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
3887 @cindex @option{-gnatD[nn]} (@command{gcc})
3890 @item /XDEBUG /LXDEBUG=nnn
3892 Create expanded source files for source level debugging. This switch
3893 also suppress generation of cross-reference information
3894 (see @option{-gnatx}).
3896 @item -gnatec=@var{path}
3897 @cindex @option{-gnatec} (@command{gcc})
3898 Specify a configuration pragma file
3900 (the equal sign is optional)
3902 (@pxref{The Configuration Pragmas Files}).
3904 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
3905 @cindex @option{-gnateD} (@command{gcc})
3906 Defines a symbol, associated with @var{value}, for preprocessing.
3907 (@pxref{Integrated Preprocessing}).
3910 @cindex @option{-gnatef} (@command{gcc})
3911 Display full source path name in brief error messages.
3914 @cindex @option{-gnateG} (@command{gcc})
3915 Save result of preprocessing in a text file.
3917 @item -gnatem=@var{path}
3918 @cindex @option{-gnatem} (@command{gcc})
3919 Specify a mapping file
3921 (the equal sign is optional)
3923 (@pxref{Units to Sources Mapping Files}).
3925 @item -gnatep=@var{file}
3926 @cindex @option{-gnatep} (@command{gcc})
3927 Specify a preprocessing data file
3929 (the equal sign is optional)
3931 (@pxref{Integrated Preprocessing}).
3934 @cindex @option{-gnatE} (@command{gcc})
3935 Full dynamic elaboration checks.
3938 @cindex @option{-gnatf} (@command{gcc})
3939 Full errors. Multiple errors per line, all undefined references, do not
3940 attempt to suppress cascaded errors.
3943 @cindex @option{-gnatF} (@command{gcc})
3944 Externals names are folded to all uppercase.
3946 @item ^-gnatg^/GNAT_INTERNAL^
3947 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
3948 Internal GNAT implementation mode. This should not be used for
3949 applications programs, it is intended only for use by the compiler
3950 and its run-time library. For documentation, see the GNAT sources.
3951 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
3952 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
3953 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
3954 so that all standard warnings and all standard style options are turned on.
3955 All warnings and style error messages are treated as errors.
3959 @cindex @option{-gnatG[nn]} (@command{gcc})
3962 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
3964 List generated expanded code in source form.
3966 @item ^-gnath^/HELP^
3967 @cindex @option{^-gnath^/HELP^} (@command{gcc})
3968 Output usage information. The output is written to @file{stdout}.
3970 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3971 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
3972 Identifier character set
3974 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3976 For details of the possible selections for @var{c},
3977 see @ref{Character Set Control}.
3979 @item ^-gnatI^/IGNORE_REP_CLAUSES^
3980 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
3981 Ignore representation clauses. When this switch is used, all
3982 representation clauses are treated as comments. This is useful
3983 when initially porting code where you want to ignore rep clause
3984 problems, and also for compiling foreign code (particularly
3988 @cindex @option{-gnatjnn} (@command{gcc})
3989 Reformat error messages to fit on nn character lines
3991 @item -gnatk=@var{n}
3992 @cindex @option{-gnatk} (@command{gcc})
3993 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
3996 @cindex @option{-gnatl} (@command{gcc})
3997 Output full source listing with embedded error messages.
4000 @cindex @option{-gnatL} (@command{gcc})
4001 Used in conjunction with -gnatG or -gnatD to intersperse original
4002 source lines (as comment lines with line numbers) in the expanded
4005 @item -gnatm=@var{n}
4006 @cindex @option{-gnatm} (@command{gcc})
4007 Limit number of detected error or warning messages to @var{n}
4008 where @var{n} is in the range 1..999999. The default setting if
4009 no switch is given is 9999. If the number of warnings reaches this
4010 limit, then a message is output and further warnings are suppressed,
4011 but the compilation is continued. If the number of error messages
4012 reaches this limit, then a message is output and the compilation
4013 is abandoned. The equal sign here is optional. A value of zero
4014 means that no limit applies.
4017 @cindex @option{-gnatn} (@command{gcc})
4018 Activate inlining for subprograms for which
4019 pragma @code{inline} is specified. This inlining is performed
4020 by the GCC back-end.
4023 @cindex @option{-gnatN} (@command{gcc})
4024 Activate front end inlining for subprograms for which
4025 pragma @code{Inline} is specified. This inlining is performed
4026 by the front end and will be visible in the
4027 @option{-gnatG} output.
4029 When using a gcc-based back end (in practice this means using any version
4030 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4031 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4032 Historically front end inlining was more extensive than the gcc back end
4033 inlining, but that is no longer the case.
4036 @cindex @option{-gnato} (@command{gcc})
4037 Enable numeric overflow checking (which is not normally enabled by
4038 default). Note that division by zero is a separate check that is not
4039 controlled by this switch (division by zero checking is on by default).
4042 @cindex @option{-gnatp} (@command{gcc})
4043 Suppress all checks. See @ref{Run-Time Checks} for details.
4046 @cindex @option{-gnatP} (@command{gcc})
4047 Enable polling. This is required on some systems (notably Windows NT) to
4048 obtain asynchronous abort and asynchronous transfer of control capability.
4049 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4053 @cindex @option{-gnatq} (@command{gcc})
4054 Don't quit. Try semantics, even if parse errors.
4057 @cindex @option{-gnatQ} (@command{gcc})
4058 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4061 @cindex @option{-gnatr} (@command{gcc})
4062 Treat pragma Restrictions as Restriction_Warnings.
4064 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4065 @cindex @option{-gnatR} (@command{gcc})
4066 Output representation information for declared types and objects.
4069 @cindex @option{-gnats} (@command{gcc})
4073 @cindex @option{-gnatS} (@command{gcc})
4074 Print package Standard.
4077 @cindex @option{-gnatt} (@command{gcc})
4078 Generate tree output file.
4080 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4081 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4082 All compiler tables start at @var{nnn} times usual starting size.
4085 @cindex @option{-gnatu} (@command{gcc})
4086 List units for this compilation.
4089 @cindex @option{-gnatU} (@command{gcc})
4090 Tag all error messages with the unique string ``error:''
4093 @cindex @option{-gnatv} (@command{gcc})
4094 Verbose mode. Full error output with source lines to @file{stdout}.
4097 @cindex @option{-gnatV} (@command{gcc})
4098 Control level of validity checking. See separate section describing
4101 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4102 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4104 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4105 the exact warnings that
4106 are enabled or disabled (@pxref{Warning Message Control}).
4108 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4109 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4110 Wide character encoding method
4112 (@var{e}=n/h/u/s/e/8).
4115 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4119 @cindex @option{-gnatx} (@command{gcc})
4120 Suppress generation of cross-reference information.
4122 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4123 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4124 Enable built-in style checks (@pxref{Style Checking}).
4126 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4127 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4128 Distribution stub generation and compilation
4130 (@var{m}=r/c for receiver/caller stubs).
4133 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4134 to be generated and compiled).
4137 @item ^-I^/SEARCH=^@var{dir}
4138 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4140 Direct GNAT to search the @var{dir} directory for source files needed by
4141 the current compilation
4142 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4144 @item ^-I-^/NOCURRENT_DIRECTORY^
4145 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4147 Except for the source file named in the command line, do not look for source
4148 files in the directory containing the source file named in the command line
4149 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4153 @cindex @option{-mbig-switch} (@command{gcc})
4154 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4155 This standard gcc switch causes the compiler to use larger offsets in its
4156 jump table representation for @code{case} statements.
4157 This may result in less efficient code, but is sometimes necessary
4158 (for example on HP-UX targets)
4159 @cindex HP-UX and @option{-mbig-switch} option
4160 in order to compile large and/or nested @code{case} statements.
4163 @cindex @option{-o} (@command{gcc})
4164 This switch is used in @command{gcc} to redirect the generated object file
4165 and its associated ALI file. Beware of this switch with GNAT, because it may
4166 cause the object file and ALI file to have different names which in turn
4167 may confuse the binder and the linker.
4171 @cindex @option{-nostdinc} (@command{gcc})
4172 Inhibit the search of the default location for the GNAT Run Time
4173 Library (RTL) source files.
4176 @cindex @option{-nostdlib} (@command{gcc})
4177 Inhibit the search of the default location for the GNAT Run Time
4178 Library (RTL) ALI files.
4182 @cindex @option{-O} (@command{gcc})
4183 @var{n} controls the optimization level.
4187 No optimization, the default setting if no @option{-O} appears
4190 Normal optimization, the default if you specify @option{-O} without
4191 an operand. A good compromise between code quality and compilation
4195 Extensive optimization, may improve execution time, possibly at the cost of
4196 substantially increased compilation time.
4199 Same as @option{-O2}, and also includes inline expansion for small subprograms
4203 Optimize space usage
4207 See also @ref{Optimization Levels}.
4212 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4213 Equivalent to @option{/OPTIMIZE=NONE}.
4214 This is the default behavior in the absence of an @option{/OPTIMIZE}
4217 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4218 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4219 Selects the level of optimization for your program. The supported
4220 keywords are as follows:
4223 Perform most optimizations, including those that
4225 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4226 without keyword options.
4229 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4232 Perform some optimizations, but omit ones that are costly.
4235 Same as @code{SOME}.
4238 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4239 automatic inlining of small subprograms within a unit
4242 Try to unroll loops. This keyword may be specified together with
4243 any keyword above other than @code{NONE}. Loop unrolling
4244 usually, but not always, improves the performance of programs.
4247 Optimize space usage
4251 See also @ref{Optimization Levels}.
4255 @item -pass-exit-codes
4256 @cindex @option{-pass-exit-codes} (@command{gcc})
4257 Catch exit codes from the compiler and use the most meaningful as
4261 @item --RTS=@var{rts-path}
4262 @cindex @option{--RTS} (@command{gcc})
4263 Specifies the default location of the runtime library. Same meaning as the
4264 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4267 @cindex @option{^-S^/ASM^} (@command{gcc})
4268 ^Used in place of @option{-c} to^Used to^
4269 cause the assembler source file to be
4270 generated, using @file{^.s^.S^} as the extension,
4271 instead of the object file.
4272 This may be useful if you need to examine the generated assembly code.
4274 @item ^-fverbose-asm^/VERBOSE_ASM^
4275 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4276 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4277 to cause the generated assembly code file to be annotated with variable
4278 names, making it significantly easier to follow.
4281 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4282 Show commands generated by the @command{gcc} driver. Normally used only for
4283 debugging purposes or if you need to be sure what version of the
4284 compiler you are executing.
4288 @cindex @option{-V} (@command{gcc})
4289 Execute @var{ver} version of the compiler. This is the @command{gcc}
4290 version, not the GNAT version.
4293 @item ^-w^/NO_BACK_END_WARNINGS^
4294 @cindex @option{-w} (@command{gcc})
4295 Turn off warnings generated by the back end of the compiler. Use of
4296 this switch also causes the default for front end warnings to be set
4297 to suppress (as though @option{-gnatws} had appeared at the start of
4303 @c Combining qualifiers does not work on VMS
4304 You may combine a sequence of GNAT switches into a single switch. For
4305 example, the combined switch
4307 @cindex Combining GNAT switches
4313 is equivalent to specifying the following sequence of switches:
4316 -gnato -gnatf -gnati3
4321 The following restrictions apply to the combination of switches
4326 The switch @option{-gnatc} if combined with other switches must come
4327 first in the string.
4330 The switch @option{-gnats} if combined with other switches must come
4331 first in the string.
4335 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4336 may not be combined with any other switches.
4340 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4341 switch), then all further characters in the switch are interpreted
4342 as style modifiers (see description of @option{-gnaty}).
4345 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4346 switch), then all further characters in the switch are interpreted
4347 as debug flags (see description of @option{-gnatd}).
4350 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4351 switch), then all further characters in the switch are interpreted
4352 as warning mode modifiers (see description of @option{-gnatw}).
4355 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4356 switch), then all further characters in the switch are interpreted
4357 as validity checking options (see description of @option{-gnatV}).
4361 @node Output and Error Message Control
4362 @subsection Output and Error Message Control
4366 The standard default format for error messages is called ``brief format''.
4367 Brief format messages are written to @file{stderr} (the standard error
4368 file) and have the following form:
4371 e.adb:3:04: Incorrect spelling of keyword "function"
4372 e.adb:4:20: ";" should be "is"
4376 The first integer after the file name is the line number in the file,
4377 and the second integer is the column number within the line.
4379 @code{GPS} can parse the error messages
4380 and point to the referenced character.
4382 The following switches provide control over the error message
4388 @cindex @option{-gnatv} (@command{gcc})
4391 The v stands for verbose.
4393 The effect of this setting is to write long-format error
4394 messages to @file{stdout} (the standard output file.
4395 The same program compiled with the
4396 @option{-gnatv} switch would generate:
4400 3. funcion X (Q : Integer)
4402 >>> Incorrect spelling of keyword "function"
4405 >>> ";" should be "is"
4410 The vertical bar indicates the location of the error, and the @samp{>>>}
4411 prefix can be used to search for error messages. When this switch is
4412 used the only source lines output are those with errors.
4415 @cindex @option{-gnatl} (@command{gcc})
4417 The @code{l} stands for list.
4419 This switch causes a full listing of
4420 the file to be generated. In the case where a body is
4421 compiled, the corresponding spec is also listed, along
4422 with any subunits. Typical output from compiling a package
4423 body @file{p.adb} might look like:
4425 @smallexample @c ada
4429 1. package body p is
4431 3. procedure a is separate;
4442 2. pragma Elaborate_Body
4466 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4467 standard output is redirected, a brief summary is written to
4468 @file{stderr} (standard error) giving the number of error messages and
4469 warning messages generated.
4471 @item -^gnatl^OUTPUT_FILE^=file
4472 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4473 This has the same effect as @option{-gnatl} except that the output is
4474 written to a file instead of to standard output. If the given name
4475 @file{fname} does not start with a period, then it is the full name
4476 of the file to be written. If @file{fname} is an extension, it is
4477 appended to the name of the file being compiled. For example, if
4478 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4479 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4482 @cindex @option{-gnatU} (@command{gcc})
4483 This switch forces all error messages to be preceded by the unique
4484 string ``error:''. This means that error messages take a few more
4485 characters in space, but allows easy searching for and identification
4489 @cindex @option{-gnatb} (@command{gcc})
4491 The @code{b} stands for brief.
4493 This switch causes GNAT to generate the
4494 brief format error messages to @file{stderr} (the standard error
4495 file) as well as the verbose
4496 format message or full listing (which as usual is written to
4497 @file{stdout} (the standard output file).
4499 @item -gnatm=@var{n}
4500 @cindex @option{-gnatm} (@command{gcc})
4502 The @code{m} stands for maximum.
4504 @var{n} is a decimal integer in the
4505 range of 1 to 999999 and limits the number of error or warning
4506 messages to be generated. For example, using
4507 @option{-gnatm2} might yield
4510 e.adb:3:04: Incorrect spelling of keyword "function"
4511 e.adb:5:35: missing ".."
4512 fatal error: maximum number of errors detected
4513 compilation abandoned
4517 The default setting if
4518 no switch is given is 9999. If the number of warnings reaches this
4519 limit, then a message is output and further warnings are suppressed,
4520 but the compilation is continued. If the number of error messages
4521 reaches this limit, then a message is output and the compilation
4522 is abandoned. A value of zero means that no limit applies.
4525 Note that the equal sign is optional, so the switches
4526 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4529 @cindex @option{-gnatf} (@command{gcc})
4530 @cindex Error messages, suppressing
4532 The @code{f} stands for full.
4534 Normally, the compiler suppresses error messages that are likely to be
4535 redundant. This switch causes all error
4536 messages to be generated. In particular, in the case of
4537 references to undefined variables. If a given variable is referenced
4538 several times, the normal format of messages is
4540 e.adb:7:07: "V" is undefined (more references follow)
4544 where the parenthetical comment warns that there are additional
4545 references to the variable @code{V}. Compiling the same program with the
4546 @option{-gnatf} switch yields
4549 e.adb:7:07: "V" is undefined
4550 e.adb:8:07: "V" is undefined
4551 e.adb:8:12: "V" is undefined
4552 e.adb:8:16: "V" is undefined
4553 e.adb:9:07: "V" is undefined
4554 e.adb:9:12: "V" is undefined
4558 The @option{-gnatf} switch also generates additional information for
4559 some error messages. Some examples are:
4563 Full details on entities not available in high integrity mode
4565 Details on possibly non-portable unchecked conversion
4567 List possible interpretations for ambiguous calls
4569 Additional details on incorrect parameters
4573 @cindex @option{-gnatjnn} (@command{gcc})
4574 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4575 with continuation lines are treated as though the continuation lines were
4576 separate messages (and so a warning with two continuation lines counts as
4577 three warnings, and is listed as three separate messages).
4579 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4580 messages are output in a different manner. A message and all its continuation
4581 lines are treated as a unit, and count as only one warning or message in the
4582 statistics totals. Furthermore, the message is reformatted so that no line
4583 is longer than nn characters.
4586 @cindex @option{-gnatq} (@command{gcc})
4588 The @code{q} stands for quit (really ``don't quit'').
4590 In normal operation mode, the compiler first parses the program and
4591 determines if there are any syntax errors. If there are, appropriate
4592 error messages are generated and compilation is immediately terminated.
4594 GNAT to continue with semantic analysis even if syntax errors have been
4595 found. This may enable the detection of more errors in a single run. On
4596 the other hand, the semantic analyzer is more likely to encounter some
4597 internal fatal error when given a syntactically invalid tree.
4600 @cindex @option{-gnatQ} (@command{gcc})
4601 In normal operation mode, the @file{ALI} file is not generated if any
4602 illegalities are detected in the program. The use of @option{-gnatQ} forces
4603 generation of the @file{ALI} file. This file is marked as being in
4604 error, so it cannot be used for binding purposes, but it does contain
4605 reasonably complete cross-reference information, and thus may be useful
4606 for use by tools (e.g., semantic browsing tools or integrated development
4607 environments) that are driven from the @file{ALI} file. This switch
4608 implies @option{-gnatq}, since the semantic phase must be run to get a
4609 meaningful ALI file.
4611 In addition, if @option{-gnatt} is also specified, then the tree file is
4612 generated even if there are illegalities. It may be useful in this case
4613 to also specify @option{-gnatq} to ensure that full semantic processing
4614 occurs. The resulting tree file can be processed by ASIS, for the purpose
4615 of providing partial information about illegal units, but if the error
4616 causes the tree to be badly malformed, then ASIS may crash during the
4619 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4620 being in error, @command{gnatmake} will attempt to recompile the source when it
4621 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4623 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4624 since ALI files are never generated if @option{-gnats} is set.
4628 @node Warning Message Control
4629 @subsection Warning Message Control
4630 @cindex Warning messages
4632 In addition to error messages, which correspond to illegalities as defined
4633 in the Ada Reference Manual, the compiler detects two kinds of warning
4636 First, the compiler considers some constructs suspicious and generates a
4637 warning message to alert you to a possible error. Second, if the
4638 compiler detects a situation that is sure to raise an exception at
4639 run time, it generates a warning message. The following shows an example
4640 of warning messages:
4642 e.adb:4:24: warning: creation of object may raise Storage_Error
4643 e.adb:10:17: warning: static value out of range
4644 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4648 GNAT considers a large number of situations as appropriate
4649 for the generation of warning messages. As always, warnings are not
4650 definite indications of errors. For example, if you do an out-of-range
4651 assignment with the deliberate intention of raising a
4652 @code{Constraint_Error} exception, then the warning that may be
4653 issued does not indicate an error. Some of the situations for which GNAT
4654 issues warnings (at least some of the time) are given in the following
4655 list. This list is not complete, and new warnings are often added to
4656 subsequent versions of GNAT. The list is intended to give a general idea
4657 of the kinds of warnings that are generated.
4661 Possible infinitely recursive calls
4664 Out-of-range values being assigned
4667 Possible order of elaboration problems
4670 Assertions (pragma Assert) that are sure to fail
4676 Address clauses with possibly unaligned values, or where an attempt is
4677 made to overlay a smaller variable with a larger one.
4680 Fixed-point type declarations with a null range
4683 Direct_IO or Sequential_IO instantiated with a type that has access values
4686 Variables that are never assigned a value
4689 Variables that are referenced before being initialized
4692 Task entries with no corresponding @code{accept} statement
4695 Duplicate accepts for the same task entry in a @code{select}
4698 Objects that take too much storage
4701 Unchecked conversion between types of differing sizes
4704 Missing @code{return} statement along some execution path in a function
4707 Incorrect (unrecognized) pragmas
4710 Incorrect external names
4713 Allocation from empty storage pool
4716 Potentially blocking operation in protected type
4719 Suspicious parenthesization of expressions
4722 Mismatching bounds in an aggregate
4725 Attempt to return local value by reference
4728 Premature instantiation of a generic body
4731 Attempt to pack aliased components
4734 Out of bounds array subscripts
4737 Wrong length on string assignment
4740 Violations of style rules if style checking is enabled
4743 Unused @code{with} clauses
4746 @code{Bit_Order} usage that does not have any effect
4749 @code{Standard.Duration} used to resolve universal fixed expression
4752 Dereference of possibly null value
4755 Declaration that is likely to cause storage error
4758 Internal GNAT unit @code{with}'ed by application unit
4761 Values known to be out of range at compile time
4764 Unreferenced labels and variables
4767 Address overlays that could clobber memory
4770 Unexpected initialization when address clause present
4773 Bad alignment for address clause
4776 Useless type conversions
4779 Redundant assignment statements and other redundant constructs
4782 Useless exception handlers
4785 Accidental hiding of name by child unit
4788 Access before elaboration detected at compile time
4791 A range in a @code{for} loop that is known to be null or might be null
4796 The following section lists compiler switches that are available
4797 to control the handling of warning messages. It is also possible
4798 to exercise much finer control over what warnings are issued and
4799 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
4800 gnat_rm, GNAT Reference manual}.
4805 @emph{Activate all optional errors.}
4806 @cindex @option{-gnatwa} (@command{gcc})
4807 This switch activates most optional warning messages, see remaining list
4808 in this section for details on optional warning messages that can be
4809 individually controlled. The warnings that are not turned on by this
4811 @option{-gnatwd} (implicit dereferencing),
4812 @option{-gnatwh} (hiding),
4813 @option{-gnatwl} (elaboration warnings),
4814 @option{-gnatw.o} (warn on values set by out parameters ignored)
4815 and @option{-gnatwt} (tracking of deleted conditional code).
4816 All other optional warnings are turned on.
4819 @emph{Suppress all optional errors.}
4820 @cindex @option{-gnatwA} (@command{gcc})
4821 This switch suppresses all optional warning messages, see remaining list
4822 in this section for details on optional warning messages that can be
4823 individually controlled.
4826 @emph{Activate warnings on failing assertions.}
4827 @cindex @option{-gnatw.a} (@command{gcc})
4828 @cindex Assert failures
4829 This switch activates warnings for assertions where the compiler can tell at
4830 compile time that the assertion will fail. Note that this warning is given
4831 even if assertions are disabled. The default is that such warnings are
4835 @emph{Suppress warnings on failing assertions.}
4836 @cindex @option{-gnatw.A} (@command{gcc})
4837 @cindex Assert failures
4838 This switch suppresses warnings for assertions where the compiler can tell at
4839 compile time that the assertion will fail.
4842 @emph{Activate warnings on bad fixed values.}
4843 @cindex @option{-gnatwb} (@command{gcc})
4844 @cindex Bad fixed values
4845 @cindex Fixed-point Small value
4847 This switch activates warnings for static fixed-point expressions whose
4848 value is not an exact multiple of Small. Such values are implementation
4849 dependent, since an implementation is free to choose either of the multiples
4850 that surround the value. GNAT always chooses the closer one, but this is not
4851 required behavior, and it is better to specify a value that is an exact
4852 multiple, ensuring predictable execution. The default is that such warnings
4856 @emph{Suppress warnings on bad fixed values.}
4857 @cindex @option{-gnatwB} (@command{gcc})
4858 This switch suppresses warnings for static fixed-point expressions whose
4859 value is not an exact multiple of Small.
4862 @emph{Activate warnings on biased representation.}
4863 @cindex @option{-gnatw.b} (@command{gcc})
4864 @cindex Biased representation
4865 This switch activates warnings when a size clause, value size clause, component
4866 clause, or component size clause forces the use of biased representation for an
4867 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
4868 to represent 10/11). The default is that such warnings are generated.
4871 @emph{Suppress warnings on biased representation.}
4872 @cindex @option{-gnatwB} (@command{gcc})
4873 This switch suppresses warnings for representation clauses that force the use
4874 of biased representation.
4877 @emph{Activate warnings on conditionals.}
4878 @cindex @option{-gnatwc} (@command{gcc})
4879 @cindex Conditionals, constant
4880 This switch activates warnings for conditional expressions used in
4881 tests that are known to be True or False at compile time. The default
4882 is that such warnings are not generated.
4883 Note that this warning does
4884 not get issued for the use of boolean variables or constants whose
4885 values are known at compile time, since this is a standard technique
4886 for conditional compilation in Ada, and this would generate too many
4887 false positive warnings.
4889 This warning option also activates a special test for comparisons using
4890 the operators ``>='' and`` <=''.
4891 If the compiler can tell that only the equality condition is possible,
4892 then it will warn that the ``>'' or ``<'' part of the test
4893 is useless and that the operator could be replaced by ``=''.
4894 An example would be comparing a @code{Natural} variable <= 0.
4896 This warning option also generates warnings if
4897 one or both tests is optimized away in a membership test for integer
4898 values if the result can be determined at compile time. Range tests on
4899 enumeration types are not included, since it is common for such tests
4900 to include an end point.
4902 This warning can also be turned on using @option{-gnatwa}.
4905 @emph{Suppress warnings on conditionals.}
4906 @cindex @option{-gnatwC} (@command{gcc})
4907 This switch suppresses warnings for conditional expressions used in
4908 tests that are known to be True or False at compile time.
4911 @emph{Activate warnings on missing component clauses.}
4912 @cindex @option{-gnatw.c} (@command{gcc})
4913 @cindex Component clause, missing
4914 This switch activates warnings for record components where a record
4915 representation clause is present and has component clauses for the
4916 majority, but not all, of the components. A warning is given for each
4917 component for which no component clause is present.
4919 This warning can also be turned on using @option{-gnatwa}.
4922 @emph{Suppress warnings on missing component clauses.}
4923 @cindex @option{-gnatwC} (@command{gcc})
4924 This switch suppresses warnings for record components that are
4925 missing a component clause in the situation described above.
4928 @emph{Activate warnings on implicit dereferencing.}
4929 @cindex @option{-gnatwd} (@command{gcc})
4930 If this switch is set, then the use of a prefix of an access type
4931 in an indexed component, slice, or selected component without an
4932 explicit @code{.all} will generate a warning. With this warning
4933 enabled, access checks occur only at points where an explicit
4934 @code{.all} appears in the source code (assuming no warnings are
4935 generated as a result of this switch). The default is that such
4936 warnings are not generated.
4937 Note that @option{-gnatwa} does not affect the setting of
4938 this warning option.
4941 @emph{Suppress warnings on implicit dereferencing.}
4942 @cindex @option{-gnatwD} (@command{gcc})
4943 @cindex Implicit dereferencing
4944 @cindex Dereferencing, implicit
4945 This switch suppresses warnings for implicit dereferences in
4946 indexed components, slices, and selected components.
4949 @emph{Treat warnings as errors.}
4950 @cindex @option{-gnatwe} (@command{gcc})
4951 @cindex Warnings, treat as error
4952 This switch causes warning messages to be treated as errors.
4953 The warning string still appears, but the warning messages are counted
4954 as errors, and prevent the generation of an object file.
4957 @emph{Activate every optional warning}
4958 @cindex @option{-gnatw.e} (@command{gcc})
4959 @cindex Warnings, activate every optional warning
4960 This switch activates all optional warnings, including those which
4961 are not activated by @code{-gnatwa}.
4964 @emph{Activate warnings on unreferenced formals.}
4965 @cindex @option{-gnatwf} (@command{gcc})
4966 @cindex Formals, unreferenced
4967 This switch causes a warning to be generated if a formal parameter
4968 is not referenced in the body of the subprogram. This warning can
4969 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
4970 default is that these warnings are not generated.
4973 @emph{Suppress warnings on unreferenced formals.}
4974 @cindex @option{-gnatwF} (@command{gcc})
4975 This switch suppresses warnings for unreferenced formal
4976 parameters. Note that the
4977 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4978 effect of warning on unreferenced entities other than subprogram
4982 @emph{Activate warnings on unrecognized pragmas.}
4983 @cindex @option{-gnatwg} (@command{gcc})
4984 @cindex Pragmas, unrecognized
4985 This switch causes a warning to be generated if an unrecognized
4986 pragma is encountered. Apart from issuing this warning, the
4987 pragma is ignored and has no effect. This warning can
4988 also be turned on using @option{-gnatwa}. The default
4989 is that such warnings are issued (satisfying the Ada Reference
4990 Manual requirement that such warnings appear).
4993 @emph{Suppress warnings on unrecognized pragmas.}
4994 @cindex @option{-gnatwG} (@command{gcc})
4995 This switch suppresses warnings for unrecognized pragmas.
4998 @emph{Activate warnings on hiding.}
4999 @cindex @option{-gnatwh} (@command{gcc})
5000 @cindex Hiding of Declarations
5001 This switch activates warnings on hiding declarations.
5002 A declaration is considered hiding
5003 if it is for a non-overloadable entity, and it declares an entity with the
5004 same name as some other entity that is directly or use-visible. The default
5005 is that such warnings are not generated.
5006 Note that @option{-gnatwa} does not affect the setting of this warning option.
5009 @emph{Suppress warnings on hiding.}
5010 @cindex @option{-gnatwH} (@command{gcc})
5011 This switch suppresses warnings on hiding declarations.
5014 @emph{Activate warnings on implementation units.}
5015 @cindex @option{-gnatwi} (@command{gcc})
5016 This switch activates warnings for a @code{with} of an internal GNAT
5017 implementation unit, defined as any unit from the @code{Ada},
5018 @code{Interfaces}, @code{GNAT},
5019 ^^@code{DEC},^ or @code{System}
5020 hierarchies that is not
5021 documented in either the Ada Reference Manual or the GNAT
5022 Programmer's Reference Manual. Such units are intended only
5023 for internal implementation purposes and should not be @code{with}'ed
5024 by user programs. The default is that such warnings are generated
5025 This warning can also be turned on using @option{-gnatwa}.
5028 @emph{Disable warnings on implementation units.}
5029 @cindex @option{-gnatwI} (@command{gcc})
5030 This switch disables warnings for a @code{with} of an internal GNAT
5031 implementation unit.
5034 @emph{Activate warnings on obsolescent features (Annex J).}
5035 @cindex @option{-gnatwj} (@command{gcc})
5036 @cindex Features, obsolescent
5037 @cindex Obsolescent features
5038 If this warning option is activated, then warnings are generated for
5039 calls to subprograms marked with @code{pragma Obsolescent} and
5040 for use of features in Annex J of the Ada Reference Manual. In the
5041 case of Annex J, not all features are flagged. In particular use
5042 of the renamed packages (like @code{Text_IO}) and use of package
5043 @code{ASCII} are not flagged, since these are very common and
5044 would generate many annoying positive warnings. The default is that
5045 such warnings are not generated. This warning is also turned on by
5046 the use of @option{-gnatwa}.
5048 In addition to the above cases, warnings are also generated for
5049 GNAT features that have been provided in past versions but which
5050 have been superseded (typically by features in the new Ada standard).
5051 For example, @code{pragma Ravenscar} will be flagged since its
5052 function is replaced by @code{pragma Profile(Ravenscar)}.
5054 Note that this warning option functions differently from the
5055 restriction @code{No_Obsolescent_Features} in two respects.
5056 First, the restriction applies only to annex J features.
5057 Second, the restriction does flag uses of package @code{ASCII}.
5060 @emph{Suppress warnings on obsolescent features (Annex J).}
5061 @cindex @option{-gnatwJ} (@command{gcc})
5062 This switch disables warnings on use of obsolescent features.
5065 @emph{Activate warnings on variables that could be constants.}
5066 @cindex @option{-gnatwk} (@command{gcc})
5067 This switch activates warnings for variables that are initialized but
5068 never modified, and then could be declared constants. The default is that
5069 such warnings are not given.
5070 This warning can also be turned on using @option{-gnatwa}.
5073 @emph{Suppress warnings on variables that could be constants.}
5074 @cindex @option{-gnatwK} (@command{gcc})
5075 This switch disables warnings on variables that could be declared constants.
5078 @emph{Activate warnings for elaboration pragmas.}
5079 @cindex @option{-gnatwl} (@command{gcc})
5080 @cindex Elaboration, warnings
5081 This switch activates warnings on missing
5082 @code{Elaborate_All} and @code{Elaborate} pragmas.
5083 See the section in this guide on elaboration checking for details on
5084 when such pragmas should be used. In dynamic elaboration mode, this switch
5085 generations warnings about the need to add elaboration pragmas. Note however,
5086 that if you blindly follow these warnings, and add @code{Elaborate_All}
5087 warnings wherever they are recommended, you basically end up with the
5088 equivalent of the static elaboration model, which may not be what you want for
5089 legacy code for which the static model does not work.
5091 For the static model, the messages generated are labeled "info:" (for
5092 information messages). They are not warnings to add elaboration pragmas,
5093 merely informational messages showing what implicit elaboration pragmas
5094 have been added, for use in analyzing elaboration circularity problems.
5096 Warnings are also generated if you
5097 are using the static mode of elaboration, and a @code{pragma Elaborate}
5098 is encountered. The default is that such warnings
5100 This warning is not automatically turned on by the use of @option{-gnatwa}.
5103 @emph{Suppress warnings for elaboration pragmas.}
5104 @cindex @option{-gnatwL} (@command{gcc})
5105 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5106 See the section in this guide on elaboration checking for details on
5107 when such pragmas should be used.
5110 @emph{Activate warnings on modified but unreferenced variables.}
5111 @cindex @option{-gnatwm} (@command{gcc})
5112 This switch activates warnings for variables that are assigned (using
5113 an initialization value or with one or more assignment statements) but
5114 whose value is never read. The warning is suppressed for volatile
5115 variables and also for variables that are renamings of other variables
5116 or for which an address clause is given.
5117 This warning can also be turned on using @option{-gnatwa}.
5118 The default is that these warnings are not given.
5121 @emph{Disable warnings on modified but unreferenced variables.}
5122 @cindex @option{-gnatwM} (@command{gcc})
5123 This switch disables warnings for variables that are assigned or
5124 initialized, but never read.
5127 @emph{Set normal warnings mode.}
5128 @cindex @option{-gnatwn} (@command{gcc})
5129 This switch sets normal warning mode, in which enabled warnings are
5130 issued and treated as warnings rather than errors. This is the default
5131 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5132 an explicit @option{-gnatws} or
5133 @option{-gnatwe}. It also cancels the effect of the
5134 implicit @option{-gnatwe} that is activated by the
5135 use of @option{-gnatg}.
5138 @emph{Activate warnings on address clause overlays.}
5139 @cindex @option{-gnatwo} (@command{gcc})
5140 @cindex Address Clauses, warnings
5141 This switch activates warnings for possibly unintended initialization
5142 effects of defining address clauses that cause one variable to overlap
5143 another. The default is that such warnings are generated.
5144 This warning can also be turned on using @option{-gnatwa}.
5147 @emph{Suppress warnings on address clause overlays.}
5148 @cindex @option{-gnatwO} (@command{gcc})
5149 This switch suppresses warnings on possibly unintended initialization
5150 effects of defining address clauses that cause one variable to overlap
5154 @emph{Activate warnings on modified but unreferenced out parameters.}
5155 @cindex @option{-gnatw.o} (@command{gcc})
5156 This switch activates warnings for variables that are modified by using
5157 them as actuals for a call to a procedure with an out mode formal, where
5158 the resulting assigned value is never read. It is applicable in the case
5159 where there is more than one out mode formal. If there is only one out
5160 mode formal, the warning is issued by default (controlled by -gnatwu).
5161 The warning is suppressed for volatile
5162 variables and also for variables that are renamings of other variables
5163 or for which an address clause is given.
5164 The default is that these warnings are not given. Note that this warning
5165 is not included in -gnatwa, it must be activated explicitly.
5168 @emph{Disable warnings on modified but unreferenced out parameters.}
5169 @cindex @option{-gnatw.O} (@command{gcc})
5170 This switch suppresses warnings for variables that are modified by using
5171 them as actuals for a call to a procedure with an out mode formal, where
5172 the resulting assigned value is never read.
5175 @emph{Activate warnings on ineffective pragma Inlines.}
5176 @cindex @option{-gnatwp} (@command{gcc})
5177 @cindex Inlining, warnings
5178 This switch activates warnings for failure of front end inlining
5179 (activated by @option{-gnatN}) to inline a particular call. There are
5180 many reasons for not being able to inline a call, including most
5181 commonly that the call is too complex to inline. The default is
5182 that such warnings are not given.
5183 This warning can also be turned on using @option{-gnatwa}.
5184 Warnings on ineffective inlining by the gcc back-end can be activated
5185 separately, using the gcc switch -Winline.
5188 @emph{Suppress warnings on ineffective pragma Inlines.}
5189 @cindex @option{-gnatwP} (@command{gcc})
5190 This switch suppresses warnings on ineffective pragma Inlines. If the
5191 inlining mechanism cannot inline a call, it will simply ignore the
5195 @emph{Activate warnings on parameter ordering.}
5196 @cindex @option{-gnatw.p} (@command{gcc})
5197 @cindex Parameter order, warnings
5198 This switch activates warnings for cases of suspicious parameter
5199 ordering when the list of arguments are all simple identifiers that
5200 match the names of the formals, but are in a different order. The
5201 warning is suppressed if any use of named parameter notation is used,
5202 so this is the appropriate way to suppress a false positive (and
5203 serves to emphasize that the "misordering" is deliberate). The
5205 that such warnings are not given.
5206 This warning can also be turned on using @option{-gnatwa}.
5209 @emph{Suppress warnings on parameter ordering.}
5210 @cindex @option{-gnatw.P} (@command{gcc})
5211 This switch suppresses warnings on cases of suspicious parameter
5215 @emph{Activate warnings on questionable missing parentheses.}
5216 @cindex @option{-gnatwq} (@command{gcc})
5217 @cindex Parentheses, warnings
5218 This switch activates warnings for cases where parentheses are not used and
5219 the result is potential ambiguity from a readers point of view. For example
5220 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5221 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5222 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5223 follow the rule of always parenthesizing to make the association clear, and
5224 this warning switch warns if such parentheses are not present. The default
5225 is that these warnings are given.
5226 This warning can also be turned on using @option{-gnatwa}.
5229 @emph{Suppress warnings on questionable missing parentheses.}
5230 @cindex @option{-gnatwQ} (@command{gcc})
5231 This switch suppresses warnings for cases where the association is not
5232 clear and the use of parentheses is preferred.
5235 @emph{Activate warnings on redundant constructs.}
5236 @cindex @option{-gnatwr} (@command{gcc})
5237 This switch activates warnings for redundant constructs. The following
5238 is the current list of constructs regarded as redundant:
5242 Assignment of an item to itself.
5244 Type conversion that converts an expression to its own type.
5246 Use of the attribute @code{Base} where @code{typ'Base} is the same
5249 Use of pragma @code{Pack} when all components are placed by a record
5250 representation clause.
5252 Exception handler containing only a reraise statement (raise with no
5253 operand) which has no effect.
5255 Use of the operator abs on an operand that is known at compile time
5258 Comparison of boolean expressions to an explicit True value.
5261 This warning can also be turned on using @option{-gnatwa}.
5262 The default is that warnings for redundant constructs are not given.
5265 @emph{Suppress warnings on redundant constructs.}
5266 @cindex @option{-gnatwR} (@command{gcc})
5267 This switch suppresses warnings for redundant constructs.
5270 @emph{Suppress all warnings.}
5271 @cindex @option{-gnatws} (@command{gcc})
5272 This switch completely suppresses the
5273 output of all warning messages from the GNAT front end.
5274 Note that it does not suppress warnings from the @command{gcc} back end.
5275 To suppress these back end warnings as well, use the switch @option{-w}
5276 in addition to @option{-gnatws}.
5279 @emph{Activate warnings for tracking of deleted conditional code.}
5280 @cindex @option{-gnatwt} (@command{gcc})
5281 @cindex Deactivated code, warnings
5282 @cindex Deleted code, warnings
5283 This switch activates warnings for tracking of code in conditionals (IF and
5284 CASE statements) that is detected to be dead code which cannot be executed, and
5285 which is removed by the front end. This warning is off by default, and is not
5286 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5287 useful for detecting deactivated code in certified applications.
5290 @emph{Suppress warnings for tracking of deleted conditional code.}
5291 @cindex @option{-gnatwT} (@command{gcc})
5292 This switch suppresses warnings for tracking of deleted conditional code.
5295 @emph{Activate warnings on unused entities.}
5296 @cindex @option{-gnatwu} (@command{gcc})
5297 This switch activates warnings to be generated for entities that
5298 are declared but not referenced, and for units that are @code{with}'ed
5300 referenced. In the case of packages, a warning is also generated if
5301 no entities in the package are referenced. This means that if the package
5302 is referenced but the only references are in @code{use}
5303 clauses or @code{renames}
5304 declarations, a warning is still generated. A warning is also generated
5305 for a generic package that is @code{with}'ed but never instantiated.
5306 In the case where a package or subprogram body is compiled, and there
5307 is a @code{with} on the corresponding spec
5308 that is only referenced in the body,
5309 a warning is also generated, noting that the
5310 @code{with} can be moved to the body. The default is that
5311 such warnings are not generated.
5312 This switch also activates warnings on unreferenced formals
5313 (it includes the effect of @option{-gnatwf}).
5314 This warning can also be turned on using @option{-gnatwa}.
5317 @emph{Suppress warnings on unused entities.}
5318 @cindex @option{-gnatwU} (@command{gcc})
5319 This switch suppresses warnings for unused entities and packages.
5320 It also turns off warnings on unreferenced formals (and thus includes
5321 the effect of @option{-gnatwF}).
5324 @emph{Activate warnings on unassigned variables.}
5325 @cindex @option{-gnatwv} (@command{gcc})
5326 @cindex Unassigned variable warnings
5327 This switch activates warnings for access to variables which
5328 may not be properly initialized. The default is that
5329 such warnings are generated.
5330 This warning can also be turned on using @option{-gnatwa}.
5333 @emph{Suppress warnings on unassigned variables.}
5334 @cindex @option{-gnatwV} (@command{gcc})
5335 This switch suppresses warnings for access to variables which
5336 may not be properly initialized.
5337 For variables of a composite type, the warning can also be suppressed in
5338 Ada 2005 by using a default initialization with a box. For example, if
5339 Table is an array of records whose components are only partially uninitialized,
5340 then the following code:
5342 @smallexample @c ada
5343 Tab : Table := (others => <>);
5346 will suppress warnings on subsequent statements that access components
5350 @emph{Activate warnings on wrong low bound assumption.}
5351 @cindex @option{-gnatww} (@command{gcc})
5352 @cindex String indexing warnings
5353 This switch activates warnings for indexing an unconstrained string parameter
5354 with a literal or S'Length. This is a case where the code is assuming that the
5355 low bound is one, which is in general not true (for example when a slice is
5356 passed). The default is that such warnings are generated.
5357 This warning can also be turned on using @option{-gnatwa}.
5360 @emph{Suppress warnings on wrong low bound assumption.}
5361 @cindex @option{-gnatwW} (@command{gcc})
5362 This switch suppresses warnings for indexing an unconstrained string parameter
5363 with a literal or S'Length. Note that this warning can also be suppressed
5364 in a particular case by adding an
5365 assertion that the lower bound is 1,
5366 as shown in the following example.
5368 @smallexample @c ada
5369 procedure K (S : String) is
5370 pragma Assert (S'First = 1);
5375 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5376 @cindex @option{-gnatw.w} (@command{gcc})
5377 @cindex Warnings Off control
5378 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5379 where either the pragma is entirely useless (because it suppresses no
5380 warnings), or it could be replaced by @code{pragma Unreferenced} or
5381 @code{pragma Unmodified}.The default is that these warnings are not given.
5382 Note that this warning is not included in -gnatwa, it must be
5383 activated explicitly.
5386 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5387 @cindex @option{-gnatw.W} (@command{gcc})
5388 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5391 @emph{Activate warnings on Export/Import pragmas.}
5392 @cindex @option{-gnatwx} (@command{gcc})
5393 @cindex Export/Import pragma warnings
5394 This switch activates warnings on Export/Import pragmas when
5395 the compiler detects a possible conflict between the Ada and
5396 foreign language calling sequences. For example, the use of
5397 default parameters in a convention C procedure is dubious
5398 because the C compiler cannot supply the proper default, so
5399 a warning is issued. The default is that such warnings are
5401 This warning can also be turned on using @option{-gnatwa}.
5404 @emph{Suppress warnings on Export/Import pragmas.}
5405 @cindex @option{-gnatwX} (@command{gcc})
5406 This switch suppresses warnings on Export/Import pragmas.
5407 The sense of this is that you are telling the compiler that
5408 you know what you are doing in writing the pragma, and it
5409 should not complain at you.
5412 @emph{Activate warnings for No_Exception_Propagation mode.}
5413 @cindex @option{-gnatwm} (@command{gcc})
5414 This switch activates warnings for exception usage when pragma Restrictions
5415 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5416 explicit exception raises which are not covered by a local handler, and for
5417 exception handlers which do not cover a local raise. The default is that these
5418 warnings are not given.
5421 @emph{Disable warnings for No_Exception_Propagation mode.}
5422 This switch disables warnings for exception usage when pragma Restrictions
5423 (No_Exception_Propagation) is in effect.
5426 @emph{Activate warnings for Ada 2005 compatibility issues.}
5427 @cindex @option{-gnatwy} (@command{gcc})
5428 @cindex Ada 2005 compatibility issues warnings
5429 For the most part Ada 2005 is upwards compatible with Ada 95,
5430 but there are some exceptions (for example the fact that
5431 @code{interface} is now a reserved word in Ada 2005). This
5432 switch activates several warnings to help in identifying
5433 and correcting such incompatibilities. The default is that
5434 these warnings are generated. Note that at one point Ada 2005
5435 was called Ada 0Y, hence the choice of character.
5436 This warning can also be turned on using @option{-gnatwa}.
5439 @emph{Disable warnings for Ada 2005 compatibility issues.}
5440 @cindex @option{-gnatwY} (@command{gcc})
5441 @cindex Ada 2005 compatibility issues warnings
5442 This switch suppresses several warnings intended to help in identifying
5443 incompatibilities between Ada 95 and Ada 2005.
5446 @emph{Activate warnings on unchecked conversions.}
5447 @cindex @option{-gnatwz} (@command{gcc})
5448 @cindex Unchecked_Conversion warnings
5449 This switch activates warnings for unchecked conversions
5450 where the types are known at compile time to have different
5452 is that such warnings are generated. Warnings are also
5453 generated for subprogram pointers with different conventions,
5454 and, on VMS only, for data pointers with different conventions.
5455 This warning can also be turned on using @option{-gnatwa}.
5458 @emph{Suppress warnings on unchecked conversions.}
5459 @cindex @option{-gnatwZ} (@command{gcc})
5460 This switch suppresses warnings for unchecked conversions
5461 where the types are known at compile time to have different
5462 sizes or conventions.
5464 @item ^-Wunused^WARNINGS=UNUSED^
5465 @cindex @option{-Wunused}
5466 The warnings controlled by the @option{-gnatw} switch are generated by
5467 the front end of the compiler. The @option{GCC} back end can provide
5468 additional warnings and they are controlled by the @option{-W} switch.
5469 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5470 warnings for entities that are declared but not referenced.
5472 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5473 @cindex @option{-Wuninitialized}
5474 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5475 the back end warning for uninitialized variables. This switch must be
5476 used in conjunction with an optimization level greater than zero.
5478 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5479 @cindex @option{-Wall}
5480 This switch enables all the above warnings from the @option{GCC} back end.
5481 The code generator detects a number of warning situations that are missed
5482 by the @option{GNAT} front end, and this switch can be used to activate them.
5483 The use of this switch also sets the default front end warning mode to
5484 @option{-gnatwa}, that is, most front end warnings activated as well.
5486 @item ^-w^/NO_BACK_END_WARNINGS^
5488 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5489 The use of this switch also sets the default front end warning mode to
5490 @option{-gnatws}, that is, front end warnings suppressed as well.
5496 A string of warning parameters can be used in the same parameter. For example:
5503 will turn on all optional warnings except for elaboration pragma warnings,
5504 and also specify that warnings should be treated as errors.
5506 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5531 @node Debugging and Assertion Control
5532 @subsection Debugging and Assertion Control
5536 @cindex @option{-gnata} (@command{gcc})
5542 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5543 are ignored. This switch, where @samp{a} stands for assert, causes
5544 @code{Assert} and @code{Debug} pragmas to be activated.
5546 The pragmas have the form:
5550 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5551 @var{static-string-expression}@r{]})
5552 @b{pragma} Debug (@var{procedure call})
5557 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5558 If the result is @code{True}, the pragma has no effect (other than
5559 possible side effects from evaluating the expression). If the result is
5560 @code{False}, the exception @code{Assert_Failure} declared in the package
5561 @code{System.Assertions} is
5562 raised (passing @var{static-string-expression}, if present, as the
5563 message associated with the exception). If no string expression is
5564 given the default is a string giving the file name and line number
5567 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5568 @code{pragma Debug} may appear within a declaration sequence, allowing
5569 debugging procedures to be called between declarations.
5572 @item /DEBUG@r{[}=debug-level@r{]}
5574 Specifies how much debugging information is to be included in
5575 the resulting object file where 'debug-level' is one of the following:
5578 Include both debugger symbol records and traceback
5580 This is the default setting.
5582 Include both debugger symbol records and traceback in
5585 Excludes both debugger symbol records and traceback
5586 the object file. Same as /NODEBUG.
5588 Includes only debugger symbol records in the object
5589 file. Note that this doesn't include traceback information.
5594 @node Validity Checking
5595 @subsection Validity Checking
5596 @findex Validity Checking
5599 The Ada Reference Manual has specific requirements for checking
5600 for invalid values. In particular, RM 13.9.1 requires that the
5601 evaluation of invalid values (for example from unchecked conversions),
5602 not result in erroneous execution. In GNAT, the result of such an
5603 evaluation in normal default mode is to either use the value
5604 unmodified, or to raise Constraint_Error in those cases where use
5605 of the unmodified value would cause erroneous execution. The cases
5606 where unmodified values might lead to erroneous execution are case
5607 statements (where a wild jump might result from an invalid value),
5608 and subscripts on the left hand side (where memory corruption could
5609 occur as a result of an invalid value).
5611 The @option{-gnatB} switch tells the compiler to assume that all
5612 values are valid (that is, within their declared subtype range)
5613 except in the context of a use of the Valid attribute. This means
5614 the compiler can generate more efficient code, since the range
5615 of values is better known at compile time.
5617 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5620 The @code{x} argument is a string of letters that
5621 indicate validity checks that are performed or not performed in addition
5622 to the default checks described above.
5625 The options allowed for this qualifier
5626 indicate validity checks that are performed or not performed in addition
5627 to the default checks described above.
5633 @emph{All validity checks.}
5634 @cindex @option{-gnatVa} (@command{gcc})
5635 All validity checks are turned on.
5637 That is, @option{-gnatVa} is
5638 equivalent to @option{gnatVcdfimorst}.
5642 @emph{Validity checks for copies.}
5643 @cindex @option{-gnatVc} (@command{gcc})
5644 The right hand side of assignments, and the initializing values of
5645 object declarations are validity checked.
5648 @emph{Default (RM) validity checks.}
5649 @cindex @option{-gnatVd} (@command{gcc})
5650 Some validity checks are done by default following normal Ada semantics
5652 A check is done in case statements that the expression is within the range
5653 of the subtype. If it is not, Constraint_Error is raised.
5654 For assignments to array components, a check is done that the expression used
5655 as index is within the range. If it is not, Constraint_Error is raised.
5656 Both these validity checks may be turned off using switch @option{-gnatVD}.
5657 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5658 switch @option{-gnatVd} will leave the checks turned on.
5659 Switch @option{-gnatVD} should be used only if you are sure that all such
5660 expressions have valid values. If you use this switch and invalid values
5661 are present, then the program is erroneous, and wild jumps or memory
5662 overwriting may occur.
5665 @emph{Validity checks for elementary components.}
5666 @cindex @option{-gnatVe} (@command{gcc})
5667 In the absence of this switch, assignments to record or array components are
5668 not validity checked, even if validity checks for assignments generally
5669 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5670 require valid data, but assignment of individual components does. So for
5671 example, there is a difference between copying the elements of an array with a
5672 slice assignment, compared to assigning element by element in a loop. This
5673 switch allows you to turn off validity checking for components, even when they
5674 are assigned component by component.
5677 @emph{Validity checks for floating-point values.}
5678 @cindex @option{-gnatVf} (@command{gcc})
5679 In the absence of this switch, validity checking occurs only for discrete
5680 values. If @option{-gnatVf} is specified, then validity checking also applies
5681 for floating-point values, and NaNs and infinities are considered invalid,
5682 as well as out of range values for constrained types. Note that this means
5683 that standard IEEE infinity mode is not allowed. The exact contexts
5684 in which floating-point values are checked depends on the setting of other
5685 options. For example,
5686 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5687 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5688 (the order does not matter) specifies that floating-point parameters of mode
5689 @code{in} should be validity checked.
5692 @emph{Validity checks for @code{in} mode parameters}
5693 @cindex @option{-gnatVi} (@command{gcc})
5694 Arguments for parameters of mode @code{in} are validity checked in function
5695 and procedure calls at the point of call.
5698 @emph{Validity checks for @code{in out} mode parameters.}
5699 @cindex @option{-gnatVm} (@command{gcc})
5700 Arguments for parameters of mode @code{in out} are validity checked in
5701 procedure calls at the point of call. The @code{'m'} here stands for
5702 modify, since this concerns parameters that can be modified by the call.
5703 Note that there is no specific option to test @code{out} parameters,
5704 but any reference within the subprogram will be tested in the usual
5705 manner, and if an invalid value is copied back, any reference to it
5706 will be subject to validity checking.
5709 @emph{No validity checks.}
5710 @cindex @option{-gnatVn} (@command{gcc})
5711 This switch turns off all validity checking, including the default checking
5712 for case statements and left hand side subscripts. Note that the use of
5713 the switch @option{-gnatp} suppresses all run-time checks, including
5714 validity checks, and thus implies @option{-gnatVn}. When this switch
5715 is used, it cancels any other @option{-gnatV} previously issued.
5718 @emph{Validity checks for operator and attribute operands.}
5719 @cindex @option{-gnatVo} (@command{gcc})
5720 Arguments for predefined operators and attributes are validity checked.
5721 This includes all operators in package @code{Standard},
5722 the shift operators defined as intrinsic in package @code{Interfaces}
5723 and operands for attributes such as @code{Pos}. Checks are also made
5724 on individual component values for composite comparisons, and on the
5725 expressions in type conversions and qualified expressions. Checks are
5726 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
5729 @emph{Validity checks for parameters.}
5730 @cindex @option{-gnatVp} (@command{gcc})
5731 This controls the treatment of parameters within a subprogram (as opposed
5732 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5733 of parameters on a call. If either of these call options is used, then
5734 normally an assumption is made within a subprogram that the input arguments
5735 have been validity checking at the point of call, and do not need checking
5736 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5737 is not made, and parameters are not assumed to be valid, so their validity
5738 will be checked (or rechecked) within the subprogram.
5741 @emph{Validity checks for function returns.}
5742 @cindex @option{-gnatVr} (@command{gcc})
5743 The expression in @code{return} statements in functions is validity
5747 @emph{Validity checks for subscripts.}
5748 @cindex @option{-gnatVs} (@command{gcc})
5749 All subscripts expressions are checked for validity, whether they appear
5750 on the right side or left side (in default mode only left side subscripts
5751 are validity checked).
5754 @emph{Validity checks for tests.}
5755 @cindex @option{-gnatVt} (@command{gcc})
5756 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5757 statements are checked, as well as guard expressions in entry calls.
5762 The @option{-gnatV} switch may be followed by
5763 ^a string of letters^a list of options^
5764 to turn on a series of validity checking options.
5766 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5767 specifies that in addition to the default validity checking, copies and
5768 function return expressions are to be validity checked.
5769 In order to make it easier
5770 to specify the desired combination of effects,
5772 the upper case letters @code{CDFIMORST} may
5773 be used to turn off the corresponding lower case option.
5776 the prefix @code{NO} on an option turns off the corresponding validity
5779 @item @code{NOCOPIES}
5780 @item @code{NODEFAULT}
5781 @item @code{NOFLOATS}
5782 @item @code{NOIN_PARAMS}
5783 @item @code{NOMOD_PARAMS}
5784 @item @code{NOOPERANDS}
5785 @item @code{NORETURNS}
5786 @item @code{NOSUBSCRIPTS}
5787 @item @code{NOTESTS}
5791 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5792 turns on all validity checking options except for
5793 checking of @code{@b{in out}} procedure arguments.
5795 The specification of additional validity checking generates extra code (and
5796 in the case of @option{-gnatVa} the code expansion can be substantial).
5797 However, these additional checks can be very useful in detecting
5798 uninitialized variables, incorrect use of unchecked conversion, and other
5799 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5800 is useful in conjunction with the extra validity checking, since this
5801 ensures that wherever possible uninitialized variables have invalid values.
5803 See also the pragma @code{Validity_Checks} which allows modification of
5804 the validity checking mode at the program source level, and also allows for
5805 temporary disabling of validity checks.
5807 @node Style Checking
5808 @subsection Style Checking
5809 @findex Style checking
5812 The @option{-gnaty^x^(option,option,@dots{})^} switch
5813 @cindex @option{-gnaty} (@command{gcc})
5814 causes the compiler to
5815 enforce specified style rules. A limited set of style rules has been used
5816 in writing the GNAT sources themselves. This switch allows user programs
5817 to activate all or some of these checks. If the source program fails a
5818 specified style check, an appropriate warning message is given, preceded by
5819 the character sequence ``(style)''.
5821 @code{(option,option,@dots{})} is a sequence of keywords
5824 The string @var{x} is a sequence of letters or digits
5826 indicating the particular style
5827 checks to be performed. The following checks are defined:
5832 @emph{Specify indentation level.}
5833 If a digit from 1-9 appears
5834 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5835 then proper indentation is checked, with the digit indicating the
5836 indentation level required. A value of zero turns off this style check.
5837 The general style of required indentation is as specified by
5838 the examples in the Ada Reference Manual. Full line comments must be
5839 aligned with the @code{--} starting on a column that is a multiple of
5840 the alignment level, or they may be aligned the same way as the following
5841 non-blank line (this is useful when full line comments appear in the middle
5845 @emph{Check attribute casing.}
5846 Attribute names, including the case of keywords such as @code{digits}
5847 used as attributes names, must be written in mixed case, that is, the
5848 initial letter and any letter following an underscore must be uppercase.
5849 All other letters must be lowercase.
5851 @item ^A^ARRAY_INDEXES^
5852 @emph{Use of array index numbers in array attributes.}
5853 When using the array attributes First, Last, Range,
5854 or Length, the index number must be omitted for one-dimensional arrays
5855 and is required for multi-dimensional arrays.
5858 @emph{Blanks not allowed at statement end.}
5859 Trailing blanks are not allowed at the end of statements. The purpose of this
5860 rule, together with h (no horizontal tabs), is to enforce a canonical format
5861 for the use of blanks to separate source tokens.
5864 @emph{Check comments.}
5865 Comments must meet the following set of rules:
5870 The ``@code{--}'' that starts the column must either start in column one,
5871 or else at least one blank must precede this sequence.
5874 Comments that follow other tokens on a line must have at least one blank
5875 following the ``@code{--}'' at the start of the comment.
5878 Full line comments must have two blanks following the ``@code{--}'' that
5879 starts the comment, with the following exceptions.
5882 A line consisting only of the ``@code{--}'' characters, possibly preceded
5883 by blanks is permitted.
5886 A comment starting with ``@code{--x}'' where @code{x} is a special character
5888 This allows proper processing of the output generated by specialized tools
5889 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5891 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5892 special character is defined as being in one of the ASCII ranges
5893 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
5894 Note that this usage is not permitted
5895 in GNAT implementation units (i.e., when @option{-gnatg} is used).
5898 A line consisting entirely of minus signs, possibly preceded by blanks, is
5899 permitted. This allows the construction of box comments where lines of minus
5900 signs are used to form the top and bottom of the box.
5903 A comment that starts and ends with ``@code{--}'' is permitted as long as at
5904 least one blank follows the initial ``@code{--}''. Together with the preceding
5905 rule, this allows the construction of box comments, as shown in the following
5908 ---------------------------
5909 -- This is a box comment --
5910 -- with two text lines. --
5911 ---------------------------
5915 @item ^d^DOS_LINE_ENDINGS^
5916 @emph{Check no DOS line terminators present.}
5917 All lines must be terminated by a single ASCII.LF
5918 character (in particular the DOS line terminator sequence CR/LF is not
5922 @emph{Check end/exit labels.}
5923 Optional labels on @code{end} statements ending subprograms and on
5924 @code{exit} statements exiting named loops, are required to be present.
5927 @emph{No form feeds or vertical tabs.}
5928 Neither form feeds nor vertical tab characters are permitted
5932 @emph{GNAT style mode}
5933 The set of style check switches is set to match that used by the GNAT sources.
5934 This may be useful when developing code that is eventually intended to be
5935 incorporated into GNAT. For further details, see GNAT sources.
5938 @emph{No horizontal tabs.}
5939 Horizontal tab characters are not permitted in the source text.
5940 Together with the b (no blanks at end of line) check, this
5941 enforces a canonical form for the use of blanks to separate
5945 @emph{Check if-then layout.}
5946 The keyword @code{then} must appear either on the same
5947 line as corresponding @code{if}, or on a line on its own, lined
5948 up under the @code{if} with at least one non-blank line in between
5949 containing all or part of the condition to be tested.
5952 @emph{check mode IN keywords}
5953 Mode @code{in} (the default mode) is not
5954 allowed to be given explicitly. @code{in out} is fine,
5955 but not @code{in} on its own.
5958 @emph{Check keyword casing.}
5959 All keywords must be in lower case (with the exception of keywords
5960 such as @code{digits} used as attribute names to which this check
5964 @emph{Check layout.}
5965 Layout of statement and declaration constructs must follow the
5966 recommendations in the Ada Reference Manual, as indicated by the
5967 form of the syntax rules. For example an @code{else} keyword must
5968 be lined up with the corresponding @code{if} keyword.
5970 There are two respects in which the style rule enforced by this check
5971 option are more liberal than those in the Ada Reference Manual. First
5972 in the case of record declarations, it is permissible to put the
5973 @code{record} keyword on the same line as the @code{type} keyword, and
5974 then the @code{end} in @code{end record} must line up under @code{type}.
5975 This is also permitted when the type declaration is split on two lines.
5976 For example, any of the following three layouts is acceptable:
5978 @smallexample @c ada
6001 Second, in the case of a block statement, a permitted alternative
6002 is to put the block label on the same line as the @code{declare} or
6003 @code{begin} keyword, and then line the @code{end} keyword up under
6004 the block label. For example both the following are permitted:
6006 @smallexample @c ada
6024 The same alternative format is allowed for loops. For example, both of
6025 the following are permitted:
6027 @smallexample @c ada
6029 Clear : while J < 10 loop
6040 @item ^Lnnn^MAX_NESTING=nnn^
6041 @emph{Set maximum nesting level}
6042 The maximum level of nesting of constructs (including subprograms, loops,
6043 blocks, packages, and conditionals) may not exceed the given value
6044 @option{nnn}. A value of zero disconnects this style check.
6046 @item ^m^LINE_LENGTH^
6047 @emph{Check maximum line length.}
6048 The length of source lines must not exceed 79 characters, including
6049 any trailing blanks. The value of 79 allows convenient display on an
6050 80 character wide device or window, allowing for possible special
6051 treatment of 80 character lines. Note that this count is of
6052 characters in the source text. This means that a tab character counts
6053 as one character in this count but a wide character sequence counts as
6054 a single character (however many bytes are needed in the encoding).
6056 @item ^Mnnn^MAX_LENGTH=nnn^
6057 @emph{Set maximum line length.}
6058 The length of lines must not exceed the
6059 given value @option{nnn}. The maximum value that can be specified is 32767.
6061 @item ^n^STANDARD_CASING^
6062 @emph{Check casing of entities in Standard.}
6063 Any identifier from Standard must be cased
6064 to match the presentation in the Ada Reference Manual (for example,
6065 @code{Integer} and @code{ASCII.NUL}).
6068 @emph{Turn off all style checks}
6069 All style check options are turned off.
6071 @item ^o^ORDERED_SUBPROGRAMS^
6072 @emph{Check order of subprogram bodies.}
6073 All subprogram bodies in a given scope
6074 (e.g.@: a package body) must be in alphabetical order. The ordering
6075 rule uses normal Ada rules for comparing strings, ignoring casing
6076 of letters, except that if there is a trailing numeric suffix, then
6077 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6080 @item ^O^OVERRIDING_INDICATORS^
6081 @emph{Check that overriding subprograms are explicitly marked as such.}
6082 The declaration of a primitive operation of a type extension that overrides
6083 an inherited operation must carry an overriding indicator.
6086 @emph{Check pragma casing.}
6087 Pragma names must be written in mixed case, that is, the
6088 initial letter and any letter following an underscore must be uppercase.
6089 All other letters must be lowercase.
6091 @item ^r^REFERENCES^
6092 @emph{Check references.}
6093 All identifier references must be cased in the same way as the
6094 corresponding declaration. No specific casing style is imposed on
6095 identifiers. The only requirement is for consistency of references
6098 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6099 @emph{Check no statements after THEN/ELSE.}
6100 No statements are allowed
6101 on the same line as a THEN or ELSE keyword following the
6102 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6103 and a special exception allows a pragma to appear after ELSE.
6106 @emph{Check separate specs.}
6107 Separate declarations (``specs'') are required for subprograms (a
6108 body is not allowed to serve as its own declaration). The only
6109 exception is that parameterless library level procedures are
6110 not required to have a separate declaration. This exception covers
6111 the most frequent form of main program procedures.
6114 @emph{Check token spacing.}
6115 The following token spacing rules are enforced:
6120 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6123 The token @code{=>} must be surrounded by spaces.
6126 The token @code{<>} must be preceded by a space or a left parenthesis.
6129 Binary operators other than @code{**} must be surrounded by spaces.
6130 There is no restriction on the layout of the @code{**} binary operator.
6133 Colon must be surrounded by spaces.
6136 Colon-equal (assignment, initialization) must be surrounded by spaces.
6139 Comma must be the first non-blank character on the line, or be
6140 immediately preceded by a non-blank character, and must be followed
6144 If the token preceding a left parenthesis ends with a letter or digit, then
6145 a space must separate the two tokens.
6148 A right parenthesis must either be the first non-blank character on
6149 a line, or it must be preceded by a non-blank character.
6152 A semicolon must not be preceded by a space, and must not be followed by
6153 a non-blank character.
6156 A unary plus or minus may not be followed by a space.
6159 A vertical bar must be surrounded by spaces.
6162 @item ^u^UNNECESSARY_BLANK_LINES^
6163 @emph{Check unnecessary blank lines.}
6164 Unnecessary blank lines are not allowed. A blank line is considered
6165 unnecessary if it appears at the end of the file, or if more than
6166 one blank line occurs in sequence.
6168 @item ^x^XTRA_PARENS^
6169 @emph{Check extra parentheses.}
6170 Unnecessary extra level of parentheses (C-style) are not allowed
6171 around conditions in @code{if} statements, @code{while} statements and
6172 @code{exit} statements.
6174 @item ^y^ALL_BUILTIN^
6175 @emph{Set all standard style check options}
6176 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6177 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6178 @option{-gnatyS}, @option{-gnatyLnnn},
6179 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6183 @emph{Remove style check options}
6184 This causes any subsequent options in the string to act as canceling the
6185 corresponding style check option. To cancel maximum nesting level control,
6186 use @option{L} parameter witout any integer value after that, because any
6187 digit following @option{-} in the parameter string of the @option{-gnaty}
6188 option will be threated as canceling indentation check. The same is true
6189 for @option{M} parameter. @option{y} and @option{N} parameters are not
6190 allowed after @option{-}.
6193 This causes any subsequent options in the string to enable the corresponding
6194 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6200 @emph{Removing style check options}
6201 If the name of a style check is preceded by @option{NO} then the corresponding
6202 style check is turned off. For example @option{NOCOMMENTS} turns off style
6203 checking for comments.
6208 In the above rules, appearing in column one is always permitted, that is,
6209 counts as meeting either a requirement for a required preceding space,
6210 or as meeting a requirement for no preceding space.
6212 Appearing at the end of a line is also always permitted, that is, counts
6213 as meeting either a requirement for a following space, or as meeting
6214 a requirement for no following space.
6217 If any of these style rules is violated, a message is generated giving
6218 details on the violation. The initial characters of such messages are
6219 always ``@code{(style)}''. Note that these messages are treated as warning
6220 messages, so they normally do not prevent the generation of an object
6221 file. The @option{-gnatwe} switch can be used to treat warning messages,
6222 including style messages, as fatal errors.
6226 @option{-gnaty} on its own (that is not
6227 followed by any letters or digits), then the effect is equivalent
6228 to the use of @option{-gnatyy}, as described above, that is all
6229 built-in standard style check options are enabled.
6233 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6234 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6235 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6247 clears any previously set style checks.
6249 @node Run-Time Checks
6250 @subsection Run-Time Checks
6251 @cindex Division by zero
6252 @cindex Access before elaboration
6253 @cindex Checks, division by zero
6254 @cindex Checks, access before elaboration
6255 @cindex Checks, stack overflow checking
6258 By default, the following checks are suppressed: integer overflow
6259 checks, stack overflow checks, and checks for access before
6260 elaboration on subprogram calls. All other checks, including range
6261 checks and array bounds checks, are turned on by default. The
6262 following @command{gcc} switches refine this default behavior.
6267 @cindex @option{-gnatp} (@command{gcc})
6268 @cindex Suppressing checks
6269 @cindex Checks, suppressing
6271 Suppress all run-time checks as though @code{pragma Suppress (All_checks)}
6272 had been present in the source. Validity checks are also suppressed (in
6273 other words @option{-gnatp} also implies @option{-gnatVn}.
6274 Use this switch to improve the performance
6275 of the code at the expense of safety in the presence of invalid data or
6278 Note that when checks are suppressed, the compiler is allowed, but not
6279 required, to omit the checking code. If the run-time cost of the
6280 checking code is zero or near-zero, the compiler will generate it even
6281 if checks are suppressed. In particular, if the compiler can prove
6282 that a certain check will necessarily fail, it will generate code to
6283 do an unconditional ``raise'', even if checks are suppressed. The
6284 compiler warns in this case.
6286 Of course, run-time checks are omitted whenever the compiler can prove
6287 that they will not fail, whether or not checks are suppressed.
6289 Note that if you suppress a check that would have failed, program
6290 execution is erroneous, which means the behavior is totally
6291 unpredictable. The program might crash, or print wrong answers, or
6292 do anything else. It might even do exactly what you wanted it to do
6293 (and then it might start failing mysteriously next week or next
6294 year). The compiler will generate code based on the assumption that
6295 the condition being checked is true, which can result in disaster if
6296 that assumption is wrong.
6299 @cindex @option{-gnato} (@command{gcc})
6300 @cindex Overflow checks
6301 @cindex Check, overflow
6302 Enables overflow checking for integer operations.
6303 This causes GNAT to generate slower and larger executable
6304 programs by adding code to check for overflow (resulting in raising
6305 @code{Constraint_Error} as required by standard Ada
6306 semantics). These overflow checks correspond to situations in which
6307 the true value of the result of an operation may be outside the base
6308 range of the result type. The following example shows the distinction:
6310 @smallexample @c ada
6311 X1 : Integer := "Integer'Last";
6312 X2 : Integer range 1 .. 5 := "5";
6313 X3 : Integer := "Integer'Last";
6314 X4 : Integer range 1 .. 5 := "5";
6315 F : Float := "2.0E+20";
6324 Note that if explicit values are assigned at compile time, the
6325 compiler may be able to detect overflow at compile time, in which case
6326 no actual run-time checking code is required, and Constraint_Error
6327 will be raised unconditionally, with or without
6328 @option{-gnato}. That's why the assigned values in the above fragment
6329 are in quotes, the meaning is "assign a value not known to the
6330 compiler that happens to be equal to ...". The remaining discussion
6331 assumes that the compiler cannot detect the values at compile time.
6333 Here the first addition results in a value that is outside the base range
6334 of Integer, and hence requires an overflow check for detection of the
6335 constraint error. Thus the first assignment to @code{X1} raises a
6336 @code{Constraint_Error} exception only if @option{-gnato} is set.
6338 The second increment operation results in a violation of the explicit
6339 range constraint; such range checks are performed by default, and are
6340 unaffected by @option{-gnato}.
6342 The two conversions of @code{F} both result in values that are outside
6343 the base range of type @code{Integer} and thus will raise
6344 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6345 The fact that the result of the second conversion is assigned to
6346 variable @code{X4} with a restricted range is irrelevant, since the problem
6347 is in the conversion, not the assignment.
6349 Basically the rule is that in the default mode (@option{-gnato} not
6350 used), the generated code assures that all integer variables stay
6351 within their declared ranges, or within the base range if there is
6352 no declared range. This prevents any serious problems like indexes
6353 out of range for array operations.
6355 What is not checked in default mode is an overflow that results in
6356 an in-range, but incorrect value. In the above example, the assignments
6357 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6358 range of the target variable, but the result is wrong in the sense that
6359 it is too large to be represented correctly. Typically the assignment
6360 to @code{X1} will result in wrap around to the largest negative number.
6361 The conversions of @code{F} will result in some @code{Integer} value
6362 and if that integer value is out of the @code{X4} range then the
6363 subsequent assignment would generate an exception.
6365 @findex Machine_Overflows
6366 Note that the @option{-gnato} switch does not affect the code generated
6367 for any floating-point operations; it applies only to integer
6369 For floating-point, GNAT has the @code{Machine_Overflows}
6370 attribute set to @code{False} and the normal mode of operation is to
6371 generate IEEE NaN and infinite values on overflow or invalid operations
6372 (such as dividing 0.0 by 0.0).
6374 The reason that we distinguish overflow checking from other kinds of
6375 range constraint checking is that a failure of an overflow check, unlike
6376 for example the failure of a range check, can result in an incorrect
6377 value, but cannot cause random memory destruction (like an out of range
6378 subscript), or a wild jump (from an out of range case value). Overflow
6379 checking is also quite expensive in time and space, since in general it
6380 requires the use of double length arithmetic.
6382 Note again that @option{-gnato} is off by default, so overflow checking is
6383 not performed in default mode. This means that out of the box, with the
6384 default settings, GNAT does not do all the checks expected from the
6385 language description in the Ada Reference Manual. If you want all constraint
6386 checks to be performed, as described in this Manual, then you must
6387 explicitly use the -gnato switch either on the @command{gnatmake} or
6388 @command{gcc} command.
6391 @cindex @option{-gnatE} (@command{gcc})
6392 @cindex Elaboration checks
6393 @cindex Check, elaboration
6394 Enables dynamic checks for access-before-elaboration
6395 on subprogram calls and generic instantiations.
6396 Note that @option{-gnatE} is not necessary for safety, because in the
6397 default mode, GNAT ensures statically that the checks would not fail.
6398 For full details of the effect and use of this switch,
6399 @xref{Compiling Using gcc}.
6402 @cindex @option{-fstack-check} (@command{gcc})
6403 @cindex Stack Overflow Checking
6404 @cindex Checks, stack overflow checking
6405 Activates stack overflow checking. For full details of the effect and use of
6406 this switch see @ref{Stack Overflow Checking}.
6411 The setting of these switches only controls the default setting of the
6412 checks. You may modify them using either @code{Suppress} (to remove
6413 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6416 @node Using gcc for Syntax Checking
6417 @subsection Using @command{gcc} for Syntax Checking
6420 @cindex @option{-gnats} (@command{gcc})
6424 The @code{s} stands for ``syntax''.
6427 Run GNAT in syntax checking only mode. For
6428 example, the command
6431 $ gcc -c -gnats x.adb
6435 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6436 series of files in a single command
6438 , and can use wild cards to specify such a group of files.
6439 Note that you must specify the @option{-c} (compile
6440 only) flag in addition to the @option{-gnats} flag.
6443 You may use other switches in conjunction with @option{-gnats}. In
6444 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6445 format of any generated error messages.
6447 When the source file is empty or contains only empty lines and/or comments,
6448 the output is a warning:
6451 $ gcc -c -gnats -x ada toto.txt
6452 toto.txt:1:01: warning: empty file, contains no compilation units
6456 Otherwise, the output is simply the error messages, if any. No object file or
6457 ALI file is generated by a syntax-only compilation. Also, no units other
6458 than the one specified are accessed. For example, if a unit @code{X}
6459 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6460 check only mode does not access the source file containing unit
6463 @cindex Multiple units, syntax checking
6464 Normally, GNAT allows only a single unit in a source file. However, this
6465 restriction does not apply in syntax-check-only mode, and it is possible
6466 to check a file containing multiple compilation units concatenated
6467 together. This is primarily used by the @code{gnatchop} utility
6468 (@pxref{Renaming Files Using gnatchop}).
6471 @node Using gcc for Semantic Checking
6472 @subsection Using @command{gcc} for Semantic Checking
6475 @cindex @option{-gnatc} (@command{gcc})
6479 The @code{c} stands for ``check''.
6481 Causes the compiler to operate in semantic check mode,
6482 with full checking for all illegalities specified in the
6483 Ada Reference Manual, but without generation of any object code
6484 (no object file is generated).
6486 Because dependent files must be accessed, you must follow the GNAT
6487 semantic restrictions on file structuring to operate in this mode:
6491 The needed source files must be accessible
6492 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6495 Each file must contain only one compilation unit.
6498 The file name and unit name must match (@pxref{File Naming Rules}).
6501 The output consists of error messages as appropriate. No object file is
6502 generated. An @file{ALI} file is generated for use in the context of
6503 cross-reference tools, but this file is marked as not being suitable
6504 for binding (since no object file is generated).
6505 The checking corresponds exactly to the notion of
6506 legality in the Ada Reference Manual.
6508 Any unit can be compiled in semantics-checking-only mode, including
6509 units that would not normally be compiled (subunits,
6510 and specifications where a separate body is present).
6513 @node Compiling Different Versions of Ada
6514 @subsection Compiling Different Versions of Ada
6517 The switches described in this section allow you to explicitly specify
6518 the version of the Ada language that your programs are written in.
6519 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6520 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6521 indicate Ada 83 compatibility mode.
6524 @cindex Compatibility with Ada 83
6526 @item -gnat83 (Ada 83 Compatibility Mode)
6527 @cindex @option{-gnat83} (@command{gcc})
6528 @cindex ACVC, Ada 83 tests
6532 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6533 specifies that the program is to be compiled in Ada 83 mode. With
6534 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6535 semantics where this can be done easily.
6536 It is not possible to guarantee this switch does a perfect
6537 job; some subtle tests, such as are
6538 found in earlier ACVC tests (and that have been removed from the ACATS suite
6539 for Ada 95), might not compile correctly.
6540 Nevertheless, this switch may be useful in some circumstances, for example
6541 where, due to contractual reasons, existing code needs to be maintained
6542 using only Ada 83 features.
6544 With few exceptions (most notably the need to use @code{<>} on
6545 @cindex Generic formal parameters
6546 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6547 reserved words, and the use of packages
6548 with optional bodies), it is not necessary to specify the
6549 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6550 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6551 a correct Ada 83 program is usually also a correct program
6552 in these later versions of the language standard.
6553 For further information, please refer to @ref{Compatibility and Porting Guide}.
6555 @item -gnat95 (Ada 95 mode)
6556 @cindex @option{-gnat95} (@command{gcc})
6560 This switch directs the compiler to implement the Ada 95 version of the
6562 Since Ada 95 is almost completely upwards
6563 compatible with Ada 83, Ada 83 programs may generally be compiled using
6564 this switch (see the description of the @option{-gnat83} switch for further
6565 information about Ada 83 mode).
6566 If an Ada 2005 program is compiled in Ada 95 mode,
6567 uses of the new Ada 2005 features will cause error
6568 messages or warnings.
6570 This switch also can be used to cancel the effect of a previous
6571 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6573 @item -gnat05 (Ada 2005 mode)
6574 @cindex @option{-gnat05} (@command{gcc})
6575 @cindex Ada 2005 mode
6578 This switch directs the compiler to implement the Ada 2005 version of the
6580 Since Ada 2005 is almost completely upwards
6581 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6582 may generally be compiled using this switch (see the description of the
6583 @option{-gnat83} and @option{-gnat95} switches for further
6586 For information about the approved ``Ada Issues'' that have been incorporated
6587 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6588 Included with GNAT releases is a file @file{features-ada0y} that describes
6589 the set of implemented Ada 2005 features.
6593 @node Character Set Control
6594 @subsection Character Set Control
6596 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6597 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6600 Normally GNAT recognizes the Latin-1 character set in source program
6601 identifiers, as described in the Ada Reference Manual.
6603 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6604 single character ^^or word^ indicating the character set, as follows:
6608 ISO 8859-1 (Latin-1) identifiers
6611 ISO 8859-2 (Latin-2) letters allowed in identifiers
6614 ISO 8859-3 (Latin-3) letters allowed in identifiers
6617 ISO 8859-4 (Latin-4) letters allowed in identifiers
6620 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6623 ISO 8859-15 (Latin-9) letters allowed in identifiers
6626 IBM PC letters (code page 437) allowed in identifiers
6629 IBM PC letters (code page 850) allowed in identifiers
6631 @item ^f^FULL_UPPER^
6632 Full upper-half codes allowed in identifiers
6635 No upper-half codes allowed in identifiers
6638 Wide-character codes (that is, codes greater than 255)
6639 allowed in identifiers
6642 @xref{Foreign Language Representation}, for full details on the
6643 implementation of these character sets.
6645 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6646 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6647 Specify the method of encoding for wide characters.
6648 @var{e} is one of the following:
6653 Hex encoding (brackets coding also recognized)
6656 Upper half encoding (brackets encoding also recognized)
6659 Shift/JIS encoding (brackets encoding also recognized)
6662 EUC encoding (brackets encoding also recognized)
6665 UTF-8 encoding (brackets encoding also recognized)
6668 Brackets encoding only (default value)
6670 For full details on these encoding
6671 methods see @ref{Wide Character Encodings}.
6672 Note that brackets coding is always accepted, even if one of the other
6673 options is specified, so for example @option{-gnatW8} specifies that both
6674 brackets and UTF-8 encodings will be recognized. The units that are
6675 with'ed directly or indirectly will be scanned using the specified
6676 representation scheme, and so if one of the non-brackets scheme is
6677 used, it must be used consistently throughout the program. However,
6678 since brackets encoding is always recognized, it may be conveniently
6679 used in standard libraries, allowing these libraries to be used with
6680 any of the available coding schemes.
6683 If no @option{-gnatW?} parameter is present, then the default
6684 representation is normally Brackets encoding only. However, if the
6685 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6686 byte order mark or BOM for UTF-8), then these three characters are
6687 skipped and the default representation for the file is set to UTF-8.
6689 Note that the wide character representation that is specified (explicitly
6690 or by default) for the main program also acts as the default encoding used
6691 for Wide_Text_IO files if not specifically overridden by a WCEM form
6695 @node File Naming Control
6696 @subsection File Naming Control
6699 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6700 @cindex @option{-gnatk} (@command{gcc})
6701 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6702 1-999, indicates the maximum allowable length of a file name (not
6703 including the @file{.ads} or @file{.adb} extension). The default is not
6704 to enable file name krunching.
6706 For the source file naming rules, @xref{File Naming Rules}.
6709 @node Subprogram Inlining Control
6710 @subsection Subprogram Inlining Control
6715 @cindex @option{-gnatn} (@command{gcc})
6717 The @code{n} here is intended to suggest the first syllable of the
6720 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6721 inlining to actually occur, optimization must be enabled. To enable
6722 inlining of subprograms specified by pragma @code{Inline},
6723 you must also specify this switch.
6724 In the absence of this switch, GNAT does not attempt
6725 inlining and does not need to access the bodies of
6726 subprograms for which @code{pragma Inline} is specified if they are not
6727 in the current unit.
6729 If you specify this switch the compiler will access these bodies,
6730 creating an extra source dependency for the resulting object file, and
6731 where possible, the call will be inlined.
6732 For further details on when inlining is possible
6733 see @ref{Inlining of Subprograms}.
6736 @cindex @option{-gnatN} (@command{gcc})
6737 This switch activates front-end inlining which also
6738 generates additional dependencies.
6740 When using a gcc-based back end (in practice this means using any version
6741 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
6742 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
6743 Historically front end inlining was more extensive than the gcc back end
6744 inlining, but that is no longer the case.
6747 @node Auxiliary Output Control
6748 @subsection Auxiliary Output Control
6752 @cindex @option{-gnatt} (@command{gcc})
6753 @cindex Writing internal trees
6754 @cindex Internal trees, writing to file
6755 Causes GNAT to write the internal tree for a unit to a file (with the
6756 extension @file{.adt}.
6757 This not normally required, but is used by separate analysis tools.
6759 these tools do the necessary compilations automatically, so you should
6760 not have to specify this switch in normal operation.
6763 @cindex @option{-gnatu} (@command{gcc})
6764 Print a list of units required by this compilation on @file{stdout}.
6765 The listing includes all units on which the unit being compiled depends
6766 either directly or indirectly.
6769 @item -pass-exit-codes
6770 @cindex @option{-pass-exit-codes} (@command{gcc})
6771 If this switch is not used, the exit code returned by @command{gcc} when
6772 compiling multiple files indicates whether all source files have
6773 been successfully used to generate object files or not.
6775 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
6776 exit status and allows an integrated development environment to better
6777 react to a compilation failure. Those exit status are:
6781 There was an error in at least one source file.
6783 At least one source file did not generate an object file.
6785 The compiler died unexpectedly (internal error for example).
6787 An object file has been generated for every source file.
6792 @node Debugging Control
6793 @subsection Debugging Control
6797 @cindex Debugging options
6800 @cindex @option{-gnatd} (@command{gcc})
6801 Activate internal debugging switches. @var{x} is a letter or digit, or
6802 string of letters or digits, which specifies the type of debugging
6803 outputs desired. Normally these are used only for internal development
6804 or system debugging purposes. You can find full documentation for these
6805 switches in the body of the @code{Debug} unit in the compiler source
6806 file @file{debug.adb}.
6810 @cindex @option{-gnatG} (@command{gcc})
6811 This switch causes the compiler to generate auxiliary output containing
6812 a pseudo-source listing of the generated expanded code. Like most Ada
6813 compilers, GNAT works by first transforming the high level Ada code into
6814 lower level constructs. For example, tasking operations are transformed
6815 into calls to the tasking run-time routines. A unique capability of GNAT
6816 is to list this expanded code in a form very close to normal Ada source.
6817 This is very useful in understanding the implications of various Ada
6818 usage on the efficiency of the generated code. There are many cases in
6819 Ada (e.g.@: the use of controlled types), where simple Ada statements can
6820 generate a lot of run-time code. By using @option{-gnatG} you can identify
6821 these cases, and consider whether it may be desirable to modify the coding
6822 approach to improve efficiency.
6824 The optional parameter @code{nn} if present after -gnatG specifies an
6825 alternative maximum line length that overrides the normal default of 72.
6826 This value is in the range 40-999999, values less than 40 being silently
6827 reset to 40. The equal sign is optional.
6829 The format of the output is very similar to standard Ada source, and is
6830 easily understood by an Ada programmer. The following special syntactic
6831 additions correspond to low level features used in the generated code that
6832 do not have any exact analogies in pure Ada source form. The following
6833 is a partial list of these special constructions. See the spec
6834 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6836 If the switch @option{-gnatL} is used in conjunction with
6837 @cindex @option{-gnatL} (@command{gcc})
6838 @option{-gnatG}, then the original source lines are interspersed
6839 in the expanded source (as comment lines with the original line number).
6842 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
6843 Shows the storage pool being used for an allocator.
6845 @item at end @var{procedure-name};
6846 Shows the finalization (cleanup) procedure for a scope.
6848 @item (if @var{expr} then @var{expr} else @var{expr})
6849 Conditional expression equivalent to the @code{x?y:z} construction in C.
6851 @item @var{target}^^^(@var{source})
6852 A conversion with floating-point truncation instead of rounding.
6854 @item @var{target}?(@var{source})
6855 A conversion that bypasses normal Ada semantic checking. In particular
6856 enumeration types and fixed-point types are treated simply as integers.
6858 @item @var{target}?^^^(@var{source})
6859 Combines the above two cases.
6861 @item @var{x} #/ @var{y}
6862 @itemx @var{x} #mod @var{y}
6863 @itemx @var{x} #* @var{y}
6864 @itemx @var{x} #rem @var{y}
6865 A division or multiplication of fixed-point values which are treated as
6866 integers without any kind of scaling.
6868 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
6869 Shows the storage pool associated with a @code{free} statement.
6871 @item [subtype or type declaration]
6872 Used to list an equivalent declaration for an internally generated
6873 type that is referenced elsewhere in the listing.
6875 @item freeze @var{type-name} @ovar{actions}
6876 Shows the point at which @var{type-name} is frozen, with possible
6877 associated actions to be performed at the freeze point.
6879 @item reference @var{itype}
6880 Reference (and hence definition) to internal type @var{itype}.
6882 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6883 Intrinsic function call.
6885 @item @var{label-name} : label
6886 Declaration of label @var{labelname}.
6888 @item #$ @var{subprogram-name}
6889 An implicit call to a run-time support routine
6890 (to meet the requirement of H.3.1(9) in a
6893 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
6894 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6895 @var{expr}, but handled more efficiently).
6897 @item [constraint_error]
6898 Raise the @code{Constraint_Error} exception.
6900 @item @var{expression}'reference
6901 A pointer to the result of evaluating @var{expression}.
6903 @item @var{target-type}!(@var{source-expression})
6904 An unchecked conversion of @var{source-expression} to @var{target-type}.
6906 @item [@var{numerator}/@var{denominator}]
6907 Used to represent internal real literals (that) have no exact
6908 representation in base 2-16 (for example, the result of compile time
6909 evaluation of the expression 1.0/27.0).
6913 @cindex @option{-gnatD} (@command{gcc})
6914 When used in conjunction with @option{-gnatG}, this switch causes
6915 the expanded source, as described above for
6916 @option{-gnatG} to be written to files with names
6917 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6918 instead of to the standard output file. For
6919 example, if the source file name is @file{hello.adb}, then a file
6920 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6921 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
6922 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6923 you to do source level debugging using the generated code which is
6924 sometimes useful for complex code, for example to find out exactly
6925 which part of a complex construction raised an exception. This switch
6926 also suppress generation of cross-reference information (see
6927 @option{-gnatx}) since otherwise the cross-reference information
6928 would refer to the @file{^.dg^.DG^} file, which would cause
6929 confusion since this is not the original source file.
6931 Note that @option{-gnatD} actually implies @option{-gnatG}
6932 automatically, so it is not necessary to give both options.
6933 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6935 If the switch @option{-gnatL} is used in conjunction with
6936 @cindex @option{-gnatL} (@command{gcc})
6937 @option{-gnatDG}, then the original source lines are interspersed
6938 in the expanded source (as comment lines with the original line number).
6940 The optional parameter @code{nn} if present after -gnatD specifies an
6941 alternative maximum line length that overrides the normal default of 72.
6942 This value is in the range 40-999999, values less than 40 being silently
6943 reset to 40. The equal sign is optional.
6946 @cindex @option{-gnatr} (@command{gcc})
6947 @cindex pragma Restrictions
6948 This switch causes pragma Restrictions to be treated as Restriction_Warnings
6949 so that violation of restrictions causes warnings rather than illegalities.
6950 This is useful during the development process when new restrictions are added
6951 or investigated. The switch also causes pragma Profile to be treated as
6952 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
6953 restriction warnings rather than restrictions.
6956 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
6957 @cindex @option{-gnatR} (@command{gcc})
6958 This switch controls output from the compiler of a listing showing
6959 representation information for declared types and objects. For
6960 @option{-gnatR0}, no information is output (equivalent to omitting
6961 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6962 so @option{-gnatR} with no parameter has the same effect), size and alignment
6963 information is listed for declared array and record types. For
6964 @option{-gnatR2}, size and alignment information is listed for all
6965 declared types and objects. Finally @option{-gnatR3} includes symbolic
6966 expressions for values that are computed at run time for
6967 variant records. These symbolic expressions have a mostly obvious
6968 format with #n being used to represent the value of the n'th
6969 discriminant. See source files @file{repinfo.ads/adb} in the
6970 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6971 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
6972 the output is to a file with the name @file{^file.rep^file_REP^} where
6973 file is the name of the corresponding source file.
6976 @item /REPRESENTATION_INFO
6977 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
6978 This qualifier controls output from the compiler of a listing showing
6979 representation information for declared types and objects. For
6980 @option{/REPRESENTATION_INFO=NONE}, no information is output
6981 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6982 @option{/REPRESENTATION_INFO} without option is equivalent to
6983 @option{/REPRESENTATION_INFO=ARRAYS}.
6984 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6985 information is listed for declared array and record types. For
6986 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6987 is listed for all expression information for values that are computed
6988 at run time for variant records. These symbolic expressions have a mostly
6989 obvious format with #n being used to represent the value of the n'th
6990 discriminant. See source files @file{REPINFO.ADS/ADB} in the
6991 @code{GNAT} sources for full details on the format of
6992 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
6993 If _FILE is added at the end of an option
6994 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
6995 then the output is to a file with the name @file{file_REP} where
6996 file is the name of the corresponding source file.
6998 Note that it is possible for record components to have zero size. In
6999 this case, the component clause uses an obvious extension of permitted
7000 Ada syntax, for example @code{at 0 range 0 .. -1}.
7002 Representation information requires that code be generated (since it is the
7003 code generator that lays out complex data structures). If an attempt is made
7004 to output representation information when no code is generated, for example
7005 when a subunit is compiled on its own, then no information can be generated
7006 and the compiler outputs a message to this effect.
7009 @cindex @option{-gnatS} (@command{gcc})
7010 The use of the switch @option{-gnatS} for an
7011 Ada compilation will cause the compiler to output a
7012 representation of package Standard in a form very
7013 close to standard Ada. It is not quite possible to
7014 do this entirely in standard Ada (since new
7015 numeric base types cannot be created in standard
7016 Ada), but the output is easily
7017 readable to any Ada programmer, and is useful to
7018 determine the characteristics of target dependent
7019 types in package Standard.
7022 @cindex @option{-gnatx} (@command{gcc})
7023 Normally the compiler generates full cross-referencing information in
7024 the @file{ALI} file. This information is used by a number of tools,
7025 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7026 suppresses this information. This saves some space and may slightly
7027 speed up compilation, but means that these tools cannot be used.
7030 @node Exception Handling Control
7031 @subsection Exception Handling Control
7034 GNAT uses two methods for handling exceptions at run-time. The
7035 @code{setjmp/longjmp} method saves the context when entering
7036 a frame with an exception handler. Then when an exception is
7037 raised, the context can be restored immediately, without the
7038 need for tracing stack frames. This method provides very fast
7039 exception propagation, but introduces significant overhead for
7040 the use of exception handlers, even if no exception is raised.
7042 The other approach is called ``zero cost'' exception handling.
7043 With this method, the compiler builds static tables to describe
7044 the exception ranges. No dynamic code is required when entering
7045 a frame containing an exception handler. When an exception is
7046 raised, the tables are used to control a back trace of the
7047 subprogram invocation stack to locate the required exception
7048 handler. This method has considerably poorer performance for
7049 the propagation of exceptions, but there is no overhead for
7050 exception handlers if no exception is raised. Note that in this
7051 mode and in the context of mixed Ada and C/C++ programming,
7052 to propagate an exception through a C/C++ code, the C/C++ code
7053 must be compiled with the @option{-funwind-tables} GCC's
7056 The following switches may be used to control which of the
7057 two exception handling methods is used.
7063 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7064 This switch causes the setjmp/longjmp run-time (when available) to be used
7065 for exception handling. If the default
7066 mechanism for the target is zero cost exceptions, then
7067 this switch can be used to modify this default, and must be
7068 used for all units in the partition.
7069 This option is rarely used. One case in which it may be
7070 advantageous is if you have an application where exception
7071 raising is common and the overall performance of the
7072 application is improved by favoring exception propagation.
7075 @cindex @option{--RTS=zcx} (@command{gnatmake})
7076 @cindex Zero Cost Exceptions
7077 This switch causes the zero cost approach to be used
7078 for exception handling. If this is the default mechanism for the
7079 target (see below), then this switch is unneeded. If the default
7080 mechanism for the target is setjmp/longjmp exceptions, then
7081 this switch can be used to modify this default, and must be
7082 used for all units in the partition.
7083 This option can only be used if the zero cost approach
7084 is available for the target in use, otherwise it will generate an error.
7088 The same option @option{--RTS} must be used both for @command{gcc}
7089 and @command{gnatbind}. Passing this option to @command{gnatmake}
7090 (@pxref{Switches for gnatmake}) will ensure the required consistency
7091 through the compilation and binding steps.
7093 @node Units to Sources Mapping Files
7094 @subsection Units to Sources Mapping Files
7098 @item -gnatem^^=^@var{path}
7099 @cindex @option{-gnatem} (@command{gcc})
7100 A mapping file is a way to communicate to the compiler two mappings:
7101 from unit names to file names (without any directory information) and from
7102 file names to path names (with full directory information). These mappings
7103 are used by the compiler to short-circuit the path search.
7105 The use of mapping files is not required for correct operation of the
7106 compiler, but mapping files can improve efficiency, particularly when
7107 sources are read over a slow network connection. In normal operation,
7108 you need not be concerned with the format or use of mapping files,
7109 and the @option{-gnatem} switch is not a switch that you would use
7110 explicitly. it is intended only for use by automatic tools such as
7111 @command{gnatmake} running under the project file facility. The
7112 description here of the format of mapping files is provided
7113 for completeness and for possible use by other tools.
7115 A mapping file is a sequence of sets of three lines. In each set,
7116 the first line is the unit name, in lower case, with ``@code{%s}''
7118 specs and ``@code{%b}'' appended for bodies; the second line is the
7119 file name; and the third line is the path name.
7125 /gnat/project1/sources/main.2.ada
7128 When the switch @option{-gnatem} is specified, the compiler will create
7129 in memory the two mappings from the specified file. If there is any problem
7130 (nonexistent file, truncated file or duplicate entries), no mapping will
7133 Several @option{-gnatem} switches may be specified; however, only the last
7134 one on the command line will be taken into account.
7136 When using a project file, @command{gnatmake} create a temporary mapping file
7137 and communicates it to the compiler using this switch.
7141 @node Integrated Preprocessing
7142 @subsection Integrated Preprocessing
7145 GNAT sources may be preprocessed immediately before compilation.
7146 In this case, the actual
7147 text of the source is not the text of the source file, but is derived from it
7148 through a process called preprocessing. Integrated preprocessing is specified
7149 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7150 indicates, through a text file, the preprocessing data to be used.
7151 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7154 Note that when integrated preprocessing is used, the output from the
7155 preprocessor is not written to any external file. Instead it is passed
7156 internally to the compiler. If you need to preserve the result of
7157 preprocessing in a file, then you should use @command{gnatprep}
7158 to perform the desired preprocessing in stand-alone mode.
7161 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7162 used when Integrated Preprocessing is used. The reason is that preprocessing
7163 with another Preprocessing Data file without changing the sources will
7164 not trigger recompilation without this switch.
7167 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7168 always trigger recompilation for sources that are preprocessed,
7169 because @command{gnatmake} cannot compute the checksum of the source after
7173 The actual preprocessing function is described in details in section
7174 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7175 preprocessing is triggered and parameterized.
7179 @item -gnatep=@var{file}
7180 @cindex @option{-gnatep} (@command{gcc})
7181 This switch indicates to the compiler the file name (without directory
7182 information) of the preprocessor data file to use. The preprocessor data file
7183 should be found in the source directories.
7186 A preprocessing data file is a text file with significant lines indicating
7187 how should be preprocessed either a specific source or all sources not
7188 mentioned in other lines. A significant line is a nonempty, non-comment line.
7189 Comments are similar to Ada comments.
7192 Each significant line starts with either a literal string or the character '*'.
7193 A literal string is the file name (without directory information) of the source
7194 to preprocess. A character '*' indicates the preprocessing for all the sources
7195 that are not specified explicitly on other lines (order of the lines is not
7196 significant). It is an error to have two lines with the same file name or two
7197 lines starting with the character '*'.
7200 After the file name or the character '*', another optional literal string
7201 indicating the file name of the definition file to be used for preprocessing
7202 (@pxref{Form of Definitions File}). The definition files are found by the
7203 compiler in one of the source directories. In some cases, when compiling
7204 a source in a directory other than the current directory, if the definition
7205 file is in the current directory, it may be necessary to add the current
7206 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7207 the compiler would not find the definition file.
7210 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7211 be found. Those ^switches^switches^ are:
7216 Causes both preprocessor lines and the lines deleted by
7217 preprocessing to be replaced by blank lines, preserving the line number.
7218 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7219 it cancels the effect of @option{-c}.
7222 Causes both preprocessor lines and the lines deleted
7223 by preprocessing to be retained as comments marked
7224 with the special string ``@code{--! }''.
7226 @item -Dsymbol=value
7227 Define or redefine a symbol, associated with value. A symbol is an Ada
7228 identifier, or an Ada reserved word, with the exception of @code{if},
7229 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7230 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7231 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7232 same name defined in a definition file.
7235 Causes a sorted list of symbol names and values to be
7236 listed on the standard output file.
7239 Causes undefined symbols to be treated as having the value @code{FALSE}
7241 of a preprocessor test. In the absence of this option, an undefined symbol in
7242 a @code{#if} or @code{#elsif} test will be treated as an error.
7247 Examples of valid lines in a preprocessor data file:
7250 "toto.adb" "prep.def" -u
7251 -- preprocess "toto.adb", using definition file "prep.def",
7252 -- undefined symbol are False.
7255 -- preprocess all other sources without a definition file;
7256 -- suppressed lined are commented; symbol VERSION has the value V101.
7258 "titi.adb" "prep2.def" -s
7259 -- preprocess "titi.adb", using definition file "prep2.def";
7260 -- list all symbols with their values.
7263 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7264 @cindex @option{-gnateD} (@command{gcc})
7265 Define or redefine a preprocessing symbol, associated with value. If no value
7266 is given on the command line, then the value of the symbol is @code{True}.
7267 A symbol is an identifier, following normal Ada (case-insensitive)
7268 rules for its syntax, and value is any sequence (including an empty sequence)
7269 of characters from the set (letters, digits, period, underline).
7270 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7271 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7274 A symbol declared with this ^switch^switch^ on the command line replaces a
7275 symbol with the same name either in a definition file or specified with a
7276 ^switch^switch^ -D in the preprocessor data file.
7279 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7282 When integrated preprocessing is performed and the preprocessor modifies
7283 the source text, write the result of this preprocessing into a file
7284 <source>^.prep^_prep^.
7288 @node Code Generation Control
7289 @subsection Code Generation Control
7293 The GCC technology provides a wide range of target dependent
7294 @option{-m} switches for controlling
7295 details of code generation with respect to different versions of
7296 architectures. This includes variations in instruction sets (e.g.@:
7297 different members of the power pc family), and different requirements
7298 for optimal arrangement of instructions (e.g.@: different members of
7299 the x86 family). The list of available @option{-m} switches may be
7300 found in the GCC documentation.
7302 Use of these @option{-m} switches may in some cases result in improved
7305 The GNAT Pro technology is tested and qualified without any
7306 @option{-m} switches,
7307 so generally the most reliable approach is to avoid the use of these
7308 switches. However, we generally expect most of these switches to work
7309 successfully with GNAT Pro, and many customers have reported successful
7310 use of these options.
7312 Our general advice is to avoid the use of @option{-m} switches unless
7313 special needs lead to requirements in this area. In particular,
7314 there is no point in using @option{-m} switches to improve performance
7315 unless you actually see a performance improvement.
7319 @subsection Return Codes
7320 @cindex Return Codes
7321 @cindex @option{/RETURN_CODES=VMS}
7324 On VMS, GNAT compiled programs return POSIX-style codes by default,
7325 e.g.@: @option{/RETURN_CODES=POSIX}.
7327 To enable VMS style return codes, use GNAT BIND and LINK with the option
7328 @option{/RETURN_CODES=VMS}. For example:
7331 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7332 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7336 Programs built with /RETURN_CODES=VMS are suitable to be called in
7337 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7338 are suitable for spawning with appropriate GNAT RTL routines.
7342 @node Search Paths and the Run-Time Library (RTL)
7343 @section Search Paths and the Run-Time Library (RTL)
7346 With the GNAT source-based library system, the compiler must be able to
7347 find source files for units that are needed by the unit being compiled.
7348 Search paths are used to guide this process.
7350 The compiler compiles one source file whose name must be given
7351 explicitly on the command line. In other words, no searching is done
7352 for this file. To find all other source files that are needed (the most
7353 common being the specs of units), the compiler examines the following
7354 directories, in the following order:
7358 The directory containing the source file of the main unit being compiled
7359 (the file name on the command line).
7362 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7363 @command{gcc} command line, in the order given.
7366 @findex ADA_PRJ_INCLUDE_FILE
7367 Each of the directories listed in the text file whose name is given
7368 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7371 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7372 driver when project files are used. It should not normally be set
7376 @findex ADA_INCLUDE_PATH
7377 Each of the directories listed in the value of the
7378 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7380 Construct this value
7381 exactly as the @env{PATH} environment variable: a list of directory
7382 names separated by colons (semicolons when working with the NT version).
7385 Normally, define this value as a logical name containing a comma separated
7386 list of directory names.
7388 This variable can also be defined by means of an environment string
7389 (an argument to the HP C exec* set of functions).
7393 DEFINE ANOTHER_PATH FOO:[BAG]
7394 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7397 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7398 first, followed by the standard Ada
7399 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7400 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7401 (Text_IO, Sequential_IO, etc)
7402 instead of the standard Ada packages. Thus, in order to get the standard Ada
7403 packages by default, ADA_INCLUDE_PATH must be redefined.
7407 The content of the @file{ada_source_path} file which is part of the GNAT
7408 installation tree and is used to store standard libraries such as the
7409 GNAT Run Time Library (RTL) source files.
7411 @ref{Installing a library}
7416 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7417 inhibits the use of the directory
7418 containing the source file named in the command line. You can still
7419 have this directory on your search path, but in this case it must be
7420 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7422 Specifying the switch @option{-nostdinc}
7423 inhibits the search of the default location for the GNAT Run Time
7424 Library (RTL) source files.
7426 The compiler outputs its object files and ALI files in the current
7429 Caution: The object file can be redirected with the @option{-o} switch;
7430 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7431 so the @file{ALI} file will not go to the right place. Therefore, you should
7432 avoid using the @option{-o} switch.
7436 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7437 children make up the GNAT RTL, together with the simple @code{System.IO}
7438 package used in the @code{"Hello World"} example. The sources for these units
7439 are needed by the compiler and are kept together in one directory. Not
7440 all of the bodies are needed, but all of the sources are kept together
7441 anyway. In a normal installation, you need not specify these directory
7442 names when compiling or binding. Either the environment variables or
7443 the built-in defaults cause these files to be found.
7445 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7446 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7447 consisting of child units of @code{GNAT}. This is a collection of generally
7448 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7449 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7451 Besides simplifying access to the RTL, a major use of search paths is
7452 in compiling sources from multiple directories. This can make
7453 development environments much more flexible.
7455 @node Order of Compilation Issues
7456 @section Order of Compilation Issues
7459 If, in our earlier example, there was a spec for the @code{hello}
7460 procedure, it would be contained in the file @file{hello.ads}; yet this
7461 file would not have to be explicitly compiled. This is the result of the
7462 model we chose to implement library management. Some of the consequences
7463 of this model are as follows:
7467 There is no point in compiling specs (except for package
7468 specs with no bodies) because these are compiled as needed by clients. If
7469 you attempt a useless compilation, you will receive an error message.
7470 It is also useless to compile subunits because they are compiled as needed
7474 There are no order of compilation requirements: performing a
7475 compilation never obsoletes anything. The only way you can obsolete
7476 something and require recompilations is to modify one of the
7477 source files on which it depends.
7480 There is no library as such, apart from the ALI files
7481 (@pxref{The Ada Library Information Files}, for information on the format
7482 of these files). For now we find it convenient to create separate ALI files,
7483 but eventually the information therein may be incorporated into the object
7487 When you compile a unit, the source files for the specs of all units
7488 that it @code{with}'s, all its subunits, and the bodies of any generics it
7489 instantiates must be available (reachable by the search-paths mechanism
7490 described above), or you will receive a fatal error message.
7497 The following are some typical Ada compilation command line examples:
7500 @item $ gcc -c xyz.adb
7501 Compile body in file @file{xyz.adb} with all default options.
7504 @item $ gcc -c -O2 -gnata xyz-def.adb
7507 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7510 Compile the child unit package in file @file{xyz-def.adb} with extensive
7511 optimizations, and pragma @code{Assert}/@code{Debug} statements
7514 @item $ gcc -c -gnatc abc-def.adb
7515 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7519 @node Binding Using gnatbind
7520 @chapter Binding Using @code{gnatbind}
7524 * Running gnatbind::
7525 * Switches for gnatbind::
7526 * Command-Line Access::
7527 * Search Paths for gnatbind::
7528 * Examples of gnatbind Usage::
7532 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7533 to bind compiled GNAT objects.
7535 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7536 driver (see @ref{The GNAT Driver and Project Files}).
7538 The @code{gnatbind} program performs four separate functions:
7542 Checks that a program is consistent, in accordance with the rules in
7543 Chapter 10 of the Ada Reference Manual. In particular, error
7544 messages are generated if a program uses inconsistent versions of a
7548 Checks that an acceptable order of elaboration exists for the program
7549 and issues an error message if it cannot find an order of elaboration
7550 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7553 Generates a main program incorporating the given elaboration order.
7554 This program is a small Ada package (body and spec) that
7555 must be subsequently compiled
7556 using the GNAT compiler. The necessary compilation step is usually
7557 performed automatically by @command{gnatlink}. The two most important
7558 functions of this program
7559 are to call the elaboration routines of units in an appropriate order
7560 and to call the main program.
7563 Determines the set of object files required by the given main program.
7564 This information is output in the forms of comments in the generated program,
7565 to be read by the @command{gnatlink} utility used to link the Ada application.
7568 @node Running gnatbind
7569 @section Running @code{gnatbind}
7572 The form of the @code{gnatbind} command is
7575 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7579 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7580 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7581 package in two files whose names are
7582 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7583 For example, if given the
7584 parameter @file{hello.ali}, for a main program contained in file
7585 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7586 and @file{b~hello.adb}.
7588 When doing consistency checking, the binder takes into consideration
7589 any source files it can locate. For example, if the binder determines
7590 that the given main program requires the package @code{Pack}, whose
7592 file is @file{pack.ali} and whose corresponding source spec file is
7593 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7594 (using the same search path conventions as previously described for the
7595 @command{gcc} command). If it can locate this source file, it checks that
7597 or source checksums of the source and its references to in @file{ALI} files
7598 match. In other words, any @file{ALI} files that mentions this spec must have
7599 resulted from compiling this version of the source file (or in the case
7600 where the source checksums match, a version close enough that the
7601 difference does not matter).
7603 @cindex Source files, use by binder
7604 The effect of this consistency checking, which includes source files, is
7605 that the binder ensures that the program is consistent with the latest
7606 version of the source files that can be located at bind time. Editing a
7607 source file without compiling files that depend on the source file cause
7608 error messages to be generated by the binder.
7610 For example, suppose you have a main program @file{hello.adb} and a
7611 package @code{P}, from file @file{p.ads} and you perform the following
7616 Enter @code{gcc -c hello.adb} to compile the main program.
7619 Enter @code{gcc -c p.ads} to compile package @code{P}.
7622 Edit file @file{p.ads}.
7625 Enter @code{gnatbind hello}.
7629 At this point, the file @file{p.ali} contains an out-of-date time stamp
7630 because the file @file{p.ads} has been edited. The attempt at binding
7631 fails, and the binder generates the following error messages:
7634 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7635 error: "p.ads" has been modified and must be recompiled
7639 Now both files must be recompiled as indicated, and then the bind can
7640 succeed, generating a main program. You need not normally be concerned
7641 with the contents of this file, but for reference purposes a sample
7642 binder output file is given in @ref{Example of Binder Output File}.
7644 In most normal usage, the default mode of @command{gnatbind} which is to
7645 generate the main package in Ada, as described in the previous section.
7646 In particular, this means that any Ada programmer can read and understand
7647 the generated main program. It can also be debugged just like any other
7648 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7649 @command{gnatbind} and @command{gnatlink}.
7651 However for some purposes it may be convenient to generate the main
7652 program in C rather than Ada. This may for example be helpful when you
7653 are generating a mixed language program with the main program in C. The
7654 GNAT compiler itself is an example.
7655 The use of the @option{^-C^/BIND_FILE=C^} switch
7656 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7657 be generated in C (and compiled using the gnu C compiler).
7659 @node Switches for gnatbind
7660 @section Switches for @command{gnatbind}
7663 The following switches are available with @code{gnatbind}; details will
7664 be presented in subsequent sections.
7667 * Consistency-Checking Modes::
7668 * Binder Error Message Control::
7669 * Elaboration Control::
7671 * Binding with Non-Ada Main Programs::
7672 * Binding Programs with No Main Subprogram::
7679 @cindex @option{--version} @command{gnatbind}
7680 Display Copyright and version, then exit disregarding all other options.
7683 @cindex @option{--help} @command{gnatbind}
7684 If @option{--version} was not used, display usage, then exit disregarding
7688 @cindex @option{-a} @command{gnatbind}
7689 Indicates that, if supported by the platform, the adainit procedure should
7690 be treated as an initialisation routine by the linker (a constructor). This
7691 is intended to be used by the Project Manager to automatically initialize
7692 shared Stand-Alone Libraries.
7694 @item ^-aO^/OBJECT_SEARCH^
7695 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7696 Specify directory to be searched for ALI files.
7698 @item ^-aI^/SOURCE_SEARCH^
7699 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7700 Specify directory to be searched for source file.
7702 @item ^-A^/BIND_FILE=ADA^
7703 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7704 Generate binder program in Ada (default)
7706 @item ^-b^/REPORT_ERRORS=BRIEF^
7707 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7708 Generate brief messages to @file{stderr} even if verbose mode set.
7710 @item ^-c^/NOOUTPUT^
7711 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7712 Check only, no generation of binder output file.
7714 @item ^-C^/BIND_FILE=C^
7715 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
7716 Generate binder program in C
7718 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7719 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
7720 This switch can be used to change the default task stack size value
7721 to a specified size @var{nn}, which is expressed in bytes by default, or
7722 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7724 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
7725 in effect, to completing all task specs with
7726 @smallexample @c ada
7727 pragma Storage_Size (nn);
7729 When they do not already have such a pragma.
7731 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7732 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
7733 This switch can be used to change the default secondary stack size value
7734 to a specified size @var{nn}, which is expressed in bytes by default, or
7735 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7738 The secondary stack is used to deal with functions that return a variable
7739 sized result, for example a function returning an unconstrained
7740 String. There are two ways in which this secondary stack is allocated.
7742 For most targets, the secondary stack is growing on demand and is allocated
7743 as a chain of blocks in the heap. The -D option is not very
7744 relevant. It only give some control over the size of the allocated
7745 blocks (whose size is the minimum of the default secondary stack size value,
7746 and the actual size needed for the current allocation request).
7748 For certain targets, notably VxWorks 653,
7749 the secondary stack is allocated by carving off a fixed ratio chunk of the
7750 primary task stack. The -D option is used to define the
7751 size of the environment task's secondary stack.
7753 @item ^-e^/ELABORATION_DEPENDENCIES^
7754 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
7755 Output complete list of elaboration-order dependencies.
7757 @item ^-E^/STORE_TRACEBACKS^
7758 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
7759 Store tracebacks in exception occurrences when the target supports it.
7760 This is the default with the zero cost exception mechanism.
7762 @c The following may get moved to an appendix
7763 This option is currently supported on the following targets:
7764 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
7766 See also the packages @code{GNAT.Traceback} and
7767 @code{GNAT.Traceback.Symbolic} for more information.
7769 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
7770 @command{gcc} option.
7773 @item ^-F^/FORCE_ELABS_FLAGS^
7774 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
7775 Force the checks of elaboration flags. @command{gnatbind} does not normally
7776 generate checks of elaboration flags for the main executable, except when
7777 a Stand-Alone Library is used. However, there are cases when this cannot be
7778 detected by gnatbind. An example is importing an interface of a Stand-Alone
7779 Library through a pragma Import and only specifying through a linker switch
7780 this Stand-Alone Library. This switch is used to guarantee that elaboration
7781 flag checks are generated.
7784 @cindex @option{^-h^/HELP^} (@command{gnatbind})
7785 Output usage (help) information
7788 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7789 Specify directory to be searched for source and ALI files.
7791 @item ^-I-^/NOCURRENT_DIRECTORY^
7792 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
7793 Do not look for sources in the current directory where @code{gnatbind} was
7794 invoked, and do not look for ALI files in the directory containing the
7795 ALI file named in the @code{gnatbind} command line.
7797 @item ^-l^/ORDER_OF_ELABORATION^
7798 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
7799 Output chosen elaboration order.
7801 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
7802 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
7803 Bind the units for library building. In this case the adainit and
7804 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
7805 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
7806 ^@var{xxx}final^@var{XXX}FINAL^.
7807 Implies ^-n^/NOCOMPILE^.
7809 (@xref{GNAT and Libraries}, for more details.)
7812 On OpenVMS, these init and final procedures are exported in uppercase
7813 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
7814 the init procedure will be "TOTOINIT" and the exported name of the final
7815 procedure will be "TOTOFINAL".
7818 @item ^-Mxyz^/RENAME_MAIN=xyz^
7819 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
7820 Rename generated main program from main to xyz. This option is
7821 supported on cross environments only.
7823 @item ^-m^/ERROR_LIMIT=^@var{n}
7824 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
7825 Limit number of detected errors or warnings to @var{n}, where @var{n} is
7826 in the range 1..999999. The default value if no switch is
7827 given is 9999. If the number of warnings reaches this limit, then a
7828 message is output and further warnings are suppressed, the bind
7829 continues in this case. If the number of errors reaches this
7830 limit, then a message is output and the bind is abandoned.
7831 A value of zero means that no limit is enforced. The equal
7835 Furthermore, under Windows, the sources pointed to by the libraries path
7836 set in the registry are not searched for.
7840 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7844 @cindex @option{-nostdinc} (@command{gnatbind})
7845 Do not look for sources in the system default directory.
7848 @cindex @option{-nostdlib} (@command{gnatbind})
7849 Do not look for library files in the system default directory.
7851 @item --RTS=@var{rts-path}
7852 @cindex @option{--RTS} (@code{gnatbind})
7853 Specifies the default location of the runtime library. Same meaning as the
7854 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
7856 @item ^-o ^/OUTPUT=^@var{file}
7857 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7858 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7859 Note that if this option is used, then linking must be done manually,
7860 gnatlink cannot be used.
7862 @item ^-O^/OBJECT_LIST^
7863 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7866 @item ^-p^/PESSIMISTIC_ELABORATION^
7867 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7868 Pessimistic (worst-case) elaboration order
7871 @cindex @option{^-R^-R^} (@command{gnatbind})
7872 Output closure source list.
7874 @item ^-s^/READ_SOURCES=ALL^
7875 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7876 Require all source files to be present.
7878 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7879 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7880 Specifies the value to be used when detecting uninitialized scalar
7881 objects with pragma Initialize_Scalars.
7882 The @var{xxx} ^string specified with the switch^option^ may be either
7884 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7885 @item ``@option{^lo^LOW^}'' for the lowest possible value
7886 @item ``@option{^hi^HIGH^}'' for the highest possible value
7887 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
7888 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
7891 In addition, you can specify @option{-Sev} to indicate that the value is
7892 to be set at run time. In this case, the program will look for an environment
7893 @cindex GNAT_INIT_SCALARS
7894 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
7895 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
7896 If no environment variable is found, or if it does not have a valid value,
7897 then the default is @option{in} (invalid values).
7901 @cindex @option{-static} (@code{gnatbind})
7902 Link against a static GNAT run time.
7905 @cindex @option{-shared} (@code{gnatbind})
7906 Link against a shared GNAT run time when available.
7909 @item ^-t^/NOTIME_STAMP_CHECK^
7910 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7911 Tolerate time stamp and other consistency errors
7913 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7914 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7915 Set the time slice value to @var{n} milliseconds. If the system supports
7916 the specification of a specific time slice value, then the indicated value
7917 is used. If the system does not support specific time slice values, but
7918 does support some general notion of round-robin scheduling, then any
7919 nonzero value will activate round-robin scheduling.
7921 A value of zero is treated specially. It turns off time
7922 slicing, and in addition, indicates to the tasking run time that the
7923 semantics should match as closely as possible the Annex D
7924 requirements of the Ada RM, and in particular sets the default
7925 scheduling policy to @code{FIFO_Within_Priorities}.
7927 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
7928 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
7929 Enable dynamic stack usage, with @var{n} results stored and displayed
7930 at program termination. A result is generated when a task
7931 terminates. Results that can't be stored are displayed on the fly, at
7932 task termination. This option is currently not supported on Itanium
7933 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
7935 @item ^-v^/REPORT_ERRORS=VERBOSE^
7936 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7937 Verbose mode. Write error messages, header, summary output to
7942 @cindex @option{-w} (@code{gnatbind})
7943 Warning mode (@var{x}=s/e for suppress/treat as error)
7947 @item /WARNINGS=NORMAL
7948 @cindex @option{/WARNINGS} (@code{gnatbind})
7949 Normal warnings mode. Warnings are issued but ignored
7951 @item /WARNINGS=SUPPRESS
7952 @cindex @option{/WARNINGS} (@code{gnatbind})
7953 All warning messages are suppressed
7955 @item /WARNINGS=ERROR
7956 @cindex @option{/WARNINGS} (@code{gnatbind})
7957 Warning messages are treated as fatal errors
7960 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
7961 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
7962 Override default wide character encoding for standard Text_IO files.
7964 @item ^-x^/READ_SOURCES=NONE^
7965 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7966 Exclude source files (check object consistency only).
7969 @item /READ_SOURCES=AVAILABLE
7970 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7971 Default mode, in which sources are checked for consistency only if
7975 @item ^-y^/ENABLE_LEAP_SECONDS^
7976 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
7977 Enable leap seconds support in @code{Ada.Calendar} and its children.
7979 @item ^-z^/ZERO_MAIN^
7980 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7986 You may obtain this listing of switches by running @code{gnatbind} with
7990 @node Consistency-Checking Modes
7991 @subsection Consistency-Checking Modes
7994 As described earlier, by default @code{gnatbind} checks
7995 that object files are consistent with one another and are consistent
7996 with any source files it can locate. The following switches control binder
8001 @item ^-s^/READ_SOURCES=ALL^
8002 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8003 Require source files to be present. In this mode, the binder must be
8004 able to locate all source files that are referenced, in order to check
8005 their consistency. In normal mode, if a source file cannot be located it
8006 is simply ignored. If you specify this switch, a missing source
8009 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8010 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8011 Override default wide character encoding for standard Text_IO files.
8012 Normally the default wide character encoding method used for standard
8013 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8014 the main source input (see description of switch
8015 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8016 use of this switch for the binder (which has the same set of
8017 possible arguments) overrides this default as specified.
8019 @item ^-x^/READ_SOURCES=NONE^
8020 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8021 Exclude source files. In this mode, the binder only checks that ALI
8022 files are consistent with one another. Source files are not accessed.
8023 The binder runs faster in this mode, and there is still a guarantee that
8024 the resulting program is self-consistent.
8025 If a source file has been edited since it was last compiled, and you
8026 specify this switch, the binder will not detect that the object
8027 file is out of date with respect to the source file. Note that this is the
8028 mode that is automatically used by @command{gnatmake} because in this
8029 case the checking against sources has already been performed by
8030 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8033 @item /READ_SOURCES=AVAILABLE
8034 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8035 This is the default mode in which source files are checked if they are
8036 available, and ignored if they are not available.
8040 @node Binder Error Message Control
8041 @subsection Binder Error Message Control
8044 The following switches provide control over the generation of error
8045 messages from the binder:
8049 @item ^-v^/REPORT_ERRORS=VERBOSE^
8050 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8051 Verbose mode. In the normal mode, brief error messages are generated to
8052 @file{stderr}. If this switch is present, a header is written
8053 to @file{stdout} and any error messages are directed to @file{stdout}.
8054 All that is written to @file{stderr} is a brief summary message.
8056 @item ^-b^/REPORT_ERRORS=BRIEF^
8057 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8058 Generate brief error messages to @file{stderr} even if verbose mode is
8059 specified. This is relevant only when used with the
8060 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8064 @cindex @option{-m} (@code{gnatbind})
8065 Limits the number of error messages to @var{n}, a decimal integer in the
8066 range 1-999. The binder terminates immediately if this limit is reached.
8069 @cindex @option{-M} (@code{gnatbind})
8070 Renames the generated main program from @code{main} to @code{xxx}.
8071 This is useful in the case of some cross-building environments, where
8072 the actual main program is separate from the one generated
8076 @item ^-ws^/WARNINGS=SUPPRESS^
8077 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8079 Suppress all warning messages.
8081 @item ^-we^/WARNINGS=ERROR^
8082 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8083 Treat any warning messages as fatal errors.
8086 @item /WARNINGS=NORMAL
8087 Standard mode with warnings generated, but warnings do not get treated
8091 @item ^-t^/NOTIME_STAMP_CHECK^
8092 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8093 @cindex Time stamp checks, in binder
8094 @cindex Binder consistency checks
8095 @cindex Consistency checks, in binder
8096 The binder performs a number of consistency checks including:
8100 Check that time stamps of a given source unit are consistent
8102 Check that checksums of a given source unit are consistent
8104 Check that consistent versions of @code{GNAT} were used for compilation
8106 Check consistency of configuration pragmas as required
8110 Normally failure of such checks, in accordance with the consistency
8111 requirements of the Ada Reference Manual, causes error messages to be
8112 generated which abort the binder and prevent the output of a binder
8113 file and subsequent link to obtain an executable.
8115 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8116 into warnings, so that
8117 binding and linking can continue to completion even in the presence of such
8118 errors. The result may be a failed link (due to missing symbols), or a
8119 non-functional executable which has undefined semantics.
8120 @emph{This means that
8121 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8125 @node Elaboration Control
8126 @subsection Elaboration Control
8129 The following switches provide additional control over the elaboration
8130 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8133 @item ^-p^/PESSIMISTIC_ELABORATION^
8134 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8135 Normally the binder attempts to choose an elaboration order that is
8136 likely to minimize the likelihood of an elaboration order error resulting
8137 in raising a @code{Program_Error} exception. This switch reverses the
8138 action of the binder, and requests that it deliberately choose an order
8139 that is likely to maximize the likelihood of an elaboration error.
8140 This is useful in ensuring portability and avoiding dependence on
8141 accidental fortuitous elaboration ordering.
8143 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8145 elaboration checking is used (@option{-gnatE} switch used for compilation).
8146 This is because in the default static elaboration mode, all necessary
8147 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8148 These implicit pragmas are still respected by the binder in
8149 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8150 safe elaboration order is assured.
8153 @node Output Control
8154 @subsection Output Control
8157 The following switches allow additional control over the output
8158 generated by the binder.
8163 @item ^-A^/BIND_FILE=ADA^
8164 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8165 Generate binder program in Ada (default). The binder program is named
8166 @file{b~@var{mainprog}.adb} by default. This can be changed with
8167 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8169 @item ^-c^/NOOUTPUT^
8170 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8171 Check only. Do not generate the binder output file. In this mode the
8172 binder performs all error checks but does not generate an output file.
8174 @item ^-C^/BIND_FILE=C^
8175 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8176 Generate binder program in C. The binder program is named
8177 @file{b_@var{mainprog}.c}.
8178 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8181 @item ^-e^/ELABORATION_DEPENDENCIES^
8182 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8183 Output complete list of elaboration-order dependencies, showing the
8184 reason for each dependency. This output can be rather extensive but may
8185 be useful in diagnosing problems with elaboration order. The output is
8186 written to @file{stdout}.
8189 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8190 Output usage information. The output is written to @file{stdout}.
8192 @item ^-K^/LINKER_OPTION_LIST^
8193 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8194 Output linker options to @file{stdout}. Includes library search paths,
8195 contents of pragmas Ident and Linker_Options, and libraries added
8198 @item ^-l^/ORDER_OF_ELABORATION^
8199 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8200 Output chosen elaboration order. The output is written to @file{stdout}.
8202 @item ^-O^/OBJECT_LIST^
8203 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8204 Output full names of all the object files that must be linked to provide
8205 the Ada component of the program. The output is written to @file{stdout}.
8206 This list includes the files explicitly supplied and referenced by the user
8207 as well as implicitly referenced run-time unit files. The latter are
8208 omitted if the corresponding units reside in shared libraries. The
8209 directory names for the run-time units depend on the system configuration.
8211 @item ^-o ^/OUTPUT=^@var{file}
8212 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8213 Set name of output file to @var{file} instead of the normal
8214 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8215 binder generated body filename. In C mode you would normally give
8216 @var{file} an extension of @file{.c} because it will be a C source program.
8217 Note that if this option is used, then linking must be done manually.
8218 It is not possible to use gnatlink in this case, since it cannot locate
8221 @item ^-r^/RESTRICTION_LIST^
8222 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8223 Generate list of @code{pragma Restrictions} that could be applied to
8224 the current unit. This is useful for code audit purposes, and also may
8225 be used to improve code generation in some cases.
8229 @node Binding with Non-Ada Main Programs
8230 @subsection Binding with Non-Ada Main Programs
8233 In our description so far we have assumed that the main
8234 program is in Ada, and that the task of the binder is to generate a
8235 corresponding function @code{main} that invokes this Ada main
8236 program. GNAT also supports the building of executable programs where
8237 the main program is not in Ada, but some of the called routines are
8238 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8239 The following switch is used in this situation:
8243 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8244 No main program. The main program is not in Ada.
8248 In this case, most of the functions of the binder are still required,
8249 but instead of generating a main program, the binder generates a file
8250 containing the following callable routines:
8255 You must call this routine to initialize the Ada part of the program by
8256 calling the necessary elaboration routines. A call to @code{adainit} is
8257 required before the first call to an Ada subprogram.
8259 Note that it is assumed that the basic execution environment must be setup
8260 to be appropriate for Ada execution at the point where the first Ada
8261 subprogram is called. In particular, if the Ada code will do any
8262 floating-point operations, then the FPU must be setup in an appropriate
8263 manner. For the case of the x86, for example, full precision mode is
8264 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8265 that the FPU is in the right state.
8269 You must call this routine to perform any library-level finalization
8270 required by the Ada subprograms. A call to @code{adafinal} is required
8271 after the last call to an Ada subprogram, and before the program
8276 If the @option{^-n^/NOMAIN^} switch
8277 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8278 @cindex Binder, multiple input files
8279 is given, more than one ALI file may appear on
8280 the command line for @code{gnatbind}. The normal @dfn{closure}
8281 calculation is performed for each of the specified units. Calculating
8282 the closure means finding out the set of units involved by tracing
8283 @code{with} references. The reason it is necessary to be able to
8284 specify more than one ALI file is that a given program may invoke two or
8285 more quite separate groups of Ada units.
8287 The binder takes the name of its output file from the last specified ALI
8288 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8289 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8290 The output is an Ada unit in source form that can
8291 be compiled with GNAT unless the -C switch is used in which case the
8292 output is a C source file, which must be compiled using the C compiler.
8293 This compilation occurs automatically as part of the @command{gnatlink}
8296 Currently the GNAT run time requires a FPU using 80 bits mode
8297 precision. Under targets where this is not the default it is required to
8298 call GNAT.Float_Control.Reset before using floating point numbers (this
8299 include float computation, float input and output) in the Ada code. A
8300 side effect is that this could be the wrong mode for the foreign code
8301 where floating point computation could be broken after this call.
8303 @node Binding Programs with No Main Subprogram
8304 @subsection Binding Programs with No Main Subprogram
8307 It is possible to have an Ada program which does not have a main
8308 subprogram. This program will call the elaboration routines of all the
8309 packages, then the finalization routines.
8311 The following switch is used to bind programs organized in this manner:
8314 @item ^-z^/ZERO_MAIN^
8315 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8316 Normally the binder checks that the unit name given on the command line
8317 corresponds to a suitable main subprogram. When this switch is used,
8318 a list of ALI files can be given, and the execution of the program
8319 consists of elaboration of these units in an appropriate order. Note
8320 that the default wide character encoding method for standard Text_IO
8321 files is always set to Brackets if this switch is set (you can use
8323 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8326 @node Command-Line Access
8327 @section Command-Line Access
8330 The package @code{Ada.Command_Line} provides access to the command-line
8331 arguments and program name. In order for this interface to operate
8332 correctly, the two variables
8344 are declared in one of the GNAT library routines. These variables must
8345 be set from the actual @code{argc} and @code{argv} values passed to the
8346 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8347 generates the C main program to automatically set these variables.
8348 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8349 set these variables. If they are not set, the procedures in
8350 @code{Ada.Command_Line} will not be available, and any attempt to use
8351 them will raise @code{Constraint_Error}. If command line access is
8352 required, your main program must set @code{gnat_argc} and
8353 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8356 @node Search Paths for gnatbind
8357 @section Search Paths for @code{gnatbind}
8360 The binder takes the name of an ALI file as its argument and needs to
8361 locate source files as well as other ALI files to verify object consistency.
8363 For source files, it follows exactly the same search rules as @command{gcc}
8364 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8365 directories searched are:
8369 The directory containing the ALI file named in the command line, unless
8370 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8373 All directories specified by @option{^-I^/SEARCH^}
8374 switches on the @code{gnatbind}
8375 command line, in the order given.
8378 @findex ADA_PRJ_OBJECTS_FILE
8379 Each of the directories listed in the text file whose name is given
8380 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8383 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8384 driver when project files are used. It should not normally be set
8388 @findex ADA_OBJECTS_PATH
8389 Each of the directories listed in the value of the
8390 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8392 Construct this value
8393 exactly as the @env{PATH} environment variable: a list of directory
8394 names separated by colons (semicolons when working with the NT version
8398 Normally, define this value as a logical name containing a comma separated
8399 list of directory names.
8401 This variable can also be defined by means of an environment string
8402 (an argument to the HP C exec* set of functions).
8406 DEFINE ANOTHER_PATH FOO:[BAG]
8407 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8410 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8411 first, followed by the standard Ada
8412 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8413 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8414 (Text_IO, Sequential_IO, etc)
8415 instead of the standard Ada packages. Thus, in order to get the standard Ada
8416 packages by default, ADA_OBJECTS_PATH must be redefined.
8420 The content of the @file{ada_object_path} file which is part of the GNAT
8421 installation tree and is used to store standard libraries such as the
8422 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8425 @ref{Installing a library}
8430 In the binder the switch @option{^-I^/SEARCH^}
8431 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8432 is used to specify both source and
8433 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8434 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8435 instead if you want to specify
8436 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8437 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8438 if you want to specify library paths
8439 only. This means that for the binder
8440 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8441 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8442 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8443 The binder generates the bind file (a C language source file) in the
8444 current working directory.
8450 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8451 children make up the GNAT Run-Time Library, together with the package
8452 GNAT and its children, which contain a set of useful additional
8453 library functions provided by GNAT. The sources for these units are
8454 needed by the compiler and are kept together in one directory. The ALI
8455 files and object files generated by compiling the RTL are needed by the
8456 binder and the linker and are kept together in one directory, typically
8457 different from the directory containing the sources. In a normal
8458 installation, you need not specify these directory names when compiling
8459 or binding. Either the environment variables or the built-in defaults
8460 cause these files to be found.
8462 Besides simplifying access to the RTL, a major use of search paths is
8463 in compiling sources from multiple directories. This can make
8464 development environments much more flexible.
8466 @node Examples of gnatbind Usage
8467 @section Examples of @code{gnatbind} Usage
8470 This section contains a number of examples of using the GNAT binding
8471 utility @code{gnatbind}.
8474 @item gnatbind hello
8475 The main program @code{Hello} (source program in @file{hello.adb}) is
8476 bound using the standard switch settings. The generated main program is
8477 @file{b~hello.adb}. This is the normal, default use of the binder.
8480 @item gnatbind hello -o mainprog.adb
8483 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8485 The main program @code{Hello} (source program in @file{hello.adb}) is
8486 bound using the standard switch settings. The generated main program is
8487 @file{mainprog.adb} with the associated spec in
8488 @file{mainprog.ads}. Note that you must specify the body here not the
8489 spec, in the case where the output is in Ada. Note that if this option
8490 is used, then linking must be done manually, since gnatlink will not
8491 be able to find the generated file.
8494 @item gnatbind main -C -o mainprog.c -x
8497 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8499 The main program @code{Main} (source program in
8500 @file{main.adb}) is bound, excluding source files from the
8501 consistency checking, generating
8502 the file @file{mainprog.c}.
8505 @item gnatbind -x main_program -C -o mainprog.c
8506 This command is exactly the same as the previous example. Switches may
8507 appear anywhere in the command line, and single letter switches may be
8508 combined into a single switch.
8512 @item gnatbind -n math dbase -C -o ada-control.c
8515 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8517 The main program is in a language other than Ada, but calls to
8518 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8519 to @code{gnatbind} generates the file @file{ada-control.c} containing
8520 the @code{adainit} and @code{adafinal} routines to be called before and
8521 after accessing the Ada units.
8524 @c ------------------------------------
8525 @node Linking Using gnatlink
8526 @chapter Linking Using @command{gnatlink}
8527 @c ------------------------------------
8531 This chapter discusses @command{gnatlink}, a tool that links
8532 an Ada program and builds an executable file. This utility
8533 invokes the system linker ^(via the @command{gcc} command)^^
8534 with a correct list of object files and library references.
8535 @command{gnatlink} automatically determines the list of files and
8536 references for the Ada part of a program. It uses the binder file
8537 generated by the @command{gnatbind} to determine this list.
8539 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8540 driver (see @ref{The GNAT Driver and Project Files}).
8543 * Running gnatlink::
8544 * Switches for gnatlink::
8547 @node Running gnatlink
8548 @section Running @command{gnatlink}
8551 The form of the @command{gnatlink} command is
8554 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8555 @ovar{non-Ada objects} @ovar{linker options}
8559 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8561 or linker options) may be in any order, provided that no non-Ada object may
8562 be mistaken for a main @file{ALI} file.
8563 Any file name @file{F} without the @file{.ali}
8564 extension will be taken as the main @file{ALI} file if a file exists
8565 whose name is the concatenation of @file{F} and @file{.ali}.
8568 @file{@var{mainprog}.ali} references the ALI file of the main program.
8569 The @file{.ali} extension of this file can be omitted. From this
8570 reference, @command{gnatlink} locates the corresponding binder file
8571 @file{b~@var{mainprog}.adb} and, using the information in this file along
8572 with the list of non-Ada objects and linker options, constructs a
8573 linker command file to create the executable.
8575 The arguments other than the @command{gnatlink} switches and the main
8576 @file{ALI} file are passed to the linker uninterpreted.
8577 They typically include the names of
8578 object files for units written in other languages than Ada and any library
8579 references required to resolve references in any of these foreign language
8580 units, or in @code{Import} pragmas in any Ada units.
8582 @var{linker options} is an optional list of linker specific
8584 The default linker called by gnatlink is @command{gcc} which in
8585 turn calls the appropriate system linker.
8586 Standard options for the linker such as @option{-lmy_lib} or
8587 @option{-Ldir} can be added as is.
8588 For options that are not recognized by
8589 @command{gcc} as linker options, use the @command{gcc} switches
8590 @option{-Xlinker} or @option{-Wl,}.
8591 Refer to the GCC documentation for
8592 details. Here is an example showing how to generate a linker map:
8595 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8598 Using @var{linker options} it is possible to set the program stack and
8601 See @ref{Setting Stack Size from gnatlink} and
8602 @ref{Setting Heap Size from gnatlink}.
8605 @command{gnatlink} determines the list of objects required by the Ada
8606 program and prepends them to the list of objects passed to the linker.
8607 @command{gnatlink} also gathers any arguments set by the use of
8608 @code{pragma Linker_Options} and adds them to the list of arguments
8609 presented to the linker.
8612 @command{gnatlink} accepts the following types of extra files on the command
8613 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8614 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8615 handled according to their extension.
8618 @node Switches for gnatlink
8619 @section Switches for @command{gnatlink}
8622 The following switches are available with the @command{gnatlink} utility:
8628 @cindex @option{--version} @command{gnatlink}
8629 Display Copyright and version, then exit disregarding all other options.
8632 @cindex @option{--help} @command{gnatlink}
8633 If @option{--version} was not used, display usage, then exit disregarding
8636 @item ^-A^/BIND_FILE=ADA^
8637 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8638 The binder has generated code in Ada. This is the default.
8640 @item ^-C^/BIND_FILE=C^
8641 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8642 If instead of generating a file in Ada, the binder has generated one in
8643 C, then the linker needs to know about it. Use this switch to signal
8644 to @command{gnatlink} that the binder has generated C code rather than
8647 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8648 @cindex Command line length
8649 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8650 On some targets, the command line length is limited, and @command{gnatlink}
8651 will generate a separate file for the linker if the list of object files
8653 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8654 to be generated even if
8655 the limit is not exceeded. This is useful in some cases to deal with
8656 special situations where the command line length is exceeded.
8659 @cindex Debugging information, including
8660 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8661 The option to include debugging information causes the Ada bind file (in
8662 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8663 @option{^-g^/DEBUG^}.
8664 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8665 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8666 Without @option{^-g^/DEBUG^}, the binder removes these files by
8667 default. The same procedure apply if a C bind file was generated using
8668 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8669 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8671 @item ^-n^/NOCOMPILE^
8672 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8673 Do not compile the file generated by the binder. This may be used when
8674 a link is rerun with different options, but there is no need to recompile
8678 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8679 Causes additional information to be output, including a full list of the
8680 included object files. This switch option is most useful when you want
8681 to see what set of object files are being used in the link step.
8683 @item ^-v -v^/VERBOSE/VERBOSE^
8684 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8685 Very verbose mode. Requests that the compiler operate in verbose mode when
8686 it compiles the binder file, and that the system linker run in verbose mode.
8688 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8689 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8690 @var{exec-name} specifies an alternate name for the generated
8691 executable program. If this switch is omitted, the executable has the same
8692 name as the main unit. For example, @code{gnatlink try.ali} creates
8693 an executable called @file{^try^TRY.EXE^}.
8696 @item -b @var{target}
8697 @cindex @option{-b} (@command{gnatlink})
8698 Compile your program to run on @var{target}, which is the name of a
8699 system configuration. You must have a GNAT cross-compiler built if
8700 @var{target} is not the same as your host system.
8703 @cindex @option{-B} (@command{gnatlink})
8704 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8705 from @var{dir} instead of the default location. Only use this switch
8706 when multiple versions of the GNAT compiler are available.
8707 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8708 for further details. You would normally use the @option{-b} or
8709 @option{-V} switch instead.
8711 @item --GCC=@var{compiler_name}
8712 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8713 Program used for compiling the binder file. The default is
8714 @command{gcc}. You need to use quotes around @var{compiler_name} if
8715 @code{compiler_name} contains spaces or other separator characters.
8716 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8717 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8718 inserted after your command name. Thus in the above example the compiler
8719 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8720 A limitation of this syntax is that the name and path name of the executable
8721 itself must not include any embedded spaces. If the compiler executable is
8722 different from the default one (gcc or <prefix>-gcc), then the back-end
8723 switches in the ALI file are not used to compile the binder generated source.
8724 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8725 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8726 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8727 is taken into account. However, all the additional switches are also taken
8729 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8730 @option{--GCC="bar -x -y -z -t"}.
8732 @item --LINK=@var{name}
8733 @cindex @option{--LINK=} (@command{gnatlink})
8734 @var{name} is the name of the linker to be invoked. This is especially
8735 useful in mixed language programs since languages such as C++ require
8736 their own linker to be used. When this switch is omitted, the default
8737 name for the linker is @command{gcc}. When this switch is used, the
8738 specified linker is called instead of @command{gcc} with exactly the same
8739 parameters that would have been passed to @command{gcc} so if the desired
8740 linker requires different parameters it is necessary to use a wrapper
8741 script that massages the parameters before invoking the real linker. It
8742 may be useful to control the exact invocation by using the verbose
8748 @item /DEBUG=TRACEBACK
8749 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
8750 This qualifier causes sufficient information to be included in the
8751 executable file to allow a traceback, but does not include the full
8752 symbol information needed by the debugger.
8754 @item /IDENTIFICATION="<string>"
8755 @code{"<string>"} specifies the string to be stored in the image file
8756 identification field in the image header.
8757 It overrides any pragma @code{Ident} specified string.
8759 @item /NOINHIBIT-EXEC
8760 Generate the executable file even if there are linker warnings.
8762 @item /NOSTART_FILES
8763 Don't link in the object file containing the ``main'' transfer address.
8764 Used when linking with a foreign language main program compiled with an
8768 Prefer linking with object libraries over sharable images, even without
8774 @node The GNAT Make Program gnatmake
8775 @chapter The GNAT Make Program @command{gnatmake}
8779 * Running gnatmake::
8780 * Switches for gnatmake::
8781 * Mode Switches for gnatmake::
8782 * Notes on the Command Line::
8783 * How gnatmake Works::
8784 * Examples of gnatmake Usage::
8787 A typical development cycle when working on an Ada program consists of
8788 the following steps:
8792 Edit some sources to fix bugs.
8798 Compile all sources affected.
8808 The third step can be tricky, because not only do the modified files
8809 @cindex Dependency rules
8810 have to be compiled, but any files depending on these files must also be
8811 recompiled. The dependency rules in Ada can be quite complex, especially
8812 in the presence of overloading, @code{use} clauses, generics and inlined
8815 @command{gnatmake} automatically takes care of the third and fourth steps
8816 of this process. It determines which sources need to be compiled,
8817 compiles them, and binds and links the resulting object files.
8819 Unlike some other Ada make programs, the dependencies are always
8820 accurately recomputed from the new sources. The source based approach of
8821 the GNAT compilation model makes this possible. This means that if
8822 changes to the source program cause corresponding changes in
8823 dependencies, they will always be tracked exactly correctly by
8826 @node Running gnatmake
8827 @section Running @command{gnatmake}
8830 The usual form of the @command{gnatmake} command is
8833 $ gnatmake @ovar{switches} @var{file_name}
8834 @ovar{file_names} @ovar{mode_switches}
8838 The only required argument is one @var{file_name}, which specifies
8839 a compilation unit that is a main program. Several @var{file_names} can be
8840 specified: this will result in several executables being built.
8841 If @code{switches} are present, they can be placed before the first
8842 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8843 If @var{mode_switches} are present, they must always be placed after
8844 the last @var{file_name} and all @code{switches}.
8846 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
8847 extension may be omitted from the @var{file_name} arguments. However, if
8848 you are using non-standard extensions, then it is required that the
8849 extension be given. A relative or absolute directory path can be
8850 specified in a @var{file_name}, in which case, the input source file will
8851 be searched for in the specified directory only. Otherwise, the input
8852 source file will first be searched in the directory where
8853 @command{gnatmake} was invoked and if it is not found, it will be search on
8854 the source path of the compiler as described in
8855 @ref{Search Paths and the Run-Time Library (RTL)}.
8857 All @command{gnatmake} output (except when you specify
8858 @option{^-M^/DEPENDENCIES_LIST^}) is to
8859 @file{stderr}. The output produced by the
8860 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8863 @node Switches for gnatmake
8864 @section Switches for @command{gnatmake}
8867 You may specify any of the following switches to @command{gnatmake}:
8873 @cindex @option{--version} @command{gnatmake}
8874 Display Copyright and version, then exit disregarding all other options.
8877 @cindex @option{--help} @command{gnatmake}
8878 If @option{--version} was not used, display usage, then exit disregarding
8882 @item --GCC=@var{compiler_name}
8883 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
8884 Program used for compiling. The default is `@command{gcc}'. You need to use
8885 quotes around @var{compiler_name} if @code{compiler_name} contains
8886 spaces or other separator characters. As an example @option{--GCC="foo -x
8887 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
8888 compiler. A limitation of this syntax is that the name and path name of
8889 the executable itself must not include any embedded spaces. Note that
8890 switch @option{-c} is always inserted after your command name. Thus in the
8891 above example the compiler command that will be used by @command{gnatmake}
8892 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
8893 used, only the last @var{compiler_name} is taken into account. However,
8894 all the additional switches are also taken into account. Thus,
8895 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8896 @option{--GCC="bar -x -y -z -t"}.
8898 @item --GNATBIND=@var{binder_name}
8899 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
8900 Program used for binding. The default is `@code{gnatbind}'. You need to
8901 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8902 or other separator characters. As an example @option{--GNATBIND="bar -x
8903 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
8904 binder. Binder switches that are normally appended by @command{gnatmake}
8905 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8906 A limitation of this syntax is that the name and path name of the executable
8907 itself must not include any embedded spaces.
8909 @item --GNATLINK=@var{linker_name}
8910 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
8911 Program used for linking. The default is `@command{gnatlink}'. You need to
8912 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8913 or other separator characters. As an example @option{--GNATLINK="lan -x
8914 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
8915 linker. Linker switches that are normally appended by @command{gnatmake} to
8916 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
8917 A limitation of this syntax is that the name and path name of the executable
8918 itself must not include any embedded spaces.
8922 @item ^-a^/ALL_FILES^
8923 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
8924 Consider all files in the make process, even the GNAT internal system
8925 files (for example, the predefined Ada library files), as well as any
8926 locked files. Locked files are files whose ALI file is write-protected.
8928 @command{gnatmake} does not check these files,
8929 because the assumption is that the GNAT internal files are properly up
8930 to date, and also that any write protected ALI files have been properly
8931 installed. Note that if there is an installation problem, such that one
8932 of these files is not up to date, it will be properly caught by the
8934 You may have to specify this switch if you are working on GNAT
8935 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8936 in conjunction with @option{^-f^/FORCE_COMPILE^}
8937 if you need to recompile an entire application,
8938 including run-time files, using special configuration pragmas,
8939 such as a @code{Normalize_Scalars} pragma.
8942 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8945 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8948 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8951 @item ^-b^/ACTIONS=BIND^
8952 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
8953 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8954 compilation and binding, but no link.
8955 Can be combined with @option{^-l^/ACTIONS=LINK^}
8956 to do binding and linking. When not combined with
8957 @option{^-c^/ACTIONS=COMPILE^}
8958 all the units in the closure of the main program must have been previously
8959 compiled and must be up to date. The root unit specified by @var{file_name}
8960 may be given without extension, with the source extension or, if no GNAT
8961 Project File is specified, with the ALI file extension.
8963 @item ^-c^/ACTIONS=COMPILE^
8964 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
8965 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8966 is also specified. Do not perform linking, except if both
8967 @option{^-b^/ACTIONS=BIND^} and
8968 @option{^-l^/ACTIONS=LINK^} are also specified.
8969 If the root unit specified by @var{file_name} is not a main unit, this is the
8970 default. Otherwise @command{gnatmake} will attempt binding and linking
8971 unless all objects are up to date and the executable is more recent than
8975 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
8976 Use a temporary mapping file. A mapping file is a way to communicate to the
8977 compiler two mappings: from unit names to file names (without any directory
8978 information) and from file names to path names (with full directory
8979 information). These mappings are used by the compiler to short-circuit the path
8980 search. When @command{gnatmake} is invoked with this switch, it will create
8981 a temporary mapping file, initially populated by the project manager,
8982 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8983 Each invocation of the compiler will add the newly accessed sources to the
8984 mapping file. This will improve the source search during the next invocation
8987 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8988 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
8989 Use a specific mapping file. The file, specified as a path name (absolute or
8990 relative) by this switch, should already exist, otherwise the switch is
8991 ineffective. The specified mapping file will be communicated to the compiler.
8992 This switch is not compatible with a project file
8993 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
8994 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
8996 @item ^-d^/DISPLAY_PROGRESS^
8997 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
8998 Display progress for each source, up to date or not, as a single line
9001 completed x out of y (zz%)
9004 If the file needs to be compiled this is displayed after the invocation of
9005 the compiler. These lines are displayed even in quiet output mode.
9007 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9008 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9009 Put all object files and ALI file in directory @var{dir}.
9010 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9011 and ALI files go in the current working directory.
9013 This switch cannot be used when using a project file.
9017 @cindex @option{-eL} (@command{gnatmake})
9018 Follow all symbolic links when processing project files.
9021 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9022 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9023 Output the commands for the compiler, the binder and the linker
9024 on ^standard output^SYS$OUTPUT^,
9025 instead of ^standard error^SYS$ERROR^.
9027 @item ^-f^/FORCE_COMPILE^
9028 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9029 Force recompilations. Recompile all sources, even though some object
9030 files may be up to date, but don't recompile predefined or GNAT internal
9031 files or locked files (files with a write-protected ALI file),
9032 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9034 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9035 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9036 When using project files, if some errors or warnings are detected during
9037 parsing and verbose mode is not in effect (no use of switch
9038 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9039 file, rather than its simple file name.
9042 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9043 Enable debugging. This switch is simply passed to the compiler and to the
9046 @item ^-i^/IN_PLACE^
9047 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9048 In normal mode, @command{gnatmake} compiles all object files and ALI files
9049 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9050 then instead object files and ALI files that already exist are overwritten
9051 in place. This means that once a large project is organized into separate
9052 directories in the desired manner, then @command{gnatmake} will automatically
9053 maintain and update this organization. If no ALI files are found on the
9054 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9055 the new object and ALI files are created in the
9056 directory containing the source being compiled. If another organization
9057 is desired, where objects and sources are kept in different directories,
9058 a useful technique is to create dummy ALI files in the desired directories.
9059 When detecting such a dummy file, @command{gnatmake} will be forced to
9060 recompile the corresponding source file, and it will be put the resulting
9061 object and ALI files in the directory where it found the dummy file.
9063 @item ^-j^/PROCESSES=^@var{n}
9064 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9065 @cindex Parallel make
9066 Use @var{n} processes to carry out the (re)compilations. On a
9067 multiprocessor machine compilations will occur in parallel. In the
9068 event of compilation errors, messages from various compilations might
9069 get interspersed (but @command{gnatmake} will give you the full ordered
9070 list of failing compiles at the end). If this is problematic, rerun
9071 the make process with n set to 1 to get a clean list of messages.
9073 @item ^-k^/CONTINUE_ON_ERROR^
9074 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9075 Keep going. Continue as much as possible after a compilation error. To
9076 ease the programmer's task in case of compilation errors, the list of
9077 sources for which the compile fails is given when @command{gnatmake}
9080 If @command{gnatmake} is invoked with several @file{file_names} and with this
9081 switch, if there are compilation errors when building an executable,
9082 @command{gnatmake} will not attempt to build the following executables.
9084 @item ^-l^/ACTIONS=LINK^
9085 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9086 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9087 and linking. Linking will not be performed if combined with
9088 @option{^-c^/ACTIONS=COMPILE^}
9089 but not with @option{^-b^/ACTIONS=BIND^}.
9090 When not combined with @option{^-b^/ACTIONS=BIND^}
9091 all the units in the closure of the main program must have been previously
9092 compiled and must be up to date, and the main program needs to have been bound.
9093 The root unit specified by @var{file_name}
9094 may be given without extension, with the source extension or, if no GNAT
9095 Project File is specified, with the ALI file extension.
9097 @item ^-m^/MINIMAL_RECOMPILATION^
9098 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9099 Specify that the minimum necessary amount of recompilations
9100 be performed. In this mode @command{gnatmake} ignores time
9101 stamp differences when the only
9102 modifications to a source file consist in adding/removing comments,
9103 empty lines, spaces or tabs. This means that if you have changed the
9104 comments in a source file or have simply reformatted it, using this
9105 switch will tell @command{gnatmake} not to recompile files that depend on it
9106 (provided other sources on which these files depend have undergone no
9107 semantic modifications). Note that the debugging information may be
9108 out of date with respect to the sources if the @option{-m} switch causes
9109 a compilation to be switched, so the use of this switch represents a
9110 trade-off between compilation time and accurate debugging information.
9112 @item ^-M^/DEPENDENCIES_LIST^
9113 @cindex Dependencies, producing list
9114 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9115 Check if all objects are up to date. If they are, output the object
9116 dependences to @file{stdout} in a form that can be directly exploited in
9117 a @file{Makefile}. By default, each source file is prefixed with its
9118 (relative or absolute) directory name. This name is whatever you
9119 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9120 and @option{^-I^/SEARCH^} switches. If you use
9121 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9122 @option{^-q^/QUIET^}
9123 (see below), only the source file names,
9124 without relative paths, are output. If you just specify the
9125 @option{^-M^/DEPENDENCIES_LIST^}
9126 switch, dependencies of the GNAT internal system files are omitted. This
9127 is typically what you want. If you also specify
9128 the @option{^-a^/ALL_FILES^} switch,
9129 dependencies of the GNAT internal files are also listed. Note that
9130 dependencies of the objects in external Ada libraries (see switch
9131 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9134 @item ^-n^/DO_OBJECT_CHECK^
9135 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9136 Don't compile, bind, or link. Checks if all objects are up to date.
9137 If they are not, the full name of the first file that needs to be
9138 recompiled is printed.
9139 Repeated use of this option, followed by compiling the indicated source
9140 file, will eventually result in recompiling all required units.
9142 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9143 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9144 Output executable name. The name of the final executable program will be
9145 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9146 name for the executable will be the name of the input file in appropriate form
9147 for an executable file on the host system.
9149 This switch cannot be used when invoking @command{gnatmake} with several
9152 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9153 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9154 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9155 automatically missing object directories, library directories and exec
9158 @item ^-P^/PROJECT_FILE=^@var{project}
9159 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9160 Use project file @var{project}. Only one such switch can be used.
9161 @xref{gnatmake and Project Files}.
9164 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9165 Quiet. When this flag is not set, the commands carried out by
9166 @command{gnatmake} are displayed.
9168 @item ^-s^/SWITCH_CHECK/^
9169 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9170 Recompile if compiler switches have changed since last compilation.
9171 All compiler switches but -I and -o are taken into account in the
9173 orders between different ``first letter'' switches are ignored, but
9174 orders between same switches are taken into account. For example,
9175 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9176 is equivalent to @option{-O -g}.
9178 This switch is recommended when Integrated Preprocessing is used.
9181 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9182 Unique. Recompile at most the main files. It implies -c. Combined with
9183 -f, it is equivalent to calling the compiler directly. Note that using
9184 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9185 (@pxref{Project Files and Main Subprograms}).
9187 @item ^-U^/ALL_PROJECTS^
9188 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9189 When used without a project file or with one or several mains on the command
9190 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9191 on the command line, all sources of all project files are checked and compiled
9192 if not up to date, and libraries are rebuilt, if necessary.
9195 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9196 Verbose. Display the reason for all recompilations @command{gnatmake}
9197 decides are necessary, with the highest verbosity level.
9199 @item ^-vl^/LOW_VERBOSITY^
9200 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9201 Verbosity level Low. Display fewer lines than in verbosity Medium.
9203 @item ^-vm^/MEDIUM_VERBOSITY^
9204 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9205 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9207 @item ^-vh^/HIGH_VERBOSITY^
9208 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9209 Verbosity level High. Equivalent to ^-v^/REASONS^.
9211 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9212 Indicate the verbosity of the parsing of GNAT project files.
9213 @xref{Switches Related to Project Files}.
9215 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9216 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9217 Indicate that sources that are not part of any Project File may be compiled.
9218 Normally, when using Project Files, only sources that are part of a Project
9219 File may be compile. When this switch is used, a source outside of all Project
9220 Files may be compiled. The ALI file and the object file will be put in the
9221 object directory of the main Project. The compilation switches used will only
9222 be those specified on the command line. Even when
9223 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9224 command line need to be sources of a project file.
9226 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9227 Indicate that external variable @var{name} has the value @var{value}.
9228 The Project Manager will use this value for occurrences of
9229 @code{external(name)} when parsing the project file.
9230 @xref{Switches Related to Project Files}.
9233 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9234 No main subprogram. Bind and link the program even if the unit name
9235 given on the command line is a package name. The resulting executable
9236 will execute the elaboration routines of the package and its closure,
9237 then the finalization routines.
9242 @item @command{gcc} @asis{switches}
9244 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9245 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9248 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9249 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9250 automatically treated as a compiler switch, and passed on to all
9251 compilations that are carried out.
9256 Source and library search path switches:
9260 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9261 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9262 When looking for source files also look in directory @var{dir}.
9263 The order in which source files search is undertaken is
9264 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9266 @item ^-aL^/SKIP_MISSING=^@var{dir}
9267 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9268 Consider @var{dir} as being an externally provided Ada library.
9269 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9270 files have been located in directory @var{dir}. This allows you to have
9271 missing bodies for the units in @var{dir} and to ignore out of date bodies
9272 for the same units. You still need to specify
9273 the location of the specs for these units by using the switches
9274 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9275 or @option{^-I^/SEARCH=^@var{dir}}.
9276 Note: this switch is provided for compatibility with previous versions
9277 of @command{gnatmake}. The easier method of causing standard libraries
9278 to be excluded from consideration is to write-protect the corresponding
9281 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9282 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9283 When searching for library and object files, look in directory
9284 @var{dir}. The order in which library files are searched is described in
9285 @ref{Search Paths for gnatbind}.
9287 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9288 @cindex Search paths, for @command{gnatmake}
9289 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9290 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9291 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9293 @item ^-I^/SEARCH=^@var{dir}
9294 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9295 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9296 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9298 @item ^-I-^/NOCURRENT_DIRECTORY^
9299 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9300 @cindex Source files, suppressing search
9301 Do not look for source files in the directory containing the source
9302 file named in the command line.
9303 Do not look for ALI or object files in the directory
9304 where @command{gnatmake} was invoked.
9306 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9307 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9308 @cindex Linker libraries
9309 Add directory @var{dir} to the list of directories in which the linker
9310 will search for libraries. This is equivalent to
9311 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9313 Furthermore, under Windows, the sources pointed to by the libraries path
9314 set in the registry are not searched for.
9318 @cindex @option{-nostdinc} (@command{gnatmake})
9319 Do not look for source files in the system default directory.
9322 @cindex @option{-nostdlib} (@command{gnatmake})
9323 Do not look for library files in the system default directory.
9325 @item --RTS=@var{rts-path}
9326 @cindex @option{--RTS} (@command{gnatmake})
9327 Specifies the default location of the runtime library. GNAT looks for the
9329 in the following directories, and stops as soon as a valid runtime is found
9330 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9331 @file{ada_object_path} present):
9334 @item <current directory>/$rts_path
9336 @item <default-search-dir>/$rts_path
9338 @item <default-search-dir>/rts-$rts_path
9342 The selected path is handled like a normal RTS path.
9346 @node Mode Switches for gnatmake
9347 @section Mode Switches for @command{gnatmake}
9350 The mode switches (referred to as @code{mode_switches}) allow the
9351 inclusion of switches that are to be passed to the compiler itself, the
9352 binder or the linker. The effect of a mode switch is to cause all
9353 subsequent switches up to the end of the switch list, or up to the next
9354 mode switch, to be interpreted as switches to be passed on to the
9355 designated component of GNAT.
9359 @item -cargs @var{switches}
9360 @cindex @option{-cargs} (@command{gnatmake})
9361 Compiler switches. Here @var{switches} is a list of switches
9362 that are valid switches for @command{gcc}. They will be passed on to
9363 all compile steps performed by @command{gnatmake}.
9365 @item -bargs @var{switches}
9366 @cindex @option{-bargs} (@command{gnatmake})
9367 Binder switches. Here @var{switches} is a list of switches
9368 that are valid switches for @code{gnatbind}. They will be passed on to
9369 all bind steps performed by @command{gnatmake}.
9371 @item -largs @var{switches}
9372 @cindex @option{-largs} (@command{gnatmake})
9373 Linker switches. Here @var{switches} is a list of switches
9374 that are valid switches for @command{gnatlink}. They will be passed on to
9375 all link steps performed by @command{gnatmake}.
9377 @item -margs @var{switches}
9378 @cindex @option{-margs} (@command{gnatmake})
9379 Make switches. The switches are directly interpreted by @command{gnatmake},
9380 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9384 @node Notes on the Command Line
9385 @section Notes on the Command Line
9388 This section contains some additional useful notes on the operation
9389 of the @command{gnatmake} command.
9393 @cindex Recompilation, by @command{gnatmake}
9394 If @command{gnatmake} finds no ALI files, it recompiles the main program
9395 and all other units required by the main program.
9396 This means that @command{gnatmake}
9397 can be used for the initial compile, as well as during subsequent steps of
9398 the development cycle.
9401 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9402 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9403 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9407 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9408 is used to specify both source and
9409 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9410 instead if you just want to specify
9411 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9412 if you want to specify library paths
9416 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9417 This may conveniently be used to exclude standard libraries from
9418 consideration and in particular it means that the use of the
9419 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9420 unless @option{^-a^/ALL_FILES^} is also specified.
9423 @command{gnatmake} has been designed to make the use of Ada libraries
9424 particularly convenient. Assume you have an Ada library organized
9425 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9426 of your Ada compilation units,
9427 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9428 specs of these units, but no bodies. Then to compile a unit
9429 stored in @code{main.adb}, which uses this Ada library you would just type
9433 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9436 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9437 /SKIP_MISSING=@i{[OBJ_DIR]} main
9442 Using @command{gnatmake} along with the
9443 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9444 switch provides a mechanism for avoiding unnecessary recompilations. Using
9446 you can update the comments/format of your
9447 source files without having to recompile everything. Note, however, that
9448 adding or deleting lines in a source files may render its debugging
9449 info obsolete. If the file in question is a spec, the impact is rather
9450 limited, as that debugging info will only be useful during the
9451 elaboration phase of your program. For bodies the impact can be more
9452 significant. In all events, your debugger will warn you if a source file
9453 is more recent than the corresponding object, and alert you to the fact
9454 that the debugging information may be out of date.
9457 @node How gnatmake Works
9458 @section How @command{gnatmake} Works
9461 Generally @command{gnatmake} automatically performs all necessary
9462 recompilations and you don't need to worry about how it works. However,
9463 it may be useful to have some basic understanding of the @command{gnatmake}
9464 approach and in particular to understand how it uses the results of
9465 previous compilations without incorrectly depending on them.
9467 First a definition: an object file is considered @dfn{up to date} if the
9468 corresponding ALI file exists and if all the source files listed in the
9469 dependency section of this ALI file have time stamps matching those in
9470 the ALI file. This means that neither the source file itself nor any
9471 files that it depends on have been modified, and hence there is no need
9472 to recompile this file.
9474 @command{gnatmake} works by first checking if the specified main unit is up
9475 to date. If so, no compilations are required for the main unit. If not,
9476 @command{gnatmake} compiles the main program to build a new ALI file that
9477 reflects the latest sources. Then the ALI file of the main unit is
9478 examined to find all the source files on which the main program depends,
9479 and @command{gnatmake} recursively applies the above procedure on all these
9482 This process ensures that @command{gnatmake} only trusts the dependencies
9483 in an existing ALI file if they are known to be correct. Otherwise it
9484 always recompiles to determine a new, guaranteed accurate set of
9485 dependencies. As a result the program is compiled ``upside down'' from what may
9486 be more familiar as the required order of compilation in some other Ada
9487 systems. In particular, clients are compiled before the units on which
9488 they depend. The ability of GNAT to compile in any order is critical in
9489 allowing an order of compilation to be chosen that guarantees that
9490 @command{gnatmake} will recompute a correct set of new dependencies if
9493 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9494 imported by several of the executables, it will be recompiled at most once.
9496 Note: when using non-standard naming conventions
9497 (@pxref{Using Other File Names}), changing through a configuration pragmas
9498 file the version of a source and invoking @command{gnatmake} to recompile may
9499 have no effect, if the previous version of the source is still accessible
9500 by @command{gnatmake}. It may be necessary to use the switch
9501 ^-f^/FORCE_COMPILE^.
9503 @node Examples of gnatmake Usage
9504 @section Examples of @command{gnatmake} Usage
9507 @item gnatmake hello.adb
9508 Compile all files necessary to bind and link the main program
9509 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9510 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9512 @item gnatmake main1 main2 main3
9513 Compile all files necessary to bind and link the main programs
9514 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9515 (containing unit @code{Main2}) and @file{main3.adb}
9516 (containing unit @code{Main3}) and bind and link the resulting object files
9517 to generate three executable files @file{^main1^MAIN1.EXE^},
9518 @file{^main2^MAIN2.EXE^}
9519 and @file{^main3^MAIN3.EXE^}.
9522 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9526 @item gnatmake Main_Unit /QUIET
9527 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9528 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9530 Compile all files necessary to bind and link the main program unit
9531 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9532 be done with optimization level 2 and the order of elaboration will be
9533 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9534 displaying commands it is executing.
9537 @c *************************
9538 @node Improving Performance
9539 @chapter Improving Performance
9540 @cindex Improving performance
9543 This chapter presents several topics related to program performance.
9544 It first describes some of the tradeoffs that need to be considered
9545 and some of the techniques for making your program run faster.
9546 It then documents the @command{gnatelim} tool and unused subprogram/data
9547 elimination feature, which can reduce the size of program executables.
9549 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9550 driver (see @ref{The GNAT Driver and Project Files}).
9554 * Performance Considerations::
9555 * Text_IO Suggestions::
9556 * Reducing Size of Ada Executables with gnatelim::
9557 * Reducing Size of Executables with unused subprogram/data elimination::
9561 @c *****************************
9562 @node Performance Considerations
9563 @section Performance Considerations
9566 The GNAT system provides a number of options that allow a trade-off
9571 performance of the generated code
9574 speed of compilation
9577 minimization of dependences and recompilation
9580 the degree of run-time checking.
9584 The defaults (if no options are selected) aim at improving the speed
9585 of compilation and minimizing dependences, at the expense of performance
9586 of the generated code:
9593 no inlining of subprogram calls
9596 all run-time checks enabled except overflow and elaboration checks
9600 These options are suitable for most program development purposes. This
9601 chapter describes how you can modify these choices, and also provides
9602 some guidelines on debugging optimized code.
9605 * Controlling Run-Time Checks::
9606 * Use of Restrictions::
9607 * Optimization Levels::
9608 * Debugging Optimized Code::
9609 * Inlining of Subprograms::
9610 * Other Optimization Switches::
9611 * Optimization and Strict Aliasing::
9614 * Coverage Analysis::
9618 @node Controlling Run-Time Checks
9619 @subsection Controlling Run-Time Checks
9622 By default, GNAT generates all run-time checks, except integer overflow
9623 checks, stack overflow checks, and checks for access before elaboration on
9624 subprogram calls. The latter are not required in default mode, because all
9625 necessary checking is done at compile time.
9626 @cindex @option{-gnatp} (@command{gcc})
9627 @cindex @option{-gnato} (@command{gcc})
9628 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9629 be modified. @xref{Run-Time Checks}.
9631 Our experience is that the default is suitable for most development
9634 We treat integer overflow specially because these
9635 are quite expensive and in our experience are not as important as other
9636 run-time checks in the development process. Note that division by zero
9637 is not considered an overflow check, and divide by zero checks are
9638 generated where required by default.
9640 Elaboration checks are off by default, and also not needed by default, since
9641 GNAT uses a static elaboration analysis approach that avoids the need for
9642 run-time checking. This manual contains a full chapter discussing the issue
9643 of elaboration checks, and if the default is not satisfactory for your use,
9644 you should read this chapter.
9646 For validity checks, the minimal checks required by the Ada Reference
9647 Manual (for case statements and assignments to array elements) are on
9648 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9649 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9650 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9651 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9652 are also suppressed entirely if @option{-gnatp} is used.
9654 @cindex Overflow checks
9655 @cindex Checks, overflow
9658 @cindex pragma Suppress
9659 @cindex pragma Unsuppress
9660 Note that the setting of the switches controls the default setting of
9661 the checks. They may be modified using either @code{pragma Suppress} (to
9662 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9663 checks) in the program source.
9665 @node Use of Restrictions
9666 @subsection Use of Restrictions
9669 The use of pragma Restrictions allows you to control which features are
9670 permitted in your program. Apart from the obvious point that if you avoid
9671 relatively expensive features like finalization (enforceable by the use
9672 of pragma Restrictions (No_Finalization), the use of this pragma does not
9673 affect the generated code in most cases.
9675 One notable exception to this rule is that the possibility of task abort
9676 results in some distributed overhead, particularly if finalization or
9677 exception handlers are used. The reason is that certain sections of code
9678 have to be marked as non-abortable.
9680 If you use neither the @code{abort} statement, nor asynchronous transfer
9681 of control (@code{select @dots{} then abort}), then this distributed overhead
9682 is removed, which may have a general positive effect in improving
9683 overall performance. Especially code involving frequent use of tasking
9684 constructs and controlled types will show much improved performance.
9685 The relevant restrictions pragmas are
9687 @smallexample @c ada
9688 pragma Restrictions (No_Abort_Statements);
9689 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9693 It is recommended that these restriction pragmas be used if possible. Note
9694 that this also means that you can write code without worrying about the
9695 possibility of an immediate abort at any point.
9697 @node Optimization Levels
9698 @subsection Optimization Levels
9699 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9702 Without any optimization ^option,^qualifier,^
9703 the compiler's goal is to reduce the cost of
9704 compilation and to make debugging produce the expected results.
9705 Statements are independent: if you stop the program with a breakpoint between
9706 statements, you can then assign a new value to any variable or change
9707 the program counter to any other statement in the subprogram and get exactly
9708 the results you would expect from the source code.
9710 Turning on optimization makes the compiler attempt to improve the
9711 performance and/or code size at the expense of compilation time and
9712 possibly the ability to debug the program.
9715 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
9716 the last such option is the one that is effective.
9719 The default is optimization off. This results in the fastest compile
9720 times, but GNAT makes absolutely no attempt to optimize, and the
9721 generated programs are considerably larger and slower than when
9722 optimization is enabled. You can use the
9724 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
9725 @option{-O2}, @option{-O3}, and @option{-Os})
9728 @code{OPTIMIZE} qualifier
9730 to @command{gcc} to control the optimization level:
9733 @item ^-O0^/OPTIMIZE=NONE^
9734 No optimization (the default);
9735 generates unoptimized code but has
9736 the fastest compilation time.
9738 Note that many other compilers do fairly extensive optimization
9739 even if ``no optimization'' is specified. With gcc, it is
9740 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
9741 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
9742 really does mean no optimization at all. This difference between
9743 gcc and other compilers should be kept in mind when doing
9744 performance comparisons.
9746 @item ^-O1^/OPTIMIZE=SOME^
9747 Moderate optimization;
9748 optimizes reasonably well but does not
9749 degrade compilation time significantly.
9751 @item ^-O2^/OPTIMIZE=ALL^
9753 @itemx /OPTIMIZE=DEVELOPMENT
9756 generates highly optimized code and has
9757 the slowest compilation time.
9759 @item ^-O3^/OPTIMIZE=INLINING^
9760 Full optimization as in @option{-O2},
9761 and also attempts automatic inlining of small
9762 subprograms within a unit (@pxref{Inlining of Subprograms}).
9764 @item ^-Os^/OPTIMIZE=SPACE^
9765 Optimize space usage of resulting program.
9769 Higher optimization levels perform more global transformations on the
9770 program and apply more expensive analysis algorithms in order to generate
9771 faster and more compact code. The price in compilation time, and the
9772 resulting improvement in execution time,
9773 both depend on the particular application and the hardware environment.
9774 You should experiment to find the best level for your application.
9776 Since the precise set of optimizations done at each level will vary from
9777 release to release (and sometime from target to target), it is best to think
9778 of the optimization settings in general terms.
9779 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
9780 the GNU Compiler Collection (GCC)}, for details about
9781 ^the @option{-O} settings and a number of @option{-f} options that^how to^
9782 individually enable or disable specific optimizations.
9784 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
9785 been tested extensively at all optimization levels. There are some bugs
9786 which appear only with optimization turned on, but there have also been
9787 bugs which show up only in @emph{unoptimized} code. Selecting a lower
9788 level of optimization does not improve the reliability of the code
9789 generator, which in practice is highly reliable at all optimization
9792 Note regarding the use of @option{-O3}: The use of this optimization level
9793 is generally discouraged with GNAT, since it often results in larger
9794 executables which run more slowly. See further discussion of this point
9795 in @ref{Inlining of Subprograms}.
9797 @node Debugging Optimized Code
9798 @subsection Debugging Optimized Code
9799 @cindex Debugging optimized code
9800 @cindex Optimization and debugging
9803 Although it is possible to do a reasonable amount of debugging at
9805 nonzero optimization levels,
9806 the higher the level the more likely that
9809 @option{/OPTIMIZE} settings other than @code{NONE},
9810 such settings will make it more likely that
9812 source-level constructs will have been eliminated by optimization.
9813 For example, if a loop is strength-reduced, the loop
9814 control variable may be completely eliminated and thus cannot be
9815 displayed in the debugger.
9816 This can only happen at @option{-O2} or @option{-O3}.
9817 Explicit temporary variables that you code might be eliminated at
9818 ^level^setting^ @option{-O1} or higher.
9820 The use of the @option{^-g^/DEBUG^} switch,
9821 @cindex @option{^-g^/DEBUG^} (@command{gcc})
9822 which is needed for source-level debugging,
9823 affects the size of the program executable on disk,
9824 and indeed the debugging information can be quite large.
9825 However, it has no effect on the generated code (and thus does not
9826 degrade performance)
9828 Since the compiler generates debugging tables for a compilation unit before
9829 it performs optimizations, the optimizing transformations may invalidate some
9830 of the debugging data. You therefore need to anticipate certain
9831 anomalous situations that may arise while debugging optimized code.
9832 These are the most common cases:
9836 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
9838 the PC bouncing back and forth in the code. This may result from any of
9839 the following optimizations:
9843 @i{Common subexpression elimination:} using a single instance of code for a
9844 quantity that the source computes several times. As a result you
9845 may not be able to stop on what looks like a statement.
9848 @i{Invariant code motion:} moving an expression that does not change within a
9849 loop, to the beginning of the loop.
9852 @i{Instruction scheduling:} moving instructions so as to
9853 overlap loads and stores (typically) with other code, or in
9854 general to move computations of values closer to their uses. Often
9855 this causes you to pass an assignment statement without the assignment
9856 happening and then later bounce back to the statement when the
9857 value is actually needed. Placing a breakpoint on a line of code
9858 and then stepping over it may, therefore, not always cause all the
9859 expected side-effects.
9863 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
9864 two identical pieces of code are merged and the program counter suddenly
9865 jumps to a statement that is not supposed to be executed, simply because
9866 it (and the code following) translates to the same thing as the code
9867 that @emph{was} supposed to be executed. This effect is typically seen in
9868 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
9869 a @code{break} in a C @code{^switch^switch^} statement.
9872 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
9873 There are various reasons for this effect:
9877 In a subprogram prologue, a parameter may not yet have been moved to its
9881 A variable may be dead, and its register re-used. This is
9882 probably the most common cause.
9885 As mentioned above, the assignment of a value to a variable may
9889 A variable may be eliminated entirely by value propagation or
9890 other means. In this case, GCC may incorrectly generate debugging
9891 information for the variable
9895 In general, when an unexpected value appears for a local variable or parameter
9896 you should first ascertain if that value was actually computed by
9897 your program, as opposed to being incorrectly reported by the debugger.
9899 array elements in an object designated by an access value
9900 are generally less of a problem, once you have ascertained that the access
9902 Typically, this means checking variables in the preceding code and in the
9903 calling subprogram to verify that the value observed is explainable from other
9904 values (one must apply the procedure recursively to those
9905 other values); or re-running the code and stopping a little earlier
9906 (perhaps before the call) and stepping to better see how the variable obtained
9907 the value in question; or continuing to step @emph{from} the point of the
9908 strange value to see if code motion had simply moved the variable's
9913 In light of such anomalies, a recommended technique is to use @option{-O0}
9914 early in the software development cycle, when extensive debugging capabilities
9915 are most needed, and then move to @option{-O1} and later @option{-O2} as
9916 the debugger becomes less critical.
9917 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9918 a release management issue.
9920 Note that if you use @option{-g} you can then use the @command{strip} program
9921 on the resulting executable,
9922 which removes both debugging information and global symbols.
9925 @node Inlining of Subprograms
9926 @subsection Inlining of Subprograms
9929 A call to a subprogram in the current unit is inlined if all the
9930 following conditions are met:
9934 The optimization level is at least @option{-O1}.
9937 The called subprogram is suitable for inlining: It must be small enough
9938 and not contain something that @command{gcc} cannot support in inlined
9942 @cindex pragma Inline
9944 Either @code{pragma Inline} applies to the subprogram, or it is local
9945 to the unit and called once from within it, or it is small and automatic
9946 inlining (optimization level @option{-O3}) is specified.
9950 Calls to subprograms in @code{with}'ed units are normally not inlined.
9951 To achieve actual inlining (that is, replacement of the call by the code
9952 in the body of the subprogram), the following conditions must all be true.
9956 The optimization level is at least @option{-O1}.
9959 The called subprogram is suitable for inlining: It must be small enough
9960 and not contain something that @command{gcc} cannot support in inlined
9964 The call appears in a body (not in a package spec).
9967 There is a @code{pragma Inline} for the subprogram.
9970 @cindex @option{-gnatn} (@command{gcc})
9971 The @option{^-gnatn^/INLINE^} switch
9972 is used in the @command{gcc} command line
9975 Even if all these conditions are met, it may not be possible for
9976 the compiler to inline the call, due to the length of the body,
9977 or features in the body that make it impossible for the compiler
9980 Note that specifying the @option{-gnatn} switch causes additional
9981 compilation dependencies. Consider the following:
9983 @smallexample @c ada
10003 With the default behavior (no @option{-gnatn} switch specified), the
10004 compilation of the @code{Main} procedure depends only on its own source,
10005 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10006 means that editing the body of @code{R} does not require recompiling
10009 On the other hand, the call @code{R.Q} is not inlined under these
10010 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10011 is compiled, the call will be inlined if the body of @code{Q} is small
10012 enough, but now @code{Main} depends on the body of @code{R} in
10013 @file{r.adb} as well as on the spec. This means that if this body is edited,
10014 the main program must be recompiled. Note that this extra dependency
10015 occurs whether or not the call is in fact inlined by @command{gcc}.
10017 The use of front end inlining with @option{-gnatN} generates similar
10018 additional dependencies.
10020 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10021 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10022 can be used to prevent
10023 all inlining. This switch overrides all other conditions and ensures
10024 that no inlining occurs. The extra dependences resulting from
10025 @option{-gnatn} will still be active, even if
10026 this switch is used to suppress the resulting inlining actions.
10028 @cindex @option{-fno-inline-functions} (@command{gcc})
10029 Note: The @option{-fno-inline-functions} switch can be used to prevent
10030 automatic inlining of small subprograms if @option{-O3} is used.
10032 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10033 Note: The @option{-fno-inline-functions-called-once} switch
10034 can be used to prevent inlining of subprograms local to the unit
10035 and called once from within it if @option{-O1} is used.
10037 Note regarding the use of @option{-O3}: There is no difference in inlining
10038 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10039 pragma @code{Inline} assuming the use of @option{-gnatn}
10040 or @option{-gnatN} (the switches that activate inlining). If you have used
10041 pragma @code{Inline} in appropriate cases, then it is usually much better
10042 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10043 in this case only has the effect of inlining subprograms you did not
10044 think should be inlined. We often find that the use of @option{-O3} slows
10045 down code by performing excessive inlining, leading to increased instruction
10046 cache pressure from the increased code size. So the bottom line here is
10047 that you should not automatically assume that @option{-O3} is better than
10048 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10049 it actually improves performance.
10051 @node Other Optimization Switches
10052 @subsection Other Optimization Switches
10053 @cindex Optimization Switches
10055 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10056 @command{gcc} optimization switches are potentially usable. These switches
10057 have not been extensively tested with GNAT but can generally be expected
10058 to work. Examples of switches in this category are
10059 @option{-funroll-loops} and
10060 the various target-specific @option{-m} options (in particular, it has been
10061 observed that @option{-march=pentium4} can significantly improve performance
10062 on appropriate machines). For full details of these switches, see
10063 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10064 the GNU Compiler Collection (GCC)}.
10066 @node Optimization and Strict Aliasing
10067 @subsection Optimization and Strict Aliasing
10069 @cindex Strict Aliasing
10070 @cindex No_Strict_Aliasing
10073 The strong typing capabilities of Ada allow an optimizer to generate
10074 efficient code in situations where other languages would be forced to
10075 make worst case assumptions preventing such optimizations. Consider
10076 the following example:
10078 @smallexample @c ada
10081 type Int1 is new Integer;
10082 type Int2 is new Integer;
10083 type Int1A is access Int1;
10084 type Int2A is access Int2;
10091 for J in Data'Range loop
10092 if Data (J) = Int1V.all then
10093 Int2V.all := Int2V.all + 1;
10102 In this example, since the variable @code{Int1V} can only access objects
10103 of type @code{Int1}, and @code{Int2V} can only access objects of type
10104 @code{Int2}, there is no possibility that the assignment to
10105 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10106 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10107 for all iterations of the loop and avoid the extra memory reference
10108 required to dereference it each time through the loop.
10110 This kind of optimization, called strict aliasing analysis, is
10111 triggered by specifying an optimization level of @option{-O2} or
10112 higher and allows @code{GNAT} to generate more efficient code
10113 when access values are involved.
10115 However, although this optimization is always correct in terms of
10116 the formal semantics of the Ada Reference Manual, difficulties can
10117 arise if features like @code{Unchecked_Conversion} are used to break
10118 the typing system. Consider the following complete program example:
10120 @smallexample @c ada
10123 type int1 is new integer;
10124 type int2 is new integer;
10125 type a1 is access int1;
10126 type a2 is access int2;
10131 function to_a2 (Input : a1) return a2;
10134 with Unchecked_Conversion;
10136 function to_a2 (Input : a1) return a2 is
10138 new Unchecked_Conversion (a1, a2);
10140 return to_a2u (Input);
10146 with Text_IO; use Text_IO;
10148 v1 : a1 := new int1;
10149 v2 : a2 := to_a2 (v1);
10153 put_line (int1'image (v1.all));
10159 This program prints out 0 in @option{-O0} or @option{-O1}
10160 mode, but it prints out 1 in @option{-O2} mode. That's
10161 because in strict aliasing mode, the compiler can and
10162 does assume that the assignment to @code{v2.all} could not
10163 affect the value of @code{v1.all}, since different types
10166 This behavior is not a case of non-conformance with the standard, since
10167 the Ada RM specifies that an unchecked conversion where the resulting
10168 bit pattern is not a correct value of the target type can result in an
10169 abnormal value and attempting to reference an abnormal value makes the
10170 execution of a program erroneous. That's the case here since the result
10171 does not point to an object of type @code{int2}. This means that the
10172 effect is entirely unpredictable.
10174 However, although that explanation may satisfy a language
10175 lawyer, in practice an applications programmer expects an
10176 unchecked conversion involving pointers to create true
10177 aliases and the behavior of printing 1 seems plain wrong.
10178 In this case, the strict aliasing optimization is unwelcome.
10180 Indeed the compiler recognizes this possibility, and the
10181 unchecked conversion generates a warning:
10184 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10185 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10186 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10190 Unfortunately the problem is recognized when compiling the body of
10191 package @code{p2}, but the actual "bad" code is generated while
10192 compiling the body of @code{m} and this latter compilation does not see
10193 the suspicious @code{Unchecked_Conversion}.
10195 As implied by the warning message, there are approaches you can use to
10196 avoid the unwanted strict aliasing optimization in a case like this.
10198 One possibility is to simply avoid the use of @option{-O2}, but
10199 that is a bit drastic, since it throws away a number of useful
10200 optimizations that do not involve strict aliasing assumptions.
10202 A less drastic approach is to compile the program using the
10203 option @option{-fno-strict-aliasing}. Actually it is only the
10204 unit containing the dereferencing of the suspicious pointer
10205 that needs to be compiled. So in this case, if we compile
10206 unit @code{m} with this switch, then we get the expected
10207 value of zero printed. Analyzing which units might need
10208 the switch can be painful, so a more reasonable approach
10209 is to compile the entire program with options @option{-O2}
10210 and @option{-fno-strict-aliasing}. If the performance is
10211 satisfactory with this combination of options, then the
10212 advantage is that the entire issue of possible "wrong"
10213 optimization due to strict aliasing is avoided.
10215 To avoid the use of compiler switches, the configuration
10216 pragma @code{No_Strict_Aliasing} with no parameters may be
10217 used to specify that for all access types, the strict
10218 aliasing optimization should be suppressed.
10220 However, these approaches are still overkill, in that they causes
10221 all manipulations of all access values to be deoptimized. A more
10222 refined approach is to concentrate attention on the specific
10223 access type identified as problematic.
10225 First, if a careful analysis of uses of the pointer shows
10226 that there are no possible problematic references, then
10227 the warning can be suppressed by bracketing the
10228 instantiation of @code{Unchecked_Conversion} to turn
10231 @smallexample @c ada
10232 pragma Warnings (Off);
10234 new Unchecked_Conversion (a1, a2);
10235 pragma Warnings (On);
10239 Of course that approach is not appropriate for this particular
10240 example, since indeed there is a problematic reference. In this
10241 case we can take one of two other approaches.
10243 The first possibility is to move the instantiation of unchecked
10244 conversion to the unit in which the type is declared. In
10245 this example, we would move the instantiation of
10246 @code{Unchecked_Conversion} from the body of package
10247 @code{p2} to the spec of package @code{p1}. Now the
10248 warning disappears. That's because any use of the
10249 access type knows there is a suspicious unchecked
10250 conversion, and the strict aliasing optimization
10251 is automatically suppressed for the type.
10253 If it is not practical to move the unchecked conversion to the same unit
10254 in which the destination access type is declared (perhaps because the
10255 source type is not visible in that unit), you may use pragma
10256 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10257 same declarative sequence as the declaration of the access type:
10259 @smallexample @c ada
10260 type a2 is access int2;
10261 pragma No_Strict_Aliasing (a2);
10265 Here again, the compiler now knows that the strict aliasing optimization
10266 should be suppressed for any reference to type @code{a2} and the
10267 expected behavior is obtained.
10269 Finally, note that although the compiler can generate warnings for
10270 simple cases of unchecked conversions, there are tricker and more
10271 indirect ways of creating type incorrect aliases which the compiler
10272 cannot detect. Examples are the use of address overlays and unchecked
10273 conversions involving composite types containing access types as
10274 components. In such cases, no warnings are generated, but there can
10275 still be aliasing problems. One safe coding practice is to forbid the
10276 use of address clauses for type overlaying, and to allow unchecked
10277 conversion only for primitive types. This is not really a significant
10278 restriction since any possible desired effect can be achieved by
10279 unchecked conversion of access values.
10282 @node Coverage Analysis
10283 @subsection Coverage Analysis
10286 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10287 the user to determine the distribution of execution time across a program,
10288 @pxref{Profiling} for details of usage.
10292 @node Text_IO Suggestions
10293 @section @code{Text_IO} Suggestions
10294 @cindex @code{Text_IO} and performance
10297 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10298 the requirement of maintaining page and line counts. If performance
10299 is critical, a recommendation is to use @code{Stream_IO} instead of
10300 @code{Text_IO} for volume output, since this package has less overhead.
10302 If @code{Text_IO} must be used, note that by default output to the standard
10303 output and standard error files is unbuffered (this provides better
10304 behavior when output statements are used for debugging, or if the
10305 progress of a program is observed by tracking the output, e.g. by
10306 using the Unix @command{tail -f} command to watch redirected output.
10308 If you are generating large volumes of output with @code{Text_IO} and
10309 performance is an important factor, use a designated file instead
10310 of the standard output file, or change the standard output file to
10311 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10315 @node Reducing Size of Ada Executables with gnatelim
10316 @section Reducing Size of Ada Executables with @code{gnatelim}
10320 This section describes @command{gnatelim}, a tool which detects unused
10321 subprograms and helps the compiler to create a smaller executable for your
10326 * Running gnatelim::
10327 * Correcting the List of Eliminate Pragmas::
10328 * Making Your Executables Smaller::
10329 * Summary of the gnatelim Usage Cycle::
10332 @node About gnatelim
10333 @subsection About @code{gnatelim}
10336 When a program shares a set of Ada
10337 packages with other programs, it may happen that this program uses
10338 only a fraction of the subprograms defined in these packages. The code
10339 created for these unused subprograms increases the size of the executable.
10341 @code{gnatelim} tracks unused subprograms in an Ada program and
10342 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10343 subprograms that are declared but never called. By placing the list of
10344 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10345 recompiling your program, you may decrease the size of its executable,
10346 because the compiler will not generate the code for 'eliminated' subprograms.
10347 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10348 information about this pragma.
10350 @code{gnatelim} needs as its input data the name of the main subprogram
10351 and a bind file for a main subprogram.
10353 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10354 the main subprogram. @code{gnatelim} can work with both Ada and C
10355 bind files; when both are present, it uses the Ada bind file.
10356 The following commands will build the program and create the bind file:
10359 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10360 $ gnatbind main_prog
10363 Note that @code{gnatelim} needs neither object nor ALI files.
10365 @node Running gnatelim
10366 @subsection Running @code{gnatelim}
10369 @code{gnatelim} has the following command-line interface:
10372 $ gnatelim @ovar{options} name
10376 @code{name} should be a name of a source file that contains the main subprogram
10377 of a program (partition).
10379 @code{gnatelim} has the following switches:
10384 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10385 Quiet mode: by default @code{gnatelim} outputs to the standard error
10386 stream the number of program units left to be processed. This option turns
10389 @item ^-v^/VERBOSE^
10390 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10391 Verbose mode: @code{gnatelim} version information is printed as Ada
10392 comments to the standard output stream. Also, in addition to the number of
10393 program units left @code{gnatelim} will output the name of the current unit
10397 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10398 Also look for subprograms from the GNAT run time that can be eliminated. Note
10399 that when @file{gnat.adc} is produced using this switch, the entire program
10400 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10402 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10403 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10404 When looking for source files also look in directory @var{dir}. Specifying
10405 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10406 sources in the current directory.
10408 @item ^-b^/BIND_FILE=^@var{bind_file}
10409 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10410 Specifies @var{bind_file} as the bind file to process. If not set, the name
10411 of the bind file is computed from the full expanded Ada name
10412 of a main subprogram.
10414 @item ^-C^/CONFIG_FILE=^@var{config_file}
10415 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10416 Specifies a file @var{config_file} that contains configuration pragmas. The
10417 file must be specified with full path.
10419 @item ^--GCC^/COMPILER^=@var{compiler_name}
10420 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10421 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10422 available on the path.
10424 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10425 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10426 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10427 available on the path.
10431 @code{gnatelim} sends its output to the standard output stream, and all the
10432 tracing and debug information is sent to the standard error stream.
10433 In order to produce a proper GNAT configuration file
10434 @file{gnat.adc}, redirection must be used:
10438 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10441 $ gnatelim main_prog.adb > gnat.adc
10450 $ gnatelim main_prog.adb >> gnat.adc
10454 in order to append the @code{gnatelim} output to the existing contents of
10458 @node Correcting the List of Eliminate Pragmas
10459 @subsection Correcting the List of Eliminate Pragmas
10462 In some rare cases @code{gnatelim} may try to eliminate
10463 subprograms that are actually called in the program. In this case, the
10464 compiler will generate an error message of the form:
10467 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10471 You will need to manually remove the wrong @code{Eliminate} pragmas from
10472 the @file{gnat.adc} file. You should recompile your program
10473 from scratch after that, because you need a consistent @file{gnat.adc} file
10474 during the entire compilation.
10476 @node Making Your Executables Smaller
10477 @subsection Making Your Executables Smaller
10480 In order to get a smaller executable for your program you now have to
10481 recompile the program completely with the new @file{gnat.adc} file
10482 created by @code{gnatelim} in your current directory:
10485 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10489 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10490 recompile everything
10491 with the set of pragmas @code{Eliminate} that you have obtained with
10492 @command{gnatelim}).
10494 Be aware that the set of @code{Eliminate} pragmas is specific to each
10495 program. It is not recommended to merge sets of @code{Eliminate}
10496 pragmas created for different programs in one @file{gnat.adc} file.
10498 @node Summary of the gnatelim Usage Cycle
10499 @subsection Summary of the gnatelim Usage Cycle
10502 Here is a quick summary of the steps to be taken in order to reduce
10503 the size of your executables with @code{gnatelim}. You may use
10504 other GNAT options to control the optimization level,
10505 to produce the debugging information, to set search path, etc.
10509 Produce a bind file
10512 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10513 $ gnatbind main_prog
10517 Generate a list of @code{Eliminate} pragmas
10520 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10523 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10528 Recompile the application
10531 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10536 @node Reducing Size of Executables with unused subprogram/data elimination
10537 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10538 @findex unused subprogram/data elimination
10541 This section describes how you can eliminate unused subprograms and data from
10542 your executable just by setting options at compilation time.
10545 * About unused subprogram/data elimination::
10546 * Compilation options::
10547 * Example of unused subprogram/data elimination::
10550 @node About unused subprogram/data elimination
10551 @subsection About unused subprogram/data elimination
10554 By default, an executable contains all code and data of its composing objects
10555 (directly linked or coming from statically linked libraries), even data or code
10556 never used by this executable.
10558 This feature will allow you to eliminate such unused code from your
10559 executable, making it smaller (in disk and in memory).
10561 This functionality is available on all Linux platforms except for the IA-64
10562 architecture and on all cross platforms using the ELF binary file format.
10563 In both cases GNU binutils version 2.16 or later are required to enable it.
10565 @node Compilation options
10566 @subsection Compilation options
10569 The operation of eliminating the unused code and data from the final executable
10570 is directly performed by the linker.
10572 In order to do this, it has to work with objects compiled with the
10574 @option{-ffunction-sections} @option{-fdata-sections}.
10575 @cindex @option{-ffunction-sections} (@command{gcc})
10576 @cindex @option{-fdata-sections} (@command{gcc})
10577 These options are usable with C and Ada files.
10578 They will place respectively each
10579 function or data in a separate section in the resulting object file.
10581 Once the objects and static libraries are created with these options, the
10582 linker can perform the dead code elimination. You can do this by setting
10583 the @option{-Wl,--gc-sections} option to gcc command or in the
10584 @option{-largs} section of @command{gnatmake}. This will perform a
10585 garbage collection of code and data never referenced.
10587 If the linker performs a partial link (@option{-r} ld linker option), then you
10588 will need to provide one or several entry point using the
10589 @option{-e} / @option{--entry} ld option.
10591 Note that objects compiled without the @option{-ffunction-sections} and
10592 @option{-fdata-sections} options can still be linked with the executable.
10593 However, no dead code elimination will be performed on those objects (they will
10596 The GNAT static library is now compiled with -ffunction-sections and
10597 -fdata-sections on some platforms. This allows you to eliminate the unused code
10598 and data of the GNAT library from your executable.
10600 @node Example of unused subprogram/data elimination
10601 @subsection Example of unused subprogram/data elimination
10604 Here is a simple example:
10606 @smallexample @c ada
10615 Used_Data : Integer;
10616 Unused_Data : Integer;
10618 procedure Used (Data : Integer);
10619 procedure Unused (Data : Integer);
10622 package body Aux is
10623 procedure Used (Data : Integer) is
10628 procedure Unused (Data : Integer) is
10630 Unused_Data := Data;
10636 @code{Unused} and @code{Unused_Data} are never referenced in this code
10637 excerpt, and hence they may be safely removed from the final executable.
10642 $ nm test | grep used
10643 020015f0 T aux__unused
10644 02005d88 B aux__unused_data
10645 020015cc T aux__used
10646 02005d84 B aux__used_data
10648 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10649 -largs -Wl,--gc-sections
10651 $ nm test | grep used
10652 02005350 T aux__used
10653 0201ffe0 B aux__used_data
10657 It can be observed that the procedure @code{Unused} and the object
10658 @code{Unused_Data} are removed by the linker when using the
10659 appropriate options.
10661 @c ********************************
10662 @node Renaming Files Using gnatchop
10663 @chapter Renaming Files Using @code{gnatchop}
10667 This chapter discusses how to handle files with multiple units by using
10668 the @code{gnatchop} utility. This utility is also useful in renaming
10669 files to meet the standard GNAT default file naming conventions.
10672 * Handling Files with Multiple Units::
10673 * Operating gnatchop in Compilation Mode::
10674 * Command Line for gnatchop::
10675 * Switches for gnatchop::
10676 * Examples of gnatchop Usage::
10679 @node Handling Files with Multiple Units
10680 @section Handling Files with Multiple Units
10683 The basic compilation model of GNAT requires that a file submitted to the
10684 compiler have only one unit and there be a strict correspondence
10685 between the file name and the unit name.
10687 The @code{gnatchop} utility allows both of these rules to be relaxed,
10688 allowing GNAT to process files which contain multiple compilation units
10689 and files with arbitrary file names. @code{gnatchop}
10690 reads the specified file and generates one or more output files,
10691 containing one unit per file. The unit and the file name correspond,
10692 as required by GNAT.
10694 If you want to permanently restructure a set of ``foreign'' files so that
10695 they match the GNAT rules, and do the remaining development using the
10696 GNAT structure, you can simply use @command{gnatchop} once, generate the
10697 new set of files and work with them from that point on.
10699 Alternatively, if you want to keep your files in the ``foreign'' format,
10700 perhaps to maintain compatibility with some other Ada compilation
10701 system, you can set up a procedure where you use @command{gnatchop} each
10702 time you compile, regarding the source files that it writes as temporary
10703 files that you throw away.
10705 @node Operating gnatchop in Compilation Mode
10706 @section Operating gnatchop in Compilation Mode
10709 The basic function of @code{gnatchop} is to take a file with multiple units
10710 and split it into separate files. The boundary between files is reasonably
10711 clear, except for the issue of comments and pragmas. In default mode, the
10712 rule is that any pragmas between units belong to the previous unit, except
10713 that configuration pragmas always belong to the following unit. Any comments
10714 belong to the following unit. These rules
10715 almost always result in the right choice of
10716 the split point without needing to mark it explicitly and most users will
10717 find this default to be what they want. In this default mode it is incorrect to
10718 submit a file containing only configuration pragmas, or one that ends in
10719 configuration pragmas, to @code{gnatchop}.
10721 However, using a special option to activate ``compilation mode'',
10723 can perform another function, which is to provide exactly the semantics
10724 required by the RM for handling of configuration pragmas in a compilation.
10725 In the absence of configuration pragmas (at the main file level), this
10726 option has no effect, but it causes such configuration pragmas to be handled
10727 in a quite different manner.
10729 First, in compilation mode, if @code{gnatchop} is given a file that consists of
10730 only configuration pragmas, then this file is appended to the
10731 @file{gnat.adc} file in the current directory. This behavior provides
10732 the required behavior described in the RM for the actions to be taken
10733 on submitting such a file to the compiler, namely that these pragmas
10734 should apply to all subsequent compilations in the same compilation
10735 environment. Using GNAT, the current directory, possibly containing a
10736 @file{gnat.adc} file is the representation
10737 of a compilation environment. For more information on the
10738 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
10740 Second, in compilation mode, if @code{gnatchop}
10741 is given a file that starts with
10742 configuration pragmas, and contains one or more units, then these
10743 configuration pragmas are prepended to each of the chopped files. This
10744 behavior provides the required behavior described in the RM for the
10745 actions to be taken on compiling such a file, namely that the pragmas
10746 apply to all units in the compilation, but not to subsequently compiled
10749 Finally, if configuration pragmas appear between units, they are appended
10750 to the previous unit. This results in the previous unit being illegal,
10751 since the compiler does not accept configuration pragmas that follow
10752 a unit. This provides the required RM behavior that forbids configuration
10753 pragmas other than those preceding the first compilation unit of a
10756 For most purposes, @code{gnatchop} will be used in default mode. The
10757 compilation mode described above is used only if you need exactly
10758 accurate behavior with respect to compilations, and you have files
10759 that contain multiple units and configuration pragmas. In this
10760 circumstance the use of @code{gnatchop} with the compilation mode
10761 switch provides the required behavior, and is for example the mode
10762 in which GNAT processes the ACVC tests.
10764 @node Command Line for gnatchop
10765 @section Command Line for @code{gnatchop}
10768 The @code{gnatchop} command has the form:
10771 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
10776 The only required argument is the file name of the file to be chopped.
10777 There are no restrictions on the form of this file name. The file itself
10778 contains one or more Ada units, in normal GNAT format, concatenated
10779 together. As shown, more than one file may be presented to be chopped.
10781 When run in default mode, @code{gnatchop} generates one output file in
10782 the current directory for each unit in each of the files.
10784 @var{directory}, if specified, gives the name of the directory to which
10785 the output files will be written. If it is not specified, all files are
10786 written to the current directory.
10788 For example, given a
10789 file called @file{hellofiles} containing
10791 @smallexample @c ada
10796 with Text_IO; use Text_IO;
10799 Put_Line ("Hello");
10809 $ gnatchop ^hellofiles^HELLOFILES.^
10813 generates two files in the current directory, one called
10814 @file{hello.ads} containing the single line that is the procedure spec,
10815 and the other called @file{hello.adb} containing the remaining text. The
10816 original file is not affected. The generated files can be compiled in
10820 When gnatchop is invoked on a file that is empty or that contains only empty
10821 lines and/or comments, gnatchop will not fail, but will not produce any
10824 For example, given a
10825 file called @file{toto.txt} containing
10827 @smallexample @c ada
10839 $ gnatchop ^toto.txt^TOT.TXT^
10843 will not produce any new file and will result in the following warnings:
10846 toto.txt:1:01: warning: empty file, contains no compilation units
10847 no compilation units found
10848 no source files written
10851 @node Switches for gnatchop
10852 @section Switches for @code{gnatchop}
10855 @command{gnatchop} recognizes the following switches:
10861 @cindex @option{--version} @command{gnatchop}
10862 Display Copyright and version, then exit disregarding all other options.
10865 @cindex @option{--help} @command{gnatchop}
10866 If @option{--version} was not used, display usage, then exit disregarding
10869 @item ^-c^/COMPILATION^
10870 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
10871 Causes @code{gnatchop} to operate in compilation mode, in which
10872 configuration pragmas are handled according to strict RM rules. See
10873 previous section for a full description of this mode.
10876 @item -gnat@var{xxx}
10877 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
10878 used to parse the given file. Not all @var{xxx} options make sense,
10879 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
10880 process a source file that uses Latin-2 coding for identifiers.
10884 Causes @code{gnatchop} to generate a brief help summary to the standard
10885 output file showing usage information.
10887 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
10888 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
10889 Limit generated file names to the specified number @code{mm}
10891 This is useful if the
10892 resulting set of files is required to be interoperable with systems
10893 which limit the length of file names.
10895 If no value is given, or
10896 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
10897 a default of 39, suitable for OpenVMS Alpha
10898 Systems, is assumed
10901 No space is allowed between the @option{-k} and the numeric value. The numeric
10902 value may be omitted in which case a default of @option{-k8},
10904 with DOS-like file systems, is used. If no @option{-k} switch
10906 there is no limit on the length of file names.
10909 @item ^-p^/PRESERVE^
10910 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
10911 Causes the file ^modification^creation^ time stamp of the input file to be
10912 preserved and used for the time stamp of the output file(s). This may be
10913 useful for preserving coherency of time stamps in an environment where
10914 @code{gnatchop} is used as part of a standard build process.
10917 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
10918 Causes output of informational messages indicating the set of generated
10919 files to be suppressed. Warnings and error messages are unaffected.
10921 @item ^-r^/REFERENCE^
10922 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
10923 @findex Source_Reference
10924 Generate @code{Source_Reference} pragmas. Use this switch if the output
10925 files are regarded as temporary and development is to be done in terms
10926 of the original unchopped file. This switch causes
10927 @code{Source_Reference} pragmas to be inserted into each of the
10928 generated files to refers back to the original file name and line number.
10929 The result is that all error messages refer back to the original
10931 In addition, the debugging information placed into the object file (when
10932 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
10934 also refers back to this original file so that tools like profilers and
10935 debuggers will give information in terms of the original unchopped file.
10937 If the original file to be chopped itself contains
10938 a @code{Source_Reference}
10939 pragma referencing a third file, then gnatchop respects
10940 this pragma, and the generated @code{Source_Reference} pragmas
10941 in the chopped file refer to the original file, with appropriate
10942 line numbers. This is particularly useful when @code{gnatchop}
10943 is used in conjunction with @code{gnatprep} to compile files that
10944 contain preprocessing statements and multiple units.
10946 @item ^-v^/VERBOSE^
10947 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
10948 Causes @code{gnatchop} to operate in verbose mode. The version
10949 number and copyright notice are output, as well as exact copies of
10950 the gnat1 commands spawned to obtain the chop control information.
10952 @item ^-w^/OVERWRITE^
10953 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
10954 Overwrite existing file names. Normally @code{gnatchop} regards it as a
10955 fatal error if there is already a file with the same name as a
10956 file it would otherwise output, in other words if the files to be
10957 chopped contain duplicated units. This switch bypasses this
10958 check, and causes all but the last instance of such duplicated
10959 units to be skipped.
10962 @item --GCC=@var{xxxx}
10963 @cindex @option{--GCC=} (@code{gnatchop})
10964 Specify the path of the GNAT parser to be used. When this switch is used,
10965 no attempt is made to add the prefix to the GNAT parser executable.
10969 @node Examples of gnatchop Usage
10970 @section Examples of @code{gnatchop} Usage
10974 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
10977 @item gnatchop -w hello_s.ada prerelease/files
10980 Chops the source file @file{hello_s.ada}. The output files will be
10981 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
10983 files with matching names in that directory (no files in the current
10984 directory are modified).
10986 @item gnatchop ^archive^ARCHIVE.^
10987 Chops the source file @file{^archive^ARCHIVE.^}
10988 into the current directory. One
10989 useful application of @code{gnatchop} is in sending sets of sources
10990 around, for example in email messages. The required sources are simply
10991 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
10993 @command{gnatchop} is used at the other end to reconstitute the original
10996 @item gnatchop file1 file2 file3 direc
10997 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
10998 the resulting files in the directory @file{direc}. Note that if any units
10999 occur more than once anywhere within this set of files, an error message
11000 is generated, and no files are written. To override this check, use the
11001 @option{^-w^/OVERWRITE^} switch,
11002 in which case the last occurrence in the last file will
11003 be the one that is output, and earlier duplicate occurrences for a given
11004 unit will be skipped.
11007 @node Configuration Pragmas
11008 @chapter Configuration Pragmas
11009 @cindex Configuration pragmas
11010 @cindex Pragmas, configuration
11013 Configuration pragmas include those pragmas described as
11014 such in the Ada Reference Manual, as well as
11015 implementation-dependent pragmas that are configuration pragmas.
11016 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11017 for details on these additional GNAT-specific configuration pragmas.
11018 Most notably, the pragma @code{Source_File_Name}, which allows
11019 specifying non-default names for source files, is a configuration
11020 pragma. The following is a complete list of configuration pragmas
11021 recognized by GNAT:
11033 Compile_Time_Warning
11035 Component_Alignment
11042 External_Name_Casing
11045 Float_Representation
11058 Priority_Specific_Dispatching
11061 Propagate_Exceptions
11064 Restricted_Run_Time
11066 Restrictions_Warnings
11069 Source_File_Name_Project
11072 Suppress_Exception_Locations
11073 Task_Dispatching_Policy
11079 Wide_Character_Encoding
11084 * Handling of Configuration Pragmas::
11085 * The Configuration Pragmas Files::
11088 @node Handling of Configuration Pragmas
11089 @section Handling of Configuration Pragmas
11091 Configuration pragmas may either appear at the start of a compilation
11092 unit, in which case they apply only to that unit, or they may apply to
11093 all compilations performed in a given compilation environment.
11095 GNAT also provides the @code{gnatchop} utility to provide an automatic
11096 way to handle configuration pragmas following the semantics for
11097 compilations (that is, files with multiple units), described in the RM.
11098 See @ref{Operating gnatchop in Compilation Mode} for details.
11099 However, for most purposes, it will be more convenient to edit the
11100 @file{gnat.adc} file that contains configuration pragmas directly,
11101 as described in the following section.
11103 @node The Configuration Pragmas Files
11104 @section The Configuration Pragmas Files
11105 @cindex @file{gnat.adc}
11108 In GNAT a compilation environment is defined by the current
11109 directory at the time that a compile command is given. This current
11110 directory is searched for a file whose name is @file{gnat.adc}. If
11111 this file is present, it is expected to contain one or more
11112 configuration pragmas that will be applied to the current compilation.
11113 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11116 Configuration pragmas may be entered into the @file{gnat.adc} file
11117 either by running @code{gnatchop} on a source file that consists only of
11118 configuration pragmas, or more conveniently by
11119 direct editing of the @file{gnat.adc} file, which is a standard format
11122 In addition to @file{gnat.adc}, additional files containing configuration
11123 pragmas may be applied to the current compilation using the switch
11124 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11125 contains only configuration pragmas. These configuration pragmas are
11126 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11127 is present and switch @option{-gnatA} is not used).
11129 It is allowed to specify several switches @option{-gnatec}, all of which
11130 will be taken into account.
11132 If you are using project file, a separate mechanism is provided using
11133 project attributes, see @ref{Specifying Configuration Pragmas} for more
11137 Of special interest to GNAT OpenVMS Alpha is the following
11138 configuration pragma:
11140 @smallexample @c ada
11142 pragma Extend_System (Aux_DEC);
11147 In the presence of this pragma, GNAT adds to the definition of the
11148 predefined package SYSTEM all the additional types and subprograms that are
11149 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11152 @node Handling Arbitrary File Naming Conventions Using gnatname
11153 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11154 @cindex Arbitrary File Naming Conventions
11157 * Arbitrary File Naming Conventions::
11158 * Running gnatname::
11159 * Switches for gnatname::
11160 * Examples of gnatname Usage::
11163 @node Arbitrary File Naming Conventions
11164 @section Arbitrary File Naming Conventions
11167 The GNAT compiler must be able to know the source file name of a compilation
11168 unit. When using the standard GNAT default file naming conventions
11169 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11170 does not need additional information.
11173 When the source file names do not follow the standard GNAT default file naming
11174 conventions, the GNAT compiler must be given additional information through
11175 a configuration pragmas file (@pxref{Configuration Pragmas})
11177 When the non-standard file naming conventions are well-defined,
11178 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11179 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11180 if the file naming conventions are irregular or arbitrary, a number
11181 of pragma @code{Source_File_Name} for individual compilation units
11183 To help maintain the correspondence between compilation unit names and
11184 source file names within the compiler,
11185 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11188 @node Running gnatname
11189 @section Running @code{gnatname}
11192 The usual form of the @code{gnatname} command is
11195 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11196 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11200 All of the arguments are optional. If invoked without any argument,
11201 @code{gnatname} will display its usage.
11204 When used with at least one naming pattern, @code{gnatname} will attempt to
11205 find all the compilation units in files that follow at least one of the
11206 naming patterns. To find these compilation units,
11207 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11211 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11212 Each Naming Pattern is enclosed between double quotes.
11213 A Naming Pattern is a regular expression similar to the wildcard patterns
11214 used in file names by the Unix shells or the DOS prompt.
11217 @code{gnatname} may be called with several sections of directories/patterns.
11218 Sections are separated by switch @code{--and}. In each section, there must be
11219 at least one pattern. If no directory is specified in a section, the current
11220 directory (or the project directory is @code{-P} is used) is implied.
11221 The options other that the directory switches and the patterns apply globally
11222 even if they are in different sections.
11225 Examples of Naming Patterns are
11234 For a more complete description of the syntax of Naming Patterns,
11235 see the second kind of regular expressions described in @file{g-regexp.ads}
11236 (the ``Glob'' regular expressions).
11239 When invoked with no switch @code{-P}, @code{gnatname} will create a
11240 configuration pragmas file @file{gnat.adc} in the current working directory,
11241 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11244 @node Switches for gnatname
11245 @section Switches for @code{gnatname}
11248 Switches for @code{gnatname} must precede any specified Naming Pattern.
11251 You may specify any of the following switches to @code{gnatname}:
11257 @cindex @option{--version} @command{gnatname}
11258 Display Copyright and version, then exit disregarding all other options.
11261 @cindex @option{--help} @command{gnatname}
11262 If @option{--version} was not used, display usage, then exit disregarding
11266 Start another section of directories/patterns.
11268 @item ^-c^/CONFIG_FILE=^@file{file}
11269 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11270 Create a configuration pragmas file @file{file} (instead of the default
11273 There may be zero, one or more space between @option{-c} and
11276 @file{file} may include directory information. @file{file} must be
11277 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11278 When a switch @option{^-c^/CONFIG_FILE^} is
11279 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11281 @item ^-d^/SOURCE_DIRS=^@file{dir}
11282 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11283 Look for source files in directory @file{dir}. There may be zero, one or more
11284 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11285 When a switch @option{^-d^/SOURCE_DIRS^}
11286 is specified, the current working directory will not be searched for source
11287 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11288 or @option{^-D^/DIR_FILES^} switch.
11289 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11290 If @file{dir} is a relative path, it is relative to the directory of
11291 the configuration pragmas file specified with switch
11292 @option{^-c^/CONFIG_FILE^},
11293 or to the directory of the project file specified with switch
11294 @option{^-P^/PROJECT_FILE^} or,
11295 if neither switch @option{^-c^/CONFIG_FILE^}
11296 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11297 current working directory. The directory
11298 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11300 @item ^-D^/DIRS_FILE=^@file{file}
11301 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11302 Look for source files in all directories listed in text file @file{file}.
11303 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11305 @file{file} must be an existing, readable text file.
11306 Each nonempty line in @file{file} must be a directory.
11307 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11308 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11311 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11312 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11313 Foreign patterns. Using this switch, it is possible to add sources of languages
11314 other than Ada to the list of sources of a project file.
11315 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11318 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11321 will look for Ada units in all files with the @file{.ada} extension,
11322 and will add to the list of file for project @file{prj.gpr} the C files
11323 with extension @file{.^c^C^}.
11326 @cindex @option{^-h^/HELP^} (@code{gnatname})
11327 Output usage (help) information. The output is written to @file{stdout}.
11329 @item ^-P^/PROJECT_FILE=^@file{proj}
11330 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11331 Create or update project file @file{proj}. There may be zero, one or more space
11332 between @option{-P} and @file{proj}. @file{proj} may include directory
11333 information. @file{proj} must be writable.
11334 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11335 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11336 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11338 @item ^-v^/VERBOSE^
11339 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11340 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11341 This includes name of the file written, the name of the directories to search
11342 and, for each file in those directories whose name matches at least one of
11343 the Naming Patterns, an indication of whether the file contains a unit,
11344 and if so the name of the unit.
11346 @item ^-v -v^/VERBOSE /VERBOSE^
11347 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11348 Very Verbose mode. In addition to the output produced in verbose mode,
11349 for each file in the searched directories whose name matches none of
11350 the Naming Patterns, an indication is given that there is no match.
11352 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11353 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11354 Excluded patterns. Using this switch, it is possible to exclude some files
11355 that would match the name patterns. For example,
11357 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11360 will look for Ada units in all files with the @file{.ada} extension,
11361 except those whose names end with @file{_nt.ada}.
11365 @node Examples of gnatname Usage
11366 @section Examples of @code{gnatname} Usage
11370 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11376 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11381 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11382 and be writable. In addition, the directory
11383 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11384 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11387 Note the optional spaces after @option{-c} and @option{-d}.
11392 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11393 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11396 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11397 /EXCLUDED_PATTERN=*_nt_body.ada
11398 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11399 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11403 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11404 even in conjunction with one or several switches
11405 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11406 are used in this example.
11408 @c *****************************************
11409 @c * G N A T P r o j e c t M a n a g e r *
11410 @c *****************************************
11411 @node GNAT Project Manager
11412 @chapter GNAT Project Manager
11416 * Examples of Project Files::
11417 * Project File Syntax::
11418 * Objects and Sources in Project Files::
11419 * Importing Projects::
11420 * Project Extension::
11421 * Project Hierarchy Extension::
11422 * External References in Project Files::
11423 * Packages in Project Files::
11424 * Variables from Imported Projects::
11426 * Library Projects::
11427 * Stand-alone Library Projects::
11428 * Switches Related to Project Files::
11429 * Tools Supporting Project Files::
11430 * An Extended Example::
11431 * Project File Complete Syntax::
11434 @c ****************
11435 @c * Introduction *
11436 @c ****************
11439 @section Introduction
11442 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11443 you to manage complex builds involving a number of source files, directories,
11444 and compilation options for different system configurations. In particular,
11445 project files allow you to specify:
11448 The directory or set of directories containing the source files, and/or the
11449 names of the specific source files themselves
11451 The directory in which the compiler's output
11452 (@file{ALI} files, object files, tree files) is to be placed
11454 The directory in which the executable programs is to be placed
11456 ^Switch^Switch^ settings for any of the project-enabled tools
11457 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11458 @code{gnatfind}); you can apply these settings either globally or to individual
11461 The source files containing the main subprogram(s) to be built
11463 The source programming language(s) (currently Ada and/or C)
11465 Source file naming conventions; you can specify these either globally or for
11466 individual compilation units
11473 @node Project Files
11474 @subsection Project Files
11477 Project files are written in a syntax close to that of Ada, using familiar
11478 notions such as packages, context clauses, declarations, default values,
11479 assignments, and inheritance. Finally, project files can be built
11480 hierarchically from other project files, simplifying complex system
11481 integration and project reuse.
11483 A @dfn{project} is a specific set of values for various compilation properties.
11484 The settings for a given project are described by means of
11485 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11486 Property values in project files are either strings or lists of strings.
11487 Properties that are not explicitly set receive default values. A project
11488 file may interrogate the values of @dfn{external variables} (user-defined
11489 command-line switches or environment variables), and it may specify property
11490 settings conditionally, based on the value of such variables.
11492 In simple cases, a project's source files depend only on other source files
11493 in the same project, or on the predefined libraries. (@emph{Dependence} is
11495 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11496 the Project Manager also allows more sophisticated arrangements,
11497 where the source files in one project depend on source files in other
11501 One project can @emph{import} other projects containing needed source files.
11503 You can organize GNAT projects in a hierarchy: a @emph{child} project
11504 can extend a @emph{parent} project, inheriting the parent's source files and
11505 optionally overriding any of them with alternative versions
11509 More generally, the Project Manager lets you structure large development
11510 efforts into hierarchical subsystems, where build decisions are delegated
11511 to the subsystem level, and thus different compilation environments
11512 (^switch^switch^ settings) used for different subsystems.
11514 The Project Manager is invoked through the
11515 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11516 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11518 There may be zero, one or more spaces between @option{-P} and
11519 @option{@emph{projectfile}}.
11521 If you want to define (on the command line) an external variable that is
11522 queried by the project file, you must use the
11523 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11524 The Project Manager parses and interprets the project file, and drives the
11525 invoked tool based on the project settings.
11527 The Project Manager supports a wide range of development strategies,
11528 for systems of all sizes. Here are some typical practices that are
11532 Using a common set of source files, but generating object files in different
11533 directories via different ^switch^switch^ settings
11535 Using a mostly-shared set of source files, but with different versions of
11540 The destination of an executable can be controlled inside a project file
11541 using the @option{^-o^-o^}
11543 In the absence of such a ^switch^switch^ either inside
11544 the project file or on the command line, any executable files generated by
11545 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11546 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11547 in the object directory of the project.
11549 You can use project files to achieve some of the effects of a source
11550 versioning system (for example, defining separate projects for
11551 the different sets of sources that comprise different releases) but the
11552 Project Manager is independent of any source configuration management tools
11553 that might be used by the developers.
11555 The next section introduces the main features of GNAT's project facility
11556 through a sequence of examples; subsequent sections will present the syntax
11557 and semantics in more detail. A more formal description of the project
11558 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11561 @c *****************************
11562 @c * Examples of Project Files *
11563 @c *****************************
11565 @node Examples of Project Files
11566 @section Examples of Project Files
11568 This section illustrates some of the typical uses of project files and
11569 explains their basic structure and behavior.
11572 * Common Sources with Different ^Switches^Switches^ and Directories::
11573 * Using External Variables::
11574 * Importing Other Projects::
11575 * Extending a Project::
11578 @node Common Sources with Different ^Switches^Switches^ and Directories
11579 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11583 * Specifying the Object Directory::
11584 * Specifying the Exec Directory::
11585 * Project File Packages::
11586 * Specifying ^Switch^Switch^ Settings::
11587 * Main Subprograms::
11588 * Executable File Names::
11589 * Source File Naming Conventions::
11590 * Source Language(s)::
11594 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11595 @file{proc.adb} are in the @file{/common} directory. The file
11596 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11597 package @code{Pack}. We want to compile these source files under two sets
11598 of ^switches^switches^:
11601 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11602 and the @option{^-gnata^-gnata^},
11603 @option{^-gnato^-gnato^},
11604 and @option{^-gnatE^-gnatE^} switches to the
11605 compiler; the compiler's output is to appear in @file{/common/debug}
11607 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11608 to the compiler; the compiler's output is to appear in @file{/common/release}
11612 The GNAT project files shown below, respectively @file{debug.gpr} and
11613 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11626 ^/common/debug^[COMMON.DEBUG]^
11631 ^/common/release^[COMMON.RELEASE]^
11636 Here are the corresponding project files:
11638 @smallexample @c projectfile
11641 for Object_Dir use "debug";
11642 for Main use ("proc");
11645 for ^Default_Switches^Default_Switches^ ("Ada")
11647 for Executable ("proc.adb") use "proc1";
11652 package Compiler is
11653 for ^Default_Switches^Default_Switches^ ("Ada")
11654 use ("-fstack-check",
11657 "^-gnatE^-gnatE^");
11663 @smallexample @c projectfile
11666 for Object_Dir use "release";
11667 for Exec_Dir use ".";
11668 for Main use ("proc");
11670 package Compiler is
11671 for ^Default_Switches^Default_Switches^ ("Ada")
11679 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11680 insensitive), and analogously the project defined by @file{release.gpr} is
11681 @code{"Release"}. For consistency the file should have the same name as the
11682 project, and the project file's extension should be @code{"gpr"}. These
11683 conventions are not required, but a warning is issued if they are not followed.
11685 If the current directory is @file{^/temp^[TEMP]^}, then the command
11687 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
11691 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
11692 as well as the @code{^proc1^PROC1.EXE^} executable,
11693 using the ^switch^switch^ settings defined in the project file.
11695 Likewise, the command
11697 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
11701 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
11702 and the @code{^proc^PROC.EXE^}
11703 executable in @file{^/common^[COMMON]^},
11704 using the ^switch^switch^ settings from the project file.
11707 @unnumberedsubsubsec Source Files
11710 If a project file does not explicitly specify a set of source directories or
11711 a set of source files, then by default the project's source files are the
11712 Ada source files in the project file directory. Thus @file{pack.ads},
11713 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
11715 @node Specifying the Object Directory
11716 @unnumberedsubsubsec Specifying the Object Directory
11719 Several project properties are modeled by Ada-style @emph{attributes};
11720 a property is defined by supplying the equivalent of an Ada attribute
11721 definition clause in the project file.
11722 A project's object directory is another such a property; the corresponding
11723 attribute is @code{Object_Dir}, and its value is also a string expression,
11724 specified either as absolute or relative. In the later case,
11725 it is relative to the project file directory. Thus the compiler's
11726 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
11727 (for the @code{Debug} project)
11728 and to @file{^/common/release^[COMMON.RELEASE]^}
11729 (for the @code{Release} project).
11730 If @code{Object_Dir} is not specified, then the default is the project file
11733 @node Specifying the Exec Directory
11734 @unnumberedsubsubsec Specifying the Exec Directory
11737 A project's exec directory is another property; the corresponding
11738 attribute is @code{Exec_Dir}, and its value is also a string expression,
11739 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
11740 then the default is the object directory (which may also be the project file
11741 directory if attribute @code{Object_Dir} is not specified). Thus the executable
11742 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
11743 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
11744 and in @file{^/common^[COMMON]^} for the @code{Release} project.
11746 @node Project File Packages
11747 @unnumberedsubsubsec Project File Packages
11750 A GNAT tool that is integrated with the Project Manager is modeled by a
11751 corresponding package in the project file. In the example above,
11752 The @code{Debug} project defines the packages @code{Builder}
11753 (for @command{gnatmake}) and @code{Compiler};
11754 the @code{Release} project defines only the @code{Compiler} package.
11756 The Ada-like package syntax is not to be taken literally. Although packages in
11757 project files bear a surface resemblance to packages in Ada source code, the
11758 notation is simply a way to convey a grouping of properties for a named
11759 entity. Indeed, the package names permitted in project files are restricted
11760 to a predefined set, corresponding to the project-aware tools, and the contents
11761 of packages are limited to a small set of constructs.
11762 The packages in the example above contain attribute definitions.
11764 @node Specifying ^Switch^Switch^ Settings
11765 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
11768 ^Switch^Switch^ settings for a project-aware tool can be specified through
11769 attributes in the package that corresponds to the tool.
11770 The example above illustrates one of the relevant attributes,
11771 @code{^Default_Switches^Default_Switches^}, which is defined in packages
11772 in both project files.
11773 Unlike simple attributes like @code{Source_Dirs},
11774 @code{^Default_Switches^Default_Switches^} is
11775 known as an @emph{associative array}. When you define this attribute, you must
11776 supply an ``index'' (a literal string), and the effect of the attribute
11777 definition is to set the value of the array at the specified index.
11778 For the @code{^Default_Switches^Default_Switches^} attribute,
11779 the index is a programming language (in our case, Ada),
11780 and the value specified (after @code{use}) must be a list
11781 of string expressions.
11783 The attributes permitted in project files are restricted to a predefined set.
11784 Some may appear at project level, others in packages.
11785 For any attribute that is an associative array, the index must always be a
11786 literal string, but the restrictions on this string (e.g., a file name or a
11787 language name) depend on the individual attribute.
11788 Also depending on the attribute, its specified value will need to be either a
11789 string or a string list.
11791 In the @code{Debug} project, we set the switches for two tools,
11792 @command{gnatmake} and the compiler, and thus we include the two corresponding
11793 packages; each package defines the @code{^Default_Switches^Default_Switches^}
11794 attribute with index @code{"Ada"}.
11795 Note that the package corresponding to
11796 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
11797 similar, but only includes the @code{Compiler} package.
11799 In project @code{Debug} above, the ^switches^switches^ starting with
11800 @option{-gnat} that are specified in package @code{Compiler}
11801 could have been placed in package @code{Builder}, since @command{gnatmake}
11802 transmits all such ^switches^switches^ to the compiler.
11804 @node Main Subprograms
11805 @unnumberedsubsubsec Main Subprograms
11808 One of the specifiable properties of a project is a list of files that contain
11809 main subprograms. This property is captured in the @code{Main} attribute,
11810 whose value is a list of strings. If a project defines the @code{Main}
11811 attribute, it is not necessary to identify the main subprogram(s) when
11812 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
11814 @node Executable File Names
11815 @unnumberedsubsubsec Executable File Names
11818 By default, the executable file name corresponding to a main source is
11819 deduced from the main source file name. Through the attributes
11820 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
11821 it is possible to change this default.
11822 In project @code{Debug} above, the executable file name
11823 for main source @file{^proc.adb^PROC.ADB^} is
11824 @file{^proc1^PROC1.EXE^}.
11825 Attribute @code{Executable_Suffix}, when specified, may change the suffix
11826 of the executable files, when no attribute @code{Executable} applies:
11827 its value replace the platform-specific executable suffix.
11828 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
11829 specify a non-default executable file name when several mains are built at once
11830 in a single @command{gnatmake} command.
11832 @node Source File Naming Conventions
11833 @unnumberedsubsubsec Source File Naming Conventions
11836 Since the project files above do not specify any source file naming
11837 conventions, the GNAT defaults are used. The mechanism for defining source
11838 file naming conventions -- a package named @code{Naming} --
11839 is described below (@pxref{Naming Schemes}).
11841 @node Source Language(s)
11842 @unnumberedsubsubsec Source Language(s)
11845 Since the project files do not specify a @code{Languages} attribute, by
11846 default the GNAT tools assume that the language of the project file is Ada.
11847 More generally, a project can comprise source files
11848 in Ada, C, and/or other languages.
11850 @node Using External Variables
11851 @subsection Using External Variables
11854 Instead of supplying different project files for debug and release, we can
11855 define a single project file that queries an external variable (set either
11856 on the command line or via an ^environment variable^logical name^) in order to
11857 conditionally define the appropriate settings. Again, assume that the
11858 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
11859 located in directory @file{^/common^[COMMON]^}. The following project file,
11860 @file{build.gpr}, queries the external variable named @code{STYLE} and
11861 defines an object directory and ^switch^switch^ settings based on whether
11862 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
11863 the default is @code{"deb"}.
11865 @smallexample @c projectfile
11868 for Main use ("proc");
11870 type Style_Type is ("deb", "rel");
11871 Style : Style_Type := external ("STYLE", "deb");
11875 for Object_Dir use "debug";
11878 for Object_Dir use "release";
11879 for Exec_Dir use ".";
11888 for ^Default_Switches^Default_Switches^ ("Ada")
11890 for Executable ("proc") use "proc1";
11899 package Compiler is
11903 for ^Default_Switches^Default_Switches^ ("Ada")
11904 use ("^-gnata^-gnata^",
11906 "^-gnatE^-gnatE^");
11909 for ^Default_Switches^Default_Switches^ ("Ada")
11920 @code{Style_Type} is an example of a @emph{string type}, which is the project
11921 file analog of an Ada enumeration type but whose components are string literals
11922 rather than identifiers. @code{Style} is declared as a variable of this type.
11924 The form @code{external("STYLE", "deb")} is known as an
11925 @emph{external reference}; its first argument is the name of an
11926 @emph{external variable}, and the second argument is a default value to be
11927 used if the external variable doesn't exist. You can define an external
11928 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
11929 or you can use ^an environment variable^a logical name^
11930 as an external variable.
11932 Each @code{case} construct is expanded by the Project Manager based on the
11933 value of @code{Style}. Thus the command
11936 gnatmake -P/common/build.gpr -XSTYLE=deb
11942 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
11947 is equivalent to the @command{gnatmake} invocation using the project file
11948 @file{debug.gpr} in the earlier example. So is the command
11950 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
11954 since @code{"deb"} is the default for @code{STYLE}.
11960 gnatmake -P/common/build.gpr -XSTYLE=rel
11966 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
11971 is equivalent to the @command{gnatmake} invocation using the project file
11972 @file{release.gpr} in the earlier example.
11974 @node Importing Other Projects
11975 @subsection Importing Other Projects
11976 @cindex @code{ADA_PROJECT_PATH}
11979 A compilation unit in a source file in one project may depend on compilation
11980 units in source files in other projects. To compile this unit under
11981 control of a project file, the
11982 dependent project must @emph{import} the projects containing the needed source
11984 This effect is obtained using syntax similar to an Ada @code{with} clause,
11985 but where @code{with}ed entities are strings that denote project files.
11987 As an example, suppose that the two projects @code{GUI_Proj} and
11988 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
11989 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
11990 and @file{^/comm^[COMM]^}, respectively.
11991 Suppose that the source files for @code{GUI_Proj} are
11992 @file{gui.ads} and @file{gui.adb}, and that the source files for
11993 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
11994 files is located in its respective project file directory. Schematically:
12013 We want to develop an application in directory @file{^/app^[APP]^} that
12014 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12015 the corresponding project files (e.g.@: the ^switch^switch^ settings
12016 and object directory).
12017 Skeletal code for a main procedure might be something like the following:
12019 @smallexample @c ada
12022 procedure App_Main is
12031 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12034 @smallexample @c projectfile
12036 with "/gui/gui_proj", "/comm/comm_proj";
12037 project App_Proj is
12038 for Main use ("app_main");
12044 Building an executable is achieved through the command:
12046 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12049 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12050 in the directory where @file{app_proj.gpr} resides.
12052 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12053 (as illustrated above) the @code{with} clause can omit the extension.
12055 Our example specified an absolute path for each imported project file.
12056 Alternatively, the directory name of an imported object can be omitted
12060 The imported project file is in the same directory as the importing project
12063 You have defined ^an environment variable^a logical name^
12064 that includes the directory containing
12065 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
12066 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12067 directory names separated by colons (semicolons on Windows).
12071 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
12072 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12075 @smallexample @c projectfile
12077 with "gui_proj", "comm_proj";
12078 project App_Proj is
12079 for Main use ("app_main");
12085 Importing other projects can create ambiguities.
12086 For example, the same unit might be present in different imported projects, or
12087 it might be present in both the importing project and in an imported project.
12088 Both of these conditions are errors. Note that in the current version of
12089 the Project Manager, it is illegal to have an ambiguous unit even if the
12090 unit is never referenced by the importing project. This restriction may be
12091 relaxed in a future release.
12093 @node Extending a Project
12094 @subsection Extending a Project
12097 In large software systems it is common to have multiple
12098 implementations of a common interface; in Ada terms, multiple versions of a
12099 package body for the same spec. For example, one implementation
12100 might be safe for use in tasking programs, while another might only be used
12101 in sequential applications. This can be modeled in GNAT using the concept
12102 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12103 another project (the ``parent'') then by default all source files of the
12104 parent project are inherited by the child, but the child project can
12105 override any of the parent's source files with new versions, and can also
12106 add new files. This facility is the project analog of a type extension in
12107 Object-Oriented Programming. Project hierarchies are permitted (a child
12108 project may be the parent of yet another project), and a project that
12109 inherits one project can also import other projects.
12111 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12112 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12113 @file{pack.adb}, and @file{proc.adb}:
12126 Note that the project file can simply be empty (that is, no attribute or
12127 package is defined):
12129 @smallexample @c projectfile
12131 project Seq_Proj is
12137 implying that its source files are all the Ada source files in the project
12140 Suppose we want to supply an alternate version of @file{pack.adb}, in
12141 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12142 @file{pack.ads} and @file{proc.adb}. We can define a project
12143 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12147 ^/tasking^[TASKING]^
12153 project Tasking_Proj extends "/seq/seq_proj" is
12159 The version of @file{pack.adb} used in a build depends on which project file
12162 Note that we could have obtained the desired behavior using project import
12163 rather than project inheritance; a @code{base} project would contain the
12164 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12165 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12166 would import @code{base} and add a different version of @file{pack.adb}. The
12167 choice depends on whether other sources in the original project need to be
12168 overridden. If they do, then project extension is necessary, otherwise,
12169 importing is sufficient.
12172 In a project file that extends another project file, it is possible to
12173 indicate that an inherited source is not part of the sources of the extending
12174 project. This is necessary sometimes when a package spec has been overloaded
12175 and no longer requires a body: in this case, it is necessary to indicate that
12176 the inherited body is not part of the sources of the project, otherwise there
12177 will be a compilation error when compiling the spec.
12179 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12180 Its value is a string list: a list of file names. It is also possible to use
12181 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12182 the file name of a text file containing a list of file names, one per line.
12184 @smallexample @c @projectfile
12185 project B extends "a" is
12186 for Source_Files use ("pkg.ads");
12187 -- New spec of Pkg does not need a completion
12188 for Excluded_Source_Files use ("pkg.adb");
12192 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12193 is still needed: if it is possible to build using @command{gnatmake} when such
12194 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12195 it is possible to remove the source completely from a system that includes
12198 @c ***********************
12199 @c * Project File Syntax *
12200 @c ***********************
12202 @node Project File Syntax
12203 @section Project File Syntax
12207 * Qualified Projects::
12213 * Associative Array Attributes::
12214 * case Constructions::
12218 This section describes the structure of project files.
12220 A project may be an @emph{independent project}, entirely defined by a single
12221 project file. Any Ada source file in an independent project depends only
12222 on the predefined library and other Ada source files in the same project.
12225 A project may also @dfn{depend on} other projects, in either or both of
12226 the following ways:
12228 @item It may import any number of projects
12229 @item It may extend at most one other project
12233 The dependence relation is a directed acyclic graph (the subgraph reflecting
12234 the ``extends'' relation is a tree).
12236 A project's @dfn{immediate sources} are the source files directly defined by
12237 that project, either implicitly by residing in the project file's directory,
12238 or explicitly through any of the source-related attributes described below.
12239 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12240 of @var{proj} together with the immediate sources (unless overridden) of any
12241 project on which @var{proj} depends (either directly or indirectly).
12244 @subsection Basic Syntax
12247 As seen in the earlier examples, project files have an Ada-like syntax.
12248 The minimal project file is:
12249 @smallexample @c projectfile
12258 The identifier @code{Empty} is the name of the project.
12259 This project name must be present after the reserved
12260 word @code{end} at the end of the project file, followed by a semi-colon.
12262 Any name in a project file, such as the project name or a variable name,
12263 has the same syntax as an Ada identifier.
12265 The reserved words of project files are the Ada 95 reserved words plus
12266 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12267 reserved words currently used in project file syntax are:
12303 Comments in project files have the same syntax as in Ada, two consecutive
12304 hyphens through the end of the line.
12306 @node Qualified Projects
12307 @subsection Qualified Projects
12310 Before the reserved @code{project}, there may be one or two "qualifiers", that
12311 is identifiers or other reserved words, to qualify the project.
12313 The current list of qualifiers is:
12317 @code{abstract}: qualify a project with no sources. An abstract project must
12318 have a declaration specifying that there are no sources in the project, and,
12319 if it extends another project, the project it extends must also be a qualified
12323 @code{standard}: a standard project is a non library project with sources.
12326 @code{aggregate}: for future extension
12329 @code{aggregate library}: for future extension
12332 @code{library}: a library project must declare both attributes
12333 @code{Library_Name} and @code{Library_Dir}.
12336 @code{configuration}: a configuration project cannot be in a project tree.
12340 @subsection Packages
12343 A project file may contain @emph{packages}. The name of a package must be one
12344 of the identifiers from the following list. A package
12345 with a given name may only appear once in a project file. Package names are
12346 case insensitive. The following package names are legal:
12362 @code{Cross_Reference}
12366 @code{Pretty_Printer}
12376 @code{Language_Processing}
12380 In its simplest form, a package may be empty:
12382 @smallexample @c projectfile
12392 A package may contain @emph{attribute declarations},
12393 @emph{variable declarations} and @emph{case constructions}, as will be
12396 When there is ambiguity between a project name and a package name,
12397 the name always designates the project. To avoid possible confusion, it is
12398 always a good idea to avoid naming a project with one of the
12399 names allowed for packages or any name that starts with @code{gnat}.
12402 @subsection Expressions
12405 An @emph{expression} is either a @emph{string expression} or a
12406 @emph{string list expression}.
12408 A @emph{string expression} is either a @emph{simple string expression} or a
12409 @emph{compound string expression}.
12411 A @emph{simple string expression} is one of the following:
12413 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12414 @item A string-valued variable reference (@pxref{Variables})
12415 @item A string-valued attribute reference (@pxref{Attributes})
12416 @item An external reference (@pxref{External References in Project Files})
12420 A @emph{compound string expression} is a concatenation of string expressions,
12421 using the operator @code{"&"}
12423 Path & "/" & File_Name & ".ads"
12427 A @emph{string list expression} is either a
12428 @emph{simple string list expression} or a
12429 @emph{compound string list expression}.
12431 A @emph{simple string list expression} is one of the following:
12433 @item A parenthesized list of zero or more string expressions,
12434 separated by commas
12436 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12439 @item A string list-valued variable reference
12440 @item A string list-valued attribute reference
12444 A @emph{compound string list expression} is the concatenation (using
12445 @code{"&"}) of a simple string list expression and an expression. Note that
12446 each term in a compound string list expression, except the first, may be
12447 either a string expression or a string list expression.
12449 @smallexample @c projectfile
12451 File_Name_List := () & File_Name; -- One string in this list
12452 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12454 Big_List := File_Name_List & Extended_File_Name_List;
12455 -- Concatenation of two string lists: three strings
12456 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12457 -- Illegal: must start with a string list
12462 @subsection String Types
12465 A @emph{string type declaration} introduces a discrete set of string literals.
12466 If a string variable is declared to have this type, its value
12467 is restricted to the given set of literals.
12469 Here is an example of a string type declaration:
12471 @smallexample @c projectfile
12472 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12476 Variables of a string type are called @emph{typed variables}; all other
12477 variables are called @emph{untyped variables}. Typed variables are
12478 particularly useful in @code{case} constructions, to support conditional
12479 attribute declarations.
12480 (@pxref{case Constructions}).
12482 The string literals in the list are case sensitive and must all be different.
12483 They may include any graphic characters allowed in Ada, including spaces.
12485 A string type may only be declared at the project level, not inside a package.
12487 A string type may be referenced by its name if it has been declared in the same
12488 project file, or by an expanded name whose prefix is the name of the project
12489 in which it is declared.
12492 @subsection Variables
12495 A variable may be declared at the project file level, or within a package.
12496 Here are some examples of variable declarations:
12498 @smallexample @c projectfile
12500 This_OS : OS := external ("OS"); -- a typed variable declaration
12501 That_OS := "GNU/Linux"; -- an untyped variable declaration
12506 The syntax of a @emph{typed variable declaration} is identical to the Ada
12507 syntax for an object declaration. By contrast, the syntax of an untyped
12508 variable declaration is identical to an Ada assignment statement. In fact,
12509 variable declarations in project files have some of the characteristics of
12510 an assignment, in that successive declarations for the same variable are
12511 allowed. Untyped variable declarations do establish the expected kind of the
12512 variable (string or string list), and successive declarations for it must
12513 respect the initial kind.
12516 A string variable declaration (typed or untyped) declares a variable
12517 whose value is a string. This variable may be used as a string expression.
12518 @smallexample @c projectfile
12519 File_Name := "readme.txt";
12520 Saved_File_Name := File_Name & ".saved";
12524 A string list variable declaration declares a variable whose value is a list
12525 of strings. The list may contain any number (zero or more) of strings.
12527 @smallexample @c projectfile
12529 List_With_One_Element := ("^-gnaty^-gnaty^");
12530 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12531 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12532 "pack2.ada", "util_.ada", "util.ada");
12536 The same typed variable may not be declared more than once at project level,
12537 and it may not be declared more than once in any package; it is in effect
12540 The same untyped variable may be declared several times. Declarations are
12541 elaborated in the order in which they appear, so the new value replaces
12542 the old one, and any subsequent reference to the variable uses the new value.
12543 However, as noted above, if a variable has been declared as a string, all
12545 declarations must give it a string value. Similarly, if a variable has
12546 been declared as a string list, all subsequent declarations
12547 must give it a string list value.
12549 A @emph{variable reference} may take several forms:
12552 @item The simple variable name, for a variable in the current package (if any)
12553 or in the current project
12554 @item An expanded name, whose prefix is a context name.
12558 A @emph{context} may be one of the following:
12561 @item The name of an existing package in the current project
12562 @item The name of an imported project of the current project
12563 @item The name of an ancestor project (i.e., a project extended by the current
12564 project, either directly or indirectly)
12565 @item An expanded name whose prefix is an imported/parent project name, and
12566 whose selector is a package name in that project.
12570 A variable reference may be used in an expression.
12573 @subsection Attributes
12576 A project (and its packages) may have @emph{attributes} that define
12577 the project's properties. Some attributes have values that are strings;
12578 others have values that are string lists.
12580 There are two categories of attributes: @emph{simple attributes}
12581 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12583 Legal project attribute names, and attribute names for each legal package are
12584 listed below. Attributes names are case-insensitive.
12586 The following attributes are defined on projects (all are simple attributes):
12588 @multitable @columnfractions .4 .3
12589 @item @emph{Attribute Name}
12591 @item @code{Source_Files}
12593 @item @code{Source_Dirs}
12595 @item @code{Source_List_File}
12597 @item @code{Object_Dir}
12599 @item @code{Exec_Dir}
12601 @item @code{Excluded_Source_Dirs}
12603 @item @code{Excluded_Source_Files}
12605 @item @code{Excluded_Source_List_File}
12607 @item @code{Languages}
12611 @item @code{Library_Dir}
12613 @item @code{Library_Name}
12615 @item @code{Library_Kind}
12617 @item @code{Library_Version}
12619 @item @code{Library_Interface}
12621 @item @code{Library_Auto_Init}
12623 @item @code{Library_Options}
12625 @item @code{Library_Src_Dir}
12627 @item @code{Library_ALI_Dir}
12629 @item @code{Library_GCC}
12631 @item @code{Library_Symbol_File}
12633 @item @code{Library_Symbol_Policy}
12635 @item @code{Library_Reference_Symbol_File}
12637 @item @code{Externally_Built}
12642 The following attributes are defined for package @code{Naming}
12643 (@pxref{Naming Schemes}):
12645 @multitable @columnfractions .4 .2 .2 .2
12646 @item Attribute Name @tab Category @tab Index @tab Value
12647 @item @code{Spec_Suffix}
12648 @tab associative array
12651 @item @code{Body_Suffix}
12652 @tab associative array
12655 @item @code{Separate_Suffix}
12656 @tab simple attribute
12659 @item @code{Casing}
12660 @tab simple attribute
12663 @item @code{Dot_Replacement}
12664 @tab simple attribute
12668 @tab associative array
12672 @tab associative array
12675 @item @code{Specification_Exceptions}
12676 @tab associative array
12679 @item @code{Implementation_Exceptions}
12680 @tab associative array
12686 The following attributes are defined for packages @code{Builder},
12687 @code{Compiler}, @code{Binder},
12688 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
12689 (@pxref{^Switches^Switches^ and Project Files}).
12691 @multitable @columnfractions .4 .2 .2 .2
12692 @item Attribute Name @tab Category @tab Index @tab Value
12693 @item @code{^Default_Switches^Default_Switches^}
12694 @tab associative array
12697 @item @code{^Switches^Switches^}
12698 @tab associative array
12704 In addition, package @code{Compiler} has a single string attribute
12705 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
12706 string attribute @code{Global_Configuration_Pragmas}.
12709 Each simple attribute has a default value: the empty string (for string-valued
12710 attributes) and the empty list (for string list-valued attributes).
12712 An attribute declaration defines a new value for an attribute.
12714 Examples of simple attribute declarations:
12716 @smallexample @c projectfile
12717 for Object_Dir use "objects";
12718 for Source_Dirs use ("units", "test/drivers");
12722 The syntax of a @dfn{simple attribute declaration} is similar to that of an
12723 attribute definition clause in Ada.
12725 Attributes references may be appear in expressions.
12726 The general form for such a reference is @code{<entity>'<attribute>}:
12727 Associative array attributes are functions. Associative
12728 array attribute references must have an argument that is a string literal.
12732 @smallexample @c projectfile
12734 Naming'Dot_Replacement
12735 Imported_Project'Source_Dirs
12736 Imported_Project.Naming'Casing
12737 Builder'^Default_Switches^Default_Switches^("Ada")
12741 The prefix of an attribute may be:
12743 @item @code{project} for an attribute of the current project
12744 @item The name of an existing package of the current project
12745 @item The name of an imported project
12746 @item The name of a parent project that is extended by the current project
12747 @item An expanded name whose prefix is imported/parent project name,
12748 and whose selector is a package name
12753 @smallexample @c projectfile
12756 for Source_Dirs use project'Source_Dirs & "units";
12757 for Source_Dirs use project'Source_Dirs & "test/drivers"
12763 In the first attribute declaration, initially the attribute @code{Source_Dirs}
12764 has the default value: an empty string list. After this declaration,
12765 @code{Source_Dirs} is a string list of one element: @code{"units"}.
12766 After the second attribute declaration @code{Source_Dirs} is a string list of
12767 two elements: @code{"units"} and @code{"test/drivers"}.
12769 Note: this example is for illustration only. In practice,
12770 the project file would contain only one attribute declaration:
12772 @smallexample @c projectfile
12773 for Source_Dirs use ("units", "test/drivers");
12776 @node Associative Array Attributes
12777 @subsection Associative Array Attributes
12780 Some attributes are defined as @emph{associative arrays}. An associative
12781 array may be regarded as a function that takes a string as a parameter
12782 and delivers a string or string list value as its result.
12784 Here are some examples of single associative array attribute associations:
12786 @smallexample @c projectfile
12787 for Body ("main") use "Main.ada";
12788 for ^Switches^Switches^ ("main.ada")
12790 "^-gnatv^-gnatv^");
12791 for ^Switches^Switches^ ("main.ada")
12792 use Builder'^Switches^Switches^ ("main.ada")
12797 Like untyped variables and simple attributes, associative array attributes
12798 may be declared several times. Each declaration supplies a new value for the
12799 attribute, and replaces the previous setting.
12802 An associative array attribute may be declared as a full associative array
12803 declaration, with the value of the same attribute in an imported or extended
12806 @smallexample @c projectfile
12808 for Default_Switches use Default.Builder'Default_Switches;
12813 In this example, @code{Default} must be either a project imported by the
12814 current project, or the project that the current project extends. If the
12815 attribute is in a package (in this case, in package @code{Builder}), the same
12816 package needs to be specified.
12819 A full associative array declaration replaces any other declaration for the
12820 attribute, including other full associative array declaration. Single
12821 associative array associations may be declare after a full associative
12822 declaration, modifying the value for a single association of the attribute.
12824 @node case Constructions
12825 @subsection @code{case} Constructions
12828 A @code{case} construction is used in a project file to effect conditional
12830 Here is a typical example:
12832 @smallexample @c projectfile
12835 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
12837 OS : OS_Type := external ("OS", "GNU/Linux");
12841 package Compiler is
12843 when "GNU/Linux" | "Unix" =>
12844 for ^Default_Switches^Default_Switches^ ("Ada")
12845 use ("^-gnath^-gnath^");
12847 for ^Default_Switches^Default_Switches^ ("Ada")
12848 use ("^-gnatP^-gnatP^");
12857 The syntax of a @code{case} construction is based on the Ada case statement
12858 (although there is no @code{null} construction for empty alternatives).
12860 The case expression must be a typed string variable.
12861 Each alternative comprises the reserved word @code{when}, either a list of
12862 literal strings separated by the @code{"|"} character or the reserved word
12863 @code{others}, and the @code{"=>"} token.
12864 Each literal string must belong to the string type that is the type of the
12866 An @code{others} alternative, if present, must occur last.
12868 After each @code{=>}, there are zero or more constructions. The only
12869 constructions allowed in a case construction are other case constructions,
12870 attribute declarations and variable declarations. String type declarations and
12871 package declarations are not allowed. Variable declarations are restricted to
12872 variables that have already been declared before the case construction.
12874 The value of the case variable is often given by an external reference
12875 (@pxref{External References in Project Files}).
12877 @c ****************************************
12878 @c * Objects and Sources in Project Files *
12879 @c ****************************************
12881 @node Objects and Sources in Project Files
12882 @section Objects and Sources in Project Files
12885 * Object Directory::
12887 * Source Directories::
12888 * Source File Names::
12892 Each project has exactly one object directory and one or more source
12893 directories. The source directories must contain at least one source file,
12894 unless the project file explicitly specifies that no source files are present
12895 (@pxref{Source File Names}).
12897 @node Object Directory
12898 @subsection Object Directory
12901 The object directory for a project is the directory containing the compiler's
12902 output (such as @file{ALI} files and object files) for the project's immediate
12905 The object directory is given by the value of the attribute @code{Object_Dir}
12906 in the project file.
12908 @smallexample @c projectfile
12909 for Object_Dir use "objects";
12913 The attribute @code{Object_Dir} has a string value, the path name of the object
12914 directory. The path name may be absolute or relative to the directory of the
12915 project file. This directory must already exist, and be readable and writable.
12917 By default, when the attribute @code{Object_Dir} is not given an explicit value
12918 or when its value is the empty string, the object directory is the same as the
12919 directory containing the project file.
12921 @node Exec Directory
12922 @subsection Exec Directory
12925 The exec directory for a project is the directory containing the executables
12926 for the project's main subprograms.
12928 The exec directory is given by the value of the attribute @code{Exec_Dir}
12929 in the project file.
12931 @smallexample @c projectfile
12932 for Exec_Dir use "executables";
12936 The attribute @code{Exec_Dir} has a string value, the path name of the exec
12937 directory. The path name may be absolute or relative to the directory of the
12938 project file. This directory must already exist, and be writable.
12940 By default, when the attribute @code{Exec_Dir} is not given an explicit value
12941 or when its value is the empty string, the exec directory is the same as the
12942 object directory of the project file.
12944 @node Source Directories
12945 @subsection Source Directories
12948 The source directories of a project are specified by the project file
12949 attribute @code{Source_Dirs}.
12951 This attribute's value is a string list. If the attribute is not given an
12952 explicit value, then there is only one source directory, the one where the
12953 project file resides.
12955 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
12958 @smallexample @c projectfile
12959 for Source_Dirs use ();
12963 indicates that the project contains no source files.
12965 Otherwise, each string in the string list designates one or more
12966 source directories.
12968 @smallexample @c projectfile
12969 for Source_Dirs use ("sources", "test/drivers");
12973 If a string in the list ends with @code{"/**"}, then the directory whose path
12974 name precedes the two asterisks, as well as all its subdirectories
12975 (recursively), are source directories.
12977 @smallexample @c projectfile
12978 for Source_Dirs use ("/system/sources/**");
12982 Here the directory @code{/system/sources} and all of its subdirectories
12983 (recursively) are source directories.
12985 To specify that the source directories are the directory of the project file
12986 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
12987 @smallexample @c projectfile
12988 for Source_Dirs use ("./**");
12992 Each of the source directories must exist and be readable.
12994 @node Source File Names
12995 @subsection Source File Names
12998 In a project that contains source files, their names may be specified by the
12999 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13000 (a string). Source file names never include any directory information.
13002 If the attribute @code{Source_Files} is given an explicit value, then each
13003 element of the list is a source file name.
13005 @smallexample @c projectfile
13006 for Source_Files use ("main.adb");
13007 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13011 If the attribute @code{Source_Files} is not given an explicit value,
13012 but the attribute @code{Source_List_File} is given a string value,
13013 then the source file names are contained in the text file whose path name
13014 (absolute or relative to the directory of the project file) is the
13015 value of the attribute @code{Source_List_File}.
13017 Each line in the file that is not empty or is not a comment
13018 contains a source file name.
13020 @smallexample @c projectfile
13021 for Source_List_File use "source_list.txt";
13025 By default, if neither the attribute @code{Source_Files} nor the attribute
13026 @code{Source_List_File} is given an explicit value, then each file in the
13027 source directories that conforms to the project's naming scheme
13028 (@pxref{Naming Schemes}) is an immediate source of the project.
13030 A warning is issued if both attributes @code{Source_Files} and
13031 @code{Source_List_File} are given explicit values. In this case, the attribute
13032 @code{Source_Files} prevails.
13034 Each source file name must be the name of one existing source file
13035 in one of the source directories.
13037 A @code{Source_Files} attribute whose value is an empty list
13038 indicates that there are no source files in the project.
13040 If the order of the source directories is known statically, that is if
13041 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13042 be several files with the same source file name. In this case, only the file
13043 in the first directory is considered as an immediate source of the project
13044 file. If the order of the source directories is not known statically, it is
13045 an error to have several files with the same source file name.
13047 Projects can be specified to have no Ada source
13048 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
13049 list, or the @code{"Ada"} may be absent from @code{Languages}:
13051 @smallexample @c projectfile
13052 for Source_Dirs use ();
13053 for Source_Files use ();
13054 for Languages use ("C", "C++");
13058 Otherwise, a project must contain at least one immediate source.
13060 Projects with no source files are useful as template packages
13061 (@pxref{Packages in Project Files}) for other projects; in particular to
13062 define a package @code{Naming} (@pxref{Naming Schemes}).
13064 @c ****************************
13065 @c * Importing Projects *
13066 @c ****************************
13068 @node Importing Projects
13069 @section Importing Projects
13070 @cindex @code{ADA_PROJECT_PATH}
13073 An immediate source of a project P may depend on source files that
13074 are neither immediate sources of P nor in the predefined library.
13075 To get this effect, P must @emph{import} the projects that contain the needed
13078 @smallexample @c projectfile
13080 with "project1", "utilities.gpr";
13081 with "/namings/apex.gpr";
13088 As can be seen in this example, the syntax for importing projects is similar
13089 to the syntax for importing compilation units in Ada. However, project files
13090 use literal strings instead of names, and the @code{with} clause identifies
13091 project files rather than packages.
13093 Each literal string is the file name or path name (absolute or relative) of a
13094 project file. If a string corresponds to a file name, with no path or a
13095 relative path, then its location is determined by the @emph{project path}. The
13096 latter can be queried using @code{gnatls -v}. It contains:
13100 In first position, the directory containing the current project file.
13102 In last position, the default project directory. This default project directory
13103 is part of the GNAT installation and is the standard place to install project
13104 files giving access to standard support libraries.
13106 @ref{Installing a library}
13110 In between, all the directories referenced in the
13111 ^environment variable^logical name^ @env{ADA_PROJECT_PATH} if it exists.
13115 If a relative pathname is used, as in
13117 @smallexample @c projectfile
13122 then the full path for the project is constructed by concatenating this
13123 relative path to those in the project path, in order, until a matching file is
13124 found. Any symbolic link will be fully resolved in the directory of the
13125 importing project file before the imported project file is examined.
13127 If the @code{with}'ed project file name does not have an extension,
13128 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13129 then the file name as specified in the @code{with} clause (no extension) will
13130 be used. In the above example, if a file @code{project1.gpr} is found, then it
13131 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13132 then it will be used; if neither file exists, this is an error.
13134 A warning is issued if the name of the project file does not match the
13135 name of the project; this check is case insensitive.
13137 Any source file that is an immediate source of the imported project can be
13138 used by the immediate sources of the importing project, transitively. Thus
13139 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13140 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13141 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13142 because if and when @code{B} ceases to import @code{C}, some sources in
13143 @code{A} will no longer compile.
13145 A side effect of this capability is that normally cyclic dependencies are not
13146 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13147 is not allowed to import @code{A}. However, there are cases when cyclic
13148 dependencies would be beneficial. For these cases, another form of import
13149 between projects exists, the @code{limited with}: a project @code{A} that
13150 imports a project @code{B} with a straight @code{with} may also be imported,
13151 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13152 to @code{A} include at least one @code{limited with}.
13154 @smallexample @c 0projectfile
13160 limited with "../a/a.gpr";
13168 limited with "../a/a.gpr";
13174 In the above legal example, there are two project cycles:
13177 @item A -> C -> D -> A
13181 In each of these cycle there is one @code{limited with}: import of @code{A}
13182 from @code{B} and import of @code{A} from @code{D}.
13184 The difference between straight @code{with} and @code{limited with} is that
13185 the name of a project imported with a @code{limited with} cannot be used in the
13186 project that imports it. In particular, its packages cannot be renamed and
13187 its variables cannot be referred to.
13189 An exception to the above rules for @code{limited with} is that for the main
13190 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13191 @code{limited with} is equivalent to a straight @code{with}. For example,
13192 in the example above, projects @code{B} and @code{D} could not be main
13193 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13194 each have a @code{limited with} that is the only one in a cycle of importing
13197 @c *********************
13198 @c * Project Extension *
13199 @c *********************
13201 @node Project Extension
13202 @section Project Extension
13205 During development of a large system, it is sometimes necessary to use
13206 modified versions of some of the source files, without changing the original
13207 sources. This can be achieved through the @emph{project extension} facility.
13209 @smallexample @c projectfile
13210 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13214 A project extension declaration introduces an extending project
13215 (the @emph{child}) and a project being extended (the @emph{parent}).
13217 By default, a child project inherits all the sources of its parent.
13218 However, inherited sources can be overridden: a unit in a parent is hidden
13219 by a unit of the same name in the child.
13221 Inherited sources are considered to be sources (but not immediate sources)
13222 of the child project; see @ref{Project File Syntax}.
13224 An inherited source file retains any switches specified in the parent project.
13226 For example if the project @code{Utilities} contains the spec and the
13227 body of an Ada package @code{Util_IO}, then the project
13228 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13229 The original body of @code{Util_IO} will not be considered in program builds.
13230 However, the package spec will still be found in the project
13233 A child project can have only one parent, except when it is qualified as
13234 abstract. But it may import any number of other projects.
13236 A project is not allowed to import directly or indirectly at the same time a
13237 child project and any of its ancestors.
13239 @c *******************************
13240 @c * Project Hierarchy Extension *
13241 @c *******************************
13243 @node Project Hierarchy Extension
13244 @section Project Hierarchy Extension
13247 When extending a large system spanning multiple projects, it is often
13248 inconvenient to extend every project in the hierarchy that is impacted by a
13249 small change introduced. In such cases, it is possible to create a virtual
13250 extension of entire hierarchy using @code{extends all} relationship.
13252 When the project is extended using @code{extends all} inheritance, all projects
13253 that are imported by it, both directly and indirectly, are considered virtually
13254 extended. That is, the Project Manager creates "virtual projects"
13255 that extend every project in the hierarchy; all these virtual projects have
13256 no sources of their own and have as object directory the object directory of
13257 the root of "extending all" project.
13259 It is possible to explicitly extend one or more projects in the hierarchy
13260 in order to modify the sources. These extending projects must be imported by
13261 the "extending all" project, which will replace the corresponding virtual
13262 projects with the explicit ones.
13264 When building such a project hierarchy extension, the Project Manager will
13265 ensure that both modified sources and sources in virtual extending projects
13266 that depend on them, are recompiled.
13268 By means of example, consider the following hierarchy of projects.
13272 project A, containing package P1
13274 project B importing A and containing package P2 which depends on P1
13276 project C importing B and containing package P3 which depends on P2
13280 We want to modify packages P1 and P3.
13282 This project hierarchy will need to be extended as follows:
13286 Create project A1 that extends A, placing modified P1 there:
13288 @smallexample @c 0projectfile
13289 project A1 extends "(@dots{})/A" is
13294 Create project C1 that "extends all" C and imports A1, placing modified
13297 @smallexample @c 0projectfile
13298 with "(@dots{})/A1";
13299 project C1 extends all "(@dots{})/C" is
13304 When you build project C1, your entire modified project space will be
13305 recompiled, including the virtual project B1 that has been impacted by the
13306 "extending all" inheritance of project C.
13308 Note that if a Library Project in the hierarchy is virtually extended,
13309 the virtual project that extends the Library Project is not a Library Project.
13311 @c ****************************************
13312 @c * External References in Project Files *
13313 @c ****************************************
13315 @node External References in Project Files
13316 @section External References in Project Files
13319 A project file may contain references to external variables; such references
13320 are called @emph{external references}.
13322 An external variable is either defined as part of the environment (an
13323 environment variable in Unix, for example) or else specified on the command
13324 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13325 If both, then the command line value is used.
13327 The value of an external reference is obtained by means of the built-in
13328 function @code{external}, which returns a string value.
13329 This function has two forms:
13331 @item @code{external (external_variable_name)}
13332 @item @code{external (external_variable_name, default_value)}
13336 Each parameter must be a string literal. For example:
13338 @smallexample @c projectfile
13340 external ("OS", "GNU/Linux")
13344 In the form with one parameter, the function returns the value of
13345 the external variable given as parameter. If this name is not present in the
13346 environment, the function returns an empty string.
13348 In the form with two string parameters, the second argument is
13349 the value returned when the variable given as the first argument is not
13350 present in the environment. In the example above, if @code{"OS"} is not
13351 the name of ^an environment variable^a logical name^ and is not passed on
13352 the command line, then the returned value is @code{"GNU/Linux"}.
13354 An external reference may be part of a string expression or of a string
13355 list expression, and can therefore appear in a variable declaration or
13356 an attribute declaration.
13358 @smallexample @c projectfile
13360 type Mode_Type is ("Debug", "Release");
13361 Mode : Mode_Type := external ("MODE");
13368 @c *****************************
13369 @c * Packages in Project Files *
13370 @c *****************************
13372 @node Packages in Project Files
13373 @section Packages in Project Files
13376 A @emph{package} defines the settings for project-aware tools within a
13378 For each such tool one can declare a package; the names for these
13379 packages are preset (@pxref{Packages}).
13380 A package may contain variable declarations, attribute declarations, and case
13383 @smallexample @c projectfile
13386 package Builder is -- used by gnatmake
13387 for ^Default_Switches^Default_Switches^ ("Ada")
13396 The syntax of package declarations mimics that of package in Ada.
13398 Most of the packages have an attribute
13399 @code{^Default_Switches^Default_Switches^}.
13400 This attribute is an associative array, and its value is a string list.
13401 The index of the associative array is the name of a programming language (case
13402 insensitive). This attribute indicates the ^switch^switch^
13403 or ^switches^switches^ to be used
13404 with the corresponding tool.
13406 Some packages also have another attribute, @code{^Switches^Switches^},
13407 an associative array whose value is a string list.
13408 The index is the name of a source file.
13409 This attribute indicates the ^switch^switch^
13410 or ^switches^switches^ to be used by the corresponding
13411 tool when dealing with this specific file.
13413 Further information on these ^switch^switch^-related attributes is found in
13414 @ref{^Switches^Switches^ and Project Files}.
13416 A package may be declared as a @emph{renaming} of another package; e.g., from
13417 the project file for an imported project.
13419 @smallexample @c projectfile
13421 with "/global/apex.gpr";
13423 package Naming renames Apex.Naming;
13430 Packages that are renamed in other project files often come from project files
13431 that have no sources: they are just used as templates. Any modification in the
13432 template will be reflected automatically in all the project files that rename
13433 a package from the template.
13435 In addition to the tool-oriented packages, you can also declare a package
13436 named @code{Naming} to establish specialized source file naming conventions
13437 (@pxref{Naming Schemes}).
13439 @c ************************************
13440 @c * Variables from Imported Projects *
13441 @c ************************************
13443 @node Variables from Imported Projects
13444 @section Variables from Imported Projects
13447 An attribute or variable defined in an imported or parent project can
13448 be used in expressions in the importing / extending project.
13449 Such an attribute or variable is denoted by an expanded name whose prefix
13450 is either the name of the project or the expanded name of a package within
13453 @smallexample @c projectfile
13456 project Main extends "base" is
13457 Var1 := Imported.Var;
13458 Var2 := Base.Var & ".new";
13463 for ^Default_Switches^Default_Switches^ ("Ada")
13464 use Imported.Builder'Ada_^Switches^Switches^ &
13465 "^-gnatg^-gnatg^" &
13471 package Compiler is
13472 for ^Default_Switches^Default_Switches^ ("Ada")
13473 use Base.Compiler'Ada_^Switches^Switches^;
13484 The value of @code{Var1} is a copy of the variable @code{Var} defined
13485 in the project file @file{"imported.gpr"}
13487 the value of @code{Var2} is a copy of the value of variable @code{Var}
13488 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13490 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13491 @code{Builder} is a string list that includes in its value a copy of the value
13492 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13493 in project file @file{imported.gpr} plus two new elements:
13494 @option{"^-gnatg^-gnatg^"}
13495 and @option{"^-v^-v^"};
13497 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13498 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13499 defined in the @code{Compiler} package in project file @file{base.gpr},
13500 the project being extended.
13503 @c ******************
13504 @c * Naming Schemes *
13505 @c ******************
13507 @node Naming Schemes
13508 @section Naming Schemes
13511 Sometimes an Ada software system is ported from a foreign compilation
13512 environment to GNAT, and the file names do not use the default GNAT
13513 conventions. Instead of changing all the file names (which for a variety
13514 of reasons might not be possible), you can define the relevant file
13515 naming scheme in the @code{Naming} package in your project file.
13518 Note that the use of pragmas described in
13519 @ref{Alternative File Naming Schemes} by mean of a configuration
13520 pragmas file is not supported when using project files. You must use
13521 the features described in this paragraph. You can however use specify
13522 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13525 For example, the following
13526 package models the Apex file naming rules:
13528 @smallexample @c projectfile
13531 for Casing use "lowercase";
13532 for Dot_Replacement use ".";
13533 for Spec_Suffix ("Ada") use ".1.ada";
13534 for Body_Suffix ("Ada") use ".2.ada";
13541 For example, the following package models the HP Ada file naming rules:
13543 @smallexample @c projectfile
13546 for Casing use "lowercase";
13547 for Dot_Replacement use "__";
13548 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13549 for Body_Suffix ("Ada") use ".^ada^ada^";
13555 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13556 names in lower case)
13560 You can define the following attributes in package @code{Naming}:
13564 @item @code{Casing}
13565 This must be a string with one of the three values @code{"lowercase"},
13566 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13569 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13571 @item @code{Dot_Replacement}
13572 This must be a string whose value satisfies the following conditions:
13575 @item It must not be empty
13576 @item It cannot start or end with an alphanumeric character
13577 @item It cannot be a single underscore
13578 @item It cannot start with an underscore followed by an alphanumeric
13579 @item It cannot contain a dot @code{'.'} except if the entire string
13584 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13586 @item @code{Spec_Suffix}
13587 This is an associative array (indexed by the programming language name, case
13588 insensitive) whose value is a string that must satisfy the following
13592 @item It must not be empty
13593 @item It must include at least one dot
13596 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13597 @code{"^.ads^.ADS^"}.
13599 @item @code{Body_Suffix}
13600 This is an associative array (indexed by the programming language name, case
13601 insensitive) whose value is a string that must satisfy the following
13605 @item It must not be empty
13606 @item It must include at least one dot
13607 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13610 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13611 same string, then a file name that ends with the longest of these two suffixes
13612 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13613 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13615 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13616 @code{"^.adb^.ADB^"}.
13618 @item @code{Separate_Suffix}
13619 This must be a string whose value satisfies the same conditions as
13620 @code{Body_Suffix}. The same "longest suffix" rules apply.
13623 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13624 value as @code{Body_Suffix ("Ada")}.
13628 You can use the associative array attribute @code{Spec} to define
13629 the source file name for an individual Ada compilation unit's spec. The array
13630 index must be a string literal that identifies the Ada unit (case insensitive).
13631 The value of this attribute must be a string that identifies the file that
13632 contains this unit's spec (case sensitive or insensitive depending on the
13635 @smallexample @c projectfile
13636 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13641 You can use the associative array attribute @code{Body} to
13642 define the source file name for an individual Ada compilation unit's body
13643 (possibly a subunit). The array index must be a string literal that identifies
13644 the Ada unit (case insensitive). The value of this attribute must be a string
13645 that identifies the file that contains this unit's body or subunit (case
13646 sensitive or insensitive depending on the operating system).
13648 @smallexample @c projectfile
13649 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13653 @c ********************
13654 @c * Library Projects *
13655 @c ********************
13657 @node Library Projects
13658 @section Library Projects
13661 @emph{Library projects} are projects whose object code is placed in a library.
13662 (Note that this facility is not yet supported on all platforms)
13664 To create a library project, you need to define in its project file
13665 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
13666 Additionally, you may define other library-related attributes such as
13667 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
13668 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
13670 The @code{Library_Name} attribute has a string value. There is no restriction
13671 on the name of a library. It is the responsibility of the developer to
13672 choose a name that will be accepted by the platform. It is recommended to
13673 choose names that could be Ada identifiers; such names are almost guaranteed
13674 to be acceptable on all platforms.
13676 The @code{Library_Dir} attribute has a string value that designates the path
13677 (absolute or relative) of the directory where the library will reside.
13678 It must designate an existing directory, and this directory must be writable,
13679 different from the project's object directory and from any source directory
13680 in the project tree.
13682 If both @code{Library_Name} and @code{Library_Dir} are specified and
13683 are legal, then the project file defines a library project. The optional
13684 library-related attributes are checked only for such project files.
13686 The @code{Library_Kind} attribute has a string value that must be one of the
13687 following (case insensitive): @code{"static"}, @code{"dynamic"} or
13688 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
13689 attribute is not specified, the library is a static library, that is
13690 an archive of object files that can be potentially linked into a
13691 static executable. Otherwise, the library may be dynamic or
13692 relocatable, that is a library that is loaded only at the start of execution.
13694 If you need to build both a static and a dynamic library, you should use two
13695 different object directories, since in some cases some extra code needs to
13696 be generated for the latter. For such cases, it is recommended to either use
13697 two different project files, or a single one which uses external variables
13698 to indicate what kind of library should be build.
13700 The @code{Library_ALI_Dir} attribute may be specified to indicate the
13701 directory where the ALI files of the library will be copied. When it is
13702 not specified, the ALI files are copied to the directory specified in
13703 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
13704 must be writable and different from the project's object directory and from
13705 any source directory in the project tree.
13707 The @code{Library_Version} attribute has a string value whose interpretation
13708 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
13709 used only for dynamic/relocatable libraries as the internal name of the
13710 library (the @code{"soname"}). If the library file name (built from the
13711 @code{Library_Name}) is different from the @code{Library_Version}, then the
13712 library file will be a symbolic link to the actual file whose name will be
13713 @code{Library_Version}.
13717 @smallexample @c projectfile
13723 for Library_Dir use "lib_dir";
13724 for Library_Name use "dummy";
13725 for Library_Kind use "relocatable";
13726 for Library_Version use "libdummy.so." & Version;
13733 Directory @file{lib_dir} will contain the internal library file whose name
13734 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
13735 @file{libdummy.so.1}.
13737 When @command{gnatmake} detects that a project file
13738 is a library project file, it will check all immediate sources of the project
13739 and rebuild the library if any of the sources have been recompiled.
13741 Standard project files can import library project files. In such cases,
13742 the libraries will only be rebuilt if some of its sources are recompiled
13743 because they are in the closure of some other source in an importing project.
13744 Sources of the library project files that are not in such a closure will
13745 not be checked, unless the full library is checked, because one of its sources
13746 needs to be recompiled.
13748 For instance, assume the project file @code{A} imports the library project file
13749 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
13750 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
13751 @file{l2.ads}, @file{l2.adb}.
13753 If @file{l1.adb} has been modified, then the library associated with @code{L}
13754 will be rebuilt when compiling all the immediate sources of @code{A} only
13755 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
13758 To be sure that all the sources in the library associated with @code{L} are
13759 up to date, and that all the sources of project @code{A} are also up to date,
13760 the following two commands needs to be used:
13767 When a library is built or rebuilt, an attempt is made first to delete all
13768 files in the library directory.
13769 All @file{ALI} files will also be copied from the object directory to the
13770 library directory. To build executables, @command{gnatmake} will use the
13771 library rather than the individual object files.
13774 It is also possible to create library project files for third-party libraries
13775 that are precompiled and cannot be compiled locally thanks to the
13776 @code{externally_built} attribute. (See @ref{Installing a library}).
13779 @c *******************************
13780 @c * Stand-alone Library Projects *
13781 @c *******************************
13783 @node Stand-alone Library Projects
13784 @section Stand-alone Library Projects
13787 A Stand-alone Library is a library that contains the necessary code to
13788 elaborate the Ada units that are included in the library. A Stand-alone
13789 Library is suitable to be used in an executable when the main is not
13790 in Ada. However, Stand-alone Libraries may also be used with an Ada main
13793 A Stand-alone Library Project is a Library Project where the library is
13794 a Stand-alone Library.
13796 To be a Stand-alone Library Project, in addition to the two attributes
13797 that make a project a Library Project (@code{Library_Name} and
13798 @code{Library_Dir}, see @ref{Library Projects}), the attribute
13799 @code{Library_Interface} must be defined.
13801 @smallexample @c projectfile
13803 for Library_Dir use "lib_dir";
13804 for Library_Name use "dummy";
13805 for Library_Interface use ("int1", "int1.child");
13809 Attribute @code{Library_Interface} has a nonempty string list value,
13810 each string in the list designating a unit contained in an immediate source
13811 of the project file.
13813 When a Stand-alone Library is built, first the binder is invoked to build
13814 a package whose name depends on the library name
13815 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
13816 This binder-generated package includes initialization and
13817 finalization procedures whose
13818 names depend on the library name (dummyinit and dummyfinal in the example
13819 above). The object corresponding to this package is included in the library.
13821 A dynamic or relocatable Stand-alone Library is automatically initialized
13822 if automatic initialization of Stand-alone Libraries is supported on the
13823 platform and if attribute @code{Library_Auto_Init} is not specified or
13824 is specified with the value "true". A static Stand-alone Library is never
13825 automatically initialized.
13827 Single string attribute @code{Library_Auto_Init} may be specified with only
13828 two possible values: "false" or "true" (case-insensitive). Specifying
13829 "false" for attribute @code{Library_Auto_Init} will prevent automatic
13830 initialization of dynamic or relocatable libraries.
13832 When a non-automatically initialized Stand-alone Library is used
13833 in an executable, its initialization procedure must be called before
13834 any service of the library is used.
13835 When the main subprogram is in Ada, it may mean that the initialization
13836 procedure has to be called during elaboration of another package.
13838 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
13839 (those that are listed in attribute @code{Library_Interface}) are copied to
13840 the Library Directory. As a consequence, only the Interface Units may be
13841 imported from Ada units outside of the library. If other units are imported,
13842 the binding phase will fail.
13844 When a Stand-Alone Library is bound, the switches that are specified in
13845 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
13846 used in the call to @command{gnatbind}.
13848 The string list attribute @code{Library_Options} may be used to specified
13849 additional switches to the call to @command{gcc} to link the library.
13851 The attribute @code{Library_Src_Dir}, may be specified for a
13852 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
13853 single string value. Its value must be the path (absolute or relative to the
13854 project directory) of an existing directory. This directory cannot be the
13855 object directory or one of the source directories, but it can be the same as
13856 the library directory. The sources of the Interface
13857 Units of the library, necessary to an Ada client of the library, will be
13858 copied to the designated directory, called Interface Copy directory.
13859 These sources includes the specs of the Interface Units, but they may also
13860 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
13861 are used, or when there is a generic units in the spec. Before the sources
13862 are copied to the Interface Copy directory, an attempt is made to delete all
13863 files in the Interface Copy directory.
13865 @c *************************************
13866 @c * Switches Related to Project Files *
13867 @c *************************************
13868 @node Switches Related to Project Files
13869 @section Switches Related to Project Files
13872 The following switches are used by GNAT tools that support project files:
13876 @item ^-P^/PROJECT_FILE=^@var{project}
13877 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
13878 Indicates the name of a project file. This project file will be parsed with
13879 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
13880 if any, and using the external references indicated
13881 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
13883 There may zero, one or more spaces between @option{-P} and @var{project}.
13887 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
13890 Since the Project Manager parses the project file only after all the switches
13891 on the command line are checked, the order of the switches
13892 @option{^-P^/PROJECT_FILE^},
13893 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
13894 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
13896 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
13897 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
13898 Indicates that external variable @var{name} has the value @var{value}.
13899 The Project Manager will use this value for occurrences of
13900 @code{external(name)} when parsing the project file.
13904 If @var{name} or @var{value} includes a space, then @var{name=value} should be
13905 put between quotes.
13913 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
13914 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
13915 @var{name}, only the last one is used.
13918 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
13919 takes precedence over the value of the same name in the environment.
13921 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
13922 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
13923 Indicates the verbosity of the parsing of GNAT project files.
13926 @option{-vP0} means Default;
13927 @option{-vP1} means Medium;
13928 @option{-vP2} means High.
13932 There are three possible options for this qualifier: DEFAULT, MEDIUM and
13937 The default is ^Default^DEFAULT^: no output for syntactically correct
13940 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
13941 only the last one is used.
13943 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
13944 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
13945 Add directory <dir> at the beginning of the project search path, in order,
13946 after the current working directory.
13950 @cindex @option{-eL} (any project-aware tool)
13951 Follow all symbolic links when processing project files.
13954 @item ^--subdirs^/SUBDIRS^=<subdir>
13955 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
13956 This switch is recognized by gnatmake and gnatclean. It indicate that the real
13957 directories (except the source directories) are the subdirectories <subdir>
13958 of the directories specified in the project files. This applies in particular
13959 to object directories, library directories and exec directories. If the
13960 subdirectories do not exist, they are created automatically.
13964 @c **********************************
13965 @c * Tools Supporting Project Files *
13966 @c **********************************
13968 @node Tools Supporting Project Files
13969 @section Tools Supporting Project Files
13972 * gnatmake and Project Files::
13973 * The GNAT Driver and Project Files::
13976 @node gnatmake and Project Files
13977 @subsection gnatmake and Project Files
13980 This section covers several topics related to @command{gnatmake} and
13981 project files: defining ^switches^switches^ for @command{gnatmake}
13982 and for the tools that it invokes; specifying configuration pragmas;
13983 the use of the @code{Main} attribute; building and rebuilding library project
13987 * ^Switches^Switches^ and Project Files::
13988 * Specifying Configuration Pragmas::
13989 * Project Files and Main Subprograms::
13990 * Library Project Files::
13993 @node ^Switches^Switches^ and Project Files
13994 @subsubsection ^Switches^Switches^ and Project Files
13997 It is not currently possible to specify VMS style qualifiers in the project
13998 files; only Unix style ^switches^switches^ may be specified.
14002 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14003 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14004 attribute, a @code{^Switches^Switches^} attribute, or both;
14005 as their names imply, these ^switch^switch^-related
14006 attributes affect the ^switches^switches^ that are used for each of these GNAT
14008 @command{gnatmake} is invoked. As will be explained below, these
14009 component-specific ^switches^switches^ precede
14010 the ^switches^switches^ provided on the @command{gnatmake} command line.
14012 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14013 array indexed by language name (case insensitive) whose value is a string list.
14016 @smallexample @c projectfile
14018 package Compiler is
14019 for ^Default_Switches^Default_Switches^ ("Ada")
14020 use ("^-gnaty^-gnaty^",
14027 The @code{^Switches^Switches^} attribute is also an associative array,
14028 indexed by a file name (which may or may not be case sensitive, depending
14029 on the operating system) whose value is a string list. For example:
14031 @smallexample @c projectfile
14034 for ^Switches^Switches^ ("main1.adb")
14036 for ^Switches^Switches^ ("main2.adb")
14043 For the @code{Builder} package, the file names must designate source files
14044 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14045 file names must designate @file{ALI} or source files for main subprograms.
14046 In each case just the file name without an explicit extension is acceptable.
14048 For each tool used in a program build (@command{gnatmake}, the compiler, the
14049 binder, and the linker), the corresponding package @dfn{contributes} a set of
14050 ^switches^switches^ for each file on which the tool is invoked, based on the
14051 ^switch^switch^-related attributes defined in the package.
14052 In particular, the ^switches^switches^
14053 that each of these packages contributes for a given file @var{f} comprise:
14057 the value of attribute @code{^Switches^Switches^ (@var{f})},
14058 if it is specified in the package for the given file,
14060 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14061 if it is specified in the package.
14065 If neither of these attributes is defined in the package, then the package does
14066 not contribute any ^switches^switches^ for the given file.
14068 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14069 two sets, in the following order: those contributed for the file
14070 by the @code{Builder} package;
14071 and the switches passed on the command line.
14073 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14074 the ^switches^switches^ passed to the tool comprise three sets,
14075 in the following order:
14079 the applicable ^switches^switches^ contributed for the file
14080 by the @code{Builder} package in the project file supplied on the command line;
14083 those contributed for the file by the package (in the relevant project file --
14084 see below) corresponding to the tool; and
14087 the applicable switches passed on the command line.
14091 The term @emph{applicable ^switches^switches^} reflects the fact that
14092 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14093 tools, depending on the individual ^switch^switch^.
14095 @command{gnatmake} may invoke the compiler on source files from different
14096 projects. The Project Manager will use the appropriate project file to
14097 determine the @code{Compiler} package for each source file being compiled.
14098 Likewise for the @code{Binder} and @code{Linker} packages.
14100 As an example, consider the following package in a project file:
14102 @smallexample @c projectfile
14105 package Compiler is
14106 for ^Default_Switches^Default_Switches^ ("Ada")
14108 for ^Switches^Switches^ ("a.adb")
14110 for ^Switches^Switches^ ("b.adb")
14112 "^-gnaty^-gnaty^");
14119 If @command{gnatmake} is invoked with this project file, and it needs to
14120 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14121 @file{a.adb} will be compiled with the ^switch^switch^
14122 @option{^-O1^-O1^},
14123 @file{b.adb} with ^switches^switches^
14125 and @option{^-gnaty^-gnaty^},
14126 and @file{c.adb} with @option{^-g^-g^}.
14128 The following example illustrates the ordering of the ^switches^switches^
14129 contributed by different packages:
14131 @smallexample @c projectfile
14135 for ^Switches^Switches^ ("main.adb")
14143 package Compiler is
14144 for ^Switches^Switches^ ("main.adb")
14152 If you issue the command:
14155 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14159 then the compiler will be invoked on @file{main.adb} with the following
14160 sequence of ^switches^switches^
14163 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14166 with the last @option{^-O^-O^}
14167 ^switch^switch^ having precedence over the earlier ones;
14168 several other ^switches^switches^
14169 (such as @option{^-c^-c^}) are added implicitly.
14171 The ^switches^switches^
14173 and @option{^-O1^-O1^} are contributed by package
14174 @code{Builder}, @option{^-O2^-O2^} is contributed
14175 by the package @code{Compiler}
14176 and @option{^-O0^-O0^} comes from the command line.
14178 The @option{^-g^-g^}
14179 ^switch^switch^ will also be passed in the invocation of
14180 @command{Gnatlink.}
14182 A final example illustrates switch contributions from packages in different
14185 @smallexample @c projectfile
14188 for Source_Files use ("pack.ads", "pack.adb");
14189 package Compiler is
14190 for ^Default_Switches^Default_Switches^ ("Ada")
14191 use ("^-gnata^-gnata^");
14199 for Source_Files use ("foo_main.adb", "bar_main.adb");
14201 for ^Switches^Switches^ ("foo_main.adb")
14209 -- Ada source file:
14211 procedure Foo_Main is
14219 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14223 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14224 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14225 @option{^-gnato^-gnato^} (passed on the command line).
14226 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14227 are @option{^-g^-g^} from @code{Proj4.Builder},
14228 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14229 and @option{^-gnato^-gnato^} from the command line.
14232 When using @command{gnatmake} with project files, some ^switches^switches^ or
14233 arguments may be expressed as relative paths. As the working directory where
14234 compilation occurs may change, these relative paths are converted to absolute
14235 paths. For the ^switches^switches^ found in a project file, the relative paths
14236 are relative to the project file directory, for the switches on the command
14237 line, they are relative to the directory where @command{gnatmake} is invoked.
14238 The ^switches^switches^ for which this occurs are:
14244 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14246 ^-o^-o^, object files specified in package @code{Linker} or after
14247 -largs on the command line). The exception to this rule is the ^switch^switch^
14248 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14250 @node Specifying Configuration Pragmas
14251 @subsubsection Specifying Configuration Pragmas
14253 When using @command{gnatmake} with project files, if there exists a file
14254 @file{gnat.adc} that contains configuration pragmas, this file will be
14257 Configuration pragmas can be defined by means of the following attributes in
14258 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14259 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14261 Both these attributes are single string attributes. Their values is the path
14262 name of a file containing configuration pragmas. If a path name is relative,
14263 then it is relative to the project directory of the project file where the
14264 attribute is defined.
14266 When compiling a source, the configuration pragmas used are, in order,
14267 those listed in the file designated by attribute
14268 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14269 project file, if it is specified, and those listed in the file designated by
14270 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14271 the project file of the source, if it exists.
14273 @node Project Files and Main Subprograms
14274 @subsubsection Project Files and Main Subprograms
14277 When using a project file, you can invoke @command{gnatmake}
14278 with one or several main subprograms, by specifying their source files on the
14282 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14286 Each of these needs to be a source file of the same project, except
14287 when the switch ^-u^/UNIQUE^ is used.
14290 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14291 same project, one of the project in the tree rooted at the project specified
14292 on the command line. The package @code{Builder} of this common project, the
14293 "main project" is the one that is considered by @command{gnatmake}.
14296 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14297 imported directly or indirectly by the project specified on the command line.
14298 Note that if such a source file is not part of the project specified on the
14299 command line, the ^switches^switches^ found in package @code{Builder} of the
14300 project specified on the command line, if any, that are transmitted
14301 to the compiler will still be used, not those found in the project file of
14305 When using a project file, you can also invoke @command{gnatmake} without
14306 explicitly specifying any main, and the effect depends on whether you have
14307 defined the @code{Main} attribute. This attribute has a string list value,
14308 where each element in the list is the name of a source file (the file
14309 extension is optional) that contains a unit that can be a main subprogram.
14311 If the @code{Main} attribute is defined in a project file as a non-empty
14312 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14313 line, then invoking @command{gnatmake} with this project file but without any
14314 main on the command line is equivalent to invoking @command{gnatmake} with all
14315 the file names in the @code{Main} attribute on the command line.
14318 @smallexample @c projectfile
14321 for Main use ("main1", "main2", "main3");
14327 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14329 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14331 When the project attribute @code{Main} is not specified, or is specified
14332 as an empty string list, or when the switch @option{-u} is used on the command
14333 line, then invoking @command{gnatmake} with no main on the command line will
14334 result in all immediate sources of the project file being checked, and
14335 potentially recompiled. Depending on the presence of the switch @option{-u},
14336 sources from other project files on which the immediate sources of the main
14337 project file depend are also checked and potentially recompiled. In other
14338 words, the @option{-u} switch is applied to all of the immediate sources of the
14341 When no main is specified on the command line and attribute @code{Main} exists
14342 and includes several mains, or when several mains are specified on the
14343 command line, the default ^switches^switches^ in package @code{Builder} will
14344 be used for all mains, even if there are specific ^switches^switches^
14345 specified for one or several mains.
14347 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14348 the specific ^switches^switches^ for each main, if they are specified.
14350 @node Library Project Files
14351 @subsubsection Library Project Files
14354 When @command{gnatmake} is invoked with a main project file that is a library
14355 project file, it is not allowed to specify one or more mains on the command
14359 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14360 ^-l^/ACTION=LINK^ have special meanings.
14363 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14364 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14367 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14368 to @command{gnatmake} that the binder generated file should be compiled
14369 (in the case of a stand-alone library) and that the library should be built.
14373 @node The GNAT Driver and Project Files
14374 @subsection The GNAT Driver and Project Files
14377 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14378 can benefit from project files:
14379 @command{^gnatbind^gnatbind^},
14380 @command{^gnatcheck^gnatcheck^}),
14381 @command{^gnatclean^gnatclean^}),
14382 @command{^gnatelim^gnatelim^},
14383 @command{^gnatfind^gnatfind^},
14384 @command{^gnatlink^gnatlink^},
14385 @command{^gnatls^gnatls^},
14386 @command{^gnatmetric^gnatmetric^},
14387 @command{^gnatpp^gnatpp^},
14388 @command{^gnatstub^gnatstub^},
14389 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14390 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14391 They must be invoked through the @command{gnat} driver.
14393 The @command{gnat} driver is a wrapper that accepts a number of commands and
14394 calls the corresponding tool. It was designed initially for VMS platforms (to
14395 convert VMS qualifiers to Unix-style switches), but it is now available on all
14398 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14399 (case insensitive):
14403 BIND to invoke @command{^gnatbind^gnatbind^}
14405 CHOP to invoke @command{^gnatchop^gnatchop^}
14407 CLEAN to invoke @command{^gnatclean^gnatclean^}
14409 COMP or COMPILE to invoke the compiler
14411 ELIM to invoke @command{^gnatelim^gnatelim^}
14413 FIND to invoke @command{^gnatfind^gnatfind^}
14415 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14417 LINK to invoke @command{^gnatlink^gnatlink^}
14419 LS or LIST to invoke @command{^gnatls^gnatls^}
14421 MAKE to invoke @command{^gnatmake^gnatmake^}
14423 NAME to invoke @command{^gnatname^gnatname^}
14425 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14427 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14429 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14431 STUB to invoke @command{^gnatstub^gnatstub^}
14433 XREF to invoke @command{^gnatxref^gnatxref^}
14437 (note that the compiler is invoked using the command
14438 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14441 On non-VMS platforms, between @command{gnat} and the command, two
14442 special switches may be used:
14446 @command{-v} to display the invocation of the tool.
14448 @command{-dn} to prevent the @command{gnat} driver from removing
14449 the temporary files it has created. These temporary files are
14450 configuration files and temporary file list files.
14454 The command may be followed by switches and arguments for the invoked
14458 gnat bind -C main.ali
14464 Switches may also be put in text files, one switch per line, and the text
14465 files may be specified with their path name preceded by '@@'.
14468 gnat bind @@args.txt main.ali
14472 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14473 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14474 (@option{^-P^/PROJECT_FILE^},
14475 @option{^-X^/EXTERNAL_REFERENCE^} and
14476 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14477 the switches of the invoking tool.
14480 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14481 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14482 the immediate sources of the specified project file.
14485 When GNAT METRIC is used with a project file, but with no source
14486 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14487 with all the immediate sources of the specified project file and with
14488 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14492 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14493 a project file, no source is specified on the command line and
14494 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14495 the underlying tool (^gnatpp^gnatpp^ or
14496 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14497 not only for the immediate sources of the main project.
14499 (-U stands for Universal or Union of the project files of the project tree)
14503 For each of the following commands, there is optionally a corresponding
14504 package in the main project.
14508 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14511 package @code{Check} for command CHECK (invoking
14512 @code{^gnatcheck^gnatcheck^})
14515 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14518 package @code{Cross_Reference} for command XREF (invoking
14519 @code{^gnatxref^gnatxref^})
14522 package @code{Eliminate} for command ELIM (invoking
14523 @code{^gnatelim^gnatelim^})
14526 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14529 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14532 package @code{Gnatstub} for command STUB
14533 (invoking @code{^gnatstub^gnatstub^})
14536 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14539 package @code{Metrics} for command METRIC
14540 (invoking @code{^gnatmetric^gnatmetric^})
14543 package @code{Pretty_Printer} for command PP or PRETTY
14544 (invoking @code{^gnatpp^gnatpp^})
14549 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14550 a simple variable with a string list value. It contains ^switches^switches^
14551 for the invocation of @code{^gnatls^gnatls^}.
14553 @smallexample @c projectfile
14557 for ^Switches^Switches^
14566 All other packages have two attribute @code{^Switches^Switches^} and
14567 @code{^Default_Switches^Default_Switches^}.
14570 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14571 source file name, that has a string list value: the ^switches^switches^ to be
14572 used when the tool corresponding to the package is invoked for the specific
14576 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14577 indexed by the programming language that has a string list value.
14578 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14579 ^switches^switches^ for the invocation of the tool corresponding
14580 to the package, except if a specific @code{^Switches^Switches^} attribute
14581 is specified for the source file.
14583 @smallexample @c projectfile
14587 for Source_Dirs use ("./**");
14590 for ^Switches^Switches^ use
14597 package Compiler is
14598 for ^Default_Switches^Default_Switches^ ("Ada")
14599 use ("^-gnatv^-gnatv^",
14600 "^-gnatwa^-gnatwa^");
14606 for ^Default_Switches^Default_Switches^ ("Ada")
14614 for ^Default_Switches^Default_Switches^ ("Ada")
14616 for ^Switches^Switches^ ("main.adb")
14625 for ^Default_Switches^Default_Switches^ ("Ada")
14632 package Cross_Reference is
14633 for ^Default_Switches^Default_Switches^ ("Ada")
14638 end Cross_Reference;
14644 With the above project file, commands such as
14647 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14648 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14649 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14650 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14651 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
14655 will set up the environment properly and invoke the tool with the switches
14656 found in the package corresponding to the tool:
14657 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
14658 except @code{^Switches^Switches^ ("main.adb")}
14659 for @code{^gnatlink^gnatlink^}.
14660 It is also possible to invoke some of the tools,
14661 @code{^gnatcheck^gnatcheck^}),
14662 @code{^gnatmetric^gnatmetric^}),
14663 and @code{^gnatpp^gnatpp^})
14664 on a set of project units thanks to the combination of the switches
14665 @option{-P}, @option{-U} and possibly the main unit when one is interested
14666 in its closure. For instance,
14670 will compute the metrics for all the immediate units of project
14673 gnat metric -Pproj -U
14675 will compute the metrics for all the units of the closure of projects
14676 rooted at @code{proj}.
14678 gnat metric -Pproj -U main_unit
14680 will compute the metrics for the closure of units rooted at
14681 @code{main_unit}. This last possibility relies implicitly
14682 on @command{gnatbind}'s option @option{-R}.
14684 @c **********************
14685 @node An Extended Example
14686 @section An Extended Example
14689 Suppose that we have two programs, @var{prog1} and @var{prog2},
14690 whose sources are in corresponding directories. We would like
14691 to build them with a single @command{gnatmake} command, and we want to place
14692 their object files into @file{build} subdirectories of the source directories.
14693 Furthermore, we want to have to have two separate subdirectories
14694 in @file{build} -- @file{release} and @file{debug} -- which will contain
14695 the object files compiled with different set of compilation flags.
14697 In other words, we have the following structure:
14714 Here are the project files that we must place in a directory @file{main}
14715 to maintain this structure:
14719 @item We create a @code{Common} project with a package @code{Compiler} that
14720 specifies the compilation ^switches^switches^:
14725 @b{project} Common @b{is}
14727 @b{for} Source_Dirs @b{use} (); -- No source files
14731 @b{type} Build_Type @b{is} ("release", "debug");
14732 Build : Build_Type := External ("BUILD", "debug");
14735 @b{package} Compiler @b{is}
14736 @b{case} Build @b{is}
14737 @b{when} "release" =>
14738 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14739 @b{use} ("^-O2^-O2^");
14740 @b{when} "debug" =>
14741 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14742 @b{use} ("^-g^-g^");
14750 @item We create separate projects for the two programs:
14757 @b{project} Prog1 @b{is}
14759 @b{for} Source_Dirs @b{use} ("prog1");
14760 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
14762 @b{package} Compiler @b{renames} Common.Compiler;
14773 @b{project} Prog2 @b{is}
14775 @b{for} Source_Dirs @b{use} ("prog2");
14776 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
14778 @b{package} Compiler @b{renames} Common.Compiler;
14784 @item We create a wrapping project @code{Main}:
14793 @b{project} Main @b{is}
14795 @b{package} Compiler @b{renames} Common.Compiler;
14801 @item Finally we need to create a dummy procedure that @code{with}s (either
14802 explicitly or implicitly) all the sources of our two programs.
14807 Now we can build the programs using the command
14810 gnatmake ^-P^/PROJECT_FILE=^main dummy
14814 for the Debug mode, or
14818 gnatmake -Pmain -XBUILD=release
14824 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
14829 for the Release mode.
14831 @c ********************************
14832 @c * Project File Complete Syntax *
14833 @c ********************************
14835 @node Project File Complete Syntax
14836 @section Project File Complete Syntax
14840 context_clause project_declaration
14846 @b{with} path_name @{ , path_name @} ;
14851 project_declaration ::=
14852 simple_project_declaration | project_extension
14854 simple_project_declaration ::=
14855 @b{project} <project_>simple_name @b{is}
14856 @{declarative_item@}
14857 @b{end} <project_>simple_name;
14859 project_extension ::=
14860 @b{project} <project_>simple_name @b{extends} path_name @b{is}
14861 @{declarative_item@}
14862 @b{end} <project_>simple_name;
14864 declarative_item ::=
14865 package_declaration |
14866 typed_string_declaration |
14867 other_declarative_item
14869 package_declaration ::=
14870 package_spec | package_renaming
14873 @b{package} package_identifier @b{is}
14874 @{simple_declarative_item@}
14875 @b{end} package_identifier ;
14877 package_identifier ::=
14878 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
14879 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
14880 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
14882 package_renaming ::==
14883 @b{package} package_identifier @b{renames}
14884 <project_>simple_name.package_identifier ;
14886 typed_string_declaration ::=
14887 @b{type} <typed_string_>_simple_name @b{is}
14888 ( string_literal @{, string_literal@} );
14890 other_declarative_item ::=
14891 attribute_declaration |
14892 typed_variable_declaration |
14893 variable_declaration |
14896 attribute_declaration ::=
14897 full_associative_array_declaration |
14898 @b{for} attribute_designator @b{use} expression ;
14900 full_associative_array_declaration ::=
14901 @b{for} <associative_array_attribute_>simple_name @b{use}
14902 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
14904 attribute_designator ::=
14905 <simple_attribute_>simple_name |
14906 <associative_array_attribute_>simple_name ( string_literal )
14908 typed_variable_declaration ::=
14909 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
14911 variable_declaration ::=
14912 <variable_>simple_name := expression;
14922 attribute_reference
14928 ( <string_>expression @{ , <string_>expression @} )
14931 @b{external} ( string_literal [, string_literal] )
14933 attribute_reference ::=
14934 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
14936 attribute_prefix ::=
14938 <project_>simple_name | package_identifier |
14939 <project_>simple_name . package_identifier
14941 case_construction ::=
14942 @b{case} <typed_variable_>name @b{is}
14947 @b{when} discrete_choice_list =>
14948 @{case_construction | attribute_declaration@}
14950 discrete_choice_list ::=
14951 string_literal @{| string_literal@} |
14955 simple_name @{. simple_name@}
14958 identifier (same as Ada)
14962 @node The Cross-Referencing Tools gnatxref and gnatfind
14963 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
14968 The compiler generates cross-referencing information (unless
14969 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
14970 This information indicates where in the source each entity is declared and
14971 referenced. Note that entities in package Standard are not included, but
14972 entities in all other predefined units are included in the output.
14974 Before using any of these two tools, you need to compile successfully your
14975 application, so that GNAT gets a chance to generate the cross-referencing
14978 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
14979 information to provide the user with the capability to easily locate the
14980 declaration and references to an entity. These tools are quite similar,
14981 the difference being that @code{gnatfind} is intended for locating
14982 definitions and/or references to a specified entity or entities, whereas
14983 @code{gnatxref} is oriented to generating a full report of all
14986 To use these tools, you must not compile your application using the
14987 @option{-gnatx} switch on the @command{gnatmake} command line
14988 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
14989 information will not be generated.
14991 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
14992 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
14995 * gnatxref Switches::
14996 * gnatfind Switches::
14997 * Project Files for gnatxref and gnatfind::
14998 * Regular Expressions in gnatfind and gnatxref::
14999 * Examples of gnatxref Usage::
15000 * Examples of gnatfind Usage::
15003 @node gnatxref Switches
15004 @section @code{gnatxref} Switches
15007 The command invocation for @code{gnatxref} is:
15009 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15018 identifies the source files for which a report is to be generated. The
15019 ``with''ed units will be processed too. You must provide at least one file.
15021 These file names are considered to be regular expressions, so for instance
15022 specifying @file{source*.adb} is the same as giving every file in the current
15023 directory whose name starts with @file{source} and whose extension is
15026 You shouldn't specify any directory name, just base names. @command{gnatxref}
15027 and @command{gnatfind} will be able to locate these files by themselves using
15028 the source path. If you specify directories, no result is produced.
15033 The switches can be:
15037 @cindex @option{--version} @command{gnatxref}
15038 Display Copyright and version, then exit disregarding all other options.
15041 @cindex @option{--help} @command{gnatxref}
15042 If @option{--version} was not used, display usage, then exit disregarding
15045 @item ^-a^/ALL_FILES^
15046 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15047 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15048 the read-only files found in the library search path. Otherwise, these files
15049 will be ignored. This option can be used to protect Gnat sources or your own
15050 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15051 much faster, and their output much smaller. Read-only here refers to access
15052 or permissions status in the file system for the current user.
15055 @cindex @option{-aIDIR} (@command{gnatxref})
15056 When looking for source files also look in directory DIR. The order in which
15057 source file search is undertaken is the same as for @command{gnatmake}.
15060 @cindex @option{-aODIR} (@command{gnatxref})
15061 When searching for library and object files, look in directory
15062 DIR. The order in which library files are searched is the same as for
15063 @command{gnatmake}.
15066 @cindex @option{-nostdinc} (@command{gnatxref})
15067 Do not look for sources in the system default directory.
15070 @cindex @option{-nostdlib} (@command{gnatxref})
15071 Do not look for library files in the system default directory.
15073 @item --RTS=@var{rts-path}
15074 @cindex @option{--RTS} (@command{gnatxref})
15075 Specifies the default location of the runtime library. Same meaning as the
15076 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15078 @item ^-d^/DERIVED_TYPES^
15079 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15080 If this switch is set @code{gnatxref} will output the parent type
15081 reference for each matching derived types.
15083 @item ^-f^/FULL_PATHNAME^
15084 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15085 If this switch is set, the output file names will be preceded by their
15086 directory (if the file was found in the search path). If this switch is
15087 not set, the directory will not be printed.
15089 @item ^-g^/IGNORE_LOCALS^
15090 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15091 If this switch is set, information is output only for library-level
15092 entities, ignoring local entities. The use of this switch may accelerate
15093 @code{gnatfind} and @code{gnatxref}.
15096 @cindex @option{-IDIR} (@command{gnatxref})
15097 Equivalent to @samp{-aODIR -aIDIR}.
15100 @cindex @option{-pFILE} (@command{gnatxref})
15101 Specify a project file to use @xref{Project Files}.
15102 If you need to use the @file{.gpr}
15103 project files, you should use gnatxref through the GNAT driver
15104 (@command{gnat xref -Pproject}).
15106 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15107 project file in the current directory.
15109 If a project file is either specified or found by the tools, then the content
15110 of the source directory and object directory lines are added as if they
15111 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15112 and @samp{^-aO^OBJECT_SEARCH^}.
15114 Output only unused symbols. This may be really useful if you give your
15115 main compilation unit on the command line, as @code{gnatxref} will then
15116 display every unused entity and 'with'ed package.
15120 Instead of producing the default output, @code{gnatxref} will generate a
15121 @file{tags} file that can be used by vi. For examples how to use this
15122 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15123 to the standard output, thus you will have to redirect it to a file.
15129 All these switches may be in any order on the command line, and may even
15130 appear after the file names. They need not be separated by spaces, thus
15131 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15132 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15134 @node gnatfind Switches
15135 @section @code{gnatfind} Switches
15138 The command line for @code{gnatfind} is:
15141 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15142 @r{[}@var{file1} @var{file2} @dots{}]
15150 An entity will be output only if it matches the regular expression found
15151 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15153 Omitting the pattern is equivalent to specifying @samp{*}, which
15154 will match any entity. Note that if you do not provide a pattern, you
15155 have to provide both a sourcefile and a line.
15157 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15158 for matching purposes. At the current time there is no support for
15159 8-bit codes other than Latin-1, or for wide characters in identifiers.
15162 @code{gnatfind} will look for references, bodies or declarations
15163 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15164 and column @var{column}. See @ref{Examples of gnatfind Usage}
15165 for syntax examples.
15168 is a decimal integer identifying the line number containing
15169 the reference to the entity (or entities) to be located.
15172 is a decimal integer identifying the exact location on the
15173 line of the first character of the identifier for the
15174 entity reference. Columns are numbered from 1.
15176 @item file1 file2 @dots{}
15177 The search will be restricted to these source files. If none are given, then
15178 the search will be done for every library file in the search path.
15179 These file must appear only after the pattern or sourcefile.
15181 These file names are considered to be regular expressions, so for instance
15182 specifying @file{source*.adb} is the same as giving every file in the current
15183 directory whose name starts with @file{source} and whose extension is
15186 The location of the spec of the entity will always be displayed, even if it
15187 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15188 occurrences of the entity in the separate units of the ones given on the
15189 command line will also be displayed.
15191 Note that if you specify at least one file in this part, @code{gnatfind} may
15192 sometimes not be able to find the body of the subprograms.
15197 At least one of 'sourcefile' or 'pattern' has to be present on
15200 The following switches are available:
15204 @cindex @option{--version} @command{gnatfind}
15205 Display Copyright and version, then exit disregarding all other options.
15208 @cindex @option{--help} @command{gnatfind}
15209 If @option{--version} was not used, display usage, then exit disregarding
15212 @item ^-a^/ALL_FILES^
15213 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15214 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15215 the read-only files found in the library search path. Otherwise, these files
15216 will be ignored. This option can be used to protect Gnat sources or your own
15217 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15218 much faster, and their output much smaller. Read-only here refers to access
15219 or permission status in the file system for the current user.
15222 @cindex @option{-aIDIR} (@command{gnatfind})
15223 When looking for source files also look in directory DIR. The order in which
15224 source file search is undertaken is the same as for @command{gnatmake}.
15227 @cindex @option{-aODIR} (@command{gnatfind})
15228 When searching for library and object files, look in directory
15229 DIR. The order in which library files are searched is the same as for
15230 @command{gnatmake}.
15233 @cindex @option{-nostdinc} (@command{gnatfind})
15234 Do not look for sources in the system default directory.
15237 @cindex @option{-nostdlib} (@command{gnatfind})
15238 Do not look for library files in the system default directory.
15240 @item --RTS=@var{rts-path}
15241 @cindex @option{--RTS} (@command{gnatfind})
15242 Specifies the default location of the runtime library. Same meaning as the
15243 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15245 @item ^-d^/DERIVED_TYPE_INFORMATION^
15246 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15247 If this switch is set, then @code{gnatfind} will output the parent type
15248 reference for each matching derived types.
15250 @item ^-e^/EXPRESSIONS^
15251 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15252 By default, @code{gnatfind} accept the simple regular expression set for
15253 @samp{pattern}. If this switch is set, then the pattern will be
15254 considered as full Unix-style regular expression.
15256 @item ^-f^/FULL_PATHNAME^
15257 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15258 If this switch is set, the output file names will be preceded by their
15259 directory (if the file was found in the search path). If this switch is
15260 not set, the directory will not be printed.
15262 @item ^-g^/IGNORE_LOCALS^
15263 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15264 If this switch is set, information is output only for library-level
15265 entities, ignoring local entities. The use of this switch may accelerate
15266 @code{gnatfind} and @code{gnatxref}.
15269 @cindex @option{-IDIR} (@command{gnatfind})
15270 Equivalent to @samp{-aODIR -aIDIR}.
15273 @cindex @option{-pFILE} (@command{gnatfind})
15274 Specify a project file (@pxref{Project Files}) to use.
15275 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15276 project file in the current directory.
15278 If a project file is either specified or found by the tools, then the content
15279 of the source directory and object directory lines are added as if they
15280 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15281 @samp{^-aO^/OBJECT_SEARCH^}.
15283 @item ^-r^/REFERENCES^
15284 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15285 By default, @code{gnatfind} will output only the information about the
15286 declaration, body or type completion of the entities. If this switch is
15287 set, the @code{gnatfind} will locate every reference to the entities in
15288 the files specified on the command line (or in every file in the search
15289 path if no file is given on the command line).
15291 @item ^-s^/PRINT_LINES^
15292 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15293 If this switch is set, then @code{gnatfind} will output the content
15294 of the Ada source file lines were the entity was found.
15296 @item ^-t^/TYPE_HIERARCHY^
15297 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15298 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15299 the specified type. It act like -d option but recursively from parent
15300 type to parent type. When this switch is set it is not possible to
15301 specify more than one file.
15306 All these switches may be in any order on the command line, and may even
15307 appear after the file names. They need not be separated by spaces, thus
15308 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15309 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15311 As stated previously, gnatfind will search in every directory in the
15312 search path. You can force it to look only in the current directory if
15313 you specify @code{*} at the end of the command line.
15315 @node Project Files for gnatxref and gnatfind
15316 @section Project Files for @command{gnatxref} and @command{gnatfind}
15319 Project files allow a programmer to specify how to compile its
15320 application, where to find sources, etc. These files are used
15322 primarily by GPS, but they can also be used
15325 @code{gnatxref} and @code{gnatfind}.
15327 A project file name must end with @file{.gpr}. If a single one is
15328 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15329 extract the information from it. If multiple project files are found, none of
15330 them is read, and you have to use the @samp{-p} switch to specify the one
15333 The following lines can be included, even though most of them have default
15334 values which can be used in most cases.
15335 The lines can be entered in any order in the file.
15336 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15337 each line. If you have multiple instances, only the last one is taken into
15342 [default: @code{"^./^[]^"}]
15343 specifies a directory where to look for source files. Multiple @code{src_dir}
15344 lines can be specified and they will be searched in the order they
15348 [default: @code{"^./^[]^"}]
15349 specifies a directory where to look for object and library files. Multiple
15350 @code{obj_dir} lines can be specified, and they will be searched in the order
15353 @item comp_opt=SWITCHES
15354 [default: @code{""}]
15355 creates a variable which can be referred to subsequently by using
15356 the @code{$@{comp_opt@}} notation. This is intended to store the default
15357 switches given to @command{gnatmake} and @command{gcc}.
15359 @item bind_opt=SWITCHES
15360 [default: @code{""}]
15361 creates a variable which can be referred to subsequently by using
15362 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15363 switches given to @command{gnatbind}.
15365 @item link_opt=SWITCHES
15366 [default: @code{""}]
15367 creates a variable which can be referred to subsequently by using
15368 the @samp{$@{link_opt@}} notation. This is intended to store the default
15369 switches given to @command{gnatlink}.
15371 @item main=EXECUTABLE
15372 [default: @code{""}]
15373 specifies the name of the executable for the application. This variable can
15374 be referred to in the following lines by using the @samp{$@{main@}} notation.
15377 @item comp_cmd=COMMAND
15378 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15381 @item comp_cmd=COMMAND
15382 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15384 specifies the command used to compile a single file in the application.
15387 @item make_cmd=COMMAND
15388 [default: @code{"GNAT MAKE $@{main@}
15389 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15390 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15391 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15394 @item make_cmd=COMMAND
15395 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15396 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15397 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15399 specifies the command used to recompile the whole application.
15401 @item run_cmd=COMMAND
15402 [default: @code{"$@{main@}"}]
15403 specifies the command used to run the application.
15405 @item debug_cmd=COMMAND
15406 [default: @code{"gdb $@{main@}"}]
15407 specifies the command used to debug the application
15412 @command{gnatxref} and @command{gnatfind} only take into account the
15413 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15415 @node Regular Expressions in gnatfind and gnatxref
15416 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15419 As specified in the section about @command{gnatfind}, the pattern can be a
15420 regular expression. Actually, there are to set of regular expressions
15421 which are recognized by the program:
15424 @item globbing patterns
15425 These are the most usual regular expression. They are the same that you
15426 generally used in a Unix shell command line, or in a DOS session.
15428 Here is a more formal grammar:
15435 term ::= elmt -- matches elmt
15436 term ::= elmt elmt -- concatenation (elmt then elmt)
15437 term ::= * -- any string of 0 or more characters
15438 term ::= ? -- matches any character
15439 term ::= [char @{char@}] -- matches any character listed
15440 term ::= [char - char] -- matches any character in range
15444 @item full regular expression
15445 The second set of regular expressions is much more powerful. This is the
15446 type of regular expressions recognized by utilities such a @file{grep}.
15448 The following is the form of a regular expression, expressed in Ada
15449 reference manual style BNF is as follows
15456 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15458 term ::= item @{item@} -- concatenation (item then item)
15460 item ::= elmt -- match elmt
15461 item ::= elmt * -- zero or more elmt's
15462 item ::= elmt + -- one or more elmt's
15463 item ::= elmt ? -- matches elmt or nothing
15466 elmt ::= nschar -- matches given character
15467 elmt ::= [nschar @{nschar@}] -- matches any character listed
15468 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15469 elmt ::= [char - char] -- matches chars in given range
15470 elmt ::= \ char -- matches given character
15471 elmt ::= . -- matches any single character
15472 elmt ::= ( regexp ) -- parens used for grouping
15474 char ::= any character, including special characters
15475 nschar ::= any character except ()[].*+?^^^
15479 Following are a few examples:
15483 will match any of the two strings @samp{abcde} and @samp{fghi},
15486 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15487 @samp{abcccd}, and so on,
15490 will match any string which has only lowercase characters in it (and at
15491 least one character.
15496 @node Examples of gnatxref Usage
15497 @section Examples of @code{gnatxref} Usage
15499 @subsection General Usage
15502 For the following examples, we will consider the following units:
15504 @smallexample @c ada
15510 3: procedure Foo (B : in Integer);
15517 1: package body Main is
15518 2: procedure Foo (B : in Integer) is
15529 2: procedure Print (B : Integer);
15538 The first thing to do is to recompile your application (for instance, in
15539 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15540 the cross-referencing information.
15541 You can then issue any of the following commands:
15543 @item gnatxref main.adb
15544 @code{gnatxref} generates cross-reference information for main.adb
15545 and every unit 'with'ed by main.adb.
15547 The output would be:
15555 Decl: main.ads 3:20
15556 Body: main.adb 2:20
15557 Ref: main.adb 4:13 5:13 6:19
15560 Ref: main.adb 6:8 7:8
15570 Decl: main.ads 3:15
15571 Body: main.adb 2:15
15574 Body: main.adb 1:14
15577 Ref: main.adb 6:12 7:12
15581 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15582 its body is in main.adb, line 1, column 14 and is not referenced any where.
15584 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15585 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15587 @item gnatxref package1.adb package2.ads
15588 @code{gnatxref} will generates cross-reference information for
15589 package1.adb, package2.ads and any other package 'with'ed by any
15595 @subsection Using gnatxref with vi
15597 @code{gnatxref} can generate a tags file output, which can be used
15598 directly from @command{vi}. Note that the standard version of @command{vi}
15599 will not work properly with overloaded symbols. Consider using another
15600 free implementation of @command{vi}, such as @command{vim}.
15603 $ gnatxref -v gnatfind.adb > tags
15607 will generate the tags file for @code{gnatfind} itself (if the sources
15608 are in the search path!).
15610 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15611 (replacing @var{entity} by whatever you are looking for), and vi will
15612 display a new file with the corresponding declaration of entity.
15615 @node Examples of gnatfind Usage
15616 @section Examples of @code{gnatfind} Usage
15620 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15621 Find declarations for all entities xyz referenced at least once in
15622 main.adb. The references are search in every library file in the search
15625 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15628 The output will look like:
15630 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15631 ^directory/^[directory]^main.adb:24:10: xyz <= body
15632 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15636 that is to say, one of the entities xyz found in main.adb is declared at
15637 line 12 of main.ads (and its body is in main.adb), and another one is
15638 declared at line 45 of foo.ads
15640 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15641 This is the same command as the previous one, instead @code{gnatfind} will
15642 display the content of the Ada source file lines.
15644 The output will look like:
15647 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15649 ^directory/^[directory]^main.adb:24:10: xyz <= body
15651 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15656 This can make it easier to find exactly the location your are looking
15659 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
15660 Find references to all entities containing an x that are
15661 referenced on line 123 of main.ads.
15662 The references will be searched only in main.ads and foo.adb.
15664 @item gnatfind main.ads:123
15665 Find declarations and bodies for all entities that are referenced on
15666 line 123 of main.ads.
15668 This is the same as @code{gnatfind "*":main.adb:123}.
15670 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
15671 Find the declaration for the entity referenced at column 45 in
15672 line 123 of file main.adb in directory mydir. Note that it
15673 is usual to omit the identifier name when the column is given,
15674 since the column position identifies a unique reference.
15676 The column has to be the beginning of the identifier, and should not
15677 point to any character in the middle of the identifier.
15681 @c *********************************
15682 @node The GNAT Pretty-Printer gnatpp
15683 @chapter The GNAT Pretty-Printer @command{gnatpp}
15685 @cindex Pretty-Printer
15688 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
15689 for source reformatting / pretty-printing.
15690 It takes an Ada source file as input and generates a reformatted
15692 You can specify various style directives via switches; e.g.,
15693 identifier case conventions, rules of indentation, and comment layout.
15695 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
15696 tree for the input source and thus requires the input to be syntactically and
15697 semantically legal.
15698 If this condition is not met, @command{gnatpp} will terminate with an
15699 error message; no output file will be generated.
15701 If the source files presented to @command{gnatpp} contain
15702 preprocessing directives, then the output file will
15703 correspond to the generated source after all
15704 preprocessing is carried out. There is no way
15705 using @command{gnatpp} to obtain pretty printed files that
15706 include the preprocessing directives.
15708 If the compilation unit
15709 contained in the input source depends semantically upon units located
15710 outside the current directory, you have to provide the source search path
15711 when invoking @command{gnatpp}, if these units are contained in files with
15712 names that do not follow the GNAT file naming rules, you have to provide
15713 the configuration file describing the corresponding naming scheme;
15714 see the description of the @command{gnatpp}
15715 switches below. Another possibility is to use a project file and to
15716 call @command{gnatpp} through the @command{gnat} driver
15718 The @command{gnatpp} command has the form
15721 $ gnatpp @ovar{switches} @var{filename}
15728 @var{switches} is an optional sequence of switches defining such properties as
15729 the formatting rules, the source search path, and the destination for the
15733 @var{filename} is the name (including the extension) of the source file to
15734 reformat; ``wildcards'' or several file names on the same gnatpp command are
15735 allowed. The file name may contain path information; it does not have to
15736 follow the GNAT file naming rules
15740 * Switches for gnatpp::
15741 * Formatting Rules::
15744 @node Switches for gnatpp
15745 @section Switches for @command{gnatpp}
15748 The following subsections describe the various switches accepted by
15749 @command{gnatpp}, organized by category.
15752 You specify a switch by supplying a name and generally also a value.
15753 In many cases the values for a switch with a given name are incompatible with
15755 (for example the switch that controls the casing of a reserved word may have
15756 exactly one value: upper case, lower case, or
15757 mixed case) and thus exactly one such switch can be in effect for an
15758 invocation of @command{gnatpp}.
15759 If more than one is supplied, the last one is used.
15760 However, some values for the same switch are mutually compatible.
15761 You may supply several such switches to @command{gnatpp}, but then
15762 each must be specified in full, with both the name and the value.
15763 Abbreviated forms (the name appearing once, followed by each value) are
15765 For example, to set
15766 the alignment of the assignment delimiter both in declarations and in
15767 assignment statements, you must write @option{-A2A3}
15768 (or @option{-A2 -A3}), but not @option{-A23}.
15772 In many cases the set of options for a given qualifier are incompatible with
15773 each other (for example the qualifier that controls the casing of a reserved
15774 word may have exactly one option, which specifies either upper case, lower
15775 case, or mixed case), and thus exactly one such option can be in effect for
15776 an invocation of @command{gnatpp}.
15777 If more than one is supplied, the last one is used.
15778 However, some qualifiers have options that are mutually compatible,
15779 and then you may then supply several such options when invoking
15783 In most cases, it is obvious whether or not the
15784 ^values for a switch with a given name^options for a given qualifier^
15785 are compatible with each other.
15786 When the semantics might not be evident, the summaries below explicitly
15787 indicate the effect.
15790 * Alignment Control::
15792 * Construct Layout Control::
15793 * General Text Layout Control::
15794 * Other Formatting Options::
15795 * Setting the Source Search Path::
15796 * Output File Control::
15797 * Other gnatpp Switches::
15800 @node Alignment Control
15801 @subsection Alignment Control
15802 @cindex Alignment control in @command{gnatpp}
15805 Programs can be easier to read if certain constructs are vertically aligned.
15806 By default all alignments are set ON.
15807 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
15808 OFF, and then use one or more of the other
15809 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
15810 to activate alignment for specific constructs.
15813 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
15817 Set all alignments to ON
15820 @item ^-A0^/ALIGN=OFF^
15821 Set all alignments to OFF
15823 @item ^-A1^/ALIGN=COLONS^
15824 Align @code{:} in declarations
15826 @item ^-A2^/ALIGN=DECLARATIONS^
15827 Align @code{:=} in initializations in declarations
15829 @item ^-A3^/ALIGN=STATEMENTS^
15830 Align @code{:=} in assignment statements
15832 @item ^-A4^/ALIGN=ARROWS^
15833 Align @code{=>} in associations
15835 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
15836 Align @code{at} keywords in the component clauses in record
15837 representation clauses
15841 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
15844 @node Casing Control
15845 @subsection Casing Control
15846 @cindex Casing control in @command{gnatpp}
15849 @command{gnatpp} allows you to specify the casing for reserved words,
15850 pragma names, attribute designators and identifiers.
15851 For identifiers you may define a
15852 general rule for name casing but also override this rule
15853 via a set of dictionary files.
15855 Three types of casing are supported: lower case, upper case, and mixed case.
15856 Lower and upper case are self-explanatory (but since some letters in
15857 Latin1 and other GNAT-supported character sets
15858 exist only in lower-case form, an upper case conversion will have no
15860 ``Mixed case'' means that the first letter, and also each letter immediately
15861 following an underscore, are converted to their uppercase forms;
15862 all the other letters are converted to their lowercase forms.
15865 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
15866 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
15867 Attribute designators are lower case
15869 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
15870 Attribute designators are upper case
15872 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
15873 Attribute designators are mixed case (this is the default)
15875 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
15876 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
15877 Keywords (technically, these are known in Ada as @emph{reserved words}) are
15878 lower case (this is the default)
15880 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
15881 Keywords are upper case
15883 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
15884 @item ^-nD^/NAME_CASING=AS_DECLARED^
15885 Name casing for defining occurrences are as they appear in the source file
15886 (this is the default)
15888 @item ^-nU^/NAME_CASING=UPPER_CASE^
15889 Names are in upper case
15891 @item ^-nL^/NAME_CASING=LOWER_CASE^
15892 Names are in lower case
15894 @item ^-nM^/NAME_CASING=MIXED_CASE^
15895 Names are in mixed case
15897 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
15898 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
15899 Pragma names are lower case
15901 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
15902 Pragma names are upper case
15904 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
15905 Pragma names are mixed case (this is the default)
15907 @item ^-D@var{file}^/DICTIONARY=@var{file}^
15908 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
15909 Use @var{file} as a @emph{dictionary file} that defines
15910 the casing for a set of specified names,
15911 thereby overriding the effect on these names by
15912 any explicit or implicit
15913 ^-n^/NAME_CASING^ switch.
15914 To supply more than one dictionary file,
15915 use ^several @option{-D} switches^a list of files as options^.
15918 @option{gnatpp} implicitly uses a @emph{default dictionary file}
15919 to define the casing for the Ada predefined names and
15920 the names declared in the GNAT libraries.
15922 @item ^-D-^/SPECIFIC_CASING^
15923 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
15924 Do not use the default dictionary file;
15925 instead, use the casing
15926 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
15931 The structure of a dictionary file, and details on the conventions
15932 used in the default dictionary file, are defined in @ref{Name Casing}.
15934 The @option{^-D-^/SPECIFIC_CASING^} and
15935 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
15938 @node Construct Layout Control
15939 @subsection Construct Layout Control
15940 @cindex Layout control in @command{gnatpp}
15943 This group of @command{gnatpp} switches controls the layout of comments and
15944 complex syntactic constructs. See @ref{Formatting Comments} for details
15948 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
15949 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
15950 All the comments remain unchanged
15952 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
15953 GNAT-style comment line indentation (this is the default).
15955 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
15956 Reference-manual comment line indentation.
15958 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
15959 GNAT-style comment beginning
15961 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
15962 Reformat comment blocks
15964 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
15965 Keep unchanged special form comments
15967 Reformat comment blocks
15969 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
15970 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
15971 GNAT-style layout (this is the default)
15973 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
15976 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
15979 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
15981 All the VT characters are removed from the comment text. All the HT characters
15982 are expanded with the sequences of space characters to get to the next tab
15985 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
15986 @item ^--no-separate-is^/NO_SEPARATE_IS^
15987 Do not place the keyword @code{is} on a separate line in a subprogram body in
15988 case if the spec occupies more then one line.
15990 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
15991 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
15992 Place the keyword @code{loop} in FOR and WHILE loop statements and the
15993 keyword @code{then} in IF statements on a separate line.
15995 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
15996 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
15997 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
15998 keyword @code{then} in IF statements on a separate line. This option is
15999 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16001 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16002 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16003 Start each USE clause in a context clause from a separate line.
16005 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16006 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16007 Use a separate line for a loop or block statement name, but do not use an extra
16008 indentation level for the statement itself.
16014 The @option{-c1} and @option{-c2} switches are incompatible.
16015 The @option{-c3} and @option{-c4} switches are compatible with each other and
16016 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16017 the other comment formatting switches.
16019 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16024 For the @option{/COMMENTS_LAYOUT} qualifier:
16027 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16029 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16030 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16034 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16035 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16038 @node General Text Layout Control
16039 @subsection General Text Layout Control
16042 These switches allow control over line length and indentation.
16045 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16046 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16047 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16049 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16050 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16051 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16053 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16054 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16055 Indentation level for continuation lines (relative to the line being
16056 continued), @var{nnn} from 1@dots{}9.
16058 value is one less then the (normal) indentation level, unless the
16059 indentation is set to 1 (in which case the default value for continuation
16060 line indentation is also 1)
16063 @node Other Formatting Options
16064 @subsection Other Formatting Options
16067 These switches control the inclusion of missing end/exit labels, and
16068 the indentation level in @b{case} statements.
16071 @item ^-e^/NO_MISSED_LABELS^
16072 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16073 Do not insert missing end/exit labels. An end label is the name of
16074 a construct that may optionally be repeated at the end of the
16075 construct's declaration;
16076 e.g., the names of packages, subprograms, and tasks.
16077 An exit label is the name of a loop that may appear as target
16078 of an exit statement within the loop.
16079 By default, @command{gnatpp} inserts these end/exit labels when
16080 they are absent from the original source. This option suppresses such
16081 insertion, so that the formatted source reflects the original.
16083 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16084 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16085 Insert a Form Feed character after a pragma Page.
16087 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16088 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16089 Do not use an additional indentation level for @b{case} alternatives
16090 and variants if there are @var{nnn} or more (the default
16092 If @var{nnn} is 0, an additional indentation level is
16093 used for @b{case} alternatives and variants regardless of their number.
16096 @node Setting the Source Search Path
16097 @subsection Setting the Source Search Path
16100 To define the search path for the input source file, @command{gnatpp}
16101 uses the same switches as the GNAT compiler, with the same effects.
16104 @item ^-I^/SEARCH=^@var{dir}
16105 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16106 The same as the corresponding gcc switch
16108 @item ^-I-^/NOCURRENT_DIRECTORY^
16109 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16110 The same as the corresponding gcc switch
16112 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16113 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16114 The same as the corresponding gcc switch
16116 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16117 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16118 The same as the corresponding gcc switch
16122 @node Output File Control
16123 @subsection Output File Control
16126 By default the output is sent to the file whose name is obtained by appending
16127 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16128 (if the file with this name already exists, it is unconditionally overwritten).
16129 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16130 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16132 The output may be redirected by the following switches:
16135 @item ^-pipe^/STANDARD_OUTPUT^
16136 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16137 Send the output to @code{Standard_Output}
16139 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16140 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16141 Write the output into @var{output_file}.
16142 If @var{output_file} already exists, @command{gnatpp} terminates without
16143 reading or processing the input file.
16145 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16146 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16147 Write the output into @var{output_file}, overwriting the existing file
16148 (if one is present).
16150 @item ^-r^/REPLACE^
16151 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16152 Replace the input source file with the reformatted output, and copy the
16153 original input source into the file whose name is obtained by appending the
16154 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16155 If a file with this name already exists, @command{gnatpp} terminates without
16156 reading or processing the input file.
16158 @item ^-rf^/OVERRIDING_REPLACE^
16159 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16160 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16161 already exists, it is overwritten.
16163 @item ^-rnb^/REPLACE_NO_BACKUP^
16164 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16165 Replace the input source file with the reformatted output without
16166 creating any backup copy of the input source.
16168 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16169 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16170 Specifies the format of the reformatted output file. The @var{xxx}
16171 ^string specified with the switch^option^ may be either
16173 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16174 @item ``@option{^crlf^CRLF^}''
16175 the same as @option{^crlf^CRLF^}
16176 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16177 @item ``@option{^lf^LF^}''
16178 the same as @option{^unix^UNIX^}
16181 @item ^-W^/RESULT_ENCODING=^@var{e}
16182 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16183 Specify the wide character encoding method used to write the code in the
16185 @var{e} is one of the following:
16193 Upper half encoding
16195 @item ^s^SHIFT_JIS^
16205 Brackets encoding (default value)
16211 Options @option{^-pipe^/STANDARD_OUTPUT^},
16212 @option{^-o^/OUTPUT^} and
16213 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16214 contains only one file to reformat.
16216 @option{^--eol^/END_OF_LINE^}
16218 @option{^-W^/RESULT_ENCODING^}
16219 cannot be used together
16220 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16222 @node Other gnatpp Switches
16223 @subsection Other @code{gnatpp} Switches
16226 The additional @command{gnatpp} switches are defined in this subsection.
16229 @item ^-files @var{filename}^/FILES=@var{output_file}^
16230 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16231 Take the argument source files from the specified file. This file should be an
16232 ordinary textual file containing file names separated by spaces or
16233 line breaks. You can use this switch more then once in the same call to
16234 @command{gnatpp}. You also can combine this switch with explicit list of
16237 @item ^-v^/VERBOSE^
16238 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16240 @command{gnatpp} generates version information and then
16241 a trace of the actions it takes to produce or obtain the ASIS tree.
16243 @item ^-w^/WARNINGS^
16244 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16246 @command{gnatpp} generates a warning whenever it cannot provide
16247 a required layout in the result source.
16250 @node Formatting Rules
16251 @section Formatting Rules
16254 The following subsections show how @command{gnatpp} treats ``white space'',
16255 comments, program layout, and name casing.
16256 They provide the detailed descriptions of the switches shown above.
16259 * White Space and Empty Lines::
16260 * Formatting Comments::
16261 * Construct Layout::
16265 @node White Space and Empty Lines
16266 @subsection White Space and Empty Lines
16269 @command{gnatpp} does not have an option to control space characters.
16270 It will add or remove spaces according to the style illustrated by the
16271 examples in the @cite{Ada Reference Manual}.
16273 The only format effectors
16274 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16275 that will appear in the output file are platform-specific line breaks,
16276 and also format effectors within (but not at the end of) comments.
16277 In particular, each horizontal tab character that is not inside
16278 a comment will be treated as a space and thus will appear in the
16279 output file as zero or more spaces depending on
16280 the reformatting of the line in which it appears.
16281 The only exception is a Form Feed character, which is inserted after a
16282 pragma @code{Page} when @option{-ff} is set.
16284 The output file will contain no lines with trailing ``white space'' (spaces,
16287 Empty lines in the original source are preserved
16288 only if they separate declarations or statements.
16289 In such contexts, a
16290 sequence of two or more empty lines is replaced by exactly one empty line.
16291 Note that a blank line will be removed if it separates two ``comment blocks''
16292 (a comment block is a sequence of whole-line comments).
16293 In order to preserve a visual separation between comment blocks, use an
16294 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16295 Likewise, if for some reason you wish to have a sequence of empty lines,
16296 use a sequence of empty comments instead.
16298 @node Formatting Comments
16299 @subsection Formatting Comments
16302 Comments in Ada code are of two kinds:
16305 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16306 ``white space'') on a line
16309 an @emph{end-of-line comment}, which follows some other Ada lexical element
16314 The indentation of a whole-line comment is that of either
16315 the preceding or following line in
16316 the formatted source, depending on switch settings as will be described below.
16318 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16319 between the end of the preceding Ada lexical element and the beginning
16320 of the comment as appear in the original source,
16321 unless either the comment has to be split to
16322 satisfy the line length limitation, or else the next line contains a
16323 whole line comment that is considered a continuation of this end-of-line
16324 comment (because it starts at the same position).
16326 cases, the start of the end-of-line comment is moved right to the nearest
16327 multiple of the indentation level.
16328 This may result in a ``line overflow'' (the right-shifted comment extending
16329 beyond the maximum line length), in which case the comment is split as
16332 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16333 (GNAT-style comment line indentation)
16334 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16335 (reference-manual comment line indentation).
16336 With reference-manual style, a whole-line comment is indented as if it
16337 were a declaration or statement at the same place
16338 (i.e., according to the indentation of the preceding line(s)).
16339 With GNAT style, a whole-line comment that is immediately followed by an
16340 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16341 word @b{begin}, is indented based on the construct that follows it.
16344 @smallexample @c ada
16356 Reference-manual indentation produces:
16358 @smallexample @c ada
16370 while GNAT-style indentation produces:
16372 @smallexample @c ada
16384 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16385 (GNAT style comment beginning) has the following
16390 For each whole-line comment that does not end with two hyphens,
16391 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16392 to ensure that there are at least two spaces between these hyphens and the
16393 first non-blank character of the comment.
16397 For an end-of-line comment, if in the original source the next line is a
16398 whole-line comment that starts at the same position
16399 as the end-of-line comment,
16400 then the whole-line comment (and all whole-line comments
16401 that follow it and that start at the same position)
16402 will start at this position in the output file.
16405 That is, if in the original source we have:
16407 @smallexample @c ada
16410 A := B + C; -- B must be in the range Low1..High1
16411 -- C must be in the range Low2..High2
16412 --B+C will be in the range Low1+Low2..High1+High2
16418 Then in the formatted source we get
16420 @smallexample @c ada
16423 A := B + C; -- B must be in the range Low1..High1
16424 -- C must be in the range Low2..High2
16425 -- B+C will be in the range Low1+Low2..High1+High2
16431 A comment that exceeds the line length limit will be split.
16433 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16434 the line belongs to a reformattable block, splitting the line generates a
16435 @command{gnatpp} warning.
16436 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16437 comments may be reformatted in typical
16438 word processor style (that is, moving words between lines and putting as
16439 many words in a line as possible).
16442 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16443 that has a special format (that is, a character that is neither a letter nor digit
16444 not white space nor line break immediately following the leading @code{--} of
16445 the comment) should be without any change moved from the argument source
16446 into reformatted source. This switch allows to preserve comments that are used
16447 as a special marks in the code (e.g.@: SPARK annotation).
16449 @node Construct Layout
16450 @subsection Construct Layout
16453 In several cases the suggested layout in the Ada Reference Manual includes
16454 an extra level of indentation that many programmers prefer to avoid. The
16455 affected cases include:
16459 @item Record type declaration (RM 3.8)
16461 @item Record representation clause (RM 13.5.1)
16463 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16465 @item Block statement in case if a block has a statement identifier (RM 5.6)
16469 In compact mode (when GNAT style layout or compact layout is set),
16470 the pretty printer uses one level of indentation instead
16471 of two. This is achieved in the record definition and record representation
16472 clause cases by putting the @code{record} keyword on the same line as the
16473 start of the declaration or representation clause, and in the block and loop
16474 case by putting the block or loop header on the same line as the statement
16478 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16479 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16480 layout on the one hand, and uncompact layout
16481 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16482 can be illustrated by the following examples:
16486 @multitable @columnfractions .5 .5
16487 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16490 @smallexample @c ada
16497 @smallexample @c ada
16506 @smallexample @c ada
16508 a at 0 range 0 .. 31;
16509 b at 4 range 0 .. 31;
16513 @smallexample @c ada
16516 a at 0 range 0 .. 31;
16517 b at 4 range 0 .. 31;
16522 @smallexample @c ada
16530 @smallexample @c ada
16540 @smallexample @c ada
16541 Clear : for J in 1 .. 10 loop
16546 @smallexample @c ada
16548 for J in 1 .. 10 loop
16559 GNAT style, compact layout Uncompact layout
16561 type q is record type q is
16562 a : integer; record
16563 b : integer; a : integer;
16564 end record; b : integer;
16567 for q use record for q use
16568 a at 0 range 0 .. 31; record
16569 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16570 end record; b at 4 range 0 .. 31;
16573 Block : declare Block :
16574 A : Integer := 3; declare
16575 begin A : Integer := 3;
16577 end Block; Proc (A, A);
16580 Clear : for J in 1 .. 10 loop Clear :
16581 A (J) := 0; for J in 1 .. 10 loop
16582 end loop Clear; A (J) := 0;
16589 A further difference between GNAT style layout and compact layout is that
16590 GNAT style layout inserts empty lines as separation for
16591 compound statements, return statements and bodies.
16593 Note that the layout specified by
16594 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16595 for named block and loop statements overrides the layout defined by these
16596 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16597 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16598 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16601 @subsection Name Casing
16604 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16605 the same casing as the corresponding defining identifier.
16607 You control the casing for defining occurrences via the
16608 @option{^-n^/NAME_CASING^} switch.
16610 With @option{-nD} (``as declared'', which is the default),
16613 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16615 defining occurrences appear exactly as in the source file
16616 where they are declared.
16617 The other ^values for this switch^options for this qualifier^ ---
16618 @option{^-nU^UPPER_CASE^},
16619 @option{^-nL^LOWER_CASE^},
16620 @option{^-nM^MIXED_CASE^} ---
16622 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16623 If @command{gnatpp} changes the casing of a defining
16624 occurrence, it analogously changes the casing of all the
16625 usage occurrences of this name.
16627 If the defining occurrence of a name is not in the source compilation unit
16628 currently being processed by @command{gnatpp}, the casing of each reference to
16629 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16630 switch (subject to the dictionary file mechanism described below).
16631 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16633 casing for the defining occurrence of the name.
16635 Some names may need to be spelled with casing conventions that are not
16636 covered by the upper-, lower-, and mixed-case transformations.
16637 You can arrange correct casing by placing such names in a
16638 @emph{dictionary file},
16639 and then supplying a @option{^-D^/DICTIONARY^} switch.
16640 The casing of names from dictionary files overrides
16641 any @option{^-n^/NAME_CASING^} switch.
16643 To handle the casing of Ada predefined names and the names from GNAT libraries,
16644 @command{gnatpp} assumes a default dictionary file.
16645 The name of each predefined entity is spelled with the same casing as is used
16646 for the entity in the @cite{Ada Reference Manual}.
16647 The name of each entity in the GNAT libraries is spelled with the same casing
16648 as is used in the declaration of that entity.
16650 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
16651 default dictionary file.
16652 Instead, the casing for predefined and GNAT-defined names will be established
16653 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
16654 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
16655 will appear as just shown,
16656 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
16657 To ensure that even such names are rendered in uppercase,
16658 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
16659 (or else, less conveniently, place these names in upper case in a dictionary
16662 A dictionary file is
16663 a plain text file; each line in this file can be either a blank line
16664 (containing only space characters and ASCII.HT characters), an Ada comment
16665 line, or the specification of exactly one @emph{casing schema}.
16667 A casing schema is a string that has the following syntax:
16671 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
16673 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
16678 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
16679 @var{identifier} lexical element and the @var{letter_or_digit} category.)
16681 The casing schema string can be followed by white space and/or an Ada-style
16682 comment; any amount of white space is allowed before the string.
16684 If a dictionary file is passed as
16686 the value of a @option{-D@var{file}} switch
16689 an option to the @option{/DICTIONARY} qualifier
16692 simple name and every identifier, @command{gnatpp} checks if the dictionary
16693 defines the casing for the name or for some of its parts (the term ``subword''
16694 is used below to denote the part of a name which is delimited by ``_'' or by
16695 the beginning or end of the word and which does not contain any ``_'' inside):
16699 if the whole name is in the dictionary, @command{gnatpp} uses for this name
16700 the casing defined by the dictionary; no subwords are checked for this word
16703 for every subword @command{gnatpp} checks if the dictionary contains the
16704 corresponding string of the form @code{*@var{simple_identifier}*},
16705 and if it does, the casing of this @var{simple_identifier} is used
16709 if the whole name does not contain any ``_'' inside, and if for this name
16710 the dictionary contains two entries - one of the form @var{identifier},
16711 and another - of the form *@var{simple_identifier}*, then the first one
16712 is applied to define the casing of this name
16715 if more than one dictionary file is passed as @command{gnatpp} switches, each
16716 dictionary adds new casing exceptions and overrides all the existing casing
16717 exceptions set by the previous dictionaries
16720 when @command{gnatpp} checks if the word or subword is in the dictionary,
16721 this check is not case sensitive
16725 For example, suppose we have the following source to reformat:
16727 @smallexample @c ada
16730 name1 : integer := 1;
16731 name4_name3_name2 : integer := 2;
16732 name2_name3_name4 : Boolean;
16735 name2_name3_name4 := name4_name3_name2 > name1;
16741 And suppose we have two dictionaries:
16758 If @command{gnatpp} is called with the following switches:
16762 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
16765 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
16770 then we will get the following name casing in the @command{gnatpp} output:
16772 @smallexample @c ada
16775 NAME1 : Integer := 1;
16776 Name4_NAME3_Name2 : Integer := 2;
16777 Name2_NAME3_Name4 : Boolean;
16780 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
16785 @c *********************************
16786 @node The GNAT Metric Tool gnatmetric
16787 @chapter The GNAT Metric Tool @command{gnatmetric}
16789 @cindex Metric tool
16792 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
16793 for computing various program metrics.
16794 It takes an Ada source file as input and generates a file containing the
16795 metrics data as output. Various switches control which
16796 metrics are computed and output.
16798 @command{gnatmetric} generates and uses the ASIS
16799 tree for the input source and thus requires the input to be syntactically and
16800 semantically legal.
16801 If this condition is not met, @command{gnatmetric} will generate
16802 an error message; no metric information for this file will be
16803 computed and reported.
16805 If the compilation unit contained in the input source depends semantically
16806 upon units in files located outside the current directory, you have to provide
16807 the source search path when invoking @command{gnatmetric}.
16808 If it depends semantically upon units that are contained
16809 in files with names that do not follow the GNAT file naming rules, you have to
16810 provide the configuration file describing the corresponding naming scheme (see
16811 the description of the @command{gnatmetric} switches below.)
16812 Alternatively, you may use a project file and invoke @command{gnatmetric}
16813 through the @command{gnat} driver.
16815 The @command{gnatmetric} command has the form
16818 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
16825 @var{switches} specify the metrics to compute and define the destination for
16829 Each @var{filename} is the name (including the extension) of a source
16830 file to process. ``Wildcards'' are allowed, and
16831 the file name may contain path information.
16832 If no @var{filename} is supplied, then the @var{switches} list must contain
16834 @option{-files} switch (@pxref{Other gnatmetric Switches}).
16835 Including both a @option{-files} switch and one or more
16836 @var{filename} arguments is permitted.
16839 @samp{-cargs @var{gcc_switches}} is a list of switches for
16840 @command{gcc}. They will be passed on to all compiler invocations made by
16841 @command{gnatmetric} to generate the ASIS trees. Here you can provide
16842 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
16843 and use the @option{-gnatec} switch to set the configuration file.
16847 * Switches for gnatmetric::
16850 @node Switches for gnatmetric
16851 @section Switches for @command{gnatmetric}
16854 The following subsections describe the various switches accepted by
16855 @command{gnatmetric}, organized by category.
16858 * Output Files Control::
16859 * Disable Metrics For Local Units::
16860 * Specifying a set of metrics to compute::
16861 * Other gnatmetric Switches::
16862 * Generate project-wide metrics::
16865 @node Output Files Control
16866 @subsection Output File Control
16867 @cindex Output file control in @command{gnatmetric}
16870 @command{gnatmetric} has two output formats. It can generate a
16871 textual (human-readable) form, and also XML. By default only textual
16872 output is generated.
16874 When generating the output in textual form, @command{gnatmetric} creates
16875 for each Ada source file a corresponding text file
16876 containing the computed metrics, except for the case when the set of metrics
16877 specified by gnatmetric parameters consists only of metrics that are computed
16878 for the whole set of analyzed sources, but not for each Ada source.
16879 By default, this file is placed in the same directory as where the source
16880 file is located, and its name is obtained
16881 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
16884 All the output information generated in XML format is placed in a single
16885 file. By default this file is placed in the current directory and has the
16886 name ^@file{metrix.xml}^@file{METRIX$XML}^.
16888 Some of the computed metrics are summed over the units passed to
16889 @command{gnatmetric}; for example, the total number of lines of code.
16890 By default this information is sent to @file{stdout}, but a file
16891 can be specified with the @option{-og} switch.
16893 The following switches control the @command{gnatmetric} output:
16896 @cindex @option{^-x^/XML^} (@command{gnatmetric})
16898 Generate the XML output
16900 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
16901 @item ^-nt^/NO_TEXT^
16902 Do not generate the output in text form (implies @option{^-x^/XML^})
16904 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
16905 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
16906 Put textual files with detailed metrics into @var{output_dir}
16908 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
16909 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
16910 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
16911 in the name of the output file.
16913 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
16914 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
16915 Put global metrics into @var{file_name}
16917 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
16918 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
16919 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
16921 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
16922 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
16923 Use ``short'' source file names in the output. (The @command{gnatmetric}
16924 output includes the name(s) of the Ada source file(s) from which the metrics
16925 are computed. By default each name includes the absolute path. The
16926 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
16927 to exclude all directory information from the file names that are output.)
16931 @node Disable Metrics For Local Units
16932 @subsection Disable Metrics For Local Units
16933 @cindex Disable Metrics For Local Units in @command{gnatmetric}
16936 @command{gnatmetric} relies on the GNAT compilation model @minus{}
16938 unit per one source file. It computes line metrics for the whole source
16939 file, and it also computes syntax
16940 and complexity metrics for the file's outermost unit.
16942 By default, @command{gnatmetric} will also compute all metrics for certain
16943 kinds of locally declared program units:
16947 subprogram (and generic subprogram) bodies;
16950 package (and generic package) specs and bodies;
16953 task object and type specifications and bodies;
16956 protected object and type specifications and bodies.
16960 These kinds of entities will be referred to as
16961 @emph{eligible local program units}, or simply @emph{eligible local units},
16962 @cindex Eligible local unit (for @command{gnatmetric})
16963 in the discussion below.
16965 Note that a subprogram declaration, generic instantiation,
16966 or renaming declaration only receives metrics
16967 computation when it appear as the outermost entity
16970 Suppression of metrics computation for eligible local units can be
16971 obtained via the following switch:
16974 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
16975 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
16976 Do not compute detailed metrics for eligible local program units
16980 @node Specifying a set of metrics to compute
16981 @subsection Specifying a set of metrics to compute
16984 By default all the metrics are computed and reported. The switches
16985 described in this subsection allow you to control, on an individual
16986 basis, whether metrics are computed and
16987 reported. If at least one positive metric
16988 switch is specified (that is, a switch that defines that a given
16989 metric or set of metrics is to be computed), then only
16990 explicitly specified metrics are reported.
16993 * Line Metrics Control::
16994 * Syntax Metrics Control::
16995 * Complexity Metrics Control::
16996 * Object-Oriented Metrics Control::
16999 @node Line Metrics Control
17000 @subsubsection Line Metrics Control
17001 @cindex Line metrics control in @command{gnatmetric}
17004 For any (legal) source file, and for each of its
17005 eligible local program units, @command{gnatmetric} computes the following
17010 the total number of lines;
17013 the total number of code lines (i.e., non-blank lines that are not comments)
17016 the number of comment lines
17019 the number of code lines containing end-of-line comments;
17022 the comment percentage: the ratio between the number of lines that contain
17023 comments and the number of all non-blank lines, expressed as a percentage;
17026 the number of empty lines and lines containing only space characters and/or
17027 format effectors (blank lines)
17030 the average number of code lines in subprogram bodies, task bodies, entry
17031 bodies and statement sequences in package bodies (this metric is only computed
17032 across the whole set of the analyzed units)
17037 @command{gnatmetric} sums the values of the line metrics for all the
17038 files being processed and then generates the cumulative results. The tool
17039 also computes for all the files being processed the average number of code
17042 You can use the following switches to select the specific line metrics
17043 to be computed and reported.
17046 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17049 @cindex @option{--no-lines@var{x}}
17052 @item ^--lines-all^/LINE_COUNT_METRICS=ALL_ON^
17053 Report all the line metrics
17055 @item ^--no-lines-all^/LINE_COUNT_METRICS=ALL_OFF^
17056 Do not report any of line metrics
17058 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES_ON^
17059 Report the number of all lines
17061 @item ^--no-lines^/LINE_COUNT_METRICS=ALL_LINES_OFF^
17062 Do not report the number of all lines
17064 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES_ON^
17065 Report the number of code lines
17067 @item ^--no-lines-code^/LINE_COUNT_METRICS=CODE_LINES_OFF^
17068 Do not report the number of code lines
17070 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_ON^
17071 Report the number of comment lines
17073 @item ^--no-lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_OFF^
17074 Do not report the number of comment lines
17076 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_ON^
17077 Report the number of code lines containing
17078 end-of-line comments
17080 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_OFF^
17081 Do not report the number of code lines containing
17082 end-of-line comments
17084 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_ON^
17085 Report the comment percentage in the program text
17087 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_OFF^
17088 Do not report the comment percentage in the program text
17090 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_ON^
17091 Report the number of blank lines
17093 @item ^--no-lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_OFF^
17094 Do not report the number of blank lines
17096 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_ON^
17097 Report the average number of code lines in subprogram bodies, task bodies,
17098 entry bodies and statement sequences in package bodies. The metric is computed
17099 and reported for the whole set of processed Ada sources only.
17101 @item ^--no-lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_OFF^
17102 Do not report the average number of code lines in subprogram bodies,
17103 task bodies, entry bodies and statement sequences in package bodies.
17107 @node Syntax Metrics Control
17108 @subsubsection Syntax Metrics Control
17109 @cindex Syntax metrics control in @command{gnatmetric}
17112 @command{gnatmetric} computes various syntactic metrics for the
17113 outermost unit and for each eligible local unit:
17116 @item LSLOC (``Logical Source Lines Of Code'')
17117 The total number of declarations and the total number of statements
17119 @item Maximal static nesting level of inner program units
17121 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17122 package, a task unit, a protected unit, a
17123 protected entry, a generic unit, or an explicitly declared subprogram other
17124 than an enumeration literal.''
17126 @item Maximal nesting level of composite syntactic constructs
17127 This corresponds to the notion of the
17128 maximum nesting level in the GNAT built-in style checks
17129 (@pxref{Style Checking})
17133 For the outermost unit in the file, @command{gnatmetric} additionally computes
17134 the following metrics:
17137 @item Public subprograms
17138 This metric is computed for package specs. It is the
17139 number of subprograms and generic subprograms declared in the visible
17140 part (including the visible part of nested packages, protected objects, and
17143 @item All subprograms
17144 This metric is computed for bodies and subunits. The
17145 metric is equal to a total number of subprogram bodies in the compilation
17147 Neither generic instantiations nor renamings-as-a-body nor body stubs
17148 are counted. Any subprogram body is counted, independently of its nesting
17149 level and enclosing constructs. Generic bodies and bodies of protected
17150 subprograms are counted in the same way as ``usual'' subprogram bodies.
17153 This metric is computed for package specs and
17154 generic package declarations. It is the total number of types
17155 that can be referenced from outside this compilation unit, plus the
17156 number of types from all the visible parts of all the visible generic
17157 packages. Generic formal types are not counted. Only types, not subtypes,
17161 Along with the total number of public types, the following
17162 types are counted and reported separately:
17169 Root tagged types (abstract, non-abstract, private, non-private). Type
17170 extensions are @emph{not} counted
17173 Private types (including private extensions)
17184 This metric is computed for any compilation unit. It is equal to the total
17185 number of the declarations of different types given in the compilation unit.
17186 The private and the corresponding full type declaration are counted as one
17187 type declaration. Incomplete type declarations and generic formal types
17189 No distinction is made among different kinds of types (abstract,
17190 private etc.); the total number of types is computed and reported.
17195 By default, all the syntax metrics are computed and reported. You can use the
17196 following switches to select specific syntax metrics.
17200 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17203 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17206 @item ^--syntax-all^/SYNTAX_METRICS=ALL_ON^
17207 Report all the syntax metrics
17209 @item ^--no-syntax-all^/ALL_OFF^
17210 Do not report any of syntax metrics
17212 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS_ON^
17213 Report the total number of declarations
17215 @item ^--no-declarations^/SYNTAX_METRICS=DECLARATIONS_OFF^
17216 Do not report the total number of declarations
17218 @item ^--statements^/SYNTAX_METRICS=STATEMENTS_ON^
17219 Report the total number of statements
17221 @item ^--no-statements^/SYNTAX_METRICS=STATEMENTS_OFF^
17222 Do not report the total number of statements
17224 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_ON^
17225 Report the number of public subprograms in a compilation unit
17227 @item ^--no-public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_OFF^
17228 Do not report the number of public subprograms in a compilation unit
17230 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_ON^
17231 Report the number of all the subprograms in a compilation unit
17233 @item ^--no-all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_OFF^
17234 Do not report the number of all the subprograms in a compilation unit
17236 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES_ON^
17237 Report the number of public types in a compilation unit
17239 @item ^--no-public-types^/SYNTAX_METRICS=PUBLIC_TYPES_OFF^
17240 Do not report the number of public types in a compilation unit
17242 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES_ON^
17243 Report the number of all the types in a compilation unit
17245 @item ^--no-all-types^/SYNTAX_METRICS=ALL_TYPES_OFF^
17246 Do not report the number of all the types in a compilation unit
17248 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_ON^
17249 Report the maximal program unit nesting level
17251 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17252 Do not report the maximal program unit nesting level
17254 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_ON^
17255 Report the maximal construct nesting level
17257 @item ^--no-construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_OFF^
17258 Do not report the maximal construct nesting level
17262 @node Complexity Metrics Control
17263 @subsubsection Complexity Metrics Control
17264 @cindex Complexity metrics control in @command{gnatmetric}
17267 For a program unit that is an executable body (a subprogram body (including
17268 generic bodies), task body, entry body or a package body containing
17269 its own statement sequence) @command{gnatmetric} computes the following
17270 complexity metrics:
17274 McCabe cyclomatic complexity;
17277 McCabe essential complexity;
17280 maximal loop nesting level
17285 The McCabe complexity metrics are defined
17286 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17288 According to McCabe, both control statements and short-circuit control forms
17289 should be taken into account when computing cyclomatic complexity. For each
17290 body, we compute three metric values:
17294 the complexity introduced by control
17295 statements only, without taking into account short-circuit forms,
17298 the complexity introduced by short-circuit control forms only, and
17302 cyclomatic complexity, which is the sum of these two values.
17306 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17307 the code in the exception handlers and in all the nested program units.
17309 By default, all the complexity metrics are computed and reported.
17310 For more fine-grained control you can use
17311 the following switches:
17314 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17317 @cindex @option{--no-complexity@var{x}}
17320 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL_ON^
17321 Report all the complexity metrics
17323 @item ^--no-complexity-all^/COMPLEXITY_METRICS=ALL_OFF^
17324 Do not report any of complexity metrics
17326 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_ON^
17327 Report the McCabe Cyclomatic Complexity
17329 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_OFF^
17330 Do not report the McCabe Cyclomatic Complexity
17332 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_ON^
17333 Report the Essential Complexity
17335 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_OFF^
17336 Do not report the Essential Complexity
17338 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17339 Report maximal loop nesting level
17341 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_OFF^
17342 Do not report maximal loop nesting level
17344 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_ON^
17345 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17346 task bodies, entry bodies and statement sequences in package bodies.
17347 The metric is computed and reported for whole set of processed Ada sources
17350 @item ^--no-complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_OFF^
17351 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17352 bodies, task bodies, entry bodies and statement sequences in package bodies
17354 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17355 @item ^-ne^/NO_EXITS_AS_GOTOS^
17356 Do not consider @code{exit} statements as @code{goto}s when
17357 computing Essential Complexity
17362 @node Object-Oriented Metrics Control
17363 @subsubsection Object-Oriented Metrics Control
17364 @cindex Object-Oriented metrics control in @command{gnatmetric}
17367 @cindex Coupling metrics (in in @command{gnatmetric})
17368 Coupling metrics are object-oriented metrics that measure the
17369 dependencies between a given class (or a group of classes) and the
17370 ``external world'' (that is, the other classes in the program). In this
17371 subsection the term ``class'' is used in its
17372 traditional object-oriented programming sense
17373 (an instantiable module that contains data and/or method members).
17374 A @emph{category} (of classes)
17375 is a group of closely related classes that are reused and/or
17378 A class @code{K}'s @emph{efferent coupling} is the number of classes
17379 that @code{K} depends upon.
17380 A category's efferent coupling is the number of classes outside the
17381 category that the classes inside the category depend upon.
17383 A class @code{K}'s @emph{afferent coupling} is the number of classes
17384 that depend upon @code{K}.
17385 A category's afferent coupling is the number of classes outside the
17386 category that depend on classes belonging to the category.
17388 Ada's implementation of the object-oriented paradigm does not use the
17389 traditional class notion, so the definition of the coupling
17390 metrics for Ada maps the class and class category notions
17391 onto Ada constructs.
17393 For the coupling metrics, several kinds of modules -- a library package,
17394 a library generic package, and a library generic package instantiation --
17395 that define a tagged type or an interface type are
17396 considered to be a class. A category consists of a library package (or
17397 a library generic package) that defines a tagged or an interface type,
17398 together with all its descendant (generic) packages that define tagged
17399 or interface types. For any package counted as a class,
17400 its body (if any) is considered
17401 together with its spec when counting the dependencies. For dependencies
17402 between classes, the Ada semantic dependencies are considered.
17403 For coupling metrics, only dependencies on units that are considered as
17404 classes, are considered.
17406 When computing coupling metrics, @command{gnatmetric} counts only
17407 dependencies between units that are arguments of the gnatmetric call.
17408 Coupling metrics are program-wide (or project-wide) metrics, so to
17409 get a valid result, you should call @command{gnatmetric} for
17410 the whole set of sources that make up your program. It can be done
17411 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17412 option (see See @ref{The GNAT Driver and Project Files} for details.
17414 By default, all the coupling metrics are disabled. You can use the following
17415 switches to specify the coupling metrics to be computed and reported:
17420 @cindex @option{--package@var{x}} (@command{gnatmetric})
17421 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17422 @cindex @option{--category@var{x}} (@command{gnatmetric})
17423 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17427 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17430 @item ^--coupling-all^/COUPLING_METRICS=ALL_ON^
17431 Report all the coupling metrics
17433 @item ^--no-coupling-all^/COUPLING_METRICS=ALL_OFF^
17434 Do not report any of metrics
17436 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_ON^
17437 Report package efferent coupling
17439 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_OFF^
17440 Do not report package efferent coupling
17442 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_ON^
17443 Report package afferent coupling
17445 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_OFF^
17446 Do not report package afferent coupling
17448 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_ON^
17449 Report category efferent coupling
17451 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_OFF^
17452 Do not report category efferent coupling
17454 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_ON^
17455 Report category afferent coupling
17457 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_OFF^
17458 Do not report category afferent coupling
17462 @node Other gnatmetric Switches
17463 @subsection Other @code{gnatmetric} Switches
17466 Additional @command{gnatmetric} switches are as follows:
17469 @item ^-files @var{filename}^/FILES=@var{filename}^
17470 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17471 Take the argument source files from the specified file. This file should be an
17472 ordinary text file containing file names separated by spaces or
17473 line breaks. You can use this switch more then once in the same call to
17474 @command{gnatmetric}. You also can combine this switch with
17475 an explicit list of files.
17477 @item ^-v^/VERBOSE^
17478 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17480 @command{gnatmetric} generates version information and then
17481 a trace of sources being processed.
17483 @item ^-dv^/DEBUG_OUTPUT^
17484 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17486 @command{gnatmetric} generates various messages useful to understand what
17487 happens during the metrics computation
17490 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17494 @node Generate project-wide metrics
17495 @subsection Generate project-wide metrics
17497 In order to compute metrics on all units of a given project, you can use
17498 the @command{gnat} driver along with the @option{-P} option:
17504 If the project @code{proj} depends upon other projects, you can compute
17505 the metrics on the project closure using the @option{-U} option:
17507 gnat metric -Pproj -U
17511 Finally, if not all the units are relevant to a particular main
17512 program in the project closure, you can generate metrics for the set
17513 of units needed to create a given main program (unit closure) using
17514 the @option{-U} option followed by the name of the main unit:
17516 gnat metric -Pproj -U main
17520 @c ***********************************
17521 @node File Name Krunching Using gnatkr
17522 @chapter File Name Krunching Using @code{gnatkr}
17526 This chapter discusses the method used by the compiler to shorten
17527 the default file names chosen for Ada units so that they do not
17528 exceed the maximum length permitted. It also describes the
17529 @code{gnatkr} utility that can be used to determine the result of
17530 applying this shortening.
17534 * Krunching Method::
17535 * Examples of gnatkr Usage::
17539 @section About @code{gnatkr}
17542 The default file naming rule in GNAT
17543 is that the file name must be derived from
17544 the unit name. The exact default rule is as follows:
17547 Take the unit name and replace all dots by hyphens.
17549 If such a replacement occurs in the
17550 second character position of a name, and the first character is
17551 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17552 then replace the dot by the character
17553 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17554 instead of a minus.
17556 The reason for this exception is to avoid clashes
17557 with the standard names for children of System, Ada, Interfaces,
17558 and GNAT, which use the prefixes
17559 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17562 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17563 switch of the compiler activates a ``krunching''
17564 circuit that limits file names to nn characters (where nn is a decimal
17565 integer). For example, using OpenVMS,
17566 where the maximum file name length is
17567 39, the value of nn is usually set to 39, but if you want to generate
17568 a set of files that would be usable if ported to a system with some
17569 different maximum file length, then a different value can be specified.
17570 The default value of 39 for OpenVMS need not be specified.
17572 The @code{gnatkr} utility can be used to determine the krunched name for
17573 a given file, when krunched to a specified maximum length.
17576 @section Using @code{gnatkr}
17579 The @code{gnatkr} command has the form
17583 $ gnatkr @var{name} @ovar{length}
17589 $ gnatkr @var{name} /COUNT=nn
17594 @var{name} is the uncrunched file name, derived from the name of the unit
17595 in the standard manner described in the previous section (i.e., in particular
17596 all dots are replaced by hyphens). The file name may or may not have an
17597 extension (defined as a suffix of the form period followed by arbitrary
17598 characters other than period). If an extension is present then it will
17599 be preserved in the output. For example, when krunching @file{hellofile.ads}
17600 to eight characters, the result will be hellofil.ads.
17602 Note: for compatibility with previous versions of @code{gnatkr} dots may
17603 appear in the name instead of hyphens, but the last dot will always be
17604 taken as the start of an extension. So if @code{gnatkr} is given an argument
17605 such as @file{Hello.World.adb} it will be treated exactly as if the first
17606 period had been a hyphen, and for example krunching to eight characters
17607 gives the result @file{hellworl.adb}.
17609 Note that the result is always all lower case (except on OpenVMS where it is
17610 all upper case). Characters of the other case are folded as required.
17612 @var{length} represents the length of the krunched name. The default
17613 when no argument is given is ^8^39^ characters. A length of zero stands for
17614 unlimited, in other words do not chop except for system files where the
17615 implied crunching length is always eight characters.
17618 The output is the krunched name. The output has an extension only if the
17619 original argument was a file name with an extension.
17621 @node Krunching Method
17622 @section Krunching Method
17625 The initial file name is determined by the name of the unit that the file
17626 contains. The name is formed by taking the full expanded name of the
17627 unit and replacing the separating dots with hyphens and
17628 using ^lowercase^uppercase^
17629 for all letters, except that a hyphen in the second character position is
17630 replaced by a ^tilde^dollar sign^ if the first character is
17631 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
17632 The extension is @code{.ads} for a
17633 spec and @code{.adb} for a body.
17634 Krunching does not affect the extension, but the file name is shortened to
17635 the specified length by following these rules:
17639 The name is divided into segments separated by hyphens, tildes or
17640 underscores and all hyphens, tildes, and underscores are
17641 eliminated. If this leaves the name short enough, we are done.
17644 If the name is too long, the longest segment is located (left-most
17645 if there are two of equal length), and shortened by dropping
17646 its last character. This is repeated until the name is short enough.
17648 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
17649 to fit the name into 8 characters as required by some operating systems.
17652 our-strings-wide_fixed 22
17653 our strings wide fixed 19
17654 our string wide fixed 18
17655 our strin wide fixed 17
17656 our stri wide fixed 16
17657 our stri wide fixe 15
17658 our str wide fixe 14
17659 our str wid fixe 13
17665 Final file name: oustwifi.adb
17669 The file names for all predefined units are always krunched to eight
17670 characters. The krunching of these predefined units uses the following
17671 special prefix replacements:
17675 replaced by @file{^a^A^-}
17678 replaced by @file{^g^G^-}
17681 replaced by @file{^i^I^-}
17684 replaced by @file{^s^S^-}
17687 These system files have a hyphen in the second character position. That
17688 is why normal user files replace such a character with a
17689 ^tilde^dollar sign^, to
17690 avoid confusion with system file names.
17692 As an example of this special rule, consider
17693 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
17696 ada-strings-wide_fixed 22
17697 a- strings wide fixed 18
17698 a- string wide fixed 17
17699 a- strin wide fixed 16
17700 a- stri wide fixed 15
17701 a- stri wide fixe 14
17702 a- str wide fixe 13
17708 Final file name: a-stwifi.adb
17712 Of course no file shortening algorithm can guarantee uniqueness over all
17713 possible unit names, and if file name krunching is used then it is your
17714 responsibility to ensure that no name clashes occur. The utility
17715 program @code{gnatkr} is supplied for conveniently determining the
17716 krunched name of a file.
17718 @node Examples of gnatkr Usage
17719 @section Examples of @code{gnatkr} Usage
17726 $ gnatkr very_long_unit_name.ads --> velounna.ads
17727 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
17728 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
17729 $ gnatkr grandparent-parent-child --> grparchi
17731 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
17732 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
17735 @node Preprocessing Using gnatprep
17736 @chapter Preprocessing Using @code{gnatprep}
17740 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
17742 Although designed for use with GNAT, @code{gnatprep} does not depend on any
17743 special GNAT features.
17744 For further discussion of conditional compilation in general, see
17745 @ref{Conditional Compilation}.
17748 * Preprocessing Symbols::
17750 * Switches for gnatprep::
17751 * Form of Definitions File::
17752 * Form of Input Text for gnatprep::
17755 @node Preprocessing Symbols
17756 @section Preprocessing Symbols
17759 Preprocessing symbols are defined in definition files and referred to in
17760 sources to be preprocessed. A Preprocessing symbol is an identifier, following
17761 normal Ada (case-insensitive) rules for its syntax, with the restriction that
17762 all characters need to be in the ASCII set (no accented letters).
17764 @node Using gnatprep
17765 @section Using @code{gnatprep}
17768 To call @code{gnatprep} use
17771 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
17778 is an optional sequence of switches as described in the next section.
17781 is the full name of the input file, which is an Ada source
17782 file containing preprocessor directives.
17785 is the full name of the output file, which is an Ada source
17786 in standard Ada form. When used with GNAT, this file name will
17787 normally have an ads or adb suffix.
17790 is the full name of a text file containing definitions of
17791 preprocessing symbols to be referenced by the preprocessor. This argument is
17792 optional, and can be replaced by the use of the @option{-D} switch.
17796 @node Switches for gnatprep
17797 @section Switches for @code{gnatprep}
17802 @item ^-b^/BLANK_LINES^
17803 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
17804 Causes both preprocessor lines and the lines deleted by
17805 preprocessing to be replaced by blank lines in the output source file,
17806 preserving line numbers in the output file.
17808 @item ^-c^/COMMENTS^
17809 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
17810 Causes both preprocessor lines and the lines deleted
17811 by preprocessing to be retained in the output source as comments marked
17812 with the special string @code{"--! "}. This option will result in line numbers
17813 being preserved in the output file.
17815 @item ^-C^/REPLACE_IN_COMMENTS^
17816 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
17817 Causes comments to be scanned. Normally comments are ignored by gnatprep.
17818 If this option is specified, then comments are scanned and any $symbol
17819 substitutions performed as in program text. This is particularly useful
17820 when structured comments are used (e.g., when writing programs in the
17821 SPARK dialect of Ada). Note that this switch is not available when
17822 doing integrated preprocessing (it would be useless in this context
17823 since comments are ignored by the compiler in any case).
17825 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
17826 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
17827 Defines a new preprocessing symbol, associated with value. If no value is given
17828 on the command line, then symbol is considered to be @code{True}. This switch
17829 can be used in place of a definition file.
17833 @cindex @option{/REMOVE} (@command{gnatprep})
17834 This is the default setting which causes lines deleted by preprocessing
17835 to be entirely removed from the output file.
17838 @item ^-r^/REFERENCE^
17839 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
17840 Causes a @code{Source_Reference} pragma to be generated that
17841 references the original input file, so that error messages will use
17842 the file name of this original file. The use of this switch implies
17843 that preprocessor lines are not to be removed from the file, so its
17844 use will force @option{^-b^/BLANK_LINES^} mode if
17845 @option{^-c^/COMMENTS^}
17846 has not been specified explicitly.
17848 Note that if the file to be preprocessed contains multiple units, then
17849 it will be necessary to @code{gnatchop} the output file from
17850 @code{gnatprep}. If a @code{Source_Reference} pragma is present
17851 in the preprocessed file, it will be respected by
17852 @code{gnatchop ^-r^/REFERENCE^}
17853 so that the final chopped files will correctly refer to the original
17854 input source file for @code{gnatprep}.
17856 @item ^-s^/SYMBOLS^
17857 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
17858 Causes a sorted list of symbol names and values to be
17859 listed on the standard output file.
17861 @item ^-u^/UNDEFINED^
17862 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
17863 Causes undefined symbols to be treated as having the value FALSE in the context
17864 of a preprocessor test. In the absence of this option, an undefined symbol in
17865 a @code{#if} or @code{#elsif} test will be treated as an error.
17871 Note: if neither @option{-b} nor @option{-c} is present,
17872 then preprocessor lines and
17873 deleted lines are completely removed from the output, unless -r is
17874 specified, in which case -b is assumed.
17877 @node Form of Definitions File
17878 @section Form of Definitions File
17881 The definitions file contains lines of the form
17888 where symbol is a preprocessing symbol, and value is one of the following:
17892 Empty, corresponding to a null substitution
17894 A string literal using normal Ada syntax
17896 Any sequence of characters from the set
17897 (letters, digits, period, underline).
17901 Comment lines may also appear in the definitions file, starting with
17902 the usual @code{--},
17903 and comments may be added to the definitions lines.
17905 @node Form of Input Text for gnatprep
17906 @section Form of Input Text for @code{gnatprep}
17909 The input text may contain preprocessor conditional inclusion lines,
17910 as well as general symbol substitution sequences.
17912 The preprocessor conditional inclusion commands have the form
17917 #if @i{expression} @r{[}then@r{]}
17919 #elsif @i{expression} @r{[}then@r{]}
17921 #elsif @i{expression} @r{[}then@r{]}
17932 In this example, @i{expression} is defined by the following grammar:
17934 @i{expression} ::= <symbol>
17935 @i{expression} ::= <symbol> = "<value>"
17936 @i{expression} ::= <symbol> = <symbol>
17937 @i{expression} ::= <symbol> 'Defined
17938 @i{expression} ::= not @i{expression}
17939 @i{expression} ::= @i{expression} and @i{expression}
17940 @i{expression} ::= @i{expression} or @i{expression}
17941 @i{expression} ::= @i{expression} and then @i{expression}
17942 @i{expression} ::= @i{expression} or else @i{expression}
17943 @i{expression} ::= ( @i{expression} )
17946 The following restriction exists: it is not allowed to have "and" or "or"
17947 following "not" in the same expression without parentheses. For example, this
17954 This should be one of the following:
17962 For the first test (@i{expression} ::= <symbol>) the symbol must have
17963 either the value true or false, that is to say the right-hand of the
17964 symbol definition must be one of the (case-insensitive) literals
17965 @code{True} or @code{False}. If the value is true, then the
17966 corresponding lines are included, and if the value is false, they are
17969 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
17970 the symbol has been defined in the definition file or by a @option{-D}
17971 switch on the command line. Otherwise, the test is false.
17973 The equality tests are case insensitive, as are all the preprocessor lines.
17975 If the symbol referenced is not defined in the symbol definitions file,
17976 then the effect depends on whether or not switch @option{-u}
17977 is specified. If so, then the symbol is treated as if it had the value
17978 false and the test fails. If this switch is not specified, then
17979 it is an error to reference an undefined symbol. It is also an error to
17980 reference a symbol that is defined with a value other than @code{True}
17983 The use of the @code{not} operator inverts the sense of this logical test.
17984 The @code{not} operator cannot be combined with the @code{or} or @code{and}
17985 operators, without parentheses. For example, "if not X or Y then" is not
17986 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
17988 The @code{then} keyword is optional as shown
17990 The @code{#} must be the first non-blank character on a line, but
17991 otherwise the format is free form. Spaces or tabs may appear between
17992 the @code{#} and the keyword. The keywords and the symbols are case
17993 insensitive as in normal Ada code. Comments may be used on a
17994 preprocessor line, but other than that, no other tokens may appear on a
17995 preprocessor line. Any number of @code{elsif} clauses can be present,
17996 including none at all. The @code{else} is optional, as in Ada.
17998 The @code{#} marking the start of a preprocessor line must be the first
17999 non-blank character on the line, i.e., it must be preceded only by
18000 spaces or horizontal tabs.
18002 Symbol substitution outside of preprocessor lines is obtained by using
18010 anywhere within a source line, except in a comment or within a
18011 string literal. The identifier
18012 following the @code{$} must match one of the symbols defined in the symbol
18013 definition file, and the result is to substitute the value of the
18014 symbol in place of @code{$symbol} in the output file.
18016 Note that although the substitution of strings within a string literal
18017 is not possible, it is possible to have a symbol whose defined value is
18018 a string literal. So instead of setting XYZ to @code{hello} and writing:
18021 Header : String := "$XYZ";
18025 you should set XYZ to @code{"hello"} and write:
18028 Header : String := $XYZ;
18032 and then the substitution will occur as desired.
18035 @node The GNAT Run-Time Library Builder gnatlbr
18036 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18038 @cindex Library builder
18041 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18042 supplied configuration pragmas.
18045 * Running gnatlbr::
18046 * Switches for gnatlbr::
18047 * Examples of gnatlbr Usage::
18050 @node Running gnatlbr
18051 @section Running @code{gnatlbr}
18054 The @code{gnatlbr} command has the form
18057 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18060 @node Switches for gnatlbr
18061 @section Switches for @code{gnatlbr}
18064 @code{gnatlbr} recognizes the following switches:
18068 @item /CREATE=directory
18069 @cindex @code{/CREATE} (@code{gnatlbr})
18070 Create the new run-time library in the specified directory.
18072 @item /SET=directory
18073 @cindex @code{/SET} (@code{gnatlbr})
18074 Make the library in the specified directory the current run-time library.
18076 @item /DELETE=directory
18077 @cindex @code{/DELETE} (@code{gnatlbr})
18078 Delete the run-time library in the specified directory.
18081 @cindex @code{/CONFIG} (@code{gnatlbr})
18082 With /CREATE: Use the configuration pragmas in the specified file when
18083 building the library.
18085 With /SET: Use the configuration pragmas in the specified file when
18090 @node Examples of gnatlbr Usage
18091 @section Example of @code{gnatlbr} Usage
18094 Contents of VAXFLOAT.ADC:
18095 pragma Float_Representation (VAX_Float);
18097 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18099 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18104 @node The GNAT Library Browser gnatls
18105 @chapter The GNAT Library Browser @code{gnatls}
18107 @cindex Library browser
18110 @code{gnatls} is a tool that outputs information about compiled
18111 units. It gives the relationship between objects, unit names and source
18112 files. It can also be used to check the source dependencies of a unit
18113 as well as various characteristics.
18115 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18116 driver (see @ref{The GNAT Driver and Project Files}).
18120 * Switches for gnatls::
18121 * Examples of gnatls Usage::
18124 @node Running gnatls
18125 @section Running @code{gnatls}
18128 The @code{gnatls} command has the form
18131 $ gnatls switches @var{object_or_ali_file}
18135 The main argument is the list of object or @file{ali} files
18136 (@pxref{The Ada Library Information Files})
18137 for which information is requested.
18139 In normal mode, without additional option, @code{gnatls} produces a
18140 four-column listing. Each line represents information for a specific
18141 object. The first column gives the full path of the object, the second
18142 column gives the name of the principal unit in this object, the third
18143 column gives the status of the source and the fourth column gives the
18144 full path of the source representing this unit.
18145 Here is a simple example of use:
18149 ^./^[]^demo1.o demo1 DIF demo1.adb
18150 ^./^[]^demo2.o demo2 OK demo2.adb
18151 ^./^[]^hello.o h1 OK hello.adb
18152 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18153 ^./^[]^instr.o instr OK instr.adb
18154 ^./^[]^tef.o tef DIF tef.adb
18155 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18156 ^./^[]^tgef.o tgef DIF tgef.adb
18160 The first line can be interpreted as follows: the main unit which is
18162 object file @file{demo1.o} is demo1, whose main source is in
18163 @file{demo1.adb}. Furthermore, the version of the source used for the
18164 compilation of demo1 has been modified (DIF). Each source file has a status
18165 qualifier which can be:
18168 @item OK (unchanged)
18169 The version of the source file used for the compilation of the
18170 specified unit corresponds exactly to the actual source file.
18172 @item MOK (slightly modified)
18173 The version of the source file used for the compilation of the
18174 specified unit differs from the actual source file but not enough to
18175 require recompilation. If you use gnatmake with the qualifier
18176 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18177 MOK will not be recompiled.
18179 @item DIF (modified)
18180 No version of the source found on the path corresponds to the source
18181 used to build this object.
18183 @item ??? (file not found)
18184 No source file was found for this unit.
18186 @item HID (hidden, unchanged version not first on PATH)
18187 The version of the source that corresponds exactly to the source used
18188 for compilation has been found on the path but it is hidden by another
18189 version of the same source that has been modified.
18193 @node Switches for gnatls
18194 @section Switches for @code{gnatls}
18197 @code{gnatls} recognizes the following switches:
18201 @cindex @option{--version} @command{gnatls}
18202 Display Copyright and version, then exit disregarding all other options.
18205 @cindex @option{--help} @command{gnatls}
18206 If @option{--version} was not used, display usage, then exit disregarding
18209 @item ^-a^/ALL_UNITS^
18210 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18211 Consider all units, including those of the predefined Ada library.
18212 Especially useful with @option{^-d^/DEPENDENCIES^}.
18214 @item ^-d^/DEPENDENCIES^
18215 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18216 List sources from which specified units depend on.
18218 @item ^-h^/OUTPUT=OPTIONS^
18219 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18220 Output the list of options.
18222 @item ^-o^/OUTPUT=OBJECTS^
18223 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18224 Only output information about object files.
18226 @item ^-s^/OUTPUT=SOURCES^
18227 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18228 Only output information about source files.
18230 @item ^-u^/OUTPUT=UNITS^
18231 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18232 Only output information about compilation units.
18234 @item ^-files^/FILES^=@var{file}
18235 @cindex @option{^-files^/FILES^} (@code{gnatls})
18236 Take as arguments the files listed in text file @var{file}.
18237 Text file @var{file} may contain empty lines that are ignored.
18238 Each nonempty line should contain the name of an existing file.
18239 Several such switches may be specified simultaneously.
18241 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18242 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18243 @itemx ^-I^/SEARCH=^@var{dir}
18244 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18246 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18247 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18248 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18249 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18250 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18251 flags (@pxref{Switches for gnatmake}).
18253 @item --RTS=@var{rts-path}
18254 @cindex @option{--RTS} (@code{gnatls})
18255 Specifies the default location of the runtime library. Same meaning as the
18256 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18258 @item ^-v^/OUTPUT=VERBOSE^
18259 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18260 Verbose mode. Output the complete source, object and project paths. Do not use
18261 the default column layout but instead use long format giving as much as
18262 information possible on each requested units, including special
18263 characteristics such as:
18266 @item Preelaborable
18267 The unit is preelaborable in the Ada sense.
18270 No elaboration code has been produced by the compiler for this unit.
18273 The unit is pure in the Ada sense.
18275 @item Elaborate_Body
18276 The unit contains a pragma Elaborate_Body.
18279 The unit contains a pragma Remote_Types.
18281 @item Shared_Passive
18282 The unit contains a pragma Shared_Passive.
18285 This unit is part of the predefined environment and cannot be modified
18288 @item Remote_Call_Interface
18289 The unit contains a pragma Remote_Call_Interface.
18295 @node Examples of gnatls Usage
18296 @section Example of @code{gnatls} Usage
18300 Example of using the verbose switch. Note how the source and
18301 object paths are affected by the -I switch.
18304 $ gnatls -v -I.. demo1.o
18306 GNATLS 5.03w (20041123-34)
18307 Copyright 1997-2004 Free Software Foundation, Inc.
18309 Source Search Path:
18310 <Current_Directory>
18312 /home/comar/local/adainclude/
18314 Object Search Path:
18315 <Current_Directory>
18317 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18319 Project Search Path:
18320 <Current_Directory>
18321 /home/comar/local/lib/gnat/
18326 Kind => subprogram body
18327 Flags => No_Elab_Code
18328 Source => demo1.adb modified
18332 The following is an example of use of the dependency list.
18333 Note the use of the -s switch
18334 which gives a straight list of source files. This can be useful for
18335 building specialized scripts.
18338 $ gnatls -d demo2.o
18339 ./demo2.o demo2 OK demo2.adb
18345 $ gnatls -d -s -a demo1.o
18347 /home/comar/local/adainclude/ada.ads
18348 /home/comar/local/adainclude/a-finali.ads
18349 /home/comar/local/adainclude/a-filico.ads
18350 /home/comar/local/adainclude/a-stream.ads
18351 /home/comar/local/adainclude/a-tags.ads
18354 /home/comar/local/adainclude/gnat.ads
18355 /home/comar/local/adainclude/g-io.ads
18357 /home/comar/local/adainclude/system.ads
18358 /home/comar/local/adainclude/s-exctab.ads
18359 /home/comar/local/adainclude/s-finimp.ads
18360 /home/comar/local/adainclude/s-finroo.ads
18361 /home/comar/local/adainclude/s-secsta.ads
18362 /home/comar/local/adainclude/s-stalib.ads
18363 /home/comar/local/adainclude/s-stoele.ads
18364 /home/comar/local/adainclude/s-stratt.ads
18365 /home/comar/local/adainclude/s-tasoli.ads
18366 /home/comar/local/adainclude/s-unstyp.ads
18367 /home/comar/local/adainclude/unchconv.ads
18373 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18375 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18376 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
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18400 @node Cleaning Up Using gnatclean
18401 @chapter Cleaning Up Using @code{gnatclean}
18403 @cindex Cleaning tool
18406 @code{gnatclean} is a tool that allows the deletion of files produced by the
18407 compiler, binder and linker, including ALI files, object files, tree files,
18408 expanded source files, library files, interface copy source files, binder
18409 generated files and executable files.
18412 * Running gnatclean::
18413 * Switches for gnatclean::
18414 @c * Examples of gnatclean Usage::
18417 @node Running gnatclean
18418 @section Running @code{gnatclean}
18421 The @code{gnatclean} command has the form:
18424 $ gnatclean switches @var{names}
18428 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18429 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18430 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18433 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18434 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18435 the linker. In informative-only mode, specified by switch
18436 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18437 normal mode is listed, but no file is actually deleted.
18439 @node Switches for gnatclean
18440 @section Switches for @code{gnatclean}
18443 @code{gnatclean} recognizes the following switches:
18447 @cindex @option{--version} @command{gnatclean}
18448 Display Copyright and version, then exit disregarding all other options.
18451 @cindex @option{--help} @command{gnatclean}
18452 If @option{--version} was not used, display usage, then exit disregarding
18455 @item ^-c^/COMPILER_FILES_ONLY^
18456 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18457 Only attempt to delete the files produced by the compiler, not those produced
18458 by the binder or the linker. The files that are not to be deleted are library
18459 files, interface copy files, binder generated files and executable files.
18461 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18462 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18463 Indicate that ALI and object files should normally be found in directory
18466 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18467 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18468 When using project files, if some errors or warnings are detected during
18469 parsing and verbose mode is not in effect (no use of switch
18470 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18471 file, rather than its simple file name.
18474 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18475 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18477 @item ^-n^/NODELETE^
18478 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18479 Informative-only mode. Do not delete any files. Output the list of the files
18480 that would have been deleted if this switch was not specified.
18482 @item ^-P^/PROJECT_FILE=^@var{project}
18483 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18484 Use project file @var{project}. Only one such switch can be used.
18485 When cleaning a project file, the files produced by the compilation of the
18486 immediate sources or inherited sources of the project files are to be
18487 deleted. This is not depending on the presence or not of executable names
18488 on the command line.
18491 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18492 Quiet output. If there are no errors, do not output anything, except in
18493 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18494 (switch ^-n^/NODELETE^).
18496 @item ^-r^/RECURSIVE^
18497 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18498 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18499 clean all imported and extended project files, recursively. If this switch
18500 is not specified, only the files related to the main project file are to be
18501 deleted. This switch has no effect if no project file is specified.
18503 @item ^-v^/VERBOSE^
18504 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18507 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18508 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18509 Indicates the verbosity of the parsing of GNAT project files.
18510 @xref{Switches Related to Project Files}.
18512 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18513 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18514 Indicates that external variable @var{name} has the value @var{value}.
18515 The Project Manager will use this value for occurrences of
18516 @code{external(name)} when parsing the project file.
18517 @xref{Switches Related to Project Files}.
18519 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18520 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18521 When searching for ALI and object files, look in directory
18524 @item ^-I^/SEARCH=^@var{dir}
18525 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18526 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18528 @item ^-I-^/NOCURRENT_DIRECTORY^
18529 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18530 @cindex Source files, suppressing search
18531 Do not look for ALI or object files in the directory
18532 where @code{gnatclean} was invoked.
18536 @c @node Examples of gnatclean Usage
18537 @c @section Examples of @code{gnatclean} Usage
18540 @node GNAT and Libraries
18541 @chapter GNAT and Libraries
18542 @cindex Library, building, installing, using
18545 This chapter describes how to build and use libraries with GNAT, and also shows
18546 how to recompile the GNAT run-time library. You should be familiar with the
18547 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18551 * Introduction to Libraries in GNAT::
18552 * General Ada Libraries::
18553 * Stand-alone Ada Libraries::
18554 * Rebuilding the GNAT Run-Time Library::
18557 @node Introduction to Libraries in GNAT
18558 @section Introduction to Libraries in GNAT
18561 A library is, conceptually, a collection of objects which does not have its
18562 own main thread of execution, but rather provides certain services to the
18563 applications that use it. A library can be either statically linked with the
18564 application, in which case its code is directly included in the application,
18565 or, on platforms that support it, be dynamically linked, in which case
18566 its code is shared by all applications making use of this library.
18568 GNAT supports both types of libraries.
18569 In the static case, the compiled code can be provided in different ways. The
18570 simplest approach is to provide directly the set of objects resulting from
18571 compilation of the library source files. Alternatively, you can group the
18572 objects into an archive using whatever commands are provided by the operating
18573 system. For the latter case, the objects are grouped into a shared library.
18575 In the GNAT environment, a library has three types of components:
18581 @xref{The Ada Library Information Files}.
18583 Object files, an archive or a shared library.
18587 A GNAT library may expose all its source files, which is useful for
18588 documentation purposes. Alternatively, it may expose only the units needed by
18589 an external user to make use of the library. That is to say, the specs
18590 reflecting the library services along with all the units needed to compile
18591 those specs, which can include generic bodies or any body implementing an
18592 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18593 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18595 All compilation units comprising an application, including those in a library,
18596 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18597 computes the elaboration order from the @file{ALI} files and this is why they
18598 constitute a mandatory part of GNAT libraries. Except in the case of
18599 @emph{stand-alone libraries}, where a specific library elaboration routine is
18600 produced independently of the application(s) using the library.
18602 @node General Ada Libraries
18603 @section General Ada Libraries
18606 * Building a library::
18607 * Installing a library::
18608 * Using a library::
18611 @node Building a library
18612 @subsection Building a library
18615 The easiest way to build a library is to use the Project Manager,
18616 which supports a special type of project called a @emph{Library Project}
18617 (@pxref{Library Projects}).
18619 A project is considered a library project, when two project-level attributes
18620 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18621 control different aspects of library configuration, additional optional
18622 project-level attributes can be specified:
18625 This attribute controls whether the library is to be static or dynamic
18627 @item Library_Version
18628 This attribute specifies the library version; this value is used
18629 during dynamic linking of shared libraries to determine if the currently
18630 installed versions of the binaries are compatible.
18632 @item Library_Options
18634 These attributes specify additional low-level options to be used during
18635 library generation, and redefine the actual application used to generate
18640 The GNAT Project Manager takes full care of the library maintenance task,
18641 including recompilation of the source files for which objects do not exist
18642 or are not up to date, assembly of the library archive, and installation of
18643 the library (i.e., copying associated source, object and @file{ALI} files
18644 to the specified location).
18646 Here is a simple library project file:
18647 @smallexample @c ada
18649 for Source_Dirs use ("src1", "src2");
18650 for Object_Dir use "obj";
18651 for Library_Name use "mylib";
18652 for Library_Dir use "lib";
18653 for Library_Kind use "dynamic";
18658 and the compilation command to build and install the library:
18660 @smallexample @c ada
18661 $ gnatmake -Pmy_lib
18665 It is not entirely trivial to perform manually all the steps required to
18666 produce a library. We recommend that you use the GNAT Project Manager
18667 for this task. In special cases where this is not desired, the necessary
18668 steps are discussed below.
18670 There are various possibilities for compiling the units that make up the
18671 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
18672 with a conventional script. For simple libraries, it is also possible to create
18673 a dummy main program which depends upon all the packages that comprise the
18674 interface of the library. This dummy main program can then be given to
18675 @command{gnatmake}, which will ensure that all necessary objects are built.
18677 After this task is accomplished, you should follow the standard procedure
18678 of the underlying operating system to produce the static or shared library.
18680 Here is an example of such a dummy program:
18681 @smallexample @c ada
18683 with My_Lib.Service1;
18684 with My_Lib.Service2;
18685 with My_Lib.Service3;
18686 procedure My_Lib_Dummy is
18694 Here are the generic commands that will build an archive or a shared library.
18697 # compiling the library
18698 $ gnatmake -c my_lib_dummy.adb
18700 # we don't need the dummy object itself
18701 $ rm my_lib_dummy.o my_lib_dummy.ali
18703 # create an archive with the remaining objects
18704 $ ar rc libmy_lib.a *.o
18705 # some systems may require "ranlib" to be run as well
18707 # or create a shared library
18708 $ gcc -shared -o libmy_lib.so *.o
18709 # some systems may require the code to have been compiled with -fPIC
18711 # remove the object files that are now in the library
18714 # Make the ALI files read-only so that gnatmake will not try to
18715 # regenerate the objects that are in the library
18720 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
18721 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
18722 be accessed by the directive @option{-l@var{xxx}} at link time.
18724 @node Installing a library
18725 @subsection Installing a library
18726 @cindex @code{ADA_PROJECT_PATH}
18729 If you use project files, library installation is part of the library build
18730 process. Thus no further action is needed in order to make use of the
18731 libraries that are built as part of the general application build. A usable
18732 version of the library is installed in the directory specified by the
18733 @code{Library_Dir} attribute of the library project file.
18735 You may want to install a library in a context different from where the library
18736 is built. This situation arises with third party suppliers, who may want
18737 to distribute a library in binary form where the user is not expected to be
18738 able to recompile the library. The simplest option in this case is to provide
18739 a project file slightly different from the one used to build the library, by
18740 using the @code{externally_built} attribute. For instance, the project
18741 file used to build the library in the previous section can be changed into the
18742 following one when the library is installed:
18744 @smallexample @c projectfile
18746 for Source_Dirs use ("src1", "src2");
18747 for Library_Name use "mylib";
18748 for Library_Dir use "lib";
18749 for Library_Kind use "dynamic";
18750 for Externally_Built use "true";
18755 This project file assumes that the directories @file{src1},
18756 @file{src2}, and @file{lib} exist in
18757 the directory containing the project file. The @code{externally_built}
18758 attribute makes it clear to the GNAT builder that it should not attempt to
18759 recompile any of the units from this library. It allows the library provider to
18760 restrict the source set to the minimum necessary for clients to make use of the
18761 library as described in the first section of this chapter. It is the
18762 responsibility of the library provider to install the necessary sources, ALI
18763 files and libraries in the directories mentioned in the project file. For
18764 convenience, the user's library project file should be installed in a location
18765 that will be searched automatically by the GNAT
18766 builder. These are the directories referenced in the @env{ADA_PROJECT_PATH}
18767 environment variable (@pxref{Importing Projects}), and also the default GNAT
18768 library location that can be queried with @command{gnatls -v} and is usually of
18769 the form $gnat_install_root/lib/gnat.
18771 When project files are not an option, it is also possible, but not recommended,
18772 to install the library so that the sources needed to use the library are on the
18773 Ada source path and the ALI files & libraries be on the Ada Object path (see
18774 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
18775 administrator can place general-purpose libraries in the default compiler
18776 paths, by specifying the libraries' location in the configuration files
18777 @file{ada_source_path} and @file{ada_object_path}. These configuration files
18778 must be located in the GNAT installation tree at the same place as the gcc spec
18779 file. The location of the gcc spec file can be determined as follows:
18785 The configuration files mentioned above have a simple format: each line
18786 must contain one unique directory name.
18787 Those names are added to the corresponding path
18788 in their order of appearance in the file. The names can be either absolute
18789 or relative; in the latter case, they are relative to where theses files
18792 The files @file{ada_source_path} and @file{ada_object_path} might not be
18794 GNAT installation, in which case, GNAT will look for its run-time library in
18795 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
18796 objects and @file{ALI} files). When the files exist, the compiler does not
18797 look in @file{adainclude} and @file{adalib}, and thus the
18798 @file{ada_source_path} file
18799 must contain the location for the GNAT run-time sources (which can simply
18800 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
18801 contain the location for the GNAT run-time objects (which can simply
18804 You can also specify a new default path to the run-time library at compilation
18805 time with the switch @option{--RTS=rts-path}. You can thus choose / change
18806 the run-time library you want your program to be compiled with. This switch is
18807 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
18808 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
18810 It is possible to install a library before or after the standard GNAT
18811 library, by reordering the lines in the configuration files. In general, a
18812 library must be installed before the GNAT library if it redefines
18815 @node Using a library
18816 @subsection Using a library
18818 @noindent Once again, the project facility greatly simplifies the use of
18819 libraries. In this context, using a library is just a matter of adding a
18820 @code{with} clause in the user project. For instance, to make use of the
18821 library @code{My_Lib} shown in examples in earlier sections, you can
18824 @smallexample @c projectfile
18831 Even if you have a third-party, non-Ada library, you can still use GNAT's
18832 Project Manager facility to provide a wrapper for it. For example, the
18833 following project, when @code{with}ed by your main project, will link with the
18834 third-party library @file{liba.a}:
18836 @smallexample @c projectfile
18839 for Externally_Built use "true";
18840 for Source_Files use ();
18841 for Library_Dir use "lib";
18842 for Library_Name use "a";
18843 for Library_Kind use "static";
18847 This is an alternative to the use of @code{pragma Linker_Options}. It is
18848 especially interesting in the context of systems with several interdependent
18849 static libraries where finding a proper linker order is not easy and best be
18850 left to the tools having visibility over project dependence information.
18853 In order to use an Ada library manually, you need to make sure that this
18854 library is on both your source and object path
18855 (see @ref{Search Paths and the Run-Time Library (RTL)}
18856 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
18857 in an archive or a shared library, you need to specify the desired
18858 library at link time.
18860 For example, you can use the library @file{mylib} installed in
18861 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
18864 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
18869 This can be expressed more simply:
18874 when the following conditions are met:
18877 @file{/dir/my_lib_src} has been added by the user to the environment
18878 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
18879 @file{ada_source_path}
18881 @file{/dir/my_lib_obj} has been added by the user to the environment
18882 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
18883 @file{ada_object_path}
18885 a pragma @code{Linker_Options} has been added to one of the sources.
18888 @smallexample @c ada
18889 pragma Linker_Options ("-lmy_lib");
18893 @node Stand-alone Ada Libraries
18894 @section Stand-alone Ada Libraries
18895 @cindex Stand-alone library, building, using
18898 * Introduction to Stand-alone Libraries::
18899 * Building a Stand-alone Library::
18900 * Creating a Stand-alone Library to be used in a non-Ada context::
18901 * Restrictions in Stand-alone Libraries::
18904 @node Introduction to Stand-alone Libraries
18905 @subsection Introduction to Stand-alone Libraries
18908 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
18910 elaborate the Ada units that are included in the library. In contrast with
18911 an ordinary library, which consists of all sources, objects and @file{ALI}
18913 library, a SAL may specify a restricted subset of compilation units
18914 to serve as a library interface. In this case, the fully
18915 self-sufficient set of files will normally consist of an objects
18916 archive, the sources of interface units' specs, and the @file{ALI}
18917 files of interface units.
18918 If an interface spec contains a generic unit or an inlined subprogram,
18920 source must also be provided; if the units that must be provided in the source
18921 form depend on other units, the source and @file{ALI} files of those must
18924 The main purpose of a SAL is to minimize the recompilation overhead of client
18925 applications when a new version of the library is installed. Specifically,
18926 if the interface sources have not changed, client applications do not need to
18927 be recompiled. If, furthermore, a SAL is provided in the shared form and its
18928 version, controlled by @code{Library_Version} attribute, is not changed,
18929 then the clients do not need to be relinked.
18931 SALs also allow the library providers to minimize the amount of library source
18932 text exposed to the clients. Such ``information hiding'' might be useful or
18933 necessary for various reasons.
18935 Stand-alone libraries are also well suited to be used in an executable whose
18936 main routine is not written in Ada.
18938 @node Building a Stand-alone Library
18939 @subsection Building a Stand-alone Library
18942 GNAT's Project facility provides a simple way of building and installing
18943 stand-alone libraries; see @ref{Stand-alone Library Projects}.
18944 To be a Stand-alone Library Project, in addition to the two attributes
18945 that make a project a Library Project (@code{Library_Name} and
18946 @code{Library_Dir}; see @ref{Library Projects}), the attribute
18947 @code{Library_Interface} must be defined. For example:
18949 @smallexample @c projectfile
18951 for Library_Dir use "lib_dir";
18952 for Library_Name use "dummy";
18953 for Library_Interface use ("int1", "int1.child");
18958 Attribute @code{Library_Interface} has a non-empty string list value,
18959 each string in the list designating a unit contained in an immediate source
18960 of the project file.
18962 When a Stand-alone Library is built, first the binder is invoked to build
18963 a package whose name depends on the library name
18964 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
18965 This binder-generated package includes initialization and
18966 finalization procedures whose
18967 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
18969 above). The object corresponding to this package is included in the library.
18971 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
18972 calling of these procedures if a static SAL is built, or if a shared SAL
18974 with the project-level attribute @code{Library_Auto_Init} set to
18977 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
18978 (those that are listed in attribute @code{Library_Interface}) are copied to
18979 the Library Directory. As a consequence, only the Interface Units may be
18980 imported from Ada units outside of the library. If other units are imported,
18981 the binding phase will fail.
18983 The attribute @code{Library_Src_Dir} may be specified for a
18984 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
18985 single string value. Its value must be the path (absolute or relative to the
18986 project directory) of an existing directory. This directory cannot be the
18987 object directory or one of the source directories, but it can be the same as
18988 the library directory. The sources of the Interface
18989 Units of the library that are needed by an Ada client of the library will be
18990 copied to the designated directory, called the Interface Copy directory.
18991 These sources include the specs of the Interface Units, but they may also
18992 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
18993 are used, or when there is a generic unit in the spec. Before the sources
18994 are copied to the Interface Copy directory, an attempt is made to delete all
18995 files in the Interface Copy directory.
18997 Building stand-alone libraries by hand is somewhat tedious, but for those
18998 occasions when it is necessary here are the steps that you need to perform:
19001 Compile all library sources.
19004 Invoke the binder with the switch @option{-n} (No Ada main program),
19005 with all the @file{ALI} files of the interfaces, and
19006 with the switch @option{-L} to give specific names to the @code{init}
19007 and @code{final} procedures. For example:
19009 gnatbind -n int1.ali int2.ali -Lsal1
19013 Compile the binder generated file:
19019 Link the dynamic library with all the necessary object files,
19020 indicating to the linker the names of the @code{init} (and possibly
19021 @code{final}) procedures for automatic initialization (and finalization).
19022 The built library should be placed in a directory different from
19023 the object directory.
19026 Copy the @code{ALI} files of the interface to the library directory,
19027 add in this copy an indication that it is an interface to a SAL
19028 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19029 with letter ``P'') and make the modified copy of the @file{ALI} file
19034 Using SALs is not different from using other libraries
19035 (see @ref{Using a library}).
19037 @node Creating a Stand-alone Library to be used in a non-Ada context
19038 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19041 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19044 The only extra step required is to ensure that library interface subprograms
19045 are compatible with the main program, by means of @code{pragma Export}
19046 or @code{pragma Convention}.
19048 Here is an example of simple library interface for use with C main program:
19050 @smallexample @c ada
19051 package Interface is
19053 procedure Do_Something;
19054 pragma Export (C, Do_Something, "do_something");
19056 procedure Do_Something_Else;
19057 pragma Export (C, Do_Something_Else, "do_something_else");
19063 On the foreign language side, you must provide a ``foreign'' view of the
19064 library interface; remember that it should contain elaboration routines in
19065 addition to interface subprograms.
19067 The example below shows the content of @code{mylib_interface.h} (note
19068 that there is no rule for the naming of this file, any name can be used)
19070 /* the library elaboration procedure */
19071 extern void mylibinit (void);
19073 /* the library finalization procedure */
19074 extern void mylibfinal (void);
19076 /* the interface exported by the library */
19077 extern void do_something (void);
19078 extern void do_something_else (void);
19082 Libraries built as explained above can be used from any program, provided
19083 that the elaboration procedures (named @code{mylibinit} in the previous
19084 example) are called before the library services are used. Any number of
19085 libraries can be used simultaneously, as long as the elaboration
19086 procedure of each library is called.
19088 Below is an example of a C program that uses the @code{mylib} library.
19091 #include "mylib_interface.h"
19096 /* First, elaborate the library before using it */
19099 /* Main program, using the library exported entities */
19101 do_something_else ();
19103 /* Library finalization at the end of the program */
19110 Note that invoking any library finalization procedure generated by
19111 @code{gnatbind} shuts down the Ada run-time environment.
19113 finalization of all Ada libraries must be performed at the end of the program.
19114 No call to these libraries or to the Ada run-time library should be made
19115 after the finalization phase.
19117 @node Restrictions in Stand-alone Libraries
19118 @subsection Restrictions in Stand-alone Libraries
19121 The pragmas listed below should be used with caution inside libraries,
19122 as they can create incompatibilities with other Ada libraries:
19124 @item pragma @code{Locking_Policy}
19125 @item pragma @code{Queuing_Policy}
19126 @item pragma @code{Task_Dispatching_Policy}
19127 @item pragma @code{Unreserve_All_Interrupts}
19131 When using a library that contains such pragmas, the user must make sure
19132 that all libraries use the same pragmas with the same values. Otherwise,
19133 @code{Program_Error} will
19134 be raised during the elaboration of the conflicting
19135 libraries. The usage of these pragmas and its consequences for the user
19136 should therefore be well documented.
19138 Similarly, the traceback in the exception occurrence mechanism should be
19139 enabled or disabled in a consistent manner across all libraries.
19140 Otherwise, Program_Error will be raised during the elaboration of the
19141 conflicting libraries.
19143 If the @code{Version} or @code{Body_Version}
19144 attributes are used inside a library, then you need to
19145 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19146 libraries, so that version identifiers can be properly computed.
19147 In practice these attributes are rarely used, so this is unlikely
19148 to be a consideration.
19150 @node Rebuilding the GNAT Run-Time Library
19151 @section Rebuilding the GNAT Run-Time Library
19152 @cindex GNAT Run-Time Library, rebuilding
19153 @cindex Building the GNAT Run-Time Library
19154 @cindex Rebuilding the GNAT Run-Time Library
19155 @cindex Run-Time Library, rebuilding
19158 It may be useful to recompile the GNAT library in various contexts, the
19159 most important one being the use of partition-wide configuration pragmas
19160 such as @code{Normalize_Scalars}. A special Makefile called
19161 @code{Makefile.adalib} is provided to that effect and can be found in
19162 the directory containing the GNAT library. The location of this
19163 directory depends on the way the GNAT environment has been installed and can
19164 be determined by means of the command:
19171 The last entry in the object search path usually contains the
19172 gnat library. This Makefile contains its own documentation and in
19173 particular the set of instructions needed to rebuild a new library and
19176 @node Using the GNU make Utility
19177 @chapter Using the GNU @code{make} Utility
19181 This chapter offers some examples of makefiles that solve specific
19182 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19183 make, make, GNU @code{make}}), nor does it try to replace the
19184 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19186 All the examples in this section are specific to the GNU version of
19187 make. Although @command{make} is a standard utility, and the basic language
19188 is the same, these examples use some advanced features found only in
19192 * Using gnatmake in a Makefile::
19193 * Automatically Creating a List of Directories::
19194 * Generating the Command Line Switches::
19195 * Overcoming Command Line Length Limits::
19198 @node Using gnatmake in a Makefile
19199 @section Using gnatmake in a Makefile
19204 Complex project organizations can be handled in a very powerful way by
19205 using GNU make combined with gnatmake. For instance, here is a Makefile
19206 which allows you to build each subsystem of a big project into a separate
19207 shared library. Such a makefile allows you to significantly reduce the link
19208 time of very big applications while maintaining full coherence at
19209 each step of the build process.
19211 The list of dependencies are handled automatically by
19212 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19213 the appropriate directories.
19215 Note that you should also read the example on how to automatically
19216 create the list of directories
19217 (@pxref{Automatically Creating a List of Directories})
19218 which might help you in case your project has a lot of subdirectories.
19223 @font@heightrm=cmr8
19226 ## This Makefile is intended to be used with the following directory
19228 ## - The sources are split into a series of csc (computer software components)
19229 ## Each of these csc is put in its own directory.
19230 ## Their name are referenced by the directory names.
19231 ## They will be compiled into shared library (although this would also work
19232 ## with static libraries
19233 ## - The main program (and possibly other packages that do not belong to any
19234 ## csc is put in the top level directory (where the Makefile is).
19235 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19236 ## \_ second_csc (sources) __ lib (will contain the library)
19238 ## Although this Makefile is build for shared library, it is easy to modify
19239 ## to build partial link objects instead (modify the lines with -shared and
19242 ## With this makefile, you can change any file in the system or add any new
19243 ## file, and everything will be recompiled correctly (only the relevant shared
19244 ## objects will be recompiled, and the main program will be re-linked).
19246 # The list of computer software component for your project. This might be
19247 # generated automatically.
19250 # Name of the main program (no extension)
19253 # If we need to build objects with -fPIC, uncomment the following line
19256 # The following variable should give the directory containing libgnat.so
19257 # You can get this directory through 'gnatls -v'. This is usually the last
19258 # directory in the Object_Path.
19261 # The directories for the libraries
19262 # (This macro expands the list of CSC to the list of shared libraries, you
19263 # could simply use the expanded form:
19264 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19265 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19267 $@{MAIN@}: objects $@{LIB_DIR@}
19268 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19269 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19272 # recompile the sources
19273 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19275 # Note: In a future version of GNAT, the following commands will be simplified
19276 # by a new tool, gnatmlib
19278 mkdir -p $@{dir $@@ @}
19279 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19280 cd $@{dir $@@ @} && cp -f ../*.ali .
19282 # The dependencies for the modules
19283 # Note that we have to force the expansion of *.o, since in some cases
19284 # make won't be able to do it itself.
19285 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19286 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19287 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19289 # Make sure all of the shared libraries are in the path before starting the
19292 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19295 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19296 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19297 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19298 $@{RM@} *.o *.ali $@{MAIN@}
19301 @node Automatically Creating a List of Directories
19302 @section Automatically Creating a List of Directories
19305 In most makefiles, you will have to specify a list of directories, and
19306 store it in a variable. For small projects, it is often easier to
19307 specify each of them by hand, since you then have full control over what
19308 is the proper order for these directories, which ones should be
19311 However, in larger projects, which might involve hundreds of
19312 subdirectories, it might be more convenient to generate this list
19315 The example below presents two methods. The first one, although less
19316 general, gives you more control over the list. It involves wildcard
19317 characters, that are automatically expanded by @command{make}. Its
19318 shortcoming is that you need to explicitly specify some of the
19319 organization of your project, such as for instance the directory tree
19320 depth, whether some directories are found in a separate tree, @enddots{}
19322 The second method is the most general one. It requires an external
19323 program, called @command{find}, which is standard on all Unix systems. All
19324 the directories found under a given root directory will be added to the
19330 @font@heightrm=cmr8
19333 # The examples below are based on the following directory hierarchy:
19334 # All the directories can contain any number of files
19335 # ROOT_DIRECTORY -> a -> aa -> aaa
19338 # -> b -> ba -> baa
19341 # This Makefile creates a variable called DIRS, that can be reused any time
19342 # you need this list (see the other examples in this section)
19344 # The root of your project's directory hierarchy
19348 # First method: specify explicitly the list of directories
19349 # This allows you to specify any subset of all the directories you need.
19352 DIRS := a/aa/ a/ab/ b/ba/
19355 # Second method: use wildcards
19356 # Note that the argument(s) to wildcard below should end with a '/'.
19357 # Since wildcards also return file names, we have to filter them out
19358 # to avoid duplicate directory names.
19359 # We thus use make's @code{dir} and @code{sort} functions.
19360 # It sets DIRs to the following value (note that the directories aaa and baa
19361 # are not given, unless you change the arguments to wildcard).
19362 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19365 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19366 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19369 # Third method: use an external program
19370 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19371 # This is the most complete command: it sets DIRs to the following value:
19372 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19375 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19379 @node Generating the Command Line Switches
19380 @section Generating the Command Line Switches
19383 Once you have created the list of directories as explained in the
19384 previous section (@pxref{Automatically Creating a List of Directories}),
19385 you can easily generate the command line arguments to pass to gnatmake.
19387 For the sake of completeness, this example assumes that the source path
19388 is not the same as the object path, and that you have two separate lists
19392 # see "Automatically creating a list of directories" to create
19397 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19398 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19401 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19404 @node Overcoming Command Line Length Limits
19405 @section Overcoming Command Line Length Limits
19408 One problem that might be encountered on big projects is that many
19409 operating systems limit the length of the command line. It is thus hard to give
19410 gnatmake the list of source and object directories.
19412 This example shows how you can set up environment variables, which will
19413 make @command{gnatmake} behave exactly as if the directories had been
19414 specified on the command line, but have a much higher length limit (or
19415 even none on most systems).
19417 It assumes that you have created a list of directories in your Makefile,
19418 using one of the methods presented in
19419 @ref{Automatically Creating a List of Directories}.
19420 For the sake of completeness, we assume that the object
19421 path (where the ALI files are found) is different from the sources patch.
19423 Note a small trick in the Makefile below: for efficiency reasons, we
19424 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19425 expanded immediately by @code{make}. This way we overcome the standard
19426 make behavior which is to expand the variables only when they are
19429 On Windows, if you are using the standard Windows command shell, you must
19430 replace colons with semicolons in the assignments to these variables.
19435 @font@heightrm=cmr8
19438 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19439 # This is the same thing as putting the -I arguments on the command line.
19440 # (the equivalent of using -aI on the command line would be to define
19441 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19442 # You can of course have different values for these variables.
19444 # Note also that we need to keep the previous values of these variables, since
19445 # they might have been set before running 'make' to specify where the GNAT
19446 # library is installed.
19448 # see "Automatically creating a list of directories" to create these
19454 space:=$@{empty@} $@{empty@}
19455 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19456 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19457 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19458 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19459 export ADA_INCLUDE_PATH
19460 export ADA_OBJECT_PATH
19467 @node Memory Management Issues
19468 @chapter Memory Management Issues
19471 This chapter describes some useful memory pools provided in the GNAT library
19472 and in particular the GNAT Debug Pool facility, which can be used to detect
19473 incorrect uses of access values (including ``dangling references'').
19475 It also describes the @command{gnatmem} tool, which can be used to track down
19480 * Some Useful Memory Pools::
19481 * The GNAT Debug Pool Facility::
19483 * The gnatmem Tool::
19487 @node Some Useful Memory Pools
19488 @section Some Useful Memory Pools
19489 @findex Memory Pool
19490 @cindex storage, pool
19493 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19494 storage pool. Allocations use the standard system call @code{malloc} while
19495 deallocations use the standard system call @code{free}. No reclamation is
19496 performed when the pool goes out of scope. For performance reasons, the
19497 standard default Ada allocators/deallocators do not use any explicit storage
19498 pools but if they did, they could use this storage pool without any change in
19499 behavior. That is why this storage pool is used when the user
19500 manages to make the default implicit allocator explicit as in this example:
19501 @smallexample @c ada
19502 type T1 is access Something;
19503 -- no Storage pool is defined for T2
19504 type T2 is access Something_Else;
19505 for T2'Storage_Pool use T1'Storage_Pool;
19506 -- the above is equivalent to
19507 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19511 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19512 pool. The allocation strategy is similar to @code{Pool_Local}'s
19513 except that the all
19514 storage allocated with this pool is reclaimed when the pool object goes out of
19515 scope. This pool provides a explicit mechanism similar to the implicit one
19516 provided by several Ada 83 compilers for allocations performed through a local
19517 access type and whose purpose was to reclaim memory when exiting the
19518 scope of a given local access. As an example, the following program does not
19519 leak memory even though it does not perform explicit deallocation:
19521 @smallexample @c ada
19522 with System.Pool_Local;
19523 procedure Pooloc1 is
19524 procedure Internal is
19525 type A is access Integer;
19526 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19527 for A'Storage_Pool use X;
19530 for I in 1 .. 50 loop
19535 for I in 1 .. 100 loop
19542 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19543 @code{Storage_Size} is specified for an access type.
19544 The whole storage for the pool is
19545 allocated at once, usually on the stack at the point where the access type is
19546 elaborated. It is automatically reclaimed when exiting the scope where the
19547 access type is defined. This package is not intended to be used directly by the
19548 user and it is implicitly used for each such declaration:
19550 @smallexample @c ada
19551 type T1 is access Something;
19552 for T1'Storage_Size use 10_000;
19555 @node The GNAT Debug Pool Facility
19556 @section The GNAT Debug Pool Facility
19558 @cindex storage, pool, memory corruption
19561 The use of unchecked deallocation and unchecked conversion can easily
19562 lead to incorrect memory references. The problems generated by such
19563 references are usually difficult to tackle because the symptoms can be
19564 very remote from the origin of the problem. In such cases, it is
19565 very helpful to detect the problem as early as possible. This is the
19566 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19568 In order to use the GNAT specific debugging pool, the user must
19569 associate a debug pool object with each of the access types that may be
19570 related to suspected memory problems. See Ada Reference Manual 13.11.
19571 @smallexample @c ada
19572 type Ptr is access Some_Type;
19573 Pool : GNAT.Debug_Pools.Debug_Pool;
19574 for Ptr'Storage_Pool use Pool;
19578 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19579 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19580 allow the user to redefine allocation and deallocation strategies. They
19581 also provide a checkpoint for each dereference, through the use of
19582 the primitive operation @code{Dereference} which is implicitly called at
19583 each dereference of an access value.
19585 Once an access type has been associated with a debug pool, operations on
19586 values of the type may raise four distinct exceptions,
19587 which correspond to four potential kinds of memory corruption:
19590 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19592 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19594 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19596 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19600 For types associated with a Debug_Pool, dynamic allocation is performed using
19601 the standard GNAT allocation routine. References to all allocated chunks of
19602 memory are kept in an internal dictionary. Several deallocation strategies are
19603 provided, whereupon the user can choose to release the memory to the system,
19604 keep it allocated for further invalid access checks, or fill it with an easily
19605 recognizable pattern for debug sessions. The memory pattern is the old IBM
19606 hexadecimal convention: @code{16#DEADBEEF#}.
19608 See the documentation in the file g-debpoo.ads for more information on the
19609 various strategies.
19611 Upon each dereference, a check is made that the access value denotes a
19612 properly allocated memory location. Here is a complete example of use of
19613 @code{Debug_Pools}, that includes typical instances of memory corruption:
19614 @smallexample @c ada
19618 with Gnat.Io; use Gnat.Io;
19619 with Unchecked_Deallocation;
19620 with Unchecked_Conversion;
19621 with GNAT.Debug_Pools;
19622 with System.Storage_Elements;
19623 with Ada.Exceptions; use Ada.Exceptions;
19624 procedure Debug_Pool_Test is
19626 type T is access Integer;
19627 type U is access all T;
19629 P : GNAT.Debug_Pools.Debug_Pool;
19630 for T'Storage_Pool use P;
19632 procedure Free is new Unchecked_Deallocation (Integer, T);
19633 function UC is new Unchecked_Conversion (U, T);
19636 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
19646 Put_Line (Integer'Image(B.all));
19648 when E : others => Put_Line ("raised: " & Exception_Name (E));
19653 when E : others => Put_Line ("raised: " & Exception_Name (E));
19657 Put_Line (Integer'Image(B.all));
19659 when E : others => Put_Line ("raised: " & Exception_Name (E));
19664 when E : others => Put_Line ("raised: " & Exception_Name (E));
19667 end Debug_Pool_Test;
19671 The debug pool mechanism provides the following precise diagnostics on the
19672 execution of this erroneous program:
19675 Total allocated bytes : 0
19676 Total deallocated bytes : 0
19677 Current Water Mark: 0
19681 Total allocated bytes : 8
19682 Total deallocated bytes : 0
19683 Current Water Mark: 8
19686 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
19687 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
19688 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
19689 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
19691 Total allocated bytes : 8
19692 Total deallocated bytes : 4
19693 Current Water Mark: 4
19698 @node The gnatmem Tool
19699 @section The @command{gnatmem} Tool
19703 The @code{gnatmem} utility monitors dynamic allocation and
19704 deallocation activity in a program, and displays information about
19705 incorrect deallocations and possible sources of memory leaks.
19706 It provides three type of information:
19709 General information concerning memory management, such as the total
19710 number of allocations and deallocations, the amount of allocated
19711 memory and the high water mark, i.e.@: the largest amount of allocated
19712 memory in the course of program execution.
19715 Backtraces for all incorrect deallocations, that is to say deallocations
19716 which do not correspond to a valid allocation.
19719 Information on each allocation that is potentially the origin of a memory
19724 * Running gnatmem::
19725 * Switches for gnatmem::
19726 * Example of gnatmem Usage::
19729 @node Running gnatmem
19730 @subsection Running @code{gnatmem}
19733 @code{gnatmem} makes use of the output created by the special version of
19734 allocation and deallocation routines that record call information. This
19735 allows to obtain accurate dynamic memory usage history at a minimal cost to
19736 the execution speed. Note however, that @code{gnatmem} is not supported on
19737 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
19738 Solaris and Windows NT/2000/XP (x86).
19741 The @code{gnatmem} command has the form
19744 $ gnatmem @ovar{switches} user_program
19748 The program must have been linked with the instrumented version of the
19749 allocation and deallocation routines. This is done by linking with the
19750 @file{libgmem.a} library. For correct symbolic backtrace information,
19751 the user program should be compiled with debugging options
19752 (see @ref{Switches for gcc}). For example to build @file{my_program}:
19755 $ gnatmake -g my_program -largs -lgmem
19759 As library @file{libgmem.a} contains an alternate body for package
19760 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
19761 when an executable is linked with library @file{libgmem.a}. It is then not
19762 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
19765 When @file{my_program} is executed, the file @file{gmem.out} is produced.
19766 This file contains information about all allocations and deallocations
19767 performed by the program. It is produced by the instrumented allocations and
19768 deallocations routines and will be used by @code{gnatmem}.
19770 In order to produce symbolic backtrace information for allocations and
19771 deallocations performed by the GNAT run-time library, you need to use a
19772 version of that library that has been compiled with the @option{-g} switch
19773 (see @ref{Rebuilding the GNAT Run-Time Library}).
19775 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
19776 examine. If the location of @file{gmem.out} file was not explicitly supplied by
19777 @option{-i} switch, gnatmem will assume that this file can be found in the
19778 current directory. For example, after you have executed @file{my_program},
19779 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
19782 $ gnatmem my_program
19786 This will produce the output with the following format:
19788 *************** debut cc
19790 $ gnatmem my_program
19794 Total number of allocations : 45
19795 Total number of deallocations : 6
19796 Final Water Mark (non freed mem) : 11.29 Kilobytes
19797 High Water Mark : 11.40 Kilobytes
19802 Allocation Root # 2
19803 -------------------
19804 Number of non freed allocations : 11
19805 Final Water Mark (non freed mem) : 1.16 Kilobytes
19806 High Water Mark : 1.27 Kilobytes
19808 my_program.adb:23 my_program.alloc
19814 The first block of output gives general information. In this case, the
19815 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
19816 Unchecked_Deallocation routine occurred.
19819 Subsequent paragraphs display information on all allocation roots.
19820 An allocation root is a specific point in the execution of the program
19821 that generates some dynamic allocation, such as a ``@code{@b{new}}''
19822 construct. This root is represented by an execution backtrace (or subprogram
19823 call stack). By default the backtrace depth for allocations roots is 1, so
19824 that a root corresponds exactly to a source location. The backtrace can
19825 be made deeper, to make the root more specific.
19827 @node Switches for gnatmem
19828 @subsection Switches for @code{gnatmem}
19831 @code{gnatmem} recognizes the following switches:
19836 @cindex @option{-q} (@code{gnatmem})
19837 Quiet. Gives the minimum output needed to identify the origin of the
19838 memory leaks. Omits statistical information.
19841 @cindex @var{N} (@code{gnatmem})
19842 N is an integer literal (usually between 1 and 10) which controls the
19843 depth of the backtraces defining allocation root. The default value for
19844 N is 1. The deeper the backtrace, the more precise the localization of
19845 the root. Note that the total number of roots can depend on this
19846 parameter. This parameter must be specified @emph{before} the name of the
19847 executable to be analyzed, to avoid ambiguity.
19850 @cindex @option{-b} (@code{gnatmem})
19851 This switch has the same effect as just depth parameter.
19853 @item -i @var{file}
19854 @cindex @option{-i} (@code{gnatmem})
19855 Do the @code{gnatmem} processing starting from @file{file}, rather than
19856 @file{gmem.out} in the current directory.
19859 @cindex @option{-m} (@code{gnatmem})
19860 This switch causes @code{gnatmem} to mask the allocation roots that have less
19861 than n leaks. The default value is 1. Specifying the value of 0 will allow to
19862 examine even the roots that didn't result in leaks.
19865 @cindex @option{-s} (@code{gnatmem})
19866 This switch causes @code{gnatmem} to sort the allocation roots according to the
19867 specified order of sort criteria, each identified by a single letter. The
19868 currently supported criteria are @code{n, h, w} standing respectively for
19869 number of unfreed allocations, high watermark, and final watermark
19870 corresponding to a specific root. The default order is @code{nwh}.
19874 @node Example of gnatmem Usage
19875 @subsection Example of @code{gnatmem} Usage
19878 The following example shows the use of @code{gnatmem}
19879 on a simple memory-leaking program.
19880 Suppose that we have the following Ada program:
19882 @smallexample @c ada
19885 with Unchecked_Deallocation;
19886 procedure Test_Gm is
19888 type T is array (1..1000) of Integer;
19889 type Ptr is access T;
19890 procedure Free is new Unchecked_Deallocation (T, Ptr);
19893 procedure My_Alloc is
19898 procedure My_DeAlloc is
19906 for I in 1 .. 5 loop
19907 for J in I .. 5 loop
19918 The program needs to be compiled with debugging option and linked with
19919 @code{gmem} library:
19922 $ gnatmake -g test_gm -largs -lgmem
19926 Then we execute the program as usual:
19933 Then @code{gnatmem} is invoked simply with
19939 which produces the following output (result may vary on different platforms):
19944 Total number of allocations : 18
19945 Total number of deallocations : 5
19946 Final Water Mark (non freed mem) : 53.00 Kilobytes
19947 High Water Mark : 56.90 Kilobytes
19949 Allocation Root # 1
19950 -------------------
19951 Number of non freed allocations : 11
19952 Final Water Mark (non freed mem) : 42.97 Kilobytes
19953 High Water Mark : 46.88 Kilobytes
19955 test_gm.adb:11 test_gm.my_alloc
19957 Allocation Root # 2
19958 -------------------
19959 Number of non freed allocations : 1
19960 Final Water Mark (non freed mem) : 10.02 Kilobytes
19961 High Water Mark : 10.02 Kilobytes
19963 s-secsta.adb:81 system.secondary_stack.ss_init
19965 Allocation Root # 3
19966 -------------------
19967 Number of non freed allocations : 1
19968 Final Water Mark (non freed mem) : 12 Bytes
19969 High Water Mark : 12 Bytes
19971 s-secsta.adb:181 system.secondary_stack.ss_init
19975 Note that the GNAT run time contains itself a certain number of
19976 allocations that have no corresponding deallocation,
19977 as shown here for root #2 and root
19978 #3. This is a normal behavior when the number of non-freed allocations
19979 is one, it allocates dynamic data structures that the run time needs for
19980 the complete lifetime of the program. Note also that there is only one
19981 allocation root in the user program with a single line back trace:
19982 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
19983 program shows that 'My_Alloc' is called at 2 different points in the
19984 source (line 21 and line 24). If those two allocation roots need to be
19985 distinguished, the backtrace depth parameter can be used:
19988 $ gnatmem 3 test_gm
19992 which will give the following output:
19997 Total number of allocations : 18
19998 Total number of deallocations : 5
19999 Final Water Mark (non freed mem) : 53.00 Kilobytes
20000 High Water Mark : 56.90 Kilobytes
20002 Allocation Root # 1
20003 -------------------
20004 Number of non freed allocations : 10
20005 Final Water Mark (non freed mem) : 39.06 Kilobytes
20006 High Water Mark : 42.97 Kilobytes
20008 test_gm.adb:11 test_gm.my_alloc
20009 test_gm.adb:24 test_gm
20010 b_test_gm.c:52 main
20012 Allocation Root # 2
20013 -------------------
20014 Number of non freed allocations : 1
20015 Final Water Mark (non freed mem) : 10.02 Kilobytes
20016 High Water Mark : 10.02 Kilobytes
20018 s-secsta.adb:81 system.secondary_stack.ss_init
20019 s-secsta.adb:283 <system__secondary_stack___elabb>
20020 b_test_gm.c:33 adainit
20022 Allocation Root # 3
20023 -------------------
20024 Number of non freed allocations : 1
20025 Final Water Mark (non freed mem) : 3.91 Kilobytes
20026 High Water Mark : 3.91 Kilobytes
20028 test_gm.adb:11 test_gm.my_alloc
20029 test_gm.adb:21 test_gm
20030 b_test_gm.c:52 main
20032 Allocation Root # 4
20033 -------------------
20034 Number of non freed allocations : 1
20035 Final Water Mark (non freed mem) : 12 Bytes
20036 High Water Mark : 12 Bytes
20038 s-secsta.adb:181 system.secondary_stack.ss_init
20039 s-secsta.adb:283 <system__secondary_stack___elabb>
20040 b_test_gm.c:33 adainit
20044 The allocation root #1 of the first example has been split in 2 roots #1
20045 and #3 thanks to the more precise associated backtrace.
20049 @node Stack Related Facilities
20050 @chapter Stack Related Facilities
20053 This chapter describes some useful tools associated with stack
20054 checking and analysis. In
20055 particular, it deals with dynamic and static stack usage measurements.
20058 * Stack Overflow Checking::
20059 * Static Stack Usage Analysis::
20060 * Dynamic Stack Usage Analysis::
20063 @node Stack Overflow Checking
20064 @section Stack Overflow Checking
20065 @cindex Stack Overflow Checking
20066 @cindex -fstack-check
20069 For most operating systems, @command{gcc} does not perform stack overflow
20070 checking by default. This means that if the main environment task or
20071 some other task exceeds the available stack space, then unpredictable
20072 behavior will occur. Most native systems offer some level of protection by
20073 adding a guard page at the end of each task stack. This mechanism is usually
20074 not enough for dealing properly with stack overflow situations because
20075 a large local variable could ``jump'' above the guard page.
20076 Furthermore, when the
20077 guard page is hit, there may not be any space left on the stack for executing
20078 the exception propagation code. Enabling stack checking avoids
20081 To activate stack checking, compile all units with the gcc option
20082 @option{-fstack-check}. For example:
20085 gcc -c -fstack-check package1.adb
20089 Units compiled with this option will generate extra instructions to check
20090 that any use of the stack (for procedure calls or for declaring local
20091 variables in declare blocks) does not exceed the available stack space.
20092 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20094 For declared tasks, the stack size is controlled by the size
20095 given in an applicable @code{Storage_Size} pragma or by the value specified
20096 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20097 the default size as defined in the GNAT runtime otherwise.
20099 For the environment task, the stack size depends on
20100 system defaults and is unknown to the compiler. Stack checking
20101 may still work correctly if a fixed
20102 size stack is allocated, but this cannot be guaranteed.
20104 To ensure that a clean exception is signalled for stack
20105 overflow, set the environment variable
20106 @env{GNAT_STACK_LIMIT} to indicate the maximum
20107 stack area that can be used, as in:
20108 @cindex GNAT_STACK_LIMIT
20111 SET GNAT_STACK_LIMIT 1600
20115 The limit is given in kilobytes, so the above declaration would
20116 set the stack limit of the environment task to 1.6 megabytes.
20117 Note that the only purpose of this usage is to limit the amount
20118 of stack used by the environment task. If it is necessary to
20119 increase the amount of stack for the environment task, then this
20120 is an operating systems issue, and must be addressed with the
20121 appropriate operating systems commands.
20124 To have a fixed size stack in the environment task, the stack must be put
20125 in the P0 address space and its size specified. Use these switches to
20129 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20133 The quotes are required to keep case. The number after @samp{STACK=} is the
20134 size of the environmental task stack in pagelets (512 bytes). In this example
20135 the stack size is about 2 megabytes.
20138 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20139 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20140 more details about the @option{/p0image} qualifier and the @option{stack}
20144 @node Static Stack Usage Analysis
20145 @section Static Stack Usage Analysis
20146 @cindex Static Stack Usage Analysis
20147 @cindex -fstack-usage
20150 A unit compiled with @option{-fstack-usage} will generate an extra file
20152 the maximum amount of stack used, on a per-function basis.
20153 The file has the same
20154 basename as the target object file with a @file{.su} extension.
20155 Each line of this file is made up of three fields:
20159 The name of the function.
20163 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20166 The second field corresponds to the size of the known part of the function
20169 The qualifier @code{static} means that the function frame size
20171 It usually means that all local variables have a static size.
20172 In this case, the second field is a reliable measure of the function stack
20175 The qualifier @code{dynamic} means that the function frame size is not static.
20176 It happens mainly when some local variables have a dynamic size. When this
20177 qualifier appears alone, the second field is not a reliable measure
20178 of the function stack analysis. When it is qualified with @code{bounded}, it
20179 means that the second field is a reliable maximum of the function stack
20182 @node Dynamic Stack Usage Analysis
20183 @section Dynamic Stack Usage Analysis
20186 It is possible to measure the maximum amount of stack used by a task, by
20187 adding a switch to @command{gnatbind}, as:
20190 $ gnatbind -u0 file
20194 With this option, at each task termination, its stack usage is output on
20196 It is not always convenient to output the stack usage when the program
20197 is still running. Hence, it is possible to delay this output until program
20198 termination. for a given number of tasks specified as the argument of the
20199 @option{-u} option. For instance:
20202 $ gnatbind -u100 file
20206 will buffer the stack usage information of the first 100 tasks to terminate and
20207 output this info at program termination. Results are displayed in four
20211 Index | Task Name | Stack Size | Actual Use [min - max]
20218 is a number associated with each task.
20221 is the name of the task analyzed.
20224 is the maximum size for the stack.
20227 is the measure done by the stack analyzer. In order to prevent overflow,
20228 the stack is not entirely analyzed, and it's not possible to know exactly how
20229 much has actually been used. The real amount of stack used is between the min
20235 The environment task stack, e.g., the stack that contains the main unit, is
20236 only processed when the environment variable GNAT_STACK_LIMIT is set.
20239 @c *********************************
20241 @c *********************************
20242 @node Verifying Properties Using gnatcheck
20243 @chapter Verifying Properties Using @command{gnatcheck}
20245 @cindex @command{gnatcheck}
20248 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20249 of Ada source files according to a given set of semantic rules.
20252 In order to check compliance with a given rule, @command{gnatcheck} has to
20253 semantically analyze the Ada sources.
20254 Therefore, checks can only be performed on
20255 legal Ada units. Moreover, when a unit depends semantically upon units located
20256 outside the current directory, the source search path has to be provided when
20257 calling @command{gnatcheck}, either through a specified project file or
20258 through @command{gnatcheck} switches as described below.
20260 A number of rules are predefined in @command{gnatcheck} and are described
20261 later in this chapter.
20262 You can also add new rules, by modifying the @command{gnatcheck} code and
20263 rebuilding the tool. In order to add a simple rule making some local checks,
20264 a small amount of straightforward ASIS-based programming is usually needed.
20266 Project support for @command{gnatcheck} is provided by the GNAT
20267 driver (see @ref{The GNAT Driver and Project Files}).
20269 Invoking @command{gnatcheck} on the command line has the form:
20272 $ gnatcheck @ovar{switches} @{@var{filename}@}
20273 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20274 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20281 @var{switches} specify the general tool options
20284 Each @var{filename} is the name (including the extension) of a source
20285 file to process. ``Wildcards'' are allowed, and
20286 the file name may contain path information.
20289 Each @var{arg_list_filename} is the name (including the extension) of a text
20290 file containing the names of the source files to process, separated by spaces
20294 @var{gcc_switches} is a list of switches for
20295 @command{gcc}. They will be passed on to all compiler invocations made by
20296 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20297 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20298 and use the @option{-gnatec} switch to set the configuration file.
20301 @var{rule_options} is a list of options for controlling a set of
20302 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20306 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20309 * Format of the Report File::
20310 * General gnatcheck Switches::
20311 * gnatcheck Rule Options::
20312 * Adding the Results of Compiler Checks to gnatcheck Output::
20313 * Project-Wide Checks::
20314 * Predefined Rules::
20317 @node Format of the Report File
20318 @section Format of the Report File
20319 @cindex Report file (for @code{gnatcheck})
20322 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20324 It also creates, in the current
20325 directory, a text file named @file{^gnatcheck.out^GNATCHECK.OUT^} that
20326 contains the complete report of the last gnatcheck run. This report contains:
20328 @item a list of the Ada source files being checked,
20329 @item a list of enabled and disabled rules,
20330 @item a list of the diagnostic messages, ordered in three different ways
20331 and collected in three separate
20332 sections. Section 1 contains the raw list of diagnostic messages. It
20333 corresponds to the output going to @file{stdout}. Section 2 contains
20334 messages ordered by rules.
20335 Section 3 contains messages ordered by source files.
20338 @node General gnatcheck Switches
20339 @section General @command{gnatcheck} Switches
20342 The following switches control the general @command{gnatcheck} behavior
20346 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20348 Process all units including those with read-only ALI files such as
20349 those from GNAT Run-Time library.
20353 @cindex @option{-d} (@command{gnatcheck})
20358 @cindex @option{-dd} (@command{gnatcheck})
20360 Progress indicator mode (for use in GPS)
20363 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20365 List the predefined and user-defined rules. For more details see
20366 @ref{Predefined Rules}.
20368 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20370 Use full source locations references in the report file. For a construct from
20371 a generic instantiation a full source location is a chain from the location
20372 of this construct in the generic unit to the place where this unit is
20375 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20376 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20377 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20378 the default value is 500. Zero means that there is no limitation on
20379 the number of diagnostic messages to be printed into Stdout.
20381 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20383 Quiet mode. All the diagnoses about rule violations are placed in the
20384 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20386 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20388 Short format of the report file (no version information, no list of applied
20389 rules, no list of checked sources is included)
20391 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20392 @item ^-s1^/COMPILER_STYLE^
20393 Include the compiler-style section in the report file
20395 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20396 @item ^-s2^/BY_RULES^
20397 Include the section containing diagnoses ordered by rules in the report file
20399 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20400 @item ^-s3^/BY_FILES_BY_RULES^
20401 Include the section containing diagnoses ordered by files and then by rules
20404 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20405 @item ^-v^/VERBOSE^
20406 Verbose mode; @command{gnatcheck} generates version information and then
20407 a trace of sources being processed.
20412 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20413 @option{^-s2^/BY_RULES^} or
20414 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20415 then the @command{gnatcheck} report file will only contain sections
20416 explicitly denoted by these options.
20418 @node gnatcheck Rule Options
20419 @section @command{gnatcheck} Rule Options
20422 The following options control the processing performed by
20423 @command{gnatcheck}.
20426 @cindex @option{+ALL} (@command{gnatcheck})
20428 Turn all the rule checks ON.
20430 @cindex @option{-ALL} (@command{gnatcheck})
20432 Turn all the rule checks OFF.
20434 @cindex @option{+R} (@command{gnatcheck})
20435 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20436 Turn on the check for a specified rule with the specified parameter, if any.
20437 @var{rule_id} must be the identifier of one of the currently implemented rules
20438 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20439 are not case-sensitive. The @var{param} item must
20440 be a string representing a valid parameter(s) for the specified rule.
20441 If it contains any space characters then this string must be enclosed in
20444 @cindex @option{-R} (@command{gnatcheck})
20445 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20446 Turn off the check for a specified rule with the specified parameter, if any.
20448 @cindex @option{-from} (@command{gnatcheck})
20449 @item -from=@var{rule_option_filename}
20450 Read the rule options from the text file @var{rule_option_filename}, referred as
20451 ``rule file'' below.
20456 The default behavior is that all the rule checks are disabled.
20458 A rule file is a text file containing a set of rule options.
20459 @cindex Rule file (for @code{gnatcheck})
20460 The file may contain empty lines and Ada-style comments (comment
20461 lines and end-of-line comments). The rule file has free format; that is,
20462 you do not have to start a new rule option on a new line.
20464 A rule file may contain other @option{-from=@var{rule_option_filename}}
20465 options, each such option being replaced with the content of the
20466 corresponding rule file during the rule files processing. In case a
20467 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20468 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20469 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20470 the processing of rule files is interrupted and a part of their content
20474 @node Adding the Results of Compiler Checks to gnatcheck Output
20475 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20478 The @command{gnatcheck} tool can include in the generated diagnostic messages
20480 the report file the results of the checks performed by the compiler. Though
20481 disabled by default, this effect may be obtained by using @option{+R} with
20482 the following rule identifiers and parameters:
20486 To record restrictions violations (that are performed by the compiler if the
20487 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20489 @code{Restrictions} with the same parameters as pragma
20490 @code{Restrictions} or @code{Restriction_Warnings}.
20493 To record compiler style checks(@pxref{Style Checking}), use the rule named
20494 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20495 which enables all the standard style checks that corresponds to @option{-gnatyy}
20496 GNAT style check option, or a string that has exactly the same
20497 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20498 @code{Style_Checks} (for further information about this pragma,
20499 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}).
20502 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20503 named @code{Warnings} with a parameter that is a valid
20504 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20505 (for further information about this pragma, @pxref{Pragma Warnings,,,
20506 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20507 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20508 all the specific warnings, but not suppresses the warning mode,
20509 and 'e' parameter, corresponding to @option{-gnatwe} that means
20510 "treat warnings as errors", does not have any effect.
20514 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20515 option with the corresponding restriction name as a parameter. @code{-R} is
20516 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20517 warnings and style checks, use the corresponding warning and style options.
20519 @node Project-Wide Checks
20520 @section Project-Wide Checks
20521 @cindex Project-wide checks (for @command{gnatcheck})
20524 In order to perform checks on all units of a given project, you can use
20525 the GNAT driver along with the @option{-P} option:
20527 gnat check -Pproj -rules -from=my_rules
20531 If the project @code{proj} depends upon other projects, you can perform
20532 checks on the project closure using the @option{-U} option:
20534 gnat check -Pproj -U -rules -from=my_rules
20538 Finally, if not all the units are relevant to a particular main
20539 program in the project closure, you can perform checks for the set
20540 of units needed to create a given main program (unit closure) using
20541 the @option{-U} option followed by the name of the main unit:
20543 gnat check -Pproj -U main -rules -from=my_rules
20547 @node Predefined Rules
20548 @section Predefined Rules
20549 @cindex Predefined rules (for @command{gnatcheck})
20552 @c (Jan 2007) Since the global rules are still under development and are not
20553 @c documented, there is no point in explaining the difference between
20554 @c global and local rules
20556 A rule in @command{gnatcheck} is either local or global.
20557 A @emph{local rule} is a rule that applies to a well-defined section
20558 of a program and that can be checked by analyzing only this section.
20559 A @emph{global rule} requires analysis of some global properties of the
20560 whole program (mostly related to the program call graph).
20561 As of @value{NOW}, the implementation of global rules should be
20562 considered to be at a preliminary stage. You can use the
20563 @option{+GLOBAL} option to enable all the global rules, and the
20564 @option{-GLOBAL} rule option to disable all the global rules.
20566 All the global rules in the list below are
20567 so indicated by marking them ``GLOBAL''.
20568 This +GLOBAL and -GLOBAL options are not
20569 included in the list of gnatcheck options above, because at the moment they
20570 are considered as a temporary debug options.
20572 @command{gnatcheck} performs rule checks for generic
20573 instances only for global rules. This limitation may be relaxed in a later
20578 The following subsections document the rules implemented in
20579 @command{gnatcheck}.
20580 The subsection title is the same as the rule identifier, which may be
20581 used as a parameter of the @option{+R} or @option{-R} options.
20585 * Abstract_Type_Declarations::
20586 * Anonymous_Arrays::
20587 * Anonymous_Subtypes::
20589 * Boolean_Relational_Operators::
20591 * Ceiling_Violations::
20593 * Controlled_Type_Declarations::
20594 * Declarations_In_Blocks::
20595 * Default_Parameters::
20596 * Discriminated_Records::
20597 * Enumeration_Ranges_In_CASE_Statements::
20598 * Exceptions_As_Control_Flow::
20599 * EXIT_Statements_With_No_Loop_Name::
20600 * Expanded_Loop_Exit_Names::
20601 * Explicit_Full_Discrete_Ranges::
20602 * Float_Equality_Checks::
20603 * Forbidden_Pragmas::
20604 * Function_Style_Procedures::
20605 * Generics_In_Subprograms::
20606 * GOTO_Statements::
20607 * Implicit_IN_Mode_Parameters::
20608 * Implicit_SMALL_For_Fixed_Point_Types::
20609 * Improperly_Located_Instantiations::
20610 * Improper_Returns::
20611 * Library_Level_Subprograms::
20614 * Improperly_Called_Protected_Entries::
20617 * Misnamed_Identifiers::
20618 * Multiple_Entries_In_Protected_Definitions::
20620 * Non_Qualified_Aggregates::
20621 * Non_Short_Circuit_Operators::
20622 * Non_SPARK_Attributes::
20623 * Non_Tagged_Derived_Types::
20624 * Non_Visible_Exceptions::
20625 * Numeric_Literals::
20626 * OTHERS_In_Aggregates::
20627 * OTHERS_In_CASE_Statements::
20628 * OTHERS_In_Exception_Handlers::
20629 * Outer_Loop_Exits::
20630 * Overloaded_Operators::
20631 * Overly_Nested_Control_Structures::
20632 * Parameters_Out_Of_Order::
20633 * Positional_Actuals_For_Defaulted_Generic_Parameters::
20634 * Positional_Actuals_For_Defaulted_Parameters::
20635 * Positional_Components::
20636 * Positional_Generic_Parameters::
20637 * Positional_Parameters::
20638 * Predefined_Numeric_Types::
20639 * Raising_External_Exceptions::
20640 * Raising_Predefined_Exceptions::
20641 * Separate_Numeric_Error_Handlers::
20644 * Side_Effect_Functions::
20647 * Unassigned_OUT_Parameters::
20648 * Uncommented_BEGIN_In_Package_Bodies::
20649 * Unconstrained_Array_Returns::
20650 * Universal_Ranges::
20651 * Unnamed_Blocks_And_Loops::
20653 * Unused_Subprograms::
20655 * USE_PACKAGE_Clauses::
20656 * Volatile_Objects_Without_Address_Clauses::
20660 @node Abstract_Type_Declarations
20661 @subsection @code{Abstract_Type_Declarations}
20662 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
20665 Flag all declarations of abstract types. For an abstract private
20666 type, both the private and full type declarations are flagged.
20668 This rule has no parameters.
20671 @node Anonymous_Arrays
20672 @subsection @code{Anonymous_Arrays}
20673 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
20676 Flag all anonymous array type definitions (by Ada semantics these can only
20677 occur in object declarations).
20679 This rule has no parameters.
20681 @node Anonymous_Subtypes
20682 @subsection @code{Anonymous_Subtypes}
20683 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
20686 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
20687 any instance of a subtype indication with a constraint, other than one
20688 that occurs immediately within a subtype declaration. Any use of a range
20689 other than as a constraint used immediately within a subtype declaration
20690 is considered as an anonymous subtype.
20692 An effect of this rule is that @code{for} loops such as the following are
20693 flagged (since @code{1..N} is formally a ``range''):
20695 @smallexample @c ada
20696 for I in 1 .. N loop
20702 Declaring an explicit subtype solves the problem:
20704 @smallexample @c ada
20705 subtype S is Integer range 1..N;
20713 This rule has no parameters.
20716 @subsection @code{Blocks}
20717 @cindex @code{Blocks} rule (for @command{gnatcheck})
20720 Flag each block statement.
20722 This rule has no parameters.
20724 @node Boolean_Relational_Operators
20725 @subsection @code{Boolean_Relational_Operators}
20726 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
20729 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
20730 ``>='', ``='' and ``/='') for the predefined Boolean type.
20731 (This rule is useful in enforcing the SPARK language restrictions.)
20733 Calls to predefined relational operators of any type derived from
20734 @code{Standard.Boolean} are not detected. Calls to user-defined functions
20735 with these designators, and uses of operators that are renamings
20736 of the predefined relational operators for @code{Standard.Boolean},
20737 are likewise not detected.
20739 This rule has no parameters.
20742 @node Ceiling_Violations
20743 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
20744 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
20747 Flag invocations of a protected operation by a task whose priority exceeds
20748 the protected object's ceiling.
20750 As of @value{NOW}, this rule has the following limitations:
20755 We consider only pragmas Priority and Interrupt_Priority as means to define
20756 a task/protected operation priority. We do not consider the effect of using
20757 Ada.Dynamic_Priorities.Set_Priority procedure;
20760 We consider only base task priorities, and no priority inheritance. That is,
20761 we do not make a difference between calls issued during task activation and
20762 execution of the sequence of statements from task body;
20765 Any situation when the priority of protected operation caller is set by a
20766 dynamic expression (that is, the corresponding Priority or
20767 Interrupt_Priority pragma has a non-static expression as an argument) we
20768 treat as a priority inconsistency (and, therefore, detect this situation).
20772 At the moment the notion of the main subprogram is not implemented in
20773 gnatcheck, so any pragma Priority in a library level subprogram body (in case
20774 if this subprogram can be a main subprogram of a partition) changes the
20775 priority of an environment task. So if we have more then one such pragma in
20776 the set of processed sources, the pragma that is processed last, defines the
20777 priority of an environment task.
20779 This rule has no parameters.
20782 @node Controlled_Type_Declarations
20783 @subsection @code{Controlled_Type_Declarations}
20784 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
20787 Flag all declarations of controlled types. A declaration of a private type
20788 is flagged if its full declaration declares a controlled type. A declaration
20789 of a derived type is flagged if its ancestor type is controlled. Subtype
20790 declarations are not checked. A declaration of a type that itself is not a
20791 descendant of a type declared in @code{Ada.Finalization} but has a controlled
20792 component is not checked.
20794 This rule has no parameters.
20798 @node Declarations_In_Blocks
20799 @subsection @code{Declarations_In_Blocks}
20800 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
20803 Flag all block statements containing local declarations. A @code{declare}
20804 block with an empty @i{declarative_part} or with a @i{declarative part}
20805 containing only pragmas and/or @code{use} clauses is not flagged.
20807 This rule has no parameters.
20810 @node Default_Parameters
20811 @subsection @code{Default_Parameters}
20812 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
20815 Flag all default expressions for subprogram parameters. Parameter
20816 declarations of formal and generic subprograms are also checked.
20818 This rule has no parameters.
20821 @node Discriminated_Records
20822 @subsection @code{Discriminated_Records}
20823 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
20826 Flag all declarations of record types with discriminants. Only the
20827 declarations of record and record extension types are checked. Incomplete,
20828 formal, private, derived and private extension type declarations are not
20829 checked. Task and protected type declarations also are not checked.
20831 This rule has no parameters.
20834 @node Enumeration_Ranges_In_CASE_Statements
20835 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
20836 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
20839 Flag each use of a range of enumeration literals as a choice in a
20840 @code{case} statement.
20841 All forms for specifying a range (explicit ranges
20842 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
20843 An enumeration range is
20844 flagged even if contains exactly one enumeration value or no values at all. A
20845 type derived from an enumeration type is considered as an enumeration type.
20847 This rule helps prevent maintenance problems arising from adding an
20848 enumeration value to a type and having it implicitly handled by an existing
20849 @code{case} statement with an enumeration range that includes the new literal.
20851 This rule has no parameters.
20854 @node Exceptions_As_Control_Flow
20855 @subsection @code{Exceptions_As_Control_Flow}
20856 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
20859 Flag each place where an exception is explicitly raised and handled in the
20860 same subprogram body. A @code{raise} statement in an exception handler,
20861 package body, task body or entry body is not flagged.
20863 The rule has no parameters.
20865 @node EXIT_Statements_With_No_Loop_Name
20866 @subsection @code{EXIT_Statements_With_No_Loop_Name}
20867 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
20870 Flag each @code{exit} statement that does not specify the name of the loop
20873 The rule has no parameters.
20876 @node Expanded_Loop_Exit_Names
20877 @subsection @code{Expanded_Loop_Exit_Names}
20878 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
20881 Flag all expanded loop names in @code{exit} statements.
20883 This rule has no parameters.
20885 @node Explicit_Full_Discrete_Ranges
20886 @subsection @code{Explicit_Full_Discrete_Ranges}
20887 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
20890 Flag each discrete range that has the form @code{A'First .. A'Last}.
20892 This rule has no parameters.
20894 @node Float_Equality_Checks
20895 @subsection @code{Float_Equality_Checks}
20896 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
20899 Flag all calls to the predefined equality operations for floating-point types.
20900 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
20901 User-defined equality operations are not flagged, nor are ``@code{=}''
20902 and ``@code{/=}'' operations for fixed-point types.
20904 This rule has no parameters.
20907 @node Forbidden_Pragmas
20908 @subsection @code{Forbidden_Pragmas}
20909 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
20912 Flag each use of the specified pragmas. The pragmas to be detected
20913 are named in the rule's parameters.
20915 This rule has the following parameters:
20918 @item For the @option{+R} option
20921 @item @emph{Pragma_Name}
20922 Adds the specified pragma to the set of pragmas to be
20923 checked and sets the checks for all the specified pragmas
20924 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
20925 does not correspond to any pragma name defined in the Ada
20926 standard or to the name of a GNAT-specific pragma defined
20927 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
20928 Manual}, it is treated as the name of unknown pragma.
20931 All the GNAT-specific pragmas are detected; this sets
20932 the checks for all the specified pragmas ON.
20935 All pragmas are detected; this sets the rule ON.
20938 @item For the @option{-R} option
20940 @item @emph{Pragma_Name}
20941 Removes the specified pragma from the set of pragmas to be
20942 checked without affecting checks for
20943 other pragmas. @emph{Pragma_Name} is treated as a name
20944 of a pragma. If it does not correspond to any pragma
20945 defined in the Ada standard or to any name defined in
20946 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
20947 this option is treated as turning OFF detection of all unknown pragmas.
20950 Turn OFF detection of all GNAT-specific pragmas
20953 Clear the list of the pragmas to be detected and
20959 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
20960 the syntax of an Ada identifier and therefore can not be considered
20961 as a pragma name, a diagnostic message is generated and the corresponding
20962 parameter is ignored.
20964 When more then one parameter is given in the same rule option, the parameters
20965 must be separated by a comma.
20967 If more then one option for this rule is specified for the @command{gnatcheck}
20968 call, a new option overrides the previous one(s).
20970 The @option{+R} option with no parameters turns the rule ON with the set of
20971 pragmas to be detected defined by the previous rule options.
20972 (By default this set is empty, so if the only option specified for the rule is
20973 @option{+RForbidden_Pragmas} (with
20974 no parameter), then the rule is enabled, but it does not detect anything).
20975 The @option{-R} option with no parameter turns the rule OFF, but it does not
20976 affect the set of pragmas to be detected.
20981 @node Function_Style_Procedures
20982 @subsection @code{Function_Style_Procedures}
20983 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
20986 Flag each procedure that can be rewritten as a function. A procedure can be
20987 converted into a function if it has exactly one parameter of mode @code{out}
20988 and no parameters of mode @code{in out}. Procedure declarations,
20989 formal procedure declarations, and generic procedure declarations are always
20991 bodies and body stubs are flagged only if they do not have corresponding
20992 separate declarations. Procedure renamings and procedure instantiations are
20995 If a procedure can be rewritten as a function, but its @code{out} parameter is
20996 of a limited type, it is not flagged.
20998 Protected procedures are not flagged. Null procedures also are not flagged.
21000 This rule has no parameters.
21003 @node Generics_In_Subprograms
21004 @subsection @code{Generics_In_Subprograms}
21005 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21008 Flag each declaration of a generic unit in a subprogram. Generic
21009 declarations in the bodies of generic subprograms are also flagged.
21010 A generic unit nested in another generic unit is not flagged.
21011 If a generic unit is
21012 declared in a local package that is declared in a subprogram body, the
21013 generic unit is flagged.
21015 This rule has no parameters.
21018 @node GOTO_Statements
21019 @subsection @code{GOTO_Statements}
21020 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21023 Flag each occurrence of a @code{goto} statement.
21025 This rule has no parameters.
21028 @node Implicit_IN_Mode_Parameters
21029 @subsection @code{Implicit_IN_Mode_Parameters}
21030 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21033 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21034 Note that @code{access} parameters, although they technically behave
21035 like @code{in} parameters, are not flagged.
21037 This rule has no parameters.
21040 @node Implicit_SMALL_For_Fixed_Point_Types
21041 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21042 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21045 Flag each fixed point type declaration that lacks an explicit
21046 representation clause to define its @code{'Small} value.
21047 Since @code{'Small} can be defined only for ordinary fixed point types,
21048 decimal fixed point type declarations are not checked.
21050 This rule has no parameters.
21053 @node Improperly_Located_Instantiations
21054 @subsection @code{Improperly_Located_Instantiations}
21055 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21058 Flag all generic instantiations in library-level package specs
21059 (including library generic packages) and in all subprogram bodies.
21061 Instantiations in task and entry bodies are not flagged. Instantiations in the
21062 bodies of protected subprograms are flagged.
21064 This rule has no parameters.
21068 @node Improper_Returns
21069 @subsection @code{Improper_Returns}
21070 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21073 Flag each explicit @code{return} statement in procedures, and
21074 multiple @code{return} statements in functions.
21075 Diagnostic messages are generated for all @code{return} statements
21076 in a procedure (thus each procedure must be written so that it
21077 returns implicitly at the end of its statement part),
21078 and for all @code{return} statements in a function after the first one.
21079 This rule supports the stylistic convention that each subprogram
21080 should have no more than one point of normal return.
21082 This rule has no parameters.
21085 @node Library_Level_Subprograms
21086 @subsection @code{Library_Level_Subprograms}
21087 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21090 Flag all library-level subprograms (including generic subprogram instantiations).
21092 This rule has no parameters.
21095 @node Local_Packages
21096 @subsection @code{Local_Packages}
21097 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21100 Flag all local packages declared in package and generic package
21102 Local packages in bodies are not flagged.
21104 This rule has no parameters.
21107 @node Improperly_Called_Protected_Entries
21108 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21109 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21112 Flag each protected entry that can be called from more than one task.
21114 This rule has no parameters.
21118 @subsection @code{Metrics}
21119 @cindex @code{Metrics} rule (for @command{gnatcheck})
21122 There is a set of checks based on computing a metric value and comparing the
21123 result with the specified upper (or lower, depending on a specific metric)
21124 value specified for a given metric. A construct is flagged if a given metric
21125 is applicable (can be computed) for it and the computed value is greater
21126 then (lover then) the specified upper (lower) bound.
21128 The name of any metric-based rule consists of the prefix @code{Metrics_}
21129 followed by the name of the corresponding metric (see the table below).
21130 For @option{+R} option, each metric-based rule has a numeric parameter
21131 specifying the bound (integer or real, depending on a metric), @option{-R}
21132 option for metric rules does not have a parameter.
21134 The following table shows the metric names for that the corresponding
21135 metrics-based checks are supported by gnatcheck, including the
21136 constraint that must be satisfied by the bound that is specified for the check
21137 and what bound - upper (U) or lower (L) - should be specified.
21139 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21141 @headitem Check Name @tab Description @tab Bounds Value
21144 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21146 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21147 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21148 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21149 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21153 The meaning and the computed values for all these metrics are exactly
21154 the same as for the corresponding metrics in @command{gnatmetric}.
21156 @emph{Example:} the rule
21158 +RMetrics_Cyclomatic_Complexity : 7
21161 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21163 To turn OFF the check for cyclomatic complexity metric, use the following option:
21165 -RMetrics_Cyclomatic_Complexity
21168 @node Misnamed_Identifiers
21169 @subsection @code{Misnamed_Identifiers}
21170 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21173 Flag the declaration of each identifier that does not have a suffix
21174 corresponding to the kind of entity being declared.
21175 The following declarations are checked:
21182 constant declarations (but not number declarations)
21185 package renaming declarations (but not generic package renaming
21190 This rule may have parameters. When used without parameters, the rule enforces
21191 the following checks:
21195 type-defining names end with @code{_T}, unless the type is an access type,
21196 in which case the suffix must be @code{_A}
21198 constant names end with @code{_C}
21200 names defining package renamings end with @code{_R}
21204 For a private or incomplete type declaration the following checks are
21205 made for the defining name suffix:
21209 For an incomplete type declaration: if the corresponding full type
21210 declaration is available, the defining identifier from the full type
21211 declaration is checked, but the defining identifier from the incomplete type
21212 declaration is not; otherwise the defining identifier from the incomplete
21213 type declaration is checked against the suffix specified for type
21217 For a private type declaration (including private extensions), the defining
21218 identifier from the private type declaration is checked against the type
21219 suffix (even if the corresponding full declaration is an access type
21220 declaration), and the defining identifier from the corresponding full type
21221 declaration is not checked.
21225 For a deferred constant, the defining name in the corresponding full constant
21226 declaration is not checked.
21228 Defining names of formal types are not checked.
21230 The rule may have the following parameters:
21234 For the @option{+R} option:
21237 Sets the default listed above for all the names to be checked.
21239 @item Type_Suffix=@emph{string}
21240 Specifies the suffix for a type name.
21242 @item Access_Suffix=@emph{string}
21243 Specifies the suffix for an access type name. If
21244 this parameter is set, it overrides for access
21245 types the suffix set by the @code{Type_Suffix} parameter.
21247 @item Constant_Suffix=@emph{string}
21248 Specifies the suffix for a constant name.
21250 @item Renaming_Suffix=@emph{string}
21251 Specifies the suffix for a package renaming name.
21255 For the @option{-R} option:
21258 Remove all the suffixes specified for the
21259 identifier suffix checks, whether by default or
21260 as specified by other rule parameters. All the
21261 checks for this rule are disabled as a result.
21264 Removes the suffix specified for types. This
21265 disables checks for types but does not disable
21266 any other checks for this rule (including the
21267 check for access type names if @code{Access_Suffix} is
21270 @item Access_Suffix
21271 Removes the suffix specified for access types.
21272 This disables checks for access type names but
21273 does not disable any other checks for this rule.
21274 If @code{Type_Suffix} is set, access type names are
21275 checked as ordinary type names.
21277 @item Constant_Suffix
21278 Removes the suffix specified for constants. This
21279 disables checks for constant names but does not
21280 disable any other checks for this rule.
21282 @item Renaming_Suffix
21283 Removes the suffix specified for package
21284 renamings. This disables checks for package
21285 renamings but does not disable any other checks
21291 If more than one parameter is used, parameters must be separated by commas.
21293 If more than one option is specified for the @command{gnatcheck} invocation,
21294 a new option overrides the previous one(s).
21296 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21298 name suffixes specified by previous options used for this rule.
21300 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21301 all the checks but keeps
21302 all the suffixes specified by previous options used for this rule.
21304 The @emph{string} value must be a valid suffix for an Ada identifier (after
21305 trimming all the leading and trailing space characters, if any).
21306 Parameters are not case sensitive, except the @emph{string} part.
21308 If any error is detected in a rule parameter, the parameter is ignored.
21309 In such a case the options that are set for the rule are not
21314 @node Multiple_Entries_In_Protected_Definitions
21315 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21316 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21319 Flag each protected definition (i.e., each protected object/type declaration)
21320 that defines more than one entry.
21321 Diagnostic messages are generated for all the entry declarations
21322 except the first one. An entry family is counted as one entry. Entries from
21323 the private part of the protected definition are also checked.
21325 This rule has no parameters.
21328 @subsection @code{Name_Clashes}
21329 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21332 Check that certain names are not used as defining identifiers. To activate
21333 this rule, you need to supply a reference to the dictionary file(s) as a rule
21334 parameter(s) (more then one dictionary file can be specified). If no
21335 dictionary file is set, this rule will not cause anything to be flagged.
21336 Only defining occurrences, not references, are checked.
21337 The check is not case-sensitive.
21339 This rule is enabled by default, but without setting any corresponding
21340 dictionary file(s); thus the default effect is to do no checks.
21342 A dictionary file is a plain text file. The maximum line length for this file
21343 is 1024 characters. If the line is longer then this limit, extra characters
21346 Each line can be either an empty line, a comment line, or a line containing
21347 a list of identifiers separated by space or HT characters.
21348 A comment is an Ada-style comment (from @code{--} to end-of-line).
21349 Identifiers must follow the Ada syntax for identifiers.
21350 A line containing one or more identifiers may end with a comment.
21352 @node Non_Qualified_Aggregates
21353 @subsection @code{Non_Qualified_Aggregates}
21354 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21357 Flag each non-qualified aggregate.
21358 A non-qualified aggregate is an
21359 aggregate that is not the expression of a qualified expression. A
21360 string literal is not considered an aggregate, but an array
21361 aggregate of a string type is considered as a normal aggregate.
21362 Aggregates of anonymous array types are not flagged.
21364 This rule has no parameters.
21367 @node Non_Short_Circuit_Operators
21368 @subsection @code{Non_Short_Circuit_Operators}
21369 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21372 Flag all calls to predefined @code{and} and @code{or} operators for
21373 any boolean type. Calls to
21374 user-defined @code{and} and @code{or} and to operators defined by renaming
21375 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21376 operators for modular types or boolean array types are not flagged.
21378 This rule has no parameters.
21382 @node Non_SPARK_Attributes
21383 @subsection @code{Non_SPARK_Attributes}
21384 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21387 The SPARK language defines the following subset of Ada 95 attribute
21388 designators as those that can be used in SPARK programs. The use of
21389 any other attribute is flagged.
21392 @item @code{'Adjacent}
21395 @item @code{'Ceiling}
21396 @item @code{'Component_Size}
21397 @item @code{'Compose}
21398 @item @code{'Copy_Sign}
21399 @item @code{'Delta}
21400 @item @code{'Denorm}
21401 @item @code{'Digits}
21402 @item @code{'Exponent}
21403 @item @code{'First}
21404 @item @code{'Floor}
21406 @item @code{'Fraction}
21408 @item @code{'Leading_Part}
21409 @item @code{'Length}
21410 @item @code{'Machine}
21411 @item @code{'Machine_Emax}
21412 @item @code{'Machine_Emin}
21413 @item @code{'Machine_Mantissa}
21414 @item @code{'Machine_Overflows}
21415 @item @code{'Machine_Radix}
21416 @item @code{'Machine_Rounds}
21419 @item @code{'Model}
21420 @item @code{'Model_Emin}
21421 @item @code{'Model_Epsilon}
21422 @item @code{'Model_Mantissa}
21423 @item @code{'Model_Small}
21424 @item @code{'Modulus}
21427 @item @code{'Range}
21428 @item @code{'Remainder}
21429 @item @code{'Rounding}
21430 @item @code{'Safe_First}
21431 @item @code{'Safe_Last}
21432 @item @code{'Scaling}
21433 @item @code{'Signed_Zeros}
21435 @item @code{'Small}
21437 @item @code{'Truncation}
21438 @item @code{'Unbiased_Rounding}
21440 @item @code{'Valid}
21444 This rule has no parameters.
21447 @node Non_Tagged_Derived_Types
21448 @subsection @code{Non_Tagged_Derived_Types}
21449 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21452 Flag all derived type declarations that do not have a record extension part.
21454 This rule has no parameters.
21458 @node Non_Visible_Exceptions
21459 @subsection @code{Non_Visible_Exceptions}
21460 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21463 Flag constructs leading to the possibility of propagating an exception
21464 out of the scope in which the exception is declared.
21465 Two cases are detected:
21469 An exception declaration in a subprogram body, task body or block
21470 statement is flagged if the body or statement does not contain a handler for
21471 that exception or a handler with an @code{others} choice.
21474 A @code{raise} statement in an exception handler of a subprogram body,
21475 task body or block statement is flagged if it (re)raises a locally
21476 declared exception. This may occur under the following circumstances:
21479 it explicitly raises a locally declared exception, or
21481 it does not specify an exception name (i.e., it is simply @code{raise;})
21482 and the enclosing handler contains a locally declared exception in its
21488 Renamings of local exceptions are not flagged.
21490 This rule has no parameters.
21493 @node Numeric_Literals
21494 @subsection @code{Numeric_Literals}
21495 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21498 Flag each use of a numeric literal in an index expression, and in any
21499 circumstance except for the following:
21503 a literal occurring in the initialization expression for a constant
21504 declaration or a named number declaration, or
21507 an integer literal that is less than or equal to a value
21508 specified by the @option{N} rule parameter.
21512 This rule may have the following parameters for the @option{+R} option:
21516 @emph{N} is an integer literal used as the maximal value that is not flagged
21517 (i.e., integer literals not exceeding this value are allowed)
21520 All integer literals are flagged
21524 If no parameters are set, the maximum unflagged value is 1.
21526 The last specified check limit (or the fact that there is no limit at
21527 all) is used when multiple @option{+R} options appear.
21529 The @option{-R} option for this rule has no parameters.
21530 It disables the rule but retains the last specified maximum unflagged value.
21531 If the @option{+R} option subsequently appears, this value is used as the
21532 threshold for the check.
21535 @node OTHERS_In_Aggregates
21536 @subsection @code{OTHERS_In_Aggregates}
21537 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21540 Flag each use of an @code{others} choice in extension aggregates.
21541 In record and array aggregates, an @code{others} choice is flagged unless
21542 it is used to refer to all components, or to all but one component.
21544 If, in case of a named array aggregate, there are two associations, one
21545 with an @code{others} choice and another with a discrete range, the
21546 @code{others} choice is flagged even if the discrete range specifies
21547 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21549 This rule has no parameters.
21551 @node OTHERS_In_CASE_Statements
21552 @subsection @code{OTHERS_In_CASE_Statements}
21553 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21556 Flag any use of an @code{others} choice in a @code{case} statement.
21558 This rule has no parameters.
21560 @node OTHERS_In_Exception_Handlers
21561 @subsection @code{OTHERS_In_Exception_Handlers}
21562 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
21565 Flag any use of an @code{others} choice in an exception handler.
21567 This rule has no parameters.
21570 @node Outer_Loop_Exits
21571 @subsection @code{Outer_Loop_Exits}
21572 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
21575 Flag each @code{exit} statement containing a loop name that is not the name
21576 of the immediately enclosing @code{loop} statement.
21578 This rule has no parameters.
21581 @node Overloaded_Operators
21582 @subsection @code{Overloaded_Operators}
21583 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
21586 Flag each function declaration that overloads an operator symbol.
21587 A function body is checked only if the body does not have a
21588 separate spec. Formal functions are also checked. For a
21589 renaming declaration, only renaming-as-declaration is checked
21591 This rule has no parameters.
21594 @node Overly_Nested_Control_Structures
21595 @subsection @code{Overly_Nested_Control_Structures}
21596 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
21599 Flag each control structure whose nesting level exceeds the value provided
21600 in the rule parameter.
21602 The control structures checked are the following:
21605 @item @code{if} statement
21606 @item @code{case} statement
21607 @item @code{loop} statement
21608 @item Selective accept statement
21609 @item Timed entry call statement
21610 @item Conditional entry call
21611 @item Asynchronous select statement
21615 The rule has the following parameter for the @option{+R} option:
21619 Positive integer specifying the maximal control structure nesting
21620 level that is not flagged
21624 If the parameter for the @option{+R} option is not specified or
21625 if it is not a positive integer, @option{+R} option is ignored.
21627 If more then one option is specified for the gnatcheck call, the later option and
21628 new parameter override the previous one(s).
21631 @node Parameters_Out_Of_Order
21632 @subsection @code{Parameters_Out_Of_Order}
21633 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
21636 Flag each subprogram and entry declaration whose formal parameters are not
21637 ordered according to the following scheme:
21641 @item @code{in} and @code{access} parameters first,
21642 then @code{in out} parameters,
21643 and then @code{out} parameters;
21645 @item for @code{in} mode, parameters with default initialization expressions
21650 Only the first violation of the described order is flagged.
21652 The following constructs are checked:
21655 @item subprogram declarations (including null procedures);
21656 @item generic subprogram declarations;
21657 @item formal subprogram declarations;
21658 @item entry declarations;
21659 @item subprogram bodies and subprogram body stubs that do not
21660 have separate specifications
21664 Subprogram renamings are not checked.
21666 This rule has no parameters.
21669 @node Positional_Actuals_For_Defaulted_Generic_Parameters
21670 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
21671 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
21674 Flag each generic actual parameter corresponding to a generic formal
21675 parameter with a default initialization, if positional notation is used.
21677 This rule has no parameters.
21679 @node Positional_Actuals_For_Defaulted_Parameters
21680 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
21681 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
21684 Flag each actual parameter to a subprogram or entry call where the
21685 corresponding formal parameter has a default expression, if positional
21688 This rule has no parameters.
21690 @node Positional_Components
21691 @subsection @code{Positional_Components}
21692 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
21695 Flag each array, record and extension aggregate that includes positional
21698 This rule has no parameters.
21701 @node Positional_Generic_Parameters
21702 @subsection @code{Positional_Generic_Parameters}
21703 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
21706 Flag each instantiation using positional parameter notation.
21708 This rule has no parameters.
21711 @node Positional_Parameters
21712 @subsection @code{Positional_Parameters}
21713 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
21716 Flag each subprogram or entry call using positional parameter notation,
21717 except for the following:
21721 Invocations of prefix or infix operators are not flagged
21723 If the called subprogram or entry has only one formal parameter,
21724 the call is not flagged;
21726 If a subprogram call uses the @emph{Object.Operation} notation, then
21729 the first parameter (that is, @emph{Object}) is not flagged;
21731 if the called subprogram has only two parameters, the second parameter
21732 of the call is not flagged;
21737 This rule has no parameters.
21742 @node Predefined_Numeric_Types
21743 @subsection @code{Predefined_Numeric_Types}
21744 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
21747 Flag each explicit use of the name of any numeric type or subtype defined
21748 in package @code{Standard}.
21750 The rationale for this rule is to detect when the
21751 program may depend on platform-specific characteristics of the implementation
21752 of the predefined numeric types. Note that this rule is over-pessimistic;
21753 for example, a program that uses @code{String} indexing
21754 likely needs a variable of type @code{Integer}.
21755 Another example is the flagging of predefined numeric types with explicit
21758 @smallexample @c ada
21759 subtype My_Integer is Integer range Left .. Right;
21760 Vy_Var : My_Integer;
21764 This rule detects only numeric types and subtypes defined in
21765 @code{Standard}. The use of numeric types and subtypes defined in other
21766 predefined packages (such as @code{System.Any_Priority} or
21767 @code{Ada.Text_IO.Count}) is not flagged
21769 This rule has no parameters.
21773 @node Raising_External_Exceptions
21774 @subsection @code{Raising_External_Exceptions}
21775 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
21778 Flag any @code{raise} statement, in a program unit declared in a library
21779 package or in a generic library package, for an exception that is
21780 neither a predefined exception nor an exception that is also declared (or
21781 renamed) in the visible part of the package.
21783 This rule has no parameters.
21787 @node Raising_Predefined_Exceptions
21788 @subsection @code{Raising_Predefined_Exceptions}
21789 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
21792 Flag each @code{raise} statement that raises a predefined exception
21793 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
21794 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
21796 This rule has no parameters.
21798 @node Separate_Numeric_Error_Handlers
21799 @subsection @code{Separate_Numeric_Error_Handlers}
21800 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
21803 Flags each exception handler that contains a choice for
21804 the predefined @code{Constraint_Error} exception, but does not contain
21805 the choice for the predefined @code{Numeric_Error} exception, or
21806 that contains the choice for @code{Numeric_Error}, but does not contain the
21807 choice for @code{Constraint_Error}.
21809 This rule has no parameters.
21813 @subsection @code{Recursion} (under construction, GLOBAL)
21814 @cindex @code{Recursion} rule (for @command{gnatcheck})
21817 Flag recursive subprograms (cycles in the call graph). Declarations, and not
21818 calls, of recursive subprograms are detected.
21820 This rule has no parameters.
21824 @node Side_Effect_Functions
21825 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
21826 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
21829 Flag functions with side effects.
21831 We define a side effect as changing any data object that is not local for the
21832 body of this function.
21834 At the moment, we do NOT consider a side effect any input-output operations
21835 (changing a state or a content of any file).
21837 We do not consider protected functions for this rule (???)
21839 There are the following sources of side effect:
21842 @item Explicit (or direct) side-effect:
21846 direct assignment to a non-local variable;
21849 direct call to an entity that is known to change some data object that is
21850 not local for the body of this function (Note, that if F1 calls F2 and F2
21851 does have a side effect, this does not automatically mean that F1 also
21852 have a side effect, because it may be the case that F2 is declared in
21853 F1's body and it changes some data object that is global for F2, but
21857 @item Indirect side-effect:
21860 Subprogram calls implicitly issued by:
21863 computing initialization expressions from type declarations as a part
21864 of object elaboration or allocator evaluation;
21866 computing implicit parameters of subprogram or entry calls or generic
21871 activation of a task that change some non-local data object (directly or
21875 elaboration code of a package that is a result of a package instantiation;
21878 controlled objects;
21881 @item Situations when we can suspect a side-effect, but the full static check
21882 is either impossible or too hard:
21885 assignment to access variables or to the objects pointed by access
21889 call to a subprogram pointed by access-to-subprogram value
21897 This rule has no parameters.
21901 @subsection @code{Slices}
21902 @cindex @code{Slices} rule (for @command{gnatcheck})
21905 Flag all uses of array slicing
21907 This rule has no parameters.
21910 @node Unassigned_OUT_Parameters
21911 @subsection @code{Unassigned_OUT_Parameters}
21912 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
21915 Flags procedures' @code{out} parameters that are not assigned, and
21916 identifies the contexts in which the assignments are missing.
21918 An @code{out} parameter is flagged in the statements in the procedure
21919 body's handled sequence of statements (before the procedure body's
21920 @code{exception} part, if any) if this sequence of statements contains
21921 no assignments to the parameter.
21923 An @code{out} parameter is flagged in an exception handler in the exception
21924 part of the procedure body's handled sequence of statements if the handler
21925 contains no assignment to the parameter.
21927 Bodies of generic procedures are also considered.
21929 The following are treated as assignments to an @code{out} parameter:
21933 an assignment statement, with the parameter or some component as the target;
21936 passing the parameter (or one of its components) as an @code{out} or
21937 @code{in out} parameter.
21941 This rule does not have any parameters.
21945 @node Uncommented_BEGIN_In_Package_Bodies
21946 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
21947 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
21950 Flags each package body with declarations and a statement part that does not
21951 include a trailing comment on the line containing the @code{begin} keyword;
21952 this trailing comment needs to specify the package name and nothing else.
21953 The @code{begin} is not flagged if the package body does not
21954 contain any declarations.
21956 If the @code{begin} keyword is placed on the
21957 same line as the last declaration or the first statement, it is flagged
21958 independently of whether the line contains a trailing comment. The
21959 diagnostic message is attached to the line containing the first statement.
21961 This rule has no parameters.
21964 @node Unconstrained_Array_Returns
21965 @subsection @code{Unconstrained_Array_Returns}
21966 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
21969 Flag each function returning an unconstrained array. Function declarations,
21970 function bodies (and body stubs) having no separate specifications,
21971 and generic function instantiations are checked.
21972 Generic function declarations, function calls and function renamings are
21975 This rule has no parameters.
21977 @node Universal_Ranges
21978 @subsection @code{Universal_Ranges}
21979 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
21982 Flag discrete ranges that are a part of an index constraint, constrained
21983 array definition, or @code{for}-loop parameter specification, and whose bounds
21984 are both of type @i{universal_integer}. Ranges that have at least one
21985 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
21986 or an expression of non-universal type) are not flagged.
21988 This rule has no parameters.
21991 @node Unnamed_Blocks_And_Loops
21992 @subsection @code{Unnamed_Blocks_And_Loops}
21993 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
21996 Flag each unnamed block statement and loop statement.
21998 The rule has no parameters.
22003 @node Unused_Subprograms
22004 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22005 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22008 Flag all unused subprograms.
22010 This rule has no parameters.
22016 @node USE_PACKAGE_Clauses
22017 @subsection @code{USE_PACKAGE_Clauses}
22018 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22021 Flag all @code{use} clauses for packages; @code{use type} clauses are
22024 This rule has no parameters.
22028 @node Volatile_Objects_Without_Address_Clauses
22029 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22030 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22033 Flag each volatile object that does not have an address clause.
22035 The following check is made: if the pragma @code{Volatile} is applied to a
22036 data object or to its type, then an address clause must
22037 be supplied for this object.
22039 This rule does not check the components of data objects,
22040 array components that are volatile as a result of the pragma
22041 @code{Volatile_Components}, or objects that are volatile because
22042 they are atomic as a result of pragmas @code{Atomic} or
22043 @code{Atomic_Components}.
22045 Only variable declarations, and not constant declarations, are checked.
22047 This rule has no parameters.
22050 @c *********************************
22051 @node Creating Sample Bodies Using gnatstub
22052 @chapter Creating Sample Bodies Using @command{gnatstub}
22056 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22057 for library unit declarations.
22059 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22060 driver (see @ref{The GNAT Driver and Project Files}).
22062 To create a body stub, @command{gnatstub} has to compile the library
22063 unit declaration. Therefore, bodies can be created only for legal
22064 library units. Moreover, if a library unit depends semantically upon
22065 units located outside the current directory, you have to provide
22066 the source search path when calling @command{gnatstub}, see the description
22067 of @command{gnatstub} switches below.
22069 By default, all the program unit body stubs generated by @code{gnatstub}
22070 raise the predefined @code{Program_Error} exception, which will catch
22071 accidental calls of generated stubs. This behavior can be changed with
22072 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22075 * Running gnatstub::
22076 * Switches for gnatstub::
22079 @node Running gnatstub
22080 @section Running @command{gnatstub}
22083 @command{gnatstub} has the command-line interface of the form
22086 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22093 is the name of the source file that contains a library unit declaration
22094 for which a body must be created. The file name may contain the path
22096 The file name does not have to follow the GNAT file name conventions. If the
22098 does not follow GNAT file naming conventions, the name of the body file must
22100 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22101 If the file name follows the GNAT file naming
22102 conventions and the name of the body file is not provided,
22105 of the body file from the argument file name by replacing the @file{.ads}
22107 with the @file{.adb} suffix.
22110 indicates the directory in which the body stub is to be placed (the default
22115 is an optional sequence of switches as described in the next section
22118 @node Switches for gnatstub
22119 @section Switches for @command{gnatstub}
22125 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22126 If the destination directory already contains a file with the name of the
22128 for the argument spec file, replace it with the generated body stub.
22130 @item ^-hs^/HEADER=SPEC^
22131 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22132 Put the comment header (i.e., all the comments preceding the
22133 compilation unit) from the source of the library unit declaration
22134 into the body stub.
22136 @item ^-hg^/HEADER=GENERAL^
22137 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22138 Put a sample comment header into the body stub.
22140 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22141 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22142 Use the content of the file as the comment header for a generated body stub.
22146 @cindex @option{-IDIR} (@command{gnatstub})
22148 @cindex @option{-I-} (@command{gnatstub})
22151 @item /NOCURRENT_DIRECTORY
22152 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22154 ^These switches have ^This switch has^ the same meaning as in calls to
22156 ^They define ^It defines ^ the source search path in the call to
22157 @command{gcc} issued
22158 by @command{gnatstub} to compile an argument source file.
22160 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22161 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22162 This switch has the same meaning as in calls to @command{gcc}.
22163 It defines the additional configuration file to be passed to the call to
22164 @command{gcc} issued
22165 by @command{gnatstub} to compile an argument source file.
22167 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22168 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22169 (@var{n} is a non-negative integer). Set the maximum line length in the
22170 body stub to @var{n}; the default is 79. The maximum value that can be
22171 specified is 32767. Note that in the special case of configuration
22172 pragma files, the maximum is always 32767 regardless of whether or
22173 not this switch appears.
22175 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22176 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22177 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22178 the generated body sample to @var{n}.
22179 The default indentation is 3.
22181 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22182 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22183 Order local bodies alphabetically. (By default local bodies are ordered
22184 in the same way as the corresponding local specs in the argument spec file.)
22186 @item ^-i^/INDENTATION=^@var{n}
22187 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22188 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22190 @item ^-k^/TREE_FILE=SAVE^
22191 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22192 Do not remove the tree file (i.e., the snapshot of the compiler internal
22193 structures used by @command{gnatstub}) after creating the body stub.
22195 @item ^-l^/LINE_LENGTH=^@var{n}
22196 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22197 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22199 @item ^--no-exception^/NO_EXCEPTION^
22200 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22201 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22202 This is not always possible for function stubs.
22204 @item ^-o ^/BODY=^@var{body-name}
22205 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22206 Body file name. This should be set if the argument file name does not
22208 the GNAT file naming
22209 conventions. If this switch is omitted the default name for the body will be
22211 from the argument file name according to the GNAT file naming conventions.
22214 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22215 Quiet mode: do not generate a confirmation when a body is
22216 successfully created, and do not generate a message when a body is not
22220 @item ^-r^/TREE_FILE=REUSE^
22221 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22222 Reuse the tree file (if it exists) instead of creating it. Instead of
22223 creating the tree file for the library unit declaration, @command{gnatstub}
22224 tries to find it in the current directory and use it for creating
22225 a body. If the tree file is not found, no body is created. This option
22226 also implies @option{^-k^/SAVE^}, whether or not
22227 the latter is set explicitly.
22229 @item ^-t^/TREE_FILE=OVERWRITE^
22230 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22231 Overwrite the existing tree file. If the current directory already
22232 contains the file which, according to the GNAT file naming rules should
22233 be considered as a tree file for the argument source file,
22235 will refuse to create the tree file needed to create a sample body
22236 unless this option is set.
22238 @item ^-v^/VERBOSE^
22239 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22240 Verbose mode: generate version information.
22244 @node Other Utility Programs
22245 @chapter Other Utility Programs
22248 This chapter discusses some other utility programs available in the Ada
22252 * Using Other Utility Programs with GNAT::
22253 * The External Symbol Naming Scheme of GNAT::
22254 * Converting Ada Files to html with gnathtml::
22255 * Installing gnathtml::
22262 @node Using Other Utility Programs with GNAT
22263 @section Using Other Utility Programs with GNAT
22266 The object files generated by GNAT are in standard system format and in
22267 particular the debugging information uses this format. This means
22268 programs generated by GNAT can be used with existing utilities that
22269 depend on these formats.
22272 In general, any utility program that works with C will also often work with
22273 Ada programs generated by GNAT. This includes software utilities such as
22274 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22278 @node The External Symbol Naming Scheme of GNAT
22279 @section The External Symbol Naming Scheme of GNAT
22282 In order to interpret the output from GNAT, when using tools that are
22283 originally intended for use with other languages, it is useful to
22284 understand the conventions used to generate link names from the Ada
22287 All link names are in all lowercase letters. With the exception of library
22288 procedure names, the mechanism used is simply to use the full expanded
22289 Ada name with dots replaced by double underscores. For example, suppose
22290 we have the following package spec:
22292 @smallexample @c ada
22303 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22304 the corresponding link name is @code{qrs__mn}.
22306 Of course if a @code{pragma Export} is used this may be overridden:
22308 @smallexample @c ada
22313 pragma Export (Var1, C, External_Name => "var1_name");
22315 pragma Export (Var2, C, Link_Name => "var2_link_name");
22322 In this case, the link name for @var{Var1} is whatever link name the
22323 C compiler would assign for the C function @var{var1_name}. This typically
22324 would be either @var{var1_name} or @var{_var1_name}, depending on operating
22325 system conventions, but other possibilities exist. The link name for
22326 @var{Var2} is @var{var2_link_name}, and this is not operating system
22330 One exception occurs for library level procedures. A potential ambiguity
22331 arises between the required name @code{_main} for the C main program,
22332 and the name we would otherwise assign to an Ada library level procedure
22333 called @code{Main} (which might well not be the main program).
22335 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
22336 names. So if we have a library level procedure such as
22338 @smallexample @c ada
22341 procedure Hello (S : String);
22347 the external name of this procedure will be @var{_ada_hello}.
22350 @node Converting Ada Files to html with gnathtml
22351 @section Converting Ada Files to HTML with @code{gnathtml}
22354 This @code{Perl} script allows Ada source files to be browsed using
22355 standard Web browsers. For installation procedure, see the section
22356 @xref{Installing gnathtml}.
22358 Ada reserved keywords are highlighted in a bold font and Ada comments in
22359 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
22360 switch to suppress the generation of cross-referencing information, user
22361 defined variables and types will appear in a different color; you will
22362 be able to click on any identifier and go to its declaration.
22364 The command line is as follow:
22366 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
22370 You can pass it as many Ada files as you want. @code{gnathtml} will generate
22371 an html file for every ada file, and a global file called @file{index.htm}.
22372 This file is an index of every identifier defined in the files.
22374 The available ^switches^options^ are the following ones:
22378 @cindex @option{-83} (@code{gnathtml})
22379 Only the Ada 83 subset of keywords will be highlighted.
22381 @item -cc @var{color}
22382 @cindex @option{-cc} (@code{gnathtml})
22383 This option allows you to change the color used for comments. The default
22384 value is green. The color argument can be any name accepted by html.
22387 @cindex @option{-d} (@code{gnathtml})
22388 If the Ada files depend on some other files (for instance through
22389 @code{with} clauses, the latter files will also be converted to html.
22390 Only the files in the user project will be converted to html, not the files
22391 in the run-time library itself.
22394 @cindex @option{-D} (@code{gnathtml})
22395 This command is the same as @option{-d} above, but @command{gnathtml} will
22396 also look for files in the run-time library, and generate html files for them.
22398 @item -ext @var{extension}
22399 @cindex @option{-ext} (@code{gnathtml})
22400 This option allows you to change the extension of the generated HTML files.
22401 If you do not specify an extension, it will default to @file{htm}.
22404 @cindex @option{-f} (@code{gnathtml})
22405 By default, gnathtml will generate html links only for global entities
22406 ('with'ed units, global variables and types,@dots{}). If you specify
22407 @option{-f} on the command line, then links will be generated for local
22410 @item -l @var{number}
22411 @cindex @option{-l} (@code{gnathtml})
22412 If this ^switch^option^ is provided and @var{number} is not 0, then
22413 @code{gnathtml} will number the html files every @var{number} line.
22416 @cindex @option{-I} (@code{gnathtml})
22417 Specify a directory to search for library files (@file{.ALI} files) and
22418 source files. You can provide several -I switches on the command line,
22419 and the directories will be parsed in the order of the command line.
22422 @cindex @option{-o} (@code{gnathtml})
22423 Specify the output directory for html files. By default, gnathtml will
22424 saved the generated html files in a subdirectory named @file{html/}.
22426 @item -p @var{file}
22427 @cindex @option{-p} (@code{gnathtml})
22428 If you are using Emacs and the most recent Emacs Ada mode, which provides
22429 a full Integrated Development Environment for compiling, checking,
22430 running and debugging applications, you may use @file{.gpr} files
22431 to give the directories where Emacs can find sources and object files.
22433 Using this ^switch^option^, you can tell gnathtml to use these files.
22434 This allows you to get an html version of your application, even if it
22435 is spread over multiple directories.
22437 @item -sc @var{color}
22438 @cindex @option{-sc} (@code{gnathtml})
22439 This ^switch^option^ allows you to change the color used for symbol
22441 The default value is red. The color argument can be any name accepted by html.
22443 @item -t @var{file}
22444 @cindex @option{-t} (@code{gnathtml})
22445 This ^switch^option^ provides the name of a file. This file contains a list of
22446 file names to be converted, and the effect is exactly as though they had
22447 appeared explicitly on the command line. This
22448 is the recommended way to work around the command line length limit on some
22453 @node Installing gnathtml
22454 @section Installing @code{gnathtml}
22457 @code{Perl} needs to be installed on your machine to run this script.
22458 @code{Perl} is freely available for almost every architecture and
22459 Operating System via the Internet.
22461 On Unix systems, you may want to modify the first line of the script
22462 @code{gnathtml}, to explicitly tell the Operating system where Perl
22463 is. The syntax of this line is:
22465 #!full_path_name_to_perl
22469 Alternatively, you may run the script using the following command line:
22472 $ perl gnathtml.pl @ovar{switches} @var{files}
22481 The GNAT distribution provides an Ada 95 template for the HP Language
22482 Sensitive Editor (LSE), a component of DECset. In order to
22483 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
22490 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
22491 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
22492 the collection phase with the /DEBUG qualifier.
22495 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
22496 $ DEFINE LIB$DEBUG PCA$COLLECTOR
22497 $ RUN/DEBUG <PROGRAM_NAME>
22503 @c ******************************
22504 @node Code Coverage and Profiling
22505 @chapter Code Coverage and Profiling
22506 @cindex Code Coverage
22510 This chapter describes how to use @code{gcov} - coverage testing tool - and
22511 @code{gprof} - profiler tool - on your Ada programs.
22514 * Code Coverage of Ada Programs using gcov::
22515 * Profiling an Ada Program using gprof::
22518 @node Code Coverage of Ada Programs using gcov
22519 @section Code Coverage of Ada Programs using gcov
22521 @cindex -fprofile-arcs
22522 @cindex -ftest-coverage
22524 @cindex Code Coverage
22527 @code{gcov} is a test coverage program: it analyzes the execution of a given
22528 program on selected tests, to help you determine the portions of the program
22529 that are still untested.
22531 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
22532 User's Guide. You can refer to this documentation for a more complete
22535 This chapter provides a quick startup guide, and
22536 details some Gnat-specific features.
22539 * Quick startup guide::
22543 @node Quick startup guide
22544 @subsection Quick startup guide
22546 In order to perform coverage analysis of a program using @code{gcov}, 3
22551 Code instrumentation during the compilation process
22553 Execution of the instrumented program
22555 Execution of the @code{gcov} tool to generate the result.
22558 The code instrumentation needed by gcov is created at the object level:
22559 The source code is not modified in any way, because the instrumentation code is
22560 inserted by gcc during the compilation process. To compile your code with code
22561 coverage activated, you need to recompile your whole project using the
22563 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
22564 @code{-fprofile-arcs}.
22567 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
22568 -largs -fprofile-arcs
22571 This compilation process will create @file{.gcno} files together with
22572 the usual object files.
22574 Once the program is compiled with coverage instrumentation, you can
22575 run it as many times as needed - on portions of a test suite for
22576 example. The first execution will produce @file{.gcda} files at the
22577 same location as the @file{.gcno} files. The following executions
22578 will update those files, so that a cumulative result of the covered
22579 portions of the program is generated.
22581 Finally, you need to call the @code{gcov} tool. The different options of
22582 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
22584 This will create annotated source files with a @file{.gcov} extension:
22585 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
22587 @node Gnat specifics
22588 @subsection Gnat specifics
22590 Because Ada semantics, portions of the source code may be shared among
22591 several object files. This is the case for example when generics are
22592 involved, when inlining is active or when declarations generate initialisation
22593 calls. In order to take
22594 into account this shared code, you need to call @code{gcov} on all
22595 source files of the tested program at once.
22597 The list of source files might exceed the system's maximum command line
22598 length. In order to bypass this limitation, a new mechanism has been
22599 implemented in @code{gcov}: you can now list all your project's files into a
22600 text file, and provide this file to gcov as a parameter, preceded by a @@
22601 (e.g. @samp{gcov @@mysrclist.txt}).
22603 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
22604 not supported as there can be unresolved symbols during the final link.
22606 @node Profiling an Ada Program using gprof
22607 @section Profiling an Ada Program using gprof
22613 This section is not meant to be an exhaustive documentation of @code{gprof}.
22614 Full documentation for it can be found in the GNU Profiler User's Guide
22615 documentation that is part of this GNAT distribution.
22617 Profiling a program helps determine the parts of a program that are executed
22618 most often, and are therefore the most time-consuming.
22620 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
22621 better handle Ada programs and multitasking.
22622 It is currently supported on the following platforms
22627 solaris sparc/sparc64/x86
22633 In order to profile a program using @code{gprof}, 3 steps are needed:
22637 Code instrumentation, requiring a full recompilation of the project with the
22640 Execution of the program under the analysis conditions, i.e. with the desired
22643 Analysis of the results using the @code{gprof} tool.
22647 The following sections detail the different steps, and indicate how
22648 to interpret the results:
22650 * Compilation for profiling::
22651 * Program execution::
22653 * Interpretation of profiling results::
22656 @node Compilation for profiling
22657 @subsection Compilation for profiling
22661 In order to profile a program the first step is to tell the compiler
22662 to generate the necessary profiling information. The compiler switch to be used
22663 is @code{-pg}, which must be added to other compilation switches. This
22664 switch needs to be specified both during compilation and link stages, and can
22665 be specified once when using gnatmake:
22668 gnatmake -f -pg -P my_project
22672 Note that only the objects that were compiled with the @samp{-pg} switch will be
22673 profiled; if you need to profile your whole project, use the
22674 @samp{-f} gnatmake switch to force full recompilation.
22676 @node Program execution
22677 @subsection Program execution
22680 Once the program has been compiled for profiling, you can run it as usual.
22682 The only constraint imposed by profiling is that the program must terminate
22683 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
22686 Once the program completes execution, a data file called @file{gmon.out} is
22687 generated in the directory where the program was launched from. If this file
22688 already exists, it will be overwritten.
22690 @node Running gprof
22691 @subsection Running gprof
22694 The @code{gprof} tool is called as follow:
22697 gprof my_prog gmon.out
22708 The complete form of the gprof command line is the following:
22711 gprof [^switches^options^] [executable [data-file]]
22715 @code{gprof} supports numerous ^switch^options^. The order of these
22716 ^switch^options^ does not matter. The full list of options can be found in
22717 the GNU Profiler User's Guide documentation that comes with this documentation.
22719 The following is the subset of those switches that is most relevant:
22723 @item --demangle[=@var{style}]
22724 @itemx --no-demangle
22725 @cindex @option{--demangle} (@code{gprof})
22726 These options control whether symbol names should be demangled when
22727 printing output. The default is to demangle C++ symbols. The
22728 @code{--no-demangle} option may be used to turn off demangling. Different
22729 compilers have different mangling styles. The optional demangling style
22730 argument can be used to choose an appropriate demangling style for your
22731 compiler, in particular Ada symbols generated by GNAT can be demangled using
22732 @code{--demangle=gnat}.
22734 @item -e @var{function_name}
22735 @cindex @option{-e} (@code{gprof})
22736 The @samp{-e @var{function}} option tells @code{gprof} not to print
22737 information about the function @var{function_name} (and its
22738 children@dots{}) in the call graph. The function will still be listed
22739 as a child of any functions that call it, but its index number will be
22740 shown as @samp{[not printed]}. More than one @samp{-e} option may be
22741 given; only one @var{function_name} may be indicated with each @samp{-e}
22744 @item -E @var{function_name}
22745 @cindex @option{-E} (@code{gprof})
22746 The @code{-E @var{function}} option works like the @code{-e} option, but
22747 execution time spent in the function (and children who were not called from
22748 anywhere else), will not be used to compute the percentages-of-time for
22749 the call graph. More than one @samp{-E} option may be given; only one
22750 @var{function_name} may be indicated with each @samp{-E} option.
22752 @item -f @var{function_name}
22753 @cindex @option{-f} (@code{gprof})
22754 The @samp{-f @var{function}} option causes @code{gprof} to limit the
22755 call graph to the function @var{function_name} and its children (and
22756 their children@dots{}). More than one @samp{-f} option may be given;
22757 only one @var{function_name} may be indicated with each @samp{-f}
22760 @item -F @var{function_name}
22761 @cindex @option{-F} (@code{gprof})
22762 The @samp{-F @var{function}} option works like the @code{-f} option, but
22763 only time spent in the function and its children (and their
22764 children@dots{}) will be used to determine total-time and
22765 percentages-of-time for the call graph. More than one @samp{-F} option
22766 may be given; only one @var{function_name} may be indicated with each
22767 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
22771 @node Interpretation of profiling results
22772 @subsection Interpretation of profiling results
22776 The results of the profiling analysis are represented by two arrays: the
22777 'flat profile' and the 'call graph'. Full documentation of those outputs
22778 can be found in the GNU Profiler User's Guide.
22780 The flat profile shows the time spent in each function of the program, and how
22781 many time it has been called. This allows you to locate easily the most
22782 time-consuming functions.
22784 The call graph shows, for each subprogram, the subprograms that call it,
22785 and the subprograms that it calls. It also provides an estimate of the time
22786 spent in each of those callers/called subprograms.
22789 @c ******************************
22790 @node Running and Debugging Ada Programs
22791 @chapter Running and Debugging Ada Programs
22795 This chapter discusses how to debug Ada programs.
22797 It applies to GNAT on the Alpha OpenVMS platform;
22798 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
22799 since HP has implemented Ada support in the OpenVMS debugger on I64.
22802 An incorrect Ada program may be handled in three ways by the GNAT compiler:
22806 The illegality may be a violation of the static semantics of Ada. In
22807 that case GNAT diagnoses the constructs in the program that are illegal.
22808 It is then a straightforward matter for the user to modify those parts of
22812 The illegality may be a violation of the dynamic semantics of Ada. In
22813 that case the program compiles and executes, but may generate incorrect
22814 results, or may terminate abnormally with some exception.
22817 When presented with a program that contains convoluted errors, GNAT
22818 itself may terminate abnormally without providing full diagnostics on
22819 the incorrect user program.
22823 * The GNAT Debugger GDB::
22825 * Introduction to GDB Commands::
22826 * Using Ada Expressions::
22827 * Calling User-Defined Subprograms::
22828 * Using the Next Command in a Function::
22831 * Debugging Generic Units::
22832 * GNAT Abnormal Termination or Failure to Terminate::
22833 * Naming Conventions for GNAT Source Files::
22834 * Getting Internal Debugging Information::
22835 * Stack Traceback::
22841 @node The GNAT Debugger GDB
22842 @section The GNAT Debugger GDB
22845 @code{GDB} is a general purpose, platform-independent debugger that
22846 can be used to debug mixed-language programs compiled with @command{gcc},
22847 and in particular is capable of debugging Ada programs compiled with
22848 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
22849 complex Ada data structures.
22851 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
22853 located in the GNU:[DOCS] directory,
22855 for full details on the usage of @code{GDB}, including a section on
22856 its usage on programs. This manual should be consulted for full
22857 details. The section that follows is a brief introduction to the
22858 philosophy and use of @code{GDB}.
22860 When GNAT programs are compiled, the compiler optionally writes debugging
22861 information into the generated object file, including information on
22862 line numbers, and on declared types and variables. This information is
22863 separate from the generated code. It makes the object files considerably
22864 larger, but it does not add to the size of the actual executable that
22865 will be loaded into memory, and has no impact on run-time performance. The
22866 generation of debug information is triggered by the use of the
22867 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
22868 used to carry out the compilations. It is important to emphasize that
22869 the use of these options does not change the generated code.
22871 The debugging information is written in standard system formats that
22872 are used by many tools, including debuggers and profilers. The format
22873 of the information is typically designed to describe C types and
22874 semantics, but GNAT implements a translation scheme which allows full
22875 details about Ada types and variables to be encoded into these
22876 standard C formats. Details of this encoding scheme may be found in
22877 the file exp_dbug.ads in the GNAT source distribution. However, the
22878 details of this encoding are, in general, of no interest to a user,
22879 since @code{GDB} automatically performs the necessary decoding.
22881 When a program is bound and linked, the debugging information is
22882 collected from the object files, and stored in the executable image of
22883 the program. Again, this process significantly increases the size of
22884 the generated executable file, but it does not increase the size of
22885 the executable program itself. Furthermore, if this program is run in
22886 the normal manner, it runs exactly as if the debug information were
22887 not present, and takes no more actual memory.
22889 However, if the program is run under control of @code{GDB}, the
22890 debugger is activated. The image of the program is loaded, at which
22891 point it is ready to run. If a run command is given, then the program
22892 will run exactly as it would have if @code{GDB} were not present. This
22893 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
22894 entirely non-intrusive until a breakpoint is encountered. If no
22895 breakpoint is ever hit, the program will run exactly as it would if no
22896 debugger were present. When a breakpoint is hit, @code{GDB} accesses
22897 the debugging information and can respond to user commands to inspect
22898 variables, and more generally to report on the state of execution.
22902 @section Running GDB
22905 This section describes how to initiate the debugger.
22906 @c The above sentence is really just filler, but it was otherwise
22907 @c clumsy to get the first paragraph nonindented given the conditional
22908 @c nature of the description
22911 The debugger can be launched from a @code{GPS} menu or
22912 directly from the command line. The description below covers the latter use.
22913 All the commands shown can be used in the @code{GPS} debug console window,
22914 but there are usually more GUI-based ways to achieve the same effect.
22917 The command to run @code{GDB} is
22920 $ ^gdb program^GDB PROGRAM^
22924 where @code{^program^PROGRAM^} is the name of the executable file. This
22925 activates the debugger and results in a prompt for debugger commands.
22926 The simplest command is simply @code{run}, which causes the program to run
22927 exactly as if the debugger were not present. The following section
22928 describes some of the additional commands that can be given to @code{GDB}.
22930 @c *******************************
22931 @node Introduction to GDB Commands
22932 @section Introduction to GDB Commands
22935 @code{GDB} contains a large repertoire of commands. @xref{Top,,
22936 Debugging with GDB, gdb, Debugging with GDB},
22938 located in the GNU:[DOCS] directory,
22940 for extensive documentation on the use
22941 of these commands, together with examples of their use. Furthermore,
22942 the command @command{help} invoked from within GDB activates a simple help
22943 facility which summarizes the available commands and their options.
22944 In this section we summarize a few of the most commonly
22945 used commands to give an idea of what @code{GDB} is about. You should create
22946 a simple program with debugging information and experiment with the use of
22947 these @code{GDB} commands on the program as you read through the
22951 @item set args @var{arguments}
22952 The @var{arguments} list above is a list of arguments to be passed to
22953 the program on a subsequent run command, just as though the arguments
22954 had been entered on a normal invocation of the program. The @code{set args}
22955 command is not needed if the program does not require arguments.
22958 The @code{run} command causes execution of the program to start from
22959 the beginning. If the program is already running, that is to say if
22960 you are currently positioned at a breakpoint, then a prompt will ask
22961 for confirmation that you want to abandon the current execution and
22964 @item breakpoint @var{location}
22965 The breakpoint command sets a breakpoint, that is to say a point at which
22966 execution will halt and @code{GDB} will await further
22967 commands. @var{location} is
22968 either a line number within a file, given in the format @code{file:linenumber},
22969 or it is the name of a subprogram. If you request that a breakpoint be set on
22970 a subprogram that is overloaded, a prompt will ask you to specify on which of
22971 those subprograms you want to breakpoint. You can also
22972 specify that all of them should be breakpointed. If the program is run
22973 and execution encounters the breakpoint, then the program
22974 stops and @code{GDB} signals that the breakpoint was encountered by
22975 printing the line of code before which the program is halted.
22977 @item breakpoint exception @var{name}
22978 A special form of the breakpoint command which breakpoints whenever
22979 exception @var{name} is raised.
22980 If @var{name} is omitted,
22981 then a breakpoint will occur when any exception is raised.
22983 @item print @var{expression}
22984 This will print the value of the given expression. Most simple
22985 Ada expression formats are properly handled by @code{GDB}, so the expression
22986 can contain function calls, variables, operators, and attribute references.
22989 Continues execution following a breakpoint, until the next breakpoint or the
22990 termination of the program.
22993 Executes a single line after a breakpoint. If the next statement
22994 is a subprogram call, execution continues into (the first statement of)
22995 the called subprogram.
22998 Executes a single line. If this line is a subprogram call, executes and
22999 returns from the call.
23002 Lists a few lines around the current source location. In practice, it
23003 is usually more convenient to have a separate edit window open with the
23004 relevant source file displayed. Successive applications of this command
23005 print subsequent lines. The command can be given an argument which is a
23006 line number, in which case it displays a few lines around the specified one.
23009 Displays a backtrace of the call chain. This command is typically
23010 used after a breakpoint has occurred, to examine the sequence of calls that
23011 leads to the current breakpoint. The display includes one line for each
23012 activation record (frame) corresponding to an active subprogram.
23015 At a breakpoint, @code{GDB} can display the values of variables local
23016 to the current frame. The command @code{up} can be used to
23017 examine the contents of other active frames, by moving the focus up
23018 the stack, that is to say from callee to caller, one frame at a time.
23021 Moves the focus of @code{GDB} down from the frame currently being
23022 examined to the frame of its callee (the reverse of the previous command),
23024 @item frame @var{n}
23025 Inspect the frame with the given number. The value 0 denotes the frame
23026 of the current breakpoint, that is to say the top of the call stack.
23031 The above list is a very short introduction to the commands that
23032 @code{GDB} provides. Important additional capabilities, including conditional
23033 breakpoints, the ability to execute command sequences on a breakpoint,
23034 the ability to debug at the machine instruction level and many other
23035 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
23036 Debugging with GDB}. Note that most commands can be abbreviated
23037 (for example, c for continue, bt for backtrace).
23039 @node Using Ada Expressions
23040 @section Using Ada Expressions
23041 @cindex Ada expressions
23044 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
23045 extensions. The philosophy behind the design of this subset is
23049 That @code{GDB} should provide basic literals and access to operations for
23050 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
23051 leaving more sophisticated computations to subprograms written into the
23052 program (which therefore may be called from @code{GDB}).
23055 That type safety and strict adherence to Ada language restrictions
23056 are not particularly important to the @code{GDB} user.
23059 That brevity is important to the @code{GDB} user.
23063 Thus, for brevity, the debugger acts as if there were
23064 implicit @code{with} and @code{use} clauses in effect for all user-written
23065 packages, thus making it unnecessary to fully qualify most names with
23066 their packages, regardless of context. Where this causes ambiguity,
23067 @code{GDB} asks the user's intent.
23069 For details on the supported Ada syntax, see @ref{Top,, Debugging with
23070 GDB, gdb, Debugging with GDB}.
23072 @node Calling User-Defined Subprograms
23073 @section Calling User-Defined Subprograms
23076 An important capability of @code{GDB} is the ability to call user-defined
23077 subprograms while debugging. This is achieved simply by entering
23078 a subprogram call statement in the form:
23081 call subprogram-name (parameters)
23085 The keyword @code{call} can be omitted in the normal case where the
23086 @code{subprogram-name} does not coincide with any of the predefined
23087 @code{GDB} commands.
23089 The effect is to invoke the given subprogram, passing it the
23090 list of parameters that is supplied. The parameters can be expressions and
23091 can include variables from the program being debugged. The
23092 subprogram must be defined
23093 at the library level within your program, and @code{GDB} will call the
23094 subprogram within the environment of your program execution (which
23095 means that the subprogram is free to access or even modify variables
23096 within your program).
23098 The most important use of this facility is in allowing the inclusion of
23099 debugging routines that are tailored to particular data structures
23100 in your program. Such debugging routines can be written to provide a suitably
23101 high-level description of an abstract type, rather than a low-level dump
23102 of its physical layout. After all, the standard
23103 @code{GDB print} command only knows the physical layout of your
23104 types, not their abstract meaning. Debugging routines can provide information
23105 at the desired semantic level and are thus enormously useful.
23107 For example, when debugging GNAT itself, it is crucial to have access to
23108 the contents of the tree nodes used to represent the program internally.
23109 But tree nodes are represented simply by an integer value (which in turn
23110 is an index into a table of nodes).
23111 Using the @code{print} command on a tree node would simply print this integer
23112 value, which is not very useful. But the PN routine (defined in file
23113 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23114 a useful high level representation of the tree node, which includes the
23115 syntactic category of the node, its position in the source, the integers
23116 that denote descendant nodes and parent node, as well as varied
23117 semantic information. To study this example in more detail, you might want to
23118 look at the body of the PN procedure in the stated file.
23120 @node Using the Next Command in a Function
23121 @section Using the Next Command in a Function
23124 When you use the @code{next} command in a function, the current source
23125 location will advance to the next statement as usual. A special case
23126 arises in the case of a @code{return} statement.
23128 Part of the code for a return statement is the ``epilog'' of the function.
23129 This is the code that returns to the caller. There is only one copy of
23130 this epilog code, and it is typically associated with the last return
23131 statement in the function if there is more than one return. In some
23132 implementations, this epilog is associated with the first statement
23135 The result is that if you use the @code{next} command from a return
23136 statement that is not the last return statement of the function you
23137 may see a strange apparent jump to the last return statement or to
23138 the start of the function. You should simply ignore this odd jump.
23139 The value returned is always that from the first return statement
23140 that was stepped through.
23142 @node Ada Exceptions
23143 @section Breaking on Ada Exceptions
23147 You can set breakpoints that trip when your program raises
23148 selected exceptions.
23151 @item break exception
23152 Set a breakpoint that trips whenever (any task in the) program raises
23155 @item break exception @var{name}
23156 Set a breakpoint that trips whenever (any task in the) program raises
23157 the exception @var{name}.
23159 @item break exception unhandled
23160 Set a breakpoint that trips whenever (any task in the) program raises an
23161 exception for which there is no handler.
23163 @item info exceptions
23164 @itemx info exceptions @var{regexp}
23165 The @code{info exceptions} command permits the user to examine all defined
23166 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23167 argument, prints out only those exceptions whose name matches @var{regexp}.
23175 @code{GDB} allows the following task-related commands:
23179 This command shows a list of current Ada tasks, as in the following example:
23186 ID TID P-ID Thread Pri State Name
23187 1 8088000 0 807e000 15 Child Activation Wait main_task
23188 2 80a4000 1 80ae000 15 Accept/Select Wait b
23189 3 809a800 1 80a4800 15 Child Activation Wait a
23190 * 4 80ae800 3 80b8000 15 Running c
23194 In this listing, the asterisk before the first task indicates it to be the
23195 currently running task. The first column lists the task ID that is used
23196 to refer to tasks in the following commands.
23198 @item break @var{linespec} task @var{taskid}
23199 @itemx break @var{linespec} task @var{taskid} if @dots{}
23200 @cindex Breakpoints and tasks
23201 These commands are like the @code{break @dots{} thread @dots{}}.
23202 @var{linespec} specifies source lines.
23204 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23205 to specify that you only want @code{GDB} to stop the program when a
23206 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23207 numeric task identifiers assigned by @code{GDB}, shown in the first
23208 column of the @samp{info tasks} display.
23210 If you do not specify @samp{task @var{taskid}} when you set a
23211 breakpoint, the breakpoint applies to @emph{all} tasks of your
23214 You can use the @code{task} qualifier on conditional breakpoints as
23215 well; in this case, place @samp{task @var{taskid}} before the
23216 breakpoint condition (before the @code{if}).
23218 @item task @var{taskno}
23219 @cindex Task switching
23221 This command allows to switch to the task referred by @var{taskno}. In
23222 particular, This allows to browse the backtrace of the specified
23223 task. It is advised to switch back to the original task before
23224 continuing execution otherwise the scheduling of the program may be
23229 For more detailed information on the tasking support,
23230 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23232 @node Debugging Generic Units
23233 @section Debugging Generic Units
23234 @cindex Debugging Generic Units
23238 GNAT always uses code expansion for generic instantiation. This means that
23239 each time an instantiation occurs, a complete copy of the original code is
23240 made, with appropriate substitutions of formals by actuals.
23242 It is not possible to refer to the original generic entities in
23243 @code{GDB}, but it is always possible to debug a particular instance of
23244 a generic, by using the appropriate expanded names. For example, if we have
23246 @smallexample @c ada
23251 generic package k is
23252 procedure kp (v1 : in out integer);
23256 procedure kp (v1 : in out integer) is
23262 package k1 is new k;
23263 package k2 is new k;
23265 var : integer := 1;
23278 Then to break on a call to procedure kp in the k2 instance, simply
23282 (gdb) break g.k2.kp
23286 When the breakpoint occurs, you can step through the code of the
23287 instance in the normal manner and examine the values of local variables, as for
23290 @node GNAT Abnormal Termination or Failure to Terminate
23291 @section GNAT Abnormal Termination or Failure to Terminate
23292 @cindex GNAT Abnormal Termination or Failure to Terminate
23295 When presented with programs that contain serious errors in syntax
23297 GNAT may on rare occasions experience problems in operation, such
23299 segmentation fault or illegal memory access, raising an internal
23300 exception, terminating abnormally, or failing to terminate at all.
23301 In such cases, you can activate
23302 various features of GNAT that can help you pinpoint the construct in your
23303 program that is the likely source of the problem.
23305 The following strategies are presented in increasing order of
23306 difficulty, corresponding to your experience in using GNAT and your
23307 familiarity with compiler internals.
23311 Run @command{gcc} with the @option{-gnatf}. This first
23312 switch causes all errors on a given line to be reported. In its absence,
23313 only the first error on a line is displayed.
23315 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23316 are encountered, rather than after compilation is terminated. If GNAT
23317 terminates prematurely or goes into an infinite loop, the last error
23318 message displayed may help to pinpoint the culprit.
23321 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
23322 mode, @command{gcc} produces ongoing information about the progress of the
23323 compilation and provides the name of each procedure as code is
23324 generated. This switch allows you to find which Ada procedure was being
23325 compiled when it encountered a code generation problem.
23328 @cindex @option{-gnatdc} switch
23329 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
23330 switch that does for the front-end what @option{^-v^VERBOSE^} does
23331 for the back end. The system prints the name of each unit,
23332 either a compilation unit or nested unit, as it is being analyzed.
23334 Finally, you can start
23335 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
23336 front-end of GNAT, and can be run independently (normally it is just
23337 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
23338 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
23339 @code{where} command is the first line of attack; the variable
23340 @code{lineno} (seen by @code{print lineno}), used by the second phase of
23341 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
23342 which the execution stopped, and @code{input_file name} indicates the name of
23346 @node Naming Conventions for GNAT Source Files
23347 @section Naming Conventions for GNAT Source Files
23350 In order to examine the workings of the GNAT system, the following
23351 brief description of its organization may be helpful:
23355 Files with prefix @file{^sc^SC^} contain the lexical scanner.
23358 All files prefixed with @file{^par^PAR^} are components of the parser. The
23359 numbers correspond to chapters of the Ada Reference Manual. For example,
23360 parsing of select statements can be found in @file{par-ch9.adb}.
23363 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
23364 numbers correspond to chapters of the Ada standard. For example, all
23365 issues involving context clauses can be found in @file{sem_ch10.adb}. In
23366 addition, some features of the language require sufficient special processing
23367 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
23368 dynamic dispatching, etc.
23371 All files prefixed with @file{^exp^EXP^} perform normalization and
23372 expansion of the intermediate representation (abstract syntax tree, or AST).
23373 these files use the same numbering scheme as the parser and semantics files.
23374 For example, the construction of record initialization procedures is done in
23375 @file{exp_ch3.adb}.
23378 The files prefixed with @file{^bind^BIND^} implement the binder, which
23379 verifies the consistency of the compilation, determines an order of
23380 elaboration, and generates the bind file.
23383 The files @file{atree.ads} and @file{atree.adb} detail the low-level
23384 data structures used by the front-end.
23387 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
23388 the abstract syntax tree as produced by the parser.
23391 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
23392 all entities, computed during semantic analysis.
23395 Library management issues are dealt with in files with prefix
23401 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
23402 defined in Annex A.
23407 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
23408 defined in Annex B.
23412 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
23413 both language-defined children and GNAT run-time routines.
23417 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
23418 general-purpose packages, fully documented in their specs. All
23419 the other @file{.c} files are modifications of common @command{gcc} files.
23422 @node Getting Internal Debugging Information
23423 @section Getting Internal Debugging Information
23426 Most compilers have internal debugging switches and modes. GNAT
23427 does also, except GNAT internal debugging switches and modes are not
23428 secret. A summary and full description of all the compiler and binder
23429 debug flags are in the file @file{debug.adb}. You must obtain the
23430 sources of the compiler to see the full detailed effects of these flags.
23432 The switches that print the source of the program (reconstructed from
23433 the internal tree) are of general interest for user programs, as are the
23435 the full internal tree, and the entity table (the symbol table
23436 information). The reconstructed source provides a readable version of the
23437 program after the front-end has completed analysis and expansion,
23438 and is useful when studying the performance of specific constructs.
23439 For example, constraint checks are indicated, complex aggregates
23440 are replaced with loops and assignments, and tasking primitives
23441 are replaced with run-time calls.
23443 @node Stack Traceback
23444 @section Stack Traceback
23446 @cindex stack traceback
23447 @cindex stack unwinding
23450 Traceback is a mechanism to display the sequence of subprogram calls that
23451 leads to a specified execution point in a program. Often (but not always)
23452 the execution point is an instruction at which an exception has been raised.
23453 This mechanism is also known as @i{stack unwinding} because it obtains
23454 its information by scanning the run-time stack and recovering the activation
23455 records of all active subprograms. Stack unwinding is one of the most
23456 important tools for program debugging.
23458 The first entry stored in traceback corresponds to the deepest calling level,
23459 that is to say the subprogram currently executing the instruction
23460 from which we want to obtain the traceback.
23462 Note that there is no runtime performance penalty when stack traceback
23463 is enabled, and no exception is raised during program execution.
23466 * Non-Symbolic Traceback::
23467 * Symbolic Traceback::
23470 @node Non-Symbolic Traceback
23471 @subsection Non-Symbolic Traceback
23472 @cindex traceback, non-symbolic
23475 Note: this feature is not supported on all platforms. See
23476 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
23480 * Tracebacks From an Unhandled Exception::
23481 * Tracebacks From Exception Occurrences (non-symbolic)::
23482 * Tracebacks From Anywhere in a Program (non-symbolic)::
23485 @node Tracebacks From an Unhandled Exception
23486 @subsubsection Tracebacks From an Unhandled Exception
23489 A runtime non-symbolic traceback is a list of addresses of call instructions.
23490 To enable this feature you must use the @option{-E}
23491 @code{gnatbind}'s option. With this option a stack traceback is stored as part
23492 of exception information. You can retrieve this information using the
23493 @code{addr2line} tool.
23495 Here is a simple example:
23497 @smallexample @c ada
23503 raise Constraint_Error;
23518 $ gnatmake stb -bargs -E
23521 Execution terminated by unhandled exception
23522 Exception name: CONSTRAINT_ERROR
23524 Call stack traceback locations:
23525 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23529 As we see the traceback lists a sequence of addresses for the unhandled
23530 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
23531 guess that this exception come from procedure P1. To translate these
23532 addresses into the source lines where the calls appear, the
23533 @code{addr2line} tool, described below, is invaluable. The use of this tool
23534 requires the program to be compiled with debug information.
23537 $ gnatmake -g stb -bargs -E
23540 Execution terminated by unhandled exception
23541 Exception name: CONSTRAINT_ERROR
23543 Call stack traceback locations:
23544 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23546 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
23547 0x4011f1 0x77e892a4
23549 00401373 at d:/stb/stb.adb:5
23550 0040138B at d:/stb/stb.adb:10
23551 0040139C at d:/stb/stb.adb:14
23552 00401335 at d:/stb/b~stb.adb:104
23553 004011C4 at /build/@dots{}/crt1.c:200
23554 004011F1 at /build/@dots{}/crt1.c:222
23555 77E892A4 in ?? at ??:0
23559 The @code{addr2line} tool has several other useful options:
23563 to get the function name corresponding to any location
23565 @item --demangle=gnat
23566 to use the gnat decoding mode for the function names. Note that
23567 for binutils version 2.9.x the option is simply @option{--demangle}.
23571 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
23572 0x40139c 0x401335 0x4011c4 0x4011f1
23574 00401373 in stb.p1 at d:/stb/stb.adb:5
23575 0040138B in stb.p2 at d:/stb/stb.adb:10
23576 0040139C in stb at d:/stb/stb.adb:14
23577 00401335 in main at d:/stb/b~stb.adb:104
23578 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
23579 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
23583 From this traceback we can see that the exception was raised in
23584 @file{stb.adb} at line 5, which was reached from a procedure call in
23585 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
23586 which contains the call to the main program.
23587 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
23588 and the output will vary from platform to platform.
23590 It is also possible to use @code{GDB} with these traceback addresses to debug
23591 the program. For example, we can break at a given code location, as reported
23592 in the stack traceback:
23598 Furthermore, this feature is not implemented inside Windows DLL. Only
23599 the non-symbolic traceback is reported in this case.
23602 (gdb) break *0x401373
23603 Breakpoint 1 at 0x401373: file stb.adb, line 5.
23607 It is important to note that the stack traceback addresses
23608 do not change when debug information is included. This is particularly useful
23609 because it makes it possible to release software without debug information (to
23610 minimize object size), get a field report that includes a stack traceback
23611 whenever an internal bug occurs, and then be able to retrieve the sequence
23612 of calls with the same program compiled with debug information.
23614 @node Tracebacks From Exception Occurrences (non-symbolic)
23615 @subsubsection Tracebacks From Exception Occurrences
23618 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
23619 The stack traceback is attached to the exception information string, and can
23620 be retrieved in an exception handler within the Ada program, by means of the
23621 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
23623 @smallexample @c ada
23625 with Ada.Exceptions;
23630 use Ada.Exceptions;
23638 Text_IO.Put_Line (Exception_Information (E));
23652 This program will output:
23657 Exception name: CONSTRAINT_ERROR
23658 Message: stb.adb:12
23659 Call stack traceback locations:
23660 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
23663 @node Tracebacks From Anywhere in a Program (non-symbolic)
23664 @subsubsection Tracebacks From Anywhere in a Program
23667 It is also possible to retrieve a stack traceback from anywhere in a
23668 program. For this you need to
23669 use the @code{GNAT.Traceback} API. This package includes a procedure called
23670 @code{Call_Chain} that computes a complete stack traceback, as well as useful
23671 display procedures described below. It is not necessary to use the
23672 @option{-E gnatbind} option in this case, because the stack traceback mechanism
23673 is invoked explicitly.
23676 In the following example we compute a traceback at a specific location in
23677 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
23678 convert addresses to strings:
23680 @smallexample @c ada
23682 with GNAT.Traceback;
23683 with GNAT.Debug_Utilities;
23689 use GNAT.Traceback;
23692 TB : Tracebacks_Array (1 .. 10);
23693 -- We are asking for a maximum of 10 stack frames.
23695 -- Len will receive the actual number of stack frames returned.
23697 Call_Chain (TB, Len);
23699 Text_IO.Put ("In STB.P1 : ");
23701 for K in 1 .. Len loop
23702 Text_IO.Put (Debug_Utilities.Image (TB (K)));
23723 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
23724 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
23728 You can then get further information by invoking the @code{addr2line}
23729 tool as described earlier (note that the hexadecimal addresses
23730 need to be specified in C format, with a leading ``0x'').
23732 @node Symbolic Traceback
23733 @subsection Symbolic Traceback
23734 @cindex traceback, symbolic
23737 A symbolic traceback is a stack traceback in which procedure names are
23738 associated with each code location.
23741 Note that this feature is not supported on all platforms. See
23742 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
23743 list of currently supported platforms.
23746 Note that the symbolic traceback requires that the program be compiled
23747 with debug information. If it is not compiled with debug information
23748 only the non-symbolic information will be valid.
23751 * Tracebacks From Exception Occurrences (symbolic)::
23752 * Tracebacks From Anywhere in a Program (symbolic)::
23755 @node Tracebacks From Exception Occurrences (symbolic)
23756 @subsubsection Tracebacks From Exception Occurrences
23758 @smallexample @c ada
23760 with GNAT.Traceback.Symbolic;
23766 raise Constraint_Error;
23783 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
23788 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
23791 0040149F in stb.p1 at stb.adb:8
23792 004014B7 in stb.p2 at stb.adb:13
23793 004014CF in stb.p3 at stb.adb:18
23794 004015DD in ada.stb at stb.adb:22
23795 00401461 in main at b~stb.adb:168
23796 004011C4 in __mingw_CRTStartup at crt1.c:200
23797 004011F1 in mainCRTStartup at crt1.c:222
23798 77E892A4 in ?? at ??:0
23802 In the above example the ``.\'' syntax in the @command{gnatmake} command
23803 is currently required by @command{addr2line} for files that are in
23804 the current working directory.
23805 Moreover, the exact sequence of linker options may vary from platform
23807 The above @option{-largs} section is for Windows platforms. By contrast,
23808 under Unix there is no need for the @option{-largs} section.
23809 Differences across platforms are due to details of linker implementation.
23811 @node Tracebacks From Anywhere in a Program (symbolic)
23812 @subsubsection Tracebacks From Anywhere in a Program
23815 It is possible to get a symbolic stack traceback
23816 from anywhere in a program, just as for non-symbolic tracebacks.
23817 The first step is to obtain a non-symbolic
23818 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
23819 information. Here is an example:
23821 @smallexample @c ada
23823 with GNAT.Traceback;
23824 with GNAT.Traceback.Symbolic;
23829 use GNAT.Traceback;
23830 use GNAT.Traceback.Symbolic;
23833 TB : Tracebacks_Array (1 .. 10);
23834 -- We are asking for a maximum of 10 stack frames.
23836 -- Len will receive the actual number of stack frames returned.
23838 Call_Chain (TB, Len);
23839 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
23852 @c ******************************
23854 @node Compatibility with HP Ada
23855 @chapter Compatibility with HP Ada
23856 @cindex Compatibility
23861 @cindex Compatibility between GNAT and HP Ada
23862 This chapter compares HP Ada (formerly known as ``DEC Ada'')
23863 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
23864 GNAT is highly compatible
23865 with HP Ada, and it should generally be straightforward to port code
23866 from the HP Ada environment to GNAT. However, there are a few language
23867 and implementation differences of which the user must be aware. These
23868 differences are discussed in this chapter. In
23869 addition, the operating environment and command structure for the
23870 compiler are different, and these differences are also discussed.
23872 For further details on these and other compatibility issues,
23873 see Appendix E of the HP publication
23874 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
23876 Except where otherwise indicated, the description of GNAT for OpenVMS
23877 applies to both the Alpha and I64 platforms.
23879 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
23880 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
23882 The discussion in this chapter addresses specifically the implementation
23883 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
23884 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
23885 GNAT always follows the Alpha implementation.
23887 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
23888 attributes are recognized, although only a subset of them can sensibly
23889 be implemented. The description of pragmas in
23890 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
23891 indicates whether or not they are applicable to non-VMS systems.
23894 * Ada Language Compatibility::
23895 * Differences in the Definition of Package System::
23896 * Language-Related Features::
23897 * The Package STANDARD::
23898 * The Package SYSTEM::
23899 * Tasking and Task-Related Features::
23900 * Pragmas and Pragma-Related Features::
23901 * Library of Predefined Units::
23903 * Main Program Definition::
23904 * Implementation-Defined Attributes::
23905 * Compiler and Run-Time Interfacing::
23906 * Program Compilation and Library Management::
23908 * Implementation Limits::
23909 * Tools and Utilities::
23912 @node Ada Language Compatibility
23913 @section Ada Language Compatibility
23916 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
23917 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
23918 with Ada 83, and therefore Ada 83 programs will compile
23919 and run under GNAT with
23920 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
23921 provides details on specific incompatibilities.
23923 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
23924 as well as the pragma @code{ADA_83}, to force the compiler to
23925 operate in Ada 83 mode. This mode does not guarantee complete
23926 conformance to Ada 83, but in practice is sufficient to
23927 eliminate most sources of incompatibilities.
23928 In particular, it eliminates the recognition of the
23929 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
23930 in Ada 83 programs is legal, and handles the cases of packages
23931 with optional bodies, and generics that instantiate unconstrained
23932 types without the use of @code{(<>)}.
23934 @node Differences in the Definition of Package System
23935 @section Differences in the Definition of Package @code{System}
23938 An Ada compiler is allowed to add
23939 implementation-dependent declarations to package @code{System}.
23941 GNAT does not take advantage of this permission, and the version of
23942 @code{System} provided by GNAT exactly matches that defined in the Ada
23945 However, HP Ada adds an extensive set of declarations to package
23947 as fully documented in the HP Ada manuals. To minimize changes required
23948 for programs that make use of these extensions, GNAT provides the pragma
23949 @code{Extend_System} for extending the definition of package System. By using:
23950 @cindex pragma @code{Extend_System}
23951 @cindex @code{Extend_System} pragma
23953 @smallexample @c ada
23956 pragma Extend_System (Aux_DEC);
23962 the set of definitions in @code{System} is extended to include those in
23963 package @code{System.Aux_DEC}.
23964 @cindex @code{System.Aux_DEC} package
23965 @cindex @code{Aux_DEC} package (child of @code{System})
23966 These definitions are incorporated directly into package @code{System},
23967 as though they had been declared there. For a
23968 list of the declarations added, see the spec of this package,
23969 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
23970 @cindex @file{s-auxdec.ads} file
23971 The pragma @code{Extend_System} is a configuration pragma, which means that
23972 it can be placed in the file @file{gnat.adc}, so that it will automatically
23973 apply to all subsequent compilations. See @ref{Configuration Pragmas},
23974 for further details.
23976 An alternative approach that avoids the use of the non-standard
23977 @code{Extend_System} pragma is to add a context clause to the unit that
23978 references these facilities:
23980 @smallexample @c ada
23982 with System.Aux_DEC;
23983 use System.Aux_DEC;
23988 The effect is not quite semantically identical to incorporating
23989 the declarations directly into package @code{System},
23990 but most programs will not notice a difference
23991 unless they use prefix notation (e.g.@: @code{System.Integer_8})
23992 to reference the entities directly in package @code{System}.
23993 For units containing such references,
23994 the prefixes must either be removed, or the pragma @code{Extend_System}
23997 @node Language-Related Features
23998 @section Language-Related Features
24001 The following sections highlight differences in types,
24002 representations of types, operations, alignment, and
24006 * Integer Types and Representations::
24007 * Floating-Point Types and Representations::
24008 * Pragmas Float_Representation and Long_Float::
24009 * Fixed-Point Types and Representations::
24010 * Record and Array Component Alignment::
24011 * Address Clauses::
24012 * Other Representation Clauses::
24015 @node Integer Types and Representations
24016 @subsection Integer Types and Representations
24019 The set of predefined integer types is identical in HP Ada and GNAT.
24020 Furthermore the representation of these integer types is also identical,
24021 including the capability of size clauses forcing biased representation.
24024 HP Ada for OpenVMS Alpha systems has defined the
24025 following additional integer types in package @code{System}:
24042 @code{LARGEST_INTEGER}
24046 In GNAT, the first four of these types may be obtained from the
24047 standard Ada package @code{Interfaces}.
24048 Alternatively, by use of the pragma @code{Extend_System}, identical
24049 declarations can be referenced directly in package @code{System}.
24050 On both GNAT and HP Ada, the maximum integer size is 64 bits.
24052 @node Floating-Point Types and Representations
24053 @subsection Floating-Point Types and Representations
24054 @cindex Floating-Point types
24057 The set of predefined floating-point types is identical in HP Ada and GNAT.
24058 Furthermore the representation of these floating-point
24059 types is also identical. One important difference is that the default
24060 representation for HP Ada is @code{VAX_Float}, but the default representation
24063 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
24064 pragma @code{Float_Representation} as described in the HP Ada
24066 For example, the declarations:
24068 @smallexample @c ada
24070 type F_Float is digits 6;
24071 pragma Float_Representation (VAX_Float, F_Float);
24076 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
24078 This set of declarations actually appears in @code{System.Aux_DEC},
24080 the full set of additional floating-point declarations provided in
24081 the HP Ada version of package @code{System}.
24082 This and similar declarations may be accessed in a user program
24083 by using pragma @code{Extend_System}. The use of this
24084 pragma, and the related pragma @code{Long_Float} is described in further
24085 detail in the following section.
24087 @node Pragmas Float_Representation and Long_Float
24088 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24091 HP Ada provides the pragma @code{Float_Representation}, which
24092 acts as a program library switch to allow control over
24093 the internal representation chosen for the predefined
24094 floating-point types declared in the package @code{Standard}.
24095 The format of this pragma is as follows:
24097 @smallexample @c ada
24099 pragma Float_Representation(VAX_Float | IEEE_Float);
24104 This pragma controls the representation of floating-point
24109 @code{VAX_Float} specifies that floating-point
24110 types are represented by default with the VAX system hardware types
24111 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24112 Note that the @code{H-floating}
24113 type was available only on VAX systems, and is not available
24114 in either HP Ada or GNAT.
24117 @code{IEEE_Float} specifies that floating-point
24118 types are represented by default with the IEEE single and
24119 double floating-point types.
24123 GNAT provides an identical implementation of the pragma
24124 @code{Float_Representation}, except that it functions as a
24125 configuration pragma. Note that the
24126 notion of configuration pragma corresponds closely to the
24127 HP Ada notion of a program library switch.
24129 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24131 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24132 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24133 advisable to change the format of numbers passed to standard library
24134 routines, and if necessary explicit type conversions may be needed.
24136 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24137 efficient, and (given that it conforms to an international standard)
24138 potentially more portable.
24139 The situation in which @code{VAX_Float} may be useful is in interfacing
24140 to existing code and data that expect the use of @code{VAX_Float}.
24141 In such a situation use the predefined @code{VAX_Float}
24142 types in package @code{System}, as extended by
24143 @code{Extend_System}. For example, use @code{System.F_Float}
24144 to specify the 32-bit @code{F-Float} format.
24147 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24148 to allow control over the internal representation chosen
24149 for the predefined type @code{Long_Float} and for floating-point
24150 type declarations with digits specified in the range 7 .. 15.
24151 The format of this pragma is as follows:
24153 @smallexample @c ada
24155 pragma Long_Float (D_FLOAT | G_FLOAT);
24159 @node Fixed-Point Types and Representations
24160 @subsection Fixed-Point Types and Representations
24163 On HP Ada for OpenVMS Alpha systems, rounding is
24164 away from zero for both positive and negative numbers.
24165 Therefore, @code{+0.5} rounds to @code{1},
24166 and @code{-0.5} rounds to @code{-1}.
24168 On GNAT the results of operations
24169 on fixed-point types are in accordance with the Ada
24170 rules. In particular, results of operations on decimal
24171 fixed-point types are truncated.
24173 @node Record and Array Component Alignment
24174 @subsection Record and Array Component Alignment
24177 On HP Ada for OpenVMS Alpha, all non-composite components
24178 are aligned on natural boundaries. For example, 1-byte
24179 components are aligned on byte boundaries, 2-byte
24180 components on 2-byte boundaries, 4-byte components on 4-byte
24181 byte boundaries, and so on. The OpenVMS Alpha hardware
24182 runs more efficiently with naturally aligned data.
24184 On GNAT, alignment rules are compatible
24185 with HP Ada for OpenVMS Alpha.
24187 @node Address Clauses
24188 @subsection Address Clauses
24191 In HP Ada and GNAT, address clauses are supported for
24192 objects and imported subprograms.
24193 The predefined type @code{System.Address} is a private type
24194 in both compilers on Alpha OpenVMS, with the same representation
24195 (it is simply a machine pointer). Addition, subtraction, and comparison
24196 operations are available in the standard Ada package
24197 @code{System.Storage_Elements}, or in package @code{System}
24198 if it is extended to include @code{System.Aux_DEC} using a
24199 pragma @code{Extend_System} as previously described.
24201 Note that code that @code{with}'s both this extended package @code{System}
24202 and the package @code{System.Storage_Elements} should not @code{use}
24203 both packages, or ambiguities will result. In general it is better
24204 not to mix these two sets of facilities. The Ada package was
24205 designed specifically to provide the kind of features that HP Ada
24206 adds directly to package @code{System}.
24208 The type @code{System.Address} is a 64-bit integer type in GNAT for
24209 I64 OpenVMS. For more information,
24210 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24212 GNAT is compatible with HP Ada in its handling of address
24213 clauses, except for some limitations in
24214 the form of address clauses for composite objects with
24215 initialization. Such address clauses are easily replaced
24216 by the use of an explicitly-defined constant as described
24217 in the Ada Reference Manual (13.1(22)). For example, the sequence
24220 @smallexample @c ada
24222 X, Y : Integer := Init_Func;
24223 Q : String (X .. Y) := "abc";
24225 for Q'Address use Compute_Address;
24230 will be rejected by GNAT, since the address cannot be computed at the time
24231 that @code{Q} is declared. To achieve the intended effect, write instead:
24233 @smallexample @c ada
24236 X, Y : Integer := Init_Func;
24237 Q_Address : constant Address := Compute_Address;
24238 Q : String (X .. Y) := "abc";
24240 for Q'Address use Q_Address;
24246 which will be accepted by GNAT (and other Ada compilers), and is also
24247 compatible with Ada 83. A fuller description of the restrictions
24248 on address specifications is found in @ref{Top, GNAT Reference Manual,
24249 About This Guide, gnat_rm, GNAT Reference Manual}.
24251 @node Other Representation Clauses
24252 @subsection Other Representation Clauses
24255 GNAT implements in a compatible manner all the representation
24256 clauses supported by HP Ada. In addition, GNAT
24257 implements the representation clause forms that were introduced in Ada 95,
24258 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24260 @node The Package STANDARD
24261 @section The Package @code{STANDARD}
24264 The package @code{STANDARD}, as implemented by HP Ada, is fully
24265 described in the @cite{Ada Reference Manual} and in the
24266 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24267 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24269 In addition, HP Ada supports the Latin-1 character set in
24270 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24271 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24272 the type @code{WIDE_CHARACTER}.
24274 The floating-point types supported by GNAT are those
24275 supported by HP Ada, but the defaults are different, and are controlled by
24276 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24278 @node The Package SYSTEM
24279 @section The Package @code{SYSTEM}
24282 HP Ada provides a specific version of the package
24283 @code{SYSTEM} for each platform on which the language is implemented.
24284 For the complete spec of the package @code{SYSTEM}, see
24285 Appendix F of the @cite{HP Ada Language Reference Manual}.
24287 On HP Ada, the package @code{SYSTEM} includes the following conversion
24290 @item @code{TO_ADDRESS(INTEGER)}
24292 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24294 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24296 @item @code{TO_INTEGER(ADDRESS)}
24298 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24300 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24301 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24305 By default, GNAT supplies a version of @code{SYSTEM} that matches
24306 the definition given in the @cite{Ada Reference Manual}.
24308 is a subset of the HP system definitions, which is as
24309 close as possible to the original definitions. The only difference
24310 is that the definition of @code{SYSTEM_NAME} is different:
24312 @smallexample @c ada
24314 type Name is (SYSTEM_NAME_GNAT);
24315 System_Name : constant Name := SYSTEM_NAME_GNAT;
24320 Also, GNAT adds the Ada declarations for
24321 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
24323 However, the use of the following pragma causes GNAT
24324 to extend the definition of package @code{SYSTEM} so that it
24325 encompasses the full set of HP-specific extensions,
24326 including the functions listed above:
24328 @smallexample @c ada
24330 pragma Extend_System (Aux_DEC);
24335 The pragma @code{Extend_System} is a configuration pragma that
24336 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
24337 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
24339 HP Ada does not allow the recompilation of the package
24340 @code{SYSTEM}. Instead HP Ada provides several pragmas
24341 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
24342 to modify values in the package @code{SYSTEM}.
24343 On OpenVMS Alpha systems, the pragma
24344 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
24345 its single argument.
24347 GNAT does permit the recompilation of package @code{SYSTEM} using
24348 the special switch @option{-gnatg}, and this switch can be used if
24349 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
24350 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
24351 or @code{MEMORY_SIZE} by any other means.
24353 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
24354 enumeration literal @code{SYSTEM_NAME_GNAT}.
24356 The definitions provided by the use of
24358 @smallexample @c ada
24359 pragma Extend_System (AUX_Dec);
24363 are virtually identical to those provided by the HP Ada 83 package
24364 @code{SYSTEM}. One important difference is that the name of the
24366 function for type @code{UNSIGNED_LONGWORD} is changed to
24367 @code{TO_ADDRESS_LONG}.
24368 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
24369 discussion of why this change was necessary.
24372 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
24374 an extension to Ada 83 not strictly compatible with the reference manual.
24375 GNAT, in order to be exactly compatible with the standard,
24376 does not provide this capability. In HP Ada 83, the
24377 point of this definition is to deal with a call like:
24379 @smallexample @c ada
24380 TO_ADDRESS (16#12777#);
24384 Normally, according to Ada 83 semantics, one would expect this to be
24385 ambiguous, since it matches both the @code{INTEGER} and
24386 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
24387 However, in HP Ada 83, there is no ambiguity, since the
24388 definition using @i{universal_integer} takes precedence.
24390 In GNAT, since the version with @i{universal_integer} cannot be supplied,
24392 not possible to be 100% compatible. Since there are many programs using
24393 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
24395 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
24396 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
24398 @smallexample @c ada
24399 function To_Address (X : Integer) return Address;
24400 pragma Pure_Function (To_Address);
24402 function To_Address_Long (X : Unsigned_Longword) return Address;
24403 pragma Pure_Function (To_Address_Long);
24407 This means that programs using @code{TO_ADDRESS} for
24408 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
24410 @node Tasking and Task-Related Features
24411 @section Tasking and Task-Related Features
24414 This section compares the treatment of tasking in GNAT
24415 and in HP Ada for OpenVMS Alpha.
24416 The GNAT description applies to both Alpha and I64 OpenVMS.
24417 For detailed information on tasking in
24418 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
24419 relevant run-time reference manual.
24422 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
24423 * Assigning Task IDs::
24424 * Task IDs and Delays::
24425 * Task-Related Pragmas::
24426 * Scheduling and Task Priority::
24428 * External Interrupts::
24431 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24432 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24435 On OpenVMS Alpha systems, each Ada task (except a passive
24436 task) is implemented as a single stream of execution
24437 that is created and managed by the kernel. On these
24438 systems, HP Ada tasking support is based on DECthreads,
24439 an implementation of the POSIX standard for threads.
24441 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
24442 code that calls DECthreads routines can be used together.
24443 The interaction between Ada tasks and DECthreads routines
24444 can have some benefits. For example when on OpenVMS Alpha,
24445 HP Ada can call C code that is already threaded.
24447 GNAT uses the facilities of DECthreads,
24448 and Ada tasks are mapped to threads.
24450 @node Assigning Task IDs
24451 @subsection Assigning Task IDs
24454 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
24455 the environment task that executes the main program. On
24456 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
24457 that have been created but are not yet activated.
24459 On OpenVMS Alpha systems, task IDs are assigned at
24460 activation. On GNAT systems, task IDs are also assigned at
24461 task creation but do not have the same form or values as
24462 task ID values in HP Ada. There is no null task, and the
24463 environment task does not have a specific task ID value.
24465 @node Task IDs and Delays
24466 @subsection Task IDs and Delays
24469 On OpenVMS Alpha systems, tasking delays are implemented
24470 using Timer System Services. The Task ID is used for the
24471 identification of the timer request (the @code{REQIDT} parameter).
24472 If Timers are used in the application take care not to use
24473 @code{0} for the identification, because cancelling such a timer
24474 will cancel all timers and may lead to unpredictable results.
24476 @node Task-Related Pragmas
24477 @subsection Task-Related Pragmas
24480 Ada supplies the pragma @code{TASK_STORAGE}, which allows
24481 specification of the size of the guard area for a task
24482 stack. (The guard area forms an area of memory that has no
24483 read or write access and thus helps in the detection of
24484 stack overflow.) On OpenVMS Alpha systems, if the pragma
24485 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
24486 area is created. In the absence of a pragma @code{TASK_STORAGE},
24487 a default guard area is created.
24489 GNAT supplies the following task-related pragmas:
24492 @item @code{TASK_INFO}
24494 This pragma appears within a task definition and
24495 applies to the task in which it appears. The argument
24496 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
24498 @item @code{TASK_STORAGE}
24500 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
24501 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
24502 @code{SUPPRESS}, and @code{VOLATILE}.
24504 @node Scheduling and Task Priority
24505 @subsection Scheduling and Task Priority
24508 HP Ada implements the Ada language requirement that
24509 when two tasks are eligible for execution and they have
24510 different priorities, the lower priority task does not
24511 execute while the higher priority task is waiting. The HP
24512 Ada Run-Time Library keeps a task running until either the
24513 task is suspended or a higher priority task becomes ready.
24515 On OpenVMS Alpha systems, the default strategy is round-
24516 robin with preemption. Tasks of equal priority take turns
24517 at the processor. A task is run for a certain period of
24518 time and then placed at the tail of the ready queue for
24519 its priority level.
24521 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
24522 which can be used to enable or disable round-robin
24523 scheduling of tasks with the same priority.
24524 See the relevant HP Ada run-time reference manual for
24525 information on using the pragmas to control HP Ada task
24528 GNAT follows the scheduling rules of Annex D (Real-Time
24529 Annex) of the @cite{Ada Reference Manual}. In general, this
24530 scheduling strategy is fully compatible with HP Ada
24531 although it provides some additional constraints (as
24532 fully documented in Annex D).
24533 GNAT implements time slicing control in a manner compatible with
24534 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
24535 are identical to the HP Ada 83 pragma of the same name.
24536 Note that it is not possible to mix GNAT tasking and
24537 HP Ada 83 tasking in the same program, since the two run-time
24538 libraries are not compatible.
24540 @node The Task Stack
24541 @subsection The Task Stack
24544 In HP Ada, a task stack is allocated each time a
24545 non-passive task is activated. As soon as the task is
24546 terminated, the storage for the task stack is deallocated.
24547 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
24548 a default stack size is used. Also, regardless of the size
24549 specified, some additional space is allocated for task
24550 management purposes. On OpenVMS Alpha systems, at least
24551 one page is allocated.
24553 GNAT handles task stacks in a similar manner. In accordance with
24554 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
24555 an alternative method for controlling the task stack size.
24556 The specification of the attribute @code{T'STORAGE_SIZE} is also
24557 supported in a manner compatible with HP Ada.
24559 @node External Interrupts
24560 @subsection External Interrupts
24563 On HP Ada, external interrupts can be associated with task entries.
24564 GNAT is compatible with HP Ada in its handling of external interrupts.
24566 @node Pragmas and Pragma-Related Features
24567 @section Pragmas and Pragma-Related Features
24570 Both HP Ada and GNAT supply all language-defined pragmas
24571 as specified by the Ada 83 standard. GNAT also supplies all
24572 language-defined pragmas introduced by Ada 95 and Ada 2005.
24573 In addition, GNAT implements the implementation-defined pragmas
24577 @item @code{AST_ENTRY}
24579 @item @code{COMMON_OBJECT}
24581 @item @code{COMPONENT_ALIGNMENT}
24583 @item @code{EXPORT_EXCEPTION}
24585 @item @code{EXPORT_FUNCTION}
24587 @item @code{EXPORT_OBJECT}
24589 @item @code{EXPORT_PROCEDURE}
24591 @item @code{EXPORT_VALUED_PROCEDURE}
24593 @item @code{FLOAT_REPRESENTATION}
24597 @item @code{IMPORT_EXCEPTION}
24599 @item @code{IMPORT_FUNCTION}
24601 @item @code{IMPORT_OBJECT}
24603 @item @code{IMPORT_PROCEDURE}
24605 @item @code{IMPORT_VALUED_PROCEDURE}
24607 @item @code{INLINE_GENERIC}
24609 @item @code{INTERFACE_NAME}
24611 @item @code{LONG_FLOAT}
24613 @item @code{MAIN_STORAGE}
24615 @item @code{PASSIVE}
24617 @item @code{PSECT_OBJECT}
24619 @item @code{SHARE_GENERIC}
24621 @item @code{SUPPRESS_ALL}
24623 @item @code{TASK_STORAGE}
24625 @item @code{TIME_SLICE}
24631 These pragmas are all fully implemented, with the exception of @code{TITLE},
24632 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
24633 recognized, but which have no
24634 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
24635 use of Ada protected objects. In GNAT, all generics are inlined.
24637 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
24638 a separate subprogram specification which must appear before the
24641 GNAT also supplies a number of implementation-defined pragmas as follows:
24643 @item @code{ABORT_DEFER}
24645 @item @code{ADA_83}
24647 @item @code{ADA_95}
24649 @item @code{ADA_05}
24651 @item @code{ANNOTATE}
24653 @item @code{ASSERT}
24655 @item @code{C_PASS_BY_COPY}
24657 @item @code{CPP_CLASS}
24659 @item @code{CPP_CONSTRUCTOR}
24661 @item @code{CPP_DESTRUCTOR}
24665 @item @code{EXTEND_SYSTEM}
24667 @item @code{LINKER_ALIAS}
24669 @item @code{LINKER_SECTION}
24671 @item @code{MACHINE_ATTRIBUTE}
24673 @item @code{NO_RETURN}
24675 @item @code{PURE_FUNCTION}
24677 @item @code{SOURCE_FILE_NAME}
24679 @item @code{SOURCE_REFERENCE}
24681 @item @code{TASK_INFO}
24683 @item @code{UNCHECKED_UNION}
24685 @item @code{UNIMPLEMENTED_UNIT}
24687 @item @code{UNIVERSAL_DATA}
24689 @item @code{UNSUPPRESS}
24691 @item @code{WARNINGS}
24693 @item @code{WEAK_EXTERNAL}
24697 For full details on these GNAT implementation-defined pragmas,
24698 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
24702 * Restrictions on the Pragma INLINE::
24703 * Restrictions on the Pragma INTERFACE::
24704 * Restrictions on the Pragma SYSTEM_NAME::
24707 @node Restrictions on the Pragma INLINE
24708 @subsection Restrictions on Pragma @code{INLINE}
24711 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
24713 @item Parameters cannot have a task type.
24715 @item Function results cannot be task types, unconstrained
24716 array types, or unconstrained types with discriminants.
24718 @item Bodies cannot declare the following:
24720 @item Subprogram body or stub (imported subprogram is allowed)
24724 @item Generic declarations
24726 @item Instantiations
24730 @item Access types (types derived from access types allowed)
24732 @item Array or record types
24734 @item Dependent tasks
24736 @item Direct recursive calls of subprogram or containing
24737 subprogram, directly or via a renaming
24743 In GNAT, the only restriction on pragma @code{INLINE} is that the
24744 body must occur before the call if both are in the same
24745 unit, and the size must be appropriately small. There are
24746 no other specific restrictions which cause subprograms to
24747 be incapable of being inlined.
24749 @node Restrictions on the Pragma INTERFACE
24750 @subsection Restrictions on Pragma @code{INTERFACE}
24753 The following restrictions on pragma @code{INTERFACE}
24754 are enforced by both HP Ada and GNAT:
24756 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
24757 Default is the default on OpenVMS Alpha systems.
24759 @item Parameter passing: Language specifies default
24760 mechanisms but can be overridden with an @code{EXPORT} pragma.
24763 @item Ada: Use internal Ada rules.
24765 @item Bliss, C: Parameters must be mode @code{in}; cannot be
24766 record or task type. Result cannot be a string, an
24767 array, or a record.
24769 @item Fortran: Parameters cannot have a task type. Result cannot
24770 be a string, an array, or a record.
24775 GNAT is entirely upwards compatible with HP Ada, and in addition allows
24776 record parameters for all languages.
24778 @node Restrictions on the Pragma SYSTEM_NAME
24779 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
24782 For HP Ada for OpenVMS Alpha, the enumeration literal
24783 for the type @code{NAME} is @code{OPENVMS_AXP}.
24784 In GNAT, the enumeration
24785 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
24787 @node Library of Predefined Units
24788 @section Library of Predefined Units
24791 A library of predefined units is provided as part of the
24792 HP Ada and GNAT implementations. HP Ada does not provide
24793 the package @code{MACHINE_CODE} but instead recommends importing
24796 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
24797 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
24799 The HP Ada Predefined Library units are modified to remove post-Ada 83
24800 incompatibilities and to make them interoperable with GNAT
24801 (@pxref{Changes to DECLIB}, for details).
24802 The units are located in the @file{DECLIB} directory.
24804 The GNAT RTL is contained in
24805 the @file{ADALIB} directory, and
24806 the default search path is set up to find @code{DECLIB} units in preference
24807 to @code{ADALIB} units with the same name (@code{TEXT_IO},
24808 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
24811 * Changes to DECLIB::
24814 @node Changes to DECLIB
24815 @subsection Changes to @code{DECLIB}
24818 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
24819 compatibility are minor and include the following:
24822 @item Adjusting the location of pragmas and record representation
24823 clauses to obey Ada 95 (and thus Ada 2005) rules
24825 @item Adding the proper notation to generic formal parameters
24826 that take unconstrained types in instantiation
24828 @item Adding pragma @code{ELABORATE_BODY} to package specs
24829 that have package bodies not otherwise allowed
24831 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
24832 ``@code{PROTECTD}''.
24833 Currently these are found only in the @code{STARLET} package spec.
24835 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
24836 where the address size is constrained to 32 bits.
24840 None of the above changes is visible to users.
24846 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
24849 @item Command Language Interpreter (CLI interface)
24851 @item DECtalk Run-Time Library (DTK interface)
24853 @item Librarian utility routines (LBR interface)
24855 @item General Purpose Run-Time Library (LIB interface)
24857 @item Math Run-Time Library (MTH interface)
24859 @item National Character Set Run-Time Library (NCS interface)
24861 @item Compiled Code Support Run-Time Library (OTS interface)
24863 @item Parallel Processing Run-Time Library (PPL interface)
24865 @item Screen Management Run-Time Library (SMG interface)
24867 @item Sort Run-Time Library (SOR interface)
24869 @item String Run-Time Library (STR interface)
24871 @item STARLET System Library
24874 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
24876 @item X Windows Toolkit (XT interface)
24878 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
24882 GNAT provides implementations of these HP bindings in the @code{DECLIB}
24883 directory, on both the Alpha and I64 OpenVMS platforms.
24885 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
24887 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
24888 A pragma @code{Linker_Options} has been added to packages @code{Xm},
24889 @code{Xt}, and @code{X_Lib}
24890 causing the default X/Motif sharable image libraries to be linked in. This
24891 is done via options files named @file{xm.opt}, @file{xt.opt}, and
24892 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
24894 It may be necessary to edit these options files to update or correct the
24895 library names if, for example, the newer X/Motif bindings from
24896 @file{ADA$EXAMPLES}
24897 had been (previous to installing GNAT) copied and renamed to supersede the
24898 default @file{ADA$PREDEFINED} versions.
24901 * Shared Libraries and Options Files::
24902 * Interfaces to C::
24905 @node Shared Libraries and Options Files
24906 @subsection Shared Libraries and Options Files
24909 When using the HP Ada
24910 predefined X and Motif bindings, the linking with their sharable images is
24911 done automatically by @command{GNAT LINK}.
24912 When using other X and Motif bindings, you need
24913 to add the corresponding sharable images to the command line for
24914 @code{GNAT LINK}. When linking with shared libraries, or with
24915 @file{.OPT} files, you must
24916 also add them to the command line for @command{GNAT LINK}.
24918 A shared library to be used with GNAT is built in the same way as other
24919 libraries under VMS. The VMS Link command can be used in standard fashion.
24921 @node Interfaces to C
24922 @subsection Interfaces to C
24926 provides the following Ada types and operations:
24929 @item C types package (@code{C_TYPES})
24931 @item C strings (@code{C_TYPES.NULL_TERMINATED})
24933 @item Other_types (@code{SHORT_INT})
24937 Interfacing to C with GNAT, you can use the above approach
24938 described for HP Ada or the facilities of Annex B of
24939 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
24940 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
24941 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
24943 The @option{-gnatF} qualifier forces default and explicit
24944 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
24945 to be uppercased for compatibility with the default behavior
24946 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
24948 @node Main Program Definition
24949 @section Main Program Definition
24952 The following section discusses differences in the
24953 definition of main programs on HP Ada and GNAT.
24954 On HP Ada, main programs are defined to meet the
24955 following conditions:
24957 @item Procedure with no formal parameters (returns @code{0} upon
24960 @item Procedure with no formal parameters (returns @code{42} when
24961 an unhandled exception is raised)
24963 @item Function with no formal parameters whose returned value
24964 is of a discrete type
24966 @item Procedure with one @code{out} formal of a discrete type for
24967 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
24972 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
24973 a main function or main procedure returns a discrete
24974 value whose size is less than 64 bits (32 on VAX systems),
24975 the value is zero- or sign-extended as appropriate.
24976 On GNAT, main programs are defined as follows:
24978 @item Must be a non-generic, parameterless subprogram that
24979 is either a procedure or function returning an Ada
24980 @code{STANDARD.INTEGER} (the predefined type)
24982 @item Cannot be a generic subprogram or an instantiation of a
24986 @node Implementation-Defined Attributes
24987 @section Implementation-Defined Attributes
24990 GNAT provides all HP Ada implementation-defined
24993 @node Compiler and Run-Time Interfacing
24994 @section Compiler and Run-Time Interfacing
24997 HP Ada provides the following qualifiers to pass options to the linker
25000 @item @option{/WAIT} and @option{/SUBMIT}
25002 @item @option{/COMMAND}
25004 @item @option{/@r{[}NO@r{]}MAP}
25006 @item @option{/OUTPUT=@var{file-spec}}
25008 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25012 To pass options to the linker, GNAT provides the following
25016 @item @option{/EXECUTABLE=@var{exec-name}}
25018 @item @option{/VERBOSE}
25020 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25024 For more information on these switches, see
25025 @ref{Switches for gnatlink}.
25026 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
25027 to control optimization. HP Ada also supplies the
25030 @item @code{OPTIMIZE}
25032 @item @code{INLINE}
25034 @item @code{INLINE_GENERIC}
25036 @item @code{SUPPRESS_ALL}
25038 @item @code{PASSIVE}
25042 In GNAT, optimization is controlled strictly by command
25043 line parameters, as described in the corresponding section of this guide.
25044 The HP pragmas for control of optimization are
25045 recognized but ignored.
25047 Note that in GNAT, the default is optimization off, whereas in HP Ada
25048 the default is that optimization is turned on.
25050 @node Program Compilation and Library Management
25051 @section Program Compilation and Library Management
25054 HP Ada and GNAT provide a comparable set of commands to
25055 build programs. HP Ada also provides a program library,
25056 which is a concept that does not exist on GNAT. Instead,
25057 GNAT provides directories of sources that are compiled as
25060 The following table summarizes
25061 the HP Ada commands and provides
25062 equivalent GNAT commands. In this table, some GNAT
25063 equivalents reflect the fact that GNAT does not use the
25064 concept of a program library. Instead, it uses a model
25065 in which collections of source and object files are used
25066 in a manner consistent with other languages like C and
25067 Fortran. Therefore, standard system file commands are used
25068 to manipulate these elements. Those GNAT commands are marked with
25070 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
25073 @multitable @columnfractions .35 .65
25075 @item @emph{HP Ada Command}
25076 @tab @emph{GNAT Equivalent / Description}
25078 @item @command{ADA}
25079 @tab @command{GNAT COMPILE}@*
25080 Invokes the compiler to compile one or more Ada source files.
25082 @item @command{ACS ATTACH}@*
25083 @tab [No equivalent]@*
25084 Switches control of terminal from current process running the program
25087 @item @command{ACS CHECK}
25088 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25089 Forms the execution closure of one
25090 or more compiled units and checks completeness and currency.
25092 @item @command{ACS COMPILE}
25093 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25094 Forms the execution closure of one or
25095 more specified units, checks completeness and currency,
25096 identifies units that have revised source files, compiles same,
25097 and recompiles units that are or will become obsolete.
25098 Also completes incomplete generic instantiations.
25100 @item @command{ACS COPY FOREIGN}
25102 Copies a foreign object file into the program library as a
25105 @item @command{ACS COPY UNIT}
25107 Copies a compiled unit from one program library to another.
25109 @item @command{ACS CREATE LIBRARY}
25110 @tab Create /directory (*)@*
25111 Creates a program library.
25113 @item @command{ACS CREATE SUBLIBRARY}
25114 @tab Create /directory (*)@*
25115 Creates a program sublibrary.
25117 @item @command{ACS DELETE LIBRARY}
25119 Deletes a program library and its contents.
25121 @item @command{ACS DELETE SUBLIBRARY}
25123 Deletes a program sublibrary and its contents.
25125 @item @command{ACS DELETE UNIT}
25126 @tab Delete file (*)@*
25127 On OpenVMS systems, deletes one or more compiled units from
25128 the current program library.
25130 @item @command{ACS DIRECTORY}
25131 @tab Directory (*)@*
25132 On OpenVMS systems, lists units contained in the current
25135 @item @command{ACS ENTER FOREIGN}
25137 Allows the import of a foreign body as an Ada library
25138 spec and enters a reference to a pointer.
25140 @item @command{ACS ENTER UNIT}
25142 Enters a reference (pointer) from the current program library to
25143 a unit compiled into another program library.
25145 @item @command{ACS EXIT}
25146 @tab [No equivalent]@*
25147 Exits from the program library manager.
25149 @item @command{ACS EXPORT}
25151 Creates an object file that contains system-specific object code
25152 for one or more units. With GNAT, object files can simply be copied
25153 into the desired directory.
25155 @item @command{ACS EXTRACT SOURCE}
25157 Allows access to the copied source file for each Ada compilation unit
25159 @item @command{ACS HELP}
25160 @tab @command{HELP GNAT}@*
25161 Provides online help.
25163 @item @command{ACS LINK}
25164 @tab @command{GNAT LINK}@*
25165 Links an object file containing Ada units into an executable file.
25167 @item @command{ACS LOAD}
25169 Loads (partially compiles) Ada units into the program library.
25170 Allows loading a program from a collection of files into a library
25171 without knowing the relationship among units.
25173 @item @command{ACS MERGE}
25175 Merges into the current program library, one or more units from
25176 another library where they were modified.
25178 @item @command{ACS RECOMPILE}
25179 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25180 Recompiles from external or copied source files any obsolete
25181 unit in the closure. Also, completes any incomplete generic
25184 @item @command{ACS REENTER}
25185 @tab @command{GNAT MAKE}@*
25186 Reenters current references to units compiled after last entered
25187 with the @command{ACS ENTER UNIT} command.
25189 @item @command{ACS SET LIBRARY}
25190 @tab Set default (*)@*
25191 Defines a program library to be the compilation context as well
25192 as the target library for compiler output and commands in general.
25194 @item @command{ACS SET PRAGMA}
25195 @tab Edit @file{gnat.adc} (*)@*
25196 Redefines specified values of the library characteristics
25197 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25198 and @code{Float_Representation}.
25200 @item @command{ACS SET SOURCE}
25201 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25202 Defines the source file search list for the @command{ACS COMPILE} command.
25204 @item @command{ACS SHOW LIBRARY}
25205 @tab Directory (*)@*
25206 Lists information about one or more program libraries.
25208 @item @command{ACS SHOW PROGRAM}
25209 @tab [No equivalent]@*
25210 Lists information about the execution closure of one or
25211 more units in the program library.
25213 @item @command{ACS SHOW SOURCE}
25214 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25215 Shows the source file search used when compiling units.
25217 @item @command{ACS SHOW VERSION}
25218 @tab Compile with @option{VERBOSE} option
25219 Displays the version number of the compiler and program library
25222 @item @command{ACS SPAWN}
25223 @tab [No equivalent]@*
25224 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25227 @item @command{ACS VERIFY}
25228 @tab [No equivalent]@*
25229 Performs a series of consistency checks on a program library to
25230 determine whether the library structure and library files are in
25237 @section Input-Output
25240 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25241 Management Services (RMS) to perform operations on
25245 HP Ada and GNAT predefine an identical set of input-
25246 output packages. To make the use of the
25247 generic @code{TEXT_IO} operations more convenient, HP Ada
25248 provides predefined library packages that instantiate the
25249 integer and floating-point operations for the predefined
25250 integer and floating-point types as shown in the following table.
25252 @multitable @columnfractions .45 .55
25253 @item @emph{Package Name} @tab Instantiation
25255 @item @code{INTEGER_TEXT_IO}
25256 @tab @code{INTEGER_IO(INTEGER)}
25258 @item @code{SHORT_INTEGER_TEXT_IO}
25259 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25261 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25262 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25264 @item @code{FLOAT_TEXT_IO}
25265 @tab @code{FLOAT_IO(FLOAT)}
25267 @item @code{LONG_FLOAT_TEXT_IO}
25268 @tab @code{FLOAT_IO(LONG_FLOAT)}
25272 The HP Ada predefined packages and their operations
25273 are implemented using OpenVMS Alpha files and input-output
25274 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25275 Familiarity with the following is recommended:
25277 @item RMS file organizations and access methods
25279 @item OpenVMS file specifications and directories
25281 @item OpenVMS File Definition Language (FDL)
25285 GNAT provides I/O facilities that are completely
25286 compatible with HP Ada. The distribution includes the
25287 standard HP Ada versions of all I/O packages, operating
25288 in a manner compatible with HP Ada. In particular, the
25289 following packages are by default the HP Ada (Ada 83)
25290 versions of these packages rather than the renamings
25291 suggested in Annex J of the Ada Reference Manual:
25293 @item @code{TEXT_IO}
25295 @item @code{SEQUENTIAL_IO}
25297 @item @code{DIRECT_IO}
25301 The use of the standard child package syntax (for
25302 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25304 GNAT provides HP-compatible predefined instantiations
25305 of the @code{TEXT_IO} packages, and also
25306 provides the standard predefined instantiations required
25307 by the @cite{Ada Reference Manual}.
25309 For further information on how GNAT interfaces to the file
25310 system or how I/O is implemented in programs written in
25311 mixed languages, see @ref{Implementation of the Standard I/O,,,
25312 gnat_rm, GNAT Reference Manual}.
25313 This chapter covers the following:
25315 @item Standard I/O packages
25317 @item @code{FORM} strings
25319 @item @code{ADA.DIRECT_IO}
25321 @item @code{ADA.SEQUENTIAL_IO}
25323 @item @code{ADA.TEXT_IO}
25325 @item Stream pointer positioning
25327 @item Reading and writing non-regular files
25329 @item @code{GET_IMMEDIATE}
25331 @item Treating @code{TEXT_IO} files as streams
25338 @node Implementation Limits
25339 @section Implementation Limits
25342 The following table lists implementation limits for HP Ada
25344 @multitable @columnfractions .60 .20 .20
25346 @item @emph{Compilation Parameter}
25351 @item In a subprogram or entry declaration, maximum number of
25352 formal parameters that are of an unconstrained record type
25357 @item Maximum identifier length (number of characters)
25362 @item Maximum number of characters in a source line
25367 @item Maximum collection size (number of bytes)
25372 @item Maximum number of discriminants for a record type
25377 @item Maximum number of formal parameters in an entry or
25378 subprogram declaration
25383 @item Maximum number of dimensions in an array type
25388 @item Maximum number of library units and subunits in a compilation.
25393 @item Maximum number of library units and subunits in an execution.
25398 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
25399 or @code{PSECT_OBJECT}
25404 @item Maximum number of enumeration literals in an enumeration type
25410 @item Maximum number of lines in a source file
25415 @item Maximum number of bits in any object
25420 @item Maximum size of the static portion of a stack frame (approximate)
25425 @node Tools and Utilities
25426 @section Tools and Utilities
25429 The following table lists some of the OpenVMS development tools
25430 available for HP Ada, and the corresponding tools for
25431 use with @value{EDITION} on Alpha and I64 platforms.
25432 Aside from the debugger, all the OpenVMS tools identified are part
25433 of the DECset package.
25436 @c Specify table in TeX since Texinfo does a poor job
25440 \settabs\+Language-Sensitive Editor\quad
25441 &Product with HP Ada\quad
25444 &\it Product with HP Ada
25445 & \it Product with GNAT Pro\cr
25447 \+Code Management System
25451 \+Language-Sensitive Editor
25453 & emacs or HP LSE (Alpha)\cr
25463 & OpenVMS Debug (I64)\cr
25465 \+Source Code Analyzer /
25482 \+Coverage Analyzer
25486 \+Module Management
25488 & Not applicable\cr
25498 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
25499 @c the TeX version above for the printed version
25501 @c @multitable @columnfractions .3 .4 .4
25502 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
25504 @tab @i{Tool with HP Ada}
25505 @tab @i{Tool with @value{EDITION}}
25506 @item Code Management@*System
25509 @item Language-Sensitive@*Editor
25511 @tab emacs or HP LSE (Alpha)
25520 @tab OpenVMS Debug (I64)
25521 @item Source Code Analyzer /@*Cross Referencer
25525 @tab HP Digital Test@*Manager (DTM)
25527 @item Performance and@*Coverage Analyzer
25530 @item Module Management@*System
25532 @tab Not applicable
25539 @c **************************************
25540 @node Platform-Specific Information for the Run-Time Libraries
25541 @appendix Platform-Specific Information for the Run-Time Libraries
25542 @cindex Tasking and threads libraries
25543 @cindex Threads libraries and tasking
25544 @cindex Run-time libraries (platform-specific information)
25547 The GNAT run-time implementation may vary with respect to both the
25548 underlying threads library and the exception handling scheme.
25549 For threads support, one or more of the following are supplied:
25551 @item @b{native threads library}, a binding to the thread package from
25552 the underlying operating system
25554 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
25555 POSIX thread package
25559 For exception handling, either or both of two models are supplied:
25561 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
25562 Most programs should experience a substantial speed improvement by
25563 being compiled with a ZCX run-time.
25564 This is especially true for
25565 tasking applications or applications with many exception handlers.}
25566 @cindex Zero-Cost Exceptions
25567 @cindex ZCX (Zero-Cost Exceptions)
25568 which uses binder-generated tables that
25569 are interrogated at run time to locate a handler
25571 @item @b{setjmp / longjmp} (``SJLJ''),
25572 @cindex setjmp/longjmp Exception Model
25573 @cindex SJLJ (setjmp/longjmp Exception Model)
25574 which uses dynamically-set data to establish
25575 the set of handlers
25579 This appendix summarizes which combinations of threads and exception support
25580 are supplied on various GNAT platforms.
25581 It then shows how to select a particular library either
25582 permanently or temporarily,
25583 explains the properties of (and tradeoffs among) the various threads
25584 libraries, and provides some additional
25585 information about several specific platforms.
25588 * Summary of Run-Time Configurations::
25589 * Specifying a Run-Time Library::
25590 * Choosing the Scheduling Policy::
25591 * Solaris-Specific Considerations::
25592 * Linux-Specific Considerations::
25593 * AIX-Specific Considerations::
25594 * Irix-Specific Considerations::
25595 * RTX-Specific Considerations::
25598 @node Summary of Run-Time Configurations
25599 @section Summary of Run-Time Configurations
25601 @multitable @columnfractions .30 .70
25602 @item @b{alpha-openvms}
25603 @item @code{@ @ }@i{rts-native (default)}
25604 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25605 @item @code{@ @ @ @ }Exceptions @tab ZCX
25607 @item @b{alpha-tru64}
25608 @item @code{@ @ }@i{rts-native (default)}
25609 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25610 @item @code{@ @ @ @ }Exceptions @tab ZCX
25612 @item @code{@ @ }@i{rts-sjlj}
25613 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25614 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25616 @item @b{ia64-hp_linux}
25617 @item @code{@ @ }@i{rts-native (default)}
25618 @item @code{@ @ @ @ }Tasking @tab pthread library
25619 @item @code{@ @ @ @ }Exceptions @tab ZCX
25621 @item @b{ia64-hpux}
25622 @item @code{@ @ }@i{rts-native (default)}
25623 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25624 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25626 @item @b{ia64-openvms}
25627 @item @code{@ @ }@i{rts-native (default)}
25628 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25629 @item @code{@ @ @ @ }Exceptions @tab ZCX
25631 @item @b{ia64-sgi_linux}
25632 @item @code{@ @ }@i{rts-native (default)}
25633 @item @code{@ @ @ @ }Tasking @tab pthread library
25634 @item @code{@ @ @ @ }Exceptions @tab ZCX
25636 @item @b{mips-irix}
25637 @item @code{@ @ }@i{rts-native (default)}
25638 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
25639 @item @code{@ @ @ @ }Exceptions @tab ZCX
25642 @item @code{@ @ }@i{rts-native (default)}
25643 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25644 @item @code{@ @ @ @ }Exceptions @tab ZCX
25646 @item @code{@ @ }@i{rts-sjlj}
25647 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25648 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25651 @item @code{@ @ }@i{rts-native (default)}
25652 @item @code{@ @ @ @ }Tasking @tab native AIX threads
25653 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25655 @item @b{ppc-darwin}
25656 @item @code{@ @ }@i{rts-native (default)}
25657 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
25658 @item @code{@ @ @ @ }Exceptions @tab ZCX
25660 @item @b{sparc-solaris} @tab
25661 @item @code{@ @ }@i{rts-native (default)}
25662 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25663 @item @code{@ @ @ @ }Exceptions @tab ZCX
25665 @item @code{@ @ }@i{rts-pthread}
25666 @item @code{@ @ @ @ }Tasking @tab pthread library
25667 @item @code{@ @ @ @ }Exceptions @tab ZCX
25669 @item @code{@ @ }@i{rts-sjlj}
25670 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25671 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25673 @item @b{sparc64-solaris} @tab
25674 @item @code{@ @ }@i{rts-native (default)}
25675 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25676 @item @code{@ @ @ @ }Exceptions @tab ZCX
25678 @item @b{x86-linux}
25679 @item @code{@ @ }@i{rts-native (default)}
25680 @item @code{@ @ @ @ }Tasking @tab pthread library
25681 @item @code{@ @ @ @ }Exceptions @tab ZCX
25683 @item @code{@ @ }@i{rts-sjlj}
25684 @item @code{@ @ @ @ }Tasking @tab pthread library
25685 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25688 @item @code{@ @ }@i{rts-native (default)}
25689 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
25690 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25692 @item @b{x86-solaris}
25693 @item @code{@ @ }@i{rts-native (default)}
25694 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
25695 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25697 @item @b{x86-windows}
25698 @item @code{@ @ }@i{rts-native (default)}
25699 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25700 @item @code{@ @ @ @ }Exceptions @tab ZCX
25702 @item @code{@ @ }@i{rts-sjlj (default)}
25703 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25704 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25706 @item @b{x86-windows-rtx}
25707 @item @code{@ @ }@i{rts-rtx-rtss (default)}
25708 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
25709 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25711 @item @code{@ @ }@i{rts-rtx-w32}
25712 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
25713 @item @code{@ @ @ @ }Exceptions @tab ZCX
25715 @item @b{x86_64-linux}
25716 @item @code{@ @ }@i{rts-native (default)}
25717 @item @code{@ @ @ @ }Tasking @tab pthread library
25718 @item @code{@ @ @ @ }Exceptions @tab ZCX
25720 @item @code{@ @ }@i{rts-sjlj}
25721 @item @code{@ @ @ @ }Tasking @tab pthread library
25722 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25726 @node Specifying a Run-Time Library
25727 @section Specifying a Run-Time Library
25730 The @file{adainclude} subdirectory containing the sources of the GNAT
25731 run-time library, and the @file{adalib} subdirectory containing the
25732 @file{ALI} files and the static and/or shared GNAT library, are located
25733 in the gcc target-dependent area:
25736 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
25740 As indicated above, on some platforms several run-time libraries are supplied.
25741 These libraries are installed in the target dependent area and
25742 contain a complete source and binary subdirectory. The detailed description
25743 below explains the differences between the different libraries in terms of
25744 their thread support.
25746 The default run-time library (when GNAT is installed) is @emph{rts-native}.
25747 This default run time is selected by the means of soft links.
25748 For example on x86-linux:
25754 +--- adainclude----------+
25756 +--- adalib-----------+ |
25758 +--- rts-native | |
25760 | +--- adainclude <---+
25762 | +--- adalib <----+
25773 If the @i{rts-sjlj} library is to be selected on a permanent basis,
25774 these soft links can be modified with the following commands:
25778 $ rm -f adainclude adalib
25779 $ ln -s rts-sjlj/adainclude adainclude
25780 $ ln -s rts-sjlj/adalib adalib
25784 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
25785 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
25786 @file{$target/ada_object_path}.
25788 Selecting another run-time library temporarily can be
25789 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
25790 @cindex @option{--RTS} option
25792 @node Choosing the Scheduling Policy
25793 @section Choosing the Scheduling Policy
25796 When using a POSIX threads implementation, you have a choice of several
25797 scheduling policies: @code{SCHED_FIFO},
25798 @cindex @code{SCHED_FIFO} scheduling policy
25800 @cindex @code{SCHED_RR} scheduling policy
25801 and @code{SCHED_OTHER}.
25802 @cindex @code{SCHED_OTHER} scheduling policy
25803 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
25804 or @code{SCHED_RR} requires special (e.g., root) privileges.
25806 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
25808 @cindex @code{SCHED_FIFO} scheduling policy
25809 you can use one of the following:
25813 @code{pragma Time_Slice (0.0)}
25814 @cindex pragma Time_Slice
25816 the corresponding binder option @option{-T0}
25817 @cindex @option{-T0} option
25819 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
25820 @cindex pragma Task_Dispatching_Policy
25824 To specify @code{SCHED_RR},
25825 @cindex @code{SCHED_RR} scheduling policy
25826 you should use @code{pragma Time_Slice} with a
25827 value greater than @code{0.0}, or else use the corresponding @option{-T}
25830 @node Solaris-Specific Considerations
25831 @section Solaris-Specific Considerations
25832 @cindex Solaris Sparc threads libraries
25835 This section addresses some topics related to the various threads libraries
25839 * Solaris Threads Issues::
25842 @node Solaris Threads Issues
25843 @subsection Solaris Threads Issues
25846 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
25847 library based on POSIX threads --- @emph{rts-pthread}.
25848 @cindex rts-pthread threads library
25849 This run-time library has the advantage of being mostly shared across all
25850 POSIX-compliant thread implementations, and it also provides under
25851 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
25852 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
25853 and @code{PTHREAD_PRIO_PROTECT}
25854 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
25855 semantics that can be selected using the predefined pragma
25856 @code{Locking_Policy}
25857 @cindex pragma Locking_Policy (under rts-pthread)
25859 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
25860 @cindex @code{Inheritance_Locking} (under rts-pthread)
25861 @cindex @code{Ceiling_Locking} (under rts-pthread)
25863 As explained above, the native run-time library is based on the Solaris thread
25864 library (@code{libthread}) and is the default library.
25866 When the Solaris threads library is used (this is the default), programs
25867 compiled with GNAT can automatically take advantage of
25868 and can thus execute on multiple processors.
25869 The user can alternatively specify a processor on which the program should run
25870 to emulate a single-processor system. The multiprocessor / uniprocessor choice
25872 setting the environment variable @env{GNAT_PROCESSOR}
25873 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
25874 to one of the following:
25878 Use the default configuration (run the program on all
25879 available processors) - this is the same as having @code{GNAT_PROCESSOR}
25883 Let the run-time implementation choose one processor and run the program on
25886 @item 0 .. Last_Proc
25887 Run the program on the specified processor.
25888 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
25889 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
25892 @node Linux-Specific Considerations
25893 @section Linux-Specific Considerations
25894 @cindex Linux threads libraries
25897 On GNU/Linux without NPTL support (usually system with GNU C Library
25898 older than 2.3), the signal model is not POSIX compliant, which means
25899 that to send a signal to the process, you need to send the signal to all
25900 threads, e.g.@: by using @code{killpg()}.
25902 @node AIX-Specific Considerations
25903 @section AIX-Specific Considerations
25904 @cindex AIX resolver library
25907 On AIX, the resolver library initializes some internal structure on
25908 the first call to @code{get*by*} functions, which are used to implement
25909 @code{GNAT.Sockets.Get_Host_By_Name} and
25910 @code{GNAT.Sockets.Get_Host_By_Address}.
25911 If such initialization occurs within an Ada task, and the stack size for
25912 the task is the default size, a stack overflow may occur.
25914 To avoid this overflow, the user should either ensure that the first call
25915 to @code{GNAT.Sockets.Get_Host_By_Name} or
25916 @code{GNAT.Sockets.Get_Host_By_Addrss}
25917 occurs in the environment task, or use @code{pragma Storage_Size} to
25918 specify a sufficiently large size for the stack of the task that contains
25921 @node Irix-Specific Considerations
25922 @section Irix-Specific Considerations
25923 @cindex Irix libraries
25926 The GCC support libraries coming with the Irix compiler have moved to
25927 their canonical place with respect to the general Irix ABI related
25928 conventions. Running applications built with the default shared GNAT
25929 run-time now requires the LD_LIBRARY_PATH environment variable to
25930 include this location. A possible way to achieve this is to issue the
25931 following command line on a bash prompt:
25935 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
25939 @node RTX-Specific Considerations
25940 @section RTX-Specific Considerations
25941 @cindex RTX libraries
25944 The Real-time Extension (RTX) to Windows is based on the Windows Win32
25945 API. Applications can be built to work in two different modes:
25949 Windows executables that run in Ring 3 to utilize memory protection
25950 (@emph{rts-rtx-w32}).
25953 Real-time subsystem (RTSS) executables that run in Ring 0, where
25954 performance can be optimized with RTSS applications taking precedent
25955 over all Windows applications (@emph{rts-rtx-rtss}).
25959 @c *******************************
25960 @node Example of Binder Output File
25961 @appendix Example of Binder Output File
25964 This Appendix displays the source code for @command{gnatbind}'s output
25965 file generated for a simple ``Hello World'' program.
25966 Comments have been added for clarification purposes.
25968 @smallexample @c adanocomment
25972 -- The package is called Ada_Main unless this name is actually used
25973 -- as a unit name in the partition, in which case some other unique
25977 package ada_main is
25979 Elab_Final_Code : Integer;
25980 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
25982 -- The main program saves the parameters (argument count,
25983 -- argument values, environment pointer) in global variables
25984 -- for later access by other units including
25985 -- Ada.Command_Line.
25987 gnat_argc : Integer;
25988 gnat_argv : System.Address;
25989 gnat_envp : System.Address;
25991 -- The actual variables are stored in a library routine. This
25992 -- is useful for some shared library situations, where there
25993 -- are problems if variables are not in the library.
25995 pragma Import (C, gnat_argc);
25996 pragma Import (C, gnat_argv);
25997 pragma Import (C, gnat_envp);
25999 -- The exit status is similarly an external location
26001 gnat_exit_status : Integer;
26002 pragma Import (C, gnat_exit_status);
26004 GNAT_Version : constant String :=
26005 "GNAT Version: 6.0.0w (20061115)";
26006 pragma Export (C, GNAT_Version, "__gnat_version");
26008 -- This is the generated adafinal routine that performs
26009 -- finalization at the end of execution. In the case where
26010 -- Ada is the main program, this main program makes a call
26011 -- to adafinal at program termination.
26013 procedure adafinal;
26014 pragma Export (C, adafinal, "adafinal");
26016 -- This is the generated adainit routine that performs
26017 -- initialization at the start of execution. In the case
26018 -- where Ada is the main program, this main program makes
26019 -- a call to adainit at program startup.
26022 pragma Export (C, adainit, "adainit");
26024 -- This routine is called at the start of execution. It is
26025 -- a dummy routine that is used by the debugger to breakpoint
26026 -- at the start of execution.
26028 procedure Break_Start;
26029 pragma Import (C, Break_Start, "__gnat_break_start");
26031 -- This is the actual generated main program (it would be
26032 -- suppressed if the no main program switch were used). As
26033 -- required by standard system conventions, this program has
26034 -- the external name main.
26038 argv : System.Address;
26039 envp : System.Address)
26041 pragma Export (C, main, "main");
26043 -- The following set of constants give the version
26044 -- identification values for every unit in the bound
26045 -- partition. This identification is computed from all
26046 -- dependent semantic units, and corresponds to the
26047 -- string that would be returned by use of the
26048 -- Body_Version or Version attributes.
26050 type Version_32 is mod 2 ** 32;
26051 u00001 : constant Version_32 := 16#7880BEB3#;
26052 u00002 : constant Version_32 := 16#0D24CBD0#;
26053 u00003 : constant Version_32 := 16#3283DBEB#;
26054 u00004 : constant Version_32 := 16#2359F9ED#;
26055 u00005 : constant Version_32 := 16#664FB847#;
26056 u00006 : constant Version_32 := 16#68E803DF#;
26057 u00007 : constant Version_32 := 16#5572E604#;
26058 u00008 : constant Version_32 := 16#46B173D8#;
26059 u00009 : constant Version_32 := 16#156A40CF#;
26060 u00010 : constant Version_32 := 16#033DABE0#;
26061 u00011 : constant Version_32 := 16#6AB38FEA#;
26062 u00012 : constant Version_32 := 16#22B6217D#;
26063 u00013 : constant Version_32 := 16#68A22947#;
26064 u00014 : constant Version_32 := 16#18CC4A56#;
26065 u00015 : constant Version_32 := 16#08258E1B#;
26066 u00016 : constant Version_32 := 16#367D5222#;
26067 u00017 : constant Version_32 := 16#20C9ECA4#;
26068 u00018 : constant Version_32 := 16#50D32CB6#;
26069 u00019 : constant Version_32 := 16#39A8BB77#;
26070 u00020 : constant Version_32 := 16#5CF8FA2B#;
26071 u00021 : constant Version_32 := 16#2F1EB794#;
26072 u00022 : constant Version_32 := 16#31AB6444#;
26073 u00023 : constant Version_32 := 16#1574B6E9#;
26074 u00024 : constant Version_32 := 16#5109C189#;
26075 u00025 : constant Version_32 := 16#56D770CD#;
26076 u00026 : constant Version_32 := 16#02F9DE3D#;
26077 u00027 : constant Version_32 := 16#08AB6B2C#;
26078 u00028 : constant Version_32 := 16#3FA37670#;
26079 u00029 : constant Version_32 := 16#476457A0#;
26080 u00030 : constant Version_32 := 16#731E1B6E#;
26081 u00031 : constant Version_32 := 16#23C2E789#;
26082 u00032 : constant Version_32 := 16#0F1BD6A1#;
26083 u00033 : constant Version_32 := 16#7C25DE96#;
26084 u00034 : constant Version_32 := 16#39ADFFA2#;
26085 u00035 : constant Version_32 := 16#571DE3E7#;
26086 u00036 : constant Version_32 := 16#5EB646AB#;
26087 u00037 : constant Version_32 := 16#4249379B#;
26088 u00038 : constant Version_32 := 16#0357E00A#;
26089 u00039 : constant Version_32 := 16#3784FB72#;
26090 u00040 : constant Version_32 := 16#2E723019#;
26091 u00041 : constant Version_32 := 16#623358EA#;
26092 u00042 : constant Version_32 := 16#107F9465#;
26093 u00043 : constant Version_32 := 16#6843F68A#;
26094 u00044 : constant Version_32 := 16#63305874#;
26095 u00045 : constant Version_32 := 16#31E56CE1#;
26096 u00046 : constant Version_32 := 16#02917970#;
26097 u00047 : constant Version_32 := 16#6CCBA70E#;
26098 u00048 : constant Version_32 := 16#41CD4204#;
26099 u00049 : constant Version_32 := 16#572E3F58#;
26100 u00050 : constant Version_32 := 16#20729FF5#;
26101 u00051 : constant Version_32 := 16#1D4F93E8#;
26102 u00052 : constant Version_32 := 16#30B2EC3D#;
26103 u00053 : constant Version_32 := 16#34054F96#;
26104 u00054 : constant Version_32 := 16#5A199860#;
26105 u00055 : constant Version_32 := 16#0E7F912B#;
26106 u00056 : constant Version_32 := 16#5760634A#;
26107 u00057 : constant Version_32 := 16#5D851835#;
26109 -- The following Export pragmas export the version numbers
26110 -- with symbolic names ending in B (for body) or S
26111 -- (for spec) so that they can be located in a link. The
26112 -- information provided here is sufficient to track down
26113 -- the exact versions of units used in a given build.
26115 pragma Export (C, u00001, "helloB");
26116 pragma Export (C, u00002, "system__standard_libraryB");
26117 pragma Export (C, u00003, "system__standard_libraryS");
26118 pragma Export (C, u00004, "adaS");
26119 pragma Export (C, u00005, "ada__text_ioB");
26120 pragma Export (C, u00006, "ada__text_ioS");
26121 pragma Export (C, u00007, "ada__exceptionsB");
26122 pragma Export (C, u00008, "ada__exceptionsS");
26123 pragma Export (C, u00009, "gnatS");
26124 pragma Export (C, u00010, "gnat__heap_sort_aB");
26125 pragma Export (C, u00011, "gnat__heap_sort_aS");
26126 pragma Export (C, u00012, "systemS");
26127 pragma Export (C, u00013, "system__exception_tableB");
26128 pragma Export (C, u00014, "system__exception_tableS");
26129 pragma Export (C, u00015, "gnat__htableB");
26130 pragma Export (C, u00016, "gnat__htableS");
26131 pragma Export (C, u00017, "system__exceptionsS");
26132 pragma Export (C, u00018, "system__machine_state_operationsB");
26133 pragma Export (C, u00019, "system__machine_state_operationsS");
26134 pragma Export (C, u00020, "system__machine_codeS");
26135 pragma Export (C, u00021, "system__storage_elementsB");
26136 pragma Export (C, u00022, "system__storage_elementsS");
26137 pragma Export (C, u00023, "system__secondary_stackB");
26138 pragma Export (C, u00024, "system__secondary_stackS");
26139 pragma Export (C, u00025, "system__parametersB");
26140 pragma Export (C, u00026, "system__parametersS");
26141 pragma Export (C, u00027, "system__soft_linksB");
26142 pragma Export (C, u00028, "system__soft_linksS");
26143 pragma Export (C, u00029, "system__stack_checkingB");
26144 pragma Export (C, u00030, "system__stack_checkingS");
26145 pragma Export (C, u00031, "system__tracebackB");
26146 pragma Export (C, u00032, "system__tracebackS");
26147 pragma Export (C, u00033, "ada__streamsS");
26148 pragma Export (C, u00034, "ada__tagsB");
26149 pragma Export (C, u00035, "ada__tagsS");
26150 pragma Export (C, u00036, "system__string_opsB");
26151 pragma Export (C, u00037, "system__string_opsS");
26152 pragma Export (C, u00038, "interfacesS");
26153 pragma Export (C, u00039, "interfaces__c_streamsB");
26154 pragma Export (C, u00040, "interfaces__c_streamsS");
26155 pragma Export (C, u00041, "system__file_ioB");
26156 pragma Export (C, u00042, "system__file_ioS");
26157 pragma Export (C, u00043, "ada__finalizationB");
26158 pragma Export (C, u00044, "ada__finalizationS");
26159 pragma Export (C, u00045, "system__finalization_rootB");
26160 pragma Export (C, u00046, "system__finalization_rootS");
26161 pragma Export (C, u00047, "system__finalization_implementationB");
26162 pragma Export (C, u00048, "system__finalization_implementationS");
26163 pragma Export (C, u00049, "system__string_ops_concat_3B");
26164 pragma Export (C, u00050, "system__string_ops_concat_3S");
26165 pragma Export (C, u00051, "system__stream_attributesB");
26166 pragma Export (C, u00052, "system__stream_attributesS");
26167 pragma Export (C, u00053, "ada__io_exceptionsS");
26168 pragma Export (C, u00054, "system__unsigned_typesS");
26169 pragma Export (C, u00055, "system__file_control_blockS");
26170 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26171 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26173 -- BEGIN ELABORATION ORDER
26176 -- gnat.heap_sort_a (spec)
26177 -- gnat.heap_sort_a (body)
26178 -- gnat.htable (spec)
26179 -- gnat.htable (body)
26180 -- interfaces (spec)
26182 -- system.machine_code (spec)
26183 -- system.parameters (spec)
26184 -- system.parameters (body)
26185 -- interfaces.c_streams (spec)
26186 -- interfaces.c_streams (body)
26187 -- system.standard_library (spec)
26188 -- ada.exceptions (spec)
26189 -- system.exception_table (spec)
26190 -- system.exception_table (body)
26191 -- ada.io_exceptions (spec)
26192 -- system.exceptions (spec)
26193 -- system.storage_elements (spec)
26194 -- system.storage_elements (body)
26195 -- system.machine_state_operations (spec)
26196 -- system.machine_state_operations (body)
26197 -- system.secondary_stack (spec)
26198 -- system.stack_checking (spec)
26199 -- system.soft_links (spec)
26200 -- system.soft_links (body)
26201 -- system.stack_checking (body)
26202 -- system.secondary_stack (body)
26203 -- system.standard_library (body)
26204 -- system.string_ops (spec)
26205 -- system.string_ops (body)
26208 -- ada.streams (spec)
26209 -- system.finalization_root (spec)
26210 -- system.finalization_root (body)
26211 -- system.string_ops_concat_3 (spec)
26212 -- system.string_ops_concat_3 (body)
26213 -- system.traceback (spec)
26214 -- system.traceback (body)
26215 -- ada.exceptions (body)
26216 -- system.unsigned_types (spec)
26217 -- system.stream_attributes (spec)
26218 -- system.stream_attributes (body)
26219 -- system.finalization_implementation (spec)
26220 -- system.finalization_implementation (body)
26221 -- ada.finalization (spec)
26222 -- ada.finalization (body)
26223 -- ada.finalization.list_controller (spec)
26224 -- ada.finalization.list_controller (body)
26225 -- system.file_control_block (spec)
26226 -- system.file_io (spec)
26227 -- system.file_io (body)
26228 -- ada.text_io (spec)
26229 -- ada.text_io (body)
26231 -- END ELABORATION ORDER
26235 -- The following source file name pragmas allow the generated file
26236 -- names to be unique for different main programs. They are needed
26237 -- since the package name will always be Ada_Main.
26239 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26240 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26242 -- Generated package body for Ada_Main starts here
26244 package body ada_main is
26246 -- The actual finalization is performed by calling the
26247 -- library routine in System.Standard_Library.Adafinal
26249 procedure Do_Finalize;
26250 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26257 procedure adainit is
26259 -- These booleans are set to True once the associated unit has
26260 -- been elaborated. It is also used to avoid elaborating the
26261 -- same unit twice.
26264 pragma Import (Ada, E040, "interfaces__c_streams_E");
26267 pragma Import (Ada, E008, "ada__exceptions_E");
26270 pragma Import (Ada, E014, "system__exception_table_E");
26273 pragma Import (Ada, E053, "ada__io_exceptions_E");
26276 pragma Import (Ada, E017, "system__exceptions_E");
26279 pragma Import (Ada, E024, "system__secondary_stack_E");
26282 pragma Import (Ada, E030, "system__stack_checking_E");
26285 pragma Import (Ada, E028, "system__soft_links_E");
26288 pragma Import (Ada, E035, "ada__tags_E");
26291 pragma Import (Ada, E033, "ada__streams_E");
26294 pragma Import (Ada, E046, "system__finalization_root_E");
26297 pragma Import (Ada, E048, "system__finalization_implementation_E");
26300 pragma Import (Ada, E044, "ada__finalization_E");
26303 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26306 pragma Import (Ada, E055, "system__file_control_block_E");
26309 pragma Import (Ada, E042, "system__file_io_E");
26312 pragma Import (Ada, E006, "ada__text_io_E");
26314 -- Set_Globals is a library routine that stores away the
26315 -- value of the indicated set of global values in global
26316 -- variables within the library.
26318 procedure Set_Globals
26319 (Main_Priority : Integer;
26320 Time_Slice_Value : Integer;
26321 WC_Encoding : Character;
26322 Locking_Policy : Character;
26323 Queuing_Policy : Character;
26324 Task_Dispatching_Policy : Character;
26325 Adafinal : System.Address;
26326 Unreserve_All_Interrupts : Integer;
26327 Exception_Tracebacks : Integer);
26328 @findex __gnat_set_globals
26329 pragma Import (C, Set_Globals, "__gnat_set_globals");
26331 -- SDP_Table_Build is a library routine used to build the
26332 -- exception tables. See unit Ada.Exceptions in files
26333 -- a-except.ads/adb for full details of how zero cost
26334 -- exception handling works. This procedure, the call to
26335 -- it, and the two following tables are all omitted if the
26336 -- build is in longjmp/setjmp exception mode.
26338 @findex SDP_Table_Build
26339 @findex Zero Cost Exceptions
26340 procedure SDP_Table_Build
26341 (SDP_Addresses : System.Address;
26342 SDP_Count : Natural;
26343 Elab_Addresses : System.Address;
26344 Elab_Addr_Count : Natural);
26345 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
26347 -- Table of Unit_Exception_Table addresses. Used for zero
26348 -- cost exception handling to build the top level table.
26350 ST : aliased constant array (1 .. 23) of System.Address := (
26352 Ada.Text_Io'UET_Address,
26353 Ada.Exceptions'UET_Address,
26354 Gnat.Heap_Sort_A'UET_Address,
26355 System.Exception_Table'UET_Address,
26356 System.Machine_State_Operations'UET_Address,
26357 System.Secondary_Stack'UET_Address,
26358 System.Parameters'UET_Address,
26359 System.Soft_Links'UET_Address,
26360 System.Stack_Checking'UET_Address,
26361 System.Traceback'UET_Address,
26362 Ada.Streams'UET_Address,
26363 Ada.Tags'UET_Address,
26364 System.String_Ops'UET_Address,
26365 Interfaces.C_Streams'UET_Address,
26366 System.File_Io'UET_Address,
26367 Ada.Finalization'UET_Address,
26368 System.Finalization_Root'UET_Address,
26369 System.Finalization_Implementation'UET_Address,
26370 System.String_Ops_Concat_3'UET_Address,
26371 System.Stream_Attributes'UET_Address,
26372 System.File_Control_Block'UET_Address,
26373 Ada.Finalization.List_Controller'UET_Address);
26375 -- Table of addresses of elaboration routines. Used for
26376 -- zero cost exception handling to make sure these
26377 -- addresses are included in the top level procedure
26380 EA : aliased constant array (1 .. 23) of System.Address := (
26381 adainit'Code_Address,
26382 Do_Finalize'Code_Address,
26383 Ada.Exceptions'Elab_Spec'Address,
26384 System.Exceptions'Elab_Spec'Address,
26385 Interfaces.C_Streams'Elab_Spec'Address,
26386 System.Exception_Table'Elab_Body'Address,
26387 Ada.Io_Exceptions'Elab_Spec'Address,
26388 System.Stack_Checking'Elab_Spec'Address,
26389 System.Soft_Links'Elab_Body'Address,
26390 System.Secondary_Stack'Elab_Body'Address,
26391 Ada.Tags'Elab_Spec'Address,
26392 Ada.Tags'Elab_Body'Address,
26393 Ada.Streams'Elab_Spec'Address,
26394 System.Finalization_Root'Elab_Spec'Address,
26395 Ada.Exceptions'Elab_Body'Address,
26396 System.Finalization_Implementation'Elab_Spec'Address,
26397 System.Finalization_Implementation'Elab_Body'Address,
26398 Ada.Finalization'Elab_Spec'Address,
26399 Ada.Finalization.List_Controller'Elab_Spec'Address,
26400 System.File_Control_Block'Elab_Spec'Address,
26401 System.File_Io'Elab_Body'Address,
26402 Ada.Text_Io'Elab_Spec'Address,
26403 Ada.Text_Io'Elab_Body'Address);
26405 -- Start of processing for adainit
26409 -- Call SDP_Table_Build to build the top level procedure
26410 -- table for zero cost exception handling (omitted in
26411 -- longjmp/setjmp mode).
26413 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
26415 -- Call Set_Globals to record various information for
26416 -- this partition. The values are derived by the binder
26417 -- from information stored in the ali files by the compiler.
26419 @findex __gnat_set_globals
26421 (Main_Priority => -1,
26422 -- Priority of main program, -1 if no pragma Priority used
26424 Time_Slice_Value => -1,
26425 -- Time slice from Time_Slice pragma, -1 if none used
26427 WC_Encoding => 'b',
26428 -- Wide_Character encoding used, default is brackets
26430 Locking_Policy => ' ',
26431 -- Locking_Policy used, default of space means not
26432 -- specified, otherwise it is the first character of
26433 -- the policy name.
26435 Queuing_Policy => ' ',
26436 -- Queuing_Policy used, default of space means not
26437 -- specified, otherwise it is the first character of
26438 -- the policy name.
26440 Task_Dispatching_Policy => ' ',
26441 -- Task_Dispatching_Policy used, default of space means
26442 -- not specified, otherwise first character of the
26445 Adafinal => System.Null_Address,
26446 -- Address of Adafinal routine, not used anymore
26448 Unreserve_All_Interrupts => 0,
26449 -- Set true if pragma Unreserve_All_Interrupts was used
26451 Exception_Tracebacks => 0);
26452 -- Indicates if exception tracebacks are enabled
26454 Elab_Final_Code := 1;
26456 -- Now we have the elaboration calls for all units in the partition.
26457 -- The Elab_Spec and Elab_Body attributes generate references to the
26458 -- implicit elaboration procedures generated by the compiler for
26459 -- each unit that requires elaboration.
26462 Interfaces.C_Streams'Elab_Spec;
26466 Ada.Exceptions'Elab_Spec;
26469 System.Exception_Table'Elab_Body;
26473 Ada.Io_Exceptions'Elab_Spec;
26477 System.Exceptions'Elab_Spec;
26481 System.Stack_Checking'Elab_Spec;
26484 System.Soft_Links'Elab_Body;
26489 System.Secondary_Stack'Elab_Body;
26493 Ada.Tags'Elab_Spec;
26496 Ada.Tags'Elab_Body;
26500 Ada.Streams'Elab_Spec;
26504 System.Finalization_Root'Elab_Spec;
26508 Ada.Exceptions'Elab_Body;
26512 System.Finalization_Implementation'Elab_Spec;
26515 System.Finalization_Implementation'Elab_Body;
26519 Ada.Finalization'Elab_Spec;
26523 Ada.Finalization.List_Controller'Elab_Spec;
26527 System.File_Control_Block'Elab_Spec;
26531 System.File_Io'Elab_Body;
26535 Ada.Text_Io'Elab_Spec;
26538 Ada.Text_Io'Elab_Body;
26542 Elab_Final_Code := 0;
26550 procedure adafinal is
26559 -- main is actually a function, as in the ANSI C standard,
26560 -- defined to return the exit status. The three parameters
26561 -- are the argument count, argument values and environment
26564 @findex Main Program
26567 argv : System.Address;
26568 envp : System.Address)
26571 -- The initialize routine performs low level system
26572 -- initialization using a standard library routine which
26573 -- sets up signal handling and performs any other
26574 -- required setup. The routine can be found in file
26577 @findex __gnat_initialize
26578 procedure initialize;
26579 pragma Import (C, initialize, "__gnat_initialize");
26581 -- The finalize routine performs low level system
26582 -- finalization using a standard library routine. The
26583 -- routine is found in file a-final.c and in the standard
26584 -- distribution is a dummy routine that does nothing, so
26585 -- really this is a hook for special user finalization.
26587 @findex __gnat_finalize
26588 procedure finalize;
26589 pragma Import (C, finalize, "__gnat_finalize");
26591 -- We get to the main program of the partition by using
26592 -- pragma Import because if we try to with the unit and
26593 -- call it Ada style, then not only do we waste time
26594 -- recompiling it, but also, we don't really know the right
26595 -- switches (e.g.@: identifier character set) to be used
26598 procedure Ada_Main_Program;
26599 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
26601 -- Start of processing for main
26604 -- Save global variables
26610 -- Call low level system initialization
26614 -- Call our generated Ada initialization routine
26618 -- This is the point at which we want the debugger to get
26623 -- Now we call the main program of the partition
26627 -- Perform Ada finalization
26631 -- Perform low level system finalization
26635 -- Return the proper exit status
26636 return (gnat_exit_status);
26639 -- This section is entirely comments, so it has no effect on the
26640 -- compilation of the Ada_Main package. It provides the list of
26641 -- object files and linker options, as well as some standard
26642 -- libraries needed for the link. The gnatlink utility parses
26643 -- this b~hello.adb file to read these comment lines to generate
26644 -- the appropriate command line arguments for the call to the
26645 -- system linker. The BEGIN/END lines are used for sentinels for
26646 -- this parsing operation.
26648 -- The exact file names will of course depend on the environment,
26649 -- host/target and location of files on the host system.
26651 @findex Object file list
26652 -- BEGIN Object file/option list
26655 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
26656 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
26657 -- END Object file/option list
26663 The Ada code in the above example is exactly what is generated by the
26664 binder. We have added comments to more clearly indicate the function
26665 of each part of the generated @code{Ada_Main} package.
26667 The code is standard Ada in all respects, and can be processed by any
26668 tools that handle Ada. In particular, it is possible to use the debugger
26669 in Ada mode to debug the generated @code{Ada_Main} package. For example,
26670 suppose that for reasons that you do not understand, your program is crashing
26671 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
26672 you can place a breakpoint on the call:
26674 @smallexample @c ada
26675 Ada.Text_Io'Elab_Body;
26679 and trace the elaboration routine for this package to find out where
26680 the problem might be (more usually of course you would be debugging
26681 elaboration code in your own application).
26683 @node Elaboration Order Handling in GNAT
26684 @appendix Elaboration Order Handling in GNAT
26685 @cindex Order of elaboration
26686 @cindex Elaboration control
26689 * Elaboration Code::
26690 * Checking the Elaboration Order::
26691 * Controlling the Elaboration Order::
26692 * Controlling Elaboration in GNAT - Internal Calls::
26693 * Controlling Elaboration in GNAT - External Calls::
26694 * Default Behavior in GNAT - Ensuring Safety::
26695 * Treatment of Pragma Elaborate::
26696 * Elaboration Issues for Library Tasks::
26697 * Mixing Elaboration Models::
26698 * What to Do If the Default Elaboration Behavior Fails::
26699 * Elaboration for Access-to-Subprogram Values::
26700 * Summary of Procedures for Elaboration Control::
26701 * Other Elaboration Order Considerations::
26705 This chapter describes the handling of elaboration code in Ada and
26706 in GNAT, and discusses how the order of elaboration of program units can
26707 be controlled in GNAT, either automatically or with explicit programming
26710 @node Elaboration Code
26711 @section Elaboration Code
26714 Ada provides rather general mechanisms for executing code at elaboration
26715 time, that is to say before the main program starts executing. Such code arises
26719 @item Initializers for variables.
26720 Variables declared at the library level, in package specs or bodies, can
26721 require initialization that is performed at elaboration time, as in:
26722 @smallexample @c ada
26724 Sqrt_Half : Float := Sqrt (0.5);
26728 @item Package initialization code
26729 Code in a @code{BEGIN-END} section at the outer level of a package body is
26730 executed as part of the package body elaboration code.
26732 @item Library level task allocators
26733 Tasks that are declared using task allocators at the library level
26734 start executing immediately and hence can execute at elaboration time.
26738 Subprogram calls are possible in any of these contexts, which means that
26739 any arbitrary part of the program may be executed as part of the elaboration
26740 code. It is even possible to write a program which does all its work at
26741 elaboration time, with a null main program, although stylistically this
26742 would usually be considered an inappropriate way to structure
26745 An important concern arises in the context of elaboration code:
26746 we have to be sure that it is executed in an appropriate order. What we
26747 have is a series of elaboration code sections, potentially one section
26748 for each unit in the program. It is important that these execute
26749 in the correct order. Correctness here means that, taking the above
26750 example of the declaration of @code{Sqrt_Half},
26751 if some other piece of
26752 elaboration code references @code{Sqrt_Half},
26753 then it must run after the
26754 section of elaboration code that contains the declaration of
26757 There would never be any order of elaboration problem if we made a rule
26758 that whenever you @code{with} a unit, you must elaborate both the spec and body
26759 of that unit before elaborating the unit doing the @code{with}'ing:
26761 @smallexample @c ada
26765 package Unit_2 is @dots{}
26771 would require that both the body and spec of @code{Unit_1} be elaborated
26772 before the spec of @code{Unit_2}. However, a rule like that would be far too
26773 restrictive. In particular, it would make it impossible to have routines
26774 in separate packages that were mutually recursive.
26776 You might think that a clever enough compiler could look at the actual
26777 elaboration code and determine an appropriate correct order of elaboration,
26778 but in the general case, this is not possible. Consider the following
26781 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
26783 the variable @code{Sqrt_1}, which is declared in the elaboration code
26784 of the body of @code{Unit_1}:
26786 @smallexample @c ada
26788 Sqrt_1 : Float := Sqrt (0.1);
26793 The elaboration code of the body of @code{Unit_1} also contains:
26795 @smallexample @c ada
26798 if expression_1 = 1 then
26799 Q := Unit_2.Func_2;
26806 @code{Unit_2} is exactly parallel,
26807 it has a procedure @code{Func_2} that references
26808 the variable @code{Sqrt_2}, which is declared in the elaboration code of
26809 the body @code{Unit_2}:
26811 @smallexample @c ada
26813 Sqrt_2 : Float := Sqrt (0.1);
26818 The elaboration code of the body of @code{Unit_2} also contains:
26820 @smallexample @c ada
26823 if expression_2 = 2 then
26824 Q := Unit_1.Func_1;
26831 Now the question is, which of the following orders of elaboration is
26856 If you carefully analyze the flow here, you will see that you cannot tell
26857 at compile time the answer to this question.
26858 If @code{expression_1} is not equal to 1,
26859 and @code{expression_2} is not equal to 2,
26860 then either order is acceptable, because neither of the function calls is
26861 executed. If both tests evaluate to true, then neither order is acceptable
26862 and in fact there is no correct order.
26864 If one of the two expressions is true, and the other is false, then one
26865 of the above orders is correct, and the other is incorrect. For example,
26866 if @code{expression_1} /= 1 and @code{expression_2} = 2,
26867 then the call to @code{Func_1}
26868 will occur, but not the call to @code{Func_2.}
26869 This means that it is essential
26870 to elaborate the body of @code{Unit_1} before
26871 the body of @code{Unit_2}, so the first
26872 order of elaboration is correct and the second is wrong.
26874 By making @code{expression_1} and @code{expression_2}
26875 depend on input data, or perhaps
26876 the time of day, we can make it impossible for the compiler or binder
26877 to figure out which of these expressions will be true, and hence it
26878 is impossible to guarantee a safe order of elaboration at run time.
26880 @node Checking the Elaboration Order
26881 @section Checking the Elaboration Order
26884 In some languages that involve the same kind of elaboration problems,
26885 e.g.@: Java and C++, the programmer is expected to worry about these
26886 ordering problems himself, and it is common to
26887 write a program in which an incorrect elaboration order gives
26888 surprising results, because it references variables before they
26890 Ada is designed to be a safe language, and a programmer-beware approach is
26891 clearly not sufficient. Consequently, the language provides three lines
26895 @item Standard rules
26896 Some standard rules restrict the possible choice of elaboration
26897 order. In particular, if you @code{with} a unit, then its spec is always
26898 elaborated before the unit doing the @code{with}. Similarly, a parent
26899 spec is always elaborated before the child spec, and finally
26900 a spec is always elaborated before its corresponding body.
26902 @item Dynamic elaboration checks
26903 @cindex Elaboration checks
26904 @cindex Checks, elaboration
26905 Dynamic checks are made at run time, so that if some entity is accessed
26906 before it is elaborated (typically by means of a subprogram call)
26907 then the exception (@code{Program_Error}) is raised.
26909 @item Elaboration control
26910 Facilities are provided for the programmer to specify the desired order
26914 Let's look at these facilities in more detail. First, the rules for
26915 dynamic checking. One possible rule would be simply to say that the
26916 exception is raised if you access a variable which has not yet been
26917 elaborated. The trouble with this approach is that it could require
26918 expensive checks on every variable reference. Instead Ada has two
26919 rules which are a little more restrictive, but easier to check, and
26923 @item Restrictions on calls
26924 A subprogram can only be called at elaboration time if its body
26925 has been elaborated. The rules for elaboration given above guarantee
26926 that the spec of the subprogram has been elaborated before the
26927 call, but not the body. If this rule is violated, then the
26928 exception @code{Program_Error} is raised.
26930 @item Restrictions on instantiations
26931 A generic unit can only be instantiated if the body of the generic
26932 unit has been elaborated. Again, the rules for elaboration given above
26933 guarantee that the spec of the generic unit has been elaborated
26934 before the instantiation, but not the body. If this rule is
26935 violated, then the exception @code{Program_Error} is raised.
26939 The idea is that if the body has been elaborated, then any variables
26940 it references must have been elaborated; by checking for the body being
26941 elaborated we guarantee that none of its references causes any
26942 trouble. As we noted above, this is a little too restrictive, because a
26943 subprogram that has no non-local references in its body may in fact be safe
26944 to call. However, it really would be unsafe to rely on this, because
26945 it would mean that the caller was aware of details of the implementation
26946 in the body. This goes against the basic tenets of Ada.
26948 A plausible implementation can be described as follows.
26949 A Boolean variable is associated with each subprogram
26950 and each generic unit. This variable is initialized to False, and is set to
26951 True at the point body is elaborated. Every call or instantiation checks the
26952 variable, and raises @code{Program_Error} if the variable is False.
26954 Note that one might think that it would be good enough to have one Boolean
26955 variable for each package, but that would not deal with cases of trying
26956 to call a body in the same package as the call
26957 that has not been elaborated yet.
26958 Of course a compiler may be able to do enough analysis to optimize away
26959 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
26960 does such optimizations, but still the easiest conceptual model is to
26961 think of there being one variable per subprogram.
26963 @node Controlling the Elaboration Order
26964 @section Controlling the Elaboration Order
26967 In the previous section we discussed the rules in Ada which ensure
26968 that @code{Program_Error} is raised if an incorrect elaboration order is
26969 chosen. This prevents erroneous executions, but we need mechanisms to
26970 specify a correct execution and avoid the exception altogether.
26971 To achieve this, Ada provides a number of features for controlling
26972 the order of elaboration. We discuss these features in this section.
26974 First, there are several ways of indicating to the compiler that a given
26975 unit has no elaboration problems:
26978 @item packages that do not require a body
26979 A library package that does not require a body does not permit
26980 a body (this rule was introduced in Ada 95).
26981 Thus if we have a such a package, as in:
26983 @smallexample @c ada
26986 package Definitions is
26988 type m is new integer;
26990 type a is array (1 .. 10) of m;
26991 type b is array (1 .. 20) of m;
26999 A package that @code{with}'s @code{Definitions} may safely instantiate
27000 @code{Definitions.Subp} because the compiler can determine that there
27001 definitely is no package body to worry about in this case
27004 @cindex pragma Pure
27006 Places sufficient restrictions on a unit to guarantee that
27007 no call to any subprogram in the unit can result in an
27008 elaboration problem. This means that the compiler does not need
27009 to worry about the point of elaboration of such units, and in
27010 particular, does not need to check any calls to any subprograms
27013 @item pragma Preelaborate
27014 @findex Preelaborate
27015 @cindex pragma Preelaborate
27016 This pragma places slightly less stringent restrictions on a unit than
27018 but these restrictions are still sufficient to ensure that there
27019 are no elaboration problems with any calls to the unit.
27021 @item pragma Elaborate_Body
27022 @findex Elaborate_Body
27023 @cindex pragma Elaborate_Body
27024 This pragma requires that the body of a unit be elaborated immediately
27025 after its spec. Suppose a unit @code{A} has such a pragma,
27026 and unit @code{B} does
27027 a @code{with} of unit @code{A}. Recall that the standard rules require
27028 the spec of unit @code{A}
27029 to be elaborated before the @code{with}'ing unit; given the pragma in
27030 @code{A}, we also know that the body of @code{A}
27031 will be elaborated before @code{B}, so
27032 that calls to @code{A} are safe and do not need a check.
27037 unlike pragma @code{Pure} and pragma @code{Preelaborate},
27039 @code{Elaborate_Body} does not guarantee that the program is
27040 free of elaboration problems, because it may not be possible
27041 to satisfy the requested elaboration order.
27042 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
27044 marks @code{Unit_1} as @code{Elaborate_Body},
27045 and not @code{Unit_2,} then the order of
27046 elaboration will be:
27058 Now that means that the call to @code{Func_1} in @code{Unit_2}
27059 need not be checked,
27060 it must be safe. But the call to @code{Func_2} in
27061 @code{Unit_1} may still fail if
27062 @code{Expression_1} is equal to 1,
27063 and the programmer must still take
27064 responsibility for this not being the case.
27066 If all units carry a pragma @code{Elaborate_Body}, then all problems are
27067 eliminated, except for calls entirely within a body, which are
27068 in any case fully under programmer control. However, using the pragma
27069 everywhere is not always possible.
27070 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
27071 we marked both of them as having pragma @code{Elaborate_Body}, then
27072 clearly there would be no possible elaboration order.
27074 The above pragmas allow a server to guarantee safe use by clients, and
27075 clearly this is the preferable approach. Consequently a good rule
27076 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
27077 and if this is not possible,
27078 mark them as @code{Elaborate_Body} if possible.
27079 As we have seen, there are situations where neither of these
27080 three pragmas can be used.
27081 So we also provide methods for clients to control the
27082 order of elaboration of the servers on which they depend:
27085 @item pragma Elaborate (unit)
27087 @cindex pragma Elaborate
27088 This pragma is placed in the context clause, after a @code{with} clause,
27089 and it requires that the body of the named unit be elaborated before
27090 the unit in which the pragma occurs. The idea is to use this pragma
27091 if the current unit calls at elaboration time, directly or indirectly,
27092 some subprogram in the named unit.
27094 @item pragma Elaborate_All (unit)
27095 @findex Elaborate_All
27096 @cindex pragma Elaborate_All
27097 This is a stronger version of the Elaborate pragma. Consider the
27101 Unit A @code{with}'s unit B and calls B.Func in elab code
27102 Unit B @code{with}'s unit C, and B.Func calls C.Func
27106 Now if we put a pragma @code{Elaborate (B)}
27107 in unit @code{A}, this ensures that the
27108 body of @code{B} is elaborated before the call, but not the
27109 body of @code{C}, so
27110 the call to @code{C.Func} could still cause @code{Program_Error} to
27113 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27114 not only that the body of the named unit be elaborated before the
27115 unit doing the @code{with}, but also the bodies of all units that the
27116 named unit uses, following @code{with} links transitively. For example,
27117 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27119 not only that the body of @code{B} be elaborated before @code{A},
27121 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27125 We are now in a position to give a usage rule in Ada for avoiding
27126 elaboration problems, at least if dynamic dispatching and access to
27127 subprogram values are not used. We will handle these cases separately
27130 The rule is simple. If a unit has elaboration code that can directly or
27131 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27132 a generic package in a @code{with}'ed unit,
27133 then if the @code{with}'ed unit does not have
27134 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27135 a pragma @code{Elaborate_All}
27136 for the @code{with}'ed unit. By following this rule a client is
27137 assured that calls can be made without risk of an exception.
27139 For generic subprogram instantiations, the rule can be relaxed to
27140 require only a pragma @code{Elaborate} since elaborating the body
27141 of a subprogram cannot cause any transitive elaboration (we are
27142 not calling the subprogram in this case, just elaborating its
27145 If this rule is not followed, then a program may be in one of four
27149 @item No order exists
27150 No order of elaboration exists which follows the rules, taking into
27151 account any @code{Elaborate}, @code{Elaborate_All},
27152 or @code{Elaborate_Body} pragmas. In
27153 this case, an Ada compiler must diagnose the situation at bind
27154 time, and refuse to build an executable program.
27156 @item One or more orders exist, all incorrect
27157 One or more acceptable elaboration orders exist, and all of them
27158 generate an elaboration order problem. In this case, the binder
27159 can build an executable program, but @code{Program_Error} will be raised
27160 when the program is run.
27162 @item Several orders exist, some right, some incorrect
27163 One or more acceptable elaboration orders exists, and some of them
27164 work, and some do not. The programmer has not controlled
27165 the order of elaboration, so the binder may or may not pick one of
27166 the correct orders, and the program may or may not raise an
27167 exception when it is run. This is the worst case, because it means
27168 that the program may fail when moved to another compiler, or even
27169 another version of the same compiler.
27171 @item One or more orders exists, all correct
27172 One ore more acceptable elaboration orders exist, and all of them
27173 work. In this case the program runs successfully. This state of
27174 affairs can be guaranteed by following the rule we gave above, but
27175 may be true even if the rule is not followed.
27179 Note that one additional advantage of following our rules on the use
27180 of @code{Elaborate} and @code{Elaborate_All}
27181 is that the program continues to stay in the ideal (all orders OK) state
27182 even if maintenance
27183 changes some bodies of some units. Conversely, if a program that does
27184 not follow this rule happens to be safe at some point, this state of affairs
27185 may deteriorate silently as a result of maintenance changes.
27187 You may have noticed that the above discussion did not mention
27188 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27189 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27190 code in the body makes calls to some other unit, so it is still necessary
27191 to use @code{Elaborate_All} on such units.
27193 @node Controlling Elaboration in GNAT - Internal Calls
27194 @section Controlling Elaboration in GNAT - Internal Calls
27197 In the case of internal calls, i.e., calls within a single package, the
27198 programmer has full control over the order of elaboration, and it is up
27199 to the programmer to elaborate declarations in an appropriate order. For
27202 @smallexample @c ada
27205 function One return Float;
27209 function One return Float is
27218 will obviously raise @code{Program_Error} at run time, because function
27219 One will be called before its body is elaborated. In this case GNAT will
27220 generate a warning that the call will raise @code{Program_Error}:
27226 2. function One return Float;
27228 4. Q : Float := One;
27230 >>> warning: cannot call "One" before body is elaborated
27231 >>> warning: Program_Error will be raised at run time
27234 6. function One return Float is
27247 Note that in this particular case, it is likely that the call is safe, because
27248 the function @code{One} does not access any global variables.
27249 Nevertheless in Ada, we do not want the validity of the check to depend on
27250 the contents of the body (think about the separate compilation case), so this
27251 is still wrong, as we discussed in the previous sections.
27253 The error is easily corrected by rearranging the declarations so that the
27254 body of @code{One} appears before the declaration containing the call
27255 (note that in Ada 95 and Ada 2005,
27256 declarations can appear in any order, so there is no restriction that
27257 would prevent this reordering, and if we write:
27259 @smallexample @c ada
27262 function One return Float;
27264 function One return Float is
27275 then all is well, no warning is generated, and no
27276 @code{Program_Error} exception
27278 Things are more complicated when a chain of subprograms is executed:
27280 @smallexample @c ada
27283 function A return Integer;
27284 function B return Integer;
27285 function C return Integer;
27287 function B return Integer is begin return A; end;
27288 function C return Integer is begin return B; end;
27292 function A return Integer is begin return 1; end;
27298 Now the call to @code{C}
27299 at elaboration time in the declaration of @code{X} is correct, because
27300 the body of @code{C} is already elaborated,
27301 and the call to @code{B} within the body of
27302 @code{C} is correct, but the call
27303 to @code{A} within the body of @code{B} is incorrect, because the body
27304 of @code{A} has not been elaborated, so @code{Program_Error}
27305 will be raised on the call to @code{A}.
27306 In this case GNAT will generate a
27307 warning that @code{Program_Error} may be
27308 raised at the point of the call. Let's look at the warning:
27314 2. function A return Integer;
27315 3. function B return Integer;
27316 4. function C return Integer;
27318 6. function B return Integer is begin return A; end;
27320 >>> warning: call to "A" before body is elaborated may
27321 raise Program_Error
27322 >>> warning: "B" called at line 7
27323 >>> warning: "C" called at line 9
27325 7. function C return Integer is begin return B; end;
27327 9. X : Integer := C;
27329 11. function A return Integer is begin return 1; end;
27339 Note that the message here says ``may raise'', instead of the direct case,
27340 where the message says ``will be raised''. That's because whether
27342 actually called depends in general on run-time flow of control.
27343 For example, if the body of @code{B} said
27345 @smallexample @c ada
27348 function B return Integer is
27350 if some-condition-depending-on-input-data then
27361 then we could not know until run time whether the incorrect call to A would
27362 actually occur, so @code{Program_Error} might
27363 or might not be raised. It is possible for a compiler to
27364 do a better job of analyzing bodies, to
27365 determine whether or not @code{Program_Error}
27366 might be raised, but it certainly
27367 couldn't do a perfect job (that would require solving the halting problem
27368 and is provably impossible), and because this is a warning anyway, it does
27369 not seem worth the effort to do the analysis. Cases in which it
27370 would be relevant are rare.
27372 In practice, warnings of either of the forms given
27373 above will usually correspond to
27374 real errors, and should be examined carefully and eliminated.
27375 In the rare case where a warning is bogus, it can be suppressed by any of
27376 the following methods:
27380 Compile with the @option{-gnatws} switch set
27383 Suppress @code{Elaboration_Check} for the called subprogram
27386 Use pragma @code{Warnings_Off} to turn warnings off for the call
27390 For the internal elaboration check case,
27391 GNAT by default generates the
27392 necessary run-time checks to ensure
27393 that @code{Program_Error} is raised if any
27394 call fails an elaboration check. Of course this can only happen if a
27395 warning has been issued as described above. The use of pragma
27396 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
27397 some of these checks, meaning that it may be possible (but is not
27398 guaranteed) for a program to be able to call a subprogram whose body
27399 is not yet elaborated, without raising a @code{Program_Error} exception.
27401 @node Controlling Elaboration in GNAT - External Calls
27402 @section Controlling Elaboration in GNAT - External Calls
27405 The previous section discussed the case in which the execution of a
27406 particular thread of elaboration code occurred entirely within a
27407 single unit. This is the easy case to handle, because a programmer
27408 has direct and total control over the order of elaboration, and
27409 furthermore, checks need only be generated in cases which are rare
27410 and which the compiler can easily detect.
27411 The situation is more complex when separate compilation is taken into account.
27412 Consider the following:
27414 @smallexample @c ada
27418 function Sqrt (Arg : Float) return Float;
27421 package body Math is
27422 function Sqrt (Arg : Float) return Float is
27431 X : Float := Math.Sqrt (0.5);
27444 where @code{Main} is the main program. When this program is executed, the
27445 elaboration code must first be executed, and one of the jobs of the
27446 binder is to determine the order in which the units of a program are
27447 to be elaborated. In this case we have four units: the spec and body
27449 the spec of @code{Stuff} and the body of @code{Main}).
27450 In what order should the four separate sections of elaboration code
27453 There are some restrictions in the order of elaboration that the binder
27454 can choose. In particular, if unit U has a @code{with}
27455 for a package @code{X}, then you
27456 are assured that the spec of @code{X}
27457 is elaborated before U , but you are
27458 not assured that the body of @code{X}
27459 is elaborated before U.
27460 This means that in the above case, the binder is allowed to choose the
27471 but that's not good, because now the call to @code{Math.Sqrt}
27472 that happens during
27473 the elaboration of the @code{Stuff}
27474 spec happens before the body of @code{Math.Sqrt} is
27475 elaborated, and hence causes @code{Program_Error} exception to be raised.
27476 At first glance, one might say that the binder is misbehaving, because
27477 obviously you want to elaborate the body of something you @code{with}
27479 that is not a general rule that can be followed in all cases. Consider
27481 @smallexample @c ada
27484 package X is @dots{}
27486 package Y is @dots{}
27489 package body Y is @dots{}
27492 package body X is @dots{}
27498 This is a common arrangement, and, apart from the order of elaboration
27499 problems that might arise in connection with elaboration code, this works fine.
27500 A rule that says that you must first elaborate the body of anything you
27501 @code{with} cannot work in this case:
27502 the body of @code{X} @code{with}'s @code{Y},
27503 which means you would have to
27504 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
27506 you have to elaborate the body of @code{X} first, but @dots{} and we have a
27507 loop that cannot be broken.
27509 It is true that the binder can in many cases guess an order of elaboration
27510 that is unlikely to cause a @code{Program_Error}
27511 exception to be raised, and it tries to do so (in the
27512 above example of @code{Math/Stuff/Spec}, the GNAT binder will
27514 elaborate the body of @code{Math} right after its spec, so all will be well).
27516 However, a program that blindly relies on the binder to be helpful can
27517 get into trouble, as we discussed in the previous sections, so
27519 provides a number of facilities for assisting the programmer in
27520 developing programs that are robust with respect to elaboration order.
27522 @node Default Behavior in GNAT - Ensuring Safety
27523 @section Default Behavior in GNAT - Ensuring Safety
27526 The default behavior in GNAT ensures elaboration safety. In its
27527 default mode GNAT implements the
27528 rule we previously described as the right approach. Let's restate it:
27532 @emph{If a unit has elaboration code that can directly or indirectly make a
27533 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
27534 package in a @code{with}'ed unit, then if the @code{with}'ed unit
27535 does not have pragma @code{Pure} or
27536 @code{Preelaborate}, then the client should have an
27537 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
27539 @emph{In the case of instantiating a generic subprogram, it is always
27540 sufficient to have only an @code{Elaborate} pragma for the
27541 @code{with}'ed unit.}
27545 By following this rule a client is assured that calls and instantiations
27546 can be made without risk of an exception.
27548 In this mode GNAT traces all calls that are potentially made from
27549 elaboration code, and puts in any missing implicit @code{Elaborate}
27550 and @code{Elaborate_All} pragmas.
27551 The advantage of this approach is that no elaboration problems
27552 are possible if the binder can find an elaboration order that is
27553 consistent with these implicit @code{Elaborate} and
27554 @code{Elaborate_All} pragmas. The
27555 disadvantage of this approach is that no such order may exist.
27557 If the binder does not generate any diagnostics, then it means that it has
27558 found an elaboration order that is guaranteed to be safe. However, the binder
27559 may still be relying on implicitly generated @code{Elaborate} and
27560 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
27563 If it is important to guarantee portability, then the compilations should
27566 (warn on elaboration problems) switch. This will cause warning messages
27567 to be generated indicating the missing @code{Elaborate} and
27568 @code{Elaborate_All} pragmas.
27569 Consider the following source program:
27571 @smallexample @c ada
27576 m : integer := k.r;
27583 where it is clear that there
27584 should be a pragma @code{Elaborate_All}
27585 for unit @code{k}. An implicit pragma will be generated, and it is
27586 likely that the binder will be able to honor it. However, if you want
27587 to port this program to some other Ada compiler than GNAT.
27588 it is safer to include the pragma explicitly in the source. If this
27589 unit is compiled with the
27591 switch, then the compiler outputs a warning:
27598 3. m : integer := k.r;
27600 >>> warning: call to "r" may raise Program_Error
27601 >>> warning: missing pragma Elaborate_All for "k"
27609 and these warnings can be used as a guide for supplying manually
27610 the missing pragmas. It is usually a bad idea to use this warning
27611 option during development. That's because it will warn you when
27612 you need to put in a pragma, but cannot warn you when it is time
27613 to take it out. So the use of pragma @code{Elaborate_All} may lead to
27614 unnecessary dependencies and even false circularities.
27616 This default mode is more restrictive than the Ada Reference
27617 Manual, and it is possible to construct programs which will compile
27618 using the dynamic model described there, but will run into a
27619 circularity using the safer static model we have described.
27621 Of course any Ada compiler must be able to operate in a mode
27622 consistent with the requirements of the Ada Reference Manual,
27623 and in particular must have the capability of implementing the
27624 standard dynamic model of elaboration with run-time checks.
27626 In GNAT, this standard mode can be achieved either by the use of
27627 the @option{-gnatE} switch on the compiler (@command{gcc} or
27628 @command{gnatmake}) command, or by the use of the configuration pragma:
27630 @smallexample @c ada
27631 pragma Elaboration_Checks (RM);
27635 Either approach will cause the unit affected to be compiled using the
27636 standard dynamic run-time elaboration checks described in the Ada
27637 Reference Manual. The static model is generally preferable, since it
27638 is clearly safer to rely on compile and link time checks rather than
27639 run-time checks. However, in the case of legacy code, it may be
27640 difficult to meet the requirements of the static model. This
27641 issue is further discussed in
27642 @ref{What to Do If the Default Elaboration Behavior Fails}.
27644 Note that the static model provides a strict subset of the allowed
27645 behavior and programs of the Ada Reference Manual, so if you do
27646 adhere to the static model and no circularities exist,
27647 then you are assured that your program will
27648 work using the dynamic model, providing that you remove any
27649 pragma Elaborate statements from the source.
27651 @node Treatment of Pragma Elaborate
27652 @section Treatment of Pragma Elaborate
27653 @cindex Pragma Elaborate
27656 The use of @code{pragma Elaborate}
27657 should generally be avoided in Ada 95 and Ada 2005 programs,
27658 since there is no guarantee that transitive calls
27659 will be properly handled. Indeed at one point, this pragma was placed
27660 in Annex J (Obsolescent Features), on the grounds that it is never useful.
27662 Now that's a bit restrictive. In practice, the case in which
27663 @code{pragma Elaborate} is useful is when the caller knows that there
27664 are no transitive calls, or that the called unit contains all necessary
27665 transitive @code{pragma Elaborate} statements, and legacy code often
27666 contains such uses.
27668 Strictly speaking the static mode in GNAT should ignore such pragmas,
27669 since there is no assurance at compile time that the necessary safety
27670 conditions are met. In practice, this would cause GNAT to be incompatible
27671 with correctly written Ada 83 code that had all necessary
27672 @code{pragma Elaborate} statements in place. Consequently, we made the
27673 decision that GNAT in its default mode will believe that if it encounters
27674 a @code{pragma Elaborate} then the programmer knows what they are doing,
27675 and it will trust that no elaboration errors can occur.
27677 The result of this decision is two-fold. First to be safe using the
27678 static mode, you should remove all @code{pragma Elaborate} statements.
27679 Second, when fixing circularities in existing code, you can selectively
27680 use @code{pragma Elaborate} statements to convince the static mode of
27681 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
27684 When using the static mode with @option{-gnatwl}, any use of
27685 @code{pragma Elaborate} will generate a warning about possible
27688 @node Elaboration Issues for Library Tasks
27689 @section Elaboration Issues for Library Tasks
27690 @cindex Library tasks, elaboration issues
27691 @cindex Elaboration of library tasks
27694 In this section we examine special elaboration issues that arise for
27695 programs that declare library level tasks.
27697 Generally the model of execution of an Ada program is that all units are
27698 elaborated, and then execution of the program starts. However, the
27699 declaration of library tasks definitely does not fit this model. The
27700 reason for this is that library tasks start as soon as they are declared
27701 (more precisely, as soon as the statement part of the enclosing package
27702 body is reached), that is to say before elaboration
27703 of the program is complete. This means that if such a task calls a
27704 subprogram, or an entry in another task, the callee may or may not be
27705 elaborated yet, and in the standard
27706 Reference Manual model of dynamic elaboration checks, you can even
27707 get timing dependent Program_Error exceptions, since there can be
27708 a race between the elaboration code and the task code.
27710 The static model of elaboration in GNAT seeks to avoid all such
27711 dynamic behavior, by being conservative, and the conservative
27712 approach in this particular case is to assume that all the code
27713 in a task body is potentially executed at elaboration time if
27714 a task is declared at the library level.
27716 This can definitely result in unexpected circularities. Consider
27717 the following example
27719 @smallexample @c ada
27725 type My_Int is new Integer;
27727 function Ident (M : My_Int) return My_Int;
27731 package body Decls is
27732 task body Lib_Task is
27738 function Ident (M : My_Int) return My_Int is
27746 procedure Put_Val (Arg : Decls.My_Int);
27750 package body Utils is
27751 procedure Put_Val (Arg : Decls.My_Int) is
27753 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
27760 Decls.Lib_Task.Start;
27765 If the above example is compiled in the default static elaboration
27766 mode, then a circularity occurs. The circularity comes from the call
27767 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
27768 this call occurs in elaboration code, we need an implicit pragma
27769 @code{Elaborate_All} for @code{Utils}. This means that not only must
27770 the spec and body of @code{Utils} be elaborated before the body
27771 of @code{Decls}, but also the spec and body of any unit that is
27772 @code{with'ed} by the body of @code{Utils} must also be elaborated before
27773 the body of @code{Decls}. This is the transitive implication of
27774 pragma @code{Elaborate_All} and it makes sense, because in general
27775 the body of @code{Put_Val} might have a call to something in a
27776 @code{with'ed} unit.
27778 In this case, the body of Utils (actually its spec) @code{with's}
27779 @code{Decls}. Unfortunately this means that the body of @code{Decls}
27780 must be elaborated before itself, in case there is a call from the
27781 body of @code{Utils}.
27783 Here is the exact chain of events we are worrying about:
27787 In the body of @code{Decls} a call is made from within the body of a library
27788 task to a subprogram in the package @code{Utils}. Since this call may
27789 occur at elaboration time (given that the task is activated at elaboration
27790 time), we have to assume the worst, i.e., that the
27791 call does happen at elaboration time.
27794 This means that the body and spec of @code{Util} must be elaborated before
27795 the body of @code{Decls} so that this call does not cause an access before
27799 Within the body of @code{Util}, specifically within the body of
27800 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
27804 One such @code{with}'ed package is package @code{Decls}, so there
27805 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
27806 In fact there is such a call in this example, but we would have to
27807 assume that there was such a call even if it were not there, since
27808 we are not supposed to write the body of @code{Decls} knowing what
27809 is in the body of @code{Utils}; certainly in the case of the
27810 static elaboration model, the compiler does not know what is in
27811 other bodies and must assume the worst.
27814 This means that the spec and body of @code{Decls} must also be
27815 elaborated before we elaborate the unit containing the call, but
27816 that unit is @code{Decls}! This means that the body of @code{Decls}
27817 must be elaborated before itself, and that's a circularity.
27821 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
27822 the body of @code{Decls} you will get a true Ada Reference Manual
27823 circularity that makes the program illegal.
27825 In practice, we have found that problems with the static model of
27826 elaboration in existing code often arise from library tasks, so
27827 we must address this particular situation.
27829 Note that if we compile and run the program above, using the dynamic model of
27830 elaboration (that is to say use the @option{-gnatE} switch),
27831 then it compiles, binds,
27832 links, and runs, printing the expected result of 2. Therefore in some sense
27833 the circularity here is only apparent, and we need to capture
27834 the properties of this program that distinguish it from other library-level
27835 tasks that have real elaboration problems.
27837 We have four possible answers to this question:
27842 Use the dynamic model of elaboration.
27844 If we use the @option{-gnatE} switch, then as noted above, the program works.
27845 Why is this? If we examine the task body, it is apparent that the task cannot
27847 @code{accept} statement until after elaboration has been completed, because
27848 the corresponding entry call comes from the main program, not earlier.
27849 This is why the dynamic model works here. But that's really giving
27850 up on a precise analysis, and we prefer to take this approach only if we cannot
27852 problem in any other manner. So let us examine two ways to reorganize
27853 the program to avoid the potential elaboration problem.
27856 Split library tasks into separate packages.
27858 Write separate packages, so that library tasks are isolated from
27859 other declarations as much as possible. Let us look at a variation on
27862 @smallexample @c ada
27870 package body Decls1 is
27871 task body Lib_Task is
27879 type My_Int is new Integer;
27880 function Ident (M : My_Int) return My_Int;
27884 package body Decls2 is
27885 function Ident (M : My_Int) return My_Int is
27893 procedure Put_Val (Arg : Decls2.My_Int);
27897 package body Utils is
27898 procedure Put_Val (Arg : Decls2.My_Int) is
27900 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
27907 Decls1.Lib_Task.Start;
27912 All we have done is to split @code{Decls} into two packages, one
27913 containing the library task, and one containing everything else. Now
27914 there is no cycle, and the program compiles, binds, links and executes
27915 using the default static model of elaboration.
27918 Declare separate task types.
27920 A significant part of the problem arises because of the use of the
27921 single task declaration form. This means that the elaboration of
27922 the task type, and the elaboration of the task itself (i.e.@: the
27923 creation of the task) happen at the same time. A good rule
27924 of style in Ada is to always create explicit task types. By
27925 following the additional step of placing task objects in separate
27926 packages from the task type declaration, many elaboration problems
27927 are avoided. Here is another modified example of the example program:
27929 @smallexample @c ada
27931 task type Lib_Task_Type is
27935 type My_Int is new Integer;
27937 function Ident (M : My_Int) return My_Int;
27941 package body Decls is
27942 task body Lib_Task_Type is
27948 function Ident (M : My_Int) return My_Int is
27956 procedure Put_Val (Arg : Decls.My_Int);
27960 package body Utils is
27961 procedure Put_Val (Arg : Decls.My_Int) is
27963 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
27969 Lib_Task : Decls.Lib_Task_Type;
27975 Declst.Lib_Task.Start;
27980 What we have done here is to replace the @code{task} declaration in
27981 package @code{Decls} with a @code{task type} declaration. Then we
27982 introduce a separate package @code{Declst} to contain the actual
27983 task object. This separates the elaboration issues for
27984 the @code{task type}
27985 declaration, which causes no trouble, from the elaboration issues
27986 of the task object, which is also unproblematic, since it is now independent
27987 of the elaboration of @code{Utils}.
27988 This separation of concerns also corresponds to
27989 a generally sound engineering principle of separating declarations
27990 from instances. This version of the program also compiles, binds, links,
27991 and executes, generating the expected output.
27994 Use No_Entry_Calls_In_Elaboration_Code restriction.
27995 @cindex No_Entry_Calls_In_Elaboration_Code
27997 The previous two approaches described how a program can be restructured
27998 to avoid the special problems caused by library task bodies. in practice,
27999 however, such restructuring may be difficult to apply to existing legacy code,
28000 so we must consider solutions that do not require massive rewriting.
28002 Let us consider more carefully why our original sample program works
28003 under the dynamic model of elaboration. The reason is that the code
28004 in the task body blocks immediately on the @code{accept}
28005 statement. Now of course there is nothing to prohibit elaboration
28006 code from making entry calls (for example from another library level task),
28007 so we cannot tell in isolation that
28008 the task will not execute the accept statement during elaboration.
28010 However, in practice it is very unusual to see elaboration code
28011 make any entry calls, and the pattern of tasks starting
28012 at elaboration time and then immediately blocking on @code{accept} or
28013 @code{select} statements is very common. What this means is that
28014 the compiler is being too pessimistic when it analyzes the
28015 whole package body as though it might be executed at elaboration
28018 If we know that the elaboration code contains no entry calls, (a very safe
28019 assumption most of the time, that could almost be made the default
28020 behavior), then we can compile all units of the program under control
28021 of the following configuration pragma:
28024 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28028 This pragma can be placed in the @file{gnat.adc} file in the usual
28029 manner. If we take our original unmodified program and compile it
28030 in the presence of a @file{gnat.adc} containing the above pragma,
28031 then once again, we can compile, bind, link, and execute, obtaining
28032 the expected result. In the presence of this pragma, the compiler does
28033 not trace calls in a task body, that appear after the first @code{accept}
28034 or @code{select} statement, and therefore does not report a potential
28035 circularity in the original program.
28037 The compiler will check to the extent it can that the above
28038 restriction is not violated, but it is not always possible to do a
28039 complete check at compile time, so it is important to use this
28040 pragma only if the stated restriction is in fact met, that is to say
28041 no task receives an entry call before elaboration of all units is completed.
28045 @node Mixing Elaboration Models
28046 @section Mixing Elaboration Models
28048 So far, we have assumed that the entire program is either compiled
28049 using the dynamic model or static model, ensuring consistency. It
28050 is possible to mix the two models, but rules have to be followed
28051 if this mixing is done to ensure that elaboration checks are not
28054 The basic rule is that @emph{a unit compiled with the static model cannot
28055 be @code{with'ed} by a unit compiled with the dynamic model}. The
28056 reason for this is that in the static model, a unit assumes that
28057 its clients guarantee to use (the equivalent of) pragma
28058 @code{Elaborate_All} so that no elaboration checks are required
28059 in inner subprograms, and this assumption is violated if the
28060 client is compiled with dynamic checks.
28062 The precise rule is as follows. A unit that is compiled with dynamic
28063 checks can only @code{with} a unit that meets at least one of the
28064 following criteria:
28069 The @code{with'ed} unit is itself compiled with dynamic elaboration
28070 checks (that is with the @option{-gnatE} switch.
28073 The @code{with'ed} unit is an internal GNAT implementation unit from
28074 the System, Interfaces, Ada, or GNAT hierarchies.
28077 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
28080 The @code{with'ing} unit (that is the client) has an explicit pragma
28081 @code{Elaborate_All} for the @code{with'ed} unit.
28086 If this rule is violated, that is if a unit with dynamic elaboration
28087 checks @code{with's} a unit that does not meet one of the above four
28088 criteria, then the binder (@code{gnatbind}) will issue a warning
28089 similar to that in the following example:
28092 warning: "x.ads" has dynamic elaboration checks and with's
28093 warning: "y.ads" which has static elaboration checks
28097 These warnings indicate that the rule has been violated, and that as a result
28098 elaboration checks may be missed in the resulting executable file.
28099 This warning may be suppressed using the @option{-ws} binder switch
28100 in the usual manner.
28102 One useful application of this mixing rule is in the case of a subsystem
28103 which does not itself @code{with} units from the remainder of the
28104 application. In this case, the entire subsystem can be compiled with
28105 dynamic checks to resolve a circularity in the subsystem, while
28106 allowing the main application that uses this subsystem to be compiled
28107 using the more reliable default static model.
28109 @node What to Do If the Default Elaboration Behavior Fails
28110 @section What to Do If the Default Elaboration Behavior Fails
28113 If the binder cannot find an acceptable order, it outputs detailed
28114 diagnostics. For example:
28120 error: elaboration circularity detected
28121 info: "proc (body)" must be elaborated before "pack (body)"
28122 info: reason: Elaborate_All probably needed in unit "pack (body)"
28123 info: recompile "pack (body)" with -gnatwl
28124 info: for full details
28125 info: "proc (body)"
28126 info: is needed by its spec:
28127 info: "proc (spec)"
28128 info: which is withed by:
28129 info: "pack (body)"
28130 info: "pack (body)" must be elaborated before "proc (body)"
28131 info: reason: pragma Elaborate in unit "proc (body)"
28137 In this case we have a cycle that the binder cannot break. On the one
28138 hand, there is an explicit pragma Elaborate in @code{proc} for
28139 @code{pack}. This means that the body of @code{pack} must be elaborated
28140 before the body of @code{proc}. On the other hand, there is elaboration
28141 code in @code{pack} that calls a subprogram in @code{proc}. This means
28142 that for maximum safety, there should really be a pragma
28143 Elaborate_All in @code{pack} for @code{proc} which would require that
28144 the body of @code{proc} be elaborated before the body of
28145 @code{pack}. Clearly both requirements cannot be satisfied.
28146 Faced with a circularity of this kind, you have three different options.
28149 @item Fix the program
28150 The most desirable option from the point of view of long-term maintenance
28151 is to rearrange the program so that the elaboration problems are avoided.
28152 One useful technique is to place the elaboration code into separate
28153 child packages. Another is to move some of the initialization code to
28154 explicitly called subprograms, where the program controls the order
28155 of initialization explicitly. Although this is the most desirable option,
28156 it may be impractical and involve too much modification, especially in
28157 the case of complex legacy code.
28159 @item Perform dynamic checks
28160 If the compilations are done using the
28162 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28163 manner. Dynamic checks are generated for all calls that could possibly result
28164 in raising an exception. With this switch, the compiler does not generate
28165 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28166 exactly as specified in the @cite{Ada Reference Manual}.
28167 The binder will generate
28168 an executable program that may or may not raise @code{Program_Error}, and then
28169 it is the programmer's job to ensure that it does not raise an exception. Note
28170 that it is important to compile all units with the switch, it cannot be used
28173 @item Suppress checks
28174 The drawback of dynamic checks is that they generate a
28175 significant overhead at run time, both in space and time. If you
28176 are absolutely sure that your program cannot raise any elaboration
28177 exceptions, and you still want to use the dynamic elaboration model,
28178 then you can use the configuration pragma
28179 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28180 example this pragma could be placed in the @file{gnat.adc} file.
28182 @item Suppress checks selectively
28183 When you know that certain calls or instantiations in elaboration code cannot
28184 possibly lead to an elaboration error, and the binder nevertheless complains
28185 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28186 elaboration circularities, it is possible to remove those warnings locally and
28187 obtain a program that will bind. Clearly this can be unsafe, and it is the
28188 responsibility of the programmer to make sure that the resulting program has no
28189 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28190 used with different granularity to suppress warnings and break elaboration
28195 Place the pragma that names the called subprogram in the declarative part
28196 that contains the call.
28199 Place the pragma in the declarative part, without naming an entity. This
28200 disables warnings on all calls in the corresponding declarative region.
28203 Place the pragma in the package spec that declares the called subprogram,
28204 and name the subprogram. This disables warnings on all elaboration calls to
28208 Place the pragma in the package spec that declares the called subprogram,
28209 without naming any entity. This disables warnings on all elaboration calls to
28210 all subprograms declared in this spec.
28212 @item Use Pragma Elaborate
28213 As previously described in section @xref{Treatment of Pragma Elaborate},
28214 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28215 that no elaboration checks are required on calls to the designated unit.
28216 There may be cases in which the caller knows that no transitive calls
28217 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28218 case where @code{pragma Elaborate_All} would cause a circularity.
28222 These five cases are listed in order of decreasing safety, and therefore
28223 require increasing programmer care in their application. Consider the
28226 @smallexample @c adanocomment
28228 function F1 return Integer;
28233 function F2 return Integer;
28234 function Pure (x : integer) return integer;
28235 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28236 -- pragma Suppress (Elaboration_Check); -- (4)
28240 package body Pack1 is
28241 function F1 return Integer is
28245 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28248 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28249 -- pragma Suppress(Elaboration_Check); -- (2)
28251 X1 := Pack2.F2 + 1; -- Elab. call (2)
28256 package body Pack2 is
28257 function F2 return Integer is
28261 function Pure (x : integer) return integer is
28263 return x ** 3 - 3 * x;
28267 with Pack1, Ada.Text_IO;
28270 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28273 In the absence of any pragmas, an attempt to bind this program produces
28274 the following diagnostics:
28280 error: elaboration circularity detected
28281 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28282 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28283 info: recompile "pack1 (body)" with -gnatwl for full details
28284 info: "pack1 (body)"
28285 info: must be elaborated along with its spec:
28286 info: "pack1 (spec)"
28287 info: which is withed by:
28288 info: "pack2 (body)"
28289 info: which must be elaborated along with its spec:
28290 info: "pack2 (spec)"
28291 info: which is withed by:
28292 info: "pack1 (body)"
28295 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28296 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28297 F2 is safe, even though F2 calls F1, because the call appears after the
28298 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28299 remove the warning on the call. It is also possible to use pragma (2)
28300 because there are no other potentially unsafe calls in the block.
28303 The call to @code{Pure} is safe because this function does not depend on the
28304 state of @code{Pack2}. Therefore any call to this function is safe, and it
28305 is correct to place pragma (3) in the corresponding package spec.
28308 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28309 warnings on all calls to functions declared therein. Note that this is not
28310 necessarily safe, and requires more detailed examination of the subprogram
28311 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28312 be already elaborated.
28316 It is hard to generalize on which of these four approaches should be
28317 taken. Obviously if it is possible to fix the program so that the default
28318 treatment works, this is preferable, but this may not always be practical.
28319 It is certainly simple enough to use
28321 but the danger in this case is that, even if the GNAT binder
28322 finds a correct elaboration order, it may not always do so,
28323 and certainly a binder from another Ada compiler might not. A
28324 combination of testing and analysis (for which the warnings generated
28327 switch can be useful) must be used to ensure that the program is free
28328 of errors. One switch that is useful in this testing is the
28329 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
28332 Normally the binder tries to find an order that has the best chance
28333 of avoiding elaboration problems. However, if this switch is used, the binder
28334 plays a devil's advocate role, and tries to choose the order that
28335 has the best chance of failing. If your program works even with this
28336 switch, then it has a better chance of being error free, but this is still
28339 For an example of this approach in action, consider the C-tests (executable
28340 tests) from the ACVC suite. If these are compiled and run with the default
28341 treatment, then all but one of them succeed without generating any error
28342 diagnostics from the binder. However, there is one test that fails, and
28343 this is not surprising, because the whole point of this test is to ensure
28344 that the compiler can handle cases where it is impossible to determine
28345 a correct order statically, and it checks that an exception is indeed
28346 raised at run time.
28348 This one test must be compiled and run using the
28350 switch, and then it passes. Alternatively, the entire suite can
28351 be run using this switch. It is never wrong to run with the dynamic
28352 elaboration switch if your code is correct, and we assume that the
28353 C-tests are indeed correct (it is less efficient, but efficiency is
28354 not a factor in running the ACVC tests.)
28356 @node Elaboration for Access-to-Subprogram Values
28357 @section Elaboration for Access-to-Subprogram Values
28358 @cindex Access-to-subprogram
28361 Access-to-subprogram types (introduced in Ada 95) complicate
28362 the handling of elaboration. The trouble is that it becomes
28363 impossible to tell at compile time which procedure
28364 is being called. This means that it is not possible for the binder
28365 to analyze the elaboration requirements in this case.
28367 If at the point at which the access value is created
28368 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
28369 the body of the subprogram is
28370 known to have been elaborated, then the access value is safe, and its use
28371 does not require a check. This may be achieved by appropriate arrangement
28372 of the order of declarations if the subprogram is in the current unit,
28373 or, if the subprogram is in another unit, by using pragma
28374 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
28375 on the referenced unit.
28377 If the referenced body is not known to have been elaborated at the point
28378 the access value is created, then any use of the access value must do a
28379 dynamic check, and this dynamic check will fail and raise a
28380 @code{Program_Error} exception if the body has not been elaborated yet.
28381 GNAT will generate the necessary checks, and in addition, if the
28383 switch is set, will generate warnings that such checks are required.
28385 The use of dynamic dispatching for tagged types similarly generates
28386 a requirement for dynamic checks, and premature calls to any primitive
28387 operation of a tagged type before the body of the operation has been
28388 elaborated, will result in the raising of @code{Program_Error}.
28390 @node Summary of Procedures for Elaboration Control
28391 @section Summary of Procedures for Elaboration Control
28392 @cindex Elaboration control
28395 First, compile your program with the default options, using none of
28396 the special elaboration control switches. If the binder successfully
28397 binds your program, then you can be confident that, apart from issues
28398 raised by the use of access-to-subprogram types and dynamic dispatching,
28399 the program is free of elaboration errors. If it is important that the
28400 program be portable, then use the
28402 switch to generate warnings about missing @code{Elaborate} or
28403 @code{Elaborate_All} pragmas, and supply the missing pragmas.
28405 If the program fails to bind using the default static elaboration
28406 handling, then you can fix the program to eliminate the binder
28407 message, or recompile the entire program with the
28408 @option{-gnatE} switch to generate dynamic elaboration checks,
28409 and, if you are sure there really are no elaboration problems,
28410 use a global pragma @code{Suppress (Elaboration_Check)}.
28412 @node Other Elaboration Order Considerations
28413 @section Other Elaboration Order Considerations
28415 This section has been entirely concerned with the issue of finding a valid
28416 elaboration order, as defined by the Ada Reference Manual. In a case
28417 where several elaboration orders are valid, the task is to find one
28418 of the possible valid elaboration orders (and the static model in GNAT
28419 will ensure that this is achieved).
28421 The purpose of the elaboration rules in the Ada Reference Manual is to
28422 make sure that no entity is accessed before it has been elaborated. For
28423 a subprogram, this means that the spec and body must have been elaborated
28424 before the subprogram is called. For an object, this means that the object
28425 must have been elaborated before its value is read or written. A violation
28426 of either of these two requirements is an access before elaboration order,
28427 and this section has been all about avoiding such errors.
28429 In the case where more than one order of elaboration is possible, in the
28430 sense that access before elaboration errors are avoided, then any one of
28431 the orders is ``correct'' in the sense that it meets the requirements of
28432 the Ada Reference Manual, and no such error occurs.
28434 However, it may be the case for a given program, that there are
28435 constraints on the order of elaboration that come not from consideration
28436 of avoiding elaboration errors, but rather from extra-lingual logic
28437 requirements. Consider this example:
28439 @smallexample @c ada
28440 with Init_Constants;
28441 package Constants is
28446 package Init_Constants is
28447 procedure P; -- require a body
28448 end Init_Constants;
28451 package body Init_Constants is
28452 procedure P is begin null; end;
28456 end Init_Constants;
28460 Z : Integer := Constants.X + Constants.Y;
28464 with Text_IO; use Text_IO;
28467 Put_Line (Calc.Z'Img);
28472 In this example, there is more than one valid order of elaboration. For
28473 example both the following are correct orders:
28476 Init_Constants spec
28479 Init_Constants body
28484 Init_Constants spec
28485 Init_Constants body
28492 There is no language rule to prefer one or the other, both are correct
28493 from an order of elaboration point of view. But the programmatic effects
28494 of the two orders are very different. In the first, the elaboration routine
28495 of @code{Calc} initializes @code{Z} to zero, and then the main program
28496 runs with this value of zero. But in the second order, the elaboration
28497 routine of @code{Calc} runs after the body of Init_Constants has set
28498 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
28501 One could perhaps by applying pretty clever non-artificial intelligence
28502 to the situation guess that it is more likely that the second order of
28503 elaboration is the one desired, but there is no formal linguistic reason
28504 to prefer one over the other. In fact in this particular case, GNAT will
28505 prefer the second order, because of the rule that bodies are elaborated
28506 as soon as possible, but it's just luck that this is what was wanted
28507 (if indeed the second order was preferred).
28509 If the program cares about the order of elaboration routines in a case like
28510 this, it is important to specify the order required. In this particular
28511 case, that could have been achieved by adding to the spec of Calc:
28513 @smallexample @c ada
28514 pragma Elaborate_All (Constants);
28518 which requires that the body (if any) and spec of @code{Constants},
28519 as well as the body and spec of any unit @code{with}'ed by
28520 @code{Constants} be elaborated before @code{Calc} is elaborated.
28522 Clearly no automatic method can always guess which alternative you require,
28523 and if you are working with legacy code that had constraints of this kind
28524 which were not properly specified by adding @code{Elaborate} or
28525 @code{Elaborate_All} pragmas, then indeed it is possible that two different
28526 compilers can choose different orders.
28528 However, GNAT does attempt to diagnose the common situation where there
28529 are uninitialized variables in the visible part of a package spec, and the
28530 corresponding package body has an elaboration block that directly or
28531 indirectly initialized one or more of these variables. This is the situation
28532 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
28533 a warning that suggests this addition if it detects this situation.
28535 The @code{gnatbind}
28536 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
28537 out problems. This switch causes bodies to be elaborated as late as possible
28538 instead of as early as possible. In the example above, it would have forced
28539 the choice of the first elaboration order. If you get different results
28540 when using this switch, and particularly if one set of results is right,
28541 and one is wrong as far as you are concerned, it shows that you have some
28542 missing @code{Elaborate} pragmas. For the example above, we have the
28546 gnatmake -f -q main
28549 gnatmake -f -q main -bargs -p
28555 It is of course quite unlikely that both these results are correct, so
28556 it is up to you in a case like this to investigate the source of the
28557 difference, by looking at the two elaboration orders that are chosen,
28558 and figuring out which is correct, and then adding the necessary
28559 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
28563 @c *******************************
28564 @node Conditional Compilation
28565 @appendix Conditional Compilation
28566 @c *******************************
28567 @cindex Conditional compilation
28570 It is often necessary to arrange for a single source program
28571 to serve multiple purposes, where it is compiled in different
28572 ways to achieve these different goals. Some examples of the
28573 need for this feature are
28576 @item Adapting a program to a different hardware environment
28577 @item Adapting a program to a different target architecture
28578 @item Turning debugging features on and off
28579 @item Arranging for a program to compile with different compilers
28583 In C, or C++, the typical approach would be to use the preprocessor
28584 that is defined as part of the language. The Ada language does not
28585 contain such a feature. This is not an oversight, but rather a very
28586 deliberate design decision, based on the experience that overuse of
28587 the preprocessing features in C and C++ can result in programs that
28588 are extremely difficult to maintain. For example, if we have ten
28589 switches that can be on or off, this means that there are a thousand
28590 separate programs, any one of which might not even be syntactically
28591 correct, and even if syntactically correct, the resulting program
28592 might not work correctly. Testing all combinations can quickly become
28595 Nevertheless, the need to tailor programs certainly exists, and in
28596 this Appendix we will discuss how this can
28597 be achieved using Ada in general, and GNAT in particular.
28600 * Use of Boolean Constants::
28601 * Debugging - A Special Case::
28602 * Conditionalizing Declarations::
28603 * Use of Alternative Implementations::
28607 @node Use of Boolean Constants
28608 @section Use of Boolean Constants
28611 In the case where the difference is simply which code
28612 sequence is executed, the cleanest solution is to use Boolean
28613 constants to control which code is executed.
28615 @smallexample @c ada
28617 FP_Initialize_Required : constant Boolean := True;
28619 if FP_Initialize_Required then
28626 Not only will the code inside the @code{if} statement not be executed if
28627 the constant Boolean is @code{False}, but it will also be completely
28628 deleted from the program.
28629 However, the code is only deleted after the @code{if} statement
28630 has been checked for syntactic and semantic correctness.
28631 (In contrast, with preprocessors the code is deleted before the
28632 compiler ever gets to see it, so it is not checked until the switch
28634 @cindex Preprocessors (contrasted with conditional compilation)
28636 Typically the Boolean constants will be in a separate package,
28639 @smallexample @c ada
28642 FP_Initialize_Required : constant Boolean := True;
28643 Reset_Available : constant Boolean := False;
28650 The @code{Config} package exists in multiple forms for the various targets,
28651 with an appropriate script selecting the version of @code{Config} needed.
28652 Then any other unit requiring conditional compilation can do a @code{with}
28653 of @code{Config} to make the constants visible.
28656 @node Debugging - A Special Case
28657 @section Debugging - A Special Case
28660 A common use of conditional code is to execute statements (for example
28661 dynamic checks, or output of intermediate results) under control of a
28662 debug switch, so that the debugging behavior can be turned on and off.
28663 This can be done using a Boolean constant to control whether the code
28666 @smallexample @c ada
28669 Put_Line ("got to the first stage!");
28677 @smallexample @c ada
28679 if Debugging and then Temperature > 999.0 then
28680 raise Temperature_Crazy;
28686 Since this is a common case, there are special features to deal with
28687 this in a convenient manner. For the case of tests, Ada 2005 has added
28688 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
28689 @cindex pragma @code{Assert}
28690 on the @code{Assert} pragma that has always been available in GNAT, so this
28691 feature may be used with GNAT even if you are not using Ada 2005 features.
28692 The use of pragma @code{Assert} is described in
28693 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
28694 example, the last test could be written:
28696 @smallexample @c ada
28697 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
28703 @smallexample @c ada
28704 pragma Assert (Temperature <= 999.0);
28708 In both cases, if assertions are active and the temperature is excessive,
28709 the exception @code{Assert_Failure} will be raised, with the given string in
28710 the first case or a string indicating the location of the pragma in the second
28711 case used as the exception message.
28713 You can turn assertions on and off by using the @code{Assertion_Policy}
28715 @cindex pragma @code{Assertion_Policy}
28716 This is an Ada 2005 pragma which is implemented in all modes by
28717 GNAT, but only in the latest versions of GNAT which include Ada 2005
28718 capability. Alternatively, you can use the @option{-gnata} switch
28719 @cindex @option{-gnata} switch
28720 to enable assertions from the command line (this is recognized by all versions
28723 For the example above with the @code{Put_Line}, the GNAT-specific pragma
28724 @code{Debug} can be used:
28725 @cindex pragma @code{Debug}
28727 @smallexample @c ada
28728 pragma Debug (Put_Line ("got to the first stage!"));
28732 If debug pragmas are enabled, the argument, which must be of the form of
28733 a procedure call, is executed (in this case, @code{Put_Line} will be called).
28734 Only one call can be present, but of course a special debugging procedure
28735 containing any code you like can be included in the program and then
28736 called in a pragma @code{Debug} argument as needed.
28738 One advantage of pragma @code{Debug} over the @code{if Debugging then}
28739 construct is that pragma @code{Debug} can appear in declarative contexts,
28740 such as at the very beginning of a procedure, before local declarations have
28743 Debug pragmas are enabled using either the @option{-gnata} switch that also
28744 controls assertions, or with a separate Debug_Policy pragma.
28745 @cindex pragma @code{Debug_Policy}
28746 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
28747 in Ada 95 and Ada 83 programs as well), and is analogous to
28748 pragma @code{Assertion_Policy} to control assertions.
28750 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
28751 and thus they can appear in @file{gnat.adc} if you are not using a
28752 project file, or in the file designated to contain configuration pragmas
28754 They then apply to all subsequent compilations. In practice the use of
28755 the @option{-gnata} switch is often the most convenient method of controlling
28756 the status of these pragmas.
28758 Note that a pragma is not a statement, so in contexts where a statement
28759 sequence is required, you can't just write a pragma on its own. You have
28760 to add a @code{null} statement.
28762 @smallexample @c ada
28765 @dots{} -- some statements
28767 pragma Assert (Num_Cases < 10);
28774 @node Conditionalizing Declarations
28775 @section Conditionalizing Declarations
28778 In some cases, it may be necessary to conditionalize declarations to meet
28779 different requirements. For example we might want a bit string whose length
28780 is set to meet some hardware message requirement.
28782 In some cases, it may be possible to do this using declare blocks controlled
28783 by conditional constants:
28785 @smallexample @c ada
28787 if Small_Machine then
28789 X : Bit_String (1 .. 10);
28795 X : Large_Bit_String (1 .. 1000);
28804 Note that in this approach, both declarations are analyzed by the
28805 compiler so this can only be used where both declarations are legal,
28806 even though one of them will not be used.
28808 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
28809 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
28810 that are parameterized by these constants. For example
28812 @smallexample @c ada
28815 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
28821 If @code{Bits_Per_Word} is set to 32, this generates either
28823 @smallexample @c ada
28826 Field1 at 0 range 0 .. 32;
28832 for the big endian case, or
28834 @smallexample @c ada
28837 Field1 at 0 range 10 .. 32;
28843 for the little endian case. Since a powerful subset of Ada expression
28844 notation is usable for creating static constants, clever use of this
28845 feature can often solve quite difficult problems in conditionalizing
28846 compilation (note incidentally that in Ada 95, the little endian
28847 constant was introduced as @code{System.Default_Bit_Order}, so you do not
28848 need to define this one yourself).
28851 @node Use of Alternative Implementations
28852 @section Use of Alternative Implementations
28855 In some cases, none of the approaches described above are adequate. This
28856 can occur for example if the set of declarations required is radically
28857 different for two different configurations.
28859 In this situation, the official Ada way of dealing with conditionalizing
28860 such code is to write separate units for the different cases. As long as
28861 this does not result in excessive duplication of code, this can be done
28862 without creating maintenance problems. The approach is to share common
28863 code as far as possible, and then isolate the code and declarations
28864 that are different. Subunits are often a convenient method for breaking
28865 out a piece of a unit that is to be conditionalized, with separate files
28866 for different versions of the subunit for different targets, where the
28867 build script selects the right one to give to the compiler.
28868 @cindex Subunits (and conditional compilation)
28870 As an example, consider a situation where a new feature in Ada 2005
28871 allows something to be done in a really nice way. But your code must be able
28872 to compile with an Ada 95 compiler. Conceptually you want to say:
28874 @smallexample @c ada
28877 @dots{} neat Ada 2005 code
28879 @dots{} not quite as neat Ada 95 code
28885 where @code{Ada_2005} is a Boolean constant.
28887 But this won't work when @code{Ada_2005} is set to @code{False},
28888 since the @code{then} clause will be illegal for an Ada 95 compiler.
28889 (Recall that although such unreachable code would eventually be deleted
28890 by the compiler, it still needs to be legal. If it uses features
28891 introduced in Ada 2005, it will be illegal in Ada 95.)
28893 So instead we write
28895 @smallexample @c ada
28896 procedure Insert is separate;
28900 Then we have two files for the subunit @code{Insert}, with the two sets of
28902 If the package containing this is called @code{File_Queries}, then we might
28906 @item @file{file_queries-insert-2005.adb}
28907 @item @file{file_queries-insert-95.adb}
28911 and the build script renames the appropriate file to
28914 file_queries-insert.adb
28918 and then carries out the compilation.
28920 This can also be done with project files' naming schemes. For example:
28922 @smallexample @c project
28923 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
28927 Note also that with project files it is desirable to use a different extension
28928 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
28929 conflict may arise through another commonly used feature: to declare as part
28930 of the project a set of directories containing all the sources obeying the
28931 default naming scheme.
28933 The use of alternative units is certainly feasible in all situations,
28934 and for example the Ada part of the GNAT run-time is conditionalized
28935 based on the target architecture using this approach. As a specific example,
28936 consider the implementation of the AST feature in VMS. There is one
28944 which is the same for all architectures, and three bodies:
28948 used for all non-VMS operating systems
28949 @item s-asthan-vms-alpha.adb
28950 used for VMS on the Alpha
28951 @item s-asthan-vms-ia64.adb
28952 used for VMS on the ia64
28956 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
28957 this operating system feature is not available, and the two remaining
28958 versions interface with the corresponding versions of VMS to provide
28959 VMS-compatible AST handling. The GNAT build script knows the architecture
28960 and operating system, and automatically selects the right version,
28961 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
28963 Another style for arranging alternative implementations is through Ada's
28964 access-to-subprogram facility.
28965 In case some functionality is to be conditionally included,
28966 you can declare an access-to-procedure variable @code{Ref} that is initialized
28967 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
28969 In some library package, set @code{Ref} to @code{Proc'Access} for some
28970 procedure @code{Proc} that performs the relevant processing.
28971 The initialization only occurs if the library package is included in the
28973 The same idea can also be implemented using tagged types and dispatching
28977 @node Preprocessing
28978 @section Preprocessing
28979 @cindex Preprocessing
28982 Although it is quite possible to conditionalize code without the use of
28983 C-style preprocessing, as described earlier in this section, it is
28984 nevertheless convenient in some cases to use the C approach. Moreover,
28985 older Ada compilers have often provided some preprocessing capability,
28986 so legacy code may depend on this approach, even though it is not
28989 To accommodate such use, GNAT provides a preprocessor (modeled to a large
28990 extent on the various preprocessors that have been used
28991 with legacy code on other compilers, to enable easier transition).
28993 The preprocessor may be used in two separate modes. It can be used quite
28994 separately from the compiler, to generate a separate output source file
28995 that is then fed to the compiler as a separate step. This is the
28996 @code{gnatprep} utility, whose use is fully described in
28997 @ref{Preprocessing Using gnatprep}.
28998 @cindex @code{gnatprep}
29000 The preprocessing language allows such constructs as
29004 #if DEBUG or PRIORITY > 4 then
29005 bunch of declarations
29007 completely different bunch of declarations
29013 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29014 defined either on the command line or in a separate file.
29016 The other way of running the preprocessor is even closer to the C style and
29017 often more convenient. In this approach the preprocessing is integrated into
29018 the compilation process. The compiler is fed the preprocessor input which
29019 includes @code{#if} lines etc, and then the compiler carries out the
29020 preprocessing internally and processes the resulting output.
29021 For more details on this approach, see @ref{Integrated Preprocessing}.
29024 @c *******************************
29025 @node Inline Assembler
29026 @appendix Inline Assembler
29027 @c *******************************
29030 If you need to write low-level software that interacts directly
29031 with the hardware, Ada provides two ways to incorporate assembly
29032 language code into your program. First, you can import and invoke
29033 external routines written in assembly language, an Ada feature fully
29034 supported by GNAT@. However, for small sections of code it may be simpler
29035 or more efficient to include assembly language statements directly
29036 in your Ada source program, using the facilities of the implementation-defined
29037 package @code{System.Machine_Code}, which incorporates the gcc
29038 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29039 including the following:
29042 @item No need to use non-Ada tools
29043 @item Consistent interface over different targets
29044 @item Automatic usage of the proper calling conventions
29045 @item Access to Ada constants and variables
29046 @item Definition of intrinsic routines
29047 @item Possibility of inlining a subprogram comprising assembler code
29048 @item Code optimizer can take Inline Assembler code into account
29051 This chapter presents a series of examples to show you how to use
29052 the Inline Assembler. Although it focuses on the Intel x86,
29053 the general approach applies also to other processors.
29054 It is assumed that you are familiar with Ada
29055 and with assembly language programming.
29058 * Basic Assembler Syntax::
29059 * A Simple Example of Inline Assembler::
29060 * Output Variables in Inline Assembler::
29061 * Input Variables in Inline Assembler::
29062 * Inlining Inline Assembler Code::
29063 * Other Asm Functionality::
29066 @c ---------------------------------------------------------------------------
29067 @node Basic Assembler Syntax
29068 @section Basic Assembler Syntax
29071 The assembler used by GNAT and gcc is based not on the Intel assembly
29072 language, but rather on a language that descends from the AT&T Unix
29073 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
29074 The following table summarizes the main features of @emph{as} syntax
29075 and points out the differences from the Intel conventions.
29076 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
29077 pre-processor) documentation for further information.
29080 @item Register names
29081 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
29083 Intel: No extra punctuation; for example @code{eax}
29085 @item Immediate operand
29086 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29088 Intel: No extra punctuation; for example @code{4}
29091 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29093 Intel: No extra punctuation; for example @code{loc}
29095 @item Memory contents
29096 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29098 Intel: Square brackets; for example @code{[loc]}
29100 @item Register contents
29101 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29103 Intel: Square brackets; for example @code{[eax]}
29105 @item Hexadecimal numbers
29106 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29108 Intel: Trailing ``h''; for example @code{A0h}
29111 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29114 Intel: Implicit, deduced by assembler; for example @code{mov}
29116 @item Instruction repetition
29117 gcc / @emph{as}: Split into two lines; for example
29123 Intel: Keep on one line; for example @code{rep stosl}
29125 @item Order of operands
29126 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29128 Intel: Destination first; for example @code{mov eax, 4}
29131 @c ---------------------------------------------------------------------------
29132 @node A Simple Example of Inline Assembler
29133 @section A Simple Example of Inline Assembler
29136 The following example will generate a single assembly language statement,
29137 @code{nop}, which does nothing. Despite its lack of run-time effect,
29138 the example will be useful in illustrating the basics of
29139 the Inline Assembler facility.
29141 @smallexample @c ada
29143 with System.Machine_Code; use System.Machine_Code;
29144 procedure Nothing is
29151 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29152 here it takes one parameter, a @emph{template string} that must be a static
29153 expression and that will form the generated instruction.
29154 @code{Asm} may be regarded as a compile-time procedure that parses
29155 the template string and additional parameters (none here),
29156 from which it generates a sequence of assembly language instructions.
29158 The examples in this chapter will illustrate several of the forms
29159 for invoking @code{Asm}; a complete specification of the syntax
29160 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29163 Under the standard GNAT conventions, the @code{Nothing} procedure
29164 should be in a file named @file{nothing.adb}.
29165 You can build the executable in the usual way:
29169 However, the interesting aspect of this example is not its run-time behavior
29170 but rather the generated assembly code.
29171 To see this output, invoke the compiler as follows:
29173 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29175 where the options are:
29179 compile only (no bind or link)
29181 generate assembler listing
29182 @item -fomit-frame-pointer
29183 do not set up separate stack frames
29185 do not add runtime checks
29188 This gives a human-readable assembler version of the code. The resulting
29189 file will have the same name as the Ada source file, but with a @code{.s}
29190 extension. In our example, the file @file{nothing.s} has the following
29195 .file "nothing.adb"
29197 ___gnu_compiled_ada:
29200 .globl __ada_nothing
29212 The assembly code you included is clearly indicated by
29213 the compiler, between the @code{#APP} and @code{#NO_APP}
29214 delimiters. The character before the 'APP' and 'NOAPP'
29215 can differ on different targets. For example, GNU/Linux uses '#APP' while
29216 on NT you will see '/APP'.
29218 If you make a mistake in your assembler code (such as using the
29219 wrong size modifier, or using a wrong operand for the instruction) GNAT
29220 will report this error in a temporary file, which will be deleted when
29221 the compilation is finished. Generating an assembler file will help
29222 in such cases, since you can assemble this file separately using the
29223 @emph{as} assembler that comes with gcc.
29225 Assembling the file using the command
29228 as @file{nothing.s}
29231 will give you error messages whose lines correspond to the assembler
29232 input file, so you can easily find and correct any mistakes you made.
29233 If there are no errors, @emph{as} will generate an object file
29234 @file{nothing.out}.
29236 @c ---------------------------------------------------------------------------
29237 @node Output Variables in Inline Assembler
29238 @section Output Variables in Inline Assembler
29241 The examples in this section, showing how to access the processor flags,
29242 illustrate how to specify the destination operands for assembly language
29245 @smallexample @c ada
29247 with Interfaces; use Interfaces;
29248 with Ada.Text_IO; use Ada.Text_IO;
29249 with System.Machine_Code; use System.Machine_Code;
29250 procedure Get_Flags is
29251 Flags : Unsigned_32;
29254 Asm ("pushfl" & LF & HT & -- push flags on stack
29255 "popl %%eax" & LF & HT & -- load eax with flags
29256 "movl %%eax, %0", -- store flags in variable
29257 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29258 Put_Line ("Flags register:" & Flags'Img);
29263 In order to have a nicely aligned assembly listing, we have separated
29264 multiple assembler statements in the Asm template string with linefeed
29265 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29266 The resulting section of the assembly output file is:
29273 movl %eax, -40(%ebp)
29278 It would have been legal to write the Asm invocation as:
29281 Asm ("pushfl popl %%eax movl %%eax, %0")
29284 but in the generated assembler file, this would come out as:
29288 pushfl popl %eax movl %eax, -40(%ebp)
29292 which is not so convenient for the human reader.
29294 We use Ada comments
29295 at the end of each line to explain what the assembler instructions
29296 actually do. This is a useful convention.
29298 When writing Inline Assembler instructions, you need to precede each register
29299 and variable name with a percent sign. Since the assembler already requires
29300 a percent sign at the beginning of a register name, you need two consecutive
29301 percent signs for such names in the Asm template string, thus @code{%%eax}.
29302 In the generated assembly code, one of the percent signs will be stripped off.
29304 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29305 variables: operands you later define using @code{Input} or @code{Output}
29306 parameters to @code{Asm}.
29307 An output variable is illustrated in
29308 the third statement in the Asm template string:
29312 The intent is to store the contents of the eax register in a variable that can
29313 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29314 necessarily work, since the compiler might optimize by using a register
29315 to hold Flags, and the expansion of the @code{movl} instruction would not be
29316 aware of this optimization. The solution is not to store the result directly
29317 but rather to advise the compiler to choose the correct operand form;
29318 that is the purpose of the @code{%0} output variable.
29320 Information about the output variable is supplied in the @code{Outputs}
29321 parameter to @code{Asm}:
29323 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29326 The output is defined by the @code{Asm_Output} attribute of the target type;
29327 the general format is
29329 Type'Asm_Output (constraint_string, variable_name)
29332 The constraint string directs the compiler how
29333 to store/access the associated variable. In the example
29335 Unsigned_32'Asm_Output ("=m", Flags);
29337 the @code{"m"} (memory) constraint tells the compiler that the variable
29338 @code{Flags} should be stored in a memory variable, thus preventing
29339 the optimizer from keeping it in a register. In contrast,
29341 Unsigned_32'Asm_Output ("=r", Flags);
29343 uses the @code{"r"} (register) constraint, telling the compiler to
29344 store the variable in a register.
29346 If the constraint is preceded by the equal character (@strong{=}), it tells
29347 the compiler that the variable will be used to store data into it.
29349 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29350 allowing the optimizer to choose whatever it deems best.
29352 There are a fairly large number of constraints, but the ones that are
29353 most useful (for the Intel x86 processor) are the following:
29359 global (i.e.@: can be stored anywhere)
29377 use one of eax, ebx, ecx or edx
29379 use one of eax, ebx, ecx, edx, esi or edi
29382 The full set of constraints is described in the gcc and @emph{as}
29383 documentation; note that it is possible to combine certain constraints
29384 in one constraint string.
29386 You specify the association of an output variable with an assembler operand
29387 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
29389 @smallexample @c ada
29391 Asm ("pushfl" & LF & HT & -- push flags on stack
29392 "popl %%eax" & LF & HT & -- load eax with flags
29393 "movl %%eax, %0", -- store flags in variable
29394 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29398 @code{%0} will be replaced in the expanded code by the appropriate operand,
29400 the compiler decided for the @code{Flags} variable.
29402 In general, you may have any number of output variables:
29405 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29407 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29408 of @code{Asm_Output} attributes
29412 @smallexample @c ada
29414 Asm ("movl %%eax, %0" & LF & HT &
29415 "movl %%ebx, %1" & LF & HT &
29417 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29418 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29419 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29423 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29424 in the Ada program.
29426 As a variation on the @code{Get_Flags} example, we can use the constraints
29427 string to direct the compiler to store the eax register into the @code{Flags}
29428 variable, instead of including the store instruction explicitly in the
29429 @code{Asm} template string:
29431 @smallexample @c ada
29433 with Interfaces; use Interfaces;
29434 with Ada.Text_IO; use Ada.Text_IO;
29435 with System.Machine_Code; use System.Machine_Code;
29436 procedure Get_Flags_2 is
29437 Flags : Unsigned_32;
29440 Asm ("pushfl" & LF & HT & -- push flags on stack
29441 "popl %%eax", -- save flags in eax
29442 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29443 Put_Line ("Flags register:" & Flags'Img);
29449 The @code{"a"} constraint tells the compiler that the @code{Flags}
29450 variable will come from the eax register. Here is the resulting code:
29458 movl %eax,-40(%ebp)
29463 The compiler generated the store of eax into Flags after
29464 expanding the assembler code.
29466 Actually, there was no need to pop the flags into the eax register;
29467 more simply, we could just pop the flags directly into the program variable:
29469 @smallexample @c ada
29471 with Interfaces; use Interfaces;
29472 with Ada.Text_IO; use Ada.Text_IO;
29473 with System.Machine_Code; use System.Machine_Code;
29474 procedure Get_Flags_3 is
29475 Flags : Unsigned_32;
29478 Asm ("pushfl" & LF & HT & -- push flags on stack
29479 "pop %0", -- save flags in Flags
29480 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29481 Put_Line ("Flags register:" & Flags'Img);
29486 @c ---------------------------------------------------------------------------
29487 @node Input Variables in Inline Assembler
29488 @section Input Variables in Inline Assembler
29491 The example in this section illustrates how to specify the source operands
29492 for assembly language statements.
29493 The program simply increments its input value by 1:
29495 @smallexample @c ada
29497 with Interfaces; use Interfaces;
29498 with Ada.Text_IO; use Ada.Text_IO;
29499 with System.Machine_Code; use System.Machine_Code;
29500 procedure Increment is
29502 function Incr (Value : Unsigned_32) return Unsigned_32 is
29503 Result : Unsigned_32;
29506 Inputs => Unsigned_32'Asm_Input ("a", Value),
29507 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29511 Value : Unsigned_32;
29515 Put_Line ("Value before is" & Value'Img);
29516 Value := Incr (Value);
29517 Put_Line ("Value after is" & Value'Img);
29522 The @code{Outputs} parameter to @code{Asm} specifies
29523 that the result will be in the eax register and that it is to be stored
29524 in the @code{Result} variable.
29526 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29527 but with an @code{Asm_Input} attribute.
29528 The @code{"="} constraint, indicating an output value, is not present.
29530 You can have multiple input variables, in the same way that you can have more
29531 than one output variable.
29533 The parameter count (%0, %1) etc, now starts at the first input
29534 statement, and continues with the output statements.
29535 When both parameters use the same variable, the
29536 compiler will treat them as the same %n operand, which is the case here.
29538 Just as the @code{Outputs} parameter causes the register to be stored into the
29539 target variable after execution of the assembler statements, so does the
29540 @code{Inputs} parameter cause its variable to be loaded into the register
29541 before execution of the assembler statements.
29543 Thus the effect of the @code{Asm} invocation is:
29545 @item load the 32-bit value of @code{Value} into eax
29546 @item execute the @code{incl %eax} instruction
29547 @item store the contents of eax into the @code{Result} variable
29550 The resulting assembler file (with @option{-O2} optimization) contains:
29553 _increment__incr.1:
29566 @c ---------------------------------------------------------------------------
29567 @node Inlining Inline Assembler Code
29568 @section Inlining Inline Assembler Code
29571 For a short subprogram such as the @code{Incr} function in the previous
29572 section, the overhead of the call and return (creating / deleting the stack
29573 frame) can be significant, compared to the amount of code in the subprogram
29574 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29575 which directs the compiler to expand invocations of the subprogram at the
29576 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29577 Here is the resulting program:
29579 @smallexample @c ada
29581 with Interfaces; use Interfaces;
29582 with Ada.Text_IO; use Ada.Text_IO;
29583 with System.Machine_Code; use System.Machine_Code;
29584 procedure Increment_2 is
29586 function Incr (Value : Unsigned_32) return Unsigned_32 is
29587 Result : Unsigned_32;
29590 Inputs => Unsigned_32'Asm_Input ("a", Value),
29591 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29594 pragma Inline (Increment);
29596 Value : Unsigned_32;
29600 Put_Line ("Value before is" & Value'Img);
29601 Value := Increment (Value);
29602 Put_Line ("Value after is" & Value'Img);
29607 Compile the program with both optimization (@option{-O2}) and inlining
29608 (@option{-gnatn}) enabled.
29610 The @code{Incr} function is still compiled as usual, but at the
29611 point in @code{Increment} where our function used to be called:
29616 call _increment__incr.1
29621 the code for the function body directly appears:
29634 thus saving the overhead of stack frame setup and an out-of-line call.
29636 @c ---------------------------------------------------------------------------
29637 @node Other Asm Functionality
29638 @section Other @code{Asm} Functionality
29641 This section describes two important parameters to the @code{Asm}
29642 procedure: @code{Clobber}, which identifies register usage;
29643 and @code{Volatile}, which inhibits unwanted optimizations.
29646 * The Clobber Parameter::
29647 * The Volatile Parameter::
29650 @c ---------------------------------------------------------------------------
29651 @node The Clobber Parameter
29652 @subsection The @code{Clobber} Parameter
29655 One of the dangers of intermixing assembly language and a compiled language
29656 such as Ada is that the compiler needs to be aware of which registers are
29657 being used by the assembly code. In some cases, such as the earlier examples,
29658 the constraint string is sufficient to indicate register usage (e.g.,
29660 the eax register). But more generally, the compiler needs an explicit
29661 identification of the registers that are used by the Inline Assembly
29664 Using a register that the compiler doesn't know about
29665 could be a side effect of an instruction (like @code{mull}
29666 storing its result in both eax and edx).
29667 It can also arise from explicit register usage in your
29668 assembly code; for example:
29671 Asm ("movl %0, %%ebx" & LF & HT &
29673 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29674 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
29678 where the compiler (since it does not analyze the @code{Asm} template string)
29679 does not know you are using the ebx register.
29681 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
29682 to identify the registers that will be used by your assembly code:
29686 Asm ("movl %0, %%ebx" & LF & HT &
29688 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29689 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29694 The Clobber parameter is a static string expression specifying the
29695 register(s) you are using. Note that register names are @emph{not} prefixed
29696 by a percent sign. Also, if more than one register is used then their names
29697 are separated by commas; e.g., @code{"eax, ebx"}
29699 The @code{Clobber} parameter has several additional uses:
29701 @item Use ``register'' name @code{cc} to indicate that flags might have changed
29702 @item Use ``register'' name @code{memory} if you changed a memory location
29705 @c ---------------------------------------------------------------------------
29706 @node The Volatile Parameter
29707 @subsection The @code{Volatile} Parameter
29708 @cindex Volatile parameter
29711 Compiler optimizations in the presence of Inline Assembler may sometimes have
29712 unwanted effects. For example, when an @code{Asm} invocation with an input
29713 variable is inside a loop, the compiler might move the loading of the input
29714 variable outside the loop, regarding it as a one-time initialization.
29716 If this effect is not desired, you can disable such optimizations by setting
29717 the @code{Volatile} parameter to @code{True}; for example:
29719 @smallexample @c ada
29721 Asm ("movl %0, %%ebx" & LF & HT &
29723 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29724 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29730 By default, @code{Volatile} is set to @code{False} unless there is no
29731 @code{Outputs} parameter.
29733 Although setting @code{Volatile} to @code{True} prevents unwanted
29734 optimizations, it will also disable other optimizations that might be
29735 important for efficiency. In general, you should set @code{Volatile}
29736 to @code{True} only if the compiler's optimizations have created
29738 @c END OF INLINE ASSEMBLER CHAPTER
29739 @c ===============================
29741 @c ***********************************
29742 @c * Compatibility and Porting Guide *
29743 @c ***********************************
29744 @node Compatibility and Porting Guide
29745 @appendix Compatibility and Porting Guide
29748 This chapter describes the compatibility issues that may arise between
29749 GNAT and other Ada compilation systems (including those for Ada 83),
29750 and shows how GNAT can expedite porting
29751 applications developed in other Ada environments.
29754 * Compatibility with Ada 83::
29755 * Compatibility between Ada 95 and Ada 2005::
29756 * Implementation-dependent characteristics::
29757 * Compatibility with Other Ada Systems::
29758 * Representation Clauses::
29760 @c Brief section is only in non-VMS version
29761 @c Full chapter is in VMS version
29762 * Compatibility with HP Ada 83::
29765 * Transitioning to 64-Bit GNAT for OpenVMS::
29769 @node Compatibility with Ada 83
29770 @section Compatibility with Ada 83
29771 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
29774 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
29775 particular, the design intention was that the difficulties associated
29776 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
29777 that occur when moving from one Ada 83 system to another.
29779 However, there are a number of points at which there are minor
29780 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
29781 full details of these issues,
29782 and should be consulted for a complete treatment.
29784 following subsections treat the most likely issues to be encountered.
29787 * Legal Ada 83 programs that are illegal in Ada 95::
29788 * More deterministic semantics::
29789 * Changed semantics::
29790 * Other language compatibility issues::
29793 @node Legal Ada 83 programs that are illegal in Ada 95
29794 @subsection Legal Ada 83 programs that are illegal in Ada 95
29796 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
29797 Ada 95 and thus also in Ada 2005:
29800 @item Character literals
29801 Some uses of character literals are ambiguous. Since Ada 95 has introduced
29802 @code{Wide_Character} as a new predefined character type, some uses of
29803 character literals that were legal in Ada 83 are illegal in Ada 95.
29805 @smallexample @c ada
29806 for Char in 'A' .. 'Z' loop @dots{} end loop;
29810 The problem is that @code{'A'} and @code{'Z'} could be from either
29811 @code{Character} or @code{Wide_Character}. The simplest correction
29812 is to make the type explicit; e.g.:
29813 @smallexample @c ada
29814 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
29817 @item New reserved words
29818 The identifiers @code{abstract}, @code{aliased}, @code{protected},
29819 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
29820 Existing Ada 83 code using any of these identifiers must be edited to
29821 use some alternative name.
29823 @item Freezing rules
29824 The rules in Ada 95 are slightly different with regard to the point at
29825 which entities are frozen, and representation pragmas and clauses are
29826 not permitted past the freeze point. This shows up most typically in
29827 the form of an error message complaining that a representation item
29828 appears too late, and the appropriate corrective action is to move
29829 the item nearer to the declaration of the entity to which it refers.
29831 A particular case is that representation pragmas
29834 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
29836 cannot be applied to a subprogram body. If necessary, a separate subprogram
29837 declaration must be introduced to which the pragma can be applied.
29839 @item Optional bodies for library packages
29840 In Ada 83, a package that did not require a package body was nevertheless
29841 allowed to have one. This lead to certain surprises in compiling large
29842 systems (situations in which the body could be unexpectedly ignored by the
29843 binder). In Ada 95, if a package does not require a body then it is not
29844 permitted to have a body. To fix this problem, simply remove a redundant
29845 body if it is empty, or, if it is non-empty, introduce a dummy declaration
29846 into the spec that makes the body required. One approach is to add a private
29847 part to the package declaration (if necessary), and define a parameterless
29848 procedure called @code{Requires_Body}, which must then be given a dummy
29849 procedure body in the package body, which then becomes required.
29850 Another approach (assuming that this does not introduce elaboration
29851 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
29852 since one effect of this pragma is to require the presence of a package body.
29854 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
29855 In Ada 95, the exception @code{Numeric_Error} is a renaming of
29856 @code{Constraint_Error}.
29857 This means that it is illegal to have separate exception handlers for
29858 the two exceptions. The fix is simply to remove the handler for the
29859 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
29860 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
29862 @item Indefinite subtypes in generics
29863 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
29864 as the actual for a generic formal private type, but then the instantiation
29865 would be illegal if there were any instances of declarations of variables
29866 of this type in the generic body. In Ada 95, to avoid this clear violation
29867 of the methodological principle known as the ``contract model'',
29868 the generic declaration explicitly indicates whether
29869 or not such instantiations are permitted. If a generic formal parameter
29870 has explicit unknown discriminants, indicated by using @code{(<>)} after the
29871 type name, then it can be instantiated with indefinite types, but no
29872 stand-alone variables can be declared of this type. Any attempt to declare
29873 such a variable will result in an illegality at the time the generic is
29874 declared. If the @code{(<>)} notation is not used, then it is illegal
29875 to instantiate the generic with an indefinite type.
29876 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
29877 It will show up as a compile time error, and
29878 the fix is usually simply to add the @code{(<>)} to the generic declaration.
29881 @node More deterministic semantics
29882 @subsection More deterministic semantics
29886 Conversions from real types to integer types round away from 0. In Ada 83
29887 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
29888 implementation freedom was intended to support unbiased rounding in
29889 statistical applications, but in practice it interfered with portability.
29890 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
29891 is required. Numeric code may be affected by this change in semantics.
29892 Note, though, that this issue is no worse than already existed in Ada 83
29893 when porting code from one vendor to another.
29896 The Real-Time Annex introduces a set of policies that define the behavior of
29897 features that were implementation dependent in Ada 83, such as the order in
29898 which open select branches are executed.
29901 @node Changed semantics
29902 @subsection Changed semantics
29905 The worst kind of incompatibility is one where a program that is legal in
29906 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
29907 possible in Ada 83. Fortunately this is extremely rare, but the one
29908 situation that you should be alert to is the change in the predefined type
29909 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
29912 @item Range of type @code{Character}
29913 The range of @code{Standard.Character} is now the full 256 characters
29914 of Latin-1, whereas in most Ada 83 implementations it was restricted
29915 to 128 characters. Although some of the effects of
29916 this change will be manifest in compile-time rejection of legal
29917 Ada 83 programs it is possible for a working Ada 83 program to have
29918 a different effect in Ada 95, one that was not permitted in Ada 83.
29919 As an example, the expression
29920 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
29921 delivers @code{255} as its value.
29922 In general, you should look at the logic of any
29923 character-processing Ada 83 program and see whether it needs to be adapted
29924 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
29925 character handling package that may be relevant if code needs to be adapted
29926 to account for the additional Latin-1 elements.
29927 The desirable fix is to
29928 modify the program to accommodate the full character set, but in some cases
29929 it may be convenient to define a subtype or derived type of Character that
29930 covers only the restricted range.
29934 @node Other language compatibility issues
29935 @subsection Other language compatibility issues
29938 @item @option{-gnat83} switch
29939 All implementations of GNAT provide a switch that causes GNAT to operate
29940 in Ada 83 mode. In this mode, some but not all compatibility problems
29941 of the type described above are handled automatically. For example, the
29942 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
29943 as identifiers as in Ada 83.
29945 in practice, it is usually advisable to make the necessary modifications
29946 to the program to remove the need for using this switch.
29947 See @ref{Compiling Different Versions of Ada}.
29949 @item Support for removed Ada 83 pragmas and attributes
29950 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
29951 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
29952 compilers are allowed, but not required, to implement these missing
29953 elements. In contrast with some other compilers, GNAT implements all
29954 such pragmas and attributes, eliminating this compatibility concern. These
29955 include @code{pragma Interface} and the floating point type attributes
29956 (@code{Emax}, @code{Mantissa}, etc.), among other items.
29960 @node Compatibility between Ada 95 and Ada 2005
29961 @section Compatibility between Ada 95 and Ada 2005
29962 @cindex Compatibility between Ada 95 and Ada 2005
29965 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
29966 a number of incompatibilities. Several are enumerated below;
29967 for a complete description please see the
29968 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
29969 @cite{Rationale for Ada 2005}.
29972 @item New reserved words.
29973 The words @code{interface}, @code{overriding} and @code{synchronized} are
29974 reserved in Ada 2005.
29975 A pre-Ada 2005 program that uses any of these as an identifier will be
29978 @item New declarations in predefined packages.
29979 A number of packages in the predefined environment contain new declarations:
29980 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
29981 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
29982 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
29983 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
29984 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
29985 If an Ada 95 program does a @code{with} and @code{use} of any of these
29986 packages, the new declarations may cause name clashes.
29988 @item Access parameters.
29989 A nondispatching subprogram with an access parameter cannot be renamed
29990 as a dispatching operation. This was permitted in Ada 95.
29992 @item Access types, discriminants, and constraints.
29993 Rule changes in this area have led to some incompatibilities; for example,
29994 constrained subtypes of some access types are not permitted in Ada 2005.
29996 @item Aggregates for limited types.
29997 The allowance of aggregates for limited types in Ada 2005 raises the
29998 possibility of ambiguities in legal Ada 95 programs, since additional types
29999 now need to be considered in expression resolution.
30001 @item Fixed-point multiplication and division.
30002 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30003 were legal in Ada 95 and invoked the predefined versions of these operations,
30005 The ambiguity may be resolved either by applying a type conversion to the
30006 expression, or by explicitly invoking the operation from package
30009 @item Return-by-reference types.
30010 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30011 can declare a function returning a value from an anonymous access type.
30015 @node Implementation-dependent characteristics
30016 @section Implementation-dependent characteristics
30018 Although the Ada language defines the semantics of each construct as
30019 precisely as practical, in some situations (for example for reasons of
30020 efficiency, or where the effect is heavily dependent on the host or target
30021 platform) the implementation is allowed some freedom. In porting Ada 83
30022 code to GNAT, you need to be aware of whether / how the existing code
30023 exercised such implementation dependencies. Such characteristics fall into
30024 several categories, and GNAT offers specific support in assisting the
30025 transition from certain Ada 83 compilers.
30028 * Implementation-defined pragmas::
30029 * Implementation-defined attributes::
30031 * Elaboration order::
30032 * Target-specific aspects::
30035 @node Implementation-defined pragmas
30036 @subsection Implementation-defined pragmas
30039 Ada compilers are allowed to supplement the language-defined pragmas, and
30040 these are a potential source of non-portability. All GNAT-defined pragmas
30041 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
30042 Reference Manual}, and these include several that are specifically
30043 intended to correspond to other vendors' Ada 83 pragmas.
30044 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
30045 For compatibility with HP Ada 83, GNAT supplies the pragmas
30046 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
30047 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
30048 and @code{Volatile}.
30049 Other relevant pragmas include @code{External} and @code{Link_With}.
30050 Some vendor-specific
30051 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
30053 avoiding compiler rejection of units that contain such pragmas; they are not
30054 relevant in a GNAT context and hence are not otherwise implemented.
30056 @node Implementation-defined attributes
30057 @subsection Implementation-defined attributes
30059 Analogous to pragmas, the set of attributes may be extended by an
30060 implementation. All GNAT-defined attributes are described in
30061 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
30062 Manual}, and these include several that are specifically intended
30063 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
30064 the attribute @code{VADS_Size} may be useful. For compatibility with HP
30065 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
30069 @subsection Libraries
30071 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
30072 code uses vendor-specific libraries then there are several ways to manage
30073 this in Ada 95 or Ada 2005:
30076 If the source code for the libraries (specs and bodies) are
30077 available, then the libraries can be migrated in the same way as the
30080 If the source code for the specs but not the bodies are
30081 available, then you can reimplement the bodies.
30083 Some features introduced by Ada 95 obviate the need for library support. For
30084 example most Ada 83 vendors supplied a package for unsigned integers. The
30085 Ada 95 modular type feature is the preferred way to handle this need, so
30086 instead of migrating or reimplementing the unsigned integer package it may
30087 be preferable to retrofit the application using modular types.
30090 @node Elaboration order
30091 @subsection Elaboration order
30093 The implementation can choose any elaboration order consistent with the unit
30094 dependency relationship. This freedom means that some orders can result in
30095 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30096 to invoke a subprogram its body has been elaborated, or to instantiate a
30097 generic before the generic body has been elaborated. By default GNAT
30098 attempts to choose a safe order (one that will not encounter access before
30099 elaboration problems) by implicitly inserting @code{Elaborate} or
30100 @code{Elaborate_All} pragmas where
30101 needed. However, this can lead to the creation of elaboration circularities
30102 and a resulting rejection of the program by gnatbind. This issue is
30103 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30104 In brief, there are several
30105 ways to deal with this situation:
30109 Modify the program to eliminate the circularities, e.g.@: by moving
30110 elaboration-time code into explicitly-invoked procedures
30112 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30113 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30114 @code{Elaborate_All}
30115 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30116 (by selectively suppressing elaboration checks via pragma
30117 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30120 @node Target-specific aspects
30121 @subsection Target-specific aspects
30123 Low-level applications need to deal with machine addresses, data
30124 representations, interfacing with assembler code, and similar issues. If
30125 such an Ada 83 application is being ported to different target hardware (for
30126 example where the byte endianness has changed) then you will need to
30127 carefully examine the program logic; the porting effort will heavily depend
30128 on the robustness of the original design. Moreover, Ada 95 (and thus
30129 Ada 2005) are sometimes
30130 incompatible with typical Ada 83 compiler practices regarding implicit
30131 packing, the meaning of the Size attribute, and the size of access values.
30132 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30134 @node Compatibility with Other Ada Systems
30135 @section Compatibility with Other Ada Systems
30138 If programs avoid the use of implementation dependent and
30139 implementation defined features, as documented in the @cite{Ada
30140 Reference Manual}, there should be a high degree of portability between
30141 GNAT and other Ada systems. The following are specific items which
30142 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30143 compilers, but do not affect porting code to GNAT@.
30144 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30145 the following issues may or may not arise for Ada 2005 programs
30146 when other compilers appear.)
30149 @item Ada 83 Pragmas and Attributes
30150 Ada 95 compilers are allowed, but not required, to implement the missing
30151 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30152 GNAT implements all such pragmas and attributes, eliminating this as
30153 a compatibility concern, but some other Ada 95 compilers reject these
30154 pragmas and attributes.
30156 @item Specialized Needs Annexes
30157 GNAT implements the full set of special needs annexes. At the
30158 current time, it is the only Ada 95 compiler to do so. This means that
30159 programs making use of these features may not be portable to other Ada
30160 95 compilation systems.
30162 @item Representation Clauses
30163 Some other Ada 95 compilers implement only the minimal set of
30164 representation clauses required by the Ada 95 reference manual. GNAT goes
30165 far beyond this minimal set, as described in the next section.
30168 @node Representation Clauses
30169 @section Representation Clauses
30172 The Ada 83 reference manual was quite vague in describing both the minimal
30173 required implementation of representation clauses, and also their precise
30174 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30175 minimal set of capabilities required is still quite limited.
30177 GNAT implements the full required set of capabilities in
30178 Ada 95 and Ada 2005, but also goes much further, and in particular
30179 an effort has been made to be compatible with existing Ada 83 usage to the
30180 greatest extent possible.
30182 A few cases exist in which Ada 83 compiler behavior is incompatible with
30183 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30184 intentional or accidental dependence on specific implementation dependent
30185 characteristics of these Ada 83 compilers. The following is a list of
30186 the cases most likely to arise in existing Ada 83 code.
30189 @item Implicit Packing
30190 Some Ada 83 compilers allowed a Size specification to cause implicit
30191 packing of an array or record. This could cause expensive implicit
30192 conversions for change of representation in the presence of derived
30193 types, and the Ada design intends to avoid this possibility.
30194 Subsequent AI's were issued to make it clear that such implicit
30195 change of representation in response to a Size clause is inadvisable,
30196 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30197 Reference Manuals as implementation advice that is followed by GNAT@.
30198 The problem will show up as an error
30199 message rejecting the size clause. The fix is simply to provide
30200 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30201 a Component_Size clause.
30203 @item Meaning of Size Attribute
30204 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30205 the minimal number of bits required to hold values of the type. For example,
30206 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30207 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30208 some 32 in this situation. This problem will usually show up as a compile
30209 time error, but not always. It is a good idea to check all uses of the
30210 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30211 Object_Size can provide a useful way of duplicating the behavior of
30212 some Ada 83 compiler systems.
30214 @item Size of Access Types
30215 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30216 and that therefore it will be the same size as a System.Address value. This
30217 assumption is true for GNAT in most cases with one exception. For the case of
30218 a pointer to an unconstrained array type (where the bounds may vary from one
30219 value of the access type to another), the default is to use a ``fat pointer'',
30220 which is represented as two separate pointers, one to the bounds, and one to
30221 the array. This representation has a number of advantages, including improved
30222 efficiency. However, it may cause some difficulties in porting existing Ada 83
30223 code which makes the assumption that, for example, pointers fit in 32 bits on
30224 a machine with 32-bit addressing.
30226 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30227 access types in this case (where the designated type is an unconstrained array
30228 type). These thin pointers are indeed the same size as a System.Address value.
30229 To specify a thin pointer, use a size clause for the type, for example:
30231 @smallexample @c ada
30232 type X is access all String;
30233 for X'Size use Standard'Address_Size;
30237 which will cause the type X to be represented using a single pointer.
30238 When using this representation, the bounds are right behind the array.
30239 This representation is slightly less efficient, and does not allow quite
30240 such flexibility in the use of foreign pointers or in using the
30241 Unrestricted_Access attribute to create pointers to non-aliased objects.
30242 But for any standard portable use of the access type it will work in
30243 a functionally correct manner and allow porting of existing code.
30244 Note that another way of forcing a thin pointer representation
30245 is to use a component size clause for the element size in an array,
30246 or a record representation clause for an access field in a record.
30250 @c This brief section is only in the non-VMS version
30251 @c The complete chapter on HP Ada is in the VMS version
30252 @node Compatibility with HP Ada 83
30253 @section Compatibility with HP Ada 83
30256 The VMS version of GNAT fully implements all the pragmas and attributes
30257 provided by HP Ada 83, as well as providing the standard HP Ada 83
30258 libraries, including Starlet. In addition, data layouts and parameter
30259 passing conventions are highly compatible. This means that porting
30260 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30261 most other porting efforts. The following are some of the most
30262 significant differences between GNAT and HP Ada 83.
30265 @item Default floating-point representation
30266 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30267 it is VMS format. GNAT does implement the necessary pragmas
30268 (Long_Float, Float_Representation) for changing this default.
30271 The package System in GNAT exactly corresponds to the definition in the
30272 Ada 95 reference manual, which means that it excludes many of the
30273 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30274 that contains the additional definitions, and a special pragma,
30275 Extend_System allows this package to be treated transparently as an
30276 extension of package System.
30279 The definitions provided by Aux_DEC are exactly compatible with those
30280 in the HP Ada 83 version of System, with one exception.
30281 HP Ada provides the following declarations:
30283 @smallexample @c ada
30284 TO_ADDRESS (INTEGER)
30285 TO_ADDRESS (UNSIGNED_LONGWORD)
30286 TO_ADDRESS (@i{universal_integer})
30290 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30291 an extension to Ada 83 not strictly compatible with the reference manual.
30292 In GNAT, we are constrained to be exactly compatible with the standard,
30293 and this means we cannot provide this capability. In HP Ada 83, the
30294 point of this definition is to deal with a call like:
30296 @smallexample @c ada
30297 TO_ADDRESS (16#12777#);
30301 Normally, according to the Ada 83 standard, one would expect this to be
30302 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30303 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30304 definition using @i{universal_integer} takes precedence.
30306 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30307 is not possible to be 100% compatible. Since there are many programs using
30308 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30309 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30310 declarations provided in the GNAT version of AUX_Dec are:
30312 @smallexample @c ada
30313 function To_Address (X : Integer) return Address;
30314 pragma Pure_Function (To_Address);
30316 function To_Address_Long (X : Unsigned_Longword)
30318 pragma Pure_Function (To_Address_Long);
30322 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
30323 change the name to TO_ADDRESS_LONG@.
30325 @item Task_Id values
30326 The Task_Id values assigned will be different in the two systems, and GNAT
30327 does not provide a specified value for the Task_Id of the environment task,
30328 which in GNAT is treated like any other declared task.
30332 For full details on these and other less significant compatibility issues,
30333 see appendix E of the HP publication entitled @cite{HP Ada, Technical
30334 Overview and Comparison on HP Platforms}.
30336 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
30337 attributes are recognized, although only a subset of them can sensibly
30338 be implemented. The description of pragmas in @ref{Implementation
30339 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
30340 indicates whether or not they are applicable to non-VMS systems.
30344 @node Transitioning to 64-Bit GNAT for OpenVMS
30345 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
30348 This section is meant to assist users of pre-2006 @value{EDITION}
30349 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
30350 the version of the GNAT technology supplied in 2006 and later for
30351 OpenVMS on both Alpha and I64.
30354 * Introduction to transitioning::
30355 * Migration of 32 bit code::
30356 * Taking advantage of 64 bit addressing::
30357 * Technical details::
30360 @node Introduction to transitioning
30361 @subsection Introduction
30364 64-bit @value{EDITION} for Open VMS has been designed to meet
30369 Providing a full conforming implementation of Ada 95 and Ada 2005
30372 Allowing maximum backward compatibility, thus easing migration of existing
30376 Supplying a path for exploiting the full 64-bit address range
30380 Ada's strong typing semantics has made it
30381 impractical to have different 32-bit and 64-bit modes. As soon as
30382 one object could possibly be outside the 32-bit address space, this
30383 would make it necessary for the @code{System.Address} type to be 64 bits.
30384 In particular, this would cause inconsistencies if 32-bit code is
30385 called from 64-bit code that raises an exception.
30387 This issue has been resolved by always using 64-bit addressing
30388 at the system level, but allowing for automatic conversions between
30389 32-bit and 64-bit addresses where required. Thus users who
30390 do not currently require 64-bit addressing capabilities, can
30391 recompile their code with only minimal changes (and indeed
30392 if the code is written in portable Ada, with no assumptions about
30393 the size of the @code{Address} type, then no changes at all are necessary).
30395 this approach provides a simple, gradual upgrade path to future
30396 use of larger memories than available for 32-bit systems.
30397 Also, newly written applications or libraries will by default
30398 be fully compatible with future systems exploiting 64-bit
30399 addressing capabilities.
30401 @ref{Migration of 32 bit code}, will focus on porting applications
30402 that do not require more than 2 GB of
30403 addressable memory. This code will be referred to as
30404 @emph{32-bit code}.
30405 For applications intending to exploit the full 64-bit address space,
30406 @ref{Taking advantage of 64 bit addressing},
30407 will consider further changes that may be required.
30408 Such code will be referred to below as @emph{64-bit code}.
30410 @node Migration of 32 bit code
30411 @subsection Migration of 32-bit code
30416 * Unchecked conversions::
30417 * Predefined constants::
30418 * Interfacing with C::
30419 * Experience with source compatibility::
30422 @node Address types
30423 @subsubsection Address types
30426 To solve the problem of mixing 64-bit and 32-bit addressing,
30427 while maintaining maximum backward compatibility, the following
30428 approach has been taken:
30432 @code{System.Address} always has a size of 64 bits
30435 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
30439 Since @code{System.Short_Address} is a subtype of @code{System.Address},
30440 a @code{Short_Address}
30441 may be used where an @code{Address} is required, and vice versa, without
30442 needing explicit type conversions.
30443 By virtue of the Open VMS parameter passing conventions,
30445 and exported subprograms that have 32-bit address parameters are
30446 compatible with those that have 64-bit address parameters.
30447 (See @ref{Making code 64 bit clean} for details.)
30449 The areas that may need attention are those where record types have
30450 been defined that contain components of the type @code{System.Address}, and
30451 where objects of this type are passed to code expecting a record layout with
30454 Different compilers on different platforms cannot be
30455 expected to represent the same type in the same way,
30456 since alignment constraints
30457 and other system-dependent properties affect the compiler's decision.
30458 For that reason, Ada code
30459 generally uses representation clauses to specify the expected
30460 layout where required.
30462 If such a representation clause uses 32 bits for a component having
30463 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
30464 will detect that error and produce a specific diagnostic message.
30465 The developer should then determine whether the representation
30466 should be 64 bits or not and make either of two changes:
30467 change the size to 64 bits and leave the type as @code{System.Address}, or
30468 leave the size as 32 bits and change the type to @code{System.Short_Address}.
30469 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
30470 required in any code setting or accessing the field; the compiler will
30471 automatically perform any needed conversions between address
30475 @subsubsection Access types
30478 By default, objects designated by access values are always
30479 allocated in the 32-bit
30480 address space. Thus legacy code will never contain
30481 any objects that are not addressable with 32-bit addresses, and
30482 the compiler will never raise exceptions as result of mixing
30483 32-bit and 64-bit addresses.
30485 However, the access values themselves are represented in 64 bits, for optimum
30486 performance and future compatibility with 64-bit code. As was
30487 the case with @code{System.Address}, the compiler will give an error message
30488 if an object or record component has a representation clause that
30489 requires the access value to fit in 32 bits. In such a situation,
30490 an explicit size clause for the access type, specifying 32 bits,
30491 will have the desired effect.
30493 General access types (declared with @code{access all}) can never be
30494 32 bits, as values of such types must be able to refer to any object
30495 of the designated type,
30496 including objects residing outside the 32-bit address range.
30497 Existing Ada 83 code will not contain such type definitions,
30498 however, since general access types were introduced in Ada 95.
30500 @node Unchecked conversions
30501 @subsubsection Unchecked conversions
30504 In the case of an @code{Unchecked_Conversion} where the source type is a
30505 64-bit access type or the type @code{System.Address}, and the target
30506 type is a 32-bit type, the compiler will generate a warning.
30507 Even though the generated code will still perform the required
30508 conversions, it is highly recommended in these cases to use
30509 respectively a 32-bit access type or @code{System.Short_Address}
30510 as the source type.
30512 @node Predefined constants
30513 @subsubsection Predefined constants
30516 The following table shows the correspondence between pre-2006 versions of
30517 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
30520 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
30521 @item @b{Constant} @tab @b{Old} @tab @b{New}
30522 @item @code{System.Word_Size} @tab 32 @tab 64
30523 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
30524 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
30525 @item @code{System.Address_Size} @tab 32 @tab 64
30529 If you need to refer to the specific
30530 memory size of a 32-bit implementation, instead of the
30531 actual memory size, use @code{System.Short_Memory_Size}
30532 rather than @code{System.Memory_Size}.
30533 Similarly, references to @code{System.Address_Size} may need
30534 to be replaced by @code{System.Short_Address'Size}.
30535 The program @command{gnatfind} may be useful for locating
30536 references to the above constants, so that you can verify that they
30539 @node Interfacing with C
30540 @subsubsection Interfacing with C
30543 In order to minimize the impact of the transition to 64-bit addresses on
30544 legacy programs, some fundamental types in the @code{Interfaces.C}
30545 package hierarchy continue to be represented in 32 bits.
30546 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
30547 This eases integration with the default HP C layout choices, for example
30548 as found in the system routines in @code{DECC$SHR.EXE}.
30549 Because of this implementation choice, the type fully compatible with
30550 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
30551 Depending on the context the compiler will issue a
30552 warning or an error when type @code{Address} is used, alerting the user to a
30553 potential problem. Otherwise 32-bit programs that use
30554 @code{Interfaces.C} should normally not require code modifications
30556 The other issue arising with C interfacing concerns pragma @code{Convention}.
30557 For VMS 64-bit systems, there is an issue of the appropriate default size
30558 of C convention pointers in the absence of an explicit size clause. The HP
30559 C compiler can choose either 32 or 64 bits depending on compiler options.
30560 GNAT chooses 32-bits rather than 64-bits in the default case where no size
30561 clause is given. This proves a better choice for porting 32-bit legacy
30562 applications. In order to have a 64-bit representation, it is necessary to
30563 specify a size representation clause. For example:
30565 @smallexample @c ada
30566 type int_star is access Interfaces.C.int;
30567 pragma Convention(C, int_star);
30568 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
30571 @node Experience with source compatibility
30572 @subsubsection Experience with source compatibility
30575 The Security Server and STARLET on I64 provide an interesting ``test case''
30576 for source compatibility issues, since it is in such system code
30577 where assumptions about @code{Address} size might be expected to occur.
30578 Indeed, there were a small number of occasions in the Security Server
30579 file @file{jibdef.ads}
30580 where a representation clause for a record type specified
30581 32 bits for a component of type @code{Address}.
30582 All of these errors were detected by the compiler.
30583 The repair was obvious and immediate; to simply replace @code{Address} by
30584 @code{Short_Address}.
30586 In the case of STARLET, there were several record types that should
30587 have had representation clauses but did not. In these record types
30588 there was an implicit assumption that an @code{Address} value occupied
30590 These compiled without error, but their usage resulted in run-time error
30591 returns from STARLET system calls.
30592 Future GNAT technology enhancements may include a tool that detects and flags
30593 these sorts of potential source code porting problems.
30595 @c ****************************************
30596 @node Taking advantage of 64 bit addressing
30597 @subsection Taking advantage of 64-bit addressing
30600 * Making code 64 bit clean::
30601 * Allocating memory from the 64 bit storage pool::
30602 * Restrictions on use of 64 bit objects::
30603 * Using 64 bit storage pools by default::
30604 * General access types::
30605 * STARLET and other predefined libraries::
30608 @node Making code 64 bit clean
30609 @subsubsection Making code 64-bit clean
30612 In order to prevent problems that may occur when (parts of) a
30613 system start using memory outside the 32-bit address range,
30614 we recommend some additional guidelines:
30618 For imported subprograms that take parameters of the
30619 type @code{System.Address}, ensure that these subprograms can
30620 indeed handle 64-bit addresses. If not, or when in doubt,
30621 change the subprogram declaration to specify
30622 @code{System.Short_Address} instead.
30625 Resolve all warnings related to size mismatches in
30626 unchecked conversions. Failing to do so causes
30627 erroneous execution if the source object is outside
30628 the 32-bit address space.
30631 (optional) Explicitly use the 32-bit storage pool
30632 for access types used in a 32-bit context, or use
30633 generic access types where possible
30634 (@pxref{Restrictions on use of 64 bit objects}).
30638 If these rules are followed, the compiler will automatically insert
30639 any necessary checks to ensure that no addresses or access values
30640 passed to 32-bit code ever refer to objects outside the 32-bit
30642 Any attempt to do this will raise @code{Constraint_Error}.
30644 @node Allocating memory from the 64 bit storage pool
30645 @subsubsection Allocating memory from the 64-bit storage pool
30648 For any access type @code{T} that potentially requires memory allocations
30649 beyond the 32-bit address space,
30650 use the following representation clause:
30652 @smallexample @c ada
30653 for T'Storage_Pool use System.Pool_64;
30656 @node Restrictions on use of 64 bit objects
30657 @subsubsection Restrictions on use of 64-bit objects
30660 Taking the address of an object allocated from a 64-bit storage pool,
30661 and then passing this address to a subprogram expecting
30662 @code{System.Short_Address},
30663 or assigning it to a variable of type @code{Short_Address}, will cause
30664 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
30665 (@pxref{Making code 64 bit clean}), or checks are suppressed,
30666 no exception is raised and execution
30667 will become erroneous.
30669 @node Using 64 bit storage pools by default
30670 @subsubsection Using 64-bit storage pools by default
30673 In some cases it may be desirable to have the compiler allocate
30674 from 64-bit storage pools by default. This may be the case for
30675 libraries that are 64-bit clean, but may be used in both 32-bit
30676 and 64-bit contexts. For these cases the following configuration
30677 pragma may be specified:
30679 @smallexample @c ada
30680 pragma Pool_64_Default;
30684 Any code compiled in the context of this pragma will by default
30685 use the @code{System.Pool_64} storage pool. This default may be overridden
30686 for a specific access type @code{T} by the representation clause:
30688 @smallexample @c ada
30689 for T'Storage_Pool use System.Pool_32;
30693 Any object whose address may be passed to a subprogram with a
30694 @code{Short_Address} argument, or assigned to a variable of type
30695 @code{Short_Address}, needs to be allocated from this pool.
30697 @node General access types
30698 @subsubsection General access types
30701 Objects designated by access values from a
30702 general access type (declared with @code{access all}) are never allocated
30703 from a 64-bit storage pool. Code that uses general access types will
30704 accept objects allocated in either 32-bit or 64-bit address spaces,
30705 but never allocate objects outside the 32-bit address space.
30706 Using general access types ensures maximum compatibility with both
30707 32-bit and 64-bit code.
30709 @node STARLET and other predefined libraries
30710 @subsubsection STARLET and other predefined libraries
30713 All code that comes as part of GNAT is 64-bit clean, but the
30714 restrictions given in @ref{Restrictions on use of 64 bit objects},
30715 still apply. Look at the package
30716 specs to see in which contexts objects allocated
30717 in 64-bit address space are acceptable.
30719 @node Technical details
30720 @subsection Technical details
30723 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
30724 Ada standard with respect to the type of @code{System.Address}. Previous
30725 versions of GNAT Pro have defined this type as private and implemented it as a
30728 In order to allow defining @code{System.Short_Address} as a proper subtype,
30729 and to match the implicit sign extension in parameter passing,
30730 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
30731 visible (i.e., non-private) integer type.
30732 Standard operations on the type, such as the binary operators ``+'', ``-'',
30733 etc., that take @code{Address} operands and return an @code{Address} result,
30734 have been hidden by declaring these
30735 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
30736 ambiguities that would otherwise result from overloading.
30737 (Note that, although @code{Address} is a visible integer type,
30738 good programming practice dictates against exploiting the type's
30739 integer properties such as literals, since this will compromise
30742 Defining @code{Address} as a visible integer type helps achieve
30743 maximum compatibility for existing Ada code,
30744 without sacrificing the capabilities of the 64-bit architecture.
30747 @c ************************************************
30749 @node Microsoft Windows Topics
30750 @appendix Microsoft Windows Topics
30756 This chapter describes topics that are specific to the Microsoft Windows
30757 platforms (NT, 2000, and XP Professional).
30760 * Using GNAT on Windows::
30761 * Using a network installation of GNAT::
30762 * CONSOLE and WINDOWS subsystems::
30763 * Temporary Files::
30764 * Mixed-Language Programming on Windows::
30765 * Windows Calling Conventions::
30766 * Introduction to Dynamic Link Libraries (DLLs)::
30767 * Using DLLs with GNAT::
30768 * Building DLLs with GNAT::
30769 * Building DLLs with GNAT Project files::
30770 * Building DLLs with gnatdll::
30771 * GNAT and Windows Resources::
30772 * Debugging a DLL::
30773 * Setting Stack Size from gnatlink::
30774 * Setting Heap Size from gnatlink::
30777 @node Using GNAT on Windows
30778 @section Using GNAT on Windows
30781 One of the strengths of the GNAT technology is that its tool set
30782 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
30783 @code{gdb} debugger, etc.) is used in the same way regardless of the
30786 On Windows this tool set is complemented by a number of Microsoft-specific
30787 tools that have been provided to facilitate interoperability with Windows
30788 when this is required. With these tools:
30793 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
30797 You can use any Dynamically Linked Library (DLL) in your Ada code (both
30798 relocatable and non-relocatable DLLs are supported).
30801 You can build Ada DLLs for use in other applications. These applications
30802 can be written in a language other than Ada (e.g., C, C++, etc). Again both
30803 relocatable and non-relocatable Ada DLLs are supported.
30806 You can include Windows resources in your Ada application.
30809 You can use or create COM/DCOM objects.
30813 Immediately below are listed all known general GNAT-for-Windows restrictions.
30814 Other restrictions about specific features like Windows Resources and DLLs
30815 are listed in separate sections below.
30820 It is not possible to use @code{GetLastError} and @code{SetLastError}
30821 when tasking, protected records, or exceptions are used. In these
30822 cases, in order to implement Ada semantics, the GNAT run-time system
30823 calls certain Win32 routines that set the last error variable to 0 upon
30824 success. It should be possible to use @code{GetLastError} and
30825 @code{SetLastError} when tasking, protected record, and exception
30826 features are not used, but it is not guaranteed to work.
30829 It is not possible to link against Microsoft libraries except for
30830 import libraries. The library must be built to be compatible with
30831 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
30832 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
30833 not be compatible with the GNAT runtime. Even if the library is
30834 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
30837 When the compilation environment is located on FAT32 drives, users may
30838 experience recompilations of the source files that have not changed if
30839 Daylight Saving Time (DST) state has changed since the last time files
30840 were compiled. NTFS drives do not have this problem.
30843 No components of the GNAT toolset use any entries in the Windows
30844 registry. The only entries that can be created are file associations and
30845 PATH settings, provided the user has chosen to create them at installation
30846 time, as well as some minimal book-keeping information needed to correctly
30847 uninstall or integrate different GNAT products.
30850 @node Using a network installation of GNAT
30851 @section Using a network installation of GNAT
30854 Make sure the system on which GNAT is installed is accessible from the
30855 current machine, i.e., the install location is shared over the network.
30856 Shared resources are accessed on Windows by means of UNC paths, which
30857 have the format @code{\\server\sharename\path}
30859 In order to use such a network installation, simply add the UNC path of the
30860 @file{bin} directory of your GNAT installation in front of your PATH. For
30861 example, if GNAT is installed in @file{\GNAT} directory of a share location
30862 called @file{c-drive} on a machine @file{LOKI}, the following command will
30865 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
30867 Be aware that every compilation using the network installation results in the
30868 transfer of large amounts of data across the network and will likely cause
30869 serious performance penalty.
30871 @node CONSOLE and WINDOWS subsystems
30872 @section CONSOLE and WINDOWS subsystems
30873 @cindex CONSOLE Subsystem
30874 @cindex WINDOWS Subsystem
30878 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
30879 (which is the default subsystem) will always create a console when
30880 launching the application. This is not something desirable when the
30881 application has a Windows GUI. To get rid of this console the
30882 application must be using the @code{WINDOWS} subsystem. To do so
30883 the @option{-mwindows} linker option must be specified.
30886 $ gnatmake winprog -largs -mwindows
30889 @node Temporary Files
30890 @section Temporary Files
30891 @cindex Temporary files
30894 It is possible to control where temporary files gets created by setting
30895 the @env{TMP} environment variable. The file will be created:
30898 @item Under the directory pointed to by the @env{TMP} environment variable if
30899 this directory exists.
30901 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
30902 set (or not pointing to a directory) and if this directory exists.
30904 @item Under the current working directory otherwise.
30908 This allows you to determine exactly where the temporary
30909 file will be created. This is particularly useful in networked
30910 environments where you may not have write access to some
30913 @node Mixed-Language Programming on Windows
30914 @section Mixed-Language Programming on Windows
30917 Developing pure Ada applications on Windows is no different than on
30918 other GNAT-supported platforms. However, when developing or porting an
30919 application that contains a mix of Ada and C/C++, the choice of your
30920 Windows C/C++ development environment conditions your overall
30921 interoperability strategy.
30923 If you use @command{gcc} to compile the non-Ada part of your application,
30924 there are no Windows-specific restrictions that affect the overall
30925 interoperability with your Ada code. If you plan to use
30926 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
30927 the following limitations:
30931 You cannot link your Ada code with an object or library generated with
30932 Microsoft tools if these use the @code{.tls} section (Thread Local
30933 Storage section) since the GNAT linker does not yet support this section.
30936 You cannot link your Ada code with an object or library generated with
30937 Microsoft tools if these use I/O routines other than those provided in
30938 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
30939 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
30940 libraries can cause a conflict with @code{msvcrt.dll} services. For
30941 instance Visual C++ I/O stream routines conflict with those in
30946 If you do want to use the Microsoft tools for your non-Ada code and hit one
30947 of the above limitations, you have two choices:
30951 Encapsulate your non-Ada code in a DLL to be linked with your Ada
30952 application. In this case, use the Microsoft or whatever environment to
30953 build the DLL and use GNAT to build your executable
30954 (@pxref{Using DLLs with GNAT}).
30957 Or you can encapsulate your Ada code in a DLL to be linked with the
30958 other part of your application. In this case, use GNAT to build the DLL
30959 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
30960 environment to build your executable.
30963 @node Windows Calling Conventions
30964 @section Windows Calling Conventions
30969 * C Calling Convention::
30970 * Stdcall Calling Convention::
30971 * Win32 Calling Convention::
30972 * DLL Calling Convention::
30976 When a subprogram @code{F} (caller) calls a subprogram @code{G}
30977 (callee), there are several ways to push @code{G}'s parameters on the
30978 stack and there are several possible scenarios to clean up the stack
30979 upon @code{G}'s return. A calling convention is an agreed upon software
30980 protocol whereby the responsibilities between the caller (@code{F}) and
30981 the callee (@code{G}) are clearly defined. Several calling conventions
30982 are available for Windows:
30986 @code{C} (Microsoft defined)
30989 @code{Stdcall} (Microsoft defined)
30992 @code{Win32} (GNAT specific)
30995 @code{DLL} (GNAT specific)
30998 @node C Calling Convention
30999 @subsection @code{C} Calling Convention
31002 This is the default calling convention used when interfacing to C/C++
31003 routines compiled with either @command{gcc} or Microsoft Visual C++.
31005 In the @code{C} calling convention subprogram parameters are pushed on the
31006 stack by the caller from right to left. The caller itself is in charge of
31007 cleaning up the stack after the call. In addition, the name of a routine
31008 with @code{C} calling convention is mangled by adding a leading underscore.
31010 The name to use on the Ada side when importing (or exporting) a routine
31011 with @code{C} calling convention is the name of the routine. For
31012 instance the C function:
31015 int get_val (long);
31019 should be imported from Ada as follows:
31021 @smallexample @c ada
31023 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31024 pragma Import (C, Get_Val, External_Name => "get_val");
31029 Note that in this particular case the @code{External_Name} parameter could
31030 have been omitted since, when missing, this parameter is taken to be the
31031 name of the Ada entity in lower case. When the @code{Link_Name} parameter
31032 is missing, as in the above example, this parameter is set to be the
31033 @code{External_Name} with a leading underscore.
31035 When importing a variable defined in C, you should always use the @code{C}
31036 calling convention unless the object containing the variable is part of a
31037 DLL (in which case you should use the @code{Stdcall} calling
31038 convention, @pxref{Stdcall Calling Convention}).
31040 @node Stdcall Calling Convention
31041 @subsection @code{Stdcall} Calling Convention
31044 This convention, which was the calling convention used for Pascal
31045 programs, is used by Microsoft for all the routines in the Win32 API for
31046 efficiency reasons. It must be used to import any routine for which this
31047 convention was specified.
31049 In the @code{Stdcall} calling convention subprogram parameters are pushed
31050 on the stack by the caller from right to left. The callee (and not the
31051 caller) is in charge of cleaning the stack on routine exit. In addition,
31052 the name of a routine with @code{Stdcall} calling convention is mangled by
31053 adding a leading underscore (as for the @code{C} calling convention) and a
31054 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
31055 bytes) of the parameters passed to the routine.
31057 The name to use on the Ada side when importing a C routine with a
31058 @code{Stdcall} calling convention is the name of the C routine. The leading
31059 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
31060 the compiler. For instance the Win32 function:
31063 @b{APIENTRY} int get_val (long);
31067 should be imported from Ada as follows:
31069 @smallexample @c ada
31071 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31072 pragma Import (Stdcall, Get_Val);
31073 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
31078 As for the @code{C} calling convention, when the @code{External_Name}
31079 parameter is missing, it is taken to be the name of the Ada entity in lower
31080 case. If instead of writing the above import pragma you write:
31082 @smallexample @c ada
31084 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31085 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31090 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31091 of specifying the @code{External_Name} parameter you specify the
31092 @code{Link_Name} as in the following example:
31094 @smallexample @c ada
31096 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31097 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31102 then the imported routine is @code{retrieve_val}, that is, there is no
31103 decoration at all. No leading underscore and no Stdcall suffix
31104 @code{@@}@code{@var{nn}}.
31107 This is especially important as in some special cases a DLL's entry
31108 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31109 name generated for a call has it.
31112 It is also possible to import variables defined in a DLL by using an
31113 import pragma for a variable. As an example, if a DLL contains a
31114 variable defined as:
31121 then, to access this variable from Ada you should write:
31123 @smallexample @c ada
31125 My_Var : Interfaces.C.int;
31126 pragma Import (Stdcall, My_Var);
31131 Note that to ease building cross-platform bindings this convention
31132 will be handled as a @code{C} calling convention on non-Windows platforms.
31134 @node Win32 Calling Convention
31135 @subsection @code{Win32} Calling Convention
31138 This convention, which is GNAT-specific is fully equivalent to the
31139 @code{Stdcall} calling convention described above.
31141 @node DLL Calling Convention
31142 @subsection @code{DLL} Calling Convention
31145 This convention, which is GNAT-specific is fully equivalent to the
31146 @code{Stdcall} calling convention described above.
31148 @node Introduction to Dynamic Link Libraries (DLLs)
31149 @section Introduction to Dynamic Link Libraries (DLLs)
31153 A Dynamically Linked Library (DLL) is a library that can be shared by
31154 several applications running under Windows. A DLL can contain any number of
31155 routines and variables.
31157 One advantage of DLLs is that you can change and enhance them without
31158 forcing all the applications that depend on them to be relinked or
31159 recompiled. However, you should be aware than all calls to DLL routines are
31160 slower since, as you will understand below, such calls are indirect.
31162 To illustrate the remainder of this section, suppose that an application
31163 wants to use the services of a DLL @file{API.dll}. To use the services
31164 provided by @file{API.dll} you must statically link against the DLL or
31165 an import library which contains a jump table with an entry for each
31166 routine and variable exported by the DLL. In the Microsoft world this
31167 import library is called @file{API.lib}. When using GNAT this import
31168 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31169 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31171 After you have linked your application with the DLL or the import library
31172 and you run your application, here is what happens:
31176 Your application is loaded into memory.
31179 The DLL @file{API.dll} is mapped into the address space of your
31180 application. This means that:
31184 The DLL will use the stack of the calling thread.
31187 The DLL will use the virtual address space of the calling process.
31190 The DLL will allocate memory from the virtual address space of the calling
31194 Handles (pointers) can be safely exchanged between routines in the DLL
31195 routines and routines in the application using the DLL.
31199 The entries in the jump table (from the import library @file{libAPI.dll.a}
31200 or @file{API.lib} or automatically created when linking against a DLL)
31201 which is part of your application are initialized with the addresses
31202 of the routines and variables in @file{API.dll}.
31205 If present in @file{API.dll}, routines @code{DllMain} or
31206 @code{DllMainCRTStartup} are invoked. These routines typically contain
31207 the initialization code needed for the well-being of the routines and
31208 variables exported by the DLL.
31212 There is an additional point which is worth mentioning. In the Windows
31213 world there are two kind of DLLs: relocatable and non-relocatable
31214 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31215 in the target application address space. If the addresses of two
31216 non-relocatable DLLs overlap and these happen to be used by the same
31217 application, a conflict will occur and the application will run
31218 incorrectly. Hence, when possible, it is always preferable to use and
31219 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31220 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31221 User's Guide) removes the debugging symbols from the DLL but the DLL can
31222 still be relocated.
31224 As a side note, an interesting difference between Microsoft DLLs and
31225 Unix shared libraries, is the fact that on most Unix systems all public
31226 routines are exported by default in a Unix shared library, while under
31227 Windows it is possible (but not required) to list exported routines in
31228 a definition file (@pxref{The Definition File}).
31230 @node Using DLLs with GNAT
31231 @section Using DLLs with GNAT
31234 * Creating an Ada Spec for the DLL Services::
31235 * Creating an Import Library::
31239 To use the services of a DLL, say @file{API.dll}, in your Ada application
31244 The Ada spec for the routines and/or variables you want to access in
31245 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31246 header files provided with the DLL.
31249 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31250 mentioned an import library is a statically linked library containing the
31251 import table which will be filled at load time to point to the actual
31252 @file{API.dll} routines. Sometimes you don't have an import library for the
31253 DLL you want to use. The following sections will explain how to build
31254 one. Note that this is optional.
31257 The actual DLL, @file{API.dll}.
31261 Once you have all the above, to compile an Ada application that uses the
31262 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31263 you simply issue the command
31266 $ gnatmake my_ada_app -largs -lAPI
31270 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31271 tells the GNAT linker to look first for a library named @file{API.lib}
31272 (Microsoft-style name) and if not found for a libraries named
31273 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31274 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31275 contains the following pragma
31277 @smallexample @c ada
31278 pragma Linker_Options ("-lAPI");
31282 you do not have to add @option{-largs -lAPI} at the end of the
31283 @command{gnatmake} command.
31285 If any one of the items above is missing you will have to create it
31286 yourself. The following sections explain how to do so using as an
31287 example a fictitious DLL called @file{API.dll}.
31289 @node Creating an Ada Spec for the DLL Services
31290 @subsection Creating an Ada Spec for the DLL Services
31293 A DLL typically comes with a C/C++ header file which provides the
31294 definitions of the routines and variables exported by the DLL. The Ada
31295 equivalent of this header file is a package spec that contains definitions
31296 for the imported entities. If the DLL you intend to use does not come with
31297 an Ada spec you have to generate one such spec yourself. For example if
31298 the header file of @file{API.dll} is a file @file{api.h} containing the
31299 following two definitions:
31311 then the equivalent Ada spec could be:
31313 @smallexample @c ada
31316 with Interfaces.C.Strings;
31321 function Get (Str : C.Strings.Chars_Ptr) return C.int;
31324 pragma Import (C, Get);
31325 pragma Import (DLL, Some_Var);
31332 Note that a variable is
31333 @strong{always imported with a Stdcall convention}. A function
31334 can have @code{C} or @code{Stdcall} convention.
31335 (@pxref{Windows Calling Conventions}).
31337 @node Creating an Import Library
31338 @subsection Creating an Import Library
31339 @cindex Import library
31342 * The Definition File::
31343 * GNAT-Style Import Library::
31344 * Microsoft-Style Import Library::
31348 If a Microsoft-style import library @file{API.lib} or a GNAT-style
31349 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
31350 with @file{API.dll} you can skip this section. You can also skip this
31351 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
31352 as in this case it is possible to link directly against the
31353 DLL. Otherwise read on.
31355 @node The Definition File
31356 @subsubsection The Definition File
31357 @cindex Definition file
31361 As previously mentioned, and unlike Unix systems, the list of symbols
31362 that are exported from a DLL must be provided explicitly in Windows.
31363 The main goal of a definition file is precisely that: list the symbols
31364 exported by a DLL. A definition file (usually a file with a @code{.def}
31365 suffix) has the following structure:
31370 @r{[}LIBRARY @var{name}@r{]}
31371 @r{[}DESCRIPTION @var{string}@r{]}
31381 @item LIBRARY @var{name}
31382 This section, which is optional, gives the name of the DLL.
31384 @item DESCRIPTION @var{string}
31385 This section, which is optional, gives a description string that will be
31386 embedded in the import library.
31389 This section gives the list of exported symbols (procedures, functions or
31390 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
31391 section of @file{API.def} looks like:
31405 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
31406 (@pxref{Windows Calling Conventions}) for a Stdcall
31407 calling convention function in the exported symbols list.
31410 There can actually be other sections in a definition file, but these
31411 sections are not relevant to the discussion at hand.
31413 @node GNAT-Style Import Library
31414 @subsubsection GNAT-Style Import Library
31417 To create a static import library from @file{API.dll} with the GNAT tools
31418 you should proceed as follows:
31422 Create the definition file @file{API.def} (@pxref{The Definition File}).
31423 For that use the @code{dll2def} tool as follows:
31426 $ dll2def API.dll > API.def
31430 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
31431 to standard output the list of entry points in the DLL. Note that if
31432 some routines in the DLL have the @code{Stdcall} convention
31433 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
31434 suffix then you'll have to edit @file{api.def} to add it, and specify
31435 @option{-k} to @command{gnatdll} when creating the import library.
31438 Here are some hints to find the right @code{@@}@var{nn} suffix.
31442 If you have the Microsoft import library (.lib), it is possible to get
31443 the right symbols by using Microsoft @code{dumpbin} tool (see the
31444 corresponding Microsoft documentation for further details).
31447 $ dumpbin /exports api.lib
31451 If you have a message about a missing symbol at link time the compiler
31452 tells you what symbol is expected. You just have to go back to the
31453 definition file and add the right suffix.
31457 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
31458 (@pxref{Using gnatdll}) as follows:
31461 $ gnatdll -e API.def -d API.dll
31465 @code{gnatdll} takes as input a definition file @file{API.def} and the
31466 name of the DLL containing the services listed in the definition file
31467 @file{API.dll}. The name of the static import library generated is
31468 computed from the name of the definition file as follows: if the
31469 definition file name is @var{xyz}@code{.def}, the import library name will
31470 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
31471 @option{-e} could have been removed because the name of the definition
31472 file (before the ``@code{.def}'' suffix) is the same as the name of the
31473 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
31476 @node Microsoft-Style Import Library
31477 @subsubsection Microsoft-Style Import Library
31480 With GNAT you can either use a GNAT-style or Microsoft-style import
31481 library. A Microsoft import library is needed only if you plan to make an
31482 Ada DLL available to applications developed with Microsoft
31483 tools (@pxref{Mixed-Language Programming on Windows}).
31485 To create a Microsoft-style import library for @file{API.dll} you
31486 should proceed as follows:
31490 Create the definition file @file{API.def} from the DLL. For this use either
31491 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
31492 tool (see the corresponding Microsoft documentation for further details).
31495 Build the actual import library using Microsoft's @code{lib} utility:
31498 $ lib -machine:IX86 -def:API.def -out:API.lib
31502 If you use the above command the definition file @file{API.def} must
31503 contain a line giving the name of the DLL:
31510 See the Microsoft documentation for further details about the usage of
31514 @node Building DLLs with GNAT
31515 @section Building DLLs with GNAT
31516 @cindex DLLs, building
31519 This section explain how to build DLLs using the GNAT built-in DLL
31520 support. With the following procedure it is straight forward to build
31521 and use DLLs with GNAT.
31525 @item building object files
31527 The first step is to build all objects files that are to be included
31528 into the DLL. This is done by using the standard @command{gnatmake} tool.
31530 @item building the DLL
31532 To build the DLL you must use @command{gcc}'s @option{-shared}
31533 option. It is quite simple to use this method:
31536 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
31539 It is important to note that in this case all symbols found in the
31540 object files are automatically exported. It is possible to restrict
31541 the set of symbols to export by passing to @command{gcc} a definition
31542 file, @pxref{The Definition File}. For example:
31545 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
31548 If you use a definition file you must export the elaboration procedures
31549 for every package that required one. Elaboration procedures are named
31550 using the package name followed by "_E".
31552 @item preparing DLL to be used
31554 For the DLL to be used by client programs the bodies must be hidden
31555 from it and the .ali set with read-only attribute. This is very important
31556 otherwise GNAT will recompile all packages and will not actually use
31557 the code in the DLL. For example:
31561 $ copy *.ads *.ali api.dll apilib
31562 $ attrib +R apilib\*.ali
31567 At this point it is possible to use the DLL by directly linking
31568 against it. Note that you must use the GNAT shared runtime when using
31569 GNAT shared libraries. This is achieved by using @option{-shared} binder's
31573 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
31576 @node Building DLLs with GNAT Project files
31577 @section Building DLLs with GNAT Project files
31578 @cindex DLLs, building
31581 There is nothing specific to Windows in the build process.
31582 @pxref{Library Projects}.
31585 Due to a system limitation, it is not possible under Windows to create threads
31586 when inside the @code{DllMain} routine which is used for auto-initialization
31587 of shared libraries, so it is not possible to have library level tasks in SALs.
31589 @node Building DLLs with gnatdll
31590 @section Building DLLs with gnatdll
31591 @cindex DLLs, building
31594 * Limitations When Using Ada DLLs from Ada::
31595 * Exporting Ada Entities::
31596 * Ada DLLs and Elaboration::
31597 * Ada DLLs and Finalization::
31598 * Creating a Spec for Ada DLLs::
31599 * Creating the Definition File::
31604 Note that it is preferred to use the built-in GNAT DLL support
31605 (@pxref{Building DLLs with GNAT}) or GNAT Project files
31606 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
31608 This section explains how to build DLLs containing Ada code using
31609 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
31610 remainder of this section.
31612 The steps required to build an Ada DLL that is to be used by Ada as well as
31613 non-Ada applications are as follows:
31617 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
31618 @code{Stdcall} calling convention to avoid any Ada name mangling for the
31619 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
31620 skip this step if you plan to use the Ada DLL only from Ada applications.
31623 Your Ada code must export an initialization routine which calls the routine
31624 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
31625 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
31626 routine exported by the Ada DLL must be invoked by the clients of the DLL
31627 to initialize the DLL.
31630 When useful, the DLL should also export a finalization routine which calls
31631 routine @code{adafinal} generated by @command{gnatbind} to perform the
31632 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
31633 The finalization routine exported by the Ada DLL must be invoked by the
31634 clients of the DLL when the DLL services are no further needed.
31637 You must provide a spec for the services exported by the Ada DLL in each
31638 of the programming languages to which you plan to make the DLL available.
31641 You must provide a definition file listing the exported entities
31642 (@pxref{The Definition File}).
31645 Finally you must use @code{gnatdll} to produce the DLL and the import
31646 library (@pxref{Using gnatdll}).
31650 Note that a relocatable DLL stripped using the @code{strip}
31651 binutils tool will not be relocatable anymore. To build a DLL without
31652 debug information pass @code{-largs -s} to @code{gnatdll}. This
31653 restriction does not apply to a DLL built using a Library Project.
31654 @pxref{Library Projects}.
31656 @node Limitations When Using Ada DLLs from Ada
31657 @subsection Limitations When Using Ada DLLs from Ada
31660 When using Ada DLLs from Ada applications there is a limitation users
31661 should be aware of. Because on Windows the GNAT run time is not in a DLL of
31662 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
31663 each Ada DLL includes the services of the GNAT run time that are necessary
31664 to the Ada code inside the DLL. As a result, when an Ada program uses an
31665 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
31666 one in the main program.
31668 It is therefore not possible to exchange GNAT run-time objects between the
31669 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
31670 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
31673 It is completely safe to exchange plain elementary, array or record types,
31674 Windows object handles, etc.
31676 @node Exporting Ada Entities
31677 @subsection Exporting Ada Entities
31678 @cindex Export table
31681 Building a DLL is a way to encapsulate a set of services usable from any
31682 application. As a result, the Ada entities exported by a DLL should be
31683 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
31684 any Ada name mangling. As an example here is an Ada package
31685 @code{API}, spec and body, exporting two procedures, a function, and a
31688 @smallexample @c ada
31691 with Interfaces.C; use Interfaces;
31693 Count : C.int := 0;
31694 function Factorial (Val : C.int) return C.int;
31696 procedure Initialize_API;
31697 procedure Finalize_API;
31698 -- Initialization & Finalization routines. More in the next section.
31700 pragma Export (C, Initialize_API);
31701 pragma Export (C, Finalize_API);
31702 pragma Export (C, Count);
31703 pragma Export (C, Factorial);
31709 @smallexample @c ada
31712 package body API is
31713 function Factorial (Val : C.int) return C.int is
31716 Count := Count + 1;
31717 for K in 1 .. Val loop
31723 procedure Initialize_API is
31725 pragma Import (C, Adainit);
31728 end Initialize_API;
31730 procedure Finalize_API is
31731 procedure Adafinal;
31732 pragma Import (C, Adafinal);
31742 If the Ada DLL you are building will only be used by Ada applications
31743 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
31744 convention. As an example, the previous package could be written as
31747 @smallexample @c ada
31751 Count : Integer := 0;
31752 function Factorial (Val : Integer) return Integer;
31754 procedure Initialize_API;
31755 procedure Finalize_API;
31756 -- Initialization and Finalization routines.
31762 @smallexample @c ada
31765 package body API is
31766 function Factorial (Val : Integer) return Integer is
31767 Fact : Integer := 1;
31769 Count := Count + 1;
31770 for K in 1 .. Val loop
31777 -- The remainder of this package body is unchanged.
31784 Note that if you do not export the Ada entities with a @code{C} or
31785 @code{Stdcall} convention you will have to provide the mangled Ada names
31786 in the definition file of the Ada DLL
31787 (@pxref{Creating the Definition File}).
31789 @node Ada DLLs and Elaboration
31790 @subsection Ada DLLs and Elaboration
31791 @cindex DLLs and elaboration
31794 The DLL that you are building contains your Ada code as well as all the
31795 routines in the Ada library that are needed by it. The first thing a
31796 user of your DLL must do is elaborate the Ada code
31797 (@pxref{Elaboration Order Handling in GNAT}).
31799 To achieve this you must export an initialization routine
31800 (@code{Initialize_API} in the previous example), which must be invoked
31801 before using any of the DLL services. This elaboration routine must call
31802 the Ada elaboration routine @code{adainit} generated by the GNAT binder
31803 (@pxref{Binding with Non-Ada Main Programs}). See the body of
31804 @code{Initialize_Api} for an example. Note that the GNAT binder is
31805 automatically invoked during the DLL build process by the @code{gnatdll}
31806 tool (@pxref{Using gnatdll}).
31808 When a DLL is loaded, Windows systematically invokes a routine called
31809 @code{DllMain}. It would therefore be possible to call @code{adainit}
31810 directly from @code{DllMain} without having to provide an explicit
31811 initialization routine. Unfortunately, it is not possible to call
31812 @code{adainit} from the @code{DllMain} if your program has library level
31813 tasks because access to the @code{DllMain} entry point is serialized by
31814 the system (that is, only a single thread can execute ``through'' it at a
31815 time), which means that the GNAT run time will deadlock waiting for the
31816 newly created task to complete its initialization.
31818 @node Ada DLLs and Finalization
31819 @subsection Ada DLLs and Finalization
31820 @cindex DLLs and finalization
31823 When the services of an Ada DLL are no longer needed, the client code should
31824 invoke the DLL finalization routine, if available. The DLL finalization
31825 routine is in charge of releasing all resources acquired by the DLL. In the
31826 case of the Ada code contained in the DLL, this is achieved by calling
31827 routine @code{adafinal} generated by the GNAT binder
31828 (@pxref{Binding with Non-Ada Main Programs}).
31829 See the body of @code{Finalize_Api} for an
31830 example. As already pointed out the GNAT binder is automatically invoked
31831 during the DLL build process by the @code{gnatdll} tool
31832 (@pxref{Using gnatdll}).
31834 @node Creating a Spec for Ada DLLs
31835 @subsection Creating a Spec for Ada DLLs
31838 To use the services exported by the Ada DLL from another programming
31839 language (e.g.@: C), you have to translate the specs of the exported Ada
31840 entities in that language. For instance in the case of @code{API.dll},
31841 the corresponding C header file could look like:
31846 extern int *_imp__count;
31847 #define count (*_imp__count)
31848 int factorial (int);
31854 It is important to understand that when building an Ada DLL to be used by
31855 other Ada applications, you need two different specs for the packages
31856 contained in the DLL: one for building the DLL and the other for using
31857 the DLL. This is because the @code{DLL} calling convention is needed to
31858 use a variable defined in a DLL, but when building the DLL, the variable
31859 must have either the @code{Ada} or @code{C} calling convention. As an
31860 example consider a DLL comprising the following package @code{API}:
31862 @smallexample @c ada
31866 Count : Integer := 0;
31868 -- Remainder of the package omitted.
31875 After producing a DLL containing package @code{API}, the spec that
31876 must be used to import @code{API.Count} from Ada code outside of the
31879 @smallexample @c ada
31884 pragma Import (DLL, Count);
31890 @node Creating the Definition File
31891 @subsection Creating the Definition File
31894 The definition file is the last file needed to build the DLL. It lists
31895 the exported symbols. As an example, the definition file for a DLL
31896 containing only package @code{API} (where all the entities are exported
31897 with a @code{C} calling convention) is:
31912 If the @code{C} calling convention is missing from package @code{API},
31913 then the definition file contains the mangled Ada names of the above
31914 entities, which in this case are:
31923 api__initialize_api
31928 @node Using gnatdll
31929 @subsection Using @code{gnatdll}
31933 * gnatdll Example::
31934 * gnatdll behind the Scenes::
31939 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
31940 and non-Ada sources that make up your DLL have been compiled.
31941 @code{gnatdll} is actually in charge of two distinct tasks: build the
31942 static import library for the DLL and the actual DLL. The form of the
31943 @code{gnatdll} command is
31947 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
31952 where @var{list-of-files} is a list of ALI and object files. The object
31953 file list must be the exact list of objects corresponding to the non-Ada
31954 sources whose services are to be included in the DLL. The ALI file list
31955 must be the exact list of ALI files for the corresponding Ada sources
31956 whose services are to be included in the DLL. If @var{list-of-files} is
31957 missing, only the static import library is generated.
31960 You may specify any of the following switches to @code{gnatdll}:
31963 @item -a@ovar{address}
31964 @cindex @option{-a} (@code{gnatdll})
31965 Build a non-relocatable DLL at @var{address}. If @var{address} is not
31966 specified the default address @var{0x11000000} will be used. By default,
31967 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
31968 advise the reader to build relocatable DLL.
31970 @item -b @var{address}
31971 @cindex @option{-b} (@code{gnatdll})
31972 Set the relocatable DLL base address. By default the address is
31975 @item -bargs @var{opts}
31976 @cindex @option{-bargs} (@code{gnatdll})
31977 Binder options. Pass @var{opts} to the binder.
31979 @item -d @var{dllfile}
31980 @cindex @option{-d} (@code{gnatdll})
31981 @var{dllfile} is the name of the DLL. This switch must be present for
31982 @code{gnatdll} to do anything. The name of the generated import library is
31983 obtained algorithmically from @var{dllfile} as shown in the following
31984 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
31985 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
31986 by option @option{-e}) is obtained algorithmically from @var{dllfile}
31987 as shown in the following example:
31988 if @var{dllfile} is @code{xyz.dll}, the definition
31989 file used is @code{xyz.def}.
31991 @item -e @var{deffile}
31992 @cindex @option{-e} (@code{gnatdll})
31993 @var{deffile} is the name of the definition file.
31996 @cindex @option{-g} (@code{gnatdll})
31997 Generate debugging information. This information is stored in the object
31998 file and copied from there to the final DLL file by the linker,
31999 where it can be read by the debugger. You must use the
32000 @option{-g} switch if you plan on using the debugger or the symbolic
32004 @cindex @option{-h} (@code{gnatdll})
32005 Help mode. Displays @code{gnatdll} switch usage information.
32008 @cindex @option{-I} (@code{gnatdll})
32009 Direct @code{gnatdll} to search the @var{dir} directory for source and
32010 object files needed to build the DLL.
32011 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32014 @cindex @option{-k} (@code{gnatdll})
32015 Removes the @code{@@}@var{nn} suffix from the import library's exported
32016 names, but keeps them for the link names. You must specify this
32017 option if you want to use a @code{Stdcall} function in a DLL for which
32018 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32019 of the Windows NT DLL for example. This option has no effect when
32020 @option{-n} option is specified.
32022 @item -l @var{file}
32023 @cindex @option{-l} (@code{gnatdll})
32024 The list of ALI and object files used to build the DLL are listed in
32025 @var{file}, instead of being given in the command line. Each line in
32026 @var{file} contains the name of an ALI or object file.
32029 @cindex @option{-n} (@code{gnatdll})
32030 No Import. Do not create the import library.
32033 @cindex @option{-q} (@code{gnatdll})
32034 Quiet mode. Do not display unnecessary messages.
32037 @cindex @option{-v} (@code{gnatdll})
32038 Verbose mode. Display extra information.
32040 @item -largs @var{opts}
32041 @cindex @option{-largs} (@code{gnatdll})
32042 Linker options. Pass @var{opts} to the linker.
32045 @node gnatdll Example
32046 @subsubsection @code{gnatdll} Example
32049 As an example the command to build a relocatable DLL from @file{api.adb}
32050 once @file{api.adb} has been compiled and @file{api.def} created is
32053 $ gnatdll -d api.dll api.ali
32057 The above command creates two files: @file{libapi.dll.a} (the import
32058 library) and @file{api.dll} (the actual DLL). If you want to create
32059 only the DLL, just type:
32062 $ gnatdll -d api.dll -n api.ali
32066 Alternatively if you want to create just the import library, type:
32069 $ gnatdll -d api.dll
32072 @node gnatdll behind the Scenes
32073 @subsubsection @code{gnatdll} behind the Scenes
32076 This section details the steps involved in creating a DLL. @code{gnatdll}
32077 does these steps for you. Unless you are interested in understanding what
32078 goes on behind the scenes, you should skip this section.
32080 We use the previous example of a DLL containing the Ada package @code{API},
32081 to illustrate the steps necessary to build a DLL. The starting point is a
32082 set of objects that will make up the DLL and the corresponding ALI
32083 files. In the case of this example this means that @file{api.o} and
32084 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32089 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32090 the information necessary to generate relocation information for the
32096 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32101 In addition to the base file, the @command{gnatlink} command generates an
32102 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32103 asks @command{gnatlink} to generate the routines @code{DllMain} and
32104 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32105 is loaded into memory.
32108 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32109 export table (@file{api.exp}). The export table contains the relocation
32110 information in a form which can be used during the final link to ensure
32111 that the Windows loader is able to place the DLL anywhere in memory.
32115 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32116 --output-exp api.exp
32121 @code{gnatdll} builds the base file using the new export table. Note that
32122 @command{gnatbind} must be called once again since the binder generated file
32123 has been deleted during the previous call to @command{gnatlink}.
32128 $ gnatlink api -o api.jnk api.exp -mdll
32129 -Wl,--base-file,api.base
32134 @code{gnatdll} builds the new export table using the new base file and
32135 generates the DLL import library @file{libAPI.dll.a}.
32139 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32140 --output-exp api.exp --output-lib libAPI.a
32145 Finally @code{gnatdll} builds the relocatable DLL using the final export
32151 $ gnatlink api api.exp -o api.dll -mdll
32156 @node Using dlltool
32157 @subsubsection Using @code{dlltool}
32160 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32161 DLLs and static import libraries. This section summarizes the most
32162 common @code{dlltool} switches. The form of the @code{dlltool} command
32166 $ dlltool @ovar{switches}
32170 @code{dlltool} switches include:
32173 @item --base-file @var{basefile}
32174 @cindex @option{--base-file} (@command{dlltool})
32175 Read the base file @var{basefile} generated by the linker. This switch
32176 is used to create a relocatable DLL.
32178 @item --def @var{deffile}
32179 @cindex @option{--def} (@command{dlltool})
32180 Read the definition file.
32182 @item --dllname @var{name}
32183 @cindex @option{--dllname} (@command{dlltool})
32184 Gives the name of the DLL. This switch is used to embed the name of the
32185 DLL in the static import library generated by @code{dlltool} with switch
32186 @option{--output-lib}.
32189 @cindex @option{-k} (@command{dlltool})
32190 Kill @code{@@}@var{nn} from exported names
32191 (@pxref{Windows Calling Conventions}
32192 for a discussion about @code{Stdcall}-style symbols.
32195 @cindex @option{--help} (@command{dlltool})
32196 Prints the @code{dlltool} switches with a concise description.
32198 @item --output-exp @var{exportfile}
32199 @cindex @option{--output-exp} (@command{dlltool})
32200 Generate an export file @var{exportfile}. The export file contains the
32201 export table (list of symbols in the DLL) and is used to create the DLL.
32203 @item --output-lib @var{libfile}
32204 @cindex @option{--output-lib} (@command{dlltool})
32205 Generate a static import library @var{libfile}.
32208 @cindex @option{-v} (@command{dlltool})
32211 @item --as @var{assembler-name}
32212 @cindex @option{--as} (@command{dlltool})
32213 Use @var{assembler-name} as the assembler. The default is @code{as}.
32216 @node GNAT and Windows Resources
32217 @section GNAT and Windows Resources
32218 @cindex Resources, windows
32221 * Building Resources::
32222 * Compiling Resources::
32223 * Using Resources::
32227 Resources are an easy way to add Windows specific objects to your
32228 application. The objects that can be added as resources include:
32257 This section explains how to build, compile and use resources.
32259 @node Building Resources
32260 @subsection Building Resources
32261 @cindex Resources, building
32264 A resource file is an ASCII file. By convention resource files have an
32265 @file{.rc} extension.
32266 The easiest way to build a resource file is to use Microsoft tools
32267 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32268 @code{dlgedit.exe} to build dialogs.
32269 It is always possible to build an @file{.rc} file yourself by writing a
32272 It is not our objective to explain how to write a resource file. A
32273 complete description of the resource script language can be found in the
32274 Microsoft documentation.
32276 @node Compiling Resources
32277 @subsection Compiling Resources
32280 @cindex Resources, compiling
32283 This section describes how to build a GNAT-compatible (COFF) object file
32284 containing the resources. This is done using the Resource Compiler
32285 @code{windres} as follows:
32288 $ windres -i myres.rc -o myres.o
32292 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32293 file. You can specify an alternate preprocessor (usually named
32294 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32295 parameter. A list of all possible options may be obtained by entering
32296 the command @code{windres} @option{--help}.
32298 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32299 to produce a @file{.res} file (binary resource file). See the
32300 corresponding Microsoft documentation for further details. In this case
32301 you need to use @code{windres} to translate the @file{.res} file to a
32302 GNAT-compatible object file as follows:
32305 $ windres -i myres.res -o myres.o
32308 @node Using Resources
32309 @subsection Using Resources
32310 @cindex Resources, using
32313 To include the resource file in your program just add the
32314 GNAT-compatible object file for the resource(s) to the linker
32315 arguments. With @command{gnatmake} this is done by using the @option{-largs}
32319 $ gnatmake myprog -largs myres.o
32322 @node Debugging a DLL
32323 @section Debugging a DLL
32324 @cindex DLL debugging
32327 * Program and DLL Both Built with GCC/GNAT::
32328 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
32332 Debugging a DLL is similar to debugging a standard program. But
32333 we have to deal with two different executable parts: the DLL and the
32334 program that uses it. We have the following four possibilities:
32338 The program and the DLL are built with @code{GCC/GNAT}.
32340 The program is built with foreign tools and the DLL is built with
32343 The program is built with @code{GCC/GNAT} and the DLL is built with
32349 In this section we address only cases one and two above.
32350 There is no point in trying to debug
32351 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
32352 information in it. To do so you must use a debugger compatible with the
32353 tools suite used to build the DLL.
32355 @node Program and DLL Both Built with GCC/GNAT
32356 @subsection Program and DLL Both Built with GCC/GNAT
32359 This is the simplest case. Both the DLL and the program have @code{GDB}
32360 compatible debugging information. It is then possible to break anywhere in
32361 the process. Let's suppose here that the main procedure is named
32362 @code{ada_main} and that in the DLL there is an entry point named
32366 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
32367 program must have been built with the debugging information (see GNAT -g
32368 switch). Here are the step-by-step instructions for debugging it:
32371 @item Launch @code{GDB} on the main program.
32377 @item Start the program and stop at the beginning of the main procedure
32384 This step is required to be able to set a breakpoint inside the DLL. As long
32385 as the program is not run, the DLL is not loaded. This has the
32386 consequence that the DLL debugging information is also not loaded, so it is not
32387 possible to set a breakpoint in the DLL.
32389 @item Set a breakpoint inside the DLL
32392 (gdb) break ada_dll
32399 At this stage a breakpoint is set inside the DLL. From there on
32400 you can use the standard approach to debug the whole program
32401 (@pxref{Running and Debugging Ada Programs}).
32404 @c This used to work, probably because the DLLs were non-relocatable
32405 @c keep this section around until the problem is sorted out.
32407 To break on the @code{DllMain} routine it is not possible to follow
32408 the procedure above. At the time the program stop on @code{ada_main}
32409 the @code{DllMain} routine as already been called. Either you can use
32410 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
32413 @item Launch @code{GDB} on the main program.
32419 @item Load DLL symbols
32422 (gdb) add-sym api.dll
32425 @item Set a breakpoint inside the DLL
32428 (gdb) break ada_dll.adb:45
32431 Note that at this point it is not possible to break using the routine symbol
32432 directly as the program is not yet running. The solution is to break
32433 on the proper line (break in @file{ada_dll.adb} line 45).
32435 @item Start the program
32444 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
32445 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
32448 * Debugging the DLL Directly::
32449 * Attaching to a Running Process::
32453 In this case things are slightly more complex because it is not possible to
32454 start the main program and then break at the beginning to load the DLL and the
32455 associated DLL debugging information. It is not possible to break at the
32456 beginning of the program because there is no @code{GDB} debugging information,
32457 and therefore there is no direct way of getting initial control. This
32458 section addresses this issue by describing some methods that can be used
32459 to break somewhere in the DLL to debug it.
32462 First suppose that the main procedure is named @code{main} (this is for
32463 example some C code built with Microsoft Visual C) and that there is a
32464 DLL named @code{test.dll} containing an Ada entry point named
32468 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
32469 been built with debugging information (see GNAT -g option).
32471 @node Debugging the DLL Directly
32472 @subsubsection Debugging the DLL Directly
32476 Find out the executable starting address
32479 $ objdump --file-header main.exe
32482 The starting address is reported on the last line. For example:
32485 main.exe: file format pei-i386
32486 architecture: i386, flags 0x0000010a:
32487 EXEC_P, HAS_DEBUG, D_PAGED
32488 start address 0x00401010
32492 Launch the debugger on the executable.
32499 Set a breakpoint at the starting address, and launch the program.
32502 $ (gdb) break *0x00401010
32506 The program will stop at the given address.
32509 Set a breakpoint on a DLL subroutine.
32512 (gdb) break ada_dll.adb:45
32515 Or if you want to break using a symbol on the DLL, you need first to
32516 select the Ada language (language used by the DLL).
32519 (gdb) set language ada
32520 (gdb) break ada_dll
32524 Continue the program.
32531 This will run the program until it reaches the breakpoint that has been
32532 set. From that point you can use the standard way to debug a program
32533 as described in (@pxref{Running and Debugging Ada Programs}).
32538 It is also possible to debug the DLL by attaching to a running process.
32540 @node Attaching to a Running Process
32541 @subsubsection Attaching to a Running Process
32542 @cindex DLL debugging, attach to process
32545 With @code{GDB} it is always possible to debug a running process by
32546 attaching to it. It is possible to debug a DLL this way. The limitation
32547 of this approach is that the DLL must run long enough to perform the
32548 attach operation. It may be useful for instance to insert a time wasting
32549 loop in the code of the DLL to meet this criterion.
32553 @item Launch the main program @file{main.exe}.
32559 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
32560 that the process PID for @file{main.exe} is 208.
32568 @item Attach to the running process to be debugged.
32574 @item Load the process debugging information.
32577 (gdb) symbol-file main.exe
32580 @item Break somewhere in the DLL.
32583 (gdb) break ada_dll
32586 @item Continue process execution.
32595 This last step will resume the process execution, and stop at
32596 the breakpoint we have set. From there you can use the standard
32597 approach to debug a program as described in
32598 (@pxref{Running and Debugging Ada Programs}).
32600 @node Setting Stack Size from gnatlink
32601 @section Setting Stack Size from @command{gnatlink}
32604 It is possible to specify the program stack size at link time. On modern
32605 versions of Windows, starting with XP, this is mostly useful to set the size of
32606 the main stack (environment task). The other task stacks are set with pragma
32607 Storage_Size or with the @command{gnatbind -d} command.
32609 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
32610 reserve size of individual tasks, the link-time stack size applies to all
32611 tasks, and pragma Storage_Size has no effect.
32612 In particular, Stack Overflow checks are made against this
32613 link-time specified size.
32615 This setting can be done with
32616 @command{gnatlink} using either:
32620 @item using @option{-Xlinker} linker option
32623 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
32626 This sets the stack reserve size to 0x10000 bytes and the stack commit
32627 size to 0x1000 bytes.
32629 @item using @option{-Wl} linker option
32632 $ gnatlink hello -Wl,--stack=0x1000000
32635 This sets the stack reserve size to 0x1000000 bytes. Note that with
32636 @option{-Wl} option it is not possible to set the stack commit size
32637 because the coma is a separator for this option.
32641 @node Setting Heap Size from gnatlink
32642 @section Setting Heap Size from @command{gnatlink}
32645 Under Windows systems, it is possible to specify the program heap size from
32646 @command{gnatlink} using either:
32650 @item using @option{-Xlinker} linker option
32653 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
32656 This sets the heap reserve size to 0x10000 bytes and the heap commit
32657 size to 0x1000 bytes.
32659 @item using @option{-Wl} linker option
32662 $ gnatlink hello -Wl,--heap=0x1000000
32665 This sets the heap reserve size to 0x1000000 bytes. Note that with
32666 @option{-Wl} option it is not possible to set the heap commit size
32667 because the coma is a separator for this option.
32673 @c **********************************
32674 @c * GNU Free Documentation License *
32675 @c **********************************
32677 @c GNU Free Documentation License
32679 @node Index,,GNU Free Documentation License, Top
32685 @c Put table of contents at end, otherwise it precedes the "title page" in
32686 @c the .txt version
32687 @c Edit the pdf file to move the contents to the beginning, after the title