1 \input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
12 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
14 @setfilename gnat_ugn.info
17 Copyright @copyright{} 1995-2005, 2006, 2007, 2008 Free Software Foundation,
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.2 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, with no Front-Cover Texts and with no Back-Cover
24 Texts. A copy of the license is included in the section entitled
25 ``GNU Free Documentation License''.
28 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
30 @c GNAT_UGN Style Guide
32 @c 1. Always put a @noindent on the line before the first paragraph
33 @c after any of these commands:
45 @c 2. DO NOT use @example. Use @smallexample instead.
46 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
47 @c context. These can interfere with the readability of the texi
48 @c source file. Instead, use one of the following annotated
49 @c @smallexample commands, and preprocess the texi file with the
50 @c ada2texi tool (which generates appropriate highlighting):
51 @c @smallexample @c ada
52 @c @smallexample @c adanocomment
53 @c @smallexample @c projectfile
54 @c b) The "@c ada" markup will result in boldface for reserved words
55 @c and italics for comments
56 @c c) The "@c adanocomment" markup will result only in boldface for
57 @c reserved words (comments are left alone)
58 @c d) The "@c projectfile" markup is like "@c ada" except that the set
59 @c of reserved words include the new reserved words for project files
61 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
62 @c command must be preceded by two empty lines
64 @c 4. The @item command should be on a line of its own if it is in an
65 @c @itemize or @enumerate command.
67 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
70 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
71 @c cause the document build to fail.
73 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
74 @c This command inhibits page breaks, so long examples in a @cartouche can
75 @c lead to large, ugly patches of empty space on a page.
77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
78 @c or the unw flag set. The unw flag covers topics for both Unix and
81 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
84 @c This flag is used where the text refers to conditions that exist when the
85 @c text was entered into the document but which may change over time.
86 @c Update the setting for the flag, and (if necessary) the text surrounding,
87 @c the references to the flag, on future doc revisions:
88 @c search for @value{NOW}.
92 @set DEFAULTLANGUAGEVERSION Ada 2005
93 @set NONDEFAULTLANGUAGEVERSION Ada 95
100 @set PLATFORM OpenVMS
105 @c The ARG is an optional argument. To be used for macro arguments in
106 @c their documentation (@defmac).
108 @r{[}@var{\varname\}@r{]}@c
111 @settitle @value{EDITION} User's Guide @value{PLATFORM}
112 @dircategory GNU Ada tools
114 * @value{EDITION} User's Guide (gnat_ugn) @value{PLATFORM}
117 @include gcc-common.texi
119 @setchapternewpage odd
124 @title @value{EDITION} User's Guide
128 @titlefont{@i{@value{PLATFORM}}}
134 @subtitle GNAT, The GNU Ada Compiler
139 @vskip 0pt plus 1filll
146 @node Top, About This Guide, (dir), (dir)
147 @top @value{EDITION} User's Guide
150 @value{EDITION} User's Guide @value{PLATFORM}
153 GNAT, The GNU Ada Compiler@*
154 GCC version @value{version-GCC}@*
161 * Getting Started with GNAT::
162 * The GNAT Compilation Model::
163 * Compiling Using gcc::
164 * Binding Using gnatbind::
165 * Linking Using gnatlink::
166 * The GNAT Make Program gnatmake::
167 * Improving Performance::
168 * Renaming Files Using gnatchop::
169 * Configuration Pragmas::
170 * Handling Arbitrary File Naming Conventions Using gnatname::
171 * GNAT Project Manager::
172 * The Cross-Referencing Tools gnatxref and gnatfind::
173 * The GNAT Pretty-Printer gnatpp::
174 * The GNAT Metric Tool gnatmetric::
175 * File Name Krunching Using gnatkr::
176 * Preprocessing Using gnatprep::
178 * The GNAT Run-Time Library Builder gnatlbr::
180 * The GNAT Library Browser gnatls::
181 * Cleaning Up Using gnatclean::
183 * GNAT and Libraries::
184 * Using the GNU make Utility::
186 * Memory Management Issues::
187 * Stack Related Facilities::
188 * Verifying Properties Using gnatcheck::
189 * Creating Sample Bodies Using gnatstub::
190 * 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 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
2377 to specify both options.
2379 When using a gcc-based back end (in practice this means using any version
2380 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2381 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2382 Historically front end inlining was more extensive than the gcc back end
2383 inlining, but that is no longer the case.
2386 If an object file @file{O} depends on the proper body of a subunit through
2387 inlining or instantiation, it depends on the parent unit of the subunit.
2388 This means that any modification of the parent unit or one of its subunits
2389 affects the compilation of @file{O}.
2392 The object file for a parent unit depends on all its subunit body files.
2395 The previous two rules meant that for purposes of computing dependencies and
2396 recompilation, a body and all its subunits are treated as an indivisible whole.
2399 These rules are applied transitively: if unit @code{A} @code{with}'s
2400 unit @code{B}, whose elaboration calls an inlined procedure in package
2401 @code{C}, the object file for unit @code{A} will depend on the body of
2402 @code{C}, in file @file{c.adb}.
2404 The set of dependent files described by these rules includes all the
2405 files on which the unit is semantically dependent, as dictated by the
2406 Ada language standard. However, it is a superset of what the
2407 standard describes, because it includes generic, inline, and subunit
2410 An object file must be recreated by recompiling the corresponding source
2411 file if any of the source files on which it depends are modified. For
2412 example, if the @code{make} utility is used to control compilation,
2413 the rule for an Ada object file must mention all the source files on
2414 which the object file depends, according to the above definition.
2415 The determination of the necessary
2416 recompilations is done automatically when one uses @command{gnatmake}.
2419 @node The Ada Library Information Files
2420 @section The Ada Library Information Files
2421 @cindex Ada Library Information files
2422 @cindex @file{ALI} files
2425 Each compilation actually generates two output files. The first of these
2426 is the normal object file that has a @file{.o} extension. The second is a
2427 text file containing full dependency information. It has the same
2428 name as the source file, but an @file{.ali} extension.
2429 This file is known as the Ada Library Information (@file{ALI}) file.
2430 The following information is contained in the @file{ALI} file.
2434 Version information (indicates which version of GNAT was used to compile
2435 the unit(s) in question)
2438 Main program information (including priority and time slice settings,
2439 as well as the wide character encoding used during compilation).
2442 List of arguments used in the @command{gcc} command for the compilation
2445 Attributes of the unit, including configuration pragmas used, an indication
2446 of whether the compilation was successful, exception model used etc.
2449 A list of relevant restrictions applying to the unit (used for consistency)
2453 Categorization information (e.g.@: use of pragma @code{Pure}).
2456 Information on all @code{with}'ed units, including presence of
2457 @code{Elaborate} or @code{Elaborate_All} pragmas.
2460 Information from any @code{Linker_Options} pragmas used in the unit
2463 Information on the use of @code{Body_Version} or @code{Version}
2464 attributes in the unit.
2467 Dependency information. This is a list of files, together with
2468 time stamp and checksum information. These are files on which
2469 the unit depends in the sense that recompilation is required
2470 if any of these units are modified.
2473 Cross-reference data. Contains information on all entities referenced
2474 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2475 provide cross-reference information.
2480 For a full detailed description of the format of the @file{ALI} file,
2481 see the source of the body of unit @code{Lib.Writ}, contained in file
2482 @file{lib-writ.adb} in the GNAT compiler sources.
2484 @node Binding an Ada Program
2485 @section Binding an Ada Program
2488 When using languages such as C and C++, once the source files have been
2489 compiled the only remaining step in building an executable program
2490 is linking the object modules together. This means that it is possible to
2491 link an inconsistent version of a program, in which two units have
2492 included different versions of the same header.
2494 The rules of Ada do not permit such an inconsistent program to be built.
2495 For example, if two clients have different versions of the same package,
2496 it is illegal to build a program containing these two clients.
2497 These rules are enforced by the GNAT binder, which also determines an
2498 elaboration order consistent with the Ada rules.
2500 The GNAT binder is run after all the object files for a program have
2501 been created. It is given the name of the main program unit, and from
2502 this it determines the set of units required by the program, by reading the
2503 corresponding ALI files. It generates error messages if the program is
2504 inconsistent or if no valid order of elaboration exists.
2506 If no errors are detected, the binder produces a main program, in Ada by
2507 default, that contains calls to the elaboration procedures of those
2508 compilation unit that require them, followed by
2509 a call to the main program. This Ada program is compiled to generate the
2510 object file for the main program. The name of
2511 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2512 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2515 Finally, the linker is used to build the resulting executable program,
2516 using the object from the main program from the bind step as well as the
2517 object files for the Ada units of the program.
2519 @node Mixed Language Programming
2520 @section Mixed Language Programming
2521 @cindex Mixed Language Programming
2524 This section describes how to develop a mixed-language program,
2525 specifically one that comprises units in both Ada and C.
2528 * Interfacing to C::
2529 * Calling Conventions::
2532 @node Interfacing to C
2533 @subsection Interfacing to C
2535 Interfacing Ada with a foreign language such as C involves using
2536 compiler directives to import and/or export entity definitions in each
2537 language---using @code{extern} statements in C, for instance, and the
2538 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2539 A full treatment of these topics is provided in Appendix B, section 1
2540 of the Ada Reference Manual.
2542 There are two ways to build a program using GNAT that contains some Ada
2543 sources and some foreign language sources, depending on whether or not
2544 the main subprogram is written in Ada. Here is a source example with
2545 the main subprogram in Ada:
2551 void print_num (int num)
2553 printf ("num is %d.\n", num);
2559 /* num_from_Ada is declared in my_main.adb */
2560 extern int num_from_Ada;
2564 return num_from_Ada;
2568 @smallexample @c ada
2570 procedure My_Main is
2572 -- Declare then export an Integer entity called num_from_Ada
2573 My_Num : Integer := 10;
2574 pragma Export (C, My_Num, "num_from_Ada");
2576 -- Declare an Ada function spec for Get_Num, then use
2577 -- C function get_num for the implementation.
2578 function Get_Num return Integer;
2579 pragma Import (C, Get_Num, "get_num");
2581 -- Declare an Ada procedure spec for Print_Num, then use
2582 -- C function print_num for the implementation.
2583 procedure Print_Num (Num : Integer);
2584 pragma Import (C, Print_Num, "print_num");
2587 Print_Num (Get_Num);
2593 To build this example, first compile the foreign language files to
2594 generate object files:
2596 ^gcc -c file1.c^gcc -c FILE1.C^
2597 ^gcc -c file2.c^gcc -c FILE2.C^
2601 Then, compile the Ada units to produce a set of object files and ALI
2604 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2608 Run the Ada binder on the Ada main program:
2610 gnatbind my_main.ali
2614 Link the Ada main program, the Ada objects and the other language
2617 gnatlink my_main.ali file1.o file2.o
2621 The last three steps can be grouped in a single command:
2623 gnatmake my_main.adb -largs file1.o file2.o
2626 @cindex Binder output file
2628 If the main program is in a language other than Ada, then you may have
2629 more than one entry point into the Ada subsystem. You must use a special
2630 binder option to generate callable routines that initialize and
2631 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2632 Calls to the initialization and finalization routines must be inserted
2633 in the main program, or some other appropriate point in the code. The
2634 call to initialize the Ada units must occur before the first Ada
2635 subprogram is called, and the call to finalize the Ada units must occur
2636 after the last Ada subprogram returns. The binder will place the
2637 initialization and finalization subprograms into the
2638 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2639 sources. To illustrate, we have the following example:
2643 extern void adainit (void);
2644 extern void adafinal (void);
2645 extern int add (int, int);
2646 extern int sub (int, int);
2648 int main (int argc, char *argv[])
2654 /* Should print "21 + 7 = 28" */
2655 printf ("%d + %d = %d\n", a, b, add (a, b));
2656 /* Should print "21 - 7 = 14" */
2657 printf ("%d - %d = %d\n", a, b, sub (a, b));
2663 @smallexample @c ada
2666 function Add (A, B : Integer) return Integer;
2667 pragma Export (C, Add, "add");
2671 package body Unit1 is
2672 function Add (A, B : Integer) return Integer is
2680 function Sub (A, B : Integer) return Integer;
2681 pragma Export (C, Sub, "sub");
2685 package body Unit2 is
2686 function Sub (A, B : Integer) return Integer is
2695 The build procedure for this application is similar to the last
2696 example's. First, compile the foreign language files to generate object
2699 ^gcc -c main.c^gcc -c main.c^
2703 Next, compile the Ada units to produce a set of object files and ALI
2706 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2707 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2711 Run the Ada binder on every generated ALI file. Make sure to use the
2712 @option{-n} option to specify a foreign main program:
2714 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2718 Link the Ada main program, the Ada objects and the foreign language
2719 objects. You need only list the last ALI file here:
2721 gnatlink unit2.ali main.o -o exec_file
2724 This procedure yields a binary executable called @file{exec_file}.
2728 Depending on the circumstances (for example when your non-Ada main object
2729 does not provide symbol @code{main}), you may also need to instruct the
2730 GNAT linker not to include the standard startup objects by passing the
2731 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2733 @node Calling Conventions
2734 @subsection Calling Conventions
2735 @cindex Foreign Languages
2736 @cindex Calling Conventions
2737 GNAT follows standard calling sequence conventions and will thus interface
2738 to any other language that also follows these conventions. The following
2739 Convention identifiers are recognized by GNAT:
2742 @cindex Interfacing to Ada
2743 @cindex Other Ada compilers
2744 @cindex Convention Ada
2746 This indicates that the standard Ada calling sequence will be
2747 used and all Ada data items may be passed without any limitations in the
2748 case where GNAT is used to generate both the caller and callee. It is also
2749 possible to mix GNAT generated code and code generated by another Ada
2750 compiler. In this case, the data types should be restricted to simple
2751 cases, including primitive types. Whether complex data types can be passed
2752 depends on the situation. Probably it is safe to pass simple arrays, such
2753 as arrays of integers or floats. Records may or may not work, depending
2754 on whether both compilers lay them out identically. Complex structures
2755 involving variant records, access parameters, tasks, or protected types,
2756 are unlikely to be able to be passed.
2758 Note that in the case of GNAT running
2759 on a platform that supports HP Ada 83, a higher degree of compatibility
2760 can be guaranteed, and in particular records are layed out in an identical
2761 manner in the two compilers. Note also that if output from two different
2762 compilers is mixed, the program is responsible for dealing with elaboration
2763 issues. Probably the safest approach is to write the main program in the
2764 version of Ada other than GNAT, so that it takes care of its own elaboration
2765 requirements, and then call the GNAT-generated adainit procedure to ensure
2766 elaboration of the GNAT components. Consult the documentation of the other
2767 Ada compiler for further details on elaboration.
2769 However, it is not possible to mix the tasking run time of GNAT and
2770 HP Ada 83, All the tasking operations must either be entirely within
2771 GNAT compiled sections of the program, or entirely within HP Ada 83
2772 compiled sections of the program.
2774 @cindex Interfacing to Assembly
2775 @cindex Convention Assembler
2777 Specifies assembler as the convention. In practice this has the
2778 same effect as convention Ada (but is not equivalent in the sense of being
2779 considered the same convention).
2781 @cindex Convention Asm
2784 Equivalent to Assembler.
2786 @cindex Interfacing to COBOL
2787 @cindex Convention COBOL
2790 Data will be passed according to the conventions described
2791 in section B.4 of the Ada Reference Manual.
2794 @cindex Interfacing to C
2795 @cindex Convention C
2797 Data will be passed according to the conventions described
2798 in section B.3 of the Ada Reference Manual.
2800 A note on interfacing to a C ``varargs'' function:
2801 @findex C varargs function
2802 @cindex Interfacing to C varargs function
2803 @cindex varargs function interfaces
2807 In C, @code{varargs} allows a function to take a variable number of
2808 arguments. There is no direct equivalent in this to Ada. One
2809 approach that can be used is to create a C wrapper for each
2810 different profile and then interface to this C wrapper. For
2811 example, to print an @code{int} value using @code{printf},
2812 create a C function @code{printfi} that takes two arguments, a
2813 pointer to a string and an int, and calls @code{printf}.
2814 Then in the Ada program, use pragma @code{Import} to
2815 interface to @code{printfi}.
2818 It may work on some platforms to directly interface to
2819 a @code{varargs} function by providing a specific Ada profile
2820 for a particular call. However, this does not work on
2821 all platforms, since there is no guarantee that the
2822 calling sequence for a two argument normal C function
2823 is the same as for calling a @code{varargs} C function with
2824 the same two arguments.
2827 @cindex Convention Default
2832 @cindex Convention External
2839 @cindex Interfacing to C++
2840 @cindex Convention C++
2841 @item C_Plus_Plus (or CPP)
2842 This stands for C++. For most purposes this is identical to C.
2843 See the separate description of the specialized GNAT pragmas relating to
2844 C++ interfacing for further details.
2848 @cindex Interfacing to Fortran
2849 @cindex Convention Fortran
2851 Data will be passed according to the conventions described
2852 in section B.5 of the Ada Reference Manual.
2855 This applies to an intrinsic operation, as defined in the Ada
2856 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2857 this means that the body of the subprogram is provided by the compiler itself,
2858 usually by means of an efficient code sequence, and that the user does not
2859 supply an explicit body for it. In an application program, the pragma may
2860 be applied to the following sets of names:
2864 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2865 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2866 two formal parameters. The
2867 first one must be a signed integer type or a modular type with a binary
2868 modulus, and the second parameter must be of type Natural.
2869 The return type must be the same as the type of the first argument. The size
2870 of this type can only be 8, 16, 32, or 64.
2873 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2874 The corresponding operator declaration must have parameters and result type
2875 that have the same root numeric type (for example, all three are long_float
2876 types). This simplifies the definition of operations that use type checking
2877 to perform dimensional checks:
2879 @smallexample @c ada
2880 type Distance is new Long_Float;
2881 type Time is new Long_Float;
2882 type Velocity is new Long_Float;
2883 function "/" (D : Distance; T : Time)
2885 pragma Import (Intrinsic, "/");
2889 This common idiom is often programmed with a generic definition and an
2890 explicit body. The pragma makes it simpler to introduce such declarations.
2891 It incurs no overhead in compilation time or code size, because it is
2892 implemented as a single machine instruction.
2895 General subprogram entities, to bind an Ada subprogram declaration to
2896 a compiler builtin by name with back-ends where such interfaces are
2897 available. A typical example is the set of ``__builtin'' functions
2898 exposed by the GCC back-end, as in the following example:
2900 @smallexample @c ada
2901 function builtin_sqrt (F : Float) return Float;
2902 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2905 Most of the GCC builtins are accessible this way, and as for other
2906 import conventions (e.g. C), it is the user's responsibility to ensure
2907 that the Ada subprogram profile matches the underlying builtin
2915 @cindex Convention Stdcall
2917 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2918 and specifies that the @code{Stdcall} calling sequence will be used,
2919 as defined by the NT API. Nevertheless, to ease building
2920 cross-platform bindings this convention will be handled as a @code{C} calling
2921 convention on non-Windows platforms.
2924 @cindex Convention DLL
2926 This is equivalent to @code{Stdcall}.
2929 @cindex Convention Win32
2931 This is equivalent to @code{Stdcall}.
2935 @cindex Convention Stubbed
2937 This is a special convention that indicates that the compiler
2938 should provide a stub body that raises @code{Program_Error}.
2942 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2943 that can be used to parametrize conventions and allow additional synonyms
2944 to be specified. For example if you have legacy code in which the convention
2945 identifier Fortran77 was used for Fortran, you can use the configuration
2948 @smallexample @c ada
2949 pragma Convention_Identifier (Fortran77, Fortran);
2953 And from now on the identifier Fortran77 may be used as a convention
2954 identifier (for example in an @code{Import} pragma) with the same
2958 @node Building Mixed Ada & C++ Programs
2959 @section Building Mixed Ada and C++ Programs
2962 A programmer inexperienced with mixed-language development may find that
2963 building an application containing both Ada and C++ code can be a
2964 challenge. This section gives a few
2965 hints that should make this task easier. The first section addresses
2966 the differences between interfacing with C and interfacing with C++.
2968 looks into the delicate problem of linking the complete application from
2969 its Ada and C++ parts. The last section gives some hints on how the GNAT
2970 run-time library can be adapted in order to allow inter-language dispatching
2971 with a new C++ compiler.
2974 * Interfacing to C++::
2975 * Linking a Mixed C++ & Ada Program::
2976 * A Simple Example::
2977 * Interfacing with C++ at the Class Level::
2980 @node Interfacing to C++
2981 @subsection Interfacing to C++
2984 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2985 generating code that is compatible with the G++ Application Binary
2986 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2989 Interfacing can be done at 3 levels: simple data, subprograms, and
2990 classes. In the first two cases, GNAT offers a specific @code{Convention
2991 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2992 Usually, C++ mangles the names of subprograms, and currently, GNAT does
2993 not provide any help to solve the demangling problem. This problem can be
2994 addressed in two ways:
2997 by modifying the C++ code in order to force a C convention using
2998 the @code{extern "C"} syntax.
3001 by figuring out the mangled name and use it as the Link_Name argument of
3006 Interfacing at the class level can be achieved by using the GNAT specific
3007 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3008 gnat_rm, GNAT Reference Manual}, for additional information.
3010 @node Linking a Mixed C++ & Ada Program
3011 @subsection Linking a Mixed C++ & Ada Program
3014 Usually the linker of the C++ development system must be used to link
3015 mixed applications because most C++ systems will resolve elaboration
3016 issues (such as calling constructors on global class instances)
3017 transparently during the link phase. GNAT has been adapted to ease the
3018 use of a foreign linker for the last phase. Three cases can be
3023 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3024 The C++ linker can simply be called by using the C++ specific driver
3025 called @code{c++}. Note that this setup is not very common because it
3026 may involve recompiling the whole GCC tree from sources, which makes it
3027 harder to upgrade the compilation system for one language without
3028 destabilizing the other.
3033 $ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
3037 Using GNAT and G++ from two different GCC installations: If both
3038 compilers are on the @env{PATH}, the previous method may be used. It is
3039 important to note that environment variables such as
3040 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3041 @env{GCC_ROOT} will affect both compilers
3042 at the same time and may make one of the two compilers operate
3043 improperly if set during invocation of the wrong compiler. It is also
3044 very important that the linker uses the proper @file{libgcc.a} GCC
3045 library -- that is, the one from the C++ compiler installation. The
3046 implicit link command as suggested in the @command{gnatmake} command
3047 from the former example can be replaced by an explicit link command with
3048 the full-verbosity option in order to verify which library is used:
3051 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3053 If there is a problem due to interfering environment variables, it can
3054 be worked around by using an intermediate script. The following example
3055 shows the proper script to use when GNAT has not been installed at its
3056 default location and g++ has been installed at its default location:
3064 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3068 Using a non-GNU C++ compiler: The commands previously described can be
3069 used to insure that the C++ linker is used. Nonetheless, you need to add
3070 a few more parameters to the link command line, depending on the exception
3073 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3074 to the libgcc libraries are required:
3079 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3080 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3083 Where CC is the name of the non-GNU C++ compiler.
3085 If the @code{zero cost} exception mechanism is used, and the platform
3086 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3087 paths to more objects are required:
3092 CC `gcc -print-file-name=crtbegin.o` $* \
3093 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3094 `gcc -print-file-name=crtend.o`
3095 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3098 If the @code{zero cost} exception mechanism is used, and the platform
3099 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3100 Tru64 or AIX), the simple approach described above will not work and
3101 a pre-linking phase using GNAT will be necessary.
3105 @node A Simple Example
3106 @subsection A Simple Example
3108 The following example, provided as part of the GNAT examples, shows how
3109 to achieve procedural interfacing between Ada and C++ in both
3110 directions. The C++ class A has two methods. The first method is exported
3111 to Ada by the means of an extern C wrapper function. The second method
3112 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3113 a limited record with a layout comparable to the C++ class. The Ada
3114 subprogram, in turn, calls the C++ method. So, starting from the C++
3115 main program, the process passes back and forth between the two
3119 Here are the compilation commands:
3121 $ gnatmake -c simple_cpp_interface
3124 $ gnatbind -n simple_cpp_interface
3125 $ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
3126 -lstdc++ ex7.o cpp_main.o
3130 Here are the corresponding sources:
3138 void adainit (void);
3139 void adafinal (void);
3140 void method1 (A *t);
3162 class A : public Origin @{
3164 void method1 (void);
3165 void method2 (int v);
3175 extern "C" @{ void ada_method2 (A *t, int v);@}
3177 void A::method1 (void)
3180 printf ("in A::method1, a_value = %d \n",a_value);
3184 void A::method2 (int v)
3186 ada_method2 (this, v);
3187 printf ("in A::method2, a_value = %d \n",a_value);
3194 printf ("in A::A, a_value = %d \n",a_value);
3198 @smallexample @c ada
3200 package body Simple_Cpp_Interface is
3202 procedure Ada_Method2 (This : in out A; V : Integer) is
3208 end Simple_Cpp_Interface;
3211 package Simple_Cpp_Interface is
3214 Vptr : System.Address;
3218 pragma Convention (C, A);
3220 procedure Method1 (This : in out A);
3221 pragma Import (C, Method1);
3223 procedure Ada_Method2 (This : in out A; V : Integer);
3224 pragma Export (C, Ada_Method2);
3226 end Simple_Cpp_Interface;
3229 @node Interfacing with C++ at the Class Level
3230 @subsection Interfacing with C++ at the Class Level
3232 In this section we demonstrate the GNAT features for interfacing with
3233 C++ by means of an example making use of Ada 2005 abstract interface
3234 types. This example consists of a classification of animals; classes
3235 have been used to model our main classification of animals, and
3236 interfaces provide support for the management of secondary
3237 classifications. We first demonstrate a case in which the types and
3238 constructors are defined on the C++ side and imported from the Ada
3239 side, and latter the reverse case.
3241 The root of our derivation will be the @code{Animal} class, with a
3242 single private attribute (the @code{Age} of the animal) and two public
3243 primitives to set and get the value of this attribute.
3248 @b{virtual} void Set_Age (int New_Age);
3249 @b{virtual} int Age ();
3255 Abstract interface types are defined in C++ by means of classes with pure
3256 virtual functions and no data members. In our example we will use two
3257 interfaces that provide support for the common management of @code{Carnivore}
3258 and @code{Domestic} animals:
3261 @b{class} Carnivore @{
3263 @b{virtual} int Number_Of_Teeth () = 0;
3266 @b{class} Domestic @{
3268 @b{virtual void} Set_Owner (char* Name) = 0;
3272 Using these declarations, we can now say that a @code{Dog} is an animal that is
3273 both Carnivore and Domestic, that is:
3276 @b{class} Dog : Animal, Carnivore, Domestic @{
3278 @b{virtual} int Number_Of_Teeth ();
3279 @b{virtual} void Set_Owner (char* Name);
3281 Dog(); // Constructor
3288 In the following examples we will assume that the previous declarations are
3289 located in a file named @code{animals.h}. The following package demonstrates
3290 how to import these C++ declarations from the Ada side:
3292 @smallexample @c ada
3293 with Interfaces.C.Strings; use Interfaces.C.Strings;
3295 type Carnivore is interface;
3296 pragma Convention (C_Plus_Plus, Carnivore);
3297 function Number_Of_Teeth (X : Carnivore)
3298 return Natural is abstract;
3300 type Domestic is interface;
3301 pragma Convention (C_Plus_Plus, Set_Owner);
3303 (X : in out Domestic;
3304 Name : Chars_Ptr) is abstract;
3306 type Animal is tagged record
3309 pragma Import (C_Plus_Plus, Animal);
3311 procedure Set_Age (X : in out Animal; Age : Integer);
3312 pragma Import (C_Plus_Plus, Set_Age);
3314 function Age (X : Animal) return Integer;
3315 pragma Import (C_Plus_Plus, Age);
3317 type Dog is new Animal and Carnivore and Domestic with record
3318 Tooth_Count : Natural;
3319 Owner : String (1 .. 30);
3321 pragma Import (C_Plus_Plus, Dog);
3323 function Number_Of_Teeth (A : Dog) return Integer;
3324 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3326 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3327 pragma Import (C_Plus_Plus, Set_Owner);
3329 function New_Dog return Dog'Class;
3330 pragma CPP_Constructor (New_Dog);
3331 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3335 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3336 interfacing with these C++ classes is easy. The only requirement is that all
3337 the primitives and components must be declared exactly in the same order in
3340 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3341 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3342 the arguments to the called primitives will be the same as for C++. For the
3343 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3344 to indicate that they have been defined on the C++ side; this is required
3345 because the dispatch table associated with these tagged types will be built
3346 in the C++ side and therefore will not contain the predefined Ada primitives
3347 which Ada would otherwise expect.
3349 As the reader can see there is no need to indicate the C++ mangled names
3350 associated with each subprogram because it is assumed that all the calls to
3351 these primitives will be dispatching calls. The only exception is the
3352 constructor, which must be registered with the compiler by means of
3353 @code{pragma CPP_Constructor} and needs to provide its associated C++
3354 mangled name because the Ada compiler generates direct calls to it.
3356 With the above packages we can now declare objects of type Dog on the Ada side
3357 and dispatch calls to the corresponding subprograms on the C++ side. We can
3358 also extend the tagged type Dog with further fields and primitives, and
3359 override some of its C++ primitives on the Ada side. For example, here we have
3360 a type derivation defined on the Ada side that inherits all the dispatching
3361 primitives of the ancestor from the C++ side.
3364 @b{with} Animals; @b{use} Animals;
3365 @b{package} Vaccinated_Animals @b{is}
3366 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3367 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3368 @b{end} Vaccinated_Animals;
3371 It is important to note that, because of the ABI compatibility, the programmer
3372 does not need to add any further information to indicate either the object
3373 layout or the dispatch table entry associated with each dispatching operation.
3375 Now let us define all the types and constructors on the Ada side and export
3376 them to C++, using the same hierarchy of our previous example:
3378 @smallexample @c ada
3379 with Interfaces.C.Strings;
3380 use Interfaces.C.Strings;
3382 type Carnivore is interface;
3383 pragma Convention (C_Plus_Plus, Carnivore);
3384 function Number_Of_Teeth (X : Carnivore)
3385 return Natural is abstract;
3387 type Domestic is interface;
3388 pragma Convention (C_Plus_Plus, Set_Owner);
3390 (X : in out Domestic;
3391 Name : Chars_Ptr) is abstract;
3393 type Animal is tagged record
3396 pragma Convention (C_Plus_Plus, Animal);
3398 procedure Set_Age (X : in out Animal; Age : Integer);
3399 pragma Export (C_Plus_Plus, Set_Age);
3401 function Age (X : Animal) return Integer;
3402 pragma Export (C_Plus_Plus, Age);
3404 type Dog is new Animal and Carnivore and Domestic with record
3405 Tooth_Count : Natural;
3406 Owner : String (1 .. 30);
3408 pragma Convention (C_Plus_Plus, Dog);
3410 function Number_Of_Teeth (A : Dog) return Integer;
3411 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3413 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3414 pragma Export (C_Plus_Plus, Set_Owner);
3416 function New_Dog return Dog'Class;
3417 pragma Export (C_Plus_Plus, New_Dog);
3421 Compared with our previous example the only difference is the use of
3422 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3423 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3424 nothing else to be done; as explained above, the only requirement is that all
3425 the primitives and components are declared in exactly the same order.
3427 For completeness, let us see a brief C++ main program that uses the
3428 declarations available in @code{animals.h} (presented in our first example) to
3429 import and use the declarations from the Ada side, properly initializing and
3430 finalizing the Ada run-time system along the way:
3433 @b{#include} "animals.h"
3434 @b{#include} <iostream>
3435 @b{using namespace} std;
3437 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3438 void Check_Domestic (Domestic *obj) @{@dots{}@}
3439 void Check_Animal (Animal *obj) @{@dots{}@}
3440 void Check_Dog (Dog *obj) @{@dots{}@}
3443 void adainit (void);
3444 void adafinal (void);
3450 Dog *obj = new_dog(); // Ada constructor
3451 Check_Carnivore (obj); // Check secondary DT
3452 Check_Domestic (obj); // Check secondary DT
3453 Check_Animal (obj); // Check primary DT
3454 Check_Dog (obj); // Check primary DT
3459 adainit (); test(); adafinal ();
3464 @node Comparison between GNAT and C/C++ Compilation Models
3465 @section Comparison between GNAT and C/C++ Compilation Models
3468 The GNAT model of compilation is close to the C and C++ models. You can
3469 think of Ada specs as corresponding to header files in C. As in C, you
3470 don't need to compile specs; they are compiled when they are used. The
3471 Ada @code{with} is similar in effect to the @code{#include} of a C
3474 One notable difference is that, in Ada, you may compile specs separately
3475 to check them for semantic and syntactic accuracy. This is not always
3476 possible with C headers because they are fragments of programs that have
3477 less specific syntactic or semantic rules.
3479 The other major difference is the requirement for running the binder,
3480 which performs two important functions. First, it checks for
3481 consistency. In C or C++, the only defense against assembling
3482 inconsistent programs lies outside the compiler, in a makefile, for
3483 example. The binder satisfies the Ada requirement that it be impossible
3484 to construct an inconsistent program when the compiler is used in normal
3487 @cindex Elaboration order control
3488 The other important function of the binder is to deal with elaboration
3489 issues. There are also elaboration issues in C++ that are handled
3490 automatically. This automatic handling has the advantage of being
3491 simpler to use, but the C++ programmer has no control over elaboration.
3492 Where @code{gnatbind} might complain there was no valid order of
3493 elaboration, a C++ compiler would simply construct a program that
3494 malfunctioned at run time.
3497 @node Comparison between GNAT and Conventional Ada Library Models
3498 @section Comparison between GNAT and Conventional Ada Library Models
3501 This section is intended for Ada programmers who have
3502 used an Ada compiler implementing the traditional Ada library
3503 model, as described in the Ada Reference Manual.
3505 @cindex GNAT library
3506 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3507 source files themselves acts as the library. Compiling Ada programs does
3508 not generate any centralized information, but rather an object file and
3509 a ALI file, which are of interest only to the binder and linker.
3510 In a traditional system, the compiler reads information not only from
3511 the source file being compiled, but also from the centralized library.
3512 This means that the effect of a compilation depends on what has been
3513 previously compiled. In particular:
3517 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3518 to the version of the unit most recently compiled into the library.
3521 Inlining is effective only if the necessary body has already been
3522 compiled into the library.
3525 Compiling a unit may obsolete other units in the library.
3529 In GNAT, compiling one unit never affects the compilation of any other
3530 units because the compiler reads only source files. Only changes to source
3531 files can affect the results of a compilation. In particular:
3535 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3536 to the source version of the unit that is currently accessible to the
3541 Inlining requires the appropriate source files for the package or
3542 subprogram bodies to be available to the compiler. Inlining is always
3543 effective, independent of the order in which units are complied.
3546 Compiling a unit never affects any other compilations. The editing of
3547 sources may cause previous compilations to be out of date if they
3548 depended on the source file being modified.
3552 The most important result of these differences is that order of compilation
3553 is never significant in GNAT. There is no situation in which one is
3554 required to do one compilation before another. What shows up as order of
3555 compilation requirements in the traditional Ada library becomes, in
3556 GNAT, simple source dependencies; in other words, there is only a set
3557 of rules saying what source files must be present when a file is
3561 @node Placement of temporary files
3562 @section Placement of temporary files
3563 @cindex Temporary files (user control over placement)
3566 GNAT creates temporary files in the directory designated by the environment
3567 variable @env{TMPDIR}.
3568 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3569 for detailed information on how environment variables are resolved.
3570 For most users the easiest way to make use of this feature is to simply
3571 define @env{TMPDIR} as a job level logical name).
3572 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3573 for compiler temporary files, then you can include something like the
3574 following command in your @file{LOGIN.COM} file:
3577 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3581 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3582 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3583 designated by @env{TEMP}.
3584 If none of these environment variables are defined then GNAT uses the
3585 directory designated by the logical name @code{SYS$SCRATCH:}
3586 (by default the user's home directory). If all else fails
3587 GNAT uses the current directory for temporary files.
3590 @c *************************
3591 @node Compiling Using gcc
3592 @chapter Compiling Using @command{gcc}
3595 This chapter discusses how to compile Ada programs using the @command{gcc}
3596 command. It also describes the set of switches
3597 that can be used to control the behavior of the compiler.
3599 * Compiling Programs::
3600 * Switches for gcc::
3601 * Search Paths and the Run-Time Library (RTL)::
3602 * Order of Compilation Issues::
3606 @node Compiling Programs
3607 @section Compiling Programs
3610 The first step in creating an executable program is to compile the units
3611 of the program using the @command{gcc} command. You must compile the
3616 the body file (@file{.adb}) for a library level subprogram or generic
3620 the spec file (@file{.ads}) for a library level package or generic
3621 package that has no body
3624 the body file (@file{.adb}) for a library level package
3625 or generic package that has a body
3630 You need @emph{not} compile the following files
3635 the spec of a library unit which has a body
3642 because they are compiled as part of compiling related units. GNAT
3644 when the corresponding body is compiled, and subunits when the parent is
3647 @cindex cannot generate code
3648 If you attempt to compile any of these files, you will get one of the
3649 following error messages (where @var{fff} is the name of the file you compiled):
3652 cannot generate code for file @var{fff} (package spec)
3653 to check package spec, use -gnatc
3655 cannot generate code for file @var{fff} (missing subunits)
3656 to check parent unit, use -gnatc
3658 cannot generate code for file @var{fff} (subprogram spec)
3659 to check subprogram spec, use -gnatc
3661 cannot generate code for file @var{fff} (subunit)
3662 to check subunit, use -gnatc
3666 As indicated by the above error messages, if you want to submit
3667 one of these files to the compiler to check for correct semantics
3668 without generating code, then use the @option{-gnatc} switch.
3670 The basic command for compiling a file containing an Ada unit is
3673 $ gcc -c @ovar{switches} @file{file name}
3677 where @var{file name} is the name of the Ada file (usually
3679 @file{.ads} for a spec or @file{.adb} for a body).
3682 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3684 The result of a successful compilation is an object file, which has the
3685 same name as the source file but an extension of @file{.o} and an Ada
3686 Library Information (ALI) file, which also has the same name as the
3687 source file, but with @file{.ali} as the extension. GNAT creates these
3688 two output files in the current directory, but you may specify a source
3689 file in any directory using an absolute or relative path specification
3690 containing the directory information.
3693 @command{gcc} is actually a driver program that looks at the extensions of
3694 the file arguments and loads the appropriate compiler. For example, the
3695 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3696 These programs are in directories known to the driver program (in some
3697 configurations via environment variables you set), but need not be in
3698 your path. The @command{gcc} driver also calls the assembler and any other
3699 utilities needed to complete the generation of the required object
3702 It is possible to supply several file names on the same @command{gcc}
3703 command. This causes @command{gcc} to call the appropriate compiler for
3704 each file. For example, the following command lists three separate
3705 files to be compiled:
3708 $ gcc -c x.adb y.adb z.c
3712 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3713 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3714 The compiler generates three object files @file{x.o}, @file{y.o} and
3715 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3716 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3719 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3722 @node Switches for gcc
3723 @section Switches for @command{gcc}
3726 The @command{gcc} command accepts switches that control the
3727 compilation process. These switches are fully described in this section.
3728 First we briefly list all the switches, in alphabetical order, then we
3729 describe the switches in more detail in functionally grouped sections.
3731 More switches exist for GCC than those documented here, especially
3732 for specific targets. However, their use is not recommended as
3733 they may change code generation in ways that are incompatible with
3734 the Ada run-time library, or can cause inconsistencies between
3738 * Output and Error Message Control::
3739 * Warning Message Control::
3740 * Debugging and Assertion Control::
3741 * Validity Checking::
3744 * Using gcc for Syntax Checking::
3745 * Using gcc for Semantic Checking::
3746 * Compiling Different Versions of Ada::
3747 * Character Set Control::
3748 * File Naming Control::
3749 * Subprogram Inlining Control::
3750 * Auxiliary Output Control::
3751 * Debugging Control::
3752 * Exception Handling Control::
3753 * Units to Sources Mapping Files::
3754 * Integrated Preprocessing::
3755 * Code Generation Control::
3764 @cindex @option{-b} (@command{gcc})
3765 @item -b @var{target}
3766 Compile your program to run on @var{target}, which is the name of a
3767 system configuration. You must have a GNAT cross-compiler built if
3768 @var{target} is not the same as your host system.
3771 @cindex @option{-B} (@command{gcc})
3772 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3773 from @var{dir} instead of the default location. Only use this switch
3774 when multiple versions of the GNAT compiler are available.
3775 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3776 GNU Compiler Collection (GCC)}, for further details. You would normally
3777 use the @option{-b} or @option{-V} switch instead.
3780 @cindex @option{-c} (@command{gcc})
3781 Compile. Always use this switch when compiling Ada programs.
3783 Note: for some other languages when using @command{gcc}, notably in
3784 the case of C and C++, it is possible to use
3785 use @command{gcc} without a @option{-c} switch to
3786 compile and link in one step. In the case of GNAT, you
3787 cannot use this approach, because the binder must be run
3788 and @command{gcc} cannot be used to run the GNAT binder.
3792 @cindex @option{-fno-inline} (@command{gcc})
3793 Suppresses all back-end inlining, even if other optimization or inlining
3795 This includes suppression of inlining that results
3796 from the use of the pragma @code{Inline_Always}.
3797 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3798 are ignored, and @option{-gnatn} and @option{-gnatN} have no
3799 effect if this switch is present.
3801 @item -fno-inline-functions
3802 @cindex @option{-fno-inline-functions} (@command{gcc})
3803 Suppresses automatic inlining of small subprograms, which is enabled
3804 if @option{-O3} is used.
3806 @item -fno-inline-functions-called-once
3807 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
3808 Suppresses inlining of subprograms local to the unit and called once
3809 from within it, which is enabled if @option{-O1} is used.
3811 @item -fno-strict-aliasing
3812 @cindex @option{-fno-strict-aliasing} (@command{gcc})
3813 Causes the compiler to avoid assumptions regarding non-aliasing
3814 of objects of different types. See
3815 @ref{Optimization and Strict Aliasing} for details.
3818 @cindex @option{-fstack-check} (@command{gcc})
3819 Activates stack checking.
3820 See @ref{Stack Overflow Checking} for details.
3823 @cindex @option{-fstack-usage} (@command{gcc})
3824 Makes the compiler output stack usage information for the program, on a
3825 per-function basis. See @ref{Static Stack Usage Analysis} for details.
3827 @item -fcallgraph-info@r{[}=su@r{]}
3828 @cindex @option{-fcallgraph-info} (@command{gcc})
3829 Makes the compiler output callgraph information for the program, on a
3830 per-file basis. The information is generated in the VCG format. It can
3831 be decorated with stack-usage per-node information.
3834 @cindex @option{^-g^/DEBUG^} (@command{gcc})
3835 Generate debugging information. This information is stored in the object
3836 file and copied from there to the final executable file by the linker,
3837 where it can be read by the debugger. You must use the
3838 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
3841 @cindex @option{-gnat83} (@command{gcc})
3842 Enforce Ada 83 restrictions.
3845 @cindex @option{-gnat95} (@command{gcc})
3846 Enforce Ada 95 restrictions.
3849 @cindex @option{-gnat05} (@command{gcc})
3850 Allow full Ada 2005 features.
3853 @cindex @option{-gnata} (@command{gcc})
3854 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
3855 activated. Note that these pragmas can also be controlled using the
3856 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
3857 It also activates pragmas @code{Check}, @code{Precondition}, and
3858 @code{Postcondition}. Note that these pragmas can also be controlled
3859 using the configuration pragma @code{Check_Policy}.
3862 @cindex @option{-gnatA} (@command{gcc})
3863 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
3867 @cindex @option{-gnatb} (@command{gcc})
3868 Generate brief messages to @file{stderr} even if verbose mode set.
3871 @cindex @option{-gnatc} (@command{gcc})
3872 Check syntax and semantics only (no code generation attempted).
3875 @cindex @option{-gnatd} (@command{gcc})
3876 Specify debug options for the compiler. The string of characters after
3877 the @option{-gnatd} specify the specific debug options. The possible
3878 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
3879 compiler source file @file{debug.adb} for details of the implemented
3880 debug options. Certain debug options are relevant to applications
3881 programmers, and these are documented at appropriate points in this
3885 @cindex @option{-gnatD} (@command{gcc})
3886 Create expanded source files for source level debugging. This switch
3887 also suppress generation of cross-reference information
3888 (see @option{-gnatx}).
3890 @item -gnatec=@var{path}
3891 @cindex @option{-gnatec} (@command{gcc})
3892 Specify a configuration pragma file
3894 (the equal sign is optional)
3896 (@pxref{The Configuration Pragmas Files}).
3898 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
3899 @cindex @option{-gnateD} (@command{gcc})
3900 Defines a symbol, associated with @var{value}, for preprocessing.
3901 (@pxref{Integrated Preprocessing}).
3904 @cindex @option{-gnatef} (@command{gcc})
3905 Display full source path name in brief error messages.
3908 @cindex @option{-gnateG} (@command{gcc})
3909 Save result of preprocessing in a text file.
3911 @item -gnatem=@var{path}
3912 @cindex @option{-gnatem} (@command{gcc})
3913 Specify a mapping file
3915 (the equal sign is optional)
3917 (@pxref{Units to Sources Mapping Files}).
3919 @item -gnatep=@var{file}
3920 @cindex @option{-gnatep} (@command{gcc})
3921 Specify a preprocessing data file
3923 (the equal sign is optional)
3925 (@pxref{Integrated Preprocessing}).
3928 @cindex @option{-gnatE} (@command{gcc})
3929 Full dynamic elaboration checks.
3932 @cindex @option{-gnatf} (@command{gcc})
3933 Full errors. Multiple errors per line, all undefined references, do not
3934 attempt to suppress cascaded errors.
3937 @cindex @option{-gnatF} (@command{gcc})
3938 Externals names are folded to all uppercase.
3940 @item ^-gnatg^/GNAT_INTERNAL^
3941 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
3942 Internal GNAT implementation mode. This should not be used for
3943 applications programs, it is intended only for use by the compiler
3944 and its run-time library. For documentation, see the GNAT sources.
3945 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
3946 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
3947 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
3948 so that all standard warnings and all standard style options are turned on.
3949 All warnings and style error messages are treated as errors.
3952 @cindex @option{-gnatG} (@command{gcc})
3953 List generated expanded code in source form.
3955 @item ^-gnath^/HELP^
3956 @cindex @option{^-gnath^/HELP^} (@command{gcc})
3957 Output usage information. The output is written to @file{stdout}.
3959 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3960 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
3961 Identifier character set
3963 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3965 For details of the possible selections for @var{c},
3966 see @ref{Character Set Control}.
3968 @item ^-gnatI^/IGNORE_REP_CLAUSES^
3969 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
3970 Ignore representation clauses. When this switch is used, all
3971 representation clauses are treated as comments. This is useful
3972 when initially porting code where you want to ignore rep clause
3973 problems, and also for compiling foreign code (particularly
3977 @cindex @option{-gnatjnn} (@command{gcc})
3978 Reformat error messages to fit on nn character lines
3980 @item -gnatk=@var{n}
3981 @cindex @option{-gnatk} (@command{gcc})
3982 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
3985 @cindex @option{-gnatl} (@command{gcc})
3986 Output full source listing with embedded error messages.
3989 @cindex @option{-gnatL} (@command{gcc})
3990 Used in conjunction with -gnatG or -gnatD to intersperse original
3991 source lines (as comment lines with line numbers) in the expanded
3994 @item -gnatm=@var{n}
3995 @cindex @option{-gnatm} (@command{gcc})
3996 Limit number of detected error or warning messages to @var{n}
3997 where @var{n} is in the range 1..999_999. The default setting if
3998 no switch is given is 9999. Compilation is terminated if this
3999 limit is exceeded. The equal sign here is optional.
4002 @cindex @option{-gnatn} (@command{gcc})
4003 Activate inlining for subprograms for which
4004 pragma @code{inline} is specified. This inlining is performed
4005 by the GCC back-end.
4008 @cindex @option{-gnatN} (@command{gcc})
4009 Activate front end inlining for subprograms for which
4010 pragma @code{Inline} is specified. This inlining is performed
4011 by the front end and will be visible in the
4012 @option{-gnatG} output.
4013 In some cases, this has proved more effective than the back end
4014 inlining resulting from the use of
4017 @option{-gnatN} automatically implies
4018 @option{-gnatn} so it is not necessary
4019 to specify both options. There are a few cases that the back-end inlining
4020 catches that cannot be dealt with in the front-end.
4023 @cindex @option{-gnato} (@command{gcc})
4024 Enable numeric overflow checking (which is not normally enabled by
4025 default). Not that division by zero is a separate check that is not
4026 controlled by this switch (division by zero checking is on by default).
4029 @cindex @option{-gnatp} (@command{gcc})
4030 Suppress all checks.
4033 @cindex @option{-gnatP} (@command{gcc})
4034 Enable polling. This is required on some systems (notably Windows NT) to
4035 obtain asynchronous abort and asynchronous transfer of control capability.
4036 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4040 @cindex @option{-gnatq} (@command{gcc})
4041 Don't quit. Try semantics, even if parse errors.
4044 @cindex @option{-gnatQ} (@command{gcc})
4045 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4048 @cindex @option{-gnatr} (@command{gcc})
4049 Treat pragma Restrictions as Restriction_Warnings.
4051 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4052 @cindex @option{-gnatR} (@command{gcc})
4053 Output representation information for declared types and objects.
4056 @cindex @option{-gnats} (@command{gcc})
4060 @cindex @option{-gnatS} (@command{gcc})
4061 Print package Standard.
4064 @cindex @option{-gnatt} (@command{gcc})
4065 Generate tree output file.
4067 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4068 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4069 All compiler tables start at @var{nnn} times usual starting size.
4072 @cindex @option{-gnatu} (@command{gcc})
4073 List units for this compilation.
4076 @cindex @option{-gnatU} (@command{gcc})
4077 Tag all error messages with the unique string ``error:''
4080 @cindex @option{-gnatv} (@command{gcc})
4081 Verbose mode. Full error output with source lines to @file{stdout}.
4084 @cindex @option{-gnatV} (@command{gcc})
4085 Control level of validity checking. See separate section describing
4088 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4089 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4091 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4092 the exact warnings that
4093 are enabled or disabled (@pxref{Warning Message Control}).
4095 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4096 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4097 Wide character encoding method
4099 (@var{e}=n/h/u/s/e/8).
4102 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4106 @cindex @option{-gnatx} (@command{gcc})
4107 Suppress generation of cross-reference information.
4109 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4110 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4111 Enable built-in style checks (@pxref{Style Checking}).
4113 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4114 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4115 Distribution stub generation and compilation
4117 (@var{m}=r/c for receiver/caller stubs).
4120 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4121 to be generated and compiled).
4124 @item ^-I^/SEARCH=^@var{dir}
4125 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4127 Direct GNAT to search the @var{dir} directory for source files needed by
4128 the current compilation
4129 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4131 @item ^-I-^/NOCURRENT_DIRECTORY^
4132 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4134 Except for the source file named in the command line, do not look for source
4135 files in the directory containing the source file named in the command line
4136 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4140 @cindex @option{-mbig-switch} (@command{gcc})
4141 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4142 This standard gcc switch causes the compiler to use larger offsets in its
4143 jump table representation for @code{case} statements.
4144 This may result in less efficient code, but is sometimes necessary
4145 (for example on HP-UX targets)
4146 @cindex HP-UX and @option{-mbig-switch} option
4147 in order to compile large and/or nested @code{case} statements.
4150 @cindex @option{-o} (@command{gcc})
4151 This switch is used in @command{gcc} to redirect the generated object file
4152 and its associated ALI file. Beware of this switch with GNAT, because it may
4153 cause the object file and ALI file to have different names which in turn
4154 may confuse the binder and the linker.
4158 @cindex @option{-nostdinc} (@command{gcc})
4159 Inhibit the search of the default location for the GNAT Run Time
4160 Library (RTL) source files.
4163 @cindex @option{-nostdlib} (@command{gcc})
4164 Inhibit the search of the default location for the GNAT Run Time
4165 Library (RTL) ALI files.
4169 @cindex @option{-O} (@command{gcc})
4170 @var{n} controls the optimization level.
4174 No optimization, the default setting if no @option{-O} appears
4177 Normal optimization, the default if you specify @option{-O} without
4178 an operand. A good compromise between code quality and compilation
4182 Extensive optimization, may improve execution time, possibly at the cost of
4183 substantially increased compilation time.
4186 Same as @option{-O2}, and also includes inline expansion for small subprograms
4190 Optimize space usage
4194 See also @ref{Optimization Levels}.
4199 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4200 Equivalent to @option{/OPTIMIZE=NONE}.
4201 This is the default behavior in the absence of an @option{/OPTIMIZE}
4204 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4205 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4206 Selects the level of optimization for your program. The supported
4207 keywords are as follows:
4210 Perform most optimizations, including those that
4212 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4213 without keyword options.
4216 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4219 Perform some optimizations, but omit ones that are costly.
4222 Same as @code{SOME}.
4225 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4226 automatic inlining of small subprograms within a unit
4229 Try to unroll loops. This keyword may be specified together with
4230 any keyword above other than @code{NONE}. Loop unrolling
4231 usually, but not always, improves the performance of programs.
4234 Optimize space usage
4238 See also @ref{Optimization Levels}.
4242 @item -pass-exit-codes
4243 @cindex @option{-pass-exit-codes} (@command{gcc})
4244 Catch exit codes from the compiler and use the most meaningful as
4248 @item --RTS=@var{rts-path}
4249 @cindex @option{--RTS} (@command{gcc})
4250 Specifies the default location of the runtime library. Same meaning as the
4251 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4254 @cindex @option{^-S^/ASM^} (@command{gcc})
4255 ^Used in place of @option{-c} to^Used to^
4256 cause the assembler source file to be
4257 generated, using @file{^.s^.S^} as the extension,
4258 instead of the object file.
4259 This may be useful if you need to examine the generated assembly code.
4261 @item ^-fverbose-asm^/VERBOSE_ASM^
4262 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4263 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4264 to cause the generated assembly code file to be annotated with variable
4265 names, making it significantly easier to follow.
4268 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4269 Show commands generated by the @command{gcc} driver. Normally used only for
4270 debugging purposes or if you need to be sure what version of the
4271 compiler you are executing.
4275 @cindex @option{-V} (@command{gcc})
4276 Execute @var{ver} version of the compiler. This is the @command{gcc}
4277 version, not the GNAT version.
4280 @item ^-w^/NO_BACK_END_WARNINGS^
4281 @cindex @option{-w} (@command{gcc})
4282 Turn off warnings generated by the back end of the compiler. Use of
4283 this switch also causes the default for front end warnings to be set
4284 to suppress (as though @option{-gnatws} had appeared at the start of
4290 @c Combining qualifiers does not work on VMS
4291 You may combine a sequence of GNAT switches into a single switch. For
4292 example, the combined switch
4294 @cindex Combining GNAT switches
4300 is equivalent to specifying the following sequence of switches:
4303 -gnato -gnatf -gnati3
4308 The following restrictions apply to the combination of switches
4313 The switch @option{-gnatc} if combined with other switches must come
4314 first in the string.
4317 The switch @option{-gnats} if combined with other switches must come
4318 first in the string.
4322 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4323 may not be combined with any other switches.
4327 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4328 switch), then all further characters in the switch are interpreted
4329 as style modifiers (see description of @option{-gnaty}).
4332 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4333 switch), then all further characters in the switch are interpreted
4334 as debug flags (see description of @option{-gnatd}).
4337 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4338 switch), then all further characters in the switch are interpreted
4339 as warning mode modifiers (see description of @option{-gnatw}).
4342 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4343 switch), then all further characters in the switch are interpreted
4344 as validity checking options (see description of @option{-gnatV}).
4348 @node Output and Error Message Control
4349 @subsection Output and Error Message Control
4353 The standard default format for error messages is called ``brief format''.
4354 Brief format messages are written to @file{stderr} (the standard error
4355 file) and have the following form:
4358 e.adb:3:04: Incorrect spelling of keyword "function"
4359 e.adb:4:20: ";" should be "is"
4363 The first integer after the file name is the line number in the file,
4364 and the second integer is the column number within the line.
4366 @code{GPS} can parse the error messages
4367 and point to the referenced character.
4369 The following switches provide control over the error message
4375 @cindex @option{-gnatv} (@command{gcc})
4378 The v stands for verbose.
4380 The effect of this setting is to write long-format error
4381 messages to @file{stdout} (the standard output file.
4382 The same program compiled with the
4383 @option{-gnatv} switch would generate:
4387 3. funcion X (Q : Integer)
4389 >>> Incorrect spelling of keyword "function"
4392 >>> ";" should be "is"
4397 The vertical bar indicates the location of the error, and the @samp{>>>}
4398 prefix can be used to search for error messages. When this switch is
4399 used the only source lines output are those with errors.
4402 @cindex @option{-gnatl} (@command{gcc})
4404 The @code{l} stands for list.
4406 This switch causes a full listing of
4407 the file to be generated. In the case where a body is
4408 compiled, the corresponding spec is also listed, along
4409 with any subunits. Typical output from compiling a package
4410 body @file{p.adb} might look like:
4412 @smallexample @c ada
4416 1. package body p is
4418 3. procedure a is separate;
4429 2. pragma Elaborate_Body
4453 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4454 standard output is redirected, a brief summary is written to
4455 @file{stderr} (standard error) giving the number of error messages and
4456 warning messages generated.
4458 @item -^gnatl^OUTPUT_FILE^=file
4459 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4460 This has the same effect as @option{-gnatl} except that the output is
4461 written to a file instead of to standard output. If the given name
4462 @file{fname} does not start with a period, then it is the full name
4463 of the file to be written. If @file{fname} is an extension, it is
4464 appended to the name of the file being compiled. For example, if
4465 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4466 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4469 @cindex @option{-gnatU} (@command{gcc})
4470 This switch forces all error messages to be preceded by the unique
4471 string ``error:''. This means that error messages take a few more
4472 characters in space, but allows easy searching for and identification
4476 @cindex @option{-gnatb} (@command{gcc})
4478 The @code{b} stands for brief.
4480 This switch causes GNAT to generate the
4481 brief format error messages to @file{stderr} (the standard error
4482 file) as well as the verbose
4483 format message or full listing (which as usual is written to
4484 @file{stdout} (the standard output file).
4486 @item -gnatm=@var{n}
4487 @cindex @option{-gnatm} (@command{gcc})
4489 The @code{m} stands for maximum.
4491 @var{n} is a decimal integer in the
4492 range of 1 to 999 and limits the number of error messages to be
4493 generated. For example, using @option{-gnatm2} might yield
4496 e.adb:3:04: Incorrect spelling of keyword "function"
4497 e.adb:5:35: missing ".."
4498 fatal error: maximum errors reached
4499 compilation abandoned
4503 Note that the equal sign is optional, so the switches
4504 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4507 @cindex @option{-gnatf} (@command{gcc})
4508 @cindex Error messages, suppressing
4510 The @code{f} stands for full.
4512 Normally, the compiler suppresses error messages that are likely to be
4513 redundant. This switch causes all error
4514 messages to be generated. In particular, in the case of
4515 references to undefined variables. If a given variable is referenced
4516 several times, the normal format of messages is
4518 e.adb:7:07: "V" is undefined (more references follow)
4522 where the parenthetical comment warns that there are additional
4523 references to the variable @code{V}. Compiling the same program with the
4524 @option{-gnatf} switch yields
4527 e.adb:7:07: "V" is undefined
4528 e.adb:8:07: "V" is undefined
4529 e.adb:8:12: "V" is undefined
4530 e.adb:8:16: "V" is undefined
4531 e.adb:9:07: "V" is undefined
4532 e.adb:9:12: "V" is undefined
4536 The @option{-gnatf} switch also generates additional information for
4537 some error messages. Some examples are:
4541 Full details on entities not available in high integrity mode
4543 Details on possibly non-portable unchecked conversion
4545 List possible interpretations for ambiguous calls
4547 Additional details on incorrect parameters
4551 @cindex @option{-gnatjnn} (@command{gcc})
4552 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4553 with continuation lines are treated as though the continuation lines were
4554 separate messages (and so a warning with two continuation lines counts as
4555 three warnings, and is listed as three separate messages).
4557 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4558 messages are output in a different manner. A message and all its continuation
4559 lines are treated as a unit, and count as only one warning or message in the
4560 statistics totals. Furthermore, the message is reformatted so that no line
4561 is longer than nn characters.
4564 @cindex @option{-gnatq} (@command{gcc})
4566 The @code{q} stands for quit (really ``don't quit'').
4568 In normal operation mode, the compiler first parses the program and
4569 determines if there are any syntax errors. If there are, appropriate
4570 error messages are generated and compilation is immediately terminated.
4572 GNAT to continue with semantic analysis even if syntax errors have been
4573 found. This may enable the detection of more errors in a single run. On
4574 the other hand, the semantic analyzer is more likely to encounter some
4575 internal fatal error when given a syntactically invalid tree.
4578 @cindex @option{-gnatQ} (@command{gcc})
4579 In normal operation mode, the @file{ALI} file is not generated if any
4580 illegalities are detected in the program. The use of @option{-gnatQ} forces
4581 generation of the @file{ALI} file. This file is marked as being in
4582 error, so it cannot be used for binding purposes, but it does contain
4583 reasonably complete cross-reference information, and thus may be useful
4584 for use by tools (e.g., semantic browsing tools or integrated development
4585 environments) that are driven from the @file{ALI} file. This switch
4586 implies @option{-gnatq}, since the semantic phase must be run to get a
4587 meaningful ALI file.
4589 In addition, if @option{-gnatt} is also specified, then the tree file is
4590 generated even if there are illegalities. It may be useful in this case
4591 to also specify @option{-gnatq} to ensure that full semantic processing
4592 occurs. The resulting tree file can be processed by ASIS, for the purpose
4593 of providing partial information about illegal units, but if the error
4594 causes the tree to be badly malformed, then ASIS may crash during the
4597 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4598 being in error, @command{gnatmake} will attempt to recompile the source when it
4599 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4601 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4602 since ALI files are never generated if @option{-gnats} is set.
4606 @node Warning Message Control
4607 @subsection Warning Message Control
4608 @cindex Warning messages
4610 In addition to error messages, which correspond to illegalities as defined
4611 in the Ada Reference Manual, the compiler detects two kinds of warning
4614 First, the compiler considers some constructs suspicious and generates a
4615 warning message to alert you to a possible error. Second, if the
4616 compiler detects a situation that is sure to raise an exception at
4617 run time, it generates a warning message. The following shows an example
4618 of warning messages:
4620 e.adb:4:24: warning: creation of object may raise Storage_Error
4621 e.adb:10:17: warning: static value out of range
4622 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4626 GNAT considers a large number of situations as appropriate
4627 for the generation of warning messages. As always, warnings are not
4628 definite indications of errors. For example, if you do an out-of-range
4629 assignment with the deliberate intention of raising a
4630 @code{Constraint_Error} exception, then the warning that may be
4631 issued does not indicate an error. Some of the situations for which GNAT
4632 issues warnings (at least some of the time) are given in the following
4633 list. This list is not complete, and new warnings are often added to
4634 subsequent versions of GNAT. The list is intended to give a general idea
4635 of the kinds of warnings that are generated.
4639 Possible infinitely recursive calls
4642 Out-of-range values being assigned
4645 Possible order of elaboration problems
4648 Assertions (pragma Assert) that are sure to fail
4654 Address clauses with possibly unaligned values, or where an attempt is
4655 made to overlay a smaller variable with a larger one.
4658 Fixed-point type declarations with a null range
4661 Direct_IO or Sequential_IO instantiated with a type that has access values
4664 Variables that are never assigned a value
4667 Variables that are referenced before being initialized
4670 Task entries with no corresponding @code{accept} statement
4673 Duplicate accepts for the same task entry in a @code{select}
4676 Objects that take too much storage
4679 Unchecked conversion between types of differing sizes
4682 Missing @code{return} statement along some execution path in a function
4685 Incorrect (unrecognized) pragmas
4688 Incorrect external names
4691 Allocation from empty storage pool
4694 Potentially blocking operation in protected type
4697 Suspicious parenthesization of expressions
4700 Mismatching bounds in an aggregate
4703 Attempt to return local value by reference
4706 Premature instantiation of a generic body
4709 Attempt to pack aliased components
4712 Out of bounds array subscripts
4715 Wrong length on string assignment
4718 Violations of style rules if style checking is enabled
4721 Unused @code{with} clauses
4724 @code{Bit_Order} usage that does not have any effect
4727 @code{Standard.Duration} used to resolve universal fixed expression
4730 Dereference of possibly null value
4733 Declaration that is likely to cause storage error
4736 Internal GNAT unit @code{with}'ed by application unit
4739 Values known to be out of range at compile time
4742 Unreferenced labels and variables
4745 Address overlays that could clobber memory
4748 Unexpected initialization when address clause present
4751 Bad alignment for address clause
4754 Useless type conversions
4757 Redundant assignment statements and other redundant constructs
4760 Useless exception handlers
4763 Accidental hiding of name by child unit
4766 Access before elaboration detected at compile time
4769 A range in a @code{for} loop that is known to be null or might be null
4774 The following section lists compiler switches that are available
4775 to control the handling of warning messages. It is also possible
4776 to exercise much finer control over what warnings are issued and
4777 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
4778 gnat_rm, GNAT Reference manual}.
4783 @emph{Activate all optional errors.}
4784 @cindex @option{-gnatwa} (@command{gcc})
4785 This switch activates most optional warning messages, see remaining list
4786 in this section for details on optional warning messages that can be
4787 individually controlled. The warnings that are not turned on by this
4789 @option{-gnatwd} (implicit dereferencing),
4790 @option{-gnatwh} (hiding),
4791 @option{-gnatwl} (elaboration warnings),
4792 @option{-gnatw.o} (warn on values set by out parameters ignored)
4793 and @option{-gnatwt} (tracking of deleted conditional code).
4794 All other optional warnings are turned on.
4797 @emph{Suppress all optional errors.}
4798 @cindex @option{-gnatwA} (@command{gcc})
4799 This switch suppresses all optional warning messages, see remaining list
4800 in this section for details on optional warning messages that can be
4801 individually controlled.
4804 @emph{Activate warnings on failing assertions.}
4805 @cindex @option{-gnatw.a} (@command{gcc})
4806 @cindex Assert failures
4807 This switch activates warnings for assertions where the compiler can tell at
4808 compile time that the assertion will fail. Note that this warning is given
4809 even if assertions are disabled. The default is that such warnings are
4813 @emph{Suppress warnings on failing assertions.}
4814 @cindex @option{-gnatw.A} (@command{gcc})
4815 @cindex Assert failures
4816 This switch suppresses warnings for assertions where the compiler can tell at
4817 compile time that the assertion will fail.
4820 @emph{Activate warnings on bad fixed values.}
4821 @cindex @option{-gnatwb} (@command{gcc})
4822 @cindex Bad fixed values
4823 @cindex Fixed-point Small value
4825 This switch activates warnings for static fixed-point expressions whose
4826 value is not an exact multiple of Small. Such values are implementation
4827 dependent, since an implementation is free to choose either of the multiples
4828 that surround the value. GNAT always chooses the closer one, but this is not
4829 required behavior, and it is better to specify a value that is an exact
4830 multiple, ensuring predictable execution. The default is that such warnings
4834 @emph{Suppress warnings on bad fixed values.}
4835 @cindex @option{-gnatwB} (@command{gcc})
4836 This switch suppresses warnings for static fixed-point expressions whose
4837 value is not an exact multiple of Small.
4840 @emph{Activate warnings on biased representation.}
4841 @cindex @option{-gnatw.b} (@command{gcc})
4842 @cindex Biased representation
4843 This switch activates warnings when a size clause, value size clause, component
4844 clause, or component size clause forces the use of biased representation for an
4845 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
4846 to represent 10/11). The default is that such warnings are generated.
4849 @emph{Suppress warnings on biased representation.}
4850 @cindex @option{-gnatwB} (@command{gcc})
4851 This switch suppresses warnings for representation clauses that force the use
4852 of biased representation.
4855 @emph{Activate warnings on conditionals.}
4856 @cindex @option{-gnatwc} (@command{gcc})
4857 @cindex Conditionals, constant
4858 This switch activates warnings for conditional expressions used in
4859 tests that are known to be True or False at compile time. The default
4860 is that such warnings are not generated.
4861 Note that this warning does
4862 not get issued for the use of boolean variables or constants whose
4863 values are known at compile time, since this is a standard technique
4864 for conditional compilation in Ada, and this would generate too many
4865 false positive warnings.
4867 This warning option also activates a special test for comparisons using
4868 the operators ``>='' and`` <=''.
4869 If the compiler can tell that only the equality condition is possible,
4870 then it will warn that the ``>'' or ``<'' part of the test
4871 is useless and that the operator could be replaced by ``=''.
4872 An example would be comparing a @code{Natural} variable <= 0.
4874 This warning option also generates warnings if
4875 one or both tests is optimized away in a membership test for integer
4876 values if the result can be determined at compile time. Range tests on
4877 enumeration types are not included, since it is common for such tests
4878 to include an end point.
4880 This warning can also be turned on using @option{-gnatwa}.
4883 @emph{Suppress warnings on conditionals.}
4884 @cindex @option{-gnatwC} (@command{gcc})
4885 This switch suppresses warnings for conditional expressions used in
4886 tests that are known to be True or False at compile time.
4889 @emph{Activate warnings on missing component clauses.}
4890 @cindex @option{-gnatw.c} (@command{gcc})
4891 @cindex Component clause, missing
4892 This switch activates warnings for record components where a record
4893 representation clause is present and has component clauses for the
4894 majority, but not all, of the components. A warning is given for each
4895 component for which no component clause is present.
4897 This warning can also be turned on using @option{-gnatwa}.
4900 @emph{Suppress warnings on missing component clauses.}
4901 @cindex @option{-gnatwC} (@command{gcc})
4902 This switch suppresses warnings for record components that are
4903 missing a component clause in the situation described above.
4906 @emph{Activate warnings on implicit dereferencing.}
4907 @cindex @option{-gnatwd} (@command{gcc})
4908 If this switch is set, then the use of a prefix of an access type
4909 in an indexed component, slice, or selected component without an
4910 explicit @code{.all} will generate a warning. With this warning
4911 enabled, access checks occur only at points where an explicit
4912 @code{.all} appears in the source code (assuming no warnings are
4913 generated as a result of this switch). The default is that such
4914 warnings are not generated.
4915 Note that @option{-gnatwa} does not affect the setting of
4916 this warning option.
4919 @emph{Suppress warnings on implicit dereferencing.}
4920 @cindex @option{-gnatwD} (@command{gcc})
4921 @cindex Implicit dereferencing
4922 @cindex Dereferencing, implicit
4923 This switch suppresses warnings for implicit dereferences in
4924 indexed components, slices, and selected components.
4927 @emph{Treat warnings as errors.}
4928 @cindex @option{-gnatwe} (@command{gcc})
4929 @cindex Warnings, treat as error
4930 This switch causes warning messages to be treated as errors.
4931 The warning string still appears, but the warning messages are counted
4932 as errors, and prevent the generation of an object file.
4935 @emph{Activate every optional warning}
4936 @cindex @option{-gnatw.e} (@command{gcc})
4937 @cindex Warnings, activate every optional warning
4938 This switch activates all optional warnings, including those which
4939 are not activated by @code{-gnatwa}.
4942 @emph{Activate warnings on unreferenced formals.}
4943 @cindex @option{-gnatwf} (@command{gcc})
4944 @cindex Formals, unreferenced
4945 This switch causes a warning to be generated if a formal parameter
4946 is not referenced in the body of the subprogram. This warning can
4947 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
4948 default is that these warnings are not generated.
4951 @emph{Suppress warnings on unreferenced formals.}
4952 @cindex @option{-gnatwF} (@command{gcc})
4953 This switch suppresses warnings for unreferenced formal
4954 parameters. Note that the
4955 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4956 effect of warning on unreferenced entities other than subprogram
4960 @emph{Activate warnings on unrecognized pragmas.}
4961 @cindex @option{-gnatwg} (@command{gcc})
4962 @cindex Pragmas, unrecognized
4963 This switch causes a warning to be generated if an unrecognized
4964 pragma is encountered. Apart from issuing this warning, the
4965 pragma is ignored and has no effect. This warning can
4966 also be turned on using @option{-gnatwa}. The default
4967 is that such warnings are issued (satisfying the Ada Reference
4968 Manual requirement that such warnings appear).
4971 @emph{Suppress warnings on unrecognized pragmas.}
4972 @cindex @option{-gnatwG} (@command{gcc})
4973 This switch suppresses warnings for unrecognized pragmas.
4976 @emph{Activate warnings on hiding.}
4977 @cindex @option{-gnatwh} (@command{gcc})
4978 @cindex Hiding of Declarations
4979 This switch activates warnings on hiding declarations.
4980 A declaration is considered hiding
4981 if it is for a non-overloadable entity, and it declares an entity with the
4982 same name as some other entity that is directly or use-visible. The default
4983 is that such warnings are not generated.
4984 Note that @option{-gnatwa} does not affect the setting of this warning option.
4987 @emph{Suppress warnings on hiding.}
4988 @cindex @option{-gnatwH} (@command{gcc})
4989 This switch suppresses warnings on hiding declarations.
4992 @emph{Activate warnings on implementation units.}
4993 @cindex @option{-gnatwi} (@command{gcc})
4994 This switch activates warnings for a @code{with} of an internal GNAT
4995 implementation unit, defined as any unit from the @code{Ada},
4996 @code{Interfaces}, @code{GNAT},
4997 ^^@code{DEC},^ or @code{System}
4998 hierarchies that is not
4999 documented in either the Ada Reference Manual or the GNAT
5000 Programmer's Reference Manual. Such units are intended only
5001 for internal implementation purposes and should not be @code{with}'ed
5002 by user programs. The default is that such warnings are generated
5003 This warning can also be turned on using @option{-gnatwa}.
5006 @emph{Disable warnings on implementation units.}
5007 @cindex @option{-gnatwI} (@command{gcc})
5008 This switch disables warnings for a @code{with} of an internal GNAT
5009 implementation unit.
5012 @emph{Activate warnings on obsolescent features (Annex J).}
5013 @cindex @option{-gnatwj} (@command{gcc})
5014 @cindex Features, obsolescent
5015 @cindex Obsolescent features
5016 If this warning option is activated, then warnings are generated for
5017 calls to subprograms marked with @code{pragma Obsolescent} and
5018 for use of features in Annex J of the Ada Reference Manual. In the
5019 case of Annex J, not all features are flagged. In particular use
5020 of the renamed packages (like @code{Text_IO}) and use of package
5021 @code{ASCII} are not flagged, since these are very common and
5022 would generate many annoying positive warnings. The default is that
5023 such warnings are not generated. This warning is also turned on by
5024 the use of @option{-gnatwa}.
5026 In addition to the above cases, warnings are also generated for
5027 GNAT features that have been provided in past versions but which
5028 have been superseded (typically by features in the new Ada standard).
5029 For example, @code{pragma Ravenscar} will be flagged since its
5030 function is replaced by @code{pragma Profile(Ravenscar)}.
5032 Note that this warning option functions differently from the
5033 restriction @code{No_Obsolescent_Features} in two respects.
5034 First, the restriction applies only to annex J features.
5035 Second, the restriction does flag uses of package @code{ASCII}.
5038 @emph{Suppress warnings on obsolescent features (Annex J).}
5039 @cindex @option{-gnatwJ} (@command{gcc})
5040 This switch disables warnings on use of obsolescent features.
5043 @emph{Activate warnings on variables that could be constants.}
5044 @cindex @option{-gnatwk} (@command{gcc})
5045 This switch activates warnings for variables that are initialized but
5046 never modified, and then could be declared constants. The default is that
5047 such warnings are not given.
5048 This warning can also be turned on using @option{-gnatwa}.
5051 @emph{Suppress warnings on variables that could be constants.}
5052 @cindex @option{-gnatwK} (@command{gcc})
5053 This switch disables warnings on variables that could be declared constants.
5056 @emph{Activate warnings for elaboration pragmas.}
5057 @cindex @option{-gnatwl} (@command{gcc})
5058 @cindex Elaboration, warnings
5059 This switch activates warnings on missing
5060 @code{Elaborate_All} and @code{Elaborate} pragmas.
5061 See the section in this guide on elaboration checking for details on
5062 when such pragmas should be used. In dynamic elaboration mode, this switch
5063 generations warnings about the need to add elaboration pragmas. Note however,
5064 that if you blindly follow these warnings, and add @code{Elaborate_All}
5065 warnings wherever they are recommended, you basically end up with the
5066 equivalent of the static elaboration model, which may not be what you want for
5067 legacy code for which the static model does not work.
5069 For the static model, the messages generated are labeled "info:" (for
5070 information messages). They are not warnings to add elaboration pragmas,
5071 merely informational messages showing what implicit elaboration pragmas
5072 have been added, for use in analyzing elaboration circularity problems.
5074 Warnings are also generated if you
5075 are using the static mode of elaboration, and a @code{pragma Elaborate}
5076 is encountered. The default is that such warnings
5078 This warning is not automatically turned on by the use of @option{-gnatwa}.
5081 @emph{Suppress warnings for elaboration pragmas.}
5082 @cindex @option{-gnatwL} (@command{gcc})
5083 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5084 See the section in this guide on elaboration checking for details on
5085 when such pragmas should be used.
5088 @emph{Activate warnings on modified but unreferenced variables.}
5089 @cindex @option{-gnatwm} (@command{gcc})
5090 This switch activates warnings for variables that are assigned (using
5091 an initialization value or with one or more assignment statements) but
5092 whose value is never read. The warning is suppressed for volatile
5093 variables and also for variables that are renamings of other variables
5094 or for which an address clause is given.
5095 This warning can also be turned on using @option{-gnatwa}.
5096 The default is that these warnings are not given.
5099 @emph{Disable warnings on modified but unreferenced variables.}
5100 @cindex @option{-gnatwM} (@command{gcc})
5101 This switch disables warnings for variables that are assigned or
5102 initialized, but never read.
5105 @emph{Set normal warnings mode.}
5106 @cindex @option{-gnatwn} (@command{gcc})
5107 This switch sets normal warning mode, in which enabled warnings are
5108 issued and treated as warnings rather than errors. This is the default
5109 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5110 an explicit @option{-gnatws} or
5111 @option{-gnatwe}. It also cancels the effect of the
5112 implicit @option{-gnatwe} that is activated by the
5113 use of @option{-gnatg}.
5116 @emph{Activate warnings on address clause overlays.}
5117 @cindex @option{-gnatwo} (@command{gcc})
5118 @cindex Address Clauses, warnings
5119 This switch activates warnings for possibly unintended initialization
5120 effects of defining address clauses that cause one variable to overlap
5121 another. The default is that such warnings are generated.
5122 This warning can also be turned on using @option{-gnatwa}.
5125 @emph{Suppress warnings on address clause overlays.}
5126 @cindex @option{-gnatwO} (@command{gcc})
5127 This switch suppresses warnings on possibly unintended initialization
5128 effects of defining address clauses that cause one variable to overlap
5132 @emph{Activate warnings on modified but unreferenced out parameters.}
5133 @cindex @option{-gnatw.o} (@command{gcc})
5134 This switch activates warnings for variables that are modified by using
5135 them as actuals for a call to a procedure with an out mode formal, where
5136 the resulting assigned value is never read. It is applicable in the case
5137 where there is more than one out mode formal. If there is only one out
5138 mode formal, the warning is issued by default (controlled by -gnatwu).
5139 The warning is suppressed for volatile
5140 variables and also for variables that are renamings of other variables
5141 or for which an address clause is given.
5142 The default is that these warnings are not given. Note that this warning
5143 is not included in -gnatwa, it must be activated explicitly.
5146 @emph{Disable warnings on modified but unreferenced out parameters.}
5147 @cindex @option{-gnatw.O} (@command{gcc})
5148 This switch suppresses warnings for variables that are modified by using
5149 them as actuals for a call to a procedure with an out mode formal, where
5150 the resulting assigned value is never read.
5153 @emph{Activate warnings on ineffective pragma Inlines.}
5154 @cindex @option{-gnatwp} (@command{gcc})
5155 @cindex Inlining, warnings
5156 This switch activates warnings for failure of front end inlining
5157 (activated by @option{-gnatN}) to inline a particular call. There are
5158 many reasons for not being able to inline a call, including most
5159 commonly that the call is too complex to inline. The default is
5160 that such warnings are not given.
5161 This warning can also be turned on using @option{-gnatwa}.
5162 Warnings on ineffective inlining by the gcc back-end can be activated
5163 separately, using the gcc switch -Winline.
5166 @emph{Suppress warnings on ineffective pragma Inlines.}
5167 @cindex @option{-gnatwP} (@command{gcc})
5168 This switch suppresses warnings on ineffective pragma Inlines. If the
5169 inlining mechanism cannot inline a call, it will simply ignore the
5173 @emph{Activate warnings on parameter ordering.}
5174 @cindex @option{-gnatw.p} (@command{gcc})
5175 @cindex Parameter order, warnings
5176 This switch activates warnings for cases of suspicious parameter
5177 ordering when the list of arguments are all simple identifiers that
5178 match the names of the formals, but are in a different order. The
5179 warning is suppressed if any use of named parameter notation is used,
5180 so this is the appropriate way to suppress a false positive (and
5181 serves to emphasize that the "misordering" is deliberate). The
5183 that such warnings are not given.
5184 This warning can also be turned on using @option{-gnatwa}.
5187 @emph{Suppress warnings on parameter ordering.}
5188 @cindex @option{-gnatw.P} (@command{gcc})
5189 This switch suppresses warnings on cases of suspicious parameter
5193 @emph{Activate warnings on questionable missing parentheses.}
5194 @cindex @option{-gnatwq} (@command{gcc})
5195 @cindex Parentheses, warnings
5196 This switch activates warnings for cases where parentheses are not used and
5197 the result is potential ambiguity from a readers point of view. For example
5198 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5199 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5200 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5201 follow the rule of always parenthesizing to make the association clear, and
5202 this warning switch warns if such parentheses are not present. The default
5203 is that these warnings are given.
5204 This warning can also be turned on using @option{-gnatwa}.
5207 @emph{Suppress warnings on questionable missing parentheses.}
5208 @cindex @option{-gnatwQ} (@command{gcc})
5209 This switch suppresses warnings for cases where the association is not
5210 clear and the use of parentheses is preferred.
5213 @emph{Activate warnings on redundant constructs.}
5214 @cindex @option{-gnatwr} (@command{gcc})
5215 This switch activates warnings for redundant constructs. The following
5216 is the current list of constructs regarded as redundant:
5220 Assignment of an item to itself.
5222 Type conversion that converts an expression to its own type.
5224 Use of the attribute @code{Base} where @code{typ'Base} is the same
5227 Use of pragma @code{Pack} when all components are placed by a record
5228 representation clause.
5230 Exception handler containing only a reraise statement (raise with no
5231 operand) which has no effect.
5233 Use of the operator abs on an operand that is known at compile time
5236 Comparison of boolean expressions to an explicit True value.
5239 This warning can also be turned on using @option{-gnatwa}.
5240 The default is that warnings for redundant constructs are not given.
5243 @emph{Suppress warnings on redundant constructs.}
5244 @cindex @option{-gnatwR} (@command{gcc})
5245 This switch suppresses warnings for redundant constructs.
5248 @emph{Suppress all warnings.}
5249 @cindex @option{-gnatws} (@command{gcc})
5250 This switch completely suppresses the
5251 output of all warning messages from the GNAT front end.
5252 Note that it does not suppress warnings from the @command{gcc} back end.
5253 To suppress these back end warnings as well, use the switch @option{-w}
5254 in addition to @option{-gnatws}.
5257 @emph{Activate warnings for tracking of deleted conditional code.}
5258 @cindex @option{-gnatwt} (@command{gcc})
5259 @cindex Deactivated code, warnings
5260 @cindex Deleted code, warnings
5261 This switch activates warnings for tracking of code in conditionals (IF and
5262 CASE statements) that is detected to be dead code which cannot be executed, and
5263 which is removed by the front end. This warning is off by default, and is not
5264 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5265 useful for detecting deactivated code in certified applications.
5268 @emph{Suppress warnings for tracking of deleted conditional code.}
5269 @cindex @option{-gnatwT} (@command{gcc})
5270 This switch suppresses warnings for tracking of deleted conditional code.
5273 @emph{Activate warnings on unused entities.}
5274 @cindex @option{-gnatwu} (@command{gcc})
5275 This switch activates warnings to be generated for entities that
5276 are declared but not referenced, and for units that are @code{with}'ed
5278 referenced. In the case of packages, a warning is also generated if
5279 no entities in the package are referenced. This means that if the package
5280 is referenced but the only references are in @code{use}
5281 clauses or @code{renames}
5282 declarations, a warning is still generated. A warning is also generated
5283 for a generic package that is @code{with}'ed but never instantiated.
5284 In the case where a package or subprogram body is compiled, and there
5285 is a @code{with} on the corresponding spec
5286 that is only referenced in the body,
5287 a warning is also generated, noting that the
5288 @code{with} can be moved to the body. The default is that
5289 such warnings are not generated.
5290 This switch also activates warnings on unreferenced formals
5291 (it includes the effect of @option{-gnatwf}).
5292 This warning can also be turned on using @option{-gnatwa}.
5295 @emph{Suppress warnings on unused entities.}
5296 @cindex @option{-gnatwU} (@command{gcc})
5297 This switch suppresses warnings for unused entities and packages.
5298 It also turns off warnings on unreferenced formals (and thus includes
5299 the effect of @option{-gnatwF}).
5302 @emph{Activate warnings on unassigned variables.}
5303 @cindex @option{-gnatwv} (@command{gcc})
5304 @cindex Unassigned variable warnings
5305 This switch activates warnings for access to variables which
5306 may not be properly initialized. The default is that
5307 such warnings are generated.
5308 This warning can also be turned on using @option{-gnatwa}.
5311 @emph{Suppress warnings on unassigned variables.}
5312 @cindex @option{-gnatwV} (@command{gcc})
5313 This switch suppresses warnings for access to variables which
5314 may not be properly initialized.
5315 For variables of a composite type, the warning can also be suppressed in
5316 Ada 2005 by using a default initialization with a box. For example, if
5317 Table is an array of records whose components are only partially uninitialized,
5318 then the following code:
5320 @smallexample @c ada
5321 Tab : Table := (others => <>);
5324 will suppress warnings on subsequent statements that access components
5328 @emph{Activate warnings on wrong low bound assumption.}
5329 @cindex @option{-gnatww} (@command{gcc})
5330 @cindex String indexing warnings
5331 This switch activates warnings for indexing an unconstrained string parameter
5332 with a literal or S'Length. This is a case where the code is assuming that the
5333 low bound is one, which is in general not true (for example when a slice is
5334 passed). The default is that such warnings are generated.
5335 This warning can also be turned on using @option{-gnatwa}.
5338 @emph{Suppress warnings on wrong low bound assumption.}
5339 @cindex @option{-gnatwW} (@command{gcc})
5340 This switch suppresses warnings for indexing an unconstrained string parameter
5341 with a literal or S'Length. Note that this warning can also be suppressed
5342 in a particular case by adding an
5343 assertion that the lower bound is 1,
5344 as shown in the following example.
5346 @smallexample @c ada
5347 procedure K (S : String) is
5348 pragma Assert (S'First = 1);
5353 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5354 @cindex @option{-gnatw.w} (@command{gcc})
5355 @cindex Warnings Off control
5356 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5357 where either the pragma is entirely useless (because it suppresses no
5358 warnings), or it could be replaced by @code{pragma Unreferenced} or
5359 @code{pragma Unmodified}.The default is that these warnings are not given.
5360 Note that this warning is not included in -gnatwa, it must be
5361 activated explicitly.
5364 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5365 @cindex @option{-gnatw.W} (@command{gcc})
5366 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5369 @emph{Activate warnings on Export/Import pragmas.}
5370 @cindex @option{-gnatwx} (@command{gcc})
5371 @cindex Export/Import pragma warnings
5372 This switch activates warnings on Export/Import pragmas when
5373 the compiler detects a possible conflict between the Ada and
5374 foreign language calling sequences. For example, the use of
5375 default parameters in a convention C procedure is dubious
5376 because the C compiler cannot supply the proper default, so
5377 a warning is issued. The default is that such warnings are
5379 This warning can also be turned on using @option{-gnatwa}.
5382 @emph{Suppress warnings on Export/Import pragmas.}
5383 @cindex @option{-gnatwX} (@command{gcc})
5384 This switch suppresses warnings on Export/Import pragmas.
5385 The sense of this is that you are telling the compiler that
5386 you know what you are doing in writing the pragma, and it
5387 should not complain at you.
5390 @emph{Activate warnings for No_Exception_Propagation mode.}
5391 @cindex @option{-gnatwm} (@command{gcc})
5392 This switch activates warnings for exception usage when pragma Restrictions
5393 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5394 explicit exception raises which are not covered by a local handler, and for
5395 exception handlers which do not cover a local raise. The default is that these
5396 warnings are not given.
5399 @emph{Disable warnings for No_Exception_Propagation mode.}
5400 This switch disables warnings for exception usage when pragma Restrictions
5401 (No_Exception_Propagation) is in effect.
5404 @emph{Activate warnings for Ada 2005 compatibility issues.}
5405 @cindex @option{-gnatwy} (@command{gcc})
5406 @cindex Ada 2005 compatibility issues warnings
5407 For the most part Ada 2005 is upwards compatible with Ada 95,
5408 but there are some exceptions (for example the fact that
5409 @code{interface} is now a reserved word in Ada 2005). This
5410 switch activates several warnings to help in identifying
5411 and correcting such incompatibilities. The default is that
5412 these warnings are generated. Note that at one point Ada 2005
5413 was called Ada 0Y, hence the choice of character.
5414 This warning can also be turned on using @option{-gnatwa}.
5417 @emph{Disable warnings for Ada 2005 compatibility issues.}
5418 @cindex @option{-gnatwY} (@command{gcc})
5419 @cindex Ada 2005 compatibility issues warnings
5420 This switch suppresses several warnings intended to help in identifying
5421 incompatibilities between Ada 95 and Ada 2005.
5424 @emph{Activate warnings on unchecked conversions.}
5425 @cindex @option{-gnatwz} (@command{gcc})
5426 @cindex Unchecked_Conversion warnings
5427 This switch activates warnings for unchecked conversions
5428 where the types are known at compile time to have different
5430 is that such warnings are generated. Warnings are also
5431 generated for subprogram pointers with different conventions,
5432 and, on VMS only, for data pointers with different conventions.
5433 This warning can also be turned on using @option{-gnatwa}.
5436 @emph{Suppress warnings on unchecked conversions.}
5437 @cindex @option{-gnatwZ} (@command{gcc})
5438 This switch suppresses warnings for unchecked conversions
5439 where the types are known at compile time to have different
5440 sizes or conventions.
5442 @item ^-Wunused^WARNINGS=UNUSED^
5443 @cindex @option{-Wunused}
5444 The warnings controlled by the @option{-gnatw} switch are generated by
5445 the front end of the compiler. The @option{GCC} back end can provide
5446 additional warnings and they are controlled by the @option{-W} switch.
5447 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5448 warnings for entities that are declared but not referenced.
5450 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5451 @cindex @option{-Wuninitialized}
5452 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5453 the back end warning for uninitialized variables. This switch must be
5454 used in conjunction with an optimization level greater than zero.
5456 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5457 @cindex @option{-Wall}
5458 This switch enables all the above warnings from the @option{GCC} back end.
5459 The code generator detects a number of warning situations that are missed
5460 by the @option{GNAT} front end, and this switch can be used to activate them.
5461 The use of this switch also sets the default front end warning mode to
5462 @option{-gnatwa}, that is, most front end warnings activated as well.
5464 @item ^-w^/NO_BACK_END_WARNINGS^
5466 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5467 The use of this switch also sets the default front end warning mode to
5468 @option{-gnatws}, that is, front end warnings suppressed as well.
5474 A string of warning parameters can be used in the same parameter. For example:
5481 will turn on all optional warnings except for elaboration pragma warnings,
5482 and also specify that warnings should be treated as errors.
5484 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5509 @node Debugging and Assertion Control
5510 @subsection Debugging and Assertion Control
5514 @cindex @option{-gnata} (@command{gcc})
5520 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5521 are ignored. This switch, where @samp{a} stands for assert, causes
5522 @code{Assert} and @code{Debug} pragmas to be activated.
5524 The pragmas have the form:
5528 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5529 @var{static-string-expression}@r{]})
5530 @b{pragma} Debug (@var{procedure call})
5535 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5536 If the result is @code{True}, the pragma has no effect (other than
5537 possible side effects from evaluating the expression). If the result is
5538 @code{False}, the exception @code{Assert_Failure} declared in the package
5539 @code{System.Assertions} is
5540 raised (passing @var{static-string-expression}, if present, as the
5541 message associated with the exception). If no string expression is
5542 given the default is a string giving the file name and line number
5545 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5546 @code{pragma Debug} may appear within a declaration sequence, allowing
5547 debugging procedures to be called between declarations.
5550 @item /DEBUG@r{[}=debug-level@r{]}
5552 Specifies how much debugging information is to be included in
5553 the resulting object file where 'debug-level' is one of the following:
5556 Include both debugger symbol records and traceback
5558 This is the default setting.
5560 Include both debugger symbol records and traceback in
5563 Excludes both debugger symbol records and traceback
5564 the object file. Same as /NODEBUG.
5566 Includes only debugger symbol records in the object
5567 file. Note that this doesn't include traceback information.
5572 @node Validity Checking
5573 @subsection Validity Checking
5574 @findex Validity Checking
5577 The Ada Reference Manual has specific requirements for checking
5578 for invalid values. In particular, RM 13.9.1 requires that the
5579 evaluation of invalid values (for example from unchecked conversions),
5580 not result in erroneous execution. In GNAT, the result of such an
5581 evaluation in normal default mode is to either use the value
5582 unmodified, or to raise Constraint_Error in those cases where use
5583 of the unmodified value would cause erroneous execution. The cases
5584 where unmodified values might lead to erroneous execution are case
5585 statements (where a wild jump might result from an invalid value),
5586 and subscripts on the left hand side (where memory corruption could
5587 occur as a result of an invalid value).
5589 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5592 The @code{x} argument is a string of letters that
5593 indicate validity checks that are performed or not performed in addition
5594 to the default checks described above.
5597 The options allowed for this qualifier
5598 indicate validity checks that are performed or not performed in addition
5599 to the default checks described above.
5605 @emph{All validity checks.}
5606 @cindex @option{-gnatVa} (@command{gcc})
5607 All validity checks are turned on.
5609 That is, @option{-gnatVa} is
5610 equivalent to @option{gnatVcdfimorst}.
5614 @emph{Validity checks for copies.}
5615 @cindex @option{-gnatVc} (@command{gcc})
5616 The right hand side of assignments, and the initializing values of
5617 object declarations are validity checked.
5620 @emph{Default (RM) validity checks.}
5621 @cindex @option{-gnatVd} (@command{gcc})
5622 Some validity checks are done by default following normal Ada semantics
5624 A check is done in case statements that the expression is within the range
5625 of the subtype. If it is not, Constraint_Error is raised.
5626 For assignments to array components, a check is done that the expression used
5627 as index is within the range. If it is not, Constraint_Error is raised.
5628 Both these validity checks may be turned off using switch @option{-gnatVD}.
5629 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5630 switch @option{-gnatVd} will leave the checks turned on.
5631 Switch @option{-gnatVD} should be used only if you are sure that all such
5632 expressions have valid values. If you use this switch and invalid values
5633 are present, then the program is erroneous, and wild jumps or memory
5634 overwriting may occur.
5637 @emph{Validity checks for elementary components.}
5638 @cindex @option{-gnatVe} (@command{gcc})
5639 In the absence of this switch, assignments to record or array components are
5640 not validity checked, even if validity checks for assignments generally
5641 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5642 require valid data, but assignment of individual components does. So for
5643 example, there is a difference between copying the elements of an array with a
5644 slice assignment, compared to assigning element by element in a loop. This
5645 switch allows you to turn off validity checking for components, even when they
5646 are assigned component by component.
5649 @emph{Validity checks for floating-point values.}
5650 @cindex @option{-gnatVf} (@command{gcc})
5651 In the absence of this switch, validity checking occurs only for discrete
5652 values. If @option{-gnatVf} is specified, then validity checking also applies
5653 for floating-point values, and NaNs and infinities are considered invalid,
5654 as well as out of range values for constrained types. Note that this means
5655 that standard IEEE infinity mode is not allowed. The exact contexts
5656 in which floating-point values are checked depends on the setting of other
5657 options. For example,
5658 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5659 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5660 (the order does not matter) specifies that floating-point parameters of mode
5661 @code{in} should be validity checked.
5664 @emph{Validity checks for @code{in} mode parameters}
5665 @cindex @option{-gnatVi} (@command{gcc})
5666 Arguments for parameters of mode @code{in} are validity checked in function
5667 and procedure calls at the point of call.
5670 @emph{Validity checks for @code{in out} mode parameters.}
5671 @cindex @option{-gnatVm} (@command{gcc})
5672 Arguments for parameters of mode @code{in out} are validity checked in
5673 procedure calls at the point of call. The @code{'m'} here stands for
5674 modify, since this concerns parameters that can be modified by the call.
5675 Note that there is no specific option to test @code{out} parameters,
5676 but any reference within the subprogram will be tested in the usual
5677 manner, and if an invalid value is copied back, any reference to it
5678 will be subject to validity checking.
5681 @emph{No validity checks.}
5682 @cindex @option{-gnatVn} (@command{gcc})
5683 This switch turns off all validity checking, including the default checking
5684 for case statements and left hand side subscripts. Note that the use of
5685 the switch @option{-gnatp} suppresses all run-time checks, including
5686 validity checks, and thus implies @option{-gnatVn}. When this switch
5687 is used, it cancels any other @option{-gnatV} previously issued.
5690 @emph{Validity checks for operator and attribute operands.}
5691 @cindex @option{-gnatVo} (@command{gcc})
5692 Arguments for predefined operators and attributes are validity checked.
5693 This includes all operators in package @code{Standard},
5694 the shift operators defined as intrinsic in package @code{Interfaces}
5695 and operands for attributes such as @code{Pos}. Checks are also made
5696 on individual component values for composite comparisons, and on the
5697 expressions in type conversions and qualified expressions. Checks are
5698 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
5701 @emph{Validity checks for parameters.}
5702 @cindex @option{-gnatVp} (@command{gcc})
5703 This controls the treatment of parameters within a subprogram (as opposed
5704 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5705 of parameters on a call. If either of these call options is used, then
5706 normally an assumption is made within a subprogram that the input arguments
5707 have been validity checking at the point of call, and do not need checking
5708 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5709 is not made, and parameters are not assumed to be valid, so their validity
5710 will be checked (or rechecked) within the subprogram.
5713 @emph{Validity checks for function returns.}
5714 @cindex @option{-gnatVr} (@command{gcc})
5715 The expression in @code{return} statements in functions is validity
5719 @emph{Validity checks for subscripts.}
5720 @cindex @option{-gnatVs} (@command{gcc})
5721 All subscripts expressions are checked for validity, whether they appear
5722 on the right side or left side (in default mode only left side subscripts
5723 are validity checked).
5726 @emph{Validity checks for tests.}
5727 @cindex @option{-gnatVt} (@command{gcc})
5728 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5729 statements are checked, as well as guard expressions in entry calls.
5734 The @option{-gnatV} switch may be followed by
5735 ^a string of letters^a list of options^
5736 to turn on a series of validity checking options.
5738 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5739 specifies that in addition to the default validity checking, copies and
5740 function return expressions are to be validity checked.
5741 In order to make it easier
5742 to specify the desired combination of effects,
5744 the upper case letters @code{CDFIMORST} may
5745 be used to turn off the corresponding lower case option.
5748 the prefix @code{NO} on an option turns off the corresponding validity
5751 @item @code{NOCOPIES}
5752 @item @code{NODEFAULT}
5753 @item @code{NOFLOATS}
5754 @item @code{NOIN_PARAMS}
5755 @item @code{NOMOD_PARAMS}
5756 @item @code{NOOPERANDS}
5757 @item @code{NORETURNS}
5758 @item @code{NOSUBSCRIPTS}
5759 @item @code{NOTESTS}
5763 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5764 turns on all validity checking options except for
5765 checking of @code{@b{in out}} procedure arguments.
5767 The specification of additional validity checking generates extra code (and
5768 in the case of @option{-gnatVa} the code expansion can be substantial).
5769 However, these additional checks can be very useful in detecting
5770 uninitialized variables, incorrect use of unchecked conversion, and other
5771 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5772 is useful in conjunction with the extra validity checking, since this
5773 ensures that wherever possible uninitialized variables have invalid values.
5775 See also the pragma @code{Validity_Checks} which allows modification of
5776 the validity checking mode at the program source level, and also allows for
5777 temporary disabling of validity checks.
5779 @node Style Checking
5780 @subsection Style Checking
5781 @findex Style checking
5784 The @option{-gnaty^x^(option,option,@dots{})^} switch
5785 @cindex @option{-gnaty} (@command{gcc})
5786 causes the compiler to
5787 enforce specified style rules. A limited set of style rules has been used
5788 in writing the GNAT sources themselves. This switch allows user programs
5789 to activate all or some of these checks. If the source program fails a
5790 specified style check, an appropriate warning message is given, preceded by
5791 the character sequence ``(style)''.
5793 @code{(option,option,@dots{})} is a sequence of keywords
5796 The string @var{x} is a sequence of letters or digits
5798 indicating the particular style
5799 checks to be performed. The following checks are defined:
5804 @emph{Specify indentation level.}
5805 If a digit from 1-9 appears
5806 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5807 then proper indentation is checked, with the digit indicating the
5808 indentation level required. A value of zero turns off this style check.
5809 The general style of required indentation is as specified by
5810 the examples in the Ada Reference Manual. Full line comments must be
5811 aligned with the @code{--} starting on a column that is a multiple of
5812 the alignment level, or they may be aligned the same way as the following
5813 non-blank line (this is useful when full line comments appear in the middle
5817 @emph{Check attribute casing.}
5818 Attribute names, including the case of keywords such as @code{digits}
5819 used as attributes names, must be written in mixed case, that is, the
5820 initial letter and any letter following an underscore must be uppercase.
5821 All other letters must be lowercase.
5823 @item ^A^ARRAY_INDEXES^
5824 @emph{Use of array index numbers in array attributes.}
5825 When using the array attributes First, Last, Range,
5826 or Length, the index number must be omitted for one-dimensional arrays
5827 and is required for multi-dimensional arrays.
5830 @emph{Blanks not allowed at statement end.}
5831 Trailing blanks are not allowed at the end of statements. The purpose of this
5832 rule, together with h (no horizontal tabs), is to enforce a canonical format
5833 for the use of blanks to separate source tokens.
5836 @emph{Check comments.}
5837 Comments must meet the following set of rules:
5842 The ``@code{--}'' that starts the column must either start in column one,
5843 or else at least one blank must precede this sequence.
5846 Comments that follow other tokens on a line must have at least one blank
5847 following the ``@code{--}'' at the start of the comment.
5850 Full line comments must have two blanks following the ``@code{--}'' that
5851 starts the comment, with the following exceptions.
5854 A line consisting only of the ``@code{--}'' characters, possibly preceded
5855 by blanks is permitted.
5858 A comment starting with ``@code{--x}'' where @code{x} is a special character
5860 This allows proper processing of the output generated by specialized tools
5861 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5863 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5864 special character is defined as being in one of the ASCII ranges
5865 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
5866 Note that this usage is not permitted
5867 in GNAT implementation units (i.e., when @option{-gnatg} is used).
5870 A line consisting entirely of minus signs, possibly preceded by blanks, is
5871 permitted. This allows the construction of box comments where lines of minus
5872 signs are used to form the top and bottom of the box.
5875 A comment that starts and ends with ``@code{--}'' is permitted as long as at
5876 least one blank follows the initial ``@code{--}''. Together with the preceding
5877 rule, this allows the construction of box comments, as shown in the following
5880 ---------------------------
5881 -- This is a box comment --
5882 -- with two text lines. --
5883 ---------------------------
5887 @item ^d^DOS_LINE_ENDINGS^
5888 @emph{Check no DOS line terminators present.}
5889 All lines must be terminated by a single ASCII.LF
5890 character (in particular the DOS line terminator sequence CR/LF is not
5894 @emph{Check end/exit labels.}
5895 Optional labels on @code{end} statements ending subprograms and on
5896 @code{exit} statements exiting named loops, are required to be present.
5899 @emph{No form feeds or vertical tabs.}
5900 Neither form feeds nor vertical tab characters are permitted
5904 @emph{GNAT style mode}
5905 The set of style check switches is set to match that used by the GNAT sources.
5906 This may be useful when developing code that is eventually intended to be
5907 incorporated into GNAT. For further details, see GNAT sources.
5910 @emph{No horizontal tabs.}
5911 Horizontal tab characters are not permitted in the source text.
5912 Together with the b (no blanks at end of line) check, this
5913 enforces a canonical form for the use of blanks to separate
5917 @emph{Check if-then layout.}
5918 The keyword @code{then} must appear either on the same
5919 line as corresponding @code{if}, or on a line on its own, lined
5920 up under the @code{if} with at least one non-blank line in between
5921 containing all or part of the condition to be tested.
5924 @emph{check mode IN keywords}
5925 Mode @code{in} (the default mode) is not
5926 allowed to be given explicitly. @code{in out} is fine,
5927 but not @code{in} on its own.
5930 @emph{Check keyword casing.}
5931 All keywords must be in lower case (with the exception of keywords
5932 such as @code{digits} used as attribute names to which this check
5936 @emph{Check layout.}
5937 Layout of statement and declaration constructs must follow the
5938 recommendations in the Ada Reference Manual, as indicated by the
5939 form of the syntax rules. For example an @code{else} keyword must
5940 be lined up with the corresponding @code{if} keyword.
5942 There are two respects in which the style rule enforced by this check
5943 option are more liberal than those in the Ada Reference Manual. First
5944 in the case of record declarations, it is permissible to put the
5945 @code{record} keyword on the same line as the @code{type} keyword, and
5946 then the @code{end} in @code{end record} must line up under @code{type}.
5947 This is also permitted when the type declaration is split on two lines.
5948 For example, any of the following three layouts is acceptable:
5950 @smallexample @c ada
5973 Second, in the case of a block statement, a permitted alternative
5974 is to put the block label on the same line as the @code{declare} or
5975 @code{begin} keyword, and then line the @code{end} keyword up under
5976 the block label. For example both the following are permitted:
5978 @smallexample @c ada
5996 The same alternative format is allowed for loops. For example, both of
5997 the following are permitted:
5999 @smallexample @c ada
6001 Clear : while J < 10 loop
6012 @item ^Lnnn^MAX_NESTING=nnn^
6013 @emph{Set maximum nesting level}
6014 The maximum level of nesting of constructs (including subprograms, loops,
6015 blocks, packages, and conditionals) may not exceed the given value
6016 @option{nnn}. A value of zero disconnects this style check.
6018 @item ^m^LINE_LENGTH^
6019 @emph{Check maximum line length.}
6020 The length of source lines must not exceed 79 characters, including
6021 any trailing blanks. The value of 79 allows convenient display on an
6022 80 character wide device or window, allowing for possible special
6023 treatment of 80 character lines. Note that this count is of
6024 characters in the source text. This means that a tab character counts
6025 as one character in this count but a wide character sequence counts as
6026 a single character (however many bytes are needed in the encoding).
6028 @item ^Mnnn^MAX_LENGTH=nnn^
6029 @emph{Set maximum line length.}
6030 The length of lines must not exceed the
6031 given value @option{nnn}. The maximum value that can be specified is 32767.
6033 @item ^n^STANDARD_CASING^
6034 @emph{Check casing of entities in Standard.}
6035 Any identifier from Standard must be cased
6036 to match the presentation in the Ada Reference Manual (for example,
6037 @code{Integer} and @code{ASCII.NUL}).
6040 @emph{Turn off all style checks}
6041 All style check options are turned off.
6043 @item ^o^ORDERED_SUBPROGRAMS^
6044 @emph{Check order of subprogram bodies.}
6045 All subprogram bodies in a given scope
6046 (e.g.@: a package body) must be in alphabetical order. The ordering
6047 rule uses normal Ada rules for comparing strings, ignoring casing
6048 of letters, except that if there is a trailing numeric suffix, then
6049 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6053 @emph{Check pragma casing.}
6054 Pragma names must be written in mixed case, that is, the
6055 initial letter and any letter following an underscore must be uppercase.
6056 All other letters must be lowercase.
6058 @item ^r^REFERENCES^
6059 @emph{Check references.}
6060 All identifier references must be cased in the same way as the
6061 corresponding declaration. No specific casing style is imposed on
6062 identifiers. The only requirement is for consistency of references
6065 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6066 @emph{Check no statements after THEN/ELSE.}
6067 No statements are allowed
6068 on the same line as a THEN or ELSE keyword following the
6069 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6070 and a special exception allows a pragma to appear after ELSE.
6073 @emph{Check separate specs.}
6074 Separate declarations (``specs'') are required for subprograms (a
6075 body is not allowed to serve as its own declaration). The only
6076 exception is that parameterless library level procedures are
6077 not required to have a separate declaration. This exception covers
6078 the most frequent form of main program procedures.
6081 @emph{Check token spacing.}
6082 The following token spacing rules are enforced:
6087 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6090 The token @code{=>} must be surrounded by spaces.
6093 The token @code{<>} must be preceded by a space or a left parenthesis.
6096 Binary operators other than @code{**} must be surrounded by spaces.
6097 There is no restriction on the layout of the @code{**} binary operator.
6100 Colon must be surrounded by spaces.
6103 Colon-equal (assignment, initialization) must be surrounded by spaces.
6106 Comma must be the first non-blank character on the line, or be
6107 immediately preceded by a non-blank character, and must be followed
6111 If the token preceding a left parenthesis ends with a letter or digit, then
6112 a space must separate the two tokens.
6115 A right parenthesis must either be the first non-blank character on
6116 a line, or it must be preceded by a non-blank character.
6119 A semicolon must not be preceded by a space, and must not be followed by
6120 a non-blank character.
6123 A unary plus or minus may not be followed by a space.
6126 A vertical bar must be surrounded by spaces.
6129 @item ^u^UNNECESSARY_BLANK_LINES^
6130 @emph{Check unnecessary blank lines.}
6131 Unnecessary blank lines are not allowed. A blank line is considered
6132 unnecessary if it appears at the end of the file, or if more than
6133 one blank line occurs in sequence.
6135 @item ^x^XTRA_PARENS^
6136 @emph{Check extra parentheses.}
6137 Unnecessary extra level of parentheses (C-style) are not allowed
6138 around conditions in @code{if} statements, @code{while} statements and
6139 @code{exit} statements.
6141 @item ^y^ALL_BUILTIN^
6142 @emph{Set all standard style check options}
6143 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6144 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6145 @option{-gnatyS}, @option{-gnatyLnnn},
6146 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6150 @emph{Remove style check options}
6151 This causes any subsequent options in the string to act as canceling the
6152 corresponding style check option. To cancel maximum nesting level control,
6153 use @option{L} parameter witout any integer value after that, because any
6154 digit following @option{-} in the parameter string of the @option{-gnaty}
6155 option will be threated as canceling indentation check. The same is true
6156 for @option{M} parameter. @option{y} and @option{N} parameters are not
6157 allowed after @option{-}.
6160 This causes any subsequent options in the string to enable the corresponding
6161 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6167 @emph{Removing style check options}
6168 If the name of a style check is preceded by @option{NO} then the corresponding
6169 style check is turned off. For example @option{NOCOMMENTS} turns off style
6170 checking for comments.
6175 In the above rules, appearing in column one is always permitted, that is,
6176 counts as meeting either a requirement for a required preceding space,
6177 or as meeting a requirement for no preceding space.
6179 Appearing at the end of a line is also always permitted, that is, counts
6180 as meeting either a requirement for a following space, or as meeting
6181 a requirement for no following space.
6184 If any of these style rules is violated, a message is generated giving
6185 details on the violation. The initial characters of such messages are
6186 always ``@code{(style)}''. Note that these messages are treated as warning
6187 messages, so they normally do not prevent the generation of an object
6188 file. The @option{-gnatwe} switch can be used to treat warning messages,
6189 including style messages, as fatal errors.
6193 @option{-gnaty} on its own (that is not
6194 followed by any letters or digits), then the effect is equivalent
6195 to the use of @option{-gnatyy}, as described above, that is all
6196 built-in standard style check options are enabled.
6200 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6201 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6202 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6214 clears any previously set style checks.
6216 @node Run-Time Checks
6217 @subsection Run-Time Checks
6218 @cindex Division by zero
6219 @cindex Access before elaboration
6220 @cindex Checks, division by zero
6221 @cindex Checks, access before elaboration
6222 @cindex Checks, stack overflow checking
6225 If you compile with the default options, GNAT will insert many run-time
6226 checks into the compiled code, including code that performs range
6227 checking against constraints, but not arithmetic overflow checking for
6228 integer operations (including division by zero), checks for access
6229 before elaboration on subprogram calls, or stack overflow checking. All
6230 other run-time checks, as required by the Ada Reference Manual, are
6231 generated by default. The following @command{gcc} switches refine this
6237 @cindex @option{-gnatp} (@command{gcc})
6238 @cindex Suppressing checks
6239 @cindex Checks, suppressing
6241 Suppress all run-time checks as though @code{pragma Suppress (all_checks})
6242 had been present in the source. Validity checks are also suppressed (in
6243 other words @option{-gnatp} also implies @option{-gnatVn}.
6244 Use this switch to improve the performance
6245 of the code at the expense of safety in the presence of invalid data or
6249 @cindex @option{-gnato} (@command{gcc})
6250 @cindex Overflow checks
6251 @cindex Check, overflow
6252 Enables overflow checking for integer operations.
6253 This causes GNAT to generate slower and larger executable
6254 programs by adding code to check for overflow (resulting in raising
6255 @code{Constraint_Error} as required by standard Ada
6256 semantics). These overflow checks correspond to situations in which
6257 the true value of the result of an operation may be outside the base
6258 range of the result type. The following example shows the distinction:
6260 @smallexample @c ada
6261 X1 : Integer := "Integer'Last";
6262 X2 : Integer range 1 .. 5 := "5";
6263 X3 : Integer := "Integer'Last";
6264 X4 : Integer range 1 .. 5 := "5";
6265 F : Float := "2.0E+20";
6274 Note that if explicit values are assigned at compile time, the compiler may
6275 be able to detect overflow at compile time, in which case no run-time check
6276 is required, and the setting of -gnato is irrelevant. That's why the assigned
6277 values in the above fragment are in quotes, the meaning is "assign a value
6278 not known to the compiler that happens to be equal to ...". The remaining
6279 discussion assumes that the compiler cannot detect the values at compile time.
6281 Here the first addition results in a value that is outside the base range
6282 of Integer, and hence requires an overflow check for detection of the
6283 constraint error. Thus the first assignment to @code{X1} raises a
6284 @code{Constraint_Error} exception only if @option{-gnato} is set.
6286 The second increment operation results in a violation
6287 of the explicit range constraint, and such range checks are always
6288 performed (unless specifically suppressed with a pragma @code{suppress}
6289 or the use of @option{-gnatp}).
6291 The two conversions of @code{F} both result in values that are outside
6292 the base range of type @code{Integer} and thus will raise
6293 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6294 The fact that the result of the second conversion is assigned to
6295 variable @code{X4} with a restricted range is irrelevant, since the problem
6296 is in the conversion, not the assignment.
6298 Basically the rule is that in the default mode (@option{-gnato} not
6299 used), the generated code assures that all integer variables stay
6300 within their declared ranges, or within the base range if there is
6301 no declared range. This prevents any serious problems like indexes
6302 out of range for array operations.
6304 What is not checked in default mode is an overflow that results in
6305 an in-range, but incorrect value. In the above example, the assignments
6306 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6307 range of the target variable, but the result is wrong in the sense that
6308 it is too large to be represented correctly. Typically the assignment
6309 to @code{X1} will result in wrap around to the largest negative number.
6310 The conversions of @code{F} will result in some @code{Integer} value
6311 and if that integer value is out of the @code{X4} range then the
6312 subsequent assignment would generate an exception.
6314 @findex Machine_Overflows
6315 Note that the @option{-gnato} switch does not affect the code generated
6316 for any floating-point operations; it applies only to integer
6318 For floating-point, GNAT has the @code{Machine_Overflows}
6319 attribute set to @code{False} and the normal mode of operation is to
6320 generate IEEE NaN and infinite values on overflow or invalid operations
6321 (such as dividing 0.0 by 0.0).
6323 The reason that we distinguish overflow checking from other kinds of
6324 range constraint checking is that a failure of an overflow check, unlike
6325 for example the failure of a range check, can result in an incorrect
6326 value, but cannot cause random memory destruction (like an out of range
6327 subscript), or a wild jump (from an out of range case value). Overflow
6328 checking is also quite expensive in time and space, since in general it
6329 requires the use of double length arithmetic.
6331 Note again that @option{-gnato} is off by default, so overflow checking is
6332 not performed in default mode. This means that out of the box, with the
6333 default settings, GNAT does not do all the checks expected from the
6334 language description in the Ada Reference Manual. If you want all constraint
6335 checks to be performed, as described in this Manual, then you must
6336 explicitly use the -gnato switch either on the @command{gnatmake} or
6337 @command{gcc} command.
6340 @cindex @option{-gnatE} (@command{gcc})
6341 @cindex Elaboration checks
6342 @cindex Check, elaboration
6343 Enables dynamic checks for access-before-elaboration
6344 on subprogram calls and generic instantiations.
6345 For full details of the effect and use of this switch,
6346 @xref{Compiling Using gcc}.
6349 @cindex @option{-fstack-check} (@command{gcc})
6350 @cindex Stack Overflow Checking
6351 @cindex Checks, stack overflow checking
6352 Activates stack overflow checking. For full details of the effect and use of
6353 this switch see @ref{Stack Overflow Checking}.
6358 The setting of these switches only controls the default setting of the
6359 checks. You may modify them using either @code{Suppress} (to remove
6360 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6363 @node Using gcc for Syntax Checking
6364 @subsection Using @command{gcc} for Syntax Checking
6367 @cindex @option{-gnats} (@command{gcc})
6371 The @code{s} stands for ``syntax''.
6374 Run GNAT in syntax checking only mode. For
6375 example, the command
6378 $ gcc -c -gnats x.adb
6382 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6383 series of files in a single command
6385 , and can use wild cards to specify such a group of files.
6386 Note that you must specify the @option{-c} (compile
6387 only) flag in addition to the @option{-gnats} flag.
6390 You may use other switches in conjunction with @option{-gnats}. In
6391 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6392 format of any generated error messages.
6394 When the source file is empty or contains only empty lines and/or comments,
6395 the output is a warning:
6398 $ gcc -c -gnats -x ada toto.txt
6399 toto.txt:1:01: warning: empty file, contains no compilation units
6403 Otherwise, the output is simply the error messages, if any. No object file or
6404 ALI file is generated by a syntax-only compilation. Also, no units other
6405 than the one specified are accessed. For example, if a unit @code{X}
6406 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6407 check only mode does not access the source file containing unit
6410 @cindex Multiple units, syntax checking
6411 Normally, GNAT allows only a single unit in a source file. However, this
6412 restriction does not apply in syntax-check-only mode, and it is possible
6413 to check a file containing multiple compilation units concatenated
6414 together. This is primarily used by the @code{gnatchop} utility
6415 (@pxref{Renaming Files Using gnatchop}).
6418 @node Using gcc for Semantic Checking
6419 @subsection Using @command{gcc} for Semantic Checking
6422 @cindex @option{-gnatc} (@command{gcc})
6426 The @code{c} stands for ``check''.
6428 Causes the compiler to operate in semantic check mode,
6429 with full checking for all illegalities specified in the
6430 Ada Reference Manual, but without generation of any object code
6431 (no object file is generated).
6433 Because dependent files must be accessed, you must follow the GNAT
6434 semantic restrictions on file structuring to operate in this mode:
6438 The needed source files must be accessible
6439 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6442 Each file must contain only one compilation unit.
6445 The file name and unit name must match (@pxref{File Naming Rules}).
6448 The output consists of error messages as appropriate. No object file is
6449 generated. An @file{ALI} file is generated for use in the context of
6450 cross-reference tools, but this file is marked as not being suitable
6451 for binding (since no object file is generated).
6452 The checking corresponds exactly to the notion of
6453 legality in the Ada Reference Manual.
6455 Any unit can be compiled in semantics-checking-only mode, including
6456 units that would not normally be compiled (subunits,
6457 and specifications where a separate body is present).
6460 @node Compiling Different Versions of Ada
6461 @subsection Compiling Different Versions of Ada
6464 The switches described in this section allow you to explicitly specify
6465 the version of the Ada language that your programs are written in.
6466 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6467 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6468 indicate Ada 83 compatibility mode.
6471 @cindex Compatibility with Ada 83
6473 @item -gnat83 (Ada 83 Compatibility Mode)
6474 @cindex @option{-gnat83} (@command{gcc})
6475 @cindex ACVC, Ada 83 tests
6479 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6480 specifies that the program is to be compiled in Ada 83 mode. With
6481 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6482 semantics where this can be done easily.
6483 It is not possible to guarantee this switch does a perfect
6484 job; some subtle tests, such as are
6485 found in earlier ACVC tests (and that have been removed from the ACATS suite
6486 for Ada 95), might not compile correctly.
6487 Nevertheless, this switch may be useful in some circumstances, for example
6488 where, due to contractual reasons, existing code needs to be maintained
6489 using only Ada 83 features.
6491 With few exceptions (most notably the need to use @code{<>} on
6492 @cindex Generic formal parameters
6493 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6494 reserved words, and the use of packages
6495 with optional bodies), it is not necessary to specify the
6496 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6497 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6498 a correct Ada 83 program is usually also a correct program
6499 in these later versions of the language standard.
6500 For further information, please refer to @ref{Compatibility and Porting Guide}.
6502 @item -gnat95 (Ada 95 mode)
6503 @cindex @option{-gnat95} (@command{gcc})
6507 This switch directs the compiler to implement the Ada 95 version of the
6509 Since Ada 95 is almost completely upwards
6510 compatible with Ada 83, Ada 83 programs may generally be compiled using
6511 this switch (see the description of the @option{-gnat83} switch for further
6512 information about Ada 83 mode).
6513 If an Ada 2005 program is compiled in Ada 95 mode,
6514 uses of the new Ada 2005 features will cause error
6515 messages or warnings.
6517 This switch also can be used to cancel the effect of a previous
6518 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6520 @item -gnat05 (Ada 2005 mode)
6521 @cindex @option{-gnat05} (@command{gcc})
6522 @cindex Ada 2005 mode
6525 This switch directs the compiler to implement the Ada 2005 version of the
6527 Since Ada 2005 is almost completely upwards
6528 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6529 may generally be compiled using this switch (see the description of the
6530 @option{-gnat83} and @option{-gnat95} switches for further
6533 For information about the approved ``Ada Issues'' that have been incorporated
6534 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6535 Included with GNAT releases is a file @file{features-ada0y} that describes
6536 the set of implemented Ada 2005 features.
6540 @node Character Set Control
6541 @subsection Character Set Control
6543 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6544 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6547 Normally GNAT recognizes the Latin-1 character set in source program
6548 identifiers, as described in the Ada Reference Manual.
6550 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6551 single character ^^or word^ indicating the character set, as follows:
6555 ISO 8859-1 (Latin-1) identifiers
6558 ISO 8859-2 (Latin-2) letters allowed in identifiers
6561 ISO 8859-3 (Latin-3) letters allowed in identifiers
6564 ISO 8859-4 (Latin-4) letters allowed in identifiers
6567 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6570 ISO 8859-15 (Latin-9) letters allowed in identifiers
6573 IBM PC letters (code page 437) allowed in identifiers
6576 IBM PC letters (code page 850) allowed in identifiers
6578 @item ^f^FULL_UPPER^
6579 Full upper-half codes allowed in identifiers
6582 No upper-half codes allowed in identifiers
6585 Wide-character codes (that is, codes greater than 255)
6586 allowed in identifiers
6589 @xref{Foreign Language Representation}, for full details on the
6590 implementation of these character sets.
6592 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6593 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6594 Specify the method of encoding for wide characters.
6595 @var{e} is one of the following:
6600 Hex encoding (brackets coding also recognized)
6603 Upper half encoding (brackets encoding also recognized)
6606 Shift/JIS encoding (brackets encoding also recognized)
6609 EUC encoding (brackets encoding also recognized)
6612 UTF-8 encoding (brackets encoding also recognized)
6615 Brackets encoding only (default value)
6617 For full details on these encoding
6618 methods see @ref{Wide Character Encodings}.
6619 Note that brackets coding is always accepted, even if one of the other
6620 options is specified, so for example @option{-gnatW8} specifies that both
6621 brackets and UTF-8 encodings will be recognized. The units that are
6622 with'ed directly or indirectly will be scanned using the specified
6623 representation scheme, and so if one of the non-brackets scheme is
6624 used, it must be used consistently throughout the program. However,
6625 since brackets encoding is always recognized, it may be conveniently
6626 used in standard libraries, allowing these libraries to be used with
6627 any of the available coding schemes.
6630 If no @option{-gnatW?} parameter is present, then the default
6631 representation is normally Brackets encoding only. However, if the
6632 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6633 byte order mark or BOM for UTF-8), then these three characters are
6634 skipped and the default representation for the file is set to UTF-8.
6636 Note that the wide character representation that is specified (explicitly
6637 or by default) for the main program also acts as the default encoding used
6638 for Wide_Text_IO files if not specifically overridden by a WCEM form
6642 @node File Naming Control
6643 @subsection File Naming Control
6646 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6647 @cindex @option{-gnatk} (@command{gcc})
6648 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6649 1-999, indicates the maximum allowable length of a file name (not
6650 including the @file{.ads} or @file{.adb} extension). The default is not
6651 to enable file name krunching.
6653 For the source file naming rules, @xref{File Naming Rules}.
6656 @node Subprogram Inlining Control
6657 @subsection Subprogram Inlining Control
6662 @cindex @option{-gnatn} (@command{gcc})
6664 The @code{n} here is intended to suggest the first syllable of the
6667 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6668 inlining to actually occur, optimization must be enabled. To enable
6669 inlining of subprograms specified by pragma @code{Inline},
6670 you must also specify this switch.
6671 In the absence of this switch, GNAT does not attempt
6672 inlining and does not need to access the bodies of
6673 subprograms for which @code{pragma Inline} is specified if they are not
6674 in the current unit.
6676 If you specify this switch the compiler will access these bodies,
6677 creating an extra source dependency for the resulting object file, and
6678 where possible, the call will be inlined.
6679 For further details on when inlining is possible
6680 see @ref{Inlining of Subprograms}.
6683 @cindex @option{-gnatN} (@command{gcc})
6684 The front end inlining activated by this switch is generally more extensive,
6685 and quite often more effective than the standard @option{-gnatn} inlining mode.
6686 It will also generate additional dependencies.
6688 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
6689 to specify both options.
6692 @node Auxiliary Output Control
6693 @subsection Auxiliary Output Control
6697 @cindex @option{-gnatt} (@command{gcc})
6698 @cindex Writing internal trees
6699 @cindex Internal trees, writing to file
6700 Causes GNAT to write the internal tree for a unit to a file (with the
6701 extension @file{.adt}.
6702 This not normally required, but is used by separate analysis tools.
6704 these tools do the necessary compilations automatically, so you should
6705 not have to specify this switch in normal operation.
6708 @cindex @option{-gnatu} (@command{gcc})
6709 Print a list of units required by this compilation on @file{stdout}.
6710 The listing includes all units on which the unit being compiled depends
6711 either directly or indirectly.
6714 @item -pass-exit-codes
6715 @cindex @option{-pass-exit-codes} (@command{gcc})
6716 If this switch is not used, the exit code returned by @command{gcc} when
6717 compiling multiple files indicates whether all source files have
6718 been successfully used to generate object files or not.
6720 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
6721 exit status and allows an integrated development environment to better
6722 react to a compilation failure. Those exit status are:
6726 There was an error in at least one source file.
6728 At least one source file did not generate an object file.
6730 The compiler died unexpectedly (internal error for example).
6732 An object file has been generated for every source file.
6737 @node Debugging Control
6738 @subsection Debugging Control
6742 @cindex Debugging options
6745 @cindex @option{-gnatd} (@command{gcc})
6746 Activate internal debugging switches. @var{x} is a letter or digit, or
6747 string of letters or digits, which specifies the type of debugging
6748 outputs desired. Normally these are used only for internal development
6749 or system debugging purposes. You can find full documentation for these
6750 switches in the body of the @code{Debug} unit in the compiler source
6751 file @file{debug.adb}.
6755 @cindex @option{-gnatG} (@command{gcc})
6756 This switch causes the compiler to generate auxiliary output containing
6757 a pseudo-source listing of the generated expanded code. Like most Ada
6758 compilers, GNAT works by first transforming the high level Ada code into
6759 lower level constructs. For example, tasking operations are transformed
6760 into calls to the tasking run-time routines. A unique capability of GNAT
6761 is to list this expanded code in a form very close to normal Ada source.
6762 This is very useful in understanding the implications of various Ada
6763 usage on the efficiency of the generated code. There are many cases in
6764 Ada (e.g.@: the use of controlled types), where simple Ada statements can
6765 generate a lot of run-time code. By using @option{-gnatG} you can identify
6766 these cases, and consider whether it may be desirable to modify the coding
6767 approach to improve efficiency.
6769 The format of the output is very similar to standard Ada source, and is
6770 easily understood by an Ada programmer. The following special syntactic
6771 additions correspond to low level features used in the generated code that
6772 do not have any exact analogies in pure Ada source form. The following
6773 is a partial list of these special constructions. See the spec
6774 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6776 If the switch @option{-gnatL} is used in conjunction with
6777 @cindex @option{-gnatL} (@command{gcc})
6778 @option{-gnatG}, then the original source lines are interspersed
6779 in the expanded source (as comment lines with the original line number).
6782 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
6783 Shows the storage pool being used for an allocator.
6785 @item at end @var{procedure-name};
6786 Shows the finalization (cleanup) procedure for a scope.
6788 @item (if @var{expr} then @var{expr} else @var{expr})
6789 Conditional expression equivalent to the @code{x?y:z} construction in C.
6791 @item @var{target}^^^(@var{source})
6792 A conversion with floating-point truncation instead of rounding.
6794 @item @var{target}?(@var{source})
6795 A conversion that bypasses normal Ada semantic checking. In particular
6796 enumeration types and fixed-point types are treated simply as integers.
6798 @item @var{target}?^^^(@var{source})
6799 Combines the above two cases.
6801 @item @var{x} #/ @var{y}
6802 @itemx @var{x} #mod @var{y}
6803 @itemx @var{x} #* @var{y}
6804 @itemx @var{x} #rem @var{y}
6805 A division or multiplication of fixed-point values which are treated as
6806 integers without any kind of scaling.
6808 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
6809 Shows the storage pool associated with a @code{free} statement.
6811 @item [subtype or type declaration]
6812 Used to list an equivalent declaration for an internally generated
6813 type that is referenced elsewhere in the listing.
6815 @item freeze @var{type-name} @ovar{actions}
6816 Shows the point at which @var{type-name} is frozen, with possible
6817 associated actions to be performed at the freeze point.
6819 @item reference @var{itype}
6820 Reference (and hence definition) to internal type @var{itype}.
6822 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6823 Intrinsic function call.
6825 @item @var{label-name} : label
6826 Declaration of label @var{labelname}.
6828 @item #$ @var{subprogram-name}
6829 An implicit call to a run-time support routine
6830 (to meet the requirement of H.3.1(9) in a
6833 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
6834 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6835 @var{expr}, but handled more efficiently).
6837 @item [constraint_error]
6838 Raise the @code{Constraint_Error} exception.
6840 @item @var{expression}'reference
6841 A pointer to the result of evaluating @var{expression}.
6843 @item @var{target-type}!(@var{source-expression})
6844 An unchecked conversion of @var{source-expression} to @var{target-type}.
6846 @item [@var{numerator}/@var{denominator}]
6847 Used to represent internal real literals (that) have no exact
6848 representation in base 2-16 (for example, the result of compile time
6849 evaluation of the expression 1.0/27.0).
6853 @cindex @option{-gnatD} (@command{gcc})
6854 When used in conjunction with @option{-gnatG}, this switch causes
6855 the expanded source, as described above for
6856 @option{-gnatG} to be written to files with names
6857 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6858 instead of to the standard output file. For
6859 example, if the source file name is @file{hello.adb}, then a file
6860 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6861 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
6862 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6863 you to do source level debugging using the generated code which is
6864 sometimes useful for complex code, for example to find out exactly
6865 which part of a complex construction raised an exception. This switch
6866 also suppress generation of cross-reference information (see
6867 @option{-gnatx}) since otherwise the cross-reference information
6868 would refer to the @file{^.dg^.DG^} file, which would cause
6869 confusion since this is not the original source file.
6871 Note that @option{-gnatD} actually implies @option{-gnatG}
6872 automatically, so it is not necessary to give both options.
6873 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6875 If the switch @option{-gnatL} is used in conjunction with
6876 @cindex @option{-gnatL} (@command{gcc})
6877 @option{-gnatDG}, then the original source lines are interspersed
6878 in the expanded source (as comment lines with the original line number).
6881 @cindex @option{-gnatr} (@command{gcc})
6882 @cindex pragma Restrictions
6883 This switch causes pragma Restrictions to be treated as Restriction_Warnings
6884 so that violation of restrictions causes warnings rather than illegalities.
6885 This is useful during the development process when new restrictions are added
6886 or investigated. The switch also causes pragma Profile to be treated as
6887 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
6888 restriction warnings rather than restrictions.
6891 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
6892 @cindex @option{-gnatR} (@command{gcc})
6893 This switch controls output from the compiler of a listing showing
6894 representation information for declared types and objects. For
6895 @option{-gnatR0}, no information is output (equivalent to omitting
6896 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6897 so @option{-gnatR} with no parameter has the same effect), size and alignment
6898 information is listed for declared array and record types. For
6899 @option{-gnatR2}, size and alignment information is listed for all
6900 declared types and objects. Finally @option{-gnatR3} includes symbolic
6901 expressions for values that are computed at run time for
6902 variant records. These symbolic expressions have a mostly obvious
6903 format with #n being used to represent the value of the n'th
6904 discriminant. See source files @file{repinfo.ads/adb} in the
6905 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6906 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
6907 the output is to a file with the name @file{^file.rep^file_REP^} where
6908 file is the name of the corresponding source file.
6911 @item /REPRESENTATION_INFO
6912 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
6913 This qualifier controls output from the compiler of a listing showing
6914 representation information for declared types and objects. For
6915 @option{/REPRESENTATION_INFO=NONE}, no information is output
6916 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6917 @option{/REPRESENTATION_INFO} without option is equivalent to
6918 @option{/REPRESENTATION_INFO=ARRAYS}.
6919 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6920 information is listed for declared array and record types. For
6921 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6922 is listed for all expression information for values that are computed
6923 at run time for variant records. These symbolic expressions have a mostly
6924 obvious format with #n being used to represent the value of the n'th
6925 discriminant. See source files @file{REPINFO.ADS/ADB} in the
6926 @code{GNAT} sources for full details on the format of
6927 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
6928 If _FILE is added at the end of an option
6929 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
6930 then the output is to a file with the name @file{file_REP} where
6931 file is the name of the corresponding source file.
6933 Note that it is possible for record components to have zero size. In
6934 this case, the component clause uses an obvious extension of permitted
6935 Ada syntax, for example @code{at 0 range 0 .. -1}.
6937 Representation information requires that code be generated (since it is the
6938 code generator that lays out complex data structures). If an attempt is made
6939 to output representation information when no code is generated, for example
6940 when a subunit is compiled on its own, then no information can be generated
6941 and the compiler outputs a message to this effect.
6944 @cindex @option{-gnatS} (@command{gcc})
6945 The use of the switch @option{-gnatS} for an
6946 Ada compilation will cause the compiler to output a
6947 representation of package Standard in a form very
6948 close to standard Ada. It is not quite possible to
6949 do this entirely in standard Ada (since new
6950 numeric base types cannot be created in standard
6951 Ada), but the output is easily
6952 readable to any Ada programmer, and is useful to
6953 determine the characteristics of target dependent
6954 types in package Standard.
6957 @cindex @option{-gnatx} (@command{gcc})
6958 Normally the compiler generates full cross-referencing information in
6959 the @file{ALI} file. This information is used by a number of tools,
6960 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
6961 suppresses this information. This saves some space and may slightly
6962 speed up compilation, but means that these tools cannot be used.
6965 @node Exception Handling Control
6966 @subsection Exception Handling Control
6969 GNAT uses two methods for handling exceptions at run-time. The
6970 @code{setjmp/longjmp} method saves the context when entering
6971 a frame with an exception handler. Then when an exception is
6972 raised, the context can be restored immediately, without the
6973 need for tracing stack frames. This method provides very fast
6974 exception propagation, but introduces significant overhead for
6975 the use of exception handlers, even if no exception is raised.
6977 The other approach is called ``zero cost'' exception handling.
6978 With this method, the compiler builds static tables to describe
6979 the exception ranges. No dynamic code is required when entering
6980 a frame containing an exception handler. When an exception is
6981 raised, the tables are used to control a back trace of the
6982 subprogram invocation stack to locate the required exception
6983 handler. This method has considerably poorer performance for
6984 the propagation of exceptions, but there is no overhead for
6985 exception handlers if no exception is raised. Note that in this
6986 mode and in the context of mixed Ada and C/C++ programming,
6987 to propagate an exception through a C/C++ code, the C/C++ code
6988 must be compiled with the @option{-funwind-tables} GCC's
6991 The following switches may be used to control which of the
6992 two exception handling methods is used.
6998 @cindex @option{--RTS=sjlj} (@command{gnatmake})
6999 This switch causes the setjmp/longjmp run-time (when available) to be used
7000 for exception handling. If the default
7001 mechanism for the target is zero cost exceptions, then
7002 this switch can be used to modify this default, and must be
7003 used for all units in the partition.
7004 This option is rarely used. One case in which it may be
7005 advantageous is if you have an application where exception
7006 raising is common and the overall performance of the
7007 application is improved by favoring exception propagation.
7010 @cindex @option{--RTS=zcx} (@command{gnatmake})
7011 @cindex Zero Cost Exceptions
7012 This switch causes the zero cost approach to be used
7013 for exception handling. If this is the default mechanism for the
7014 target (see below), then this switch is unneeded. If the default
7015 mechanism for the target is setjmp/longjmp exceptions, then
7016 this switch can be used to modify this default, and must be
7017 used for all units in the partition.
7018 This option can only be used if the zero cost approach
7019 is available for the target in use, otherwise it will generate an error.
7023 The same option @option{--RTS} must be used both for @command{gcc}
7024 and @command{gnatbind}. Passing this option to @command{gnatmake}
7025 (@pxref{Switches for gnatmake}) will ensure the required consistency
7026 through the compilation and binding steps.
7028 @node Units to Sources Mapping Files
7029 @subsection Units to Sources Mapping Files
7033 @item -gnatem^^=^@var{path}
7034 @cindex @option{-gnatem} (@command{gcc})
7035 A mapping file is a way to communicate to the compiler two mappings:
7036 from unit names to file names (without any directory information) and from
7037 file names to path names (with full directory information). These mappings
7038 are used by the compiler to short-circuit the path search.
7040 The use of mapping files is not required for correct operation of the
7041 compiler, but mapping files can improve efficiency, particularly when
7042 sources are read over a slow network connection. In normal operation,
7043 you need not be concerned with the format or use of mapping files,
7044 and the @option{-gnatem} switch is not a switch that you would use
7045 explicitly. it is intended only for use by automatic tools such as
7046 @command{gnatmake} running under the project file facility. The
7047 description here of the format of mapping files is provided
7048 for completeness and for possible use by other tools.
7050 A mapping file is a sequence of sets of three lines. In each set,
7051 the first line is the unit name, in lower case, with ``@code{%s}''
7053 specs and ``@code{%b}'' appended for bodies; the second line is the
7054 file name; and the third line is the path name.
7060 /gnat/project1/sources/main.2.ada
7063 When the switch @option{-gnatem} is specified, the compiler will create
7064 in memory the two mappings from the specified file. If there is any problem
7065 (nonexistent file, truncated file or duplicate entries), no mapping will
7068 Several @option{-gnatem} switches may be specified; however, only the last
7069 one on the command line will be taken into account.
7071 When using a project file, @command{gnatmake} create a temporary mapping file
7072 and communicates it to the compiler using this switch.
7076 @node Integrated Preprocessing
7077 @subsection Integrated Preprocessing
7080 GNAT sources may be preprocessed immediately before compilation.
7081 In this case, the actual
7082 text of the source is not the text of the source file, but is derived from it
7083 through a process called preprocessing. Integrated preprocessing is specified
7084 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7085 indicates, through a text file, the preprocessing data to be used.
7086 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7089 Note that when integrated preprocessing is used, the output from the
7090 preprocessor is not written to any external file. Instead it is passed
7091 internally to the compiler. If you need to preserve the result of
7092 preprocessing in a file, then you should use @command{gnatprep}
7093 to perform the desired preprocessing in stand-alone mode.
7096 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7097 used when Integrated Preprocessing is used. The reason is that preprocessing
7098 with another Preprocessing Data file without changing the sources will
7099 not trigger recompilation without this switch.
7102 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7103 always trigger recompilation for sources that are preprocessed,
7104 because @command{gnatmake} cannot compute the checksum of the source after
7108 The actual preprocessing function is described in details in section
7109 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7110 preprocessing is triggered and parameterized.
7114 @item -gnatep=@var{file}
7115 @cindex @option{-gnatep} (@command{gcc})
7116 This switch indicates to the compiler the file name (without directory
7117 information) of the preprocessor data file to use. The preprocessor data file
7118 should be found in the source directories.
7121 A preprocessing data file is a text file with significant lines indicating
7122 how should be preprocessed either a specific source or all sources not
7123 mentioned in other lines. A significant line is a nonempty, non-comment line.
7124 Comments are similar to Ada comments.
7127 Each significant line starts with either a literal string or the character '*'.
7128 A literal string is the file name (without directory information) of the source
7129 to preprocess. A character '*' indicates the preprocessing for all the sources
7130 that are not specified explicitly on other lines (order of the lines is not
7131 significant). It is an error to have two lines with the same file name or two
7132 lines starting with the character '*'.
7135 After the file name or the character '*', another optional literal string
7136 indicating the file name of the definition file to be used for preprocessing
7137 (@pxref{Form of Definitions File}). The definition files are found by the
7138 compiler in one of the source directories. In some cases, when compiling
7139 a source in a directory other than the current directory, if the definition
7140 file is in the current directory, it may be necessary to add the current
7141 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7142 the compiler would not find the definition file.
7145 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7146 be found. Those ^switches^switches^ are:
7151 Causes both preprocessor lines and the lines deleted by
7152 preprocessing to be replaced by blank lines, preserving the line number.
7153 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7154 it cancels the effect of @option{-c}.
7157 Causes both preprocessor lines and the lines deleted
7158 by preprocessing to be retained as comments marked
7159 with the special string ``@code{--! }''.
7161 @item -Dsymbol=value
7162 Define or redefine a symbol, associated with value. A symbol is an Ada
7163 identifier, or an Ada reserved word, with the exception of @code{if},
7164 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7165 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7166 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7167 same name defined in a definition file.
7170 Causes a sorted list of symbol names and values to be
7171 listed on the standard output file.
7174 Causes undefined symbols to be treated as having the value @code{FALSE}
7176 of a preprocessor test. In the absence of this option, an undefined symbol in
7177 a @code{#if} or @code{#elsif} test will be treated as an error.
7182 Examples of valid lines in a preprocessor data file:
7185 "toto.adb" "prep.def" -u
7186 -- preprocess "toto.adb", using definition file "prep.def",
7187 -- undefined symbol are False.
7190 -- preprocess all other sources without a definition file;
7191 -- suppressed lined are commented; symbol VERSION has the value V101.
7193 "titi.adb" "prep2.def" -s
7194 -- preprocess "titi.adb", using definition file "prep2.def";
7195 -- list all symbols with their values.
7198 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7199 @cindex @option{-gnateD} (@command{gcc})
7200 Define or redefine a preprocessing symbol, associated with value. If no value
7201 is given on the command line, then the value of the symbol is @code{True}.
7202 A symbol is an identifier, following normal Ada (case-insensitive)
7203 rules for its syntax, and value is any sequence (including an empty sequence)
7204 of characters from the set (letters, digits, period, underline).
7205 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7206 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7209 A symbol declared with this ^switch^switch^ on the command line replaces a
7210 symbol with the same name either in a definition file or specified with a
7211 ^switch^switch^ -D in the preprocessor data file.
7214 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7217 When integrated preprocessing is performed and the preprocessor modifies
7218 the source text, write the result of this preprocessing into a file
7219 <source>^.prep^_prep^.
7223 @node Code Generation Control
7224 @subsection Code Generation Control
7228 The GCC technology provides a wide range of target dependent
7229 @option{-m} switches for controlling
7230 details of code generation with respect to different versions of
7231 architectures. This includes variations in instruction sets (e.g.@:
7232 different members of the power pc family), and different requirements
7233 for optimal arrangement of instructions (e.g.@: different members of
7234 the x86 family). The list of available @option{-m} switches may be
7235 found in the GCC documentation.
7237 Use of these @option{-m} switches may in some cases result in improved
7240 The GNAT Pro technology is tested and qualified without any
7241 @option{-m} switches,
7242 so generally the most reliable approach is to avoid the use of these
7243 switches. However, we generally expect most of these switches to work
7244 successfully with GNAT Pro, and many customers have reported successful
7245 use of these options.
7247 Our general advice is to avoid the use of @option{-m} switches unless
7248 special needs lead to requirements in this area. In particular,
7249 there is no point in using @option{-m} switches to improve performance
7250 unless you actually see a performance improvement.
7254 @subsection Return Codes
7255 @cindex Return Codes
7256 @cindex @option{/RETURN_CODES=VMS}
7259 On VMS, GNAT compiled programs return POSIX-style codes by default,
7260 e.g.@: @option{/RETURN_CODES=POSIX}.
7262 To enable VMS style return codes, use GNAT BIND and LINK with the option
7263 @option{/RETURN_CODES=VMS}. For example:
7266 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7267 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7271 Programs built with /RETURN_CODES=VMS are suitable to be called in
7272 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7273 are suitable for spawning with appropriate GNAT RTL routines.
7277 @node Search Paths and the Run-Time Library (RTL)
7278 @section Search Paths and the Run-Time Library (RTL)
7281 With the GNAT source-based library system, the compiler must be able to
7282 find source files for units that are needed by the unit being compiled.
7283 Search paths are used to guide this process.
7285 The compiler compiles one source file whose name must be given
7286 explicitly on the command line. In other words, no searching is done
7287 for this file. To find all other source files that are needed (the most
7288 common being the specs of units), the compiler examines the following
7289 directories, in the following order:
7293 The directory containing the source file of the main unit being compiled
7294 (the file name on the command line).
7297 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7298 @command{gcc} command line, in the order given.
7301 @findex ADA_PRJ_INCLUDE_FILE
7302 Each of the directories listed in the text file whose name is given
7303 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7306 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7307 driver when project files are used. It should not normally be set
7311 @findex ADA_INCLUDE_PATH
7312 Each of the directories listed in the value of the
7313 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7315 Construct this value
7316 exactly as the @env{PATH} environment variable: a list of directory
7317 names separated by colons (semicolons when working with the NT version).
7320 Normally, define this value as a logical name containing a comma separated
7321 list of directory names.
7323 This variable can also be defined by means of an environment string
7324 (an argument to the HP C exec* set of functions).
7328 DEFINE ANOTHER_PATH FOO:[BAG]
7329 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7332 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7333 first, followed by the standard Ada
7334 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7335 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7336 (Text_IO, Sequential_IO, etc)
7337 instead of the standard Ada packages. Thus, in order to get the standard Ada
7338 packages by default, ADA_INCLUDE_PATH must be redefined.
7342 The content of the @file{ada_source_path} file which is part of the GNAT
7343 installation tree and is used to store standard libraries such as the
7344 GNAT Run Time Library (RTL) source files.
7346 @ref{Installing a library}
7351 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7352 inhibits the use of the directory
7353 containing the source file named in the command line. You can still
7354 have this directory on your search path, but in this case it must be
7355 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7357 Specifying the switch @option{-nostdinc}
7358 inhibits the search of the default location for the GNAT Run Time
7359 Library (RTL) source files.
7361 The compiler outputs its object files and ALI files in the current
7364 Caution: The object file can be redirected with the @option{-o} switch;
7365 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7366 so the @file{ALI} file will not go to the right place. Therefore, you should
7367 avoid using the @option{-o} switch.
7371 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7372 children make up the GNAT RTL, together with the simple @code{System.IO}
7373 package used in the @code{"Hello World"} example. The sources for these units
7374 are needed by the compiler and are kept together in one directory. Not
7375 all of the bodies are needed, but all of the sources are kept together
7376 anyway. In a normal installation, you need not specify these directory
7377 names when compiling or binding. Either the environment variables or
7378 the built-in defaults cause these files to be found.
7380 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7381 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7382 consisting of child units of @code{GNAT}. This is a collection of generally
7383 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7384 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7386 Besides simplifying access to the RTL, a major use of search paths is
7387 in compiling sources from multiple directories. This can make
7388 development environments much more flexible.
7390 @node Order of Compilation Issues
7391 @section Order of Compilation Issues
7394 If, in our earlier example, there was a spec for the @code{hello}
7395 procedure, it would be contained in the file @file{hello.ads}; yet this
7396 file would not have to be explicitly compiled. This is the result of the
7397 model we chose to implement library management. Some of the consequences
7398 of this model are as follows:
7402 There is no point in compiling specs (except for package
7403 specs with no bodies) because these are compiled as needed by clients. If
7404 you attempt a useless compilation, you will receive an error message.
7405 It is also useless to compile subunits because they are compiled as needed
7409 There are no order of compilation requirements: performing a
7410 compilation never obsoletes anything. The only way you can obsolete
7411 something and require recompilations is to modify one of the
7412 source files on which it depends.
7415 There is no library as such, apart from the ALI files
7416 (@pxref{The Ada Library Information Files}, for information on the format
7417 of these files). For now we find it convenient to create separate ALI files,
7418 but eventually the information therein may be incorporated into the object
7422 When you compile a unit, the source files for the specs of all units
7423 that it @code{with}'s, all its subunits, and the bodies of any generics it
7424 instantiates must be available (reachable by the search-paths mechanism
7425 described above), or you will receive a fatal error message.
7432 The following are some typical Ada compilation command line examples:
7435 @item $ gcc -c xyz.adb
7436 Compile body in file @file{xyz.adb} with all default options.
7439 @item $ gcc -c -O2 -gnata xyz-def.adb
7442 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7445 Compile the child unit package in file @file{xyz-def.adb} with extensive
7446 optimizations, and pragma @code{Assert}/@code{Debug} statements
7449 @item $ gcc -c -gnatc abc-def.adb
7450 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7454 @node Binding Using gnatbind
7455 @chapter Binding Using @code{gnatbind}
7459 * Running gnatbind::
7460 * Switches for gnatbind::
7461 * Command-Line Access::
7462 * Search Paths for gnatbind::
7463 * Examples of gnatbind Usage::
7467 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7468 to bind compiled GNAT objects.
7470 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7471 driver (see @ref{The GNAT Driver and Project Files}).
7473 The @code{gnatbind} program performs four separate functions:
7477 Checks that a program is consistent, in accordance with the rules in
7478 Chapter 10 of the Ada Reference Manual. In particular, error
7479 messages are generated if a program uses inconsistent versions of a
7483 Checks that an acceptable order of elaboration exists for the program
7484 and issues an error message if it cannot find an order of elaboration
7485 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7488 Generates a main program incorporating the given elaboration order.
7489 This program is a small Ada package (body and spec) that
7490 must be subsequently compiled
7491 using the GNAT compiler. The necessary compilation step is usually
7492 performed automatically by @command{gnatlink}. The two most important
7493 functions of this program
7494 are to call the elaboration routines of units in an appropriate order
7495 and to call the main program.
7498 Determines the set of object files required by the given main program.
7499 This information is output in the forms of comments in the generated program,
7500 to be read by the @command{gnatlink} utility used to link the Ada application.
7503 @node Running gnatbind
7504 @section Running @code{gnatbind}
7507 The form of the @code{gnatbind} command is
7510 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7514 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7515 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7516 package in two files whose names are
7517 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7518 For example, if given the
7519 parameter @file{hello.ali}, for a main program contained in file
7520 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7521 and @file{b~hello.adb}.
7523 When doing consistency checking, the binder takes into consideration
7524 any source files it can locate. For example, if the binder determines
7525 that the given main program requires the package @code{Pack}, whose
7527 file is @file{pack.ali} and whose corresponding source spec file is
7528 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7529 (using the same search path conventions as previously described for the
7530 @command{gcc} command). If it can locate this source file, it checks that
7532 or source checksums of the source and its references to in @file{ALI} files
7533 match. In other words, any @file{ALI} files that mentions this spec must have
7534 resulted from compiling this version of the source file (or in the case
7535 where the source checksums match, a version close enough that the
7536 difference does not matter).
7538 @cindex Source files, use by binder
7539 The effect of this consistency checking, which includes source files, is
7540 that the binder ensures that the program is consistent with the latest
7541 version of the source files that can be located at bind time. Editing a
7542 source file without compiling files that depend on the source file cause
7543 error messages to be generated by the binder.
7545 For example, suppose you have a main program @file{hello.adb} and a
7546 package @code{P}, from file @file{p.ads} and you perform the following
7551 Enter @code{gcc -c hello.adb} to compile the main program.
7554 Enter @code{gcc -c p.ads} to compile package @code{P}.
7557 Edit file @file{p.ads}.
7560 Enter @code{gnatbind hello}.
7564 At this point, the file @file{p.ali} contains an out-of-date time stamp
7565 because the file @file{p.ads} has been edited. The attempt at binding
7566 fails, and the binder generates the following error messages:
7569 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7570 error: "p.ads" has been modified and must be recompiled
7574 Now both files must be recompiled as indicated, and then the bind can
7575 succeed, generating a main program. You need not normally be concerned
7576 with the contents of this file, but for reference purposes a sample
7577 binder output file is given in @ref{Example of Binder Output File}.
7579 In most normal usage, the default mode of @command{gnatbind} which is to
7580 generate the main package in Ada, as described in the previous section.
7581 In particular, this means that any Ada programmer can read and understand
7582 the generated main program. It can also be debugged just like any other
7583 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7584 @command{gnatbind} and @command{gnatlink}.
7586 However for some purposes it may be convenient to generate the main
7587 program in C rather than Ada. This may for example be helpful when you
7588 are generating a mixed language program with the main program in C. The
7589 GNAT compiler itself is an example.
7590 The use of the @option{^-C^/BIND_FILE=C^} switch
7591 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7592 be generated in C (and compiled using the gnu C compiler).
7594 @node Switches for gnatbind
7595 @section Switches for @command{gnatbind}
7598 The following switches are available with @code{gnatbind}; details will
7599 be presented in subsequent sections.
7602 * Consistency-Checking Modes::
7603 * Binder Error Message Control::
7604 * Elaboration Control::
7606 * Binding with Non-Ada Main Programs::
7607 * Binding Programs with No Main Subprogram::
7614 @cindex @option{--version} @command{gnatbind}
7615 Display Copyright and version, then exit disregarding all other options.
7618 @cindex @option{--help} @command{gnatbind}
7619 If @option{--version} was not used, display usage, then exit disregarding
7623 @cindex @option{-a} @command{gnatbind}
7624 Indicates that, if supported by the platform, the adainit procedure should
7625 be treated as an initialisation routine by the linker (a constructor). This
7626 is intended to be used by the Project Manager to automatically initialize
7627 shared Stand-Alone Libraries.
7629 @item ^-aO^/OBJECT_SEARCH^
7630 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7631 Specify directory to be searched for ALI files.
7633 @item ^-aI^/SOURCE_SEARCH^
7634 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7635 Specify directory to be searched for source file.
7637 @item ^-A^/BIND_FILE=ADA^
7638 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7639 Generate binder program in Ada (default)
7641 @item ^-b^/REPORT_ERRORS=BRIEF^
7642 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7643 Generate brief messages to @file{stderr} even if verbose mode set.
7645 @item ^-c^/NOOUTPUT^
7646 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7647 Check only, no generation of binder output file.
7649 @item ^-C^/BIND_FILE=C^
7650 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
7651 Generate binder program in C
7653 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7654 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
7655 This switch can be used to change the default task stack size value
7656 to a specified size @var{nn}, which is expressed in bytes by default, or
7657 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7659 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
7660 in effect, to completing all task specs with
7661 @smallexample @c ada
7662 pragma Storage_Size (nn);
7664 When they do not already have such a pragma.
7666 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7667 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
7668 This switch can be used to change the default secondary stack size value
7669 to a specified size @var{nn}, which is expressed in bytes by default, or
7670 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7673 The secondary stack is used to deal with functions that return a variable
7674 sized result, for example a function returning an unconstrained
7675 String. There are two ways in which this secondary stack is allocated.
7677 For most targets, the secondary stack is growing on demand and is allocated
7678 as a chain of blocks in the heap. The -D option is not very
7679 relevant. It only give some control over the size of the allocated
7680 blocks (whose size is the minimum of the default secondary stack size value,
7681 and the actual size needed for the current allocation request).
7683 For certain targets, notably VxWorks 653,
7684 the secondary stack is allocated by carving off a fixed ratio chunk of the
7685 primary task stack. The -D option is used to define the
7686 size of the environment task's secondary stack.
7688 @item ^-e^/ELABORATION_DEPENDENCIES^
7689 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
7690 Output complete list of elaboration-order dependencies.
7692 @item ^-E^/STORE_TRACEBACKS^
7693 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
7694 Store tracebacks in exception occurrences when the target supports it.
7695 This is the default with the zero cost exception mechanism.
7697 @c The following may get moved to an appendix
7698 This option is currently supported on the following targets:
7699 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
7701 See also the packages @code{GNAT.Traceback} and
7702 @code{GNAT.Traceback.Symbolic} for more information.
7704 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
7705 @command{gcc} option.
7708 @item ^-F^/FORCE_ELABS_FLAGS^
7709 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
7710 Force the checks of elaboration flags. @command{gnatbind} does not normally
7711 generate checks of elaboration flags for the main executable, except when
7712 a Stand-Alone Library is used. However, there are cases when this cannot be
7713 detected by gnatbind. An example is importing an interface of a Stand-Alone
7714 Library through a pragma Import and only specifying through a linker switch
7715 this Stand-Alone Library. This switch is used to guarantee that elaboration
7716 flag checks are generated.
7719 @cindex @option{^-h^/HELP^} (@command{gnatbind})
7720 Output usage (help) information
7723 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7724 Specify directory to be searched for source and ALI files.
7726 @item ^-I-^/NOCURRENT_DIRECTORY^
7727 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
7728 Do not look for sources in the current directory where @code{gnatbind} was
7729 invoked, and do not look for ALI files in the directory containing the
7730 ALI file named in the @code{gnatbind} command line.
7732 @item ^-l^/ORDER_OF_ELABORATION^
7733 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
7734 Output chosen elaboration order.
7736 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
7737 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
7738 Bind the units for library building. In this case the adainit and
7739 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
7740 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
7741 ^@var{xxx}final^@var{XXX}FINAL^.
7742 Implies ^-n^/NOCOMPILE^.
7744 (@xref{GNAT and Libraries}, for more details.)
7747 On OpenVMS, these init and final procedures are exported in uppercase
7748 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
7749 the init procedure will be "TOTOINIT" and the exported name of the final
7750 procedure will be "TOTOFINAL".
7753 @item ^-Mxyz^/RENAME_MAIN=xyz^
7754 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
7755 Rename generated main program from main to xyz. This option is
7756 supported on cross environments only.
7758 @item ^-m^/ERROR_LIMIT=^@var{n}
7759 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
7760 Limit number of detected errors to @var{n}, where @var{n} is
7761 in the range 1..999_999. The default value if no switch is
7762 given is 9999. Binding is terminated if the limit is exceeded.
7764 Furthermore, under Windows, the sources pointed to by the libraries path
7765 set in the registry are not searched for.
7769 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7773 @cindex @option{-nostdinc} (@command{gnatbind})
7774 Do not look for sources in the system default directory.
7777 @cindex @option{-nostdlib} (@command{gnatbind})
7778 Do not look for library files in the system default directory.
7780 @item --RTS=@var{rts-path}
7781 @cindex @option{--RTS} (@code{gnatbind})
7782 Specifies the default location of the runtime library. Same meaning as the
7783 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
7785 @item ^-o ^/OUTPUT=^@var{file}
7786 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7787 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7788 Note that if this option is used, then linking must be done manually,
7789 gnatlink cannot be used.
7791 @item ^-O^/OBJECT_LIST^
7792 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7795 @item ^-p^/PESSIMISTIC_ELABORATION^
7796 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7797 Pessimistic (worst-case) elaboration order
7800 @cindex @option{^-R^-R^} (@command{gnatbind})
7801 Output closure source list.
7803 @item ^-s^/READ_SOURCES=ALL^
7804 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7805 Require all source files to be present.
7807 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7808 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7809 Specifies the value to be used when detecting uninitialized scalar
7810 objects with pragma Initialize_Scalars.
7811 The @var{xxx} ^string specified with the switch^option^ may be either
7813 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7814 @item ``@option{^lo^LOW^}'' for the lowest possible value
7815 @item ``@option{^hi^HIGH^}'' for the highest possible value
7816 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
7817 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
7820 In addition, you can specify @option{-Sev} to indicate that the value is
7821 to be set at run time. In this case, the program will look for an environment
7822 @cindex GNAT_INIT_SCALARS
7823 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
7824 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
7825 If no environment variable is found, or if it does not have a valid value,
7826 then the default is @option{in} (invalid values).
7830 @cindex @option{-static} (@code{gnatbind})
7831 Link against a static GNAT run time.
7834 @cindex @option{-shared} (@code{gnatbind})
7835 Link against a shared GNAT run time when available.
7838 @item ^-t^/NOTIME_STAMP_CHECK^
7839 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7840 Tolerate time stamp and other consistency errors
7842 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7843 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7844 Set the time slice value to @var{n} milliseconds. If the system supports
7845 the specification of a specific time slice value, then the indicated value
7846 is used. If the system does not support specific time slice values, but
7847 does support some general notion of round-robin scheduling, then any
7848 nonzero value will activate round-robin scheduling.
7850 A value of zero is treated specially. It turns off time
7851 slicing, and in addition, indicates to the tasking run time that the
7852 semantics should match as closely as possible the Annex D
7853 requirements of the Ada RM, and in particular sets the default
7854 scheduling policy to @code{FIFO_Within_Priorities}.
7856 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
7857 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
7858 Enable dynamic stack usage, with @var{n} results stored and displayed
7859 at program termination. A result is generated when a task
7860 terminates. Results that can't be stored are displayed on the fly, at
7861 task termination. This option is currently not supported on Itanium
7862 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
7864 @item ^-v^/REPORT_ERRORS=VERBOSE^
7865 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7866 Verbose mode. Write error messages, header, summary output to
7871 @cindex @option{-w} (@code{gnatbind})
7872 Warning mode (@var{x}=s/e for suppress/treat as error)
7876 @item /WARNINGS=NORMAL
7877 @cindex @option{/WARNINGS} (@code{gnatbind})
7878 Normal warnings mode. Warnings are issued but ignored
7880 @item /WARNINGS=SUPPRESS
7881 @cindex @option{/WARNINGS} (@code{gnatbind})
7882 All warning messages are suppressed
7884 @item /WARNINGS=ERROR
7885 @cindex @option{/WARNINGS} (@code{gnatbind})
7886 Warning messages are treated as fatal errors
7889 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
7890 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
7891 Override default wide character encoding for standard Text_IO files.
7893 @item ^-x^/READ_SOURCES=NONE^
7894 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7895 Exclude source files (check object consistency only).
7898 @item /READ_SOURCES=AVAILABLE
7899 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7900 Default mode, in which sources are checked for consistency only if
7904 @item ^-y^/ENABLE_LEAP_SECONDS^
7905 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
7906 Enable leap seconds support in @code{Ada.Calendar} and its children.
7908 @item ^-z^/ZERO_MAIN^
7909 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7915 You may obtain this listing of switches by running @code{gnatbind} with
7919 @node Consistency-Checking Modes
7920 @subsection Consistency-Checking Modes
7923 As described earlier, by default @code{gnatbind} checks
7924 that object files are consistent with one another and are consistent
7925 with any source files it can locate. The following switches control binder
7930 @item ^-s^/READ_SOURCES=ALL^
7931 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
7932 Require source files to be present. In this mode, the binder must be
7933 able to locate all source files that are referenced, in order to check
7934 their consistency. In normal mode, if a source file cannot be located it
7935 is simply ignored. If you specify this switch, a missing source
7938 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
7939 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
7940 Override default wide character encoding for standard Text_IO files.
7941 Normally the default wide character encoding method used for standard
7942 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
7943 the main source input (see description of switch
7944 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
7945 use of this switch for the binder (which has the same set of
7946 possible arguments) overrides this default as specified.
7948 @item ^-x^/READ_SOURCES=NONE^
7949 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
7950 Exclude source files. In this mode, the binder only checks that ALI
7951 files are consistent with one another. Source files are not accessed.
7952 The binder runs faster in this mode, and there is still a guarantee that
7953 the resulting program is self-consistent.
7954 If a source file has been edited since it was last compiled, and you
7955 specify this switch, the binder will not detect that the object
7956 file is out of date with respect to the source file. Note that this is the
7957 mode that is automatically used by @command{gnatmake} because in this
7958 case the checking against sources has already been performed by
7959 @command{gnatmake} in the course of compilation (i.e.@: before binding).
7962 @item /READ_SOURCES=AVAILABLE
7963 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
7964 This is the default mode in which source files are checked if they are
7965 available, and ignored if they are not available.
7969 @node Binder Error Message Control
7970 @subsection Binder Error Message Control
7973 The following switches provide control over the generation of error
7974 messages from the binder:
7978 @item ^-v^/REPORT_ERRORS=VERBOSE^
7979 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7980 Verbose mode. In the normal mode, brief error messages are generated to
7981 @file{stderr}. If this switch is present, a header is written
7982 to @file{stdout} and any error messages are directed to @file{stdout}.
7983 All that is written to @file{stderr} is a brief summary message.
7985 @item ^-b^/REPORT_ERRORS=BRIEF^
7986 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
7987 Generate brief error messages to @file{stderr} even if verbose mode is
7988 specified. This is relevant only when used with the
7989 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
7993 @cindex @option{-m} (@code{gnatbind})
7994 Limits the number of error messages to @var{n}, a decimal integer in the
7995 range 1-999. The binder terminates immediately if this limit is reached.
7998 @cindex @option{-M} (@code{gnatbind})
7999 Renames the generated main program from @code{main} to @code{xxx}.
8000 This is useful in the case of some cross-building environments, where
8001 the actual main program is separate from the one generated
8005 @item ^-ws^/WARNINGS=SUPPRESS^
8006 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8008 Suppress all warning messages.
8010 @item ^-we^/WARNINGS=ERROR^
8011 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8012 Treat any warning messages as fatal errors.
8015 @item /WARNINGS=NORMAL
8016 Standard mode with warnings generated, but warnings do not get treated
8020 @item ^-t^/NOTIME_STAMP_CHECK^
8021 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8022 @cindex Time stamp checks, in binder
8023 @cindex Binder consistency checks
8024 @cindex Consistency checks, in binder
8025 The binder performs a number of consistency checks including:
8029 Check that time stamps of a given source unit are consistent
8031 Check that checksums of a given source unit are consistent
8033 Check that consistent versions of @code{GNAT} were used for compilation
8035 Check consistency of configuration pragmas as required
8039 Normally failure of such checks, in accordance with the consistency
8040 requirements of the Ada Reference Manual, causes error messages to be
8041 generated which abort the binder and prevent the output of a binder
8042 file and subsequent link to obtain an executable.
8044 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8045 into warnings, so that
8046 binding and linking can continue to completion even in the presence of such
8047 errors. The result may be a failed link (due to missing symbols), or a
8048 non-functional executable which has undefined semantics.
8049 @emph{This means that
8050 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8054 @node Elaboration Control
8055 @subsection Elaboration Control
8058 The following switches provide additional control over the elaboration
8059 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8062 @item ^-p^/PESSIMISTIC_ELABORATION^
8063 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8064 Normally the binder attempts to choose an elaboration order that is
8065 likely to minimize the likelihood of an elaboration order error resulting
8066 in raising a @code{Program_Error} exception. This switch reverses the
8067 action of the binder, and requests that it deliberately choose an order
8068 that is likely to maximize the likelihood of an elaboration error.
8069 This is useful in ensuring portability and avoiding dependence on
8070 accidental fortuitous elaboration ordering.
8072 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8074 elaboration checking is used (@option{-gnatE} switch used for compilation).
8075 This is because in the default static elaboration mode, all necessary
8076 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8077 These implicit pragmas are still respected by the binder in
8078 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8079 safe elaboration order is assured.
8082 @node Output Control
8083 @subsection Output Control
8086 The following switches allow additional control over the output
8087 generated by the binder.
8092 @item ^-A^/BIND_FILE=ADA^
8093 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8094 Generate binder program in Ada (default). The binder program is named
8095 @file{b~@var{mainprog}.adb} by default. This can be changed with
8096 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8098 @item ^-c^/NOOUTPUT^
8099 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8100 Check only. Do not generate the binder output file. In this mode the
8101 binder performs all error checks but does not generate an output file.
8103 @item ^-C^/BIND_FILE=C^
8104 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8105 Generate binder program in C. The binder program is named
8106 @file{b_@var{mainprog}.c}.
8107 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8110 @item ^-e^/ELABORATION_DEPENDENCIES^
8111 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8112 Output complete list of elaboration-order dependencies, showing the
8113 reason for each dependency. This output can be rather extensive but may
8114 be useful in diagnosing problems with elaboration order. The output is
8115 written to @file{stdout}.
8118 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8119 Output usage information. The output is written to @file{stdout}.
8121 @item ^-K^/LINKER_OPTION_LIST^
8122 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8123 Output linker options to @file{stdout}. Includes library search paths,
8124 contents of pragmas Ident and Linker_Options, and libraries added
8127 @item ^-l^/ORDER_OF_ELABORATION^
8128 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8129 Output chosen elaboration order. The output is written to @file{stdout}.
8131 @item ^-O^/OBJECT_LIST^
8132 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8133 Output full names of all the object files that must be linked to provide
8134 the Ada component of the program. The output is written to @file{stdout}.
8135 This list includes the files explicitly supplied and referenced by the user
8136 as well as implicitly referenced run-time unit files. The latter are
8137 omitted if the corresponding units reside in shared libraries. The
8138 directory names for the run-time units depend on the system configuration.
8140 @item ^-o ^/OUTPUT=^@var{file}
8141 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8142 Set name of output file to @var{file} instead of the normal
8143 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8144 binder generated body filename. In C mode you would normally give
8145 @var{file} an extension of @file{.c} because it will be a C source program.
8146 Note that if this option is used, then linking must be done manually.
8147 It is not possible to use gnatlink in this case, since it cannot locate
8150 @item ^-r^/RESTRICTION_LIST^
8151 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8152 Generate list of @code{pragma Restrictions} that could be applied to
8153 the current unit. This is useful for code audit purposes, and also may
8154 be used to improve code generation in some cases.
8158 @node Binding with Non-Ada Main Programs
8159 @subsection Binding with Non-Ada Main Programs
8162 In our description so far we have assumed that the main
8163 program is in Ada, and that the task of the binder is to generate a
8164 corresponding function @code{main} that invokes this Ada main
8165 program. GNAT also supports the building of executable programs where
8166 the main program is not in Ada, but some of the called routines are
8167 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8168 The following switch is used in this situation:
8172 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8173 No main program. The main program is not in Ada.
8177 In this case, most of the functions of the binder are still required,
8178 but instead of generating a main program, the binder generates a file
8179 containing the following callable routines:
8184 You must call this routine to initialize the Ada part of the program by
8185 calling the necessary elaboration routines. A call to @code{adainit} is
8186 required before the first call to an Ada subprogram.
8188 Note that it is assumed that the basic execution environment must be setup
8189 to be appropriate for Ada execution at the point where the first Ada
8190 subprogram is called. In particular, if the Ada code will do any
8191 floating-point operations, then the FPU must be setup in an appropriate
8192 manner. For the case of the x86, for example, full precision mode is
8193 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8194 that the FPU is in the right state.
8198 You must call this routine to perform any library-level finalization
8199 required by the Ada subprograms. A call to @code{adafinal} is required
8200 after the last call to an Ada subprogram, and before the program
8205 If the @option{^-n^/NOMAIN^} switch
8206 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8207 @cindex Binder, multiple input files
8208 is given, more than one ALI file may appear on
8209 the command line for @code{gnatbind}. The normal @dfn{closure}
8210 calculation is performed for each of the specified units. Calculating
8211 the closure means finding out the set of units involved by tracing
8212 @code{with} references. The reason it is necessary to be able to
8213 specify more than one ALI file is that a given program may invoke two or
8214 more quite separate groups of Ada units.
8216 The binder takes the name of its output file from the last specified ALI
8217 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8218 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8219 The output is an Ada unit in source form that can
8220 be compiled with GNAT unless the -C switch is used in which case the
8221 output is a C source file, which must be compiled using the C compiler.
8222 This compilation occurs automatically as part of the @command{gnatlink}
8225 Currently the GNAT run time requires a FPU using 80 bits mode
8226 precision. Under targets where this is not the default it is required to
8227 call GNAT.Float_Control.Reset before using floating point numbers (this
8228 include float computation, float input and output) in the Ada code. A
8229 side effect is that this could be the wrong mode for the foreign code
8230 where floating point computation could be broken after this call.
8232 @node Binding Programs with No Main Subprogram
8233 @subsection Binding Programs with No Main Subprogram
8236 It is possible to have an Ada program which does not have a main
8237 subprogram. This program will call the elaboration routines of all the
8238 packages, then the finalization routines.
8240 The following switch is used to bind programs organized in this manner:
8243 @item ^-z^/ZERO_MAIN^
8244 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8245 Normally the binder checks that the unit name given on the command line
8246 corresponds to a suitable main subprogram. When this switch is used,
8247 a list of ALI files can be given, and the execution of the program
8248 consists of elaboration of these units in an appropriate order. Note
8249 that the default wide character encoding method for standard Text_IO
8250 files is always set to Brackets if this switch is set (you can use
8252 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8255 @node Command-Line Access
8256 @section Command-Line Access
8259 The package @code{Ada.Command_Line} provides access to the command-line
8260 arguments and program name. In order for this interface to operate
8261 correctly, the two variables
8273 are declared in one of the GNAT library routines. These variables must
8274 be set from the actual @code{argc} and @code{argv} values passed to the
8275 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8276 generates the C main program to automatically set these variables.
8277 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8278 set these variables. If they are not set, the procedures in
8279 @code{Ada.Command_Line} will not be available, and any attempt to use
8280 them will raise @code{Constraint_Error}. If command line access is
8281 required, your main program must set @code{gnat_argc} and
8282 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8285 @node Search Paths for gnatbind
8286 @section Search Paths for @code{gnatbind}
8289 The binder takes the name of an ALI file as its argument and needs to
8290 locate source files as well as other ALI files to verify object consistency.
8292 For source files, it follows exactly the same search rules as @command{gcc}
8293 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8294 directories searched are:
8298 The directory containing the ALI file named in the command line, unless
8299 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8302 All directories specified by @option{^-I^/SEARCH^}
8303 switches on the @code{gnatbind}
8304 command line, in the order given.
8307 @findex ADA_PRJ_OBJECTS_FILE
8308 Each of the directories listed in the text file whose name is given
8309 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8312 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8313 driver when project files are used. It should not normally be set
8317 @findex ADA_OBJECTS_PATH
8318 Each of the directories listed in the value of the
8319 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8321 Construct this value
8322 exactly as the @env{PATH} environment variable: a list of directory
8323 names separated by colons (semicolons when working with the NT version
8327 Normally, define this value as a logical name containing a comma separated
8328 list of directory names.
8330 This variable can also be defined by means of an environment string
8331 (an argument to the HP C exec* set of functions).
8335 DEFINE ANOTHER_PATH FOO:[BAG]
8336 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8339 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8340 first, followed by the standard Ada
8341 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8342 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8343 (Text_IO, Sequential_IO, etc)
8344 instead of the standard Ada packages. Thus, in order to get the standard Ada
8345 packages by default, ADA_OBJECTS_PATH must be redefined.
8349 The content of the @file{ada_object_path} file which is part of the GNAT
8350 installation tree and is used to store standard libraries such as the
8351 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8354 @ref{Installing a library}
8359 In the binder the switch @option{^-I^/SEARCH^}
8360 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8361 is used to specify both source and
8362 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8363 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8364 instead if you want to specify
8365 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8366 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8367 if you want to specify library paths
8368 only. This means that for the binder
8369 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8370 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8371 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8372 The binder generates the bind file (a C language source file) in the
8373 current working directory.
8379 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8380 children make up the GNAT Run-Time Library, together with the package
8381 GNAT and its children, which contain a set of useful additional
8382 library functions provided by GNAT. The sources for these units are
8383 needed by the compiler and are kept together in one directory. The ALI
8384 files and object files generated by compiling the RTL are needed by the
8385 binder and the linker and are kept together in one directory, typically
8386 different from the directory containing the sources. In a normal
8387 installation, you need not specify these directory names when compiling
8388 or binding. Either the environment variables or the built-in defaults
8389 cause these files to be found.
8391 Besides simplifying access to the RTL, a major use of search paths is
8392 in compiling sources from multiple directories. This can make
8393 development environments much more flexible.
8395 @node Examples of gnatbind Usage
8396 @section Examples of @code{gnatbind} Usage
8399 This section contains a number of examples of using the GNAT binding
8400 utility @code{gnatbind}.
8403 @item gnatbind hello
8404 The main program @code{Hello} (source program in @file{hello.adb}) is
8405 bound using the standard switch settings. The generated main program is
8406 @file{b~hello.adb}. This is the normal, default use of the binder.
8409 @item gnatbind hello -o mainprog.adb
8412 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8414 The main program @code{Hello} (source program in @file{hello.adb}) is
8415 bound using the standard switch settings. The generated main program is
8416 @file{mainprog.adb} with the associated spec in
8417 @file{mainprog.ads}. Note that you must specify the body here not the
8418 spec, in the case where the output is in Ada. Note that if this option
8419 is used, then linking must be done manually, since gnatlink will not
8420 be able to find the generated file.
8423 @item gnatbind main -C -o mainprog.c -x
8426 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8428 The main program @code{Main} (source program in
8429 @file{main.adb}) is bound, excluding source files from the
8430 consistency checking, generating
8431 the file @file{mainprog.c}.
8434 @item gnatbind -x main_program -C -o mainprog.c
8435 This command is exactly the same as the previous example. Switches may
8436 appear anywhere in the command line, and single letter switches may be
8437 combined into a single switch.
8441 @item gnatbind -n math dbase -C -o ada-control.c
8444 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8446 The main program is in a language other than Ada, but calls to
8447 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8448 to @code{gnatbind} generates the file @file{ada-control.c} containing
8449 the @code{adainit} and @code{adafinal} routines to be called before and
8450 after accessing the Ada units.
8453 @c ------------------------------------
8454 @node Linking Using gnatlink
8455 @chapter Linking Using @command{gnatlink}
8456 @c ------------------------------------
8460 This chapter discusses @command{gnatlink}, a tool that links
8461 an Ada program and builds an executable file. This utility
8462 invokes the system linker ^(via the @command{gcc} command)^^
8463 with a correct list of object files and library references.
8464 @command{gnatlink} automatically determines the list of files and
8465 references for the Ada part of a program. It uses the binder file
8466 generated by the @command{gnatbind} to determine this list.
8468 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8469 driver (see @ref{The GNAT Driver and Project Files}).
8472 * Running gnatlink::
8473 * Switches for gnatlink::
8476 @node Running gnatlink
8477 @section Running @command{gnatlink}
8480 The form of the @command{gnatlink} command is
8483 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8484 @ovar{non-Ada objects} @ovar{linker options}
8488 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8490 or linker options) may be in any order, provided that no non-Ada object may
8491 be mistaken for a main @file{ALI} file.
8492 Any file name @file{F} without the @file{.ali}
8493 extension will be taken as the main @file{ALI} file if a file exists
8494 whose name is the concatenation of @file{F} and @file{.ali}.
8497 @file{@var{mainprog}.ali} references the ALI file of the main program.
8498 The @file{.ali} extension of this file can be omitted. From this
8499 reference, @command{gnatlink} locates the corresponding binder file
8500 @file{b~@var{mainprog}.adb} and, using the information in this file along
8501 with the list of non-Ada objects and linker options, constructs a
8502 linker command file to create the executable.
8504 The arguments other than the @command{gnatlink} switches and the main
8505 @file{ALI} file are passed to the linker uninterpreted.
8506 They typically include the names of
8507 object files for units written in other languages than Ada and any library
8508 references required to resolve references in any of these foreign language
8509 units, or in @code{Import} pragmas in any Ada units.
8511 @var{linker options} is an optional list of linker specific
8513 The default linker called by gnatlink is @command{gcc} which in
8514 turn calls the appropriate system linker.
8515 Standard options for the linker such as @option{-lmy_lib} or
8516 @option{-Ldir} can be added as is.
8517 For options that are not recognized by
8518 @command{gcc} as linker options, use the @command{gcc} switches
8519 @option{-Xlinker} or @option{-Wl,}.
8520 Refer to the GCC documentation for
8521 details. Here is an example showing how to generate a linker map:
8524 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8527 Using @var{linker options} it is possible to set the program stack and
8530 See @ref{Setting Stack Size from gnatlink} and
8531 @ref{Setting Heap Size from gnatlink}.
8534 @command{gnatlink} determines the list of objects required by the Ada
8535 program and prepends them to the list of objects passed to the linker.
8536 @command{gnatlink} also gathers any arguments set by the use of
8537 @code{pragma Linker_Options} and adds them to the list of arguments
8538 presented to the linker.
8541 @command{gnatlink} accepts the following types of extra files on the command
8542 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8543 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8544 handled according to their extension.
8547 @node Switches for gnatlink
8548 @section Switches for @command{gnatlink}
8551 The following switches are available with the @command{gnatlink} utility:
8557 @cindex @option{--version} @command{gnatlink}
8558 Display Copyright and version, then exit disregarding all other options.
8561 @cindex @option{--help} @command{gnatlink}
8562 If @option{--version} was not used, display usage, then exit disregarding
8565 @item ^-A^/BIND_FILE=ADA^
8566 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8567 The binder has generated code in Ada. This is the default.
8569 @item ^-C^/BIND_FILE=C^
8570 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8571 If instead of generating a file in Ada, the binder has generated one in
8572 C, then the linker needs to know about it. Use this switch to signal
8573 to @command{gnatlink} that the binder has generated C code rather than
8576 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8577 @cindex Command line length
8578 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8579 On some targets, the command line length is limited, and @command{gnatlink}
8580 will generate a separate file for the linker if the list of object files
8582 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8583 to be generated even if
8584 the limit is not exceeded. This is useful in some cases to deal with
8585 special situations where the command line length is exceeded.
8588 @cindex Debugging information, including
8589 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8590 The option to include debugging information causes the Ada bind file (in
8591 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8592 @option{^-g^/DEBUG^}.
8593 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8594 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8595 Without @option{^-g^/DEBUG^}, the binder removes these files by
8596 default. The same procedure apply if a C bind file was generated using
8597 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8598 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8600 @item ^-n^/NOCOMPILE^
8601 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8602 Do not compile the file generated by the binder. This may be used when
8603 a link is rerun with different options, but there is no need to recompile
8607 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8608 Causes additional information to be output, including a full list of the
8609 included object files. This switch option is most useful when you want
8610 to see what set of object files are being used in the link step.
8612 @item ^-v -v^/VERBOSE/VERBOSE^
8613 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8614 Very verbose mode. Requests that the compiler operate in verbose mode when
8615 it compiles the binder file, and that the system linker run in verbose mode.
8617 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8618 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8619 @var{exec-name} specifies an alternate name for the generated
8620 executable program. If this switch is omitted, the executable has the same
8621 name as the main unit. For example, @code{gnatlink try.ali} creates
8622 an executable called @file{^try^TRY.EXE^}.
8625 @item -b @var{target}
8626 @cindex @option{-b} (@command{gnatlink})
8627 Compile your program to run on @var{target}, which is the name of a
8628 system configuration. You must have a GNAT cross-compiler built if
8629 @var{target} is not the same as your host system.
8632 @cindex @option{-B} (@command{gnatlink})
8633 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8634 from @var{dir} instead of the default location. Only use this switch
8635 when multiple versions of the GNAT compiler are available.
8636 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8637 for further details. You would normally use the @option{-b} or
8638 @option{-V} switch instead.
8640 @item --GCC=@var{compiler_name}
8641 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8642 Program used for compiling the binder file. The default is
8643 @command{gcc}. You need to use quotes around @var{compiler_name} if
8644 @code{compiler_name} contains spaces or other separator characters.
8645 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8646 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8647 inserted after your command name. Thus in the above example the compiler
8648 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8649 A limitation of this syntax is that the name and path name of the executable
8650 itself must not include any embedded spaces. If the compiler executable is
8651 different from the default one (gcc or <prefix>-gcc), then the back-end
8652 switches in the ALI file are not used to compile the binder generated source.
8653 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8654 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8655 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8656 is taken into account. However, all the additional switches are also taken
8658 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8659 @option{--GCC="bar -x -y -z -t"}.
8661 @item --LINK=@var{name}
8662 @cindex @option{--LINK=} (@command{gnatlink})
8663 @var{name} is the name of the linker to be invoked. This is especially
8664 useful in mixed language programs since languages such as C++ require
8665 their own linker to be used. When this switch is omitted, the default
8666 name for the linker is @command{gcc}. When this switch is used, the
8667 specified linker is called instead of @command{gcc} with exactly the same
8668 parameters that would have been passed to @command{gcc} so if the desired
8669 linker requires different parameters it is necessary to use a wrapper
8670 script that massages the parameters before invoking the real linker. It
8671 may be useful to control the exact invocation by using the verbose
8677 @item /DEBUG=TRACEBACK
8678 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
8679 This qualifier causes sufficient information to be included in the
8680 executable file to allow a traceback, but does not include the full
8681 symbol information needed by the debugger.
8683 @item /IDENTIFICATION="<string>"
8684 @code{"<string>"} specifies the string to be stored in the image file
8685 identification field in the image header.
8686 It overrides any pragma @code{Ident} specified string.
8688 @item /NOINHIBIT-EXEC
8689 Generate the executable file even if there are linker warnings.
8691 @item /NOSTART_FILES
8692 Don't link in the object file containing the ``main'' transfer address.
8693 Used when linking with a foreign language main program compiled with an
8697 Prefer linking with object libraries over sharable images, even without
8703 @node The GNAT Make Program gnatmake
8704 @chapter The GNAT Make Program @command{gnatmake}
8708 * Running gnatmake::
8709 * Switches for gnatmake::
8710 * Mode Switches for gnatmake::
8711 * Notes on the Command Line::
8712 * How gnatmake Works::
8713 * Examples of gnatmake Usage::
8716 A typical development cycle when working on an Ada program consists of
8717 the following steps:
8721 Edit some sources to fix bugs.
8727 Compile all sources affected.
8737 The third step can be tricky, because not only do the modified files
8738 @cindex Dependency rules
8739 have to be compiled, but any files depending on these files must also be
8740 recompiled. The dependency rules in Ada can be quite complex, especially
8741 in the presence of overloading, @code{use} clauses, generics and inlined
8744 @command{gnatmake} automatically takes care of the third and fourth steps
8745 of this process. It determines which sources need to be compiled,
8746 compiles them, and binds and links the resulting object files.
8748 Unlike some other Ada make programs, the dependencies are always
8749 accurately recomputed from the new sources. The source based approach of
8750 the GNAT compilation model makes this possible. This means that if
8751 changes to the source program cause corresponding changes in
8752 dependencies, they will always be tracked exactly correctly by
8755 @node Running gnatmake
8756 @section Running @command{gnatmake}
8759 The usual form of the @command{gnatmake} command is
8762 $ gnatmake @ovar{switches} @var{file_name}
8763 @ovar{file_names} @ovar{mode_switches}
8767 The only required argument is one @var{file_name}, which specifies
8768 a compilation unit that is a main program. Several @var{file_names} can be
8769 specified: this will result in several executables being built.
8770 If @code{switches} are present, they can be placed before the first
8771 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8772 If @var{mode_switches} are present, they must always be placed after
8773 the last @var{file_name} and all @code{switches}.
8775 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
8776 extension may be omitted from the @var{file_name} arguments. However, if
8777 you are using non-standard extensions, then it is required that the
8778 extension be given. A relative or absolute directory path can be
8779 specified in a @var{file_name}, in which case, the input source file will
8780 be searched for in the specified directory only. Otherwise, the input
8781 source file will first be searched in the directory where
8782 @command{gnatmake} was invoked and if it is not found, it will be search on
8783 the source path of the compiler as described in
8784 @ref{Search Paths and the Run-Time Library (RTL)}.
8786 All @command{gnatmake} output (except when you specify
8787 @option{^-M^/DEPENDENCIES_LIST^}) is to
8788 @file{stderr}. The output produced by the
8789 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8792 @node Switches for gnatmake
8793 @section Switches for @command{gnatmake}
8796 You may specify any of the following switches to @command{gnatmake}:
8802 @cindex @option{--version} @command{gnatmake}
8803 Display Copyright and version, then exit disregarding all other options.
8806 @cindex @option{--help} @command{gnatmake}
8807 If @option{--version} was not used, display usage, then exit disregarding
8811 @item --GCC=@var{compiler_name}
8812 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
8813 Program used for compiling. The default is `@command{gcc}'. You need to use
8814 quotes around @var{compiler_name} if @code{compiler_name} contains
8815 spaces or other separator characters. As an example @option{--GCC="foo -x
8816 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
8817 compiler. A limitation of this syntax is that the name and path name of
8818 the executable itself must not include any embedded spaces. Note that
8819 switch @option{-c} is always inserted after your command name. Thus in the
8820 above example the compiler command that will be used by @command{gnatmake}
8821 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
8822 used, only the last @var{compiler_name} is taken into account. However,
8823 all the additional switches are also taken into account. Thus,
8824 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8825 @option{--GCC="bar -x -y -z -t"}.
8827 @item --GNATBIND=@var{binder_name}
8828 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
8829 Program used for binding. The default is `@code{gnatbind}'. You need to
8830 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8831 or other separator characters. As an example @option{--GNATBIND="bar -x
8832 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
8833 binder. Binder switches that are normally appended by @command{gnatmake}
8834 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8835 A limitation of this syntax is that the name and path name of the executable
8836 itself must not include any embedded spaces.
8838 @item --GNATLINK=@var{linker_name}
8839 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
8840 Program used for linking. The default is `@command{gnatlink}'. You need to
8841 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8842 or other separator characters. As an example @option{--GNATLINK="lan -x
8843 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
8844 linker. Linker switches that are normally appended by @command{gnatmake} to
8845 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
8846 A limitation of this syntax is that the name and path name of the executable
8847 itself must not include any embedded spaces.
8851 @item ^-a^/ALL_FILES^
8852 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
8853 Consider all files in the make process, even the GNAT internal system
8854 files (for example, the predefined Ada library files), as well as any
8855 locked files. Locked files are files whose ALI file is write-protected.
8857 @command{gnatmake} does not check these files,
8858 because the assumption is that the GNAT internal files are properly up
8859 to date, and also that any write protected ALI files have been properly
8860 installed. Note that if there is an installation problem, such that one
8861 of these files is not up to date, it will be properly caught by the
8863 You may have to specify this switch if you are working on GNAT
8864 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8865 in conjunction with @option{^-f^/FORCE_COMPILE^}
8866 if you need to recompile an entire application,
8867 including run-time files, using special configuration pragmas,
8868 such as a @code{Normalize_Scalars} pragma.
8871 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8874 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8877 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8880 @item ^-b^/ACTIONS=BIND^
8881 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
8882 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8883 compilation and binding, but no link.
8884 Can be combined with @option{^-l^/ACTIONS=LINK^}
8885 to do binding and linking. When not combined with
8886 @option{^-c^/ACTIONS=COMPILE^}
8887 all the units in the closure of the main program must have been previously
8888 compiled and must be up to date. The root unit specified by @var{file_name}
8889 may be given without extension, with the source extension or, if no GNAT
8890 Project File is specified, with the ALI file extension.
8892 @item ^-c^/ACTIONS=COMPILE^
8893 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
8894 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8895 is also specified. Do not perform linking, except if both
8896 @option{^-b^/ACTIONS=BIND^} and
8897 @option{^-l^/ACTIONS=LINK^} are also specified.
8898 If the root unit specified by @var{file_name} is not a main unit, this is the
8899 default. Otherwise @command{gnatmake} will attempt binding and linking
8900 unless all objects are up to date and the executable is more recent than
8904 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
8905 Use a temporary mapping file. A mapping file is a way to communicate to the
8906 compiler two mappings: from unit names to file names (without any directory
8907 information) and from file names to path names (with full directory
8908 information). These mappings are used by the compiler to short-circuit the path
8909 search. When @command{gnatmake} is invoked with this switch, it will create
8910 a temporary mapping file, initially populated by the project manager,
8911 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8912 Each invocation of the compiler will add the newly accessed sources to the
8913 mapping file. This will improve the source search during the next invocation
8916 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8917 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
8918 Use a specific mapping file. The file, specified as a path name (absolute or
8919 relative) by this switch, should already exist, otherwise the switch is
8920 ineffective. The specified mapping file will be communicated to the compiler.
8921 This switch is not compatible with a project file
8922 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
8923 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
8925 @item ^-d^/DISPLAY_PROGRESS^
8926 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
8927 Display progress for each source, up to date or not, as a single line
8930 completed x out of y (zz%)
8933 If the file needs to be compiled this is displayed after the invocation of
8934 the compiler. These lines are displayed even in quiet output mode.
8936 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
8937 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
8938 Put all object files and ALI file in directory @var{dir}.
8939 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
8940 and ALI files go in the current working directory.
8942 This switch cannot be used when using a project file.
8946 @cindex @option{-eL} (@command{gnatmake})
8947 Follow all symbolic links when processing project files.
8950 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
8951 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
8952 Output the commands for the compiler, the binder and the linker
8953 on ^standard output^SYS$OUTPUT^,
8954 instead of ^standard error^SYS$ERROR^.
8956 @item ^-f^/FORCE_COMPILE^
8957 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
8958 Force recompilations. Recompile all sources, even though some object
8959 files may be up to date, but don't recompile predefined or GNAT internal
8960 files or locked files (files with a write-protected ALI file),
8961 unless the @option{^-a^/ALL_FILES^} switch is also specified.
8963 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
8964 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
8965 When using project files, if some errors or warnings are detected during
8966 parsing and verbose mode is not in effect (no use of switch
8967 ^-v^/VERBOSE^), then error lines start with the full path name of the project
8968 file, rather than its simple file name.
8971 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
8972 Enable debugging. This switch is simply passed to the compiler and to the
8975 @item ^-i^/IN_PLACE^
8976 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
8977 In normal mode, @command{gnatmake} compiles all object files and ALI files
8978 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
8979 then instead object files and ALI files that already exist are overwritten
8980 in place. This means that once a large project is organized into separate
8981 directories in the desired manner, then @command{gnatmake} will automatically
8982 maintain and update this organization. If no ALI files are found on the
8983 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
8984 the new object and ALI files are created in the
8985 directory containing the source being compiled. If another organization
8986 is desired, where objects and sources are kept in different directories,
8987 a useful technique is to create dummy ALI files in the desired directories.
8988 When detecting such a dummy file, @command{gnatmake} will be forced to
8989 recompile the corresponding source file, and it will be put the resulting
8990 object and ALI files in the directory where it found the dummy file.
8992 @item ^-j^/PROCESSES=^@var{n}
8993 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
8994 @cindex Parallel make
8995 Use @var{n} processes to carry out the (re)compilations. On a
8996 multiprocessor machine compilations will occur in parallel. In the
8997 event of compilation errors, messages from various compilations might
8998 get interspersed (but @command{gnatmake} will give you the full ordered
8999 list of failing compiles at the end). If this is problematic, rerun
9000 the make process with n set to 1 to get a clean list of messages.
9002 @item ^-k^/CONTINUE_ON_ERROR^
9003 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9004 Keep going. Continue as much as possible after a compilation error. To
9005 ease the programmer's task in case of compilation errors, the list of
9006 sources for which the compile fails is given when @command{gnatmake}
9009 If @command{gnatmake} is invoked with several @file{file_names} and with this
9010 switch, if there are compilation errors when building an executable,
9011 @command{gnatmake} will not attempt to build the following executables.
9013 @item ^-l^/ACTIONS=LINK^
9014 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9015 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9016 and linking. Linking will not be performed if combined with
9017 @option{^-c^/ACTIONS=COMPILE^}
9018 but not with @option{^-b^/ACTIONS=BIND^}.
9019 When not combined with @option{^-b^/ACTIONS=BIND^}
9020 all the units in the closure of the main program must have been previously
9021 compiled and must be up to date, and the main program needs to have been bound.
9022 The root unit specified by @var{file_name}
9023 may be given without extension, with the source extension or, if no GNAT
9024 Project File is specified, with the ALI file extension.
9026 @item ^-m^/MINIMAL_RECOMPILATION^
9027 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9028 Specify that the minimum necessary amount of recompilations
9029 be performed. In this mode @command{gnatmake} ignores time
9030 stamp differences when the only
9031 modifications to a source file consist in adding/removing comments,
9032 empty lines, spaces or tabs. This means that if you have changed the
9033 comments in a source file or have simply reformatted it, using this
9034 switch will tell @command{gnatmake} not to recompile files that depend on it
9035 (provided other sources on which these files depend have undergone no
9036 semantic modifications). Note that the debugging information may be
9037 out of date with respect to the sources if the @option{-m} switch causes
9038 a compilation to be switched, so the use of this switch represents a
9039 trade-off between compilation time and accurate debugging information.
9041 @item ^-M^/DEPENDENCIES_LIST^
9042 @cindex Dependencies, producing list
9043 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9044 Check if all objects are up to date. If they are, output the object
9045 dependences to @file{stdout} in a form that can be directly exploited in
9046 a @file{Makefile}. By default, each source file is prefixed with its
9047 (relative or absolute) directory name. This name is whatever you
9048 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9049 and @option{^-I^/SEARCH^} switches. If you use
9050 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9051 @option{^-q^/QUIET^}
9052 (see below), only the source file names,
9053 without relative paths, are output. If you just specify the
9054 @option{^-M^/DEPENDENCIES_LIST^}
9055 switch, dependencies of the GNAT internal system files are omitted. This
9056 is typically what you want. If you also specify
9057 the @option{^-a^/ALL_FILES^} switch,
9058 dependencies of the GNAT internal files are also listed. Note that
9059 dependencies of the objects in external Ada libraries (see switch
9060 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9063 @item ^-n^/DO_OBJECT_CHECK^
9064 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9065 Don't compile, bind, or link. Checks if all objects are up to date.
9066 If they are not, the full name of the first file that needs to be
9067 recompiled is printed.
9068 Repeated use of this option, followed by compiling the indicated source
9069 file, will eventually result in recompiling all required units.
9071 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9072 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9073 Output executable name. The name of the final executable program will be
9074 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9075 name for the executable will be the name of the input file in appropriate form
9076 for an executable file on the host system.
9078 This switch cannot be used when invoking @command{gnatmake} with several
9081 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9082 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9083 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9084 automatically missing object directories, library directories and exec
9087 @item ^-P^/PROJECT_FILE=^@var{project}
9088 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9089 Use project file @var{project}. Only one such switch can be used.
9090 @xref{gnatmake and Project Files}.
9093 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9094 Quiet. When this flag is not set, the commands carried out by
9095 @command{gnatmake} are displayed.
9097 @item ^-s^/SWITCH_CHECK/^
9098 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9099 Recompile if compiler switches have changed since last compilation.
9100 All compiler switches but -I and -o are taken into account in the
9102 orders between different ``first letter'' switches are ignored, but
9103 orders between same switches are taken into account. For example,
9104 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9105 is equivalent to @option{-O -g}.
9107 This switch is recommended when Integrated Preprocessing is used.
9110 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9111 Unique. Recompile at most the main files. It implies -c. Combined with
9112 -f, it is equivalent to calling the compiler directly. Note that using
9113 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9114 (@pxref{Project Files and Main Subprograms}).
9116 @item ^-U^/ALL_PROJECTS^
9117 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9118 When used without a project file or with one or several mains on the command
9119 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9120 on the command line, all sources of all project files are checked and compiled
9121 if not up to date, and libraries are rebuilt, if necessary.
9124 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9125 Verbose. Display the reason for all recompilations @command{gnatmake}
9126 decides are necessary, with the highest verbosity level.
9128 @item ^-vl^/LOW_VERBOSITY^
9129 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9130 Verbosity level Low. Display fewer lines than in verbosity Medium.
9132 @item ^-vm^/MEDIUM_VERBOSITY^
9133 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9134 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9136 @item ^-vh^/HIGH_VERBOSITY^
9137 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9138 Verbosity level High. Equivalent to ^-v^/REASONS^.
9140 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9141 Indicate the verbosity of the parsing of GNAT project files.
9142 @xref{Switches Related to Project Files}.
9144 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9145 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9146 Indicate that sources that are not part of any Project File may be compiled.
9147 Normally, when using Project Files, only sources that are part of a Project
9148 File may be compile. When this switch is used, a source outside of all Project
9149 Files may be compiled. The ALI file and the object file will be put in the
9150 object directory of the main Project. The compilation switches used will only
9151 be those specified on the command line. Even when
9152 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9153 command line need to be sources of a project file.
9155 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9156 Indicate that external variable @var{name} has the value @var{value}.
9157 The Project Manager will use this value for occurrences of
9158 @code{external(name)} when parsing the project file.
9159 @xref{Switches Related to Project Files}.
9162 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9163 No main subprogram. Bind and link the program even if the unit name
9164 given on the command line is a package name. The resulting executable
9165 will execute the elaboration routines of the package and its closure,
9166 then the finalization routines.
9171 @item @command{gcc} @asis{switches}
9173 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9174 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9177 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9178 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9179 automatically treated as a compiler switch, and passed on to all
9180 compilations that are carried out.
9185 Source and library search path switches:
9189 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9190 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9191 When looking for source files also look in directory @var{dir}.
9192 The order in which source files search is undertaken is
9193 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9195 @item ^-aL^/SKIP_MISSING=^@var{dir}
9196 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9197 Consider @var{dir} as being an externally provided Ada library.
9198 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9199 files have been located in directory @var{dir}. This allows you to have
9200 missing bodies for the units in @var{dir} and to ignore out of date bodies
9201 for the same units. You still need to specify
9202 the location of the specs for these units by using the switches
9203 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9204 or @option{^-I^/SEARCH=^@var{dir}}.
9205 Note: this switch is provided for compatibility with previous versions
9206 of @command{gnatmake}. The easier method of causing standard libraries
9207 to be excluded from consideration is to write-protect the corresponding
9210 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9211 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9212 When searching for library and object files, look in directory
9213 @var{dir}. The order in which library files are searched is described in
9214 @ref{Search Paths for gnatbind}.
9216 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9217 @cindex Search paths, for @command{gnatmake}
9218 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9219 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9220 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9222 @item ^-I^/SEARCH=^@var{dir}
9223 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9224 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9225 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9227 @item ^-I-^/NOCURRENT_DIRECTORY^
9228 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9229 @cindex Source files, suppressing search
9230 Do not look for source files in the directory containing the source
9231 file named in the command line.
9232 Do not look for ALI or object files in the directory
9233 where @command{gnatmake} was invoked.
9235 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9236 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9237 @cindex Linker libraries
9238 Add directory @var{dir} to the list of directories in which the linker
9239 will search for libraries. This is equivalent to
9240 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9242 Furthermore, under Windows, the sources pointed to by the libraries path
9243 set in the registry are not searched for.
9247 @cindex @option{-nostdinc} (@command{gnatmake})
9248 Do not look for source files in the system default directory.
9251 @cindex @option{-nostdlib} (@command{gnatmake})
9252 Do not look for library files in the system default directory.
9254 @item --RTS=@var{rts-path}
9255 @cindex @option{--RTS} (@command{gnatmake})
9256 Specifies the default location of the runtime library. GNAT looks for the
9258 in the following directories, and stops as soon as a valid runtime is found
9259 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9260 @file{ada_object_path} present):
9263 @item <current directory>/$rts_path
9265 @item <default-search-dir>/$rts_path
9267 @item <default-search-dir>/rts-$rts_path
9271 The selected path is handled like a normal RTS path.
9275 @node Mode Switches for gnatmake
9276 @section Mode Switches for @command{gnatmake}
9279 The mode switches (referred to as @code{mode_switches}) allow the
9280 inclusion of switches that are to be passed to the compiler itself, the
9281 binder or the linker. The effect of a mode switch is to cause all
9282 subsequent switches up to the end of the switch list, or up to the next
9283 mode switch, to be interpreted as switches to be passed on to the
9284 designated component of GNAT.
9288 @item -cargs @var{switches}
9289 @cindex @option{-cargs} (@command{gnatmake})
9290 Compiler switches. Here @var{switches} is a list of switches
9291 that are valid switches for @command{gcc}. They will be passed on to
9292 all compile steps performed by @command{gnatmake}.
9294 @item -bargs @var{switches}
9295 @cindex @option{-bargs} (@command{gnatmake})
9296 Binder switches. Here @var{switches} is a list of switches
9297 that are valid switches for @code{gnatbind}. They will be passed on to
9298 all bind steps performed by @command{gnatmake}.
9300 @item -largs @var{switches}
9301 @cindex @option{-largs} (@command{gnatmake})
9302 Linker switches. Here @var{switches} is a list of switches
9303 that are valid switches for @command{gnatlink}. They will be passed on to
9304 all link steps performed by @command{gnatmake}.
9306 @item -margs @var{switches}
9307 @cindex @option{-margs} (@command{gnatmake})
9308 Make switches. The switches are directly interpreted by @command{gnatmake},
9309 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9313 @node Notes on the Command Line
9314 @section Notes on the Command Line
9317 This section contains some additional useful notes on the operation
9318 of the @command{gnatmake} command.
9322 @cindex Recompilation, by @command{gnatmake}
9323 If @command{gnatmake} finds no ALI files, it recompiles the main program
9324 and all other units required by the main program.
9325 This means that @command{gnatmake}
9326 can be used for the initial compile, as well as during subsequent steps of
9327 the development cycle.
9330 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9331 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9332 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9336 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9337 is used to specify both source and
9338 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9339 instead if you just want to specify
9340 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9341 if you want to specify library paths
9345 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9346 This may conveniently be used to exclude standard libraries from
9347 consideration and in particular it means that the use of the
9348 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9349 unless @option{^-a^/ALL_FILES^} is also specified.
9352 @command{gnatmake} has been designed to make the use of Ada libraries
9353 particularly convenient. Assume you have an Ada library organized
9354 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9355 of your Ada compilation units,
9356 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9357 specs of these units, but no bodies. Then to compile a unit
9358 stored in @code{main.adb}, which uses this Ada library you would just type
9362 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9365 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9366 /SKIP_MISSING=@i{[OBJ_DIR]} main
9371 Using @command{gnatmake} along with the
9372 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9373 switch provides a mechanism for avoiding unnecessary recompilations. Using
9375 you can update the comments/format of your
9376 source files without having to recompile everything. Note, however, that
9377 adding or deleting lines in a source files may render its debugging
9378 info obsolete. If the file in question is a spec, the impact is rather
9379 limited, as that debugging info will only be useful during the
9380 elaboration phase of your program. For bodies the impact can be more
9381 significant. In all events, your debugger will warn you if a source file
9382 is more recent than the corresponding object, and alert you to the fact
9383 that the debugging information may be out of date.
9386 @node How gnatmake Works
9387 @section How @command{gnatmake} Works
9390 Generally @command{gnatmake} automatically performs all necessary
9391 recompilations and you don't need to worry about how it works. However,
9392 it may be useful to have some basic understanding of the @command{gnatmake}
9393 approach and in particular to understand how it uses the results of
9394 previous compilations without incorrectly depending on them.
9396 First a definition: an object file is considered @dfn{up to date} if the
9397 corresponding ALI file exists and if all the source files listed in the
9398 dependency section of this ALI file have time stamps matching those in
9399 the ALI file. This means that neither the source file itself nor any
9400 files that it depends on have been modified, and hence there is no need
9401 to recompile this file.
9403 @command{gnatmake} works by first checking if the specified main unit is up
9404 to date. If so, no compilations are required for the main unit. If not,
9405 @command{gnatmake} compiles the main program to build a new ALI file that
9406 reflects the latest sources. Then the ALI file of the main unit is
9407 examined to find all the source files on which the main program depends,
9408 and @command{gnatmake} recursively applies the above procedure on all these
9411 This process ensures that @command{gnatmake} only trusts the dependencies
9412 in an existing ALI file if they are known to be correct. Otherwise it
9413 always recompiles to determine a new, guaranteed accurate set of
9414 dependencies. As a result the program is compiled ``upside down'' from what may
9415 be more familiar as the required order of compilation in some other Ada
9416 systems. In particular, clients are compiled before the units on which
9417 they depend. The ability of GNAT to compile in any order is critical in
9418 allowing an order of compilation to be chosen that guarantees that
9419 @command{gnatmake} will recompute a correct set of new dependencies if
9422 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9423 imported by several of the executables, it will be recompiled at most once.
9425 Note: when using non-standard naming conventions
9426 (@pxref{Using Other File Names}), changing through a configuration pragmas
9427 file the version of a source and invoking @command{gnatmake} to recompile may
9428 have no effect, if the previous version of the source is still accessible
9429 by @command{gnatmake}. It may be necessary to use the switch
9430 ^-f^/FORCE_COMPILE^.
9432 @node Examples of gnatmake Usage
9433 @section Examples of @command{gnatmake} Usage
9436 @item gnatmake hello.adb
9437 Compile all files necessary to bind and link the main program
9438 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9439 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9441 @item gnatmake main1 main2 main3
9442 Compile all files necessary to bind and link the main programs
9443 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9444 (containing unit @code{Main2}) and @file{main3.adb}
9445 (containing unit @code{Main3}) and bind and link the resulting object files
9446 to generate three executable files @file{^main1^MAIN1.EXE^},
9447 @file{^main2^MAIN2.EXE^}
9448 and @file{^main3^MAIN3.EXE^}.
9451 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9455 @item gnatmake Main_Unit /QUIET
9456 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9457 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9459 Compile all files necessary to bind and link the main program unit
9460 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9461 be done with optimization level 2 and the order of elaboration will be
9462 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9463 displaying commands it is executing.
9466 @c *************************
9467 @node Improving Performance
9468 @chapter Improving Performance
9469 @cindex Improving performance
9472 This chapter presents several topics related to program performance.
9473 It first describes some of the tradeoffs that need to be considered
9474 and some of the techniques for making your program run faster.
9475 It then documents the @command{gnatelim} tool and unused subprogram/data
9476 elimination feature, which can reduce the size of program executables.
9478 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9479 driver (see @ref{The GNAT Driver and Project Files}).
9483 * Performance Considerations::
9484 * Text_IO Suggestions::
9485 * Reducing Size of Ada Executables with gnatelim::
9486 * Reducing Size of Executables with unused subprogram/data elimination::
9490 @c *****************************
9491 @node Performance Considerations
9492 @section Performance Considerations
9495 The GNAT system provides a number of options that allow a trade-off
9500 performance of the generated code
9503 speed of compilation
9506 minimization of dependences and recompilation
9509 the degree of run-time checking.
9513 The defaults (if no options are selected) aim at improving the speed
9514 of compilation and minimizing dependences, at the expense of performance
9515 of the generated code:
9522 no inlining of subprogram calls
9525 all run-time checks enabled except overflow and elaboration checks
9529 These options are suitable for most program development purposes. This
9530 chapter describes how you can modify these choices, and also provides
9531 some guidelines on debugging optimized code.
9534 * Controlling Run-Time Checks::
9535 * Use of Restrictions::
9536 * Optimization Levels::
9537 * Debugging Optimized Code::
9538 * Inlining of Subprograms::
9539 * Other Optimization Switches::
9540 * Optimization and Strict Aliasing::
9543 * Coverage Analysis::
9547 @node Controlling Run-Time Checks
9548 @subsection Controlling Run-Time Checks
9551 By default, GNAT generates all run-time checks, except arithmetic overflow
9552 checking for integer operations and checks for access before elaboration on
9553 subprogram calls. The latter are not required in default mode, because all
9554 necessary checking is done at compile time.
9555 @cindex @option{-gnatp} (@command{gcc})
9556 @cindex @option{-gnato} (@command{gcc})
9557 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9558 be modified. @xref{Run-Time Checks}.
9560 Our experience is that the default is suitable for most development
9563 We treat integer overflow specially because these
9564 are quite expensive and in our experience are not as important as other
9565 run-time checks in the development process. Note that division by zero
9566 is not considered an overflow check, and divide by zero checks are
9567 generated where required by default.
9569 Elaboration checks are off by default, and also not needed by default, since
9570 GNAT uses a static elaboration analysis approach that avoids the need for
9571 run-time checking. This manual contains a full chapter discussing the issue
9572 of elaboration checks, and if the default is not satisfactory for your use,
9573 you should read this chapter.
9575 For validity checks, the minimal checks required by the Ada Reference
9576 Manual (for case statements and assignments to array elements) are on
9577 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9578 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9579 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9580 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9581 are also suppressed entirely if @option{-gnatp} is used.
9583 @cindex Overflow checks
9584 @cindex Checks, overflow
9587 @cindex pragma Suppress
9588 @cindex pragma Unsuppress
9589 Note that the setting of the switches controls the default setting of
9590 the checks. They may be modified using either @code{pragma Suppress} (to
9591 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9592 checks) in the program source.
9594 @node Use of Restrictions
9595 @subsection Use of Restrictions
9598 The use of pragma Restrictions allows you to control which features are
9599 permitted in your program. Apart from the obvious point that if you avoid
9600 relatively expensive features like finalization (enforceable by the use
9601 of pragma Restrictions (No_Finalization), the use of this pragma does not
9602 affect the generated code in most cases.
9604 One notable exception to this rule is that the possibility of task abort
9605 results in some distributed overhead, particularly if finalization or
9606 exception handlers are used. The reason is that certain sections of code
9607 have to be marked as non-abortable.
9609 If you use neither the @code{abort} statement, nor asynchronous transfer
9610 of control (@code{select @dots{} then abort}), then this distributed overhead
9611 is removed, which may have a general positive effect in improving
9612 overall performance. Especially code involving frequent use of tasking
9613 constructs and controlled types will show much improved performance.
9614 The relevant restrictions pragmas are
9616 @smallexample @c ada
9617 pragma Restrictions (No_Abort_Statements);
9618 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9622 It is recommended that these restriction pragmas be used if possible. Note
9623 that this also means that you can write code without worrying about the
9624 possibility of an immediate abort at any point.
9626 @node Optimization Levels
9627 @subsection Optimization Levels
9628 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9631 Without any optimization ^option,^qualifier,^
9632 the compiler's goal is to reduce the cost of
9633 compilation and to make debugging produce the expected results.
9634 Statements are independent: if you stop the program with a breakpoint between
9635 statements, you can then assign a new value to any variable or change
9636 the program counter to any other statement in the subprogram and get exactly
9637 the results you would expect from the source code.
9639 Turning on optimization makes the compiler attempt to improve the
9640 performance and/or code size at the expense of compilation time and
9641 possibly the ability to debug the program.
9644 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
9645 the last such option is the one that is effective.
9648 The default is optimization off. This results in the fastest compile
9649 times, but GNAT makes absolutely no attempt to optimize, and the
9650 generated programs are considerably larger and slower than when
9651 optimization is enabled. You can use the
9653 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
9654 @option{-O2}, @option{-O3}, and @option{-Os})
9657 @code{OPTIMIZE} qualifier
9659 to @command{gcc} to control the optimization level:
9662 @item ^-O0^/OPTIMIZE=NONE^
9663 No optimization (the default);
9664 generates unoptimized code but has
9665 the fastest compilation time.
9667 Note that many other compilers do fairly extensive optimization
9668 even if ``no optimization'' is specified. With gcc, it is
9669 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
9670 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
9671 really does mean no optimization at all. This difference between
9672 gcc and other compilers should be kept in mind when doing
9673 performance comparisons.
9675 @item ^-O1^/OPTIMIZE=SOME^
9676 Moderate optimization;
9677 optimizes reasonably well but does not
9678 degrade compilation time significantly.
9680 @item ^-O2^/OPTIMIZE=ALL^
9682 @itemx /OPTIMIZE=DEVELOPMENT
9685 generates highly optimized code and has
9686 the slowest compilation time.
9688 @item ^-O3^/OPTIMIZE=INLINING^
9689 Full optimization as in @option{-O2},
9690 and also attempts automatic inlining of small
9691 subprograms within a unit (@pxref{Inlining of Subprograms}).
9693 @item ^-Os^/OPTIMIZE=SPACE^
9694 Optimize space usage of resulting program.
9698 Higher optimization levels perform more global transformations on the
9699 program and apply more expensive analysis algorithms in order to generate
9700 faster and more compact code. The price in compilation time, and the
9701 resulting improvement in execution time,
9702 both depend on the particular application and the hardware environment.
9703 You should experiment to find the best level for your application.
9705 Since the precise set of optimizations done at each level will vary from
9706 release to release (and sometime from target to target), it is best to think
9707 of the optimization settings in general terms.
9708 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
9709 the GNU Compiler Collection (GCC)}, for details about
9710 ^the @option{-O} settings and a number of @option{-f} options that^how to^
9711 individually enable or disable specific optimizations.
9713 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
9714 been tested extensively at all optimization levels. There are some bugs
9715 which appear only with optimization turned on, but there have also been
9716 bugs which show up only in @emph{unoptimized} code. Selecting a lower
9717 level of optimization does not improve the reliability of the code
9718 generator, which in practice is highly reliable at all optimization
9721 Note regarding the use of @option{-O3}: The use of this optimization level
9722 is generally discouraged with GNAT, since it often results in larger
9723 executables which run more slowly. See further discussion of this point
9724 in @ref{Inlining of Subprograms}.
9726 @node Debugging Optimized Code
9727 @subsection Debugging Optimized Code
9728 @cindex Debugging optimized code
9729 @cindex Optimization and debugging
9732 Although it is possible to do a reasonable amount of debugging at
9734 nonzero optimization levels,
9735 the higher the level the more likely that
9738 @option{/OPTIMIZE} settings other than @code{NONE},
9739 such settings will make it more likely that
9741 source-level constructs will have been eliminated by optimization.
9742 For example, if a loop is strength-reduced, the loop
9743 control variable may be completely eliminated and thus cannot be
9744 displayed in the debugger.
9745 This can only happen at @option{-O2} or @option{-O3}.
9746 Explicit temporary variables that you code might be eliminated at
9747 ^level^setting^ @option{-O1} or higher.
9749 The use of the @option{^-g^/DEBUG^} switch,
9750 @cindex @option{^-g^/DEBUG^} (@command{gcc})
9751 which is needed for source-level debugging,
9752 affects the size of the program executable on disk,
9753 and indeed the debugging information can be quite large.
9754 However, it has no effect on the generated code (and thus does not
9755 degrade performance)
9757 Since the compiler generates debugging tables for a compilation unit before
9758 it performs optimizations, the optimizing transformations may invalidate some
9759 of the debugging data. You therefore need to anticipate certain
9760 anomalous situations that may arise while debugging optimized code.
9761 These are the most common cases:
9765 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
9767 the PC bouncing back and forth in the code. This may result from any of
9768 the following optimizations:
9772 @i{Common subexpression elimination:} using a single instance of code for a
9773 quantity that the source computes several times. As a result you
9774 may not be able to stop on what looks like a statement.
9777 @i{Invariant code motion:} moving an expression that does not change within a
9778 loop, to the beginning of the loop.
9781 @i{Instruction scheduling:} moving instructions so as to
9782 overlap loads and stores (typically) with other code, or in
9783 general to move computations of values closer to their uses. Often
9784 this causes you to pass an assignment statement without the assignment
9785 happening and then later bounce back to the statement when the
9786 value is actually needed. Placing a breakpoint on a line of code
9787 and then stepping over it may, therefore, not always cause all the
9788 expected side-effects.
9792 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
9793 two identical pieces of code are merged and the program counter suddenly
9794 jumps to a statement that is not supposed to be executed, simply because
9795 it (and the code following) translates to the same thing as the code
9796 that @emph{was} supposed to be executed. This effect is typically seen in
9797 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
9798 a @code{break} in a C @code{^switch^switch^} statement.
9801 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
9802 There are various reasons for this effect:
9806 In a subprogram prologue, a parameter may not yet have been moved to its
9810 A variable may be dead, and its register re-used. This is
9811 probably the most common cause.
9814 As mentioned above, the assignment of a value to a variable may
9818 A variable may be eliminated entirely by value propagation or
9819 other means. In this case, GCC may incorrectly generate debugging
9820 information for the variable
9824 In general, when an unexpected value appears for a local variable or parameter
9825 you should first ascertain if that value was actually computed by
9826 your program, as opposed to being incorrectly reported by the debugger.
9828 array elements in an object designated by an access value
9829 are generally less of a problem, once you have ascertained that the access
9831 Typically, this means checking variables in the preceding code and in the
9832 calling subprogram to verify that the value observed is explainable from other
9833 values (one must apply the procedure recursively to those
9834 other values); or re-running the code and stopping a little earlier
9835 (perhaps before the call) and stepping to better see how the variable obtained
9836 the value in question; or continuing to step @emph{from} the point of the
9837 strange value to see if code motion had simply moved the variable's
9842 In light of such anomalies, a recommended technique is to use @option{-O0}
9843 early in the software development cycle, when extensive debugging capabilities
9844 are most needed, and then move to @option{-O1} and later @option{-O2} as
9845 the debugger becomes less critical.
9846 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9847 a release management issue.
9849 Note that if you use @option{-g} you can then use the @command{strip} program
9850 on the resulting executable,
9851 which removes both debugging information and global symbols.
9854 @node Inlining of Subprograms
9855 @subsection Inlining of Subprograms
9858 A call to a subprogram in the current unit is inlined if all the
9859 following conditions are met:
9863 The optimization level is at least @option{-O1}.
9866 The called subprogram is suitable for inlining: It must be small enough
9867 and not contain something that @command{gcc} cannot support in inlined
9871 @cindex pragma Inline
9873 Either @code{pragma Inline} applies to the subprogram, or it is local
9874 to the unit and called once from within it, or it is small and automatic
9875 inlining (optimization level @option{-O3}) is specified.
9879 Calls to subprograms in @code{with}'ed units are normally not inlined.
9880 To achieve actual inlining (that is, replacement of the call by the code
9881 in the body of the subprogram), the following conditions must all be true.
9885 The optimization level is at least @option{-O1}.
9888 The called subprogram is suitable for inlining: It must be small enough
9889 and not contain something that @command{gcc} cannot support in inlined
9893 The call appears in a body (not in a package spec).
9896 There is a @code{pragma Inline} for the subprogram.
9899 @cindex @option{-gnatn} (@command{gcc})
9900 The @option{^-gnatn^/INLINE^} switch
9901 is used in the @command{gcc} command line
9904 Even if all these conditions are met, it may not be possible for
9905 the compiler to inline the call, due to the length of the body,
9906 or features in the body that make it impossible for the compiler
9909 Note that specifying the @option{-gnatn} switch causes additional
9910 compilation dependencies. Consider the following:
9912 @smallexample @c ada
9932 With the default behavior (no @option{-gnatn} switch specified), the
9933 compilation of the @code{Main} procedure depends only on its own source,
9934 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
9935 means that editing the body of @code{R} does not require recompiling
9938 On the other hand, the call @code{R.Q} is not inlined under these
9939 circumstances. If the @option{-gnatn} switch is present when @code{Main}
9940 is compiled, the call will be inlined if the body of @code{Q} is small
9941 enough, but now @code{Main} depends on the body of @code{R} in
9942 @file{r.adb} as well as on the spec. This means that if this body is edited,
9943 the main program must be recompiled. Note that this extra dependency
9944 occurs whether or not the call is in fact inlined by @command{gcc}.
9946 The use of front end inlining with @option{-gnatN} generates similar
9947 additional dependencies.
9949 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
9950 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
9951 can be used to prevent
9952 all inlining. This switch overrides all other conditions and ensures
9953 that no inlining occurs. The extra dependences resulting from
9954 @option{-gnatn} will still be active, even if
9955 this switch is used to suppress the resulting inlining actions.
9957 @cindex @option{-fno-inline-functions} (@command{gcc})
9958 Note: The @option{-fno-inline-functions} switch can be used to prevent
9959 automatic inlining of small subprograms if @option{-O3} is used.
9961 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
9962 Note: The @option{-fno-inline-functions-called-once} switch
9963 can be used to prevent inlining of subprograms local to the unit
9964 and called once from within it if @option{-O1} is used.
9966 Note regarding the use of @option{-O3}: There is no difference in inlining
9967 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
9968 pragma @code{Inline} assuming the use of @option{-gnatn}
9969 or @option{-gnatN} (the switches that activate inlining). If you have used
9970 pragma @code{Inline} in appropriate cases, then it is usually much better
9971 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
9972 in this case only has the effect of inlining subprograms you did not
9973 think should be inlined. We often find that the use of @option{-O3} slows
9974 down code by performing excessive inlining, leading to increased instruction
9975 cache pressure from the increased code size. So the bottom line here is
9976 that you should not automatically assume that @option{-O3} is better than
9977 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
9978 it actually improves performance.
9980 @node Other Optimization Switches
9981 @subsection Other Optimization Switches
9982 @cindex Optimization Switches
9984 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
9985 @command{gcc} optimization switches are potentially usable. These switches
9986 have not been extensively tested with GNAT but can generally be expected
9987 to work. Examples of switches in this category are
9988 @option{-funroll-loops} and
9989 the various target-specific @option{-m} options (in particular, it has been
9990 observed that @option{-march=pentium4} can significantly improve performance
9991 on appropriate machines). For full details of these switches, see
9992 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
9993 the GNU Compiler Collection (GCC)}.
9995 @node Optimization and Strict Aliasing
9996 @subsection Optimization and Strict Aliasing
9998 @cindex Strict Aliasing
9999 @cindex No_Strict_Aliasing
10002 The strong typing capabilities of Ada allow an optimizer to generate
10003 efficient code in situations where other languages would be forced to
10004 make worst case assumptions preventing such optimizations. Consider
10005 the following example:
10007 @smallexample @c ada
10010 type Int1 is new Integer;
10011 type Int2 is new Integer;
10012 type Int1A is access Int1;
10013 type Int2A is access Int2;
10020 for J in Data'Range loop
10021 if Data (J) = Int1V.all then
10022 Int2V.all := Int2V.all + 1;
10031 In this example, since the variable @code{Int1V} can only access objects
10032 of type @code{Int1}, and @code{Int2V} can only access objects of type
10033 @code{Int2}, there is no possibility that the assignment to
10034 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10035 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10036 for all iterations of the loop and avoid the extra memory reference
10037 required to dereference it each time through the loop.
10039 This kind of optimization, called strict aliasing analysis, is
10040 triggered by specifying an optimization level of @option{-O2} or
10041 higher and allows @code{GNAT} to generate more efficient code
10042 when access values are involved.
10044 However, although this optimization is always correct in terms of
10045 the formal semantics of the Ada Reference Manual, difficulties can
10046 arise if features like @code{Unchecked_Conversion} are used to break
10047 the typing system. Consider the following complete program example:
10049 @smallexample @c ada
10052 type int1 is new integer;
10053 type int2 is new integer;
10054 type a1 is access int1;
10055 type a2 is access int2;
10060 function to_a2 (Input : a1) return a2;
10063 with Unchecked_Conversion;
10065 function to_a2 (Input : a1) return a2 is
10067 new Unchecked_Conversion (a1, a2);
10069 return to_a2u (Input);
10075 with Text_IO; use Text_IO;
10077 v1 : a1 := new int1;
10078 v2 : a2 := to_a2 (v1);
10082 put_line (int1'image (v1.all));
10088 This program prints out 0 in @option{-O0} or @option{-O1}
10089 mode, but it prints out 1 in @option{-O2} mode. That's
10090 because in strict aliasing mode, the compiler can and
10091 does assume that the assignment to @code{v2.all} could not
10092 affect the value of @code{v1.all}, since different types
10095 This behavior is not a case of non-conformance with the standard, since
10096 the Ada RM specifies that an unchecked conversion where the resulting
10097 bit pattern is not a correct value of the target type can result in an
10098 abnormal value and attempting to reference an abnormal value makes the
10099 execution of a program erroneous. That's the case here since the result
10100 does not point to an object of type @code{int2}. This means that the
10101 effect is entirely unpredictable.
10103 However, although that explanation may satisfy a language
10104 lawyer, in practice an applications programmer expects an
10105 unchecked conversion involving pointers to create true
10106 aliases and the behavior of printing 1 seems plain wrong.
10107 In this case, the strict aliasing optimization is unwelcome.
10109 Indeed the compiler recognizes this possibility, and the
10110 unchecked conversion generates a warning:
10113 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10114 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10115 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10119 Unfortunately the problem is recognized when compiling the body of
10120 package @code{p2}, but the actual "bad" code is generated while
10121 compiling the body of @code{m} and this latter compilation does not see
10122 the suspicious @code{Unchecked_Conversion}.
10124 As implied by the warning message, there are approaches you can use to
10125 avoid the unwanted strict aliasing optimization in a case like this.
10127 One possibility is to simply avoid the use of @option{-O2}, but
10128 that is a bit drastic, since it throws away a number of useful
10129 optimizations that do not involve strict aliasing assumptions.
10131 A less drastic approach is to compile the program using the
10132 option @option{-fno-strict-aliasing}. Actually it is only the
10133 unit containing the dereferencing of the suspicious pointer
10134 that needs to be compiled. So in this case, if we compile
10135 unit @code{m} with this switch, then we get the expected
10136 value of zero printed. Analyzing which units might need
10137 the switch can be painful, so a more reasonable approach
10138 is to compile the entire program with options @option{-O2}
10139 and @option{-fno-strict-aliasing}. If the performance is
10140 satisfactory with this combination of options, then the
10141 advantage is that the entire issue of possible "wrong"
10142 optimization due to strict aliasing is avoided.
10144 To avoid the use of compiler switches, the configuration
10145 pragma @code{No_Strict_Aliasing} with no parameters may be
10146 used to specify that for all access types, the strict
10147 aliasing optimization should be suppressed.
10149 However, these approaches are still overkill, in that they causes
10150 all manipulations of all access values to be deoptimized. A more
10151 refined approach is to concentrate attention on the specific
10152 access type identified as problematic.
10154 First, if a careful analysis of uses of the pointer shows
10155 that there are no possible problematic references, then
10156 the warning can be suppressed by bracketing the
10157 instantiation of @code{Unchecked_Conversion} to turn
10160 @smallexample @c ada
10161 pragma Warnings (Off);
10163 new Unchecked_Conversion (a1, a2);
10164 pragma Warnings (On);
10168 Of course that approach is not appropriate for this particular
10169 example, since indeed there is a problematic reference. In this
10170 case we can take one of two other approaches.
10172 The first possibility is to move the instantiation of unchecked
10173 conversion to the unit in which the type is declared. In
10174 this example, we would move the instantiation of
10175 @code{Unchecked_Conversion} from the body of package
10176 @code{p2} to the spec of package @code{p1}. Now the
10177 warning disappears. That's because any use of the
10178 access type knows there is a suspicious unchecked
10179 conversion, and the strict aliasing optimization
10180 is automatically suppressed for the type.
10182 If it is not practical to move the unchecked conversion to the same unit
10183 in which the destination access type is declared (perhaps because the
10184 source type is not visible in that unit), you may use pragma
10185 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10186 same declarative sequence as the declaration of the access type:
10188 @smallexample @c ada
10189 type a2 is access int2;
10190 pragma No_Strict_Aliasing (a2);
10194 Here again, the compiler now knows that the strict aliasing optimization
10195 should be suppressed for any reference to type @code{a2} and the
10196 expected behavior is obtained.
10198 Finally, note that although the compiler can generate warnings for
10199 simple cases of unchecked conversions, there are tricker and more
10200 indirect ways of creating type incorrect aliases which the compiler
10201 cannot detect. Examples are the use of address overlays and unchecked
10202 conversions involving composite types containing access types as
10203 components. In such cases, no warnings are generated, but there can
10204 still be aliasing problems. One safe coding practice is to forbid the
10205 use of address clauses for type overlaying, and to allow unchecked
10206 conversion only for primitive types. This is not really a significant
10207 restriction since any possible desired effect can be achieved by
10208 unchecked conversion of access values.
10211 @node Coverage Analysis
10212 @subsection Coverage Analysis
10215 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10216 the user to determine the distribution of execution time across a program,
10217 @pxref{Profiling} for details of usage.
10221 @node Text_IO Suggestions
10222 @section @code{Text_IO} Suggestions
10223 @cindex @code{Text_IO} and performance
10226 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10227 the requirement of maintaining page and line counts. If performance
10228 is critical, a recommendation is to use @code{Stream_IO} instead of
10229 @code{Text_IO} for volume output, since this package has less overhead.
10231 If @code{Text_IO} must be used, note that by default output to the standard
10232 output and standard error files is unbuffered (this provides better
10233 behavior when output statements are used for debugging, or if the
10234 progress of a program is observed by tracking the output, e.g. by
10235 using the Unix @command{tail -f} command to watch redirected output.
10237 If you are generating large volumes of output with @code{Text_IO} and
10238 performance is an important factor, use a designated file instead
10239 of the standard output file, or change the standard output file to
10240 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10244 @node Reducing Size of Ada Executables with gnatelim
10245 @section Reducing Size of Ada Executables with @code{gnatelim}
10249 This section describes @command{gnatelim}, a tool which detects unused
10250 subprograms and helps the compiler to create a smaller executable for your
10255 * Running gnatelim::
10256 * Correcting the List of Eliminate Pragmas::
10257 * Making Your Executables Smaller::
10258 * Summary of the gnatelim Usage Cycle::
10261 @node About gnatelim
10262 @subsection About @code{gnatelim}
10265 When a program shares a set of Ada
10266 packages with other programs, it may happen that this program uses
10267 only a fraction of the subprograms defined in these packages. The code
10268 created for these unused subprograms increases the size of the executable.
10270 @code{gnatelim} tracks unused subprograms in an Ada program and
10271 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10272 subprograms that are declared but never called. By placing the list of
10273 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10274 recompiling your program, you may decrease the size of its executable,
10275 because the compiler will not generate the code for 'eliminated' subprograms.
10276 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10277 information about this pragma.
10279 @code{gnatelim} needs as its input data the name of the main subprogram
10280 and a bind file for a main subprogram.
10282 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10283 the main subprogram. @code{gnatelim} can work with both Ada and C
10284 bind files; when both are present, it uses the Ada bind file.
10285 The following commands will build the program and create the bind file:
10288 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10289 $ gnatbind main_prog
10292 Note that @code{gnatelim} needs neither object nor ALI files.
10294 @node Running gnatelim
10295 @subsection Running @code{gnatelim}
10298 @code{gnatelim} has the following command-line interface:
10301 $ gnatelim @ovar{options} name
10305 @code{name} should be a name of a source file that contains the main subprogram
10306 of a program (partition).
10308 @code{gnatelim} has the following switches:
10313 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10314 Quiet mode: by default @code{gnatelim} outputs to the standard error
10315 stream the number of program units left to be processed. This option turns
10318 @item ^-v^/VERBOSE^
10319 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10320 Verbose mode: @code{gnatelim} version information is printed as Ada
10321 comments to the standard output stream. Also, in addition to the number of
10322 program units left @code{gnatelim} will output the name of the current unit
10326 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10327 Also look for subprograms from the GNAT run time that can be eliminated. Note
10328 that when @file{gnat.adc} is produced using this switch, the entire program
10329 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10331 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10332 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10333 When looking for source files also look in directory @var{dir}. Specifying
10334 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10335 sources in the current directory.
10337 @item ^-b^/BIND_FILE=^@var{bind_file}
10338 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10339 Specifies @var{bind_file} as the bind file to process. If not set, the name
10340 of the bind file is computed from the full expanded Ada name
10341 of a main subprogram.
10343 @item ^-C^/CONFIG_FILE=^@var{config_file}
10344 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10345 Specifies a file @var{config_file} that contains configuration pragmas. The
10346 file must be specified with full path.
10348 @item ^--GCC^/COMPILER^=@var{compiler_name}
10349 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10350 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10351 available on the path.
10353 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10354 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10355 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10356 available on the path.
10360 @code{gnatelim} sends its output to the standard output stream, and all the
10361 tracing and debug information is sent to the standard error stream.
10362 In order to produce a proper GNAT configuration file
10363 @file{gnat.adc}, redirection must be used:
10367 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10370 $ gnatelim main_prog.adb > gnat.adc
10379 $ gnatelim main_prog.adb >> gnat.adc
10383 in order to append the @code{gnatelim} output to the existing contents of
10387 @node Correcting the List of Eliminate Pragmas
10388 @subsection Correcting the List of Eliminate Pragmas
10391 In some rare cases @code{gnatelim} may try to eliminate
10392 subprograms that are actually called in the program. In this case, the
10393 compiler will generate an error message of the form:
10396 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10400 You will need to manually remove the wrong @code{Eliminate} pragmas from
10401 the @file{gnat.adc} file. You should recompile your program
10402 from scratch after that, because you need a consistent @file{gnat.adc} file
10403 during the entire compilation.
10405 @node Making Your Executables Smaller
10406 @subsection Making Your Executables Smaller
10409 In order to get a smaller executable for your program you now have to
10410 recompile the program completely with the new @file{gnat.adc} file
10411 created by @code{gnatelim} in your current directory:
10414 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10418 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10419 recompile everything
10420 with the set of pragmas @code{Eliminate} that you have obtained with
10421 @command{gnatelim}).
10423 Be aware that the set of @code{Eliminate} pragmas is specific to each
10424 program. It is not recommended to merge sets of @code{Eliminate}
10425 pragmas created for different programs in one @file{gnat.adc} file.
10427 @node Summary of the gnatelim Usage Cycle
10428 @subsection Summary of the gnatelim Usage Cycle
10431 Here is a quick summary of the steps to be taken in order to reduce
10432 the size of your executables with @code{gnatelim}. You may use
10433 other GNAT options to control the optimization level,
10434 to produce the debugging information, to set search path, etc.
10438 Produce a bind file
10441 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10442 $ gnatbind main_prog
10446 Generate a list of @code{Eliminate} pragmas
10449 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10452 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10457 Recompile the application
10460 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10465 @node Reducing Size of Executables with unused subprogram/data elimination
10466 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10467 @findex unused subprogram/data elimination
10470 This section describes how you can eliminate unused subprograms and data from
10471 your executable just by setting options at compilation time.
10474 * About unused subprogram/data elimination::
10475 * Compilation options::
10476 * Example of unused subprogram/data elimination::
10479 @node About unused subprogram/data elimination
10480 @subsection About unused subprogram/data elimination
10483 By default, an executable contains all code and data of its composing objects
10484 (directly linked or coming from statically linked libraries), even data or code
10485 never used by this executable.
10487 This feature will allow you to eliminate such unused code from your
10488 executable, making it smaller (in disk and in memory).
10490 This functionality is available on all Linux platforms except for the IA-64
10491 architecture and on all cross platforms using the ELF binary file format.
10492 In both cases GNU binutils version 2.16 or later are required to enable it.
10494 @node Compilation options
10495 @subsection Compilation options
10498 The operation of eliminating the unused code and data from the final executable
10499 is directly performed by the linker.
10501 In order to do this, it has to work with objects compiled with the
10503 @option{-ffunction-sections} @option{-fdata-sections}.
10504 @cindex @option{-ffunction-sections} (@command{gcc})
10505 @cindex @option{-fdata-sections} (@command{gcc})
10506 These options are usable with C and Ada files.
10507 They will place respectively each
10508 function or data in a separate section in the resulting object file.
10510 Once the objects and static libraries are created with these options, the
10511 linker can perform the dead code elimination. You can do this by setting
10512 the @option{-Wl,--gc-sections} option to gcc command or in the
10513 @option{-largs} section of @command{gnatmake}. This will perform a
10514 garbage collection of code and data never referenced.
10516 If the linker performs a partial link (@option{-r} ld linker option), then you
10517 will need to provide one or several entry point using the
10518 @option{-e} / @option{--entry} ld option.
10520 Note that objects compiled without the @option{-ffunction-sections} and
10521 @option{-fdata-sections} options can still be linked with the executable.
10522 However, no dead code elimination will be performed on those objects (they will
10525 The GNAT static library is now compiled with -ffunction-sections and
10526 -fdata-sections on some platforms. This allows you to eliminate the unused code
10527 and data of the GNAT library from your executable.
10529 @node Example of unused subprogram/data elimination
10530 @subsection Example of unused subprogram/data elimination
10533 Here is a simple example:
10535 @smallexample @c ada
10544 Used_Data : Integer;
10545 Unused_Data : Integer;
10547 procedure Used (Data : Integer);
10548 procedure Unused (Data : Integer);
10551 package body Aux is
10552 procedure Used (Data : Integer) is
10557 procedure Unused (Data : Integer) is
10559 Unused_Data := Data;
10565 @code{Unused} and @code{Unused_Data} are never referenced in this code
10566 excerpt, and hence they may be safely removed from the final executable.
10571 $ nm test | grep used
10572 020015f0 T aux__unused
10573 02005d88 B aux__unused_data
10574 020015cc T aux__used
10575 02005d84 B aux__used_data
10577 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10578 -largs -Wl,--gc-sections
10580 $ nm test | grep used
10581 02005350 T aux__used
10582 0201ffe0 B aux__used_data
10586 It can be observed that the procedure @code{Unused} and the object
10587 @code{Unused_Data} are removed by the linker when using the
10588 appropriate options.
10590 @c ********************************
10591 @node Renaming Files Using gnatchop
10592 @chapter Renaming Files Using @code{gnatchop}
10596 This chapter discusses how to handle files with multiple units by using
10597 the @code{gnatchop} utility. This utility is also useful in renaming
10598 files to meet the standard GNAT default file naming conventions.
10601 * Handling Files with Multiple Units::
10602 * Operating gnatchop in Compilation Mode::
10603 * Command Line for gnatchop::
10604 * Switches for gnatchop::
10605 * Examples of gnatchop Usage::
10608 @node Handling Files with Multiple Units
10609 @section Handling Files with Multiple Units
10612 The basic compilation model of GNAT requires that a file submitted to the
10613 compiler have only one unit and there be a strict correspondence
10614 between the file name and the unit name.
10616 The @code{gnatchop} utility allows both of these rules to be relaxed,
10617 allowing GNAT to process files which contain multiple compilation units
10618 and files with arbitrary file names. @code{gnatchop}
10619 reads the specified file and generates one or more output files,
10620 containing one unit per file. The unit and the file name correspond,
10621 as required by GNAT.
10623 If you want to permanently restructure a set of ``foreign'' files so that
10624 they match the GNAT rules, and do the remaining development using the
10625 GNAT structure, you can simply use @command{gnatchop} once, generate the
10626 new set of files and work with them from that point on.
10628 Alternatively, if you want to keep your files in the ``foreign'' format,
10629 perhaps to maintain compatibility with some other Ada compilation
10630 system, you can set up a procedure where you use @command{gnatchop} each
10631 time you compile, regarding the source files that it writes as temporary
10632 files that you throw away.
10634 @node Operating gnatchop in Compilation Mode
10635 @section Operating gnatchop in Compilation Mode
10638 The basic function of @code{gnatchop} is to take a file with multiple units
10639 and split it into separate files. The boundary between files is reasonably
10640 clear, except for the issue of comments and pragmas. In default mode, the
10641 rule is that any pragmas between units belong to the previous unit, except
10642 that configuration pragmas always belong to the following unit. Any comments
10643 belong to the following unit. These rules
10644 almost always result in the right choice of
10645 the split point without needing to mark it explicitly and most users will
10646 find this default to be what they want. In this default mode it is incorrect to
10647 submit a file containing only configuration pragmas, or one that ends in
10648 configuration pragmas, to @code{gnatchop}.
10650 However, using a special option to activate ``compilation mode'',
10652 can perform another function, which is to provide exactly the semantics
10653 required by the RM for handling of configuration pragmas in a compilation.
10654 In the absence of configuration pragmas (at the main file level), this
10655 option has no effect, but it causes such configuration pragmas to be handled
10656 in a quite different manner.
10658 First, in compilation mode, if @code{gnatchop} is given a file that consists of
10659 only configuration pragmas, then this file is appended to the
10660 @file{gnat.adc} file in the current directory. This behavior provides
10661 the required behavior described in the RM for the actions to be taken
10662 on submitting such a file to the compiler, namely that these pragmas
10663 should apply to all subsequent compilations in the same compilation
10664 environment. Using GNAT, the current directory, possibly containing a
10665 @file{gnat.adc} file is the representation
10666 of a compilation environment. For more information on the
10667 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
10669 Second, in compilation mode, if @code{gnatchop}
10670 is given a file that starts with
10671 configuration pragmas, and contains one or more units, then these
10672 configuration pragmas are prepended to each of the chopped files. This
10673 behavior provides the required behavior described in the RM for the
10674 actions to be taken on compiling such a file, namely that the pragmas
10675 apply to all units in the compilation, but not to subsequently compiled
10678 Finally, if configuration pragmas appear between units, they are appended
10679 to the previous unit. This results in the previous unit being illegal,
10680 since the compiler does not accept configuration pragmas that follow
10681 a unit. This provides the required RM behavior that forbids configuration
10682 pragmas other than those preceding the first compilation unit of a
10685 For most purposes, @code{gnatchop} will be used in default mode. The
10686 compilation mode described above is used only if you need exactly
10687 accurate behavior with respect to compilations, and you have files
10688 that contain multiple units and configuration pragmas. In this
10689 circumstance the use of @code{gnatchop} with the compilation mode
10690 switch provides the required behavior, and is for example the mode
10691 in which GNAT processes the ACVC tests.
10693 @node Command Line for gnatchop
10694 @section Command Line for @code{gnatchop}
10697 The @code{gnatchop} command has the form:
10700 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
10705 The only required argument is the file name of the file to be chopped.
10706 There are no restrictions on the form of this file name. The file itself
10707 contains one or more Ada units, in normal GNAT format, concatenated
10708 together. As shown, more than one file may be presented to be chopped.
10710 When run in default mode, @code{gnatchop} generates one output file in
10711 the current directory for each unit in each of the files.
10713 @var{directory}, if specified, gives the name of the directory to which
10714 the output files will be written. If it is not specified, all files are
10715 written to the current directory.
10717 For example, given a
10718 file called @file{hellofiles} containing
10720 @smallexample @c ada
10725 with Text_IO; use Text_IO;
10728 Put_Line ("Hello");
10738 $ gnatchop ^hellofiles^HELLOFILES.^
10742 generates two files in the current directory, one called
10743 @file{hello.ads} containing the single line that is the procedure spec,
10744 and the other called @file{hello.adb} containing the remaining text. The
10745 original file is not affected. The generated files can be compiled in
10749 When gnatchop is invoked on a file that is empty or that contains only empty
10750 lines and/or comments, gnatchop will not fail, but will not produce any
10753 For example, given a
10754 file called @file{toto.txt} containing
10756 @smallexample @c ada
10768 $ gnatchop ^toto.txt^TOT.TXT^
10772 will not produce any new file and will result in the following warnings:
10775 toto.txt:1:01: warning: empty file, contains no compilation units
10776 no compilation units found
10777 no source files written
10780 @node Switches for gnatchop
10781 @section Switches for @code{gnatchop}
10784 @command{gnatchop} recognizes the following switches:
10790 @cindex @option{--version} @command{gnatchop}
10791 Display Copyright and version, then exit disregarding all other options.
10794 @cindex @option{--help} @command{gnatchop}
10795 If @option{--version} was not used, display usage, then exit disregarding
10798 @item ^-c^/COMPILATION^
10799 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
10800 Causes @code{gnatchop} to operate in compilation mode, in which
10801 configuration pragmas are handled according to strict RM rules. See
10802 previous section for a full description of this mode.
10805 @item -gnat@var{xxx}
10806 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
10807 used to parse the given file. Not all @var{xxx} options make sense,
10808 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
10809 process a source file that uses Latin-2 coding for identifiers.
10813 Causes @code{gnatchop} to generate a brief help summary to the standard
10814 output file showing usage information.
10816 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
10817 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
10818 Limit generated file names to the specified number @code{mm}
10820 This is useful if the
10821 resulting set of files is required to be interoperable with systems
10822 which limit the length of file names.
10824 If no value is given, or
10825 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
10826 a default of 39, suitable for OpenVMS Alpha
10827 Systems, is assumed
10830 No space is allowed between the @option{-k} and the numeric value. The numeric
10831 value may be omitted in which case a default of @option{-k8},
10833 with DOS-like file systems, is used. If no @option{-k} switch
10835 there is no limit on the length of file names.
10838 @item ^-p^/PRESERVE^
10839 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
10840 Causes the file ^modification^creation^ time stamp of the input file to be
10841 preserved and used for the time stamp of the output file(s). This may be
10842 useful for preserving coherency of time stamps in an environment where
10843 @code{gnatchop} is used as part of a standard build process.
10846 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
10847 Causes output of informational messages indicating the set of generated
10848 files to be suppressed. Warnings and error messages are unaffected.
10850 @item ^-r^/REFERENCE^
10851 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
10852 @findex Source_Reference
10853 Generate @code{Source_Reference} pragmas. Use this switch if the output
10854 files are regarded as temporary and development is to be done in terms
10855 of the original unchopped file. This switch causes
10856 @code{Source_Reference} pragmas to be inserted into each of the
10857 generated files to refers back to the original file name and line number.
10858 The result is that all error messages refer back to the original
10860 In addition, the debugging information placed into the object file (when
10861 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
10863 also refers back to this original file so that tools like profilers and
10864 debuggers will give information in terms of the original unchopped file.
10866 If the original file to be chopped itself contains
10867 a @code{Source_Reference}
10868 pragma referencing a third file, then gnatchop respects
10869 this pragma, and the generated @code{Source_Reference} pragmas
10870 in the chopped file refer to the original file, with appropriate
10871 line numbers. This is particularly useful when @code{gnatchop}
10872 is used in conjunction with @code{gnatprep} to compile files that
10873 contain preprocessing statements and multiple units.
10875 @item ^-v^/VERBOSE^
10876 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
10877 Causes @code{gnatchop} to operate in verbose mode. The version
10878 number and copyright notice are output, as well as exact copies of
10879 the gnat1 commands spawned to obtain the chop control information.
10881 @item ^-w^/OVERWRITE^
10882 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
10883 Overwrite existing file names. Normally @code{gnatchop} regards it as a
10884 fatal error if there is already a file with the same name as a
10885 file it would otherwise output, in other words if the files to be
10886 chopped contain duplicated units. This switch bypasses this
10887 check, and causes all but the last instance of such duplicated
10888 units to be skipped.
10891 @item --GCC=@var{xxxx}
10892 @cindex @option{--GCC=} (@code{gnatchop})
10893 Specify the path of the GNAT parser to be used. When this switch is used,
10894 no attempt is made to add the prefix to the GNAT parser executable.
10898 @node Examples of gnatchop Usage
10899 @section Examples of @code{gnatchop} Usage
10903 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
10906 @item gnatchop -w hello_s.ada prerelease/files
10909 Chops the source file @file{hello_s.ada}. The output files will be
10910 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
10912 files with matching names in that directory (no files in the current
10913 directory are modified).
10915 @item gnatchop ^archive^ARCHIVE.^
10916 Chops the source file @file{^archive^ARCHIVE.^}
10917 into the current directory. One
10918 useful application of @code{gnatchop} is in sending sets of sources
10919 around, for example in email messages. The required sources are simply
10920 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
10922 @command{gnatchop} is used at the other end to reconstitute the original
10925 @item gnatchop file1 file2 file3 direc
10926 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
10927 the resulting files in the directory @file{direc}. Note that if any units
10928 occur more than once anywhere within this set of files, an error message
10929 is generated, and no files are written. To override this check, use the
10930 @option{^-w^/OVERWRITE^} switch,
10931 in which case the last occurrence in the last file will
10932 be the one that is output, and earlier duplicate occurrences for a given
10933 unit will be skipped.
10936 @node Configuration Pragmas
10937 @chapter Configuration Pragmas
10938 @cindex Configuration pragmas
10939 @cindex Pragmas, configuration
10942 Configuration pragmas include those pragmas described as
10943 such in the Ada Reference Manual, as well as
10944 implementation-dependent pragmas that are configuration pragmas.
10945 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
10946 for details on these additional GNAT-specific configuration pragmas.
10947 Most notably, the pragma @code{Source_File_Name}, which allows
10948 specifying non-default names for source files, is a configuration
10949 pragma. The following is a complete list of configuration pragmas
10950 recognized by GNAT:
10962 Compile_Time_Warning
10964 Component_Alignment
10971 External_Name_Casing
10974 Float_Representation
10987 Priority_Specific_Dispatching
10990 Propagate_Exceptions
10993 Restricted_Run_Time
10995 Restrictions_Warnings
10998 Source_File_Name_Project
11001 Suppress_Exception_Locations
11002 Task_Dispatching_Policy
11008 Wide_Character_Encoding
11013 * Handling of Configuration Pragmas::
11014 * The Configuration Pragmas Files::
11017 @node Handling of Configuration Pragmas
11018 @section Handling of Configuration Pragmas
11020 Configuration pragmas may either appear at the start of a compilation
11021 unit, in which case they apply only to that unit, or they may apply to
11022 all compilations performed in a given compilation environment.
11024 GNAT also provides the @code{gnatchop} utility to provide an automatic
11025 way to handle configuration pragmas following the semantics for
11026 compilations (that is, files with multiple units), described in the RM.
11027 See @ref{Operating gnatchop in Compilation Mode} for details.
11028 However, for most purposes, it will be more convenient to edit the
11029 @file{gnat.adc} file that contains configuration pragmas directly,
11030 as described in the following section.
11032 @node The Configuration Pragmas Files
11033 @section The Configuration Pragmas Files
11034 @cindex @file{gnat.adc}
11037 In GNAT a compilation environment is defined by the current
11038 directory at the time that a compile command is given. This current
11039 directory is searched for a file whose name is @file{gnat.adc}. If
11040 this file is present, it is expected to contain one or more
11041 configuration pragmas that will be applied to the current compilation.
11042 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11045 Configuration pragmas may be entered into the @file{gnat.adc} file
11046 either by running @code{gnatchop} on a source file that consists only of
11047 configuration pragmas, or more conveniently by
11048 direct editing of the @file{gnat.adc} file, which is a standard format
11051 In addition to @file{gnat.adc}, additional files containing configuration
11052 pragmas may be applied to the current compilation using the switch
11053 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11054 contains only configuration pragmas. These configuration pragmas are
11055 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11056 is present and switch @option{-gnatA} is not used).
11058 It is allowed to specify several switches @option{-gnatec}, all of which
11059 will be taken into account.
11061 If you are using project file, a separate mechanism is provided using
11062 project attributes, see @ref{Specifying Configuration Pragmas} for more
11066 Of special interest to GNAT OpenVMS Alpha is the following
11067 configuration pragma:
11069 @smallexample @c ada
11071 pragma Extend_System (Aux_DEC);
11076 In the presence of this pragma, GNAT adds to the definition of the
11077 predefined package SYSTEM all the additional types and subprograms that are
11078 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11081 @node Handling Arbitrary File Naming Conventions Using gnatname
11082 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11083 @cindex Arbitrary File Naming Conventions
11086 * Arbitrary File Naming Conventions::
11087 * Running gnatname::
11088 * Switches for gnatname::
11089 * Examples of gnatname Usage::
11092 @node Arbitrary File Naming Conventions
11093 @section Arbitrary File Naming Conventions
11096 The GNAT compiler must be able to know the source file name of a compilation
11097 unit. When using the standard GNAT default file naming conventions
11098 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11099 does not need additional information.
11102 When the source file names do not follow the standard GNAT default file naming
11103 conventions, the GNAT compiler must be given additional information through
11104 a configuration pragmas file (@pxref{Configuration Pragmas})
11106 When the non-standard file naming conventions are well-defined,
11107 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11108 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11109 if the file naming conventions are irregular or arbitrary, a number
11110 of pragma @code{Source_File_Name} for individual compilation units
11112 To help maintain the correspondence between compilation unit names and
11113 source file names within the compiler,
11114 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11117 @node Running gnatname
11118 @section Running @code{gnatname}
11121 The usual form of the @code{gnatname} command is
11124 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11125 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11129 All of the arguments are optional. If invoked without any argument,
11130 @code{gnatname} will display its usage.
11133 When used with at least one naming pattern, @code{gnatname} will attempt to
11134 find all the compilation units in files that follow at least one of the
11135 naming patterns. To find these compilation units,
11136 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11140 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11141 Each Naming Pattern is enclosed between double quotes.
11142 A Naming Pattern is a regular expression similar to the wildcard patterns
11143 used in file names by the Unix shells or the DOS prompt.
11146 @code{gnatname} may be called with several sections of directories/patterns.
11147 Sections are separated by switch @code{--and}. In each section, there must be
11148 at least one pattern. If no directory is specified in a section, the current
11149 directory (or the project directory is @code{-P} is used) is implied.
11150 The options other that the directory switches and the patterns apply globally
11151 even if they are in different sections.
11154 Examples of Naming Patterns are
11163 For a more complete description of the syntax of Naming Patterns,
11164 see the second kind of regular expressions described in @file{g-regexp.ads}
11165 (the ``Glob'' regular expressions).
11168 When invoked with no switch @code{-P}, @code{gnatname} will create a
11169 configuration pragmas file @file{gnat.adc} in the current working directory,
11170 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11173 @node Switches for gnatname
11174 @section Switches for @code{gnatname}
11177 Switches for @code{gnatname} must precede any specified Naming Pattern.
11180 You may specify any of the following switches to @code{gnatname}:
11186 @cindex @option{--version} @command{gnatname}
11187 Display Copyright and version, then exit disregarding all other options.
11190 @cindex @option{--help} @command{gnatname}
11191 If @option{--version} was not used, display usage, then exit disregarding
11195 Start another section of directories/patterns.
11197 @item ^-c^/CONFIG_FILE=^@file{file}
11198 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11199 Create a configuration pragmas file @file{file} (instead of the default
11202 There may be zero, one or more space between @option{-c} and
11205 @file{file} may include directory information. @file{file} must be
11206 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11207 When a switch @option{^-c^/CONFIG_FILE^} is
11208 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11210 @item ^-d^/SOURCE_DIRS=^@file{dir}
11211 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11212 Look for source files in directory @file{dir}. There may be zero, one or more
11213 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11214 When a switch @option{^-d^/SOURCE_DIRS^}
11215 is specified, the current working directory will not be searched for source
11216 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11217 or @option{^-D^/DIR_FILES^} switch.
11218 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11219 If @file{dir} is a relative path, it is relative to the directory of
11220 the configuration pragmas file specified with switch
11221 @option{^-c^/CONFIG_FILE^},
11222 or to the directory of the project file specified with switch
11223 @option{^-P^/PROJECT_FILE^} or,
11224 if neither switch @option{^-c^/CONFIG_FILE^}
11225 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11226 current working directory. The directory
11227 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11229 @item ^-D^/DIRS_FILE=^@file{file}
11230 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11231 Look for source files in all directories listed in text file @file{file}.
11232 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11234 @file{file} must be an existing, readable text file.
11235 Each nonempty line in @file{file} must be a directory.
11236 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11237 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11240 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11241 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11242 Foreign patterns. Using this switch, it is possible to add sources of languages
11243 other than Ada to the list of sources of a project file.
11244 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11247 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11250 will look for Ada units in all files with the @file{.ada} extension,
11251 and will add to the list of file for project @file{prj.gpr} the C files
11252 with extension @file{.^c^C^}.
11255 @cindex @option{^-h^/HELP^} (@code{gnatname})
11256 Output usage (help) information. The output is written to @file{stdout}.
11258 @item ^-P^/PROJECT_FILE=^@file{proj}
11259 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11260 Create or update project file @file{proj}. There may be zero, one or more space
11261 between @option{-P} and @file{proj}. @file{proj} may include directory
11262 information. @file{proj} must be writable.
11263 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11264 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11265 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11267 @item ^-v^/VERBOSE^
11268 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11269 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11270 This includes name of the file written, the name of the directories to search
11271 and, for each file in those directories whose name matches at least one of
11272 the Naming Patterns, an indication of whether the file contains a unit,
11273 and if so the name of the unit.
11275 @item ^-v -v^/VERBOSE /VERBOSE^
11276 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11277 Very Verbose mode. In addition to the output produced in verbose mode,
11278 for each file in the searched directories whose name matches none of
11279 the Naming Patterns, an indication is given that there is no match.
11281 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11282 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11283 Excluded patterns. Using this switch, it is possible to exclude some files
11284 that would match the name patterns. For example,
11286 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11289 will look for Ada units in all files with the @file{.ada} extension,
11290 except those whose names end with @file{_nt.ada}.
11294 @node Examples of gnatname Usage
11295 @section Examples of @code{gnatname} Usage
11299 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11305 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11310 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11311 and be writable. In addition, the directory
11312 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11313 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11316 Note the optional spaces after @option{-c} and @option{-d}.
11321 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11322 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11325 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11326 /EXCLUDED_PATTERN=*_nt_body.ada
11327 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11328 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11332 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11333 even in conjunction with one or several switches
11334 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11335 are used in this example.
11337 @c *****************************************
11338 @c * G N A T P r o j e c t M a n a g e r *
11339 @c *****************************************
11340 @node GNAT Project Manager
11341 @chapter GNAT Project Manager
11345 * Examples of Project Files::
11346 * Project File Syntax::
11347 * Objects and Sources in Project Files::
11348 * Importing Projects::
11349 * Project Extension::
11350 * Project Hierarchy Extension::
11351 * External References in Project Files::
11352 * Packages in Project Files::
11353 * Variables from Imported Projects::
11355 * Library Projects::
11356 * Stand-alone Library Projects::
11357 * Switches Related to Project Files::
11358 * Tools Supporting Project Files::
11359 * An Extended Example::
11360 * Project File Complete Syntax::
11363 @c ****************
11364 @c * Introduction *
11365 @c ****************
11368 @section Introduction
11371 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11372 you to manage complex builds involving a number of source files, directories,
11373 and compilation options for different system configurations. In particular,
11374 project files allow you to specify:
11377 The directory or set of directories containing the source files, and/or the
11378 names of the specific source files themselves
11380 The directory in which the compiler's output
11381 (@file{ALI} files, object files, tree files) is to be placed
11383 The directory in which the executable programs is to be placed
11385 ^Switch^Switch^ settings for any of the project-enabled tools
11386 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11387 @code{gnatfind}); you can apply these settings either globally or to individual
11390 The source files containing the main subprogram(s) to be built
11392 The source programming language(s) (currently Ada and/or C)
11394 Source file naming conventions; you can specify these either globally or for
11395 individual compilation units
11402 @node Project Files
11403 @subsection Project Files
11406 Project files are written in a syntax close to that of Ada, using familiar
11407 notions such as packages, context clauses, declarations, default values,
11408 assignments, and inheritance. Finally, project files can be built
11409 hierarchically from other project files, simplifying complex system
11410 integration and project reuse.
11412 A @dfn{project} is a specific set of values for various compilation properties.
11413 The settings for a given project are described by means of
11414 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11415 Property values in project files are either strings or lists of strings.
11416 Properties that are not explicitly set receive default values. A project
11417 file may interrogate the values of @dfn{external variables} (user-defined
11418 command-line switches or environment variables), and it may specify property
11419 settings conditionally, based on the value of such variables.
11421 In simple cases, a project's source files depend only on other source files
11422 in the same project, or on the predefined libraries. (@emph{Dependence} is
11424 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11425 the Project Manager also allows more sophisticated arrangements,
11426 where the source files in one project depend on source files in other
11430 One project can @emph{import} other projects containing needed source files.
11432 You can organize GNAT projects in a hierarchy: a @emph{child} project
11433 can extend a @emph{parent} project, inheriting the parent's source files and
11434 optionally overriding any of them with alternative versions
11438 More generally, the Project Manager lets you structure large development
11439 efforts into hierarchical subsystems, where build decisions are delegated
11440 to the subsystem level, and thus different compilation environments
11441 (^switch^switch^ settings) used for different subsystems.
11443 The Project Manager is invoked through the
11444 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11445 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11447 There may be zero, one or more spaces between @option{-P} and
11448 @option{@emph{projectfile}}.
11450 If you want to define (on the command line) an external variable that is
11451 queried by the project file, you must use the
11452 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11453 The Project Manager parses and interprets the project file, and drives the
11454 invoked tool based on the project settings.
11456 The Project Manager supports a wide range of development strategies,
11457 for systems of all sizes. Here are some typical practices that are
11461 Using a common set of source files, but generating object files in different
11462 directories via different ^switch^switch^ settings
11464 Using a mostly-shared set of source files, but with different versions of
11469 The destination of an executable can be controlled inside a project file
11470 using the @option{^-o^-o^}
11472 In the absence of such a ^switch^switch^ either inside
11473 the project file or on the command line, any executable files generated by
11474 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11475 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11476 in the object directory of the project.
11478 You can use project files to achieve some of the effects of a source
11479 versioning system (for example, defining separate projects for
11480 the different sets of sources that comprise different releases) but the
11481 Project Manager is independent of any source configuration management tools
11482 that might be used by the developers.
11484 The next section introduces the main features of GNAT's project facility
11485 through a sequence of examples; subsequent sections will present the syntax
11486 and semantics in more detail. A more formal description of the project
11487 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11490 @c *****************************
11491 @c * Examples of Project Files *
11492 @c *****************************
11494 @node Examples of Project Files
11495 @section Examples of Project Files
11497 This section illustrates some of the typical uses of project files and
11498 explains their basic structure and behavior.
11501 * Common Sources with Different ^Switches^Switches^ and Directories::
11502 * Using External Variables::
11503 * Importing Other Projects::
11504 * Extending a Project::
11507 @node Common Sources with Different ^Switches^Switches^ and Directories
11508 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11512 * Specifying the Object Directory::
11513 * Specifying the Exec Directory::
11514 * Project File Packages::
11515 * Specifying ^Switch^Switch^ Settings::
11516 * Main Subprograms::
11517 * Executable File Names::
11518 * Source File Naming Conventions::
11519 * Source Language(s)::
11523 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11524 @file{proc.adb} are in the @file{/common} directory. The file
11525 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11526 package @code{Pack}. We want to compile these source files under two sets
11527 of ^switches^switches^:
11530 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11531 and the @option{^-gnata^-gnata^},
11532 @option{^-gnato^-gnato^},
11533 and @option{^-gnatE^-gnatE^} switches to the
11534 compiler; the compiler's output is to appear in @file{/common/debug}
11536 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11537 to the compiler; the compiler's output is to appear in @file{/common/release}
11541 The GNAT project files shown below, respectively @file{debug.gpr} and
11542 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11555 ^/common/debug^[COMMON.DEBUG]^
11560 ^/common/release^[COMMON.RELEASE]^
11565 Here are the corresponding project files:
11567 @smallexample @c projectfile
11570 for Object_Dir use "debug";
11571 for Main use ("proc");
11574 for ^Default_Switches^Default_Switches^ ("Ada")
11576 for Executable ("proc.adb") use "proc1";
11581 package Compiler is
11582 for ^Default_Switches^Default_Switches^ ("Ada")
11583 use ("-fstack-check",
11586 "^-gnatE^-gnatE^");
11592 @smallexample @c projectfile
11595 for Object_Dir use "release";
11596 for Exec_Dir use ".";
11597 for Main use ("proc");
11599 package Compiler is
11600 for ^Default_Switches^Default_Switches^ ("Ada")
11608 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11609 insensitive), and analogously the project defined by @file{release.gpr} is
11610 @code{"Release"}. For consistency the file should have the same name as the
11611 project, and the project file's extension should be @code{"gpr"}. These
11612 conventions are not required, but a warning is issued if they are not followed.
11614 If the current directory is @file{^/temp^[TEMP]^}, then the command
11616 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
11620 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
11621 as well as the @code{^proc1^PROC1.EXE^} executable,
11622 using the ^switch^switch^ settings defined in the project file.
11624 Likewise, the command
11626 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
11630 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
11631 and the @code{^proc^PROC.EXE^}
11632 executable in @file{^/common^[COMMON]^},
11633 using the ^switch^switch^ settings from the project file.
11636 @unnumberedsubsubsec Source Files
11639 If a project file does not explicitly specify a set of source directories or
11640 a set of source files, then by default the project's source files are the
11641 Ada source files in the project file directory. Thus @file{pack.ads},
11642 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
11644 @node Specifying the Object Directory
11645 @unnumberedsubsubsec Specifying the Object Directory
11648 Several project properties are modeled by Ada-style @emph{attributes};
11649 a property is defined by supplying the equivalent of an Ada attribute
11650 definition clause in the project file.
11651 A project's object directory is another such a property; the corresponding
11652 attribute is @code{Object_Dir}, and its value is also a string expression,
11653 specified either as absolute or relative. In the later case,
11654 it is relative to the project file directory. Thus the compiler's
11655 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
11656 (for the @code{Debug} project)
11657 and to @file{^/common/release^[COMMON.RELEASE]^}
11658 (for the @code{Release} project).
11659 If @code{Object_Dir} is not specified, then the default is the project file
11662 @node Specifying the Exec Directory
11663 @unnumberedsubsubsec Specifying the Exec Directory
11666 A project's exec directory is another property; the corresponding
11667 attribute is @code{Exec_Dir}, and its value is also a string expression,
11668 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
11669 then the default is the object directory (which may also be the project file
11670 directory if attribute @code{Object_Dir} is not specified). Thus the executable
11671 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
11672 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
11673 and in @file{^/common^[COMMON]^} for the @code{Release} project.
11675 @node Project File Packages
11676 @unnumberedsubsubsec Project File Packages
11679 A GNAT tool that is integrated with the Project Manager is modeled by a
11680 corresponding package in the project file. In the example above,
11681 The @code{Debug} project defines the packages @code{Builder}
11682 (for @command{gnatmake}) and @code{Compiler};
11683 the @code{Release} project defines only the @code{Compiler} package.
11685 The Ada-like package syntax is not to be taken literally. Although packages in
11686 project files bear a surface resemblance to packages in Ada source code, the
11687 notation is simply a way to convey a grouping of properties for a named
11688 entity. Indeed, the package names permitted in project files are restricted
11689 to a predefined set, corresponding to the project-aware tools, and the contents
11690 of packages are limited to a small set of constructs.
11691 The packages in the example above contain attribute definitions.
11693 @node Specifying ^Switch^Switch^ Settings
11694 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
11697 ^Switch^Switch^ settings for a project-aware tool can be specified through
11698 attributes in the package that corresponds to the tool.
11699 The example above illustrates one of the relevant attributes,
11700 @code{^Default_Switches^Default_Switches^}, which is defined in packages
11701 in both project files.
11702 Unlike simple attributes like @code{Source_Dirs},
11703 @code{^Default_Switches^Default_Switches^} is
11704 known as an @emph{associative array}. When you define this attribute, you must
11705 supply an ``index'' (a literal string), and the effect of the attribute
11706 definition is to set the value of the array at the specified index.
11707 For the @code{^Default_Switches^Default_Switches^} attribute,
11708 the index is a programming language (in our case, Ada),
11709 and the value specified (after @code{use}) must be a list
11710 of string expressions.
11712 The attributes permitted in project files are restricted to a predefined set.
11713 Some may appear at project level, others in packages.
11714 For any attribute that is an associative array, the index must always be a
11715 literal string, but the restrictions on this string (e.g., a file name or a
11716 language name) depend on the individual attribute.
11717 Also depending on the attribute, its specified value will need to be either a
11718 string or a string list.
11720 In the @code{Debug} project, we set the switches for two tools,
11721 @command{gnatmake} and the compiler, and thus we include the two corresponding
11722 packages; each package defines the @code{^Default_Switches^Default_Switches^}
11723 attribute with index @code{"Ada"}.
11724 Note that the package corresponding to
11725 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
11726 similar, but only includes the @code{Compiler} package.
11728 In project @code{Debug} above, the ^switches^switches^ starting with
11729 @option{-gnat} that are specified in package @code{Compiler}
11730 could have been placed in package @code{Builder}, since @command{gnatmake}
11731 transmits all such ^switches^switches^ to the compiler.
11733 @node Main Subprograms
11734 @unnumberedsubsubsec Main Subprograms
11737 One of the specifiable properties of a project is a list of files that contain
11738 main subprograms. This property is captured in the @code{Main} attribute,
11739 whose value is a list of strings. If a project defines the @code{Main}
11740 attribute, it is not necessary to identify the main subprogram(s) when
11741 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
11743 @node Executable File Names
11744 @unnumberedsubsubsec Executable File Names
11747 By default, the executable file name corresponding to a main source is
11748 deduced from the main source file name. Through the attributes
11749 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
11750 it is possible to change this default.
11751 In project @code{Debug} above, the executable file name
11752 for main source @file{^proc.adb^PROC.ADB^} is
11753 @file{^proc1^PROC1.EXE^}.
11754 Attribute @code{Executable_Suffix}, when specified, may change the suffix
11755 of the executable files, when no attribute @code{Executable} applies:
11756 its value replace the platform-specific executable suffix.
11757 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
11758 specify a non-default executable file name when several mains are built at once
11759 in a single @command{gnatmake} command.
11761 @node Source File Naming Conventions
11762 @unnumberedsubsubsec Source File Naming Conventions
11765 Since the project files above do not specify any source file naming
11766 conventions, the GNAT defaults are used. The mechanism for defining source
11767 file naming conventions -- a package named @code{Naming} --
11768 is described below (@pxref{Naming Schemes}).
11770 @node Source Language(s)
11771 @unnumberedsubsubsec Source Language(s)
11774 Since the project files do not specify a @code{Languages} attribute, by
11775 default the GNAT tools assume that the language of the project file is Ada.
11776 More generally, a project can comprise source files
11777 in Ada, C, and/or other languages.
11779 @node Using External Variables
11780 @subsection Using External Variables
11783 Instead of supplying different project files for debug and release, we can
11784 define a single project file that queries an external variable (set either
11785 on the command line or via an ^environment variable^logical name^) in order to
11786 conditionally define the appropriate settings. Again, assume that the
11787 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
11788 located in directory @file{^/common^[COMMON]^}. The following project file,
11789 @file{build.gpr}, queries the external variable named @code{STYLE} and
11790 defines an object directory and ^switch^switch^ settings based on whether
11791 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
11792 the default is @code{"deb"}.
11794 @smallexample @c projectfile
11797 for Main use ("proc");
11799 type Style_Type is ("deb", "rel");
11800 Style : Style_Type := external ("STYLE", "deb");
11804 for Object_Dir use "debug";
11807 for Object_Dir use "release";
11808 for Exec_Dir use ".";
11817 for ^Default_Switches^Default_Switches^ ("Ada")
11819 for Executable ("proc") use "proc1";
11828 package Compiler is
11832 for ^Default_Switches^Default_Switches^ ("Ada")
11833 use ("^-gnata^-gnata^",
11835 "^-gnatE^-gnatE^");
11838 for ^Default_Switches^Default_Switches^ ("Ada")
11849 @code{Style_Type} is an example of a @emph{string type}, which is the project
11850 file analog of an Ada enumeration type but whose components are string literals
11851 rather than identifiers. @code{Style} is declared as a variable of this type.
11853 The form @code{external("STYLE", "deb")} is known as an
11854 @emph{external reference}; its first argument is the name of an
11855 @emph{external variable}, and the second argument is a default value to be
11856 used if the external variable doesn't exist. You can define an external
11857 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
11858 or you can use ^an environment variable^a logical name^
11859 as an external variable.
11861 Each @code{case} construct is expanded by the Project Manager based on the
11862 value of @code{Style}. Thus the command
11865 gnatmake -P/common/build.gpr -XSTYLE=deb
11871 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
11876 is equivalent to the @command{gnatmake} invocation using the project file
11877 @file{debug.gpr} in the earlier example. So is the command
11879 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
11883 since @code{"deb"} is the default for @code{STYLE}.
11889 gnatmake -P/common/build.gpr -XSTYLE=rel
11895 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
11900 is equivalent to the @command{gnatmake} invocation using the project file
11901 @file{release.gpr} in the earlier example.
11903 @node Importing Other Projects
11904 @subsection Importing Other Projects
11905 @cindex @code{ADA_PROJECT_PATH}
11908 A compilation unit in a source file in one project may depend on compilation
11909 units in source files in other projects. To compile this unit under
11910 control of a project file, the
11911 dependent project must @emph{import} the projects containing the needed source
11913 This effect is obtained using syntax similar to an Ada @code{with} clause,
11914 but where @code{with}ed entities are strings that denote project files.
11916 As an example, suppose that the two projects @code{GUI_Proj} and
11917 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
11918 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
11919 and @file{^/comm^[COMM]^}, respectively.
11920 Suppose that the source files for @code{GUI_Proj} are
11921 @file{gui.ads} and @file{gui.adb}, and that the source files for
11922 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
11923 files is located in its respective project file directory. Schematically:
11942 We want to develop an application in directory @file{^/app^[APP]^} that
11943 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
11944 the corresponding project files (e.g.@: the ^switch^switch^ settings
11945 and object directory).
11946 Skeletal code for a main procedure might be something like the following:
11948 @smallexample @c ada
11951 procedure App_Main is
11960 Here is a project file, @file{app_proj.gpr}, that achieves the desired
11963 @smallexample @c projectfile
11965 with "/gui/gui_proj", "/comm/comm_proj";
11966 project App_Proj is
11967 for Main use ("app_main");
11973 Building an executable is achieved through the command:
11975 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
11978 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
11979 in the directory where @file{app_proj.gpr} resides.
11981 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
11982 (as illustrated above) the @code{with} clause can omit the extension.
11984 Our example specified an absolute path for each imported project file.
11985 Alternatively, the directory name of an imported object can be omitted
11989 The imported project file is in the same directory as the importing project
11992 You have defined ^an environment variable^a logical name^
11993 that includes the directory containing
11994 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
11995 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
11996 directory names separated by colons (semicolons on Windows).
12000 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
12001 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12004 @smallexample @c projectfile
12006 with "gui_proj", "comm_proj";
12007 project App_Proj is
12008 for Main use ("app_main");
12014 Importing other projects can create ambiguities.
12015 For example, the same unit might be present in different imported projects, or
12016 it might be present in both the importing project and in an imported project.
12017 Both of these conditions are errors. Note that in the current version of
12018 the Project Manager, it is illegal to have an ambiguous unit even if the
12019 unit is never referenced by the importing project. This restriction may be
12020 relaxed in a future release.
12022 @node Extending a Project
12023 @subsection Extending a Project
12026 In large software systems it is common to have multiple
12027 implementations of a common interface; in Ada terms, multiple versions of a
12028 package body for the same spec. For example, one implementation
12029 might be safe for use in tasking programs, while another might only be used
12030 in sequential applications. This can be modeled in GNAT using the concept
12031 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12032 another project (the ``parent'') then by default all source files of the
12033 parent project are inherited by the child, but the child project can
12034 override any of the parent's source files with new versions, and can also
12035 add new files. This facility is the project analog of a type extension in
12036 Object-Oriented Programming. Project hierarchies are permitted (a child
12037 project may be the parent of yet another project), and a project that
12038 inherits one project can also import other projects.
12040 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12041 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12042 @file{pack.adb}, and @file{proc.adb}:
12055 Note that the project file can simply be empty (that is, no attribute or
12056 package is defined):
12058 @smallexample @c projectfile
12060 project Seq_Proj is
12066 implying that its source files are all the Ada source files in the project
12069 Suppose we want to supply an alternate version of @file{pack.adb}, in
12070 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12071 @file{pack.ads} and @file{proc.adb}. We can define a project
12072 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12076 ^/tasking^[TASKING]^
12082 project Tasking_Proj extends "/seq/seq_proj" is
12088 The version of @file{pack.adb} used in a build depends on which project file
12091 Note that we could have obtained the desired behavior using project import
12092 rather than project inheritance; a @code{base} project would contain the
12093 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12094 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12095 would import @code{base} and add a different version of @file{pack.adb}. The
12096 choice depends on whether other sources in the original project need to be
12097 overridden. If they do, then project extension is necessary, otherwise,
12098 importing is sufficient.
12101 In a project file that extends another project file, it is possible to
12102 indicate that an inherited source is not part of the sources of the extending
12103 project. This is necessary sometimes when a package spec has been overloaded
12104 and no longer requires a body: in this case, it is necessary to indicate that
12105 the inherited body is not part of the sources of the project, otherwise there
12106 will be a compilation error when compiling the spec.
12108 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12109 Its value is a string list: a list of file names. It is also possible to use
12110 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12111 the file name of a text file containing a list of file names, one per line.
12113 @smallexample @c @projectfile
12114 project B extends "a" is
12115 for Source_Files use ("pkg.ads");
12116 -- New spec of Pkg does not need a completion
12117 for Excluded_Source_Files use ("pkg.adb");
12121 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12122 is still needed: if it is possible to build using @command{gnatmake} when such
12123 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12124 it is possible to remove the source completely from a system that includes
12127 @c ***********************
12128 @c * Project File Syntax *
12129 @c ***********************
12131 @node Project File Syntax
12132 @section Project File Syntax
12136 * Qualified Projects::
12142 * Associative Array Attributes::
12143 * case Constructions::
12147 This section describes the structure of project files.
12149 A project may be an @emph{independent project}, entirely defined by a single
12150 project file. Any Ada source file in an independent project depends only
12151 on the predefined library and other Ada source files in the same project.
12154 A project may also @dfn{depend on} other projects, in either or both of
12155 the following ways:
12157 @item It may import any number of projects
12158 @item It may extend at most one other project
12162 The dependence relation is a directed acyclic graph (the subgraph reflecting
12163 the ``extends'' relation is a tree).
12165 A project's @dfn{immediate sources} are the source files directly defined by
12166 that project, either implicitly by residing in the project file's directory,
12167 or explicitly through any of the source-related attributes described below.
12168 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12169 of @var{proj} together with the immediate sources (unless overridden) of any
12170 project on which @var{proj} depends (either directly or indirectly).
12173 @subsection Basic Syntax
12176 As seen in the earlier examples, project files have an Ada-like syntax.
12177 The minimal project file is:
12178 @smallexample @c projectfile
12187 The identifier @code{Empty} is the name of the project.
12188 This project name must be present after the reserved
12189 word @code{end} at the end of the project file, followed by a semi-colon.
12191 Any name in a project file, such as the project name or a variable name,
12192 has the same syntax as an Ada identifier.
12194 The reserved words of project files are the Ada 95 reserved words plus
12195 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12196 reserved words currently used in project file syntax are:
12232 Comments in project files have the same syntax as in Ada, two consecutive
12233 hyphens through the end of the line.
12235 @node Qualified Projects
12236 @subsection Qualified Projects
12239 Before the reserved @code{project}, there may be one or two "qualifiers", that
12240 is identifiers or other reserved words, to qualify the project.
12242 The current list of qualifiers is:
12246 @code{abstract}: qualify a project with no sources. An abstract project must
12247 have a declaration specifying that there are no sources in the project, and,
12248 if it extends another project, the project it extends must also be a qualified
12252 @code{standard}: a standard project is a non library project with sources.
12255 @code{aggregate}: for future extension
12258 @code{aggregate library}: for future extension
12261 @code{library}: a library project must declare both attributes
12262 @code{Library_Name} and @code{Library_Dir}.
12265 @code{configuration}: a configuration project cannot be in a project tree.
12269 @subsection Packages
12272 A project file may contain @emph{packages}. The name of a package must be one
12273 of the identifiers from the following list. A package
12274 with a given name may only appear once in a project file. Package names are
12275 case insensitive. The following package names are legal:
12291 @code{Cross_Reference}
12295 @code{Pretty_Printer}
12305 @code{Language_Processing}
12309 In its simplest form, a package may be empty:
12311 @smallexample @c projectfile
12321 A package may contain @emph{attribute declarations},
12322 @emph{variable declarations} and @emph{case constructions}, as will be
12325 When there is ambiguity between a project name and a package name,
12326 the name always designates the project. To avoid possible confusion, it is
12327 always a good idea to avoid naming a project with one of the
12328 names allowed for packages or any name that starts with @code{gnat}.
12331 @subsection Expressions
12334 An @emph{expression} is either a @emph{string expression} or a
12335 @emph{string list expression}.
12337 A @emph{string expression} is either a @emph{simple string expression} or a
12338 @emph{compound string expression}.
12340 A @emph{simple string expression} is one of the following:
12342 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12343 @item A string-valued variable reference (@pxref{Variables})
12344 @item A string-valued attribute reference (@pxref{Attributes})
12345 @item An external reference (@pxref{External References in Project Files})
12349 A @emph{compound string expression} is a concatenation of string expressions,
12350 using the operator @code{"&"}
12352 Path & "/" & File_Name & ".ads"
12356 A @emph{string list expression} is either a
12357 @emph{simple string list expression} or a
12358 @emph{compound string list expression}.
12360 A @emph{simple string list expression} is one of the following:
12362 @item A parenthesized list of zero or more string expressions,
12363 separated by commas
12365 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12368 @item A string list-valued variable reference
12369 @item A string list-valued attribute reference
12373 A @emph{compound string list expression} is the concatenation (using
12374 @code{"&"}) of a simple string list expression and an expression. Note that
12375 each term in a compound string list expression, except the first, may be
12376 either a string expression or a string list expression.
12378 @smallexample @c projectfile
12380 File_Name_List := () & File_Name; -- One string in this list
12381 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12383 Big_List := File_Name_List & Extended_File_Name_List;
12384 -- Concatenation of two string lists: three strings
12385 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12386 -- Illegal: must start with a string list
12391 @subsection String Types
12394 A @emph{string type declaration} introduces a discrete set of string literals.
12395 If a string variable is declared to have this type, its value
12396 is restricted to the given set of literals.
12398 Here is an example of a string type declaration:
12400 @smallexample @c projectfile
12401 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12405 Variables of a string type are called @emph{typed variables}; all other
12406 variables are called @emph{untyped variables}. Typed variables are
12407 particularly useful in @code{case} constructions, to support conditional
12408 attribute declarations.
12409 (@pxref{case Constructions}).
12411 The string literals in the list are case sensitive and must all be different.
12412 They may include any graphic characters allowed in Ada, including spaces.
12414 A string type may only be declared at the project level, not inside a package.
12416 A string type may be referenced by its name if it has been declared in the same
12417 project file, or by an expanded name whose prefix is the name of the project
12418 in which it is declared.
12421 @subsection Variables
12424 A variable may be declared at the project file level, or within a package.
12425 Here are some examples of variable declarations:
12427 @smallexample @c projectfile
12429 This_OS : OS := external ("OS"); -- a typed variable declaration
12430 That_OS := "GNU/Linux"; -- an untyped variable declaration
12435 The syntax of a @emph{typed variable declaration} is identical to the Ada
12436 syntax for an object declaration. By contrast, the syntax of an untyped
12437 variable declaration is identical to an Ada assignment statement. In fact,
12438 variable declarations in project files have some of the characteristics of
12439 an assignment, in that successive declarations for the same variable are
12440 allowed. Untyped variable declarations do establish the expected kind of the
12441 variable (string or string list), and successive declarations for it must
12442 respect the initial kind.
12445 A string variable declaration (typed or untyped) declares a variable
12446 whose value is a string. This variable may be used as a string expression.
12447 @smallexample @c projectfile
12448 File_Name := "readme.txt";
12449 Saved_File_Name := File_Name & ".saved";
12453 A string list variable declaration declares a variable whose value is a list
12454 of strings. The list may contain any number (zero or more) of strings.
12456 @smallexample @c projectfile
12458 List_With_One_Element := ("^-gnaty^-gnaty^");
12459 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12460 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12461 "pack2.ada", "util_.ada", "util.ada");
12465 The same typed variable may not be declared more than once at project level,
12466 and it may not be declared more than once in any package; it is in effect
12469 The same untyped variable may be declared several times. Declarations are
12470 elaborated in the order in which they appear, so the new value replaces
12471 the old one, and any subsequent reference to the variable uses the new value.
12472 However, as noted above, if a variable has been declared as a string, all
12474 declarations must give it a string value. Similarly, if a variable has
12475 been declared as a string list, all subsequent declarations
12476 must give it a string list value.
12478 A @emph{variable reference} may take several forms:
12481 @item The simple variable name, for a variable in the current package (if any)
12482 or in the current project
12483 @item An expanded name, whose prefix is a context name.
12487 A @emph{context} may be one of the following:
12490 @item The name of an existing package in the current project
12491 @item The name of an imported project of the current project
12492 @item The name of an ancestor project (i.e., a project extended by the current
12493 project, either directly or indirectly)
12494 @item An expanded name whose prefix is an imported/parent project name, and
12495 whose selector is a package name in that project.
12499 A variable reference may be used in an expression.
12502 @subsection Attributes
12505 A project (and its packages) may have @emph{attributes} that define
12506 the project's properties. Some attributes have values that are strings;
12507 others have values that are string lists.
12509 There are two categories of attributes: @emph{simple attributes}
12510 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12512 Legal project attribute names, and attribute names for each legal package are
12513 listed below. Attributes names are case-insensitive.
12515 The following attributes are defined on projects (all are simple attributes):
12517 @multitable @columnfractions .4 .3
12518 @item @emph{Attribute Name}
12520 @item @code{Source_Files}
12522 @item @code{Source_Dirs}
12524 @item @code{Source_List_File}
12526 @item @code{Object_Dir}
12528 @item @code{Exec_Dir}
12530 @item @code{Excluded_Source_Dirs}
12532 @item @code{Excluded_Source_Files}
12534 @item @code{Excluded_Source_List_File}
12536 @item @code{Languages}
12540 @item @code{Library_Dir}
12542 @item @code{Library_Name}
12544 @item @code{Library_Kind}
12546 @item @code{Library_Version}
12548 @item @code{Library_Interface}
12550 @item @code{Library_Auto_Init}
12552 @item @code{Library_Options}
12554 @item @code{Library_Src_Dir}
12556 @item @code{Library_ALI_Dir}
12558 @item @code{Library_GCC}
12560 @item @code{Library_Symbol_File}
12562 @item @code{Library_Symbol_Policy}
12564 @item @code{Library_Reference_Symbol_File}
12566 @item @code{Externally_Built}
12571 The following attributes are defined for package @code{Naming}
12572 (@pxref{Naming Schemes}):
12574 @multitable @columnfractions .4 .2 .2 .2
12575 @item Attribute Name @tab Category @tab Index @tab Value
12576 @item @code{Spec_Suffix}
12577 @tab associative array
12580 @item @code{Body_Suffix}
12581 @tab associative array
12584 @item @code{Separate_Suffix}
12585 @tab simple attribute
12588 @item @code{Casing}
12589 @tab simple attribute
12592 @item @code{Dot_Replacement}
12593 @tab simple attribute
12597 @tab associative array
12601 @tab associative array
12604 @item @code{Specification_Exceptions}
12605 @tab associative array
12608 @item @code{Implementation_Exceptions}
12609 @tab associative array
12615 The following attributes are defined for packages @code{Builder},
12616 @code{Compiler}, @code{Binder},
12617 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
12618 (@pxref{^Switches^Switches^ and Project Files}).
12620 @multitable @columnfractions .4 .2 .2 .2
12621 @item Attribute Name @tab Category @tab Index @tab Value
12622 @item @code{^Default_Switches^Default_Switches^}
12623 @tab associative array
12626 @item @code{^Switches^Switches^}
12627 @tab associative array
12633 In addition, package @code{Compiler} has a single string attribute
12634 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
12635 string attribute @code{Global_Configuration_Pragmas}.
12638 Each simple attribute has a default value: the empty string (for string-valued
12639 attributes) and the empty list (for string list-valued attributes).
12641 An attribute declaration defines a new value for an attribute.
12643 Examples of simple attribute declarations:
12645 @smallexample @c projectfile
12646 for Object_Dir use "objects";
12647 for Source_Dirs use ("units", "test/drivers");
12651 The syntax of a @dfn{simple attribute declaration} is similar to that of an
12652 attribute definition clause in Ada.
12654 Attributes references may be appear in expressions.
12655 The general form for such a reference is @code{<entity>'<attribute>}:
12656 Associative array attributes are functions. Associative
12657 array attribute references must have an argument that is a string literal.
12661 @smallexample @c projectfile
12663 Naming'Dot_Replacement
12664 Imported_Project'Source_Dirs
12665 Imported_Project.Naming'Casing
12666 Builder'^Default_Switches^Default_Switches^("Ada")
12670 The prefix of an attribute may be:
12672 @item @code{project} for an attribute of the current project
12673 @item The name of an existing package of the current project
12674 @item The name of an imported project
12675 @item The name of a parent project that is extended by the current project
12676 @item An expanded name whose prefix is imported/parent project name,
12677 and whose selector is a package name
12682 @smallexample @c projectfile
12685 for Source_Dirs use project'Source_Dirs & "units";
12686 for Source_Dirs use project'Source_Dirs & "test/drivers"
12692 In the first attribute declaration, initially the attribute @code{Source_Dirs}
12693 has the default value: an empty string list. After this declaration,
12694 @code{Source_Dirs} is a string list of one element: @code{"units"}.
12695 After the second attribute declaration @code{Source_Dirs} is a string list of
12696 two elements: @code{"units"} and @code{"test/drivers"}.
12698 Note: this example is for illustration only. In practice,
12699 the project file would contain only one attribute declaration:
12701 @smallexample @c projectfile
12702 for Source_Dirs use ("units", "test/drivers");
12705 @node Associative Array Attributes
12706 @subsection Associative Array Attributes
12709 Some attributes are defined as @emph{associative arrays}. An associative
12710 array may be regarded as a function that takes a string as a parameter
12711 and delivers a string or string list value as its result.
12713 Here are some examples of single associative array attribute associations:
12715 @smallexample @c projectfile
12716 for Body ("main") use "Main.ada";
12717 for ^Switches^Switches^ ("main.ada")
12719 "^-gnatv^-gnatv^");
12720 for ^Switches^Switches^ ("main.ada")
12721 use Builder'^Switches^Switches^ ("main.ada")
12726 Like untyped variables and simple attributes, associative array attributes
12727 may be declared several times. Each declaration supplies a new value for the
12728 attribute, and replaces the previous setting.
12731 An associative array attribute may be declared as a full associative array
12732 declaration, with the value of the same attribute in an imported or extended
12735 @smallexample @c projectfile
12737 for Default_Switches use Default.Builder'Default_Switches;
12742 In this example, @code{Default} must be either a project imported by the
12743 current project, or the project that the current project extends. If the
12744 attribute is in a package (in this case, in package @code{Builder}), the same
12745 package needs to be specified.
12748 A full associative array declaration replaces any other declaration for the
12749 attribute, including other full associative array declaration. Single
12750 associative array associations may be declare after a full associative
12751 declaration, modifying the value for a single association of the attribute.
12753 @node case Constructions
12754 @subsection @code{case} Constructions
12757 A @code{case} construction is used in a project file to effect conditional
12759 Here is a typical example:
12761 @smallexample @c projectfile
12764 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
12766 OS : OS_Type := external ("OS", "GNU/Linux");
12770 package Compiler is
12772 when "GNU/Linux" | "Unix" =>
12773 for ^Default_Switches^Default_Switches^ ("Ada")
12774 use ("^-gnath^-gnath^");
12776 for ^Default_Switches^Default_Switches^ ("Ada")
12777 use ("^-gnatP^-gnatP^");
12786 The syntax of a @code{case} construction is based on the Ada case statement
12787 (although there is no @code{null} construction for empty alternatives).
12789 The case expression must be a typed string variable.
12790 Each alternative comprises the reserved word @code{when}, either a list of
12791 literal strings separated by the @code{"|"} character or the reserved word
12792 @code{others}, and the @code{"=>"} token.
12793 Each literal string must belong to the string type that is the type of the
12795 An @code{others} alternative, if present, must occur last.
12797 After each @code{=>}, there are zero or more constructions. The only
12798 constructions allowed in a case construction are other case constructions,
12799 attribute declarations and variable declarations. String type declarations and
12800 package declarations are not allowed. Variable declarations are restricted to
12801 variables that have already been declared before the case construction.
12803 The value of the case variable is often given by an external reference
12804 (@pxref{External References in Project Files}).
12806 @c ****************************************
12807 @c * Objects and Sources in Project Files *
12808 @c ****************************************
12810 @node Objects and Sources in Project Files
12811 @section Objects and Sources in Project Files
12814 * Object Directory::
12816 * Source Directories::
12817 * Source File Names::
12821 Each project has exactly one object directory and one or more source
12822 directories. The source directories must contain at least one source file,
12823 unless the project file explicitly specifies that no source files are present
12824 (@pxref{Source File Names}).
12826 @node Object Directory
12827 @subsection Object Directory
12830 The object directory for a project is the directory containing the compiler's
12831 output (such as @file{ALI} files and object files) for the project's immediate
12834 The object directory is given by the value of the attribute @code{Object_Dir}
12835 in the project file.
12837 @smallexample @c projectfile
12838 for Object_Dir use "objects";
12842 The attribute @code{Object_Dir} has a string value, the path name of the object
12843 directory. The path name may be absolute or relative to the directory of the
12844 project file. This directory must already exist, and be readable and writable.
12846 By default, when the attribute @code{Object_Dir} is not given an explicit value
12847 or when its value is the empty string, the object directory is the same as the
12848 directory containing the project file.
12850 @node Exec Directory
12851 @subsection Exec Directory
12854 The exec directory for a project is the directory containing the executables
12855 for the project's main subprograms.
12857 The exec directory is given by the value of the attribute @code{Exec_Dir}
12858 in the project file.
12860 @smallexample @c projectfile
12861 for Exec_Dir use "executables";
12865 The attribute @code{Exec_Dir} has a string value, the path name of the exec
12866 directory. The path name may be absolute or relative to the directory of the
12867 project file. This directory must already exist, and be writable.
12869 By default, when the attribute @code{Exec_Dir} is not given an explicit value
12870 or when its value is the empty string, the exec directory is the same as the
12871 object directory of the project file.
12873 @node Source Directories
12874 @subsection Source Directories
12877 The source directories of a project are specified by the project file
12878 attribute @code{Source_Dirs}.
12880 This attribute's value is a string list. If the attribute is not given an
12881 explicit value, then there is only one source directory, the one where the
12882 project file resides.
12884 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
12887 @smallexample @c projectfile
12888 for Source_Dirs use ();
12892 indicates that the project contains no source files.
12894 Otherwise, each string in the string list designates one or more
12895 source directories.
12897 @smallexample @c projectfile
12898 for Source_Dirs use ("sources", "test/drivers");
12902 If a string in the list ends with @code{"/**"}, then the directory whose path
12903 name precedes the two asterisks, as well as all its subdirectories
12904 (recursively), are source directories.
12906 @smallexample @c projectfile
12907 for Source_Dirs use ("/system/sources/**");
12911 Here the directory @code{/system/sources} and all of its subdirectories
12912 (recursively) are source directories.
12914 To specify that the source directories are the directory of the project file
12915 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
12916 @smallexample @c projectfile
12917 for Source_Dirs use ("./**");
12921 Each of the source directories must exist and be readable.
12923 @node Source File Names
12924 @subsection Source File Names
12927 In a project that contains source files, their names may be specified by the
12928 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
12929 (a string). Source file names never include any directory information.
12931 If the attribute @code{Source_Files} is given an explicit value, then each
12932 element of the list is a source file name.
12934 @smallexample @c projectfile
12935 for Source_Files use ("main.adb");
12936 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
12940 If the attribute @code{Source_Files} is not given an explicit value,
12941 but the attribute @code{Source_List_File} is given a string value,
12942 then the source file names are contained in the text file whose path name
12943 (absolute or relative to the directory of the project file) is the
12944 value of the attribute @code{Source_List_File}.
12946 Each line in the file that is not empty or is not a comment
12947 contains a source file name.
12949 @smallexample @c projectfile
12950 for Source_List_File use "source_list.txt";
12954 By default, if neither the attribute @code{Source_Files} nor the attribute
12955 @code{Source_List_File} is given an explicit value, then each file in the
12956 source directories that conforms to the project's naming scheme
12957 (@pxref{Naming Schemes}) is an immediate source of the project.
12959 A warning is issued if both attributes @code{Source_Files} and
12960 @code{Source_List_File} are given explicit values. In this case, the attribute
12961 @code{Source_Files} prevails.
12963 Each source file name must be the name of one existing source file
12964 in one of the source directories.
12966 A @code{Source_Files} attribute whose value is an empty list
12967 indicates that there are no source files in the project.
12969 If the order of the source directories is known statically, that is if
12970 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
12971 be several files with the same source file name. In this case, only the file
12972 in the first directory is considered as an immediate source of the project
12973 file. If the order of the source directories is not known statically, it is
12974 an error to have several files with the same source file name.
12976 Projects can be specified to have no Ada source
12977 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
12978 list, or the @code{"Ada"} may be absent from @code{Languages}:
12980 @smallexample @c projectfile
12981 for Source_Dirs use ();
12982 for Source_Files use ();
12983 for Languages use ("C", "C++");
12987 Otherwise, a project must contain at least one immediate source.
12989 Projects with no source files are useful as template packages
12990 (@pxref{Packages in Project Files}) for other projects; in particular to
12991 define a package @code{Naming} (@pxref{Naming Schemes}).
12993 @c ****************************
12994 @c * Importing Projects *
12995 @c ****************************
12997 @node Importing Projects
12998 @section Importing Projects
12999 @cindex @code{ADA_PROJECT_PATH}
13002 An immediate source of a project P may depend on source files that
13003 are neither immediate sources of P nor in the predefined library.
13004 To get this effect, P must @emph{import} the projects that contain the needed
13007 @smallexample @c projectfile
13009 with "project1", "utilities.gpr";
13010 with "/namings/apex.gpr";
13017 As can be seen in this example, the syntax for importing projects is similar
13018 to the syntax for importing compilation units in Ada. However, project files
13019 use literal strings instead of names, and the @code{with} clause identifies
13020 project files rather than packages.
13022 Each literal string is the file name or path name (absolute or relative) of a
13023 project file. If a string corresponds to a file name, with no path or a
13024 relative path, then its location is determined by the @emph{project path}. The
13025 latter can be queried using @code{gnatls -v}. It contains:
13029 In first position, the directory containing the current project file.
13031 In last position, the default project directory. This default project directory
13032 is part of the GNAT installation and is the standard place to install project
13033 files giving access to standard support libraries.
13035 @ref{Installing a library}
13039 In between, all the directories referenced in the
13040 ^environment variable^logical name^ @env{ADA_PROJECT_PATH} if it exists.
13044 If a relative pathname is used, as in
13046 @smallexample @c projectfile
13051 then the full path for the project is constructed by concatenating this
13052 relative path to those in the project path, in order, until a matching file is
13053 found. Any symbolic link will be fully resolved in the directory of the
13054 importing project file before the imported project file is examined.
13056 If the @code{with}'ed project file name does not have an extension,
13057 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13058 then the file name as specified in the @code{with} clause (no extension) will
13059 be used. In the above example, if a file @code{project1.gpr} is found, then it
13060 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13061 then it will be used; if neither file exists, this is an error.
13063 A warning is issued if the name of the project file does not match the
13064 name of the project; this check is case insensitive.
13066 Any source file that is an immediate source of the imported project can be
13067 used by the immediate sources of the importing project, transitively. Thus
13068 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13069 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13070 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13071 because if and when @code{B} ceases to import @code{C}, some sources in
13072 @code{A} will no longer compile.
13074 A side effect of this capability is that normally cyclic dependencies are not
13075 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13076 is not allowed to import @code{A}. However, there are cases when cyclic
13077 dependencies would be beneficial. For these cases, another form of import
13078 between projects exists, the @code{limited with}: a project @code{A} that
13079 imports a project @code{B} with a straight @code{with} may also be imported,
13080 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13081 to @code{A} include at least one @code{limited with}.
13083 @smallexample @c 0projectfile
13089 limited with "../a/a.gpr";
13097 limited with "../a/a.gpr";
13103 In the above legal example, there are two project cycles:
13106 @item A -> C -> D -> A
13110 In each of these cycle there is one @code{limited with}: import of @code{A}
13111 from @code{B} and import of @code{A} from @code{D}.
13113 The difference between straight @code{with} and @code{limited with} is that
13114 the name of a project imported with a @code{limited with} cannot be used in the
13115 project that imports it. In particular, its packages cannot be renamed and
13116 its variables cannot be referred to.
13118 An exception to the above rules for @code{limited with} is that for the main
13119 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13120 @code{limited with} is equivalent to a straight @code{with}. For example,
13121 in the example above, projects @code{B} and @code{D} could not be main
13122 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13123 each have a @code{limited with} that is the only one in a cycle of importing
13126 @c *********************
13127 @c * Project Extension *
13128 @c *********************
13130 @node Project Extension
13131 @section Project Extension
13134 During development of a large system, it is sometimes necessary to use
13135 modified versions of some of the source files, without changing the original
13136 sources. This can be achieved through the @emph{project extension} facility.
13138 @smallexample @c projectfile
13139 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13143 A project extension declaration introduces an extending project
13144 (the @emph{child}) and a project being extended (the @emph{parent}).
13146 By default, a child project inherits all the sources of its parent.
13147 However, inherited sources can be overridden: a unit in a parent is hidden
13148 by a unit of the same name in the child.
13150 Inherited sources are considered to be sources (but not immediate sources)
13151 of the child project; see @ref{Project File Syntax}.
13153 An inherited source file retains any switches specified in the parent project.
13155 For example if the project @code{Utilities} contains the spec and the
13156 body of an Ada package @code{Util_IO}, then the project
13157 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13158 The original body of @code{Util_IO} will not be considered in program builds.
13159 However, the package spec will still be found in the project
13162 A child project can have only one parent, except when it is qualified as
13163 abstract. But it may import any number of other projects.
13165 A project is not allowed to import directly or indirectly at the same time a
13166 child project and any of its ancestors.
13168 @c *******************************
13169 @c * Project Hierarchy Extension *
13170 @c *******************************
13172 @node Project Hierarchy Extension
13173 @section Project Hierarchy Extension
13176 When extending a large system spanning multiple projects, it is often
13177 inconvenient to extend every project in the hierarchy that is impacted by a
13178 small change introduced. In such cases, it is possible to create a virtual
13179 extension of entire hierarchy using @code{extends all} relationship.
13181 When the project is extended using @code{extends all} inheritance, all projects
13182 that are imported by it, both directly and indirectly, are considered virtually
13183 extended. That is, the Project Manager creates "virtual projects"
13184 that extend every project in the hierarchy; all these virtual projects have
13185 no sources of their own and have as object directory the object directory of
13186 the root of "extending all" project.
13188 It is possible to explicitly extend one or more projects in the hierarchy
13189 in order to modify the sources. These extending projects must be imported by
13190 the "extending all" project, which will replace the corresponding virtual
13191 projects with the explicit ones.
13193 When building such a project hierarchy extension, the Project Manager will
13194 ensure that both modified sources and sources in virtual extending projects
13195 that depend on them, are recompiled.
13197 By means of example, consider the following hierarchy of projects.
13201 project A, containing package P1
13203 project B importing A and containing package P2 which depends on P1
13205 project C importing B and containing package P3 which depends on P2
13209 We want to modify packages P1 and P3.
13211 This project hierarchy will need to be extended as follows:
13215 Create project A1 that extends A, placing modified P1 there:
13217 @smallexample @c 0projectfile
13218 project A1 extends "(@dots{})/A" is
13223 Create project C1 that "extends all" C and imports A1, placing modified
13226 @smallexample @c 0projectfile
13227 with "(@dots{})/A1";
13228 project C1 extends all "(@dots{})/C" is
13233 When you build project C1, your entire modified project space will be
13234 recompiled, including the virtual project B1 that has been impacted by the
13235 "extending all" inheritance of project C.
13237 Note that if a Library Project in the hierarchy is virtually extended,
13238 the virtual project that extends the Library Project is not a Library Project.
13240 @c ****************************************
13241 @c * External References in Project Files *
13242 @c ****************************************
13244 @node External References in Project Files
13245 @section External References in Project Files
13248 A project file may contain references to external variables; such references
13249 are called @emph{external references}.
13251 An external variable is either defined as part of the environment (an
13252 environment variable in Unix, for example) or else specified on the command
13253 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13254 If both, then the command line value is used.
13256 The value of an external reference is obtained by means of the built-in
13257 function @code{external}, which returns a string value.
13258 This function has two forms:
13260 @item @code{external (external_variable_name)}
13261 @item @code{external (external_variable_name, default_value)}
13265 Each parameter must be a string literal. For example:
13267 @smallexample @c projectfile
13269 external ("OS", "GNU/Linux")
13273 In the form with one parameter, the function returns the value of
13274 the external variable given as parameter. If this name is not present in the
13275 environment, the function returns an empty string.
13277 In the form with two string parameters, the second argument is
13278 the value returned when the variable given as the first argument is not
13279 present in the environment. In the example above, if @code{"OS"} is not
13280 the name of ^an environment variable^a logical name^ and is not passed on
13281 the command line, then the returned value is @code{"GNU/Linux"}.
13283 An external reference may be part of a string expression or of a string
13284 list expression, and can therefore appear in a variable declaration or
13285 an attribute declaration.
13287 @smallexample @c projectfile
13289 type Mode_Type is ("Debug", "Release");
13290 Mode : Mode_Type := external ("MODE");
13297 @c *****************************
13298 @c * Packages in Project Files *
13299 @c *****************************
13301 @node Packages in Project Files
13302 @section Packages in Project Files
13305 A @emph{package} defines the settings for project-aware tools within a
13307 For each such tool one can declare a package; the names for these
13308 packages are preset (@pxref{Packages}).
13309 A package may contain variable declarations, attribute declarations, and case
13312 @smallexample @c projectfile
13315 package Builder is -- used by gnatmake
13316 for ^Default_Switches^Default_Switches^ ("Ada")
13325 The syntax of package declarations mimics that of package in Ada.
13327 Most of the packages have an attribute
13328 @code{^Default_Switches^Default_Switches^}.
13329 This attribute is an associative array, and its value is a string list.
13330 The index of the associative array is the name of a programming language (case
13331 insensitive). This attribute indicates the ^switch^switch^
13332 or ^switches^switches^ to be used
13333 with the corresponding tool.
13335 Some packages also have another attribute, @code{^Switches^Switches^},
13336 an associative array whose value is a string list.
13337 The index is the name of a source file.
13338 This attribute indicates the ^switch^switch^
13339 or ^switches^switches^ to be used by the corresponding
13340 tool when dealing with this specific file.
13342 Further information on these ^switch^switch^-related attributes is found in
13343 @ref{^Switches^Switches^ and Project Files}.
13345 A package may be declared as a @emph{renaming} of another package; e.g., from
13346 the project file for an imported project.
13348 @smallexample @c projectfile
13350 with "/global/apex.gpr";
13352 package Naming renames Apex.Naming;
13359 Packages that are renamed in other project files often come from project files
13360 that have no sources: they are just used as templates. Any modification in the
13361 template will be reflected automatically in all the project files that rename
13362 a package from the template.
13364 In addition to the tool-oriented packages, you can also declare a package
13365 named @code{Naming} to establish specialized source file naming conventions
13366 (@pxref{Naming Schemes}).
13368 @c ************************************
13369 @c * Variables from Imported Projects *
13370 @c ************************************
13372 @node Variables from Imported Projects
13373 @section Variables from Imported Projects
13376 An attribute or variable defined in an imported or parent project can
13377 be used in expressions in the importing / extending project.
13378 Such an attribute or variable is denoted by an expanded name whose prefix
13379 is either the name of the project or the expanded name of a package within
13382 @smallexample @c projectfile
13385 project Main extends "base" is
13386 Var1 := Imported.Var;
13387 Var2 := Base.Var & ".new";
13392 for ^Default_Switches^Default_Switches^ ("Ada")
13393 use Imported.Builder'Ada_^Switches^Switches^ &
13394 "^-gnatg^-gnatg^" &
13400 package Compiler is
13401 for ^Default_Switches^Default_Switches^ ("Ada")
13402 use Base.Compiler'Ada_^Switches^Switches^;
13413 The value of @code{Var1} is a copy of the variable @code{Var} defined
13414 in the project file @file{"imported.gpr"}
13416 the value of @code{Var2} is a copy of the value of variable @code{Var}
13417 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13419 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13420 @code{Builder} is a string list that includes in its value a copy of the value
13421 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13422 in project file @file{imported.gpr} plus two new elements:
13423 @option{"^-gnatg^-gnatg^"}
13424 and @option{"^-v^-v^"};
13426 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13427 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13428 defined in the @code{Compiler} package in project file @file{base.gpr},
13429 the project being extended.
13432 @c ******************
13433 @c * Naming Schemes *
13434 @c ******************
13436 @node Naming Schemes
13437 @section Naming Schemes
13440 Sometimes an Ada software system is ported from a foreign compilation
13441 environment to GNAT, and the file names do not use the default GNAT
13442 conventions. Instead of changing all the file names (which for a variety
13443 of reasons might not be possible), you can define the relevant file
13444 naming scheme in the @code{Naming} package in your project file.
13447 Note that the use of pragmas described in
13448 @ref{Alternative File Naming Schemes} by mean of a configuration
13449 pragmas file is not supported when using project files. You must use
13450 the features described in this paragraph. You can however use specify
13451 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13454 For example, the following
13455 package models the Apex file naming rules:
13457 @smallexample @c projectfile
13460 for Casing use "lowercase";
13461 for Dot_Replacement use ".";
13462 for Spec_Suffix ("Ada") use ".1.ada";
13463 for Body_Suffix ("Ada") use ".2.ada";
13470 For example, the following package models the HP Ada file naming rules:
13472 @smallexample @c projectfile
13475 for Casing use "lowercase";
13476 for Dot_Replacement use "__";
13477 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13478 for Body_Suffix ("Ada") use ".^ada^ada^";
13484 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13485 names in lower case)
13489 You can define the following attributes in package @code{Naming}:
13493 @item @code{Casing}
13494 This must be a string with one of the three values @code{"lowercase"},
13495 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13498 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13500 @item @code{Dot_Replacement}
13501 This must be a string whose value satisfies the following conditions:
13504 @item It must not be empty
13505 @item It cannot start or end with an alphanumeric character
13506 @item It cannot be a single underscore
13507 @item It cannot start with an underscore followed by an alphanumeric
13508 @item It cannot contain a dot @code{'.'} except if the entire string
13513 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13515 @item @code{Spec_Suffix}
13516 This is an associative array (indexed by the programming language name, case
13517 insensitive) whose value is a string that must satisfy the following
13521 @item It must not be empty
13522 @item It must include at least one dot
13525 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13526 @code{"^.ads^.ADS^"}.
13528 @item @code{Body_Suffix}
13529 This is an associative array (indexed by the programming language name, case
13530 insensitive) whose value is a string that must satisfy the following
13534 @item It must not be empty
13535 @item It must include at least one dot
13536 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13539 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13540 same string, then a file name that ends with the longest of these two suffixes
13541 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13542 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13544 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13545 @code{"^.adb^.ADB^"}.
13547 @item @code{Separate_Suffix}
13548 This must be a string whose value satisfies the same conditions as
13549 @code{Body_Suffix}. The same "longest suffix" rules apply.
13552 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13553 value as @code{Body_Suffix ("Ada")}.
13557 You can use the associative array attribute @code{Spec} to define
13558 the source file name for an individual Ada compilation unit's spec. The array
13559 index must be a string literal that identifies the Ada unit (case insensitive).
13560 The value of this attribute must be a string that identifies the file that
13561 contains this unit's spec (case sensitive or insensitive depending on the
13564 @smallexample @c projectfile
13565 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13570 You can use the associative array attribute @code{Body} to
13571 define the source file name for an individual Ada compilation unit's body
13572 (possibly a subunit). The array index must be a string literal that identifies
13573 the Ada unit (case insensitive). The value of this attribute must be a string
13574 that identifies the file that contains this unit's body or subunit (case
13575 sensitive or insensitive depending on the operating system).
13577 @smallexample @c projectfile
13578 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13582 @c ********************
13583 @c * Library Projects *
13584 @c ********************
13586 @node Library Projects
13587 @section Library Projects
13590 @emph{Library projects} are projects whose object code is placed in a library.
13591 (Note that this facility is not yet supported on all platforms)
13593 To create a library project, you need to define in its project file
13594 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
13595 Additionally, you may define other library-related attributes such as
13596 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
13597 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
13599 The @code{Library_Name} attribute has a string value. There is no restriction
13600 on the name of a library. It is the responsibility of the developer to
13601 choose a name that will be accepted by the platform. It is recommended to
13602 choose names that could be Ada identifiers; such names are almost guaranteed
13603 to be acceptable on all platforms.
13605 The @code{Library_Dir} attribute has a string value that designates the path
13606 (absolute or relative) of the directory where the library will reside.
13607 It must designate an existing directory, and this directory must be writable,
13608 different from the project's object directory and from any source directory
13609 in the project tree.
13611 If both @code{Library_Name} and @code{Library_Dir} are specified and
13612 are legal, then the project file defines a library project. The optional
13613 library-related attributes are checked only for such project files.
13615 The @code{Library_Kind} attribute has a string value that must be one of the
13616 following (case insensitive): @code{"static"}, @code{"dynamic"} or
13617 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
13618 attribute is not specified, the library is a static library, that is
13619 an archive of object files that can be potentially linked into a
13620 static executable. Otherwise, the library may be dynamic or
13621 relocatable, that is a library that is loaded only at the start of execution.
13623 If you need to build both a static and a dynamic library, you should use two
13624 different object directories, since in some cases some extra code needs to
13625 be generated for the latter. For such cases, it is recommended to either use
13626 two different project files, or a single one which uses external variables
13627 to indicate what kind of library should be build.
13629 The @code{Library_ALI_Dir} attribute may be specified to indicate the
13630 directory where the ALI files of the library will be copied. When it is
13631 not specified, the ALI files are copied to the directory specified in
13632 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
13633 must be writable and different from the project's object directory and from
13634 any source directory in the project tree.
13636 The @code{Library_Version} attribute has a string value whose interpretation
13637 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
13638 used only for dynamic/relocatable libraries as the internal name of the
13639 library (the @code{"soname"}). If the library file name (built from the
13640 @code{Library_Name}) is different from the @code{Library_Version}, then the
13641 library file will be a symbolic link to the actual file whose name will be
13642 @code{Library_Version}.
13646 @smallexample @c projectfile
13652 for Library_Dir use "lib_dir";
13653 for Library_Name use "dummy";
13654 for Library_Kind use "relocatable";
13655 for Library_Version use "libdummy.so." & Version;
13662 Directory @file{lib_dir} will contain the internal library file whose name
13663 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
13664 @file{libdummy.so.1}.
13666 When @command{gnatmake} detects that a project file
13667 is a library project file, it will check all immediate sources of the project
13668 and rebuild the library if any of the sources have been recompiled.
13670 Standard project files can import library project files. In such cases,
13671 the libraries will only be rebuilt if some of its sources are recompiled
13672 because they are in the closure of some other source in an importing project.
13673 Sources of the library project files that are not in such a closure will
13674 not be checked, unless the full library is checked, because one of its sources
13675 needs to be recompiled.
13677 For instance, assume the project file @code{A} imports the library project file
13678 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
13679 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
13680 @file{l2.ads}, @file{l2.adb}.
13682 If @file{l1.adb} has been modified, then the library associated with @code{L}
13683 will be rebuilt when compiling all the immediate sources of @code{A} only
13684 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
13687 To be sure that all the sources in the library associated with @code{L} are
13688 up to date, and that all the sources of project @code{A} are also up to date,
13689 the following two commands needs to be used:
13696 When a library is built or rebuilt, an attempt is made first to delete all
13697 files in the library directory.
13698 All @file{ALI} files will also be copied from the object directory to the
13699 library directory. To build executables, @command{gnatmake} will use the
13700 library rather than the individual object files.
13703 It is also possible to create library project files for third-party libraries
13704 that are precompiled and cannot be compiled locally thanks to the
13705 @code{externally_built} attribute. (See @ref{Installing a library}).
13708 @c *******************************
13709 @c * Stand-alone Library Projects *
13710 @c *******************************
13712 @node Stand-alone Library Projects
13713 @section Stand-alone Library Projects
13716 A Stand-alone Library is a library that contains the necessary code to
13717 elaborate the Ada units that are included in the library. A Stand-alone
13718 Library is suitable to be used in an executable when the main is not
13719 in Ada. However, Stand-alone Libraries may also be used with an Ada main
13722 A Stand-alone Library Project is a Library Project where the library is
13723 a Stand-alone Library.
13725 To be a Stand-alone Library Project, in addition to the two attributes
13726 that make a project a Library Project (@code{Library_Name} and
13727 @code{Library_Dir}, see @ref{Library Projects}), the attribute
13728 @code{Library_Interface} must be defined.
13730 @smallexample @c projectfile
13732 for Library_Dir use "lib_dir";
13733 for Library_Name use "dummy";
13734 for Library_Interface use ("int1", "int1.child");
13738 Attribute @code{Library_Interface} has a nonempty string list value,
13739 each string in the list designating a unit contained in an immediate source
13740 of the project file.
13742 When a Stand-alone Library is built, first the binder is invoked to build
13743 a package whose name depends on the library name
13744 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
13745 This binder-generated package includes initialization and
13746 finalization procedures whose
13747 names depend on the library name (dummyinit and dummyfinal in the example
13748 above). The object corresponding to this package is included in the library.
13750 A dynamic or relocatable Stand-alone Library is automatically initialized
13751 if automatic initialization of Stand-alone Libraries is supported on the
13752 platform and if attribute @code{Library_Auto_Init} is not specified or
13753 is specified with the value "true". A static Stand-alone Library is never
13754 automatically initialized.
13756 Single string attribute @code{Library_Auto_Init} may be specified with only
13757 two possible values: "false" or "true" (case-insensitive). Specifying
13758 "false" for attribute @code{Library_Auto_Init} will prevent automatic
13759 initialization of dynamic or relocatable libraries.
13761 When a non-automatically initialized Stand-alone Library is used
13762 in an executable, its initialization procedure must be called before
13763 any service of the library is used.
13764 When the main subprogram is in Ada, it may mean that the initialization
13765 procedure has to be called during elaboration of another package.
13767 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
13768 (those that are listed in attribute @code{Library_Interface}) are copied to
13769 the Library Directory. As a consequence, only the Interface Units may be
13770 imported from Ada units outside of the library. If other units are imported,
13771 the binding phase will fail.
13773 When a Stand-Alone Library is bound, the switches that are specified in
13774 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
13775 used in the call to @command{gnatbind}.
13777 The string list attribute @code{Library_Options} may be used to specified
13778 additional switches to the call to @command{gcc} to link the library.
13780 The attribute @code{Library_Src_Dir}, may be specified for a
13781 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
13782 single string value. Its value must be the path (absolute or relative to the
13783 project directory) of an existing directory. This directory cannot be the
13784 object directory or one of the source directories, but it can be the same as
13785 the library directory. The sources of the Interface
13786 Units of the library, necessary to an Ada client of the library, will be
13787 copied to the designated directory, called Interface Copy directory.
13788 These sources includes the specs of the Interface Units, but they may also
13789 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
13790 are used, or when there is a generic units in the spec. Before the sources
13791 are copied to the Interface Copy directory, an attempt is made to delete all
13792 files in the Interface Copy directory.
13794 @c *************************************
13795 @c * Switches Related to Project Files *
13796 @c *************************************
13797 @node Switches Related to Project Files
13798 @section Switches Related to Project Files
13801 The following switches are used by GNAT tools that support project files:
13805 @item ^-P^/PROJECT_FILE=^@var{project}
13806 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
13807 Indicates the name of a project file. This project file will be parsed with
13808 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
13809 if any, and using the external references indicated
13810 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
13812 There may zero, one or more spaces between @option{-P} and @var{project}.
13816 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
13819 Since the Project Manager parses the project file only after all the switches
13820 on the command line are checked, the order of the switches
13821 @option{^-P^/PROJECT_FILE^},
13822 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
13823 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
13825 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
13826 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
13827 Indicates that external variable @var{name} has the value @var{value}.
13828 The Project Manager will use this value for occurrences of
13829 @code{external(name)} when parsing the project file.
13833 If @var{name} or @var{value} includes a space, then @var{name=value} should be
13834 put between quotes.
13842 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
13843 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
13844 @var{name}, only the last one is used.
13847 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
13848 takes precedence over the value of the same name in the environment.
13850 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
13851 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
13852 Indicates the verbosity of the parsing of GNAT project files.
13855 @option{-vP0} means Default;
13856 @option{-vP1} means Medium;
13857 @option{-vP2} means High.
13861 There are three possible options for this qualifier: DEFAULT, MEDIUM and
13866 The default is ^Default^DEFAULT^: no output for syntactically correct
13869 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
13870 only the last one is used.
13872 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
13873 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
13874 Add directory <dir> at the beginning of the project search path, in order,
13875 after the current working directory.
13879 @cindex @option{-eL} (any project-aware tool)
13880 Follow all symbolic links when processing project files.
13883 @item ^--subdirs^/SUBDIRS^=<subdir>
13884 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
13885 This switch is recognized by gnatmake and gnatclean. It indicate that the real
13886 directories (except the source directories) are the subdirectories <subdir>
13887 of the directories specified in the project files. This applies in particular
13888 to object directories, library directories and exec directories. If the
13889 subdirectories do not exist, they are created automatically.
13893 @c **********************************
13894 @c * Tools Supporting Project Files *
13895 @c **********************************
13897 @node Tools Supporting Project Files
13898 @section Tools Supporting Project Files
13901 * gnatmake and Project Files::
13902 * The GNAT Driver and Project Files::
13905 @node gnatmake and Project Files
13906 @subsection gnatmake and Project Files
13909 This section covers several topics related to @command{gnatmake} and
13910 project files: defining ^switches^switches^ for @command{gnatmake}
13911 and for the tools that it invokes; specifying configuration pragmas;
13912 the use of the @code{Main} attribute; building and rebuilding library project
13916 * ^Switches^Switches^ and Project Files::
13917 * Specifying Configuration Pragmas::
13918 * Project Files and Main Subprograms::
13919 * Library Project Files::
13922 @node ^Switches^Switches^ and Project Files
13923 @subsubsection ^Switches^Switches^ and Project Files
13926 It is not currently possible to specify VMS style qualifiers in the project
13927 files; only Unix style ^switches^switches^ may be specified.
13931 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
13932 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
13933 attribute, a @code{^Switches^Switches^} attribute, or both;
13934 as their names imply, these ^switch^switch^-related
13935 attributes affect the ^switches^switches^ that are used for each of these GNAT
13937 @command{gnatmake} is invoked. As will be explained below, these
13938 component-specific ^switches^switches^ precede
13939 the ^switches^switches^ provided on the @command{gnatmake} command line.
13941 The @code{^Default_Switches^Default_Switches^} attribute is an associative
13942 array indexed by language name (case insensitive) whose value is a string list.
13945 @smallexample @c projectfile
13947 package Compiler is
13948 for ^Default_Switches^Default_Switches^ ("Ada")
13949 use ("^-gnaty^-gnaty^",
13956 The @code{^Switches^Switches^} attribute is also an associative array,
13957 indexed by a file name (which may or may not be case sensitive, depending
13958 on the operating system) whose value is a string list. For example:
13960 @smallexample @c projectfile
13963 for ^Switches^Switches^ ("main1.adb")
13965 for ^Switches^Switches^ ("main2.adb")
13972 For the @code{Builder} package, the file names must designate source files
13973 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
13974 file names must designate @file{ALI} or source files for main subprograms.
13975 In each case just the file name without an explicit extension is acceptable.
13977 For each tool used in a program build (@command{gnatmake}, the compiler, the
13978 binder, and the linker), the corresponding package @dfn{contributes} a set of
13979 ^switches^switches^ for each file on which the tool is invoked, based on the
13980 ^switch^switch^-related attributes defined in the package.
13981 In particular, the ^switches^switches^
13982 that each of these packages contributes for a given file @var{f} comprise:
13986 the value of attribute @code{^Switches^Switches^ (@var{f})},
13987 if it is specified in the package for the given file,
13989 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
13990 if it is specified in the package.
13994 If neither of these attributes is defined in the package, then the package does
13995 not contribute any ^switches^switches^ for the given file.
13997 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
13998 two sets, in the following order: those contributed for the file
13999 by the @code{Builder} package;
14000 and the switches passed on the command line.
14002 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14003 the ^switches^switches^ passed to the tool comprise three sets,
14004 in the following order:
14008 the applicable ^switches^switches^ contributed for the file
14009 by the @code{Builder} package in the project file supplied on the command line;
14012 those contributed for the file by the package (in the relevant project file --
14013 see below) corresponding to the tool; and
14016 the applicable switches passed on the command line.
14020 The term @emph{applicable ^switches^switches^} reflects the fact that
14021 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14022 tools, depending on the individual ^switch^switch^.
14024 @command{gnatmake} may invoke the compiler on source files from different
14025 projects. The Project Manager will use the appropriate project file to
14026 determine the @code{Compiler} package for each source file being compiled.
14027 Likewise for the @code{Binder} and @code{Linker} packages.
14029 As an example, consider the following package in a project file:
14031 @smallexample @c projectfile
14034 package Compiler is
14035 for ^Default_Switches^Default_Switches^ ("Ada")
14037 for ^Switches^Switches^ ("a.adb")
14039 for ^Switches^Switches^ ("b.adb")
14041 "^-gnaty^-gnaty^");
14048 If @command{gnatmake} is invoked with this project file, and it needs to
14049 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14050 @file{a.adb} will be compiled with the ^switch^switch^
14051 @option{^-O1^-O1^},
14052 @file{b.adb} with ^switches^switches^
14054 and @option{^-gnaty^-gnaty^},
14055 and @file{c.adb} with @option{^-g^-g^}.
14057 The following example illustrates the ordering of the ^switches^switches^
14058 contributed by different packages:
14060 @smallexample @c projectfile
14064 for ^Switches^Switches^ ("main.adb")
14072 package Compiler is
14073 for ^Switches^Switches^ ("main.adb")
14081 If you issue the command:
14084 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14088 then the compiler will be invoked on @file{main.adb} with the following
14089 sequence of ^switches^switches^
14092 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14095 with the last @option{^-O^-O^}
14096 ^switch^switch^ having precedence over the earlier ones;
14097 several other ^switches^switches^
14098 (such as @option{^-c^-c^}) are added implicitly.
14100 The ^switches^switches^
14102 and @option{^-O1^-O1^} are contributed by package
14103 @code{Builder}, @option{^-O2^-O2^} is contributed
14104 by the package @code{Compiler}
14105 and @option{^-O0^-O0^} comes from the command line.
14107 The @option{^-g^-g^}
14108 ^switch^switch^ will also be passed in the invocation of
14109 @command{Gnatlink.}
14111 A final example illustrates switch contributions from packages in different
14114 @smallexample @c projectfile
14117 for Source_Files use ("pack.ads", "pack.adb");
14118 package Compiler is
14119 for ^Default_Switches^Default_Switches^ ("Ada")
14120 use ("^-gnata^-gnata^");
14128 for Source_Files use ("foo_main.adb", "bar_main.adb");
14130 for ^Switches^Switches^ ("foo_main.adb")
14138 -- Ada source file:
14140 procedure Foo_Main is
14148 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14152 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14153 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14154 @option{^-gnato^-gnato^} (passed on the command line).
14155 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14156 are @option{^-g^-g^} from @code{Proj4.Builder},
14157 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14158 and @option{^-gnato^-gnato^} from the command line.
14161 When using @command{gnatmake} with project files, some ^switches^switches^ or
14162 arguments may be expressed as relative paths. As the working directory where
14163 compilation occurs may change, these relative paths are converted to absolute
14164 paths. For the ^switches^switches^ found in a project file, the relative paths
14165 are relative to the project file directory, for the switches on the command
14166 line, they are relative to the directory where @command{gnatmake} is invoked.
14167 The ^switches^switches^ for which this occurs are:
14173 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14175 ^-o^-o^, object files specified in package @code{Linker} or after
14176 -largs on the command line). The exception to this rule is the ^switch^switch^
14177 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14179 @node Specifying Configuration Pragmas
14180 @subsubsection Specifying Configuration Pragmas
14182 When using @command{gnatmake} with project files, if there exists a file
14183 @file{gnat.adc} that contains configuration pragmas, this file will be
14186 Configuration pragmas can be defined by means of the following attributes in
14187 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14188 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14190 Both these attributes are single string attributes. Their values is the path
14191 name of a file containing configuration pragmas. If a path name is relative,
14192 then it is relative to the project directory of the project file where the
14193 attribute is defined.
14195 When compiling a source, the configuration pragmas used are, in order,
14196 those listed in the file designated by attribute
14197 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14198 project file, if it is specified, and those listed in the file designated by
14199 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14200 the project file of the source, if it exists.
14202 @node Project Files and Main Subprograms
14203 @subsubsection Project Files and Main Subprograms
14206 When using a project file, you can invoke @command{gnatmake}
14207 with one or several main subprograms, by specifying their source files on the
14211 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14215 Each of these needs to be a source file of the same project, except
14216 when the switch ^-u^/UNIQUE^ is used.
14219 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14220 same project, one of the project in the tree rooted at the project specified
14221 on the command line. The package @code{Builder} of this common project, the
14222 "main project" is the one that is considered by @command{gnatmake}.
14225 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14226 imported directly or indirectly by the project specified on the command line.
14227 Note that if such a source file is not part of the project specified on the
14228 command line, the ^switches^switches^ found in package @code{Builder} of the
14229 project specified on the command line, if any, that are transmitted
14230 to the compiler will still be used, not those found in the project file of
14234 When using a project file, you can also invoke @command{gnatmake} without
14235 explicitly specifying any main, and the effect depends on whether you have
14236 defined the @code{Main} attribute. This attribute has a string list value,
14237 where each element in the list is the name of a source file (the file
14238 extension is optional) that contains a unit that can be a main subprogram.
14240 If the @code{Main} attribute is defined in a project file as a non-empty
14241 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14242 line, then invoking @command{gnatmake} with this project file but without any
14243 main on the command line is equivalent to invoking @command{gnatmake} with all
14244 the file names in the @code{Main} attribute on the command line.
14247 @smallexample @c projectfile
14250 for Main use ("main1", "main2", "main3");
14256 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14258 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14260 When the project attribute @code{Main} is not specified, or is specified
14261 as an empty string list, or when the switch @option{-u} is used on the command
14262 line, then invoking @command{gnatmake} with no main on the command line will
14263 result in all immediate sources of the project file being checked, and
14264 potentially recompiled. Depending on the presence of the switch @option{-u},
14265 sources from other project files on which the immediate sources of the main
14266 project file depend are also checked and potentially recompiled. In other
14267 words, the @option{-u} switch is applied to all of the immediate sources of the
14270 When no main is specified on the command line and attribute @code{Main} exists
14271 and includes several mains, or when several mains are specified on the
14272 command line, the default ^switches^switches^ in package @code{Builder} will
14273 be used for all mains, even if there are specific ^switches^switches^
14274 specified for one or several mains.
14276 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14277 the specific ^switches^switches^ for each main, if they are specified.
14279 @node Library Project Files
14280 @subsubsection Library Project Files
14283 When @command{gnatmake} is invoked with a main project file that is a library
14284 project file, it is not allowed to specify one or more mains on the command
14288 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14289 ^-l^/ACTION=LINK^ have special meanings.
14292 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14293 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14296 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14297 to @command{gnatmake} that the binder generated file should be compiled
14298 (in the case of a stand-alone library) and that the library should be built.
14302 @node The GNAT Driver and Project Files
14303 @subsection The GNAT Driver and Project Files
14306 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14307 can benefit from project files:
14308 @command{^gnatbind^gnatbind^},
14309 @command{^gnatcheck^gnatcheck^}),
14310 @command{^gnatclean^gnatclean^}),
14311 @command{^gnatelim^gnatelim^},
14312 @command{^gnatfind^gnatfind^},
14313 @command{^gnatlink^gnatlink^},
14314 @command{^gnatls^gnatls^},
14315 @command{^gnatmetric^gnatmetric^},
14316 @command{^gnatpp^gnatpp^},
14317 @command{^gnatstub^gnatstub^},
14318 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14319 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14320 They must be invoked through the @command{gnat} driver.
14322 The @command{gnat} driver is a wrapper that accepts a number of commands and
14323 calls the corresponding tool. It was designed initially for VMS platforms (to
14324 convert VMS qualifiers to Unix-style switches), but it is now available on all
14327 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14328 (case insensitive):
14332 BIND to invoke @command{^gnatbind^gnatbind^}
14334 CHOP to invoke @command{^gnatchop^gnatchop^}
14336 CLEAN to invoke @command{^gnatclean^gnatclean^}
14338 COMP or COMPILE to invoke the compiler
14340 ELIM to invoke @command{^gnatelim^gnatelim^}
14342 FIND to invoke @command{^gnatfind^gnatfind^}
14344 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14346 LINK to invoke @command{^gnatlink^gnatlink^}
14348 LS or LIST to invoke @command{^gnatls^gnatls^}
14350 MAKE to invoke @command{^gnatmake^gnatmake^}
14352 NAME to invoke @command{^gnatname^gnatname^}
14354 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14356 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14358 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14360 STUB to invoke @command{^gnatstub^gnatstub^}
14362 XREF to invoke @command{^gnatxref^gnatxref^}
14366 (note that the compiler is invoked using the command
14367 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14370 On non-VMS platforms, between @command{gnat} and the command, two
14371 special switches may be used:
14375 @command{-v} to display the invocation of the tool.
14377 @command{-dn} to prevent the @command{gnat} driver from removing
14378 the temporary files it has created. These temporary files are
14379 configuration files and temporary file list files.
14383 The command may be followed by switches and arguments for the invoked
14387 gnat bind -C main.ali
14393 Switches may also be put in text files, one switch per line, and the text
14394 files may be specified with their path name preceded by '@@'.
14397 gnat bind @@args.txt main.ali
14401 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14402 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14403 (@option{^-P^/PROJECT_FILE^},
14404 @option{^-X^/EXTERNAL_REFERENCE^} and
14405 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14406 the switches of the invoking tool.
14409 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14410 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14411 the immediate sources of the specified project file.
14414 When GNAT METRIC is used with a project file, but with no source
14415 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14416 with all the immediate sources of the specified project file and with
14417 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14421 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14422 a project file, no source is specified on the command line and
14423 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14424 the underlying tool (^gnatpp^gnatpp^ or
14425 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14426 not only for the immediate sources of the main project.
14428 (-U stands for Universal or Union of the project files of the project tree)
14432 For each of the following commands, there is optionally a corresponding
14433 package in the main project.
14437 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14440 package @code{Check} for command CHECK (invoking
14441 @code{^gnatcheck^gnatcheck^})
14444 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14447 package @code{Cross_Reference} for command XREF (invoking
14448 @code{^gnatxref^gnatxref^})
14451 package @code{Eliminate} for command ELIM (invoking
14452 @code{^gnatelim^gnatelim^})
14455 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14458 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14461 package @code{Gnatstub} for command STUB
14462 (invoking @code{^gnatstub^gnatstub^})
14465 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14468 package @code{Metrics} for command METRIC
14469 (invoking @code{^gnatmetric^gnatmetric^})
14472 package @code{Pretty_Printer} for command PP or PRETTY
14473 (invoking @code{^gnatpp^gnatpp^})
14478 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14479 a simple variable with a string list value. It contains ^switches^switches^
14480 for the invocation of @code{^gnatls^gnatls^}.
14482 @smallexample @c projectfile
14486 for ^Switches^Switches^
14495 All other packages have two attribute @code{^Switches^Switches^} and
14496 @code{^Default_Switches^Default_Switches^}.
14499 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14500 source file name, that has a string list value: the ^switches^switches^ to be
14501 used when the tool corresponding to the package is invoked for the specific
14505 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14506 indexed by the programming language that has a string list value.
14507 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14508 ^switches^switches^ for the invocation of the tool corresponding
14509 to the package, except if a specific @code{^Switches^Switches^} attribute
14510 is specified for the source file.
14512 @smallexample @c projectfile
14516 for Source_Dirs use ("./**");
14519 for ^Switches^Switches^ use
14526 package Compiler is
14527 for ^Default_Switches^Default_Switches^ ("Ada")
14528 use ("^-gnatv^-gnatv^",
14529 "^-gnatwa^-gnatwa^");
14535 for ^Default_Switches^Default_Switches^ ("Ada")
14543 for ^Default_Switches^Default_Switches^ ("Ada")
14545 for ^Switches^Switches^ ("main.adb")
14554 for ^Default_Switches^Default_Switches^ ("Ada")
14561 package Cross_Reference is
14562 for ^Default_Switches^Default_Switches^ ("Ada")
14567 end Cross_Reference;
14573 With the above project file, commands such as
14576 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14577 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14578 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14579 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14580 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
14584 will set up the environment properly and invoke the tool with the switches
14585 found in the package corresponding to the tool:
14586 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
14587 except @code{^Switches^Switches^ ("main.adb")}
14588 for @code{^gnatlink^gnatlink^}.
14589 It is also possible to invoke some of the tools,
14590 @code{^gnatcheck^gnatcheck^}),
14591 @code{^gnatmetric^gnatmetric^}),
14592 and @code{^gnatpp^gnatpp^})
14593 on a set of project units thanks to the combination of the switches
14594 @option{-P}, @option{-U} and possibly the main unit when one is interested
14595 in its closure. For instance,
14599 will compute the metrics for all the immediate units of project
14602 gnat metric -Pproj -U
14604 will compute the metrics for all the units of the closure of projects
14605 rooted at @code{proj}.
14607 gnat metric -Pproj -U main_unit
14609 will compute the metrics for the closure of units rooted at
14610 @code{main_unit}. This last possibility relies implicitly
14611 on @command{gnatbind}'s option @option{-R}.
14613 @c **********************
14614 @node An Extended Example
14615 @section An Extended Example
14618 Suppose that we have two programs, @var{prog1} and @var{prog2},
14619 whose sources are in corresponding directories. We would like
14620 to build them with a single @command{gnatmake} command, and we want to place
14621 their object files into @file{build} subdirectories of the source directories.
14622 Furthermore, we want to have to have two separate subdirectories
14623 in @file{build} -- @file{release} and @file{debug} -- which will contain
14624 the object files compiled with different set of compilation flags.
14626 In other words, we have the following structure:
14643 Here are the project files that we must place in a directory @file{main}
14644 to maintain this structure:
14648 @item We create a @code{Common} project with a package @code{Compiler} that
14649 specifies the compilation ^switches^switches^:
14654 @b{project} Common @b{is}
14656 @b{for} Source_Dirs @b{use} (); -- No source files
14660 @b{type} Build_Type @b{is} ("release", "debug");
14661 Build : Build_Type := External ("BUILD", "debug");
14664 @b{package} Compiler @b{is}
14665 @b{case} Build @b{is}
14666 @b{when} "release" =>
14667 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14668 @b{use} ("^-O2^-O2^");
14669 @b{when} "debug" =>
14670 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14671 @b{use} ("^-g^-g^");
14679 @item We create separate projects for the two programs:
14686 @b{project} Prog1 @b{is}
14688 @b{for} Source_Dirs @b{use} ("prog1");
14689 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
14691 @b{package} Compiler @b{renames} Common.Compiler;
14702 @b{project} Prog2 @b{is}
14704 @b{for} Source_Dirs @b{use} ("prog2");
14705 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
14707 @b{package} Compiler @b{renames} Common.Compiler;
14713 @item We create a wrapping project @code{Main}:
14722 @b{project} Main @b{is}
14724 @b{package} Compiler @b{renames} Common.Compiler;
14730 @item Finally we need to create a dummy procedure that @code{with}s (either
14731 explicitly or implicitly) all the sources of our two programs.
14736 Now we can build the programs using the command
14739 gnatmake ^-P^/PROJECT_FILE=^main dummy
14743 for the Debug mode, or
14747 gnatmake -Pmain -XBUILD=release
14753 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
14758 for the Release mode.
14760 @c ********************************
14761 @c * Project File Complete Syntax *
14762 @c ********************************
14764 @node Project File Complete Syntax
14765 @section Project File Complete Syntax
14769 context_clause project_declaration
14775 @b{with} path_name @{ , path_name @} ;
14780 project_declaration ::=
14781 simple_project_declaration | project_extension
14783 simple_project_declaration ::=
14784 @b{project} <project_>simple_name @b{is}
14785 @{declarative_item@}
14786 @b{end} <project_>simple_name;
14788 project_extension ::=
14789 @b{project} <project_>simple_name @b{extends} path_name @b{is}
14790 @{declarative_item@}
14791 @b{end} <project_>simple_name;
14793 declarative_item ::=
14794 package_declaration |
14795 typed_string_declaration |
14796 other_declarative_item
14798 package_declaration ::=
14799 package_spec | package_renaming
14802 @b{package} package_identifier @b{is}
14803 @{simple_declarative_item@}
14804 @b{end} package_identifier ;
14806 package_identifier ::=
14807 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
14808 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
14809 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
14811 package_renaming ::==
14812 @b{package} package_identifier @b{renames}
14813 <project_>simple_name.package_identifier ;
14815 typed_string_declaration ::=
14816 @b{type} <typed_string_>_simple_name @b{is}
14817 ( string_literal @{, string_literal@} );
14819 other_declarative_item ::=
14820 attribute_declaration |
14821 typed_variable_declaration |
14822 variable_declaration |
14825 attribute_declaration ::=
14826 full_associative_array_declaration |
14827 @b{for} attribute_designator @b{use} expression ;
14829 full_associative_array_declaration ::=
14830 @b{for} <associative_array_attribute_>simple_name @b{use}
14831 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
14833 attribute_designator ::=
14834 <simple_attribute_>simple_name |
14835 <associative_array_attribute_>simple_name ( string_literal )
14837 typed_variable_declaration ::=
14838 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
14840 variable_declaration ::=
14841 <variable_>simple_name := expression;
14851 attribute_reference
14857 ( <string_>expression @{ , <string_>expression @} )
14860 @b{external} ( string_literal [, string_literal] )
14862 attribute_reference ::=
14863 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
14865 attribute_prefix ::=
14867 <project_>simple_name | package_identifier |
14868 <project_>simple_name . package_identifier
14870 case_construction ::=
14871 @b{case} <typed_variable_>name @b{is}
14876 @b{when} discrete_choice_list =>
14877 @{case_construction | attribute_declaration@}
14879 discrete_choice_list ::=
14880 string_literal @{| string_literal@} |
14884 simple_name @{. simple_name@}
14887 identifier (same as Ada)
14891 @node The Cross-Referencing Tools gnatxref and gnatfind
14892 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
14897 The compiler generates cross-referencing information (unless
14898 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
14899 This information indicates where in the source each entity is declared and
14900 referenced. Note that entities in package Standard are not included, but
14901 entities in all other predefined units are included in the output.
14903 Before using any of these two tools, you need to compile successfully your
14904 application, so that GNAT gets a chance to generate the cross-referencing
14907 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
14908 information to provide the user with the capability to easily locate the
14909 declaration and references to an entity. These tools are quite similar,
14910 the difference being that @code{gnatfind} is intended for locating
14911 definitions and/or references to a specified entity or entities, whereas
14912 @code{gnatxref} is oriented to generating a full report of all
14915 To use these tools, you must not compile your application using the
14916 @option{-gnatx} switch on the @command{gnatmake} command line
14917 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
14918 information will not be generated.
14920 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
14921 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
14924 * gnatxref Switches::
14925 * gnatfind Switches::
14926 * Project Files for gnatxref and gnatfind::
14927 * Regular Expressions in gnatfind and gnatxref::
14928 * Examples of gnatxref Usage::
14929 * Examples of gnatfind Usage::
14932 @node gnatxref Switches
14933 @section @code{gnatxref} Switches
14936 The command invocation for @code{gnatxref} is:
14938 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
14947 identifies the source files for which a report is to be generated. The
14948 ``with''ed units will be processed too. You must provide at least one file.
14950 These file names are considered to be regular expressions, so for instance
14951 specifying @file{source*.adb} is the same as giving every file in the current
14952 directory whose name starts with @file{source} and whose extension is
14955 You shouldn't specify any directory name, just base names. @command{gnatxref}
14956 and @command{gnatfind} will be able to locate these files by themselves using
14957 the source path. If you specify directories, no result is produced.
14962 The switches can be:
14966 @cindex @option{--version} @command{gnatxref}
14967 Display Copyright and version, then exit disregarding all other options.
14970 @cindex @option{--help} @command{gnatxref}
14971 If @option{--version} was not used, display usage, then exit disregarding
14974 @item ^-a^/ALL_FILES^
14975 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
14976 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
14977 the read-only files found in the library search path. Otherwise, these files
14978 will be ignored. This option can be used to protect Gnat sources or your own
14979 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
14980 much faster, and their output much smaller. Read-only here refers to access
14981 or permissions status in the file system for the current user.
14984 @cindex @option{-aIDIR} (@command{gnatxref})
14985 When looking for source files also look in directory DIR. The order in which
14986 source file search is undertaken is the same as for @command{gnatmake}.
14989 @cindex @option{-aODIR} (@command{gnatxref})
14990 When searching for library and object files, look in directory
14991 DIR. The order in which library files are searched is the same as for
14992 @command{gnatmake}.
14995 @cindex @option{-nostdinc} (@command{gnatxref})
14996 Do not look for sources in the system default directory.
14999 @cindex @option{-nostdlib} (@command{gnatxref})
15000 Do not look for library files in the system default directory.
15002 @item --RTS=@var{rts-path}
15003 @cindex @option{--RTS} (@command{gnatxref})
15004 Specifies the default location of the runtime library. Same meaning as the
15005 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15007 @item ^-d^/DERIVED_TYPES^
15008 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15009 If this switch is set @code{gnatxref} will output the parent type
15010 reference for each matching derived types.
15012 @item ^-f^/FULL_PATHNAME^
15013 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15014 If this switch is set, the output file names will be preceded by their
15015 directory (if the file was found in the search path). If this switch is
15016 not set, the directory will not be printed.
15018 @item ^-g^/IGNORE_LOCALS^
15019 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15020 If this switch is set, information is output only for library-level
15021 entities, ignoring local entities. The use of this switch may accelerate
15022 @code{gnatfind} and @code{gnatxref}.
15025 @cindex @option{-IDIR} (@command{gnatxref})
15026 Equivalent to @samp{-aODIR -aIDIR}.
15029 @cindex @option{-pFILE} (@command{gnatxref})
15030 Specify a project file to use @xref{Project Files}.
15031 If you need to use the @file{.gpr}
15032 project files, you should use gnatxref through the GNAT driver
15033 (@command{gnat xref -Pproject}).
15035 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15036 project file in the current directory.
15038 If a project file is either specified or found by the tools, then the content
15039 of the source directory and object directory lines are added as if they
15040 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15041 and @samp{^-aO^OBJECT_SEARCH^}.
15043 Output only unused symbols. This may be really useful if you give your
15044 main compilation unit on the command line, as @code{gnatxref} will then
15045 display every unused entity and 'with'ed package.
15049 Instead of producing the default output, @code{gnatxref} will generate a
15050 @file{tags} file that can be used by vi. For examples how to use this
15051 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15052 to the standard output, thus you will have to redirect it to a file.
15058 All these switches may be in any order on the command line, and may even
15059 appear after the file names. They need not be separated by spaces, thus
15060 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15061 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15063 @node gnatfind Switches
15064 @section @code{gnatfind} Switches
15067 The command line for @code{gnatfind} is:
15070 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15071 @r{[}@var{file1} @var{file2} @dots{}]
15079 An entity will be output only if it matches the regular expression found
15080 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15082 Omitting the pattern is equivalent to specifying @samp{*}, which
15083 will match any entity. Note that if you do not provide a pattern, you
15084 have to provide both a sourcefile and a line.
15086 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15087 for matching purposes. At the current time there is no support for
15088 8-bit codes other than Latin-1, or for wide characters in identifiers.
15091 @code{gnatfind} will look for references, bodies or declarations
15092 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15093 and column @var{column}. See @ref{Examples of gnatfind Usage}
15094 for syntax examples.
15097 is a decimal integer identifying the line number containing
15098 the reference to the entity (or entities) to be located.
15101 is a decimal integer identifying the exact location on the
15102 line of the first character of the identifier for the
15103 entity reference. Columns are numbered from 1.
15105 @item file1 file2 @dots{}
15106 The search will be restricted to these source files. If none are given, then
15107 the search will be done for every library file in the search path.
15108 These file must appear only after the pattern or sourcefile.
15110 These file names are considered to be regular expressions, so for instance
15111 specifying @file{source*.adb} is the same as giving every file in the current
15112 directory whose name starts with @file{source} and whose extension is
15115 The location of the spec of the entity will always be displayed, even if it
15116 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15117 occurrences of the entity in the separate units of the ones given on the
15118 command line will also be displayed.
15120 Note that if you specify at least one file in this part, @code{gnatfind} may
15121 sometimes not be able to find the body of the subprograms.
15126 At least one of 'sourcefile' or 'pattern' has to be present on
15129 The following switches are available:
15133 @cindex @option{--version} @command{gnatfind}
15134 Display Copyright and version, then exit disregarding all other options.
15137 @cindex @option{--help} @command{gnatfind}
15138 If @option{--version} was not used, display usage, then exit disregarding
15141 @item ^-a^/ALL_FILES^
15142 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15143 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15144 the read-only files found in the library search path. Otherwise, these files
15145 will be ignored. This option can be used to protect Gnat sources or your own
15146 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15147 much faster, and their output much smaller. Read-only here refers to access
15148 or permission status in the file system for the current user.
15151 @cindex @option{-aIDIR} (@command{gnatfind})
15152 When looking for source files also look in directory DIR. The order in which
15153 source file search is undertaken is the same as for @command{gnatmake}.
15156 @cindex @option{-aODIR} (@command{gnatfind})
15157 When searching for library and object files, look in directory
15158 DIR. The order in which library files are searched is the same as for
15159 @command{gnatmake}.
15162 @cindex @option{-nostdinc} (@command{gnatfind})
15163 Do not look for sources in the system default directory.
15166 @cindex @option{-nostdlib} (@command{gnatfind})
15167 Do not look for library files in the system default directory.
15169 @item --RTS=@var{rts-path}
15170 @cindex @option{--RTS} (@command{gnatfind})
15171 Specifies the default location of the runtime library. Same meaning as the
15172 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15174 @item ^-d^/DERIVED_TYPE_INFORMATION^
15175 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15176 If this switch is set, then @code{gnatfind} will output the parent type
15177 reference for each matching derived types.
15179 @item ^-e^/EXPRESSIONS^
15180 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15181 By default, @code{gnatfind} accept the simple regular expression set for
15182 @samp{pattern}. If this switch is set, then the pattern will be
15183 considered as full Unix-style regular expression.
15185 @item ^-f^/FULL_PATHNAME^
15186 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15187 If this switch is set, the output file names will be preceded by their
15188 directory (if the file was found in the search path). If this switch is
15189 not set, the directory will not be printed.
15191 @item ^-g^/IGNORE_LOCALS^
15192 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15193 If this switch is set, information is output only for library-level
15194 entities, ignoring local entities. The use of this switch may accelerate
15195 @code{gnatfind} and @code{gnatxref}.
15198 @cindex @option{-IDIR} (@command{gnatfind})
15199 Equivalent to @samp{-aODIR -aIDIR}.
15202 @cindex @option{-pFILE} (@command{gnatfind})
15203 Specify a project file (@pxref{Project Files}) to use.
15204 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15205 project file in the current directory.
15207 If a project file is either specified or found by the tools, then the content
15208 of the source directory and object directory lines are added as if they
15209 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15210 @samp{^-aO^/OBJECT_SEARCH^}.
15212 @item ^-r^/REFERENCES^
15213 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15214 By default, @code{gnatfind} will output only the information about the
15215 declaration, body or type completion of the entities. If this switch is
15216 set, the @code{gnatfind} will locate every reference to the entities in
15217 the files specified on the command line (or in every file in the search
15218 path if no file is given on the command line).
15220 @item ^-s^/PRINT_LINES^
15221 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15222 If this switch is set, then @code{gnatfind} will output the content
15223 of the Ada source file lines were the entity was found.
15225 @item ^-t^/TYPE_HIERARCHY^
15226 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15227 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15228 the specified type. It act like -d option but recursively from parent
15229 type to parent type. When this switch is set it is not possible to
15230 specify more than one file.
15235 All these switches may be in any order on the command line, and may even
15236 appear after the file names. They need not be separated by spaces, thus
15237 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15238 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15240 As stated previously, gnatfind will search in every directory in the
15241 search path. You can force it to look only in the current directory if
15242 you specify @code{*} at the end of the command line.
15244 @node Project Files for gnatxref and gnatfind
15245 @section Project Files for @command{gnatxref} and @command{gnatfind}
15248 Project files allow a programmer to specify how to compile its
15249 application, where to find sources, etc. These files are used
15251 primarily by GPS, but they can also be used
15254 @code{gnatxref} and @code{gnatfind}.
15256 A project file name must end with @file{.gpr}. If a single one is
15257 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15258 extract the information from it. If multiple project files are found, none of
15259 them is read, and you have to use the @samp{-p} switch to specify the one
15262 The following lines can be included, even though most of them have default
15263 values which can be used in most cases.
15264 The lines can be entered in any order in the file.
15265 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15266 each line. If you have multiple instances, only the last one is taken into
15271 [default: @code{"^./^[]^"}]
15272 specifies a directory where to look for source files. Multiple @code{src_dir}
15273 lines can be specified and they will be searched in the order they
15277 [default: @code{"^./^[]^"}]
15278 specifies a directory where to look for object and library files. Multiple
15279 @code{obj_dir} lines can be specified, and they will be searched in the order
15282 @item comp_opt=SWITCHES
15283 [default: @code{""}]
15284 creates a variable which can be referred to subsequently by using
15285 the @code{$@{comp_opt@}} notation. This is intended to store the default
15286 switches given to @command{gnatmake} and @command{gcc}.
15288 @item bind_opt=SWITCHES
15289 [default: @code{""}]
15290 creates a variable which can be referred to subsequently by using
15291 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15292 switches given to @command{gnatbind}.
15294 @item link_opt=SWITCHES
15295 [default: @code{""}]
15296 creates a variable which can be referred to subsequently by using
15297 the @samp{$@{link_opt@}} notation. This is intended to store the default
15298 switches given to @command{gnatlink}.
15300 @item main=EXECUTABLE
15301 [default: @code{""}]
15302 specifies the name of the executable for the application. This variable can
15303 be referred to in the following lines by using the @samp{$@{main@}} notation.
15306 @item comp_cmd=COMMAND
15307 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15310 @item comp_cmd=COMMAND
15311 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15313 specifies the command used to compile a single file in the application.
15316 @item make_cmd=COMMAND
15317 [default: @code{"GNAT MAKE $@{main@}
15318 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15319 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15320 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15323 @item make_cmd=COMMAND
15324 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15325 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15326 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15328 specifies the command used to recompile the whole application.
15330 @item run_cmd=COMMAND
15331 [default: @code{"$@{main@}"}]
15332 specifies the command used to run the application.
15334 @item debug_cmd=COMMAND
15335 [default: @code{"gdb $@{main@}"}]
15336 specifies the command used to debug the application
15341 @command{gnatxref} and @command{gnatfind} only take into account the
15342 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15344 @node Regular Expressions in gnatfind and gnatxref
15345 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15348 As specified in the section about @command{gnatfind}, the pattern can be a
15349 regular expression. Actually, there are to set of regular expressions
15350 which are recognized by the program:
15353 @item globbing patterns
15354 These are the most usual regular expression. They are the same that you
15355 generally used in a Unix shell command line, or in a DOS session.
15357 Here is a more formal grammar:
15364 term ::= elmt -- matches elmt
15365 term ::= elmt elmt -- concatenation (elmt then elmt)
15366 term ::= * -- any string of 0 or more characters
15367 term ::= ? -- matches any character
15368 term ::= [char @{char@}] -- matches any character listed
15369 term ::= [char - char] -- matches any character in range
15373 @item full regular expression
15374 The second set of regular expressions is much more powerful. This is the
15375 type of regular expressions recognized by utilities such a @file{grep}.
15377 The following is the form of a regular expression, expressed in Ada
15378 reference manual style BNF is as follows
15385 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15387 term ::= item @{item@} -- concatenation (item then item)
15389 item ::= elmt -- match elmt
15390 item ::= elmt * -- zero or more elmt's
15391 item ::= elmt + -- one or more elmt's
15392 item ::= elmt ? -- matches elmt or nothing
15395 elmt ::= nschar -- matches given character
15396 elmt ::= [nschar @{nschar@}] -- matches any character listed
15397 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15398 elmt ::= [char - char] -- matches chars in given range
15399 elmt ::= \ char -- matches given character
15400 elmt ::= . -- matches any single character
15401 elmt ::= ( regexp ) -- parens used for grouping
15403 char ::= any character, including special characters
15404 nschar ::= any character except ()[].*+?^^^
15408 Following are a few examples:
15412 will match any of the two strings @samp{abcde} and @samp{fghi},
15415 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15416 @samp{abcccd}, and so on,
15419 will match any string which has only lowercase characters in it (and at
15420 least one character.
15425 @node Examples of gnatxref Usage
15426 @section Examples of @code{gnatxref} Usage
15428 @subsection General Usage
15431 For the following examples, we will consider the following units:
15433 @smallexample @c ada
15439 3: procedure Foo (B : in Integer);
15446 1: package body Main is
15447 2: procedure Foo (B : in Integer) is
15458 2: procedure Print (B : Integer);
15467 The first thing to do is to recompile your application (for instance, in
15468 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15469 the cross-referencing information.
15470 You can then issue any of the following commands:
15472 @item gnatxref main.adb
15473 @code{gnatxref} generates cross-reference information for main.adb
15474 and every unit 'with'ed by main.adb.
15476 The output would be:
15484 Decl: main.ads 3:20
15485 Body: main.adb 2:20
15486 Ref: main.adb 4:13 5:13 6:19
15489 Ref: main.adb 6:8 7:8
15499 Decl: main.ads 3:15
15500 Body: main.adb 2:15
15503 Body: main.adb 1:14
15506 Ref: main.adb 6:12 7:12
15510 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15511 its body is in main.adb, line 1, column 14 and is not referenced any where.
15513 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15514 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15516 @item gnatxref package1.adb package2.ads
15517 @code{gnatxref} will generates cross-reference information for
15518 package1.adb, package2.ads and any other package 'with'ed by any
15524 @subsection Using gnatxref with vi
15526 @code{gnatxref} can generate a tags file output, which can be used
15527 directly from @command{vi}. Note that the standard version of @command{vi}
15528 will not work properly with overloaded symbols. Consider using another
15529 free implementation of @command{vi}, such as @command{vim}.
15532 $ gnatxref -v gnatfind.adb > tags
15536 will generate the tags file for @code{gnatfind} itself (if the sources
15537 are in the search path!).
15539 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15540 (replacing @var{entity} by whatever you are looking for), and vi will
15541 display a new file with the corresponding declaration of entity.
15544 @node Examples of gnatfind Usage
15545 @section Examples of @code{gnatfind} Usage
15549 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15550 Find declarations for all entities xyz referenced at least once in
15551 main.adb. The references are search in every library file in the search
15554 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15557 The output will look like:
15559 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15560 ^directory/^[directory]^main.adb:24:10: xyz <= body
15561 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15565 that is to say, one of the entities xyz found in main.adb is declared at
15566 line 12 of main.ads (and its body is in main.adb), and another one is
15567 declared at line 45 of foo.ads
15569 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15570 This is the same command as the previous one, instead @code{gnatfind} will
15571 display the content of the Ada source file lines.
15573 The output will look like:
15576 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15578 ^directory/^[directory]^main.adb:24:10: xyz <= body
15580 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15585 This can make it easier to find exactly the location your are looking
15588 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
15589 Find references to all entities containing an x that are
15590 referenced on line 123 of main.ads.
15591 The references will be searched only in main.ads and foo.adb.
15593 @item gnatfind main.ads:123
15594 Find declarations and bodies for all entities that are referenced on
15595 line 123 of main.ads.
15597 This is the same as @code{gnatfind "*":main.adb:123}.
15599 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
15600 Find the declaration for the entity referenced at column 45 in
15601 line 123 of file main.adb in directory mydir. Note that it
15602 is usual to omit the identifier name when the column is given,
15603 since the column position identifies a unique reference.
15605 The column has to be the beginning of the identifier, and should not
15606 point to any character in the middle of the identifier.
15610 @c *********************************
15611 @node The GNAT Pretty-Printer gnatpp
15612 @chapter The GNAT Pretty-Printer @command{gnatpp}
15614 @cindex Pretty-Printer
15617 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
15618 for source reformatting / pretty-printing.
15619 It takes an Ada source file as input and generates a reformatted
15621 You can specify various style directives via switches; e.g.,
15622 identifier case conventions, rules of indentation, and comment layout.
15624 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
15625 tree for the input source and thus requires the input to be syntactically and
15626 semantically legal.
15627 If this condition is not met, @command{gnatpp} will terminate with an
15628 error message; no output file will be generated.
15630 If the source files presented to @command{gnatpp} contain
15631 preprocessing directives, then the output file will
15632 correspond to the generated source after all
15633 preprocessing is carried out. There is no way
15634 using @command{gnatpp} to obtain pretty printed files that
15635 include the preprocessing directives.
15637 If the compilation unit
15638 contained in the input source depends semantically upon units located
15639 outside the current directory, you have to provide the source search path
15640 when invoking @command{gnatpp}, if these units are contained in files with
15641 names that do not follow the GNAT file naming rules, you have to provide
15642 the configuration file describing the corresponding naming scheme;
15643 see the description of the @command{gnatpp}
15644 switches below. Another possibility is to use a project file and to
15645 call @command{gnatpp} through the @command{gnat} driver
15647 The @command{gnatpp} command has the form
15650 $ gnatpp @ovar{switches} @var{filename}
15657 @var{switches} is an optional sequence of switches defining such properties as
15658 the formatting rules, the source search path, and the destination for the
15662 @var{filename} is the name (including the extension) of the source file to
15663 reformat; ``wildcards'' or several file names on the same gnatpp command are
15664 allowed. The file name may contain path information; it does not have to
15665 follow the GNAT file naming rules
15669 * Switches for gnatpp::
15670 * Formatting Rules::
15673 @node Switches for gnatpp
15674 @section Switches for @command{gnatpp}
15677 The following subsections describe the various switches accepted by
15678 @command{gnatpp}, organized by category.
15681 You specify a switch by supplying a name and generally also a value.
15682 In many cases the values for a switch with a given name are incompatible with
15684 (for example the switch that controls the casing of a reserved word may have
15685 exactly one value: upper case, lower case, or
15686 mixed case) and thus exactly one such switch can be in effect for an
15687 invocation of @command{gnatpp}.
15688 If more than one is supplied, the last one is used.
15689 However, some values for the same switch are mutually compatible.
15690 You may supply several such switches to @command{gnatpp}, but then
15691 each must be specified in full, with both the name and the value.
15692 Abbreviated forms (the name appearing once, followed by each value) are
15694 For example, to set
15695 the alignment of the assignment delimiter both in declarations and in
15696 assignment statements, you must write @option{-A2A3}
15697 (or @option{-A2 -A3}), but not @option{-A23}.
15701 In many cases the set of options for a given qualifier are incompatible with
15702 each other (for example the qualifier that controls the casing of a reserved
15703 word may have exactly one option, which specifies either upper case, lower
15704 case, or mixed case), and thus exactly one such option can be in effect for
15705 an invocation of @command{gnatpp}.
15706 If more than one is supplied, the last one is used.
15707 However, some qualifiers have options that are mutually compatible,
15708 and then you may then supply several such options when invoking
15712 In most cases, it is obvious whether or not the
15713 ^values for a switch with a given name^options for a given qualifier^
15714 are compatible with each other.
15715 When the semantics might not be evident, the summaries below explicitly
15716 indicate the effect.
15719 * Alignment Control::
15721 * Construct Layout Control::
15722 * General Text Layout Control::
15723 * Other Formatting Options::
15724 * Setting the Source Search Path::
15725 * Output File Control::
15726 * Other gnatpp Switches::
15729 @node Alignment Control
15730 @subsection Alignment Control
15731 @cindex Alignment control in @command{gnatpp}
15734 Programs can be easier to read if certain constructs are vertically aligned.
15735 By default all alignments are set ON.
15736 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
15737 OFF, and then use one or more of the other
15738 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
15739 to activate alignment for specific constructs.
15742 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
15746 Set all alignments to ON
15749 @item ^-A0^/ALIGN=OFF^
15750 Set all alignments to OFF
15752 @item ^-A1^/ALIGN=COLONS^
15753 Align @code{:} in declarations
15755 @item ^-A2^/ALIGN=DECLARATIONS^
15756 Align @code{:=} in initializations in declarations
15758 @item ^-A3^/ALIGN=STATEMENTS^
15759 Align @code{:=} in assignment statements
15761 @item ^-A4^/ALIGN=ARROWS^
15762 Align @code{=>} in associations
15764 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
15765 Align @code{at} keywords in the component clauses in record
15766 representation clauses
15770 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
15773 @node Casing Control
15774 @subsection Casing Control
15775 @cindex Casing control in @command{gnatpp}
15778 @command{gnatpp} allows you to specify the casing for reserved words,
15779 pragma names, attribute designators and identifiers.
15780 For identifiers you may define a
15781 general rule for name casing but also override this rule
15782 via a set of dictionary files.
15784 Three types of casing are supported: lower case, upper case, and mixed case.
15785 Lower and upper case are self-explanatory (but since some letters in
15786 Latin1 and other GNAT-supported character sets
15787 exist only in lower-case form, an upper case conversion will have no
15789 ``Mixed case'' means that the first letter, and also each letter immediately
15790 following an underscore, are converted to their uppercase forms;
15791 all the other letters are converted to their lowercase forms.
15794 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
15795 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
15796 Attribute designators are lower case
15798 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
15799 Attribute designators are upper case
15801 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
15802 Attribute designators are mixed case (this is the default)
15804 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
15805 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
15806 Keywords (technically, these are known in Ada as @emph{reserved words}) are
15807 lower case (this is the default)
15809 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
15810 Keywords are upper case
15812 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
15813 @item ^-nD^/NAME_CASING=AS_DECLARED^
15814 Name casing for defining occurrences are as they appear in the source file
15815 (this is the default)
15817 @item ^-nU^/NAME_CASING=UPPER_CASE^
15818 Names are in upper case
15820 @item ^-nL^/NAME_CASING=LOWER_CASE^
15821 Names are in lower case
15823 @item ^-nM^/NAME_CASING=MIXED_CASE^
15824 Names are in mixed case
15826 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
15827 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
15828 Pragma names are lower case
15830 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
15831 Pragma names are upper case
15833 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
15834 Pragma names are mixed case (this is the default)
15836 @item ^-D@var{file}^/DICTIONARY=@var{file}^
15837 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
15838 Use @var{file} as a @emph{dictionary file} that defines
15839 the casing for a set of specified names,
15840 thereby overriding the effect on these names by
15841 any explicit or implicit
15842 ^-n^/NAME_CASING^ switch.
15843 To supply more than one dictionary file,
15844 use ^several @option{-D} switches^a list of files as options^.
15847 @option{gnatpp} implicitly uses a @emph{default dictionary file}
15848 to define the casing for the Ada predefined names and
15849 the names declared in the GNAT libraries.
15851 @item ^-D-^/SPECIFIC_CASING^
15852 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
15853 Do not use the default dictionary file;
15854 instead, use the casing
15855 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
15860 The structure of a dictionary file, and details on the conventions
15861 used in the default dictionary file, are defined in @ref{Name Casing}.
15863 The @option{^-D-^/SPECIFIC_CASING^} and
15864 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
15867 @node Construct Layout Control
15868 @subsection Construct Layout Control
15869 @cindex Layout control in @command{gnatpp}
15872 This group of @command{gnatpp} switches controls the layout of comments and
15873 complex syntactic constructs. See @ref{Formatting Comments} for details
15877 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
15878 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
15879 All the comments remain unchanged
15881 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
15882 GNAT-style comment line indentation (this is the default).
15884 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
15885 Reference-manual comment line indentation.
15887 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
15888 GNAT-style comment beginning
15890 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
15891 Reformat comment blocks
15893 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
15894 Keep unchanged special form comments
15896 Reformat comment blocks
15898 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
15899 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
15900 GNAT-style layout (this is the default)
15902 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
15905 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
15908 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
15910 All the VT characters are removed from the comment text. All the HT characters
15911 are expanded with the sequences of space characters to get to the next tab
15914 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
15915 @item ^--no-separate-is^/NO_SEPARATE_IS^
15916 Do not place the keyword @code{is} on a separate line in a subprogram body in
15917 case if the spec occupies more then one line.
15919 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
15920 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
15921 Place the keyword @code{loop} in FOR and WHILE loop statements and the
15922 keyword @code{then} in IF statements on a separate line.
15924 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
15925 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
15926 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
15927 keyword @code{then} in IF statements on a separate line. This option is
15928 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
15930 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
15931 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
15932 Start each USE clause in a context clause from a separate line.
15934 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
15935 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
15936 Use a separate line for a loop or block statement name, but do not use an extra
15937 indentation level for the statement itself.
15943 The @option{-c1} and @option{-c2} switches are incompatible.
15944 The @option{-c3} and @option{-c4} switches are compatible with each other and
15945 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
15946 the other comment formatting switches.
15948 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
15953 For the @option{/COMMENTS_LAYOUT} qualifier:
15956 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
15958 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
15959 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
15963 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
15964 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
15967 @node General Text Layout Control
15968 @subsection General Text Layout Control
15971 These switches allow control over line length and indentation.
15974 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
15975 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
15976 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
15978 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
15979 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
15980 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
15982 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
15983 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
15984 Indentation level for continuation lines (relative to the line being
15985 continued), @var{nnn} from 1@dots{}9.
15987 value is one less then the (normal) indentation level, unless the
15988 indentation is set to 1 (in which case the default value for continuation
15989 line indentation is also 1)
15992 @node Other Formatting Options
15993 @subsection Other Formatting Options
15996 These switches control the inclusion of missing end/exit labels, and
15997 the indentation level in @b{case} statements.
16000 @item ^-e^/NO_MISSED_LABELS^
16001 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16002 Do not insert missing end/exit labels. An end label is the name of
16003 a construct that may optionally be repeated at the end of the
16004 construct's declaration;
16005 e.g., the names of packages, subprograms, and tasks.
16006 An exit label is the name of a loop that may appear as target
16007 of an exit statement within the loop.
16008 By default, @command{gnatpp} inserts these end/exit labels when
16009 they are absent from the original source. This option suppresses such
16010 insertion, so that the formatted source reflects the original.
16012 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16013 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16014 Insert a Form Feed character after a pragma Page.
16016 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16017 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16018 Do not use an additional indentation level for @b{case} alternatives
16019 and variants if there are @var{nnn} or more (the default
16021 If @var{nnn} is 0, an additional indentation level is
16022 used for @b{case} alternatives and variants regardless of their number.
16025 @node Setting the Source Search Path
16026 @subsection Setting the Source Search Path
16029 To define the search path for the input source file, @command{gnatpp}
16030 uses the same switches as the GNAT compiler, with the same effects.
16033 @item ^-I^/SEARCH=^@var{dir}
16034 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16035 The same as the corresponding gcc switch
16037 @item ^-I-^/NOCURRENT_DIRECTORY^
16038 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16039 The same as the corresponding gcc switch
16041 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16042 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16043 The same as the corresponding gcc switch
16045 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16046 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16047 The same as the corresponding gcc switch
16051 @node Output File Control
16052 @subsection Output File Control
16055 By default the output is sent to the file whose name is obtained by appending
16056 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16057 (if the file with this name already exists, it is unconditionally overwritten).
16058 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16059 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16061 The output may be redirected by the following switches:
16064 @item ^-pipe^/STANDARD_OUTPUT^
16065 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16066 Send the output to @code{Standard_Output}
16068 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16069 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16070 Write the output into @var{output_file}.
16071 If @var{output_file} already exists, @command{gnatpp} terminates without
16072 reading or processing the input file.
16074 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16075 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16076 Write the output into @var{output_file}, overwriting the existing file
16077 (if one is present).
16079 @item ^-r^/REPLACE^
16080 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16081 Replace the input source file with the reformatted output, and copy the
16082 original input source into the file whose name is obtained by appending the
16083 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16084 If a file with this name already exists, @command{gnatpp} terminates without
16085 reading or processing the input file.
16087 @item ^-rf^/OVERRIDING_REPLACE^
16088 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16089 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16090 already exists, it is overwritten.
16092 @item ^-rnb^/REPLACE_NO_BACKUP^
16093 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16094 Replace the input source file with the reformatted output without
16095 creating any backup copy of the input source.
16097 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16098 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16099 Specifies the format of the reformatted output file. The @var{xxx}
16100 ^string specified with the switch^option^ may be either
16102 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16103 @item ``@option{^crlf^CRLF^}''
16104 the same as @option{^crlf^CRLF^}
16105 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16106 @item ``@option{^lf^LF^}''
16107 the same as @option{^unix^UNIX^}
16110 @item ^-W^/RESULT_ENCODING=^@var{e}
16111 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16112 Specify the wide character encoding method used to write the code in the
16114 @var{e} is one of the following:
16122 Upper half encoding
16124 @item ^s^SHIFT_JIS^
16134 Brackets encoding (default value)
16140 Options @option{^-pipe^/STANDARD_OUTPUT^},
16141 @option{^-o^/OUTPUT^} and
16142 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16143 contains only one file to reformat.
16145 @option{^--eol^/END_OF_LINE^}
16147 @option{^-W^/RESULT_ENCODING^}
16148 cannot be used together
16149 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16151 @node Other gnatpp Switches
16152 @subsection Other @code{gnatpp} Switches
16155 The additional @command{gnatpp} switches are defined in this subsection.
16158 @item ^-files @var{filename}^/FILES=@var{output_file}^
16159 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16160 Take the argument source files from the specified file. This file should be an
16161 ordinary textual file containing file names separated by spaces or
16162 line breaks. You can use this switch more then once in the same call to
16163 @command{gnatpp}. You also can combine this switch with explicit list of
16166 @item ^-v^/VERBOSE^
16167 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16169 @command{gnatpp} generates version information and then
16170 a trace of the actions it takes to produce or obtain the ASIS tree.
16172 @item ^-w^/WARNINGS^
16173 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16175 @command{gnatpp} generates a warning whenever it cannot provide
16176 a required layout in the result source.
16179 @node Formatting Rules
16180 @section Formatting Rules
16183 The following subsections show how @command{gnatpp} treats ``white space'',
16184 comments, program layout, and name casing.
16185 They provide the detailed descriptions of the switches shown above.
16188 * White Space and Empty Lines::
16189 * Formatting Comments::
16190 * Construct Layout::
16194 @node White Space and Empty Lines
16195 @subsection White Space and Empty Lines
16198 @command{gnatpp} does not have an option to control space characters.
16199 It will add or remove spaces according to the style illustrated by the
16200 examples in the @cite{Ada Reference Manual}.
16202 The only format effectors
16203 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16204 that will appear in the output file are platform-specific line breaks,
16205 and also format effectors within (but not at the end of) comments.
16206 In particular, each horizontal tab character that is not inside
16207 a comment will be treated as a space and thus will appear in the
16208 output file as zero or more spaces depending on
16209 the reformatting of the line in which it appears.
16210 The only exception is a Form Feed character, which is inserted after a
16211 pragma @code{Page} when @option{-ff} is set.
16213 The output file will contain no lines with trailing ``white space'' (spaces,
16216 Empty lines in the original source are preserved
16217 only if they separate declarations or statements.
16218 In such contexts, a
16219 sequence of two or more empty lines is replaced by exactly one empty line.
16220 Note that a blank line will be removed if it separates two ``comment blocks''
16221 (a comment block is a sequence of whole-line comments).
16222 In order to preserve a visual separation between comment blocks, use an
16223 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16224 Likewise, if for some reason you wish to have a sequence of empty lines,
16225 use a sequence of empty comments instead.
16227 @node Formatting Comments
16228 @subsection Formatting Comments
16231 Comments in Ada code are of two kinds:
16234 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16235 ``white space'') on a line
16238 an @emph{end-of-line comment}, which follows some other Ada lexical element
16243 The indentation of a whole-line comment is that of either
16244 the preceding or following line in
16245 the formatted source, depending on switch settings as will be described below.
16247 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16248 between the end of the preceding Ada lexical element and the beginning
16249 of the comment as appear in the original source,
16250 unless either the comment has to be split to
16251 satisfy the line length limitation, or else the next line contains a
16252 whole line comment that is considered a continuation of this end-of-line
16253 comment (because it starts at the same position).
16255 cases, the start of the end-of-line comment is moved right to the nearest
16256 multiple of the indentation level.
16257 This may result in a ``line overflow'' (the right-shifted comment extending
16258 beyond the maximum line length), in which case the comment is split as
16261 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16262 (GNAT-style comment line indentation)
16263 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16264 (reference-manual comment line indentation).
16265 With reference-manual style, a whole-line comment is indented as if it
16266 were a declaration or statement at the same place
16267 (i.e., according to the indentation of the preceding line(s)).
16268 With GNAT style, a whole-line comment that is immediately followed by an
16269 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16270 word @b{begin}, is indented based on the construct that follows it.
16273 @smallexample @c ada
16285 Reference-manual indentation produces:
16287 @smallexample @c ada
16299 while GNAT-style indentation produces:
16301 @smallexample @c ada
16313 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16314 (GNAT style comment beginning) has the following
16319 For each whole-line comment that does not end with two hyphens,
16320 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16321 to ensure that there are at least two spaces between these hyphens and the
16322 first non-blank character of the comment.
16326 For an end-of-line comment, if in the original source the next line is a
16327 whole-line comment that starts at the same position
16328 as the end-of-line comment,
16329 then the whole-line comment (and all whole-line comments
16330 that follow it and that start at the same position)
16331 will start at this position in the output file.
16334 That is, if in the original source we have:
16336 @smallexample @c ada
16339 A := B + C; -- B must be in the range Low1..High1
16340 -- C must be in the range Low2..High2
16341 --B+C will be in the range Low1+Low2..High1+High2
16347 Then in the formatted source we get
16349 @smallexample @c ada
16352 A := B + C; -- B must be in the range Low1..High1
16353 -- C must be in the range Low2..High2
16354 -- B+C will be in the range Low1+Low2..High1+High2
16360 A comment that exceeds the line length limit will be split.
16362 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16363 the line belongs to a reformattable block, splitting the line generates a
16364 @command{gnatpp} warning.
16365 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16366 comments may be reformatted in typical
16367 word processor style (that is, moving words between lines and putting as
16368 many words in a line as possible).
16371 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16372 that has a special format (that is, a character that is neither a letter nor digit
16373 not white space nor line break immediately following the leading @code{--} of
16374 the comment) should be without any change moved from the argument source
16375 into reformatted source. This switch allows to preserve comments that are used
16376 as a special marks in the code (e.g.@: SPARK annotation).
16378 @node Construct Layout
16379 @subsection Construct Layout
16382 In several cases the suggested layout in the Ada Reference Manual includes
16383 an extra level of indentation that many programmers prefer to avoid. The
16384 affected cases include:
16388 @item Record type declaration (RM 3.8)
16390 @item Record representation clause (RM 13.5.1)
16392 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16394 @item Block statement in case if a block has a statement identifier (RM 5.6)
16398 In compact mode (when GNAT style layout or compact layout is set),
16399 the pretty printer uses one level of indentation instead
16400 of two. This is achieved in the record definition and record representation
16401 clause cases by putting the @code{record} keyword on the same line as the
16402 start of the declaration or representation clause, and in the block and loop
16403 case by putting the block or loop header on the same line as the statement
16407 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16408 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16409 layout on the one hand, and uncompact layout
16410 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16411 can be illustrated by the following examples:
16415 @multitable @columnfractions .5 .5
16416 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16419 @smallexample @c ada
16426 @smallexample @c ada
16435 @smallexample @c ada
16437 a at 0 range 0 .. 31;
16438 b at 4 range 0 .. 31;
16442 @smallexample @c ada
16445 a at 0 range 0 .. 31;
16446 b at 4 range 0 .. 31;
16451 @smallexample @c ada
16459 @smallexample @c ada
16469 @smallexample @c ada
16470 Clear : for J in 1 .. 10 loop
16475 @smallexample @c ada
16477 for J in 1 .. 10 loop
16488 GNAT style, compact layout Uncompact layout
16490 type q is record type q is
16491 a : integer; record
16492 b : integer; a : integer;
16493 end record; b : integer;
16496 for q use record for q use
16497 a at 0 range 0 .. 31; record
16498 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16499 end record; b at 4 range 0 .. 31;
16502 Block : declare Block :
16503 A : Integer := 3; declare
16504 begin A : Integer := 3;
16506 end Block; Proc (A, A);
16509 Clear : for J in 1 .. 10 loop Clear :
16510 A (J) := 0; for J in 1 .. 10 loop
16511 end loop Clear; A (J) := 0;
16518 A further difference between GNAT style layout and compact layout is that
16519 GNAT style layout inserts empty lines as separation for
16520 compound statements, return statements and bodies.
16522 Note that the layout specified by
16523 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16524 for named block and loop statements overrides the layout defined by these
16525 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16526 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16527 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16530 @subsection Name Casing
16533 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16534 the same casing as the corresponding defining identifier.
16536 You control the casing for defining occurrences via the
16537 @option{^-n^/NAME_CASING^} switch.
16539 With @option{-nD} (``as declared'', which is the default),
16542 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16544 defining occurrences appear exactly as in the source file
16545 where they are declared.
16546 The other ^values for this switch^options for this qualifier^ ---
16547 @option{^-nU^UPPER_CASE^},
16548 @option{^-nL^LOWER_CASE^},
16549 @option{^-nM^MIXED_CASE^} ---
16551 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16552 If @command{gnatpp} changes the casing of a defining
16553 occurrence, it analogously changes the casing of all the
16554 usage occurrences of this name.
16556 If the defining occurrence of a name is not in the source compilation unit
16557 currently being processed by @command{gnatpp}, the casing of each reference to
16558 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16559 switch (subject to the dictionary file mechanism described below).
16560 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16562 casing for the defining occurrence of the name.
16564 Some names may need to be spelled with casing conventions that are not
16565 covered by the upper-, lower-, and mixed-case transformations.
16566 You can arrange correct casing by placing such names in a
16567 @emph{dictionary file},
16568 and then supplying a @option{^-D^/DICTIONARY^} switch.
16569 The casing of names from dictionary files overrides
16570 any @option{^-n^/NAME_CASING^} switch.
16572 To handle the casing of Ada predefined names and the names from GNAT libraries,
16573 @command{gnatpp} assumes a default dictionary file.
16574 The name of each predefined entity is spelled with the same casing as is used
16575 for the entity in the @cite{Ada Reference Manual}.
16576 The name of each entity in the GNAT libraries is spelled with the same casing
16577 as is used in the declaration of that entity.
16579 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
16580 default dictionary file.
16581 Instead, the casing for predefined and GNAT-defined names will be established
16582 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
16583 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
16584 will appear as just shown,
16585 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
16586 To ensure that even such names are rendered in uppercase,
16587 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
16588 (or else, less conveniently, place these names in upper case in a dictionary
16591 A dictionary file is
16592 a plain text file; each line in this file can be either a blank line
16593 (containing only space characters and ASCII.HT characters), an Ada comment
16594 line, or the specification of exactly one @emph{casing schema}.
16596 A casing schema is a string that has the following syntax:
16600 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
16602 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
16607 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
16608 @var{identifier} lexical element and the @var{letter_or_digit} category.)
16610 The casing schema string can be followed by white space and/or an Ada-style
16611 comment; any amount of white space is allowed before the string.
16613 If a dictionary file is passed as
16615 the value of a @option{-D@var{file}} switch
16618 an option to the @option{/DICTIONARY} qualifier
16621 simple name and every identifier, @command{gnatpp} checks if the dictionary
16622 defines the casing for the name or for some of its parts (the term ``subword''
16623 is used below to denote the part of a name which is delimited by ``_'' or by
16624 the beginning or end of the word and which does not contain any ``_'' inside):
16628 if the whole name is in the dictionary, @command{gnatpp} uses for this name
16629 the casing defined by the dictionary; no subwords are checked for this word
16632 for every subword @command{gnatpp} checks if the dictionary contains the
16633 corresponding string of the form @code{*@var{simple_identifier}*},
16634 and if it does, the casing of this @var{simple_identifier} is used
16638 if the whole name does not contain any ``_'' inside, and if for this name
16639 the dictionary contains two entries - one of the form @var{identifier},
16640 and another - of the form *@var{simple_identifier}*, then the first one
16641 is applied to define the casing of this name
16644 if more than one dictionary file is passed as @command{gnatpp} switches, each
16645 dictionary adds new casing exceptions and overrides all the existing casing
16646 exceptions set by the previous dictionaries
16649 when @command{gnatpp} checks if the word or subword is in the dictionary,
16650 this check is not case sensitive
16654 For example, suppose we have the following source to reformat:
16656 @smallexample @c ada
16659 name1 : integer := 1;
16660 name4_name3_name2 : integer := 2;
16661 name2_name3_name4 : Boolean;
16664 name2_name3_name4 := name4_name3_name2 > name1;
16670 And suppose we have two dictionaries:
16687 If @command{gnatpp} is called with the following switches:
16691 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
16694 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
16699 then we will get the following name casing in the @command{gnatpp} output:
16701 @smallexample @c ada
16704 NAME1 : Integer := 1;
16705 Name4_NAME3_Name2 : Integer := 2;
16706 Name2_NAME3_Name4 : Boolean;
16709 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
16714 @c *********************************
16715 @node The GNAT Metric Tool gnatmetric
16716 @chapter The GNAT Metric Tool @command{gnatmetric}
16718 @cindex Metric tool
16721 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
16722 for computing various program metrics.
16723 It takes an Ada source file as input and generates a file containing the
16724 metrics data as output. Various switches control which
16725 metrics are computed and output.
16727 @command{gnatmetric} generates and uses the ASIS
16728 tree for the input source and thus requires the input to be syntactically and
16729 semantically legal.
16730 If this condition is not met, @command{gnatmetric} will generate
16731 an error message; no metric information for this file will be
16732 computed and reported.
16734 If the compilation unit contained in the input source depends semantically
16735 upon units in files located outside the current directory, you have to provide
16736 the source search path when invoking @command{gnatmetric}.
16737 If it depends semantically upon units that are contained
16738 in files with names that do not follow the GNAT file naming rules, you have to
16739 provide the configuration file describing the corresponding naming scheme (see
16740 the description of the @command{gnatmetric} switches below.)
16741 Alternatively, you may use a project file and invoke @command{gnatmetric}
16742 through the @command{gnat} driver.
16744 The @command{gnatmetric} command has the form
16747 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
16754 @var{switches} specify the metrics to compute and define the destination for
16758 Each @var{filename} is the name (including the extension) of a source
16759 file to process. ``Wildcards'' are allowed, and
16760 the file name may contain path information.
16761 If no @var{filename} is supplied, then the @var{switches} list must contain
16763 @option{-files} switch (@pxref{Other gnatmetric Switches}).
16764 Including both a @option{-files} switch and one or more
16765 @var{filename} arguments is permitted.
16768 @samp{-cargs @var{gcc_switches}} is a list of switches for
16769 @command{gcc}. They will be passed on to all compiler invocations made by
16770 @command{gnatmetric} to generate the ASIS trees. Here you can provide
16771 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
16772 and use the @option{-gnatec} switch to set the configuration file.
16776 * Switches for gnatmetric::
16779 @node Switches for gnatmetric
16780 @section Switches for @command{gnatmetric}
16783 The following subsections describe the various switches accepted by
16784 @command{gnatmetric}, organized by category.
16787 * Output Files Control::
16788 * Disable Metrics For Local Units::
16789 * Specifying a set of metrics to compute::
16790 * Other gnatmetric Switches::
16791 * Generate project-wide metrics::
16794 @node Output Files Control
16795 @subsection Output File Control
16796 @cindex Output file control in @command{gnatmetric}
16799 @command{gnatmetric} has two output formats. It can generate a
16800 textual (human-readable) form, and also XML. By default only textual
16801 output is generated.
16803 When generating the output in textual form, @command{gnatmetric} creates
16804 for each Ada source file a corresponding text file
16805 containing the computed metrics, except for the case when the set of metrics
16806 specified by gnatmetric parameters consists only of metrics that are computed
16807 for the whole set of analyzed sources, but not for each Ada source.
16808 By default, this file is placed in the same directory as where the source
16809 file is located, and its name is obtained
16810 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
16813 All the output information generated in XML format is placed in a single
16814 file. By default this file is placed in the current directory and has the
16815 name ^@file{metrix.xml}^@file{METRIX$XML}^.
16817 Some of the computed metrics are summed over the units passed to
16818 @command{gnatmetric}; for example, the total number of lines of code.
16819 By default this information is sent to @file{stdout}, but a file
16820 can be specified with the @option{-og} switch.
16822 The following switches control the @command{gnatmetric} output:
16825 @cindex @option{^-x^/XML^} (@command{gnatmetric})
16827 Generate the XML output
16829 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
16830 @item ^-nt^/NO_TEXT^
16831 Do not generate the output in text form (implies @option{^-x^/XML^})
16833 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
16834 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
16835 Put textual files with detailed metrics into @var{output_dir}
16837 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
16838 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
16839 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
16840 in the name of the output file.
16842 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
16843 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
16844 Put global metrics into @var{file_name}
16846 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
16847 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
16848 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
16850 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
16851 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
16852 Use ``short'' source file names in the output. (The @command{gnatmetric}
16853 output includes the name(s) of the Ada source file(s) from which the metrics
16854 are computed. By default each name includes the absolute path. The
16855 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
16856 to exclude all directory information from the file names that are output.)
16860 @node Disable Metrics For Local Units
16861 @subsection Disable Metrics For Local Units
16862 @cindex Disable Metrics For Local Units in @command{gnatmetric}
16865 @command{gnatmetric} relies on the GNAT compilation model @minus{}
16867 unit per one source file. It computes line metrics for the whole source
16868 file, and it also computes syntax
16869 and complexity metrics for the file's outermost unit.
16871 By default, @command{gnatmetric} will also compute all metrics for certain
16872 kinds of locally declared program units:
16876 subprogram (and generic subprogram) bodies;
16879 package (and generic package) specs and bodies;
16882 task object and type specifications and bodies;
16885 protected object and type specifications and bodies.
16889 These kinds of entities will be referred to as
16890 @emph{eligible local program units}, or simply @emph{eligible local units},
16891 @cindex Eligible local unit (for @command{gnatmetric})
16892 in the discussion below.
16894 Note that a subprogram declaration, generic instantiation,
16895 or renaming declaration only receives metrics
16896 computation when it appear as the outermost entity
16899 Suppression of metrics computation for eligible local units can be
16900 obtained via the following switch:
16903 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
16904 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
16905 Do not compute detailed metrics for eligible local program units
16909 @node Specifying a set of metrics to compute
16910 @subsection Specifying a set of metrics to compute
16913 By default all the metrics are computed and reported. The switches
16914 described in this subsection allow you to control, on an individual
16915 basis, whether metrics are computed and
16916 reported. If at least one positive metric
16917 switch is specified (that is, a switch that defines that a given
16918 metric or set of metrics is to be computed), then only
16919 explicitly specified metrics are reported.
16922 * Line Metrics Control::
16923 * Syntax Metrics Control::
16924 * Complexity Metrics Control::
16925 * Object-Oriented Metrics Control::
16928 @node Line Metrics Control
16929 @subsubsection Line Metrics Control
16930 @cindex Line metrics control in @command{gnatmetric}
16933 For any (legal) source file, and for each of its
16934 eligible local program units, @command{gnatmetric} computes the following
16939 the total number of lines;
16942 the total number of code lines (i.e., non-blank lines that are not comments)
16945 the number of comment lines
16948 the number of code lines containing end-of-line comments;
16951 the comment percentage: the ratio between the number of lines that contain
16952 comments and the number of all non-blank lines, expressed as a percentage;
16955 the number of empty lines and lines containing only space characters and/or
16956 format effectors (blank lines)
16959 the average number of code lines in subprogram bodies, task bodies, entry
16960 bodies and statement sequences in package bodies (this metric is only computed
16961 across the whole set of the analyzed units)
16966 @command{gnatmetric} sums the values of the line metrics for all the
16967 files being processed and then generates the cumulative results. The tool
16968 also computes for all the files being processed the average number of code
16971 You can use the following switches to select the specific line metrics
16972 to be computed and reported.
16975 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
16978 @cindex @option{--no-lines@var{x}}
16981 @item ^--lines-all^/LINE_COUNT_METRICS=ALL_ON^
16982 Report all the line metrics
16984 @item ^--no-lines-all^/LINE_COUNT_METRICS=ALL_OFF^
16985 Do not report any of line metrics
16987 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES_ON^
16988 Report the number of all lines
16990 @item ^--no-lines^/LINE_COUNT_METRICS=ALL_LINES_OFF^
16991 Do not report the number of all lines
16993 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES_ON^
16994 Report the number of code lines
16996 @item ^--no-lines-code^/LINE_COUNT_METRICS=CODE_LINES_OFF^
16997 Do not report the number of code lines
16999 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_ON^
17000 Report the number of comment lines
17002 @item ^--no-lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_OFF^
17003 Do not report the number of comment lines
17005 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_ON^
17006 Report the number of code lines containing
17007 end-of-line comments
17009 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_OFF^
17010 Do not report the number of code lines containing
17011 end-of-line comments
17013 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_ON^
17014 Report the comment percentage in the program text
17016 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_OFF^
17017 Do not report the comment percentage in the program text
17019 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_ON^
17020 Report the number of blank lines
17022 @item ^--no-lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_OFF^
17023 Do not report the number of blank lines
17025 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_ON^
17026 Report the average number of code lines in subprogram bodies, task bodies,
17027 entry bodies and statement sequences in package bodies. The metric is computed
17028 and reported for the whole set of processed Ada sources only.
17030 @item ^--no-lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_OFF^
17031 Do not report the average number of code lines in subprogram bodies,
17032 task bodies, entry bodies and statement sequences in package bodies.
17036 @node Syntax Metrics Control
17037 @subsubsection Syntax Metrics Control
17038 @cindex Syntax metrics control in @command{gnatmetric}
17041 @command{gnatmetric} computes various syntactic metrics for the
17042 outermost unit and for each eligible local unit:
17045 @item LSLOC (``Logical Source Lines Of Code'')
17046 The total number of declarations and the total number of statements
17048 @item Maximal static nesting level of inner program units
17050 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17051 package, a task unit, a protected unit, a
17052 protected entry, a generic unit, or an explicitly declared subprogram other
17053 than an enumeration literal.''
17055 @item Maximal nesting level of composite syntactic constructs
17056 This corresponds to the notion of the
17057 maximum nesting level in the GNAT built-in style checks
17058 (@pxref{Style Checking})
17062 For the outermost unit in the file, @command{gnatmetric} additionally computes
17063 the following metrics:
17066 @item Public subprograms
17067 This metric is computed for package specs. It is the
17068 number of subprograms and generic subprograms declared in the visible
17069 part (including the visible part of nested packages, protected objects, and
17072 @item All subprograms
17073 This metric is computed for bodies and subunits. The
17074 metric is equal to a total number of subprogram bodies in the compilation
17076 Neither generic instantiations nor renamings-as-a-body nor body stubs
17077 are counted. Any subprogram body is counted, independently of its nesting
17078 level and enclosing constructs. Generic bodies and bodies of protected
17079 subprograms are counted in the same way as ``usual'' subprogram bodies.
17082 This metric is computed for package specs and
17083 generic package declarations. It is the total number of types
17084 that can be referenced from outside this compilation unit, plus the
17085 number of types from all the visible parts of all the visible generic
17086 packages. Generic formal types are not counted. Only types, not subtypes,
17090 Along with the total number of public types, the following
17091 types are counted and reported separately:
17098 Root tagged types (abstract, non-abstract, private, non-private). Type
17099 extensions are @emph{not} counted
17102 Private types (including private extensions)
17113 This metric is computed for any compilation unit. It is equal to the total
17114 number of the declarations of different types given in the compilation unit.
17115 The private and the corresponding full type declaration are counted as one
17116 type declaration. Incomplete type declarations and generic formal types
17118 No distinction is made among different kinds of types (abstract,
17119 private etc.); the total number of types is computed and reported.
17124 By default, all the syntax metrics are computed and reported. You can use the
17125 following switches to select specific syntax metrics.
17129 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17132 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17135 @item ^--syntax-all^/SYNTAX_METRICS=ALL_ON^
17136 Report all the syntax metrics
17138 @item ^--no-syntax-all^/ALL_OFF^
17139 Do not report any of syntax metrics
17141 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS_ON^
17142 Report the total number of declarations
17144 @item ^--no-declarations^/SYNTAX_METRICS=DECLARATIONS_OFF^
17145 Do not report the total number of declarations
17147 @item ^--statements^/SYNTAX_METRICS=STATEMENTS_ON^
17148 Report the total number of statements
17150 @item ^--no-statements^/SYNTAX_METRICS=STATEMENTS_OFF^
17151 Do not report the total number of statements
17153 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_ON^
17154 Report the number of public subprograms in a compilation unit
17156 @item ^--no-public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_OFF^
17157 Do not report the number of public subprograms in a compilation unit
17159 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_ON^
17160 Report the number of all the subprograms in a compilation unit
17162 @item ^--no-all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_OFF^
17163 Do not report the number of all the subprograms in a compilation unit
17165 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES_ON^
17166 Report the number of public types in a compilation unit
17168 @item ^--no-public-types^/SYNTAX_METRICS=PUBLIC_TYPES_OFF^
17169 Do not report the number of public types in a compilation unit
17171 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES_ON^
17172 Report the number of all the types in a compilation unit
17174 @item ^--no-all-types^/SYNTAX_METRICS=ALL_TYPES_OFF^
17175 Do not report the number of all the types in a compilation unit
17177 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_ON^
17178 Report the maximal program unit nesting level
17180 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17181 Do not report the maximal program unit nesting level
17183 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_ON^
17184 Report the maximal construct nesting level
17186 @item ^--no-construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_OFF^
17187 Do not report the maximal construct nesting level
17191 @node Complexity Metrics Control
17192 @subsubsection Complexity Metrics Control
17193 @cindex Complexity metrics control in @command{gnatmetric}
17196 For a program unit that is an executable body (a subprogram body (including
17197 generic bodies), task body, entry body or a package body containing
17198 its own statement sequence) @command{gnatmetric} computes the following
17199 complexity metrics:
17203 McCabe cyclomatic complexity;
17206 McCabe essential complexity;
17209 maximal loop nesting level
17214 The McCabe complexity metrics are defined
17215 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17217 According to McCabe, both control statements and short-circuit control forms
17218 should be taken into account when computing cyclomatic complexity. For each
17219 body, we compute three metric values:
17223 the complexity introduced by control
17224 statements only, without taking into account short-circuit forms,
17227 the complexity introduced by short-circuit control forms only, and
17231 cyclomatic complexity, which is the sum of these two values.
17235 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17236 the code in the exception handlers and in all the nested program units.
17238 By default, all the complexity metrics are computed and reported.
17239 For more fine-grained control you can use
17240 the following switches:
17243 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17246 @cindex @option{--no-complexity@var{x}}
17249 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL_ON^
17250 Report all the complexity metrics
17252 @item ^--no-complexity-all^/COMPLEXITY_METRICS=ALL_OFF^
17253 Do not report any of complexity metrics
17255 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_ON^
17256 Report the McCabe Cyclomatic Complexity
17258 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_OFF^
17259 Do not report the McCabe Cyclomatic Complexity
17261 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_ON^
17262 Report the Essential Complexity
17264 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_OFF^
17265 Do not report the Essential Complexity
17267 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17268 Report maximal loop nesting level
17270 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_OFF^
17271 Do not report maximal loop nesting level
17273 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_ON^
17274 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17275 task bodies, entry bodies and statement sequences in package bodies.
17276 The metric is computed and reported for whole set of processed Ada sources
17279 @item ^--no-complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_OFF^
17280 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17281 bodies, task bodies, entry bodies and statement sequences in package bodies
17283 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17284 @item ^-ne^/NO_EXITS_AS_GOTOS^
17285 Do not consider @code{exit} statements as @code{goto}s when
17286 computing Essential Complexity
17291 @node Object-Oriented Metrics Control
17292 @subsubsection Object-Oriented Metrics Control
17293 @cindex Object-Oriented metrics control in @command{gnatmetric}
17296 @cindex Coupling metrics (in in @command{gnatmetric})
17297 Coupling metrics are object-oriented metrics that measure the
17298 dependencies between a given class (or a group of classes) and the
17299 ``external world'' (that is, the other classes in the program). In this
17300 subsection the term ``class'' is used in its
17301 traditional object-oriented programming sense
17302 (an instantiable module that contains data and/or method members).
17303 A @emph{category} (of classes)
17304 is a group of closely related classes that are reused and/or
17307 A class @code{K}'s @emph{efferent coupling} is the number of classes
17308 that @code{K} depends upon.
17309 A category's efferent coupling is the number of classes outside the
17310 category that the classes inside the category depend upon.
17312 A class @code{K}'s @emph{afferent coupling} is the number of classes
17313 that depend upon @code{K}.
17314 A category's afferent coupling is the number of classes outside the
17315 category that depend on classes belonging to the category.
17317 Ada's implementation of the object-oriented paradigm does not use the
17318 traditional class notion, so the definition of the coupling
17319 metrics for Ada maps the class and class category notions
17320 onto Ada constructs.
17322 For the coupling metrics, several kinds of modules -- a library package,
17323 a library generic package, and a library generic package instantiation --
17324 that define a tagged type or an interface type are
17325 considered to be a class. A category consists of a library package (or
17326 a library generic package) that defines a tagged or an interface type,
17327 together with all its descendant (generic) packages that define tagged
17328 or interface types. For any package counted as a class,
17329 its body (if any) is considered
17330 together with its spec when counting the dependencies. For dependencies
17331 between classes, the Ada semantic dependencies are considered.
17332 For coupling metrics, only dependencies on units that are considered as
17333 classes, are considered.
17335 When computing coupling metrics, @command{gnatmetric} counts only
17336 dependencies between units that are arguments of the gnatmetric call.
17337 Coupling metrics are program-wide (or project-wide) metrics, so to
17338 get a valid result, you should call @command{gnatmetric} for
17339 the whole set of sources that make up your program. It can be done
17340 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17341 option (see See @ref{The GNAT Driver and Project Files} for details.
17343 By default, all the coupling metrics are disabled. You can use the following
17344 switches to specify the coupling metrics to be computed and reported:
17349 @cindex @option{--package@var{x}} (@command{gnatmetric})
17350 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17351 @cindex @option{--category@var{x}} (@command{gnatmetric})
17352 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17356 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17359 @item ^--coupling-all^/COUPLING_METRICS=ALL_ON^
17360 Report all the coupling metrics
17362 @item ^--no-coupling-all^/COUPLING_METRICS=ALL_OFF^
17363 Do not report any of metrics
17365 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_ON^
17366 Report package efferent coupling
17368 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_OFF^
17369 Do not report package efferent coupling
17371 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_ON^
17372 Report package afferent coupling
17374 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_OFF^
17375 Do not report package afferent coupling
17377 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_ON^
17378 Report category efferent coupling
17380 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_OFF^
17381 Do not report category efferent coupling
17383 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_ON^
17384 Report category afferent coupling
17386 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_OFF^
17387 Do not report category afferent coupling
17391 @node Other gnatmetric Switches
17392 @subsection Other @code{gnatmetric} Switches
17395 Additional @command{gnatmetric} switches are as follows:
17398 @item ^-files @var{filename}^/FILES=@var{filename}^
17399 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17400 Take the argument source files from the specified file. This file should be an
17401 ordinary text file containing file names separated by spaces or
17402 line breaks. You can use this switch more then once in the same call to
17403 @command{gnatmetric}. You also can combine this switch with
17404 an explicit list of files.
17406 @item ^-v^/VERBOSE^
17407 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17409 @command{gnatmetric} generates version information and then
17410 a trace of sources being processed.
17412 @item ^-dv^/DEBUG_OUTPUT^
17413 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17415 @command{gnatmetric} generates various messages useful to understand what
17416 happens during the metrics computation
17419 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17423 @node Generate project-wide metrics
17424 @subsection Generate project-wide metrics
17426 In order to compute metrics on all units of a given project, you can use
17427 the @command{gnat} driver along with the @option{-P} option:
17433 If the project @code{proj} depends upon other projects, you can compute
17434 the metrics on the project closure using the @option{-U} option:
17436 gnat metric -Pproj -U
17440 Finally, if not all the units are relevant to a particular main
17441 program in the project closure, you can generate metrics for the set
17442 of units needed to create a given main program (unit closure) using
17443 the @option{-U} option followed by the name of the main unit:
17445 gnat metric -Pproj -U main
17449 @c ***********************************
17450 @node File Name Krunching Using gnatkr
17451 @chapter File Name Krunching Using @code{gnatkr}
17455 This chapter discusses the method used by the compiler to shorten
17456 the default file names chosen for Ada units so that they do not
17457 exceed the maximum length permitted. It also describes the
17458 @code{gnatkr} utility that can be used to determine the result of
17459 applying this shortening.
17463 * Krunching Method::
17464 * Examples of gnatkr Usage::
17468 @section About @code{gnatkr}
17471 The default file naming rule in GNAT
17472 is that the file name must be derived from
17473 the unit name. The exact default rule is as follows:
17476 Take the unit name and replace all dots by hyphens.
17478 If such a replacement occurs in the
17479 second character position of a name, and the first character is
17480 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17481 then replace the dot by the character
17482 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17483 instead of a minus.
17485 The reason for this exception is to avoid clashes
17486 with the standard names for children of System, Ada, Interfaces,
17487 and GNAT, which use the prefixes
17488 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17491 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17492 switch of the compiler activates a ``krunching''
17493 circuit that limits file names to nn characters (where nn is a decimal
17494 integer). For example, using OpenVMS,
17495 where the maximum file name length is
17496 39, the value of nn is usually set to 39, but if you want to generate
17497 a set of files that would be usable if ported to a system with some
17498 different maximum file length, then a different value can be specified.
17499 The default value of 39 for OpenVMS need not be specified.
17501 The @code{gnatkr} utility can be used to determine the krunched name for
17502 a given file, when krunched to a specified maximum length.
17505 @section Using @code{gnatkr}
17508 The @code{gnatkr} command has the form
17512 $ gnatkr @var{name} @ovar{length}
17518 $ gnatkr @var{name} /COUNT=nn
17523 @var{name} is the uncrunched file name, derived from the name of the unit
17524 in the standard manner described in the previous section (i.e., in particular
17525 all dots are replaced by hyphens). The file name may or may not have an
17526 extension (defined as a suffix of the form period followed by arbitrary
17527 characters other than period). If an extension is present then it will
17528 be preserved in the output. For example, when krunching @file{hellofile.ads}
17529 to eight characters, the result will be hellofil.ads.
17531 Note: for compatibility with previous versions of @code{gnatkr} dots may
17532 appear in the name instead of hyphens, but the last dot will always be
17533 taken as the start of an extension. So if @code{gnatkr} is given an argument
17534 such as @file{Hello.World.adb} it will be treated exactly as if the first
17535 period had been a hyphen, and for example krunching to eight characters
17536 gives the result @file{hellworl.adb}.
17538 Note that the result is always all lower case (except on OpenVMS where it is
17539 all upper case). Characters of the other case are folded as required.
17541 @var{length} represents the length of the krunched name. The default
17542 when no argument is given is ^8^39^ characters. A length of zero stands for
17543 unlimited, in other words do not chop except for system files where the
17544 implied crunching length is always eight characters.
17547 The output is the krunched name. The output has an extension only if the
17548 original argument was a file name with an extension.
17550 @node Krunching Method
17551 @section Krunching Method
17554 The initial file name is determined by the name of the unit that the file
17555 contains. The name is formed by taking the full expanded name of the
17556 unit and replacing the separating dots with hyphens and
17557 using ^lowercase^uppercase^
17558 for all letters, except that a hyphen in the second character position is
17559 replaced by a ^tilde^dollar sign^ if the first character is
17560 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
17561 The extension is @code{.ads} for a
17562 spec and @code{.adb} for a body.
17563 Krunching does not affect the extension, but the file name is shortened to
17564 the specified length by following these rules:
17568 The name is divided into segments separated by hyphens, tildes or
17569 underscores and all hyphens, tildes, and underscores are
17570 eliminated. If this leaves the name short enough, we are done.
17573 If the name is too long, the longest segment is located (left-most
17574 if there are two of equal length), and shortened by dropping
17575 its last character. This is repeated until the name is short enough.
17577 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
17578 to fit the name into 8 characters as required by some operating systems.
17581 our-strings-wide_fixed 22
17582 our strings wide fixed 19
17583 our string wide fixed 18
17584 our strin wide fixed 17
17585 our stri wide fixed 16
17586 our stri wide fixe 15
17587 our str wide fixe 14
17588 our str wid fixe 13
17594 Final file name: oustwifi.adb
17598 The file names for all predefined units are always krunched to eight
17599 characters. The krunching of these predefined units uses the following
17600 special prefix replacements:
17604 replaced by @file{^a^A^-}
17607 replaced by @file{^g^G^-}
17610 replaced by @file{^i^I^-}
17613 replaced by @file{^s^S^-}
17616 These system files have a hyphen in the second character position. That
17617 is why normal user files replace such a character with a
17618 ^tilde^dollar sign^, to
17619 avoid confusion with system file names.
17621 As an example of this special rule, consider
17622 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
17625 ada-strings-wide_fixed 22
17626 a- strings wide fixed 18
17627 a- string wide fixed 17
17628 a- strin wide fixed 16
17629 a- stri wide fixed 15
17630 a- stri wide fixe 14
17631 a- str wide fixe 13
17637 Final file name: a-stwifi.adb
17641 Of course no file shortening algorithm can guarantee uniqueness over all
17642 possible unit names, and if file name krunching is used then it is your
17643 responsibility to ensure that no name clashes occur. The utility
17644 program @code{gnatkr} is supplied for conveniently determining the
17645 krunched name of a file.
17647 @node Examples of gnatkr Usage
17648 @section Examples of @code{gnatkr} Usage
17655 $ gnatkr very_long_unit_name.ads --> velounna.ads
17656 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
17657 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
17658 $ gnatkr grandparent-parent-child --> grparchi
17660 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
17661 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
17664 @node Preprocessing Using gnatprep
17665 @chapter Preprocessing Using @code{gnatprep}
17669 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
17671 Although designed for use with GNAT, @code{gnatprep} does not depend on any
17672 special GNAT features.
17673 For further discussion of conditional compilation in general, see
17674 @ref{Conditional Compilation}.
17677 * Preprocessing Symbols::
17679 * Switches for gnatprep::
17680 * Form of Definitions File::
17681 * Form of Input Text for gnatprep::
17684 @node Preprocessing Symbols
17685 @section Preprocessing Symbols
17688 Preprocessing symbols are defined in definition files and referred to in
17689 sources to be preprocessed. A Preprocessing symbol is an identifier, following
17690 normal Ada (case-insensitive) rules for its syntax, with the restriction that
17691 all characters need to be in the ASCII set (no accented letters).
17693 @node Using gnatprep
17694 @section Using @code{gnatprep}
17697 To call @code{gnatprep} use
17700 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
17707 is an optional sequence of switches as described in the next section.
17710 is the full name of the input file, which is an Ada source
17711 file containing preprocessor directives.
17714 is the full name of the output file, which is an Ada source
17715 in standard Ada form. When used with GNAT, this file name will
17716 normally have an ads or adb suffix.
17719 is the full name of a text file containing definitions of
17720 preprocessing symbols to be referenced by the preprocessor. This argument is
17721 optional, and can be replaced by the use of the @option{-D} switch.
17725 @node Switches for gnatprep
17726 @section Switches for @code{gnatprep}
17731 @item ^-b^/BLANK_LINES^
17732 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
17733 Causes both preprocessor lines and the lines deleted by
17734 preprocessing to be replaced by blank lines in the output source file,
17735 preserving line numbers in the output file.
17737 @item ^-c^/COMMENTS^
17738 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
17739 Causes both preprocessor lines and the lines deleted
17740 by preprocessing to be retained in the output source as comments marked
17741 with the special string @code{"--! "}. This option will result in line numbers
17742 being preserved in the output file.
17744 @item ^-C^/REPLACE_IN_COMMENTS^
17745 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
17746 Causes comments to be scanned. Normally comments are ignored by gnatprep.
17747 If this option is specified, then comments are scanned and any $symbol
17748 substitutions performed as in program text. This is particularly useful
17749 when structured comments are used (e.g., when writing programs in the
17750 SPARK dialect of Ada). Note that this switch is not available when
17751 doing integrated preprocessing (it would be useless in this context
17752 since comments are ignored by the compiler in any case).
17754 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
17755 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
17756 Defines a new preprocessing symbol, associated with value. If no value is given
17757 on the command line, then symbol is considered to be @code{True}. This switch
17758 can be used in place of a definition file.
17762 @cindex @option{/REMOVE} (@command{gnatprep})
17763 This is the default setting which causes lines deleted by preprocessing
17764 to be entirely removed from the output file.
17767 @item ^-r^/REFERENCE^
17768 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
17769 Causes a @code{Source_Reference} pragma to be generated that
17770 references the original input file, so that error messages will use
17771 the file name of this original file. The use of this switch implies
17772 that preprocessor lines are not to be removed from the file, so its
17773 use will force @option{^-b^/BLANK_LINES^} mode if
17774 @option{^-c^/COMMENTS^}
17775 has not been specified explicitly.
17777 Note that if the file to be preprocessed contains multiple units, then
17778 it will be necessary to @code{gnatchop} the output file from
17779 @code{gnatprep}. If a @code{Source_Reference} pragma is present
17780 in the preprocessed file, it will be respected by
17781 @code{gnatchop ^-r^/REFERENCE^}
17782 so that the final chopped files will correctly refer to the original
17783 input source file for @code{gnatprep}.
17785 @item ^-s^/SYMBOLS^
17786 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
17787 Causes a sorted list of symbol names and values to be
17788 listed on the standard output file.
17790 @item ^-u^/UNDEFINED^
17791 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
17792 Causes undefined symbols to be treated as having the value FALSE in the context
17793 of a preprocessor test. In the absence of this option, an undefined symbol in
17794 a @code{#if} or @code{#elsif} test will be treated as an error.
17800 Note: if neither @option{-b} nor @option{-c} is present,
17801 then preprocessor lines and
17802 deleted lines are completely removed from the output, unless -r is
17803 specified, in which case -b is assumed.
17806 @node Form of Definitions File
17807 @section Form of Definitions File
17810 The definitions file contains lines of the form
17817 where symbol is a preprocessing symbol, and value is one of the following:
17821 Empty, corresponding to a null substitution
17823 A string literal using normal Ada syntax
17825 Any sequence of characters from the set
17826 (letters, digits, period, underline).
17830 Comment lines may also appear in the definitions file, starting with
17831 the usual @code{--},
17832 and comments may be added to the definitions lines.
17834 @node Form of Input Text for gnatprep
17835 @section Form of Input Text for @code{gnatprep}
17838 The input text may contain preprocessor conditional inclusion lines,
17839 as well as general symbol substitution sequences.
17841 The preprocessor conditional inclusion commands have the form
17846 #if @i{expression} @r{[}then@r{]}
17848 #elsif @i{expression} @r{[}then@r{]}
17850 #elsif @i{expression} @r{[}then@r{]}
17861 In this example, @i{expression} is defined by the following grammar:
17863 @i{expression} ::= <symbol>
17864 @i{expression} ::= <symbol> = "<value>"
17865 @i{expression} ::= <symbol> = <symbol>
17866 @i{expression} ::= <symbol> 'Defined
17867 @i{expression} ::= not @i{expression}
17868 @i{expression} ::= @i{expression} and @i{expression}
17869 @i{expression} ::= @i{expression} or @i{expression}
17870 @i{expression} ::= @i{expression} and then @i{expression}
17871 @i{expression} ::= @i{expression} or else @i{expression}
17872 @i{expression} ::= ( @i{expression} )
17875 The following restriction exists: it is not allowed to have "and" or "or"
17876 following "not" in the same expression without parentheses. For example, this
17883 This should be one of the following:
17891 For the first test (@i{expression} ::= <symbol>) the symbol must have
17892 either the value true or false, that is to say the right-hand of the
17893 symbol definition must be one of the (case-insensitive) literals
17894 @code{True} or @code{False}. If the value is true, then the
17895 corresponding lines are included, and if the value is false, they are
17898 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
17899 the symbol has been defined in the definition file or by a @option{-D}
17900 switch on the command line. Otherwise, the test is false.
17902 The equality tests are case insensitive, as are all the preprocessor lines.
17904 If the symbol referenced is not defined in the symbol definitions file,
17905 then the effect depends on whether or not switch @option{-u}
17906 is specified. If so, then the symbol is treated as if it had the value
17907 false and the test fails. If this switch is not specified, then
17908 it is an error to reference an undefined symbol. It is also an error to
17909 reference a symbol that is defined with a value other than @code{True}
17912 The use of the @code{not} operator inverts the sense of this logical test.
17913 The @code{not} operator cannot be combined with the @code{or} or @code{and}
17914 operators, without parentheses. For example, "if not X or Y then" is not
17915 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
17917 The @code{then} keyword is optional as shown
17919 The @code{#} must be the first non-blank character on a line, but
17920 otherwise the format is free form. Spaces or tabs may appear between
17921 the @code{#} and the keyword. The keywords and the symbols are case
17922 insensitive as in normal Ada code. Comments may be used on a
17923 preprocessor line, but other than that, no other tokens may appear on a
17924 preprocessor line. Any number of @code{elsif} clauses can be present,
17925 including none at all. The @code{else} is optional, as in Ada.
17927 The @code{#} marking the start of a preprocessor line must be the first
17928 non-blank character on the line, i.e., it must be preceded only by
17929 spaces or horizontal tabs.
17931 Symbol substitution outside of preprocessor lines is obtained by using
17939 anywhere within a source line, except in a comment or within a
17940 string literal. The identifier
17941 following the @code{$} must match one of the symbols defined in the symbol
17942 definition file, and the result is to substitute the value of the
17943 symbol in place of @code{$symbol} in the output file.
17945 Note that although the substitution of strings within a string literal
17946 is not possible, it is possible to have a symbol whose defined value is
17947 a string literal. So instead of setting XYZ to @code{hello} and writing:
17950 Header : String := "$XYZ";
17954 you should set XYZ to @code{"hello"} and write:
17957 Header : String := $XYZ;
17961 and then the substitution will occur as desired.
17964 @node The GNAT Run-Time Library Builder gnatlbr
17965 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
17967 @cindex Library builder
17970 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
17971 supplied configuration pragmas.
17974 * Running gnatlbr::
17975 * Switches for gnatlbr::
17976 * Examples of gnatlbr Usage::
17979 @node Running gnatlbr
17980 @section Running @code{gnatlbr}
17983 The @code{gnatlbr} command has the form
17986 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
17989 @node Switches for gnatlbr
17990 @section Switches for @code{gnatlbr}
17993 @code{gnatlbr} recognizes the following switches:
17997 @item /CREATE=directory
17998 @cindex @code{/CREATE} (@code{gnatlbr})
17999 Create the new run-time library in the specified directory.
18001 @item /SET=directory
18002 @cindex @code{/SET} (@code{gnatlbr})
18003 Make the library in the specified directory the current run-time library.
18005 @item /DELETE=directory
18006 @cindex @code{/DELETE} (@code{gnatlbr})
18007 Delete the run-time library in the specified directory.
18010 @cindex @code{/CONFIG} (@code{gnatlbr})
18011 With /CREATE: Use the configuration pragmas in the specified file when
18012 building the library.
18014 With /SET: Use the configuration pragmas in the specified file when
18019 @node Examples of gnatlbr Usage
18020 @section Example of @code{gnatlbr} Usage
18023 Contents of VAXFLOAT.ADC:
18024 pragma Float_Representation (VAX_Float);
18026 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18028 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18033 @node The GNAT Library Browser gnatls
18034 @chapter The GNAT Library Browser @code{gnatls}
18036 @cindex Library browser
18039 @code{gnatls} is a tool that outputs information about compiled
18040 units. It gives the relationship between objects, unit names and source
18041 files. It can also be used to check the source dependencies of a unit
18042 as well as various characteristics.
18044 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18045 driver (see @ref{The GNAT Driver and Project Files}).
18049 * Switches for gnatls::
18050 * Examples of gnatls Usage::
18053 @node Running gnatls
18054 @section Running @code{gnatls}
18057 The @code{gnatls} command has the form
18060 $ gnatls switches @var{object_or_ali_file}
18064 The main argument is the list of object or @file{ali} files
18065 (@pxref{The Ada Library Information Files})
18066 for which information is requested.
18068 In normal mode, without additional option, @code{gnatls} produces a
18069 four-column listing. Each line represents information for a specific
18070 object. The first column gives the full path of the object, the second
18071 column gives the name of the principal unit in this object, the third
18072 column gives the status of the source and the fourth column gives the
18073 full path of the source representing this unit.
18074 Here is a simple example of use:
18078 ^./^[]^demo1.o demo1 DIF demo1.adb
18079 ^./^[]^demo2.o demo2 OK demo2.adb
18080 ^./^[]^hello.o h1 OK hello.adb
18081 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18082 ^./^[]^instr.o instr OK instr.adb
18083 ^./^[]^tef.o tef DIF tef.adb
18084 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18085 ^./^[]^tgef.o tgef DIF tgef.adb
18089 The first line can be interpreted as follows: the main unit which is
18091 object file @file{demo1.o} is demo1, whose main source is in
18092 @file{demo1.adb}. Furthermore, the version of the source used for the
18093 compilation of demo1 has been modified (DIF). Each source file has a status
18094 qualifier which can be:
18097 @item OK (unchanged)
18098 The version of the source file used for the compilation of the
18099 specified unit corresponds exactly to the actual source file.
18101 @item MOK (slightly modified)
18102 The version of the source file used for the compilation of the
18103 specified unit differs from the actual source file but not enough to
18104 require recompilation. If you use gnatmake with the qualifier
18105 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18106 MOK will not be recompiled.
18108 @item DIF (modified)
18109 No version of the source found on the path corresponds to the source
18110 used to build this object.
18112 @item ??? (file not found)
18113 No source file was found for this unit.
18115 @item HID (hidden, unchanged version not first on PATH)
18116 The version of the source that corresponds exactly to the source used
18117 for compilation has been found on the path but it is hidden by another
18118 version of the same source that has been modified.
18122 @node Switches for gnatls
18123 @section Switches for @code{gnatls}
18126 @code{gnatls} recognizes the following switches:
18130 @cindex @option{--version} @command{gnatls}
18131 Display Copyright and version, then exit disregarding all other options.
18134 @cindex @option{--help} @command{gnatls}
18135 If @option{--version} was not used, display usage, then exit disregarding
18138 @item ^-a^/ALL_UNITS^
18139 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18140 Consider all units, including those of the predefined Ada library.
18141 Especially useful with @option{^-d^/DEPENDENCIES^}.
18143 @item ^-d^/DEPENDENCIES^
18144 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18145 List sources from which specified units depend on.
18147 @item ^-h^/OUTPUT=OPTIONS^
18148 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18149 Output the list of options.
18151 @item ^-o^/OUTPUT=OBJECTS^
18152 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18153 Only output information about object files.
18155 @item ^-s^/OUTPUT=SOURCES^
18156 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18157 Only output information about source files.
18159 @item ^-u^/OUTPUT=UNITS^
18160 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18161 Only output information about compilation units.
18163 @item ^-files^/FILES^=@var{file}
18164 @cindex @option{^-files^/FILES^} (@code{gnatls})
18165 Take as arguments the files listed in text file @var{file}.
18166 Text file @var{file} may contain empty lines that are ignored.
18167 Each nonempty line should contain the name of an existing file.
18168 Several such switches may be specified simultaneously.
18170 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18171 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18172 @itemx ^-I^/SEARCH=^@var{dir}
18173 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18175 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18176 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18177 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18178 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18179 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18180 flags (@pxref{Switches for gnatmake}).
18182 @item --RTS=@var{rts-path}
18183 @cindex @option{--RTS} (@code{gnatls})
18184 Specifies the default location of the runtime library. Same meaning as the
18185 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18187 @item ^-v^/OUTPUT=VERBOSE^
18188 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18189 Verbose mode. Output the complete source, object and project paths. Do not use
18190 the default column layout but instead use long format giving as much as
18191 information possible on each requested units, including special
18192 characteristics such as:
18195 @item Preelaborable
18196 The unit is preelaborable in the Ada sense.
18199 No elaboration code has been produced by the compiler for this unit.
18202 The unit is pure in the Ada sense.
18204 @item Elaborate_Body
18205 The unit contains a pragma Elaborate_Body.
18208 The unit contains a pragma Remote_Types.
18210 @item Shared_Passive
18211 The unit contains a pragma Shared_Passive.
18214 This unit is part of the predefined environment and cannot be modified
18217 @item Remote_Call_Interface
18218 The unit contains a pragma Remote_Call_Interface.
18224 @node Examples of gnatls Usage
18225 @section Example of @code{gnatls} Usage
18229 Example of using the verbose switch. Note how the source and
18230 object paths are affected by the -I switch.
18233 $ gnatls -v -I.. demo1.o
18235 GNATLS 5.03w (20041123-34)
18236 Copyright 1997-2004 Free Software Foundation, Inc.
18238 Source Search Path:
18239 <Current_Directory>
18241 /home/comar/local/adainclude/
18243 Object Search Path:
18244 <Current_Directory>
18246 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18248 Project Search Path:
18249 <Current_Directory>
18250 /home/comar/local/lib/gnat/
18255 Kind => subprogram body
18256 Flags => No_Elab_Code
18257 Source => demo1.adb modified
18261 The following is an example of use of the dependency list.
18262 Note the use of the -s switch
18263 which gives a straight list of source files. This can be useful for
18264 building specialized scripts.
18267 $ gnatls -d demo2.o
18268 ./demo2.o demo2 OK demo2.adb
18274 $ gnatls -d -s -a demo1.o
18276 /home/comar/local/adainclude/ada.ads
18277 /home/comar/local/adainclude/a-finali.ads
18278 /home/comar/local/adainclude/a-filico.ads
18279 /home/comar/local/adainclude/a-stream.ads
18280 /home/comar/local/adainclude/a-tags.ads
18283 /home/comar/local/adainclude/gnat.ads
18284 /home/comar/local/adainclude/g-io.ads
18286 /home/comar/local/adainclude/system.ads
18287 /home/comar/local/adainclude/s-exctab.ads
18288 /home/comar/local/adainclude/s-finimp.ads
18289 /home/comar/local/adainclude/s-finroo.ads
18290 /home/comar/local/adainclude/s-secsta.ads
18291 /home/comar/local/adainclude/s-stalib.ads
18292 /home/comar/local/adainclude/s-stoele.ads
18293 /home/comar/local/adainclude/s-stratt.ads
18294 /home/comar/local/adainclude/s-tasoli.ads
18295 /home/comar/local/adainclude/s-unstyp.ads
18296 /home/comar/local/adainclude/unchconv.ads
18302 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18304 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18305 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18306 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18307 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18308 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18312 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18313 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18315 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18316 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18317 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18318 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18319 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18320 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18321 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18322 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18323 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18324 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18325 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18329 @node Cleaning Up Using gnatclean
18330 @chapter Cleaning Up Using @code{gnatclean}
18332 @cindex Cleaning tool
18335 @code{gnatclean} is a tool that allows the deletion of files produced by the
18336 compiler, binder and linker, including ALI files, object files, tree files,
18337 expanded source files, library files, interface copy source files, binder
18338 generated files and executable files.
18341 * Running gnatclean::
18342 * Switches for gnatclean::
18343 @c * Examples of gnatclean Usage::
18346 @node Running gnatclean
18347 @section Running @code{gnatclean}
18350 The @code{gnatclean} command has the form:
18353 $ gnatclean switches @var{names}
18357 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18358 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18359 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18362 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18363 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18364 the linker. In informative-only mode, specified by switch
18365 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18366 normal mode is listed, but no file is actually deleted.
18368 @node Switches for gnatclean
18369 @section Switches for @code{gnatclean}
18372 @code{gnatclean} recognizes the following switches:
18376 @cindex @option{--version} @command{gnatclean}
18377 Display Copyright and version, then exit disregarding all other options.
18380 @cindex @option{--help} @command{gnatclean}
18381 If @option{--version} was not used, display usage, then exit disregarding
18384 @item ^-c^/COMPILER_FILES_ONLY^
18385 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18386 Only attempt to delete the files produced by the compiler, not those produced
18387 by the binder or the linker. The files that are not to be deleted are library
18388 files, interface copy files, binder generated files and executable files.
18390 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18391 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18392 Indicate that ALI and object files should normally be found in directory
18395 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18396 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18397 When using project files, if some errors or warnings are detected during
18398 parsing and verbose mode is not in effect (no use of switch
18399 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18400 file, rather than its simple file name.
18403 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18404 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18406 @item ^-n^/NODELETE^
18407 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18408 Informative-only mode. Do not delete any files. Output the list of the files
18409 that would have been deleted if this switch was not specified.
18411 @item ^-P^/PROJECT_FILE=^@var{project}
18412 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18413 Use project file @var{project}. Only one such switch can be used.
18414 When cleaning a project file, the files produced by the compilation of the
18415 immediate sources or inherited sources of the project files are to be
18416 deleted. This is not depending on the presence or not of executable names
18417 on the command line.
18420 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18421 Quiet output. If there are no errors, do not output anything, except in
18422 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18423 (switch ^-n^/NODELETE^).
18425 @item ^-r^/RECURSIVE^
18426 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18427 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18428 clean all imported and extended project files, recursively. If this switch
18429 is not specified, only the files related to the main project file are to be
18430 deleted. This switch has no effect if no project file is specified.
18432 @item ^-v^/VERBOSE^
18433 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18436 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18437 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18438 Indicates the verbosity of the parsing of GNAT project files.
18439 @xref{Switches Related to Project Files}.
18441 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18442 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18443 Indicates that external variable @var{name} has the value @var{value}.
18444 The Project Manager will use this value for occurrences of
18445 @code{external(name)} when parsing the project file.
18446 @xref{Switches Related to Project Files}.
18448 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18449 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18450 When searching for ALI and object files, look in directory
18453 @item ^-I^/SEARCH=^@var{dir}
18454 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18455 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18457 @item ^-I-^/NOCURRENT_DIRECTORY^
18458 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18459 @cindex Source files, suppressing search
18460 Do not look for ALI or object files in the directory
18461 where @code{gnatclean} was invoked.
18465 @c @node Examples of gnatclean Usage
18466 @c @section Examples of @code{gnatclean} Usage
18469 @node GNAT and Libraries
18470 @chapter GNAT and Libraries
18471 @cindex Library, building, installing, using
18474 This chapter describes how to build and use libraries with GNAT, and also shows
18475 how to recompile the GNAT run-time library. You should be familiar with the
18476 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18480 * Introduction to Libraries in GNAT::
18481 * General Ada Libraries::
18482 * Stand-alone Ada Libraries::
18483 * Rebuilding the GNAT Run-Time Library::
18486 @node Introduction to Libraries in GNAT
18487 @section Introduction to Libraries in GNAT
18490 A library is, conceptually, a collection of objects which does not have its
18491 own main thread of execution, but rather provides certain services to the
18492 applications that use it. A library can be either statically linked with the
18493 application, in which case its code is directly included in the application,
18494 or, on platforms that support it, be dynamically linked, in which case
18495 its code is shared by all applications making use of this library.
18497 GNAT supports both types of libraries.
18498 In the static case, the compiled code can be provided in different ways. The
18499 simplest approach is to provide directly the set of objects resulting from
18500 compilation of the library source files. Alternatively, you can group the
18501 objects into an archive using whatever commands are provided by the operating
18502 system. For the latter case, the objects are grouped into a shared library.
18504 In the GNAT environment, a library has three types of components:
18510 @xref{The Ada Library Information Files}.
18512 Object files, an archive or a shared library.
18516 A GNAT library may expose all its source files, which is useful for
18517 documentation purposes. Alternatively, it may expose only the units needed by
18518 an external user to make use of the library. That is to say, the specs
18519 reflecting the library services along with all the units needed to compile
18520 those specs, which can include generic bodies or any body implementing an
18521 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18522 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18524 All compilation units comprising an application, including those in a library,
18525 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18526 computes the elaboration order from the @file{ALI} files and this is why they
18527 constitute a mandatory part of GNAT libraries. Except in the case of
18528 @emph{stand-alone libraries}, where a specific library elaboration routine is
18529 produced independently of the application(s) using the library.
18531 @node General Ada Libraries
18532 @section General Ada Libraries
18535 * Building a library::
18536 * Installing a library::
18537 * Using a library::
18540 @node Building a library
18541 @subsection Building a library
18544 The easiest way to build a library is to use the Project Manager,
18545 which supports a special type of project called a @emph{Library Project}
18546 (@pxref{Library Projects}).
18548 A project is considered a library project, when two project-level attributes
18549 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18550 control different aspects of library configuration, additional optional
18551 project-level attributes can be specified:
18554 This attribute controls whether the library is to be static or dynamic
18556 @item Library_Version
18557 This attribute specifies the library version; this value is used
18558 during dynamic linking of shared libraries to determine if the currently
18559 installed versions of the binaries are compatible.
18561 @item Library_Options
18563 These attributes specify additional low-level options to be used during
18564 library generation, and redefine the actual application used to generate
18569 The GNAT Project Manager takes full care of the library maintenance task,
18570 including recompilation of the source files for which objects do not exist
18571 or are not up to date, assembly of the library archive, and installation of
18572 the library (i.e., copying associated source, object and @file{ALI} files
18573 to the specified location).
18575 Here is a simple library project file:
18576 @smallexample @c ada
18578 for Source_Dirs use ("src1", "src2");
18579 for Object_Dir use "obj";
18580 for Library_Name use "mylib";
18581 for Library_Dir use "lib";
18582 for Library_Kind use "dynamic";
18587 and the compilation command to build and install the library:
18589 @smallexample @c ada
18590 $ gnatmake -Pmy_lib
18594 It is not entirely trivial to perform manually all the steps required to
18595 produce a library. We recommend that you use the GNAT Project Manager
18596 for this task. In special cases where this is not desired, the necessary
18597 steps are discussed below.
18599 There are various possibilities for compiling the units that make up the
18600 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
18601 with a conventional script. For simple libraries, it is also possible to create
18602 a dummy main program which depends upon all the packages that comprise the
18603 interface of the library. This dummy main program can then be given to
18604 @command{gnatmake}, which will ensure that all necessary objects are built.
18606 After this task is accomplished, you should follow the standard procedure
18607 of the underlying operating system to produce the static or shared library.
18609 Here is an example of such a dummy program:
18610 @smallexample @c ada
18612 with My_Lib.Service1;
18613 with My_Lib.Service2;
18614 with My_Lib.Service3;
18615 procedure My_Lib_Dummy is
18623 Here are the generic commands that will build an archive or a shared library.
18626 # compiling the library
18627 $ gnatmake -c my_lib_dummy.adb
18629 # we don't need the dummy object itself
18630 $ rm my_lib_dummy.o my_lib_dummy.ali
18632 # create an archive with the remaining objects
18633 $ ar rc libmy_lib.a *.o
18634 # some systems may require "ranlib" to be run as well
18636 # or create a shared library
18637 $ gcc -shared -o libmy_lib.so *.o
18638 # some systems may require the code to have been compiled with -fPIC
18640 # remove the object files that are now in the library
18643 # Make the ALI files read-only so that gnatmake will not try to
18644 # regenerate the objects that are in the library
18649 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
18650 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
18651 be accessed by the directive @option{-l@var{xxx}} at link time.
18653 @node Installing a library
18654 @subsection Installing a library
18655 @cindex @code{ADA_PROJECT_PATH}
18658 If you use project files, library installation is part of the library build
18659 process. Thus no further action is needed in order to make use of the
18660 libraries that are built as part of the general application build. A usable
18661 version of the library is installed in the directory specified by the
18662 @code{Library_Dir} attribute of the library project file.
18664 You may want to install a library in a context different from where the library
18665 is built. This situation arises with third party suppliers, who may want
18666 to distribute a library in binary form where the user is not expected to be
18667 able to recompile the library. The simplest option in this case is to provide
18668 a project file slightly different from the one used to build the library, by
18669 using the @code{externally_built} attribute. For instance, the project
18670 file used to build the library in the previous section can be changed into the
18671 following one when the library is installed:
18673 @smallexample @c projectfile
18675 for Source_Dirs use ("src1", "src2");
18676 for Library_Name use "mylib";
18677 for Library_Dir use "lib";
18678 for Library_Kind use "dynamic";
18679 for Externally_Built use "true";
18684 This project file assumes that the directories @file{src1},
18685 @file{src2}, and @file{lib} exist in
18686 the directory containing the project file. The @code{externally_built}
18687 attribute makes it clear to the GNAT builder that it should not attempt to
18688 recompile any of the units from this library. It allows the library provider to
18689 restrict the source set to the minimum necessary for clients to make use of the
18690 library as described in the first section of this chapter. It is the
18691 responsibility of the library provider to install the necessary sources, ALI
18692 files and libraries in the directories mentioned in the project file. For
18693 convenience, the user's library project file should be installed in a location
18694 that will be searched automatically by the GNAT
18695 builder. These are the directories referenced in the @env{ADA_PROJECT_PATH}
18696 environment variable (@pxref{Importing Projects}), and also the default GNAT
18697 library location that can be queried with @command{gnatls -v} and is usually of
18698 the form $gnat_install_root/lib/gnat.
18700 When project files are not an option, it is also possible, but not recommended,
18701 to install the library so that the sources needed to use the library are on the
18702 Ada source path and the ALI files & libraries be on the Ada Object path (see
18703 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
18704 administrator can place general-purpose libraries in the default compiler
18705 paths, by specifying the libraries' location in the configuration files
18706 @file{ada_source_path} and @file{ada_object_path}. These configuration files
18707 must be located in the GNAT installation tree at the same place as the gcc spec
18708 file. The location of the gcc spec file can be determined as follows:
18714 The configuration files mentioned above have a simple format: each line
18715 must contain one unique directory name.
18716 Those names are added to the corresponding path
18717 in their order of appearance in the file. The names can be either absolute
18718 or relative; in the latter case, they are relative to where theses files
18721 The files @file{ada_source_path} and @file{ada_object_path} might not be
18723 GNAT installation, in which case, GNAT will look for its run-time library in
18724 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
18725 objects and @file{ALI} files). When the files exist, the compiler does not
18726 look in @file{adainclude} and @file{adalib}, and thus the
18727 @file{ada_source_path} file
18728 must contain the location for the GNAT run-time sources (which can simply
18729 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
18730 contain the location for the GNAT run-time objects (which can simply
18733 You can also specify a new default path to the run-time library at compilation
18734 time with the switch @option{--RTS=rts-path}. You can thus choose / change
18735 the run-time library you want your program to be compiled with. This switch is
18736 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
18737 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
18739 It is possible to install a library before or after the standard GNAT
18740 library, by reordering the lines in the configuration files. In general, a
18741 library must be installed before the GNAT library if it redefines
18744 @node Using a library
18745 @subsection Using a library
18747 @noindent Once again, the project facility greatly simplifies the use of
18748 libraries. In this context, using a library is just a matter of adding a
18749 @code{with} clause in the user project. For instance, to make use of the
18750 library @code{My_Lib} shown in examples in earlier sections, you can
18753 @smallexample @c projectfile
18760 Even if you have a third-party, non-Ada library, you can still use GNAT's
18761 Project Manager facility to provide a wrapper for it. For example, the
18762 following project, when @code{with}ed by your main project, will link with the
18763 third-party library @file{liba.a}:
18765 @smallexample @c projectfile
18768 for Externally_Built use "true";
18769 for Source_Files use ();
18770 for Library_Dir use "lib";
18771 for Library_Name use "a";
18772 for Library_Kind use "static";
18776 This is an alternative to the use of @code{pragma Linker_Options}. It is
18777 especially interesting in the context of systems with several interdependent
18778 static libraries where finding a proper linker order is not easy and best be
18779 left to the tools having visibility over project dependence information.
18782 In order to use an Ada library manually, you need to make sure that this
18783 library is on both your source and object path
18784 (see @ref{Search Paths and the Run-Time Library (RTL)}
18785 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
18786 in an archive or a shared library, you need to specify the desired
18787 library at link time.
18789 For example, you can use the library @file{mylib} installed in
18790 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
18793 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
18798 This can be expressed more simply:
18803 when the following conditions are met:
18806 @file{/dir/my_lib_src} has been added by the user to the environment
18807 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
18808 @file{ada_source_path}
18810 @file{/dir/my_lib_obj} has been added by the user to the environment
18811 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
18812 @file{ada_object_path}
18814 a pragma @code{Linker_Options} has been added to one of the sources.
18817 @smallexample @c ada
18818 pragma Linker_Options ("-lmy_lib");
18822 @node Stand-alone Ada Libraries
18823 @section Stand-alone Ada Libraries
18824 @cindex Stand-alone library, building, using
18827 * Introduction to Stand-alone Libraries::
18828 * Building a Stand-alone Library::
18829 * Creating a Stand-alone Library to be used in a non-Ada context::
18830 * Restrictions in Stand-alone Libraries::
18833 @node Introduction to Stand-alone Libraries
18834 @subsection Introduction to Stand-alone Libraries
18837 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
18839 elaborate the Ada units that are included in the library. In contrast with
18840 an ordinary library, which consists of all sources, objects and @file{ALI}
18842 library, a SAL may specify a restricted subset of compilation units
18843 to serve as a library interface. In this case, the fully
18844 self-sufficient set of files will normally consist of an objects
18845 archive, the sources of interface units' specs, and the @file{ALI}
18846 files of interface units.
18847 If an interface spec contains a generic unit or an inlined subprogram,
18849 source must also be provided; if the units that must be provided in the source
18850 form depend on other units, the source and @file{ALI} files of those must
18853 The main purpose of a SAL is to minimize the recompilation overhead of client
18854 applications when a new version of the library is installed. Specifically,
18855 if the interface sources have not changed, client applications do not need to
18856 be recompiled. If, furthermore, a SAL is provided in the shared form and its
18857 version, controlled by @code{Library_Version} attribute, is not changed,
18858 then the clients do not need to be relinked.
18860 SALs also allow the library providers to minimize the amount of library source
18861 text exposed to the clients. Such ``information hiding'' might be useful or
18862 necessary for various reasons.
18864 Stand-alone libraries are also well suited to be used in an executable whose
18865 main routine is not written in Ada.
18867 @node Building a Stand-alone Library
18868 @subsection Building a Stand-alone Library
18871 GNAT's Project facility provides a simple way of building and installing
18872 stand-alone libraries; see @ref{Stand-alone Library Projects}.
18873 To be a Stand-alone Library Project, in addition to the two attributes
18874 that make a project a Library Project (@code{Library_Name} and
18875 @code{Library_Dir}; see @ref{Library Projects}), the attribute
18876 @code{Library_Interface} must be defined. For example:
18878 @smallexample @c projectfile
18880 for Library_Dir use "lib_dir";
18881 for Library_Name use "dummy";
18882 for Library_Interface use ("int1", "int1.child");
18887 Attribute @code{Library_Interface} has a non-empty string list value,
18888 each string in the list designating a unit contained in an immediate source
18889 of the project file.
18891 When a Stand-alone Library is built, first the binder is invoked to build
18892 a package whose name depends on the library name
18893 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
18894 This binder-generated package includes initialization and
18895 finalization procedures whose
18896 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
18898 above). The object corresponding to this package is included in the library.
18900 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
18901 calling of these procedures if a static SAL is built, or if a shared SAL
18903 with the project-level attribute @code{Library_Auto_Init} set to
18906 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
18907 (those that are listed in attribute @code{Library_Interface}) are copied to
18908 the Library Directory. As a consequence, only the Interface Units may be
18909 imported from Ada units outside of the library. If other units are imported,
18910 the binding phase will fail.
18912 The attribute @code{Library_Src_Dir} may be specified for a
18913 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
18914 single string value. Its value must be the path (absolute or relative to the
18915 project directory) of an existing directory. This directory cannot be the
18916 object directory or one of the source directories, but it can be the same as
18917 the library directory. The sources of the Interface
18918 Units of the library that are needed by an Ada client of the library will be
18919 copied to the designated directory, called the Interface Copy directory.
18920 These sources include the specs of the Interface Units, but they may also
18921 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
18922 are used, or when there is a generic unit in the spec. Before the sources
18923 are copied to the Interface Copy directory, an attempt is made to delete all
18924 files in the Interface Copy directory.
18926 Building stand-alone libraries by hand is somewhat tedious, but for those
18927 occasions when it is necessary here are the steps that you need to perform:
18930 Compile all library sources.
18933 Invoke the binder with the switch @option{-n} (No Ada main program),
18934 with all the @file{ALI} files of the interfaces, and
18935 with the switch @option{-L} to give specific names to the @code{init}
18936 and @code{final} procedures. For example:
18938 gnatbind -n int1.ali int2.ali -Lsal1
18942 Compile the binder generated file:
18948 Link the dynamic library with all the necessary object files,
18949 indicating to the linker the names of the @code{init} (and possibly
18950 @code{final}) procedures for automatic initialization (and finalization).
18951 The built library should be placed in a directory different from
18952 the object directory.
18955 Copy the @code{ALI} files of the interface to the library directory,
18956 add in this copy an indication that it is an interface to a SAL
18957 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
18958 with letter ``P'') and make the modified copy of the @file{ALI} file
18963 Using SALs is not different from using other libraries
18964 (see @ref{Using a library}).
18966 @node Creating a Stand-alone Library to be used in a non-Ada context
18967 @subsection Creating a Stand-alone Library to be used in a non-Ada context
18970 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
18973 The only extra step required is to ensure that library interface subprograms
18974 are compatible with the main program, by means of @code{pragma Export}
18975 or @code{pragma Convention}.
18977 Here is an example of simple library interface for use with C main program:
18979 @smallexample @c ada
18980 package Interface is
18982 procedure Do_Something;
18983 pragma Export (C, Do_Something, "do_something");
18985 procedure Do_Something_Else;
18986 pragma Export (C, Do_Something_Else, "do_something_else");
18992 On the foreign language side, you must provide a ``foreign'' view of the
18993 library interface; remember that it should contain elaboration routines in
18994 addition to interface subprograms.
18996 The example below shows the content of @code{mylib_interface.h} (note
18997 that there is no rule for the naming of this file, any name can be used)
18999 /* the library elaboration procedure */
19000 extern void mylibinit (void);
19002 /* the library finalization procedure */
19003 extern void mylibfinal (void);
19005 /* the interface exported by the library */
19006 extern void do_something (void);
19007 extern void do_something_else (void);
19011 Libraries built as explained above can be used from any program, provided
19012 that the elaboration procedures (named @code{mylibinit} in the previous
19013 example) are called before the library services are used. Any number of
19014 libraries can be used simultaneously, as long as the elaboration
19015 procedure of each library is called.
19017 Below is an example of a C program that uses the @code{mylib} library.
19020 #include "mylib_interface.h"
19025 /* First, elaborate the library before using it */
19028 /* Main program, using the library exported entities */
19030 do_something_else ();
19032 /* Library finalization at the end of the program */
19039 Note that invoking any library finalization procedure generated by
19040 @code{gnatbind} shuts down the Ada run-time environment.
19042 finalization of all Ada libraries must be performed at the end of the program.
19043 No call to these libraries or to the Ada run-time library should be made
19044 after the finalization phase.
19046 @node Restrictions in Stand-alone Libraries
19047 @subsection Restrictions in Stand-alone Libraries
19050 The pragmas listed below should be used with caution inside libraries,
19051 as they can create incompatibilities with other Ada libraries:
19053 @item pragma @code{Locking_Policy}
19054 @item pragma @code{Queuing_Policy}
19055 @item pragma @code{Task_Dispatching_Policy}
19056 @item pragma @code{Unreserve_All_Interrupts}
19060 When using a library that contains such pragmas, the user must make sure
19061 that all libraries use the same pragmas with the same values. Otherwise,
19062 @code{Program_Error} will
19063 be raised during the elaboration of the conflicting
19064 libraries. The usage of these pragmas and its consequences for the user
19065 should therefore be well documented.
19067 Similarly, the traceback in the exception occurrence mechanism should be
19068 enabled or disabled in a consistent manner across all libraries.
19069 Otherwise, Program_Error will be raised during the elaboration of the
19070 conflicting libraries.
19072 If the @code{Version} or @code{Body_Version}
19073 attributes are used inside a library, then you need to
19074 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19075 libraries, so that version identifiers can be properly computed.
19076 In practice these attributes are rarely used, so this is unlikely
19077 to be a consideration.
19079 @node Rebuilding the GNAT Run-Time Library
19080 @section Rebuilding the GNAT Run-Time Library
19081 @cindex GNAT Run-Time Library, rebuilding
19082 @cindex Building the GNAT Run-Time Library
19083 @cindex Rebuilding the GNAT Run-Time Library
19084 @cindex Run-Time Library, rebuilding
19087 It may be useful to recompile the GNAT library in various contexts, the
19088 most important one being the use of partition-wide configuration pragmas
19089 such as @code{Normalize_Scalars}. A special Makefile called
19090 @code{Makefile.adalib} is provided to that effect and can be found in
19091 the directory containing the GNAT library. The location of this
19092 directory depends on the way the GNAT environment has been installed and can
19093 be determined by means of the command:
19100 The last entry in the object search path usually contains the
19101 gnat library. This Makefile contains its own documentation and in
19102 particular the set of instructions needed to rebuild a new library and
19105 @node Using the GNU make Utility
19106 @chapter Using the GNU @code{make} Utility
19110 This chapter offers some examples of makefiles that solve specific
19111 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19112 make, make, GNU @code{make}}), nor does it try to replace the
19113 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19115 All the examples in this section are specific to the GNU version of
19116 make. Although @command{make} is a standard utility, and the basic language
19117 is the same, these examples use some advanced features found only in
19121 * Using gnatmake in a Makefile::
19122 * Automatically Creating a List of Directories::
19123 * Generating the Command Line Switches::
19124 * Overcoming Command Line Length Limits::
19127 @node Using gnatmake in a Makefile
19128 @section Using gnatmake in a Makefile
19133 Complex project organizations can be handled in a very powerful way by
19134 using GNU make combined with gnatmake. For instance, here is a Makefile
19135 which allows you to build each subsystem of a big project into a separate
19136 shared library. Such a makefile allows you to significantly reduce the link
19137 time of very big applications while maintaining full coherence at
19138 each step of the build process.
19140 The list of dependencies are handled automatically by
19141 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19142 the appropriate directories.
19144 Note that you should also read the example on how to automatically
19145 create the list of directories
19146 (@pxref{Automatically Creating a List of Directories})
19147 which might help you in case your project has a lot of subdirectories.
19152 @font@heightrm=cmr8
19155 ## This Makefile is intended to be used with the following directory
19157 ## - The sources are split into a series of csc (computer software components)
19158 ## Each of these csc is put in its own directory.
19159 ## Their name are referenced by the directory names.
19160 ## They will be compiled into shared library (although this would also work
19161 ## with static libraries
19162 ## - The main program (and possibly other packages that do not belong to any
19163 ## csc is put in the top level directory (where the Makefile is).
19164 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19165 ## \_ second_csc (sources) __ lib (will contain the library)
19167 ## Although this Makefile is build for shared library, it is easy to modify
19168 ## to build partial link objects instead (modify the lines with -shared and
19171 ## With this makefile, you can change any file in the system or add any new
19172 ## file, and everything will be recompiled correctly (only the relevant shared
19173 ## objects will be recompiled, and the main program will be re-linked).
19175 # The list of computer software component for your project. This might be
19176 # generated automatically.
19179 # Name of the main program (no extension)
19182 # If we need to build objects with -fPIC, uncomment the following line
19185 # The following variable should give the directory containing libgnat.so
19186 # You can get this directory through 'gnatls -v'. This is usually the last
19187 # directory in the Object_Path.
19190 # The directories for the libraries
19191 # (This macro expands the list of CSC to the list of shared libraries, you
19192 # could simply use the expanded form:
19193 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19194 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19196 $@{MAIN@}: objects $@{LIB_DIR@}
19197 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19198 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19201 # recompile the sources
19202 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19204 # Note: In a future version of GNAT, the following commands will be simplified
19205 # by a new tool, gnatmlib
19207 mkdir -p $@{dir $@@ @}
19208 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19209 cd $@{dir $@@ @} && cp -f ../*.ali .
19211 # The dependencies for the modules
19212 # Note that we have to force the expansion of *.o, since in some cases
19213 # make won't be able to do it itself.
19214 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19215 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19216 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19218 # Make sure all of the shared libraries are in the path before starting the
19221 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19224 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19225 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19226 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19227 $@{RM@} *.o *.ali $@{MAIN@}
19230 @node Automatically Creating a List of Directories
19231 @section Automatically Creating a List of Directories
19234 In most makefiles, you will have to specify a list of directories, and
19235 store it in a variable. For small projects, it is often easier to
19236 specify each of them by hand, since you then have full control over what
19237 is the proper order for these directories, which ones should be
19240 However, in larger projects, which might involve hundreds of
19241 subdirectories, it might be more convenient to generate this list
19244 The example below presents two methods. The first one, although less
19245 general, gives you more control over the list. It involves wildcard
19246 characters, that are automatically expanded by @command{make}. Its
19247 shortcoming is that you need to explicitly specify some of the
19248 organization of your project, such as for instance the directory tree
19249 depth, whether some directories are found in a separate tree, @enddots{}
19251 The second method is the most general one. It requires an external
19252 program, called @command{find}, which is standard on all Unix systems. All
19253 the directories found under a given root directory will be added to the
19259 @font@heightrm=cmr8
19262 # The examples below are based on the following directory hierarchy:
19263 # All the directories can contain any number of files
19264 # ROOT_DIRECTORY -> a -> aa -> aaa
19267 # -> b -> ba -> baa
19270 # This Makefile creates a variable called DIRS, that can be reused any time
19271 # you need this list (see the other examples in this section)
19273 # The root of your project's directory hierarchy
19277 # First method: specify explicitly the list of directories
19278 # This allows you to specify any subset of all the directories you need.
19281 DIRS := a/aa/ a/ab/ b/ba/
19284 # Second method: use wildcards
19285 # Note that the argument(s) to wildcard below should end with a '/'.
19286 # Since wildcards also return file names, we have to filter them out
19287 # to avoid duplicate directory names.
19288 # We thus use make's @code{dir} and @code{sort} functions.
19289 # It sets DIRs to the following value (note that the directories aaa and baa
19290 # are not given, unless you change the arguments to wildcard).
19291 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19294 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19295 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19298 # Third method: use an external program
19299 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19300 # This is the most complete command: it sets DIRs to the following value:
19301 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19304 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19308 @node Generating the Command Line Switches
19309 @section Generating the Command Line Switches
19312 Once you have created the list of directories as explained in the
19313 previous section (@pxref{Automatically Creating a List of Directories}),
19314 you can easily generate the command line arguments to pass to gnatmake.
19316 For the sake of completeness, this example assumes that the source path
19317 is not the same as the object path, and that you have two separate lists
19321 # see "Automatically creating a list of directories" to create
19326 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19327 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19330 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19333 @node Overcoming Command Line Length Limits
19334 @section Overcoming Command Line Length Limits
19337 One problem that might be encountered on big projects is that many
19338 operating systems limit the length of the command line. It is thus hard to give
19339 gnatmake the list of source and object directories.
19341 This example shows how you can set up environment variables, which will
19342 make @command{gnatmake} behave exactly as if the directories had been
19343 specified on the command line, but have a much higher length limit (or
19344 even none on most systems).
19346 It assumes that you have created a list of directories in your Makefile,
19347 using one of the methods presented in
19348 @ref{Automatically Creating a List of Directories}.
19349 For the sake of completeness, we assume that the object
19350 path (where the ALI files are found) is different from the sources patch.
19352 Note a small trick in the Makefile below: for efficiency reasons, we
19353 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19354 expanded immediately by @code{make}. This way we overcome the standard
19355 make behavior which is to expand the variables only when they are
19358 On Windows, if you are using the standard Windows command shell, you must
19359 replace colons with semicolons in the assignments to these variables.
19364 @font@heightrm=cmr8
19367 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19368 # This is the same thing as putting the -I arguments on the command line.
19369 # (the equivalent of using -aI on the command line would be to define
19370 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19371 # You can of course have different values for these variables.
19373 # Note also that we need to keep the previous values of these variables, since
19374 # they might have been set before running 'make' to specify where the GNAT
19375 # library is installed.
19377 # see "Automatically creating a list of directories" to create these
19383 space:=$@{empty@} $@{empty@}
19384 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19385 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19386 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19387 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19388 export ADA_INCLUDE_PATH
19389 export ADA_OBJECT_PATH
19396 @node Memory Management Issues
19397 @chapter Memory Management Issues
19400 This chapter describes some useful memory pools provided in the GNAT library
19401 and in particular the GNAT Debug Pool facility, which can be used to detect
19402 incorrect uses of access values (including ``dangling references'').
19404 It also describes the @command{gnatmem} tool, which can be used to track down
19409 * Some Useful Memory Pools::
19410 * The GNAT Debug Pool Facility::
19412 * The gnatmem Tool::
19416 @node Some Useful Memory Pools
19417 @section Some Useful Memory Pools
19418 @findex Memory Pool
19419 @cindex storage, pool
19422 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19423 storage pool. Allocations use the standard system call @code{malloc} while
19424 deallocations use the standard system call @code{free}. No reclamation is
19425 performed when the pool goes out of scope. For performance reasons, the
19426 standard default Ada allocators/deallocators do not use any explicit storage
19427 pools but if they did, they could use this storage pool without any change in
19428 behavior. That is why this storage pool is used when the user
19429 manages to make the default implicit allocator explicit as in this example:
19430 @smallexample @c ada
19431 type T1 is access Something;
19432 -- no Storage pool is defined for T2
19433 type T2 is access Something_Else;
19434 for T2'Storage_Pool use T1'Storage_Pool;
19435 -- the above is equivalent to
19436 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19440 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19441 pool. The allocation strategy is similar to @code{Pool_Local}'s
19442 except that the all
19443 storage allocated with this pool is reclaimed when the pool object goes out of
19444 scope. This pool provides a explicit mechanism similar to the implicit one
19445 provided by several Ada 83 compilers for allocations performed through a local
19446 access type and whose purpose was to reclaim memory when exiting the
19447 scope of a given local access. As an example, the following program does not
19448 leak memory even though it does not perform explicit deallocation:
19450 @smallexample @c ada
19451 with System.Pool_Local;
19452 procedure Pooloc1 is
19453 procedure Internal is
19454 type A is access Integer;
19455 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19456 for A'Storage_Pool use X;
19459 for I in 1 .. 50 loop
19464 for I in 1 .. 100 loop
19471 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19472 @code{Storage_Size} is specified for an access type.
19473 The whole storage for the pool is
19474 allocated at once, usually on the stack at the point where the access type is
19475 elaborated. It is automatically reclaimed when exiting the scope where the
19476 access type is defined. This package is not intended to be used directly by the
19477 user and it is implicitly used for each such declaration:
19479 @smallexample @c ada
19480 type T1 is access Something;
19481 for T1'Storage_Size use 10_000;
19484 @node The GNAT Debug Pool Facility
19485 @section The GNAT Debug Pool Facility
19487 @cindex storage, pool, memory corruption
19490 The use of unchecked deallocation and unchecked conversion can easily
19491 lead to incorrect memory references. The problems generated by such
19492 references are usually difficult to tackle because the symptoms can be
19493 very remote from the origin of the problem. In such cases, it is
19494 very helpful to detect the problem as early as possible. This is the
19495 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19497 In order to use the GNAT specific debugging pool, the user must
19498 associate a debug pool object with each of the access types that may be
19499 related to suspected memory problems. See Ada Reference Manual 13.11.
19500 @smallexample @c ada
19501 type Ptr is access Some_Type;
19502 Pool : GNAT.Debug_Pools.Debug_Pool;
19503 for Ptr'Storage_Pool use Pool;
19507 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19508 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19509 allow the user to redefine allocation and deallocation strategies. They
19510 also provide a checkpoint for each dereference, through the use of
19511 the primitive operation @code{Dereference} which is implicitly called at
19512 each dereference of an access value.
19514 Once an access type has been associated with a debug pool, operations on
19515 values of the type may raise four distinct exceptions,
19516 which correspond to four potential kinds of memory corruption:
19519 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19521 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19523 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19525 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19529 For types associated with a Debug_Pool, dynamic allocation is performed using
19530 the standard GNAT allocation routine. References to all allocated chunks of
19531 memory are kept in an internal dictionary. Several deallocation strategies are
19532 provided, whereupon the user can choose to release the memory to the system,
19533 keep it allocated for further invalid access checks, or fill it with an easily
19534 recognizable pattern for debug sessions. The memory pattern is the old IBM
19535 hexadecimal convention: @code{16#DEADBEEF#}.
19537 See the documentation in the file g-debpoo.ads for more information on the
19538 various strategies.
19540 Upon each dereference, a check is made that the access value denotes a
19541 properly allocated memory location. Here is a complete example of use of
19542 @code{Debug_Pools}, that includes typical instances of memory corruption:
19543 @smallexample @c ada
19547 with Gnat.Io; use Gnat.Io;
19548 with Unchecked_Deallocation;
19549 with Unchecked_Conversion;
19550 with GNAT.Debug_Pools;
19551 with System.Storage_Elements;
19552 with Ada.Exceptions; use Ada.Exceptions;
19553 procedure Debug_Pool_Test is
19555 type T is access Integer;
19556 type U is access all T;
19558 P : GNAT.Debug_Pools.Debug_Pool;
19559 for T'Storage_Pool use P;
19561 procedure Free is new Unchecked_Deallocation (Integer, T);
19562 function UC is new Unchecked_Conversion (U, T);
19565 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
19575 Put_Line (Integer'Image(B.all));
19577 when E : others => Put_Line ("raised: " & Exception_Name (E));
19582 when E : others => Put_Line ("raised: " & Exception_Name (E));
19586 Put_Line (Integer'Image(B.all));
19588 when E : others => Put_Line ("raised: " & Exception_Name (E));
19593 when E : others => Put_Line ("raised: " & Exception_Name (E));
19596 end Debug_Pool_Test;
19600 The debug pool mechanism provides the following precise diagnostics on the
19601 execution of this erroneous program:
19604 Total allocated bytes : 0
19605 Total deallocated bytes : 0
19606 Current Water Mark: 0
19610 Total allocated bytes : 8
19611 Total deallocated bytes : 0
19612 Current Water Mark: 8
19615 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
19616 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
19617 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
19618 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
19620 Total allocated bytes : 8
19621 Total deallocated bytes : 4
19622 Current Water Mark: 4
19627 @node The gnatmem Tool
19628 @section The @command{gnatmem} Tool
19632 The @code{gnatmem} utility monitors dynamic allocation and
19633 deallocation activity in a program, and displays information about
19634 incorrect deallocations and possible sources of memory leaks.
19635 It provides three type of information:
19638 General information concerning memory management, such as the total
19639 number of allocations and deallocations, the amount of allocated
19640 memory and the high water mark, i.e.@: the largest amount of allocated
19641 memory in the course of program execution.
19644 Backtraces for all incorrect deallocations, that is to say deallocations
19645 which do not correspond to a valid allocation.
19648 Information on each allocation that is potentially the origin of a memory
19653 * Running gnatmem::
19654 * Switches for gnatmem::
19655 * Example of gnatmem Usage::
19658 @node Running gnatmem
19659 @subsection Running @code{gnatmem}
19662 @code{gnatmem} makes use of the output created by the special version of
19663 allocation and deallocation routines that record call information. This
19664 allows to obtain accurate dynamic memory usage history at a minimal cost to
19665 the execution speed. Note however, that @code{gnatmem} is not supported on
19666 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
19667 Solaris and Windows NT/2000/XP (x86).
19670 The @code{gnatmem} command has the form
19673 $ gnatmem @ovar{switches} user_program
19677 The program must have been linked with the instrumented version of the
19678 allocation and deallocation routines. This is done by linking with the
19679 @file{libgmem.a} library. For correct symbolic backtrace information,
19680 the user program should be compiled with debugging options
19681 (see @ref{Switches for gcc}). For example to build @file{my_program}:
19684 $ gnatmake -g my_program -largs -lgmem
19688 As library @file{libgmem.a} contains an alternate body for package
19689 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
19690 when an executable is linked with library @file{libgmem.a}. It is then not
19691 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
19694 When @file{my_program} is executed, the file @file{gmem.out} is produced.
19695 This file contains information about all allocations and deallocations
19696 performed by the program. It is produced by the instrumented allocations and
19697 deallocations routines and will be used by @code{gnatmem}.
19699 In order to produce symbolic backtrace information for allocations and
19700 deallocations performed by the GNAT run-time library, you need to use a
19701 version of that library that has been compiled with the @option{-g} switch
19702 (see @ref{Rebuilding the GNAT Run-Time Library}).
19704 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
19705 examine. If the location of @file{gmem.out} file was not explicitly supplied by
19706 @option{-i} switch, gnatmem will assume that this file can be found in the
19707 current directory. For example, after you have executed @file{my_program},
19708 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
19711 $ gnatmem my_program
19715 This will produce the output with the following format:
19717 *************** debut cc
19719 $ gnatmem my_program
19723 Total number of allocations : 45
19724 Total number of deallocations : 6
19725 Final Water Mark (non freed mem) : 11.29 Kilobytes
19726 High Water Mark : 11.40 Kilobytes
19731 Allocation Root # 2
19732 -------------------
19733 Number of non freed allocations : 11
19734 Final Water Mark (non freed mem) : 1.16 Kilobytes
19735 High Water Mark : 1.27 Kilobytes
19737 my_program.adb:23 my_program.alloc
19743 The first block of output gives general information. In this case, the
19744 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
19745 Unchecked_Deallocation routine occurred.
19748 Subsequent paragraphs display information on all allocation roots.
19749 An allocation root is a specific point in the execution of the program
19750 that generates some dynamic allocation, such as a ``@code{@b{new}}''
19751 construct. This root is represented by an execution backtrace (or subprogram
19752 call stack). By default the backtrace depth for allocations roots is 1, so
19753 that a root corresponds exactly to a source location. The backtrace can
19754 be made deeper, to make the root more specific.
19756 @node Switches for gnatmem
19757 @subsection Switches for @code{gnatmem}
19760 @code{gnatmem} recognizes the following switches:
19765 @cindex @option{-q} (@code{gnatmem})
19766 Quiet. Gives the minimum output needed to identify the origin of the
19767 memory leaks. Omits statistical information.
19770 @cindex @var{N} (@code{gnatmem})
19771 N is an integer literal (usually between 1 and 10) which controls the
19772 depth of the backtraces defining allocation root. The default value for
19773 N is 1. The deeper the backtrace, the more precise the localization of
19774 the root. Note that the total number of roots can depend on this
19775 parameter. This parameter must be specified @emph{before} the name of the
19776 executable to be analyzed, to avoid ambiguity.
19779 @cindex @option{-b} (@code{gnatmem})
19780 This switch has the same effect as just depth parameter.
19782 @item -i @var{file}
19783 @cindex @option{-i} (@code{gnatmem})
19784 Do the @code{gnatmem} processing starting from @file{file}, rather than
19785 @file{gmem.out} in the current directory.
19788 @cindex @option{-m} (@code{gnatmem})
19789 This switch causes @code{gnatmem} to mask the allocation roots that have less
19790 than n leaks. The default value is 1. Specifying the value of 0 will allow to
19791 examine even the roots that didn't result in leaks.
19794 @cindex @option{-s} (@code{gnatmem})
19795 This switch causes @code{gnatmem} to sort the allocation roots according to the
19796 specified order of sort criteria, each identified by a single letter. The
19797 currently supported criteria are @code{n, h, w} standing respectively for
19798 number of unfreed allocations, high watermark, and final watermark
19799 corresponding to a specific root. The default order is @code{nwh}.
19803 @node Example of gnatmem Usage
19804 @subsection Example of @code{gnatmem} Usage
19807 The following example shows the use of @code{gnatmem}
19808 on a simple memory-leaking program.
19809 Suppose that we have the following Ada program:
19811 @smallexample @c ada
19814 with Unchecked_Deallocation;
19815 procedure Test_Gm is
19817 type T is array (1..1000) of Integer;
19818 type Ptr is access T;
19819 procedure Free is new Unchecked_Deallocation (T, Ptr);
19822 procedure My_Alloc is
19827 procedure My_DeAlloc is
19835 for I in 1 .. 5 loop
19836 for J in I .. 5 loop
19847 The program needs to be compiled with debugging option and linked with
19848 @code{gmem} library:
19851 $ gnatmake -g test_gm -largs -lgmem
19855 Then we execute the program as usual:
19862 Then @code{gnatmem} is invoked simply with
19868 which produces the following output (result may vary on different platforms):
19873 Total number of allocations : 18
19874 Total number of deallocations : 5
19875 Final Water Mark (non freed mem) : 53.00 Kilobytes
19876 High Water Mark : 56.90 Kilobytes
19878 Allocation Root # 1
19879 -------------------
19880 Number of non freed allocations : 11
19881 Final Water Mark (non freed mem) : 42.97 Kilobytes
19882 High Water Mark : 46.88 Kilobytes
19884 test_gm.adb:11 test_gm.my_alloc
19886 Allocation Root # 2
19887 -------------------
19888 Number of non freed allocations : 1
19889 Final Water Mark (non freed mem) : 10.02 Kilobytes
19890 High Water Mark : 10.02 Kilobytes
19892 s-secsta.adb:81 system.secondary_stack.ss_init
19894 Allocation Root # 3
19895 -------------------
19896 Number of non freed allocations : 1
19897 Final Water Mark (non freed mem) : 12 Bytes
19898 High Water Mark : 12 Bytes
19900 s-secsta.adb:181 system.secondary_stack.ss_init
19904 Note that the GNAT run time contains itself a certain number of
19905 allocations that have no corresponding deallocation,
19906 as shown here for root #2 and root
19907 #3. This is a normal behavior when the number of non-freed allocations
19908 is one, it allocates dynamic data structures that the run time needs for
19909 the complete lifetime of the program. Note also that there is only one
19910 allocation root in the user program with a single line back trace:
19911 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
19912 program shows that 'My_Alloc' is called at 2 different points in the
19913 source (line 21 and line 24). If those two allocation roots need to be
19914 distinguished, the backtrace depth parameter can be used:
19917 $ gnatmem 3 test_gm
19921 which will give the following output:
19926 Total number of allocations : 18
19927 Total number of deallocations : 5
19928 Final Water Mark (non freed mem) : 53.00 Kilobytes
19929 High Water Mark : 56.90 Kilobytes
19931 Allocation Root # 1
19932 -------------------
19933 Number of non freed allocations : 10
19934 Final Water Mark (non freed mem) : 39.06 Kilobytes
19935 High Water Mark : 42.97 Kilobytes
19937 test_gm.adb:11 test_gm.my_alloc
19938 test_gm.adb:24 test_gm
19939 b_test_gm.c:52 main
19941 Allocation Root # 2
19942 -------------------
19943 Number of non freed allocations : 1
19944 Final Water Mark (non freed mem) : 10.02 Kilobytes
19945 High Water Mark : 10.02 Kilobytes
19947 s-secsta.adb:81 system.secondary_stack.ss_init
19948 s-secsta.adb:283 <system__secondary_stack___elabb>
19949 b_test_gm.c:33 adainit
19951 Allocation Root # 3
19952 -------------------
19953 Number of non freed allocations : 1
19954 Final Water Mark (non freed mem) : 3.91 Kilobytes
19955 High Water Mark : 3.91 Kilobytes
19957 test_gm.adb:11 test_gm.my_alloc
19958 test_gm.adb:21 test_gm
19959 b_test_gm.c:52 main
19961 Allocation Root # 4
19962 -------------------
19963 Number of non freed allocations : 1
19964 Final Water Mark (non freed mem) : 12 Bytes
19965 High Water Mark : 12 Bytes
19967 s-secsta.adb:181 system.secondary_stack.ss_init
19968 s-secsta.adb:283 <system__secondary_stack___elabb>
19969 b_test_gm.c:33 adainit
19973 The allocation root #1 of the first example has been split in 2 roots #1
19974 and #3 thanks to the more precise associated backtrace.
19978 @node Stack Related Facilities
19979 @chapter Stack Related Facilities
19982 This chapter describes some useful tools associated with stack
19983 checking and analysis. In
19984 particular, it deals with dynamic and static stack usage measurements.
19987 * Stack Overflow Checking::
19988 * Static Stack Usage Analysis::
19989 * Dynamic Stack Usage Analysis::
19992 @node Stack Overflow Checking
19993 @section Stack Overflow Checking
19994 @cindex Stack Overflow Checking
19995 @cindex -fstack-check
19998 For most operating systems, @command{gcc} does not perform stack overflow
19999 checking by default. This means that if the main environment task or
20000 some other task exceeds the available stack space, then unpredictable
20001 behavior will occur. Most native systems offer some level of protection by
20002 adding a guard page at the end of each task stack. This mechanism is usually
20003 not enough for dealing properly with stack overflow situations because
20004 a large local variable could ``jump'' above the guard page.
20005 Furthermore, when the
20006 guard page is hit, there may not be any space left on the stack for executing
20007 the exception propagation code. Enabling stack checking avoids
20010 To activate stack checking, compile all units with the gcc option
20011 @option{-fstack-check}. For example:
20014 gcc -c -fstack-check package1.adb
20018 Units compiled with this option will generate extra instructions to check
20019 that any use of the stack (for procedure calls or for declaring local
20020 variables in declare blocks) does not exceed the available stack space.
20021 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20023 For declared tasks, the stack size is controlled by the size
20024 given in an applicable @code{Storage_Size} pragma or by the value specified
20025 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20026 the default size as defined in the GNAT runtime otherwise.
20028 For the environment task, the stack size depends on
20029 system defaults and is unknown to the compiler. Stack checking
20030 may still work correctly if a fixed
20031 size stack is allocated, but this cannot be guaranteed.
20033 To ensure that a clean exception is signalled for stack
20034 overflow, set the environment variable
20035 @env{GNAT_STACK_LIMIT} to indicate the maximum
20036 stack area that can be used, as in:
20037 @cindex GNAT_STACK_LIMIT
20040 SET GNAT_STACK_LIMIT 1600
20044 The limit is given in kilobytes, so the above declaration would
20045 set the stack limit of the environment task to 1.6 megabytes.
20046 Note that the only purpose of this usage is to limit the amount
20047 of stack used by the environment task. If it is necessary to
20048 increase the amount of stack for the environment task, then this
20049 is an operating systems issue, and must be addressed with the
20050 appropriate operating systems commands.
20053 To have a fixed size stack in the environment task, the stack must be put
20054 in the P0 address space and its size specified. Use these switches to
20058 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20062 The quotes are required to keep case. The number after @samp{STACK=} is the
20063 size of the environmental task stack in pagelets (512 bytes). In this example
20064 the stack size is about 2 megabytes.
20067 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20068 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20069 more details about the @option{/p0image} qualifier and the @option{stack}
20073 @node Static Stack Usage Analysis
20074 @section Static Stack Usage Analysis
20075 @cindex Static Stack Usage Analysis
20076 @cindex -fstack-usage
20079 A unit compiled with @option{-fstack-usage} will generate an extra file
20081 the maximum amount of stack used, on a per-function basis.
20082 The file has the same
20083 basename as the target object file with a @file{.su} extension.
20084 Each line of this file is made up of three fields:
20088 The name of the function.
20092 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20095 The second field corresponds to the size of the known part of the function
20098 The qualifier @code{static} means that the function frame size
20100 It usually means that all local variables have a static size.
20101 In this case, the second field is a reliable measure of the function stack
20104 The qualifier @code{dynamic} means that the function frame size is not static.
20105 It happens mainly when some local variables have a dynamic size. When this
20106 qualifier appears alone, the second field is not a reliable measure
20107 of the function stack analysis. When it is qualified with @code{bounded}, it
20108 means that the second field is a reliable maximum of the function stack
20111 @node Dynamic Stack Usage Analysis
20112 @section Dynamic Stack Usage Analysis
20115 It is possible to measure the maximum amount of stack used by a task, by
20116 adding a switch to @command{gnatbind}, as:
20119 $ gnatbind -u0 file
20123 With this option, at each task termination, its stack usage is output on
20125 It is not always convenient to output the stack usage when the program
20126 is still running. Hence, it is possible to delay this output until program
20127 termination. for a given number of tasks specified as the argument of the
20128 @option{-u} option. For instance:
20131 $ gnatbind -u100 file
20135 will buffer the stack usage information of the first 100 tasks to terminate and
20136 output this info at program termination. Results are displayed in four
20140 Index | Task Name | Stack Size | Actual Use [min - max]
20147 is a number associated with each task.
20150 is the name of the task analyzed.
20153 is the maximum size for the stack.
20156 is the measure done by the stack analyzer. In order to prevent overflow,
20157 the stack is not entirely analyzed, and it's not possible to know exactly how
20158 much has actually been used. The real amount of stack used is between the min
20164 The environment task stack, e.g., the stack that contains the main unit, is
20165 only processed when the environment variable GNAT_STACK_LIMIT is set.
20168 @c *********************************
20170 @c *********************************
20171 @node Verifying Properties Using gnatcheck
20172 @chapter Verifying Properties Using @command{gnatcheck}
20174 @cindex @command{gnatcheck}
20177 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20178 of Ada source files according to a given set of semantic rules.
20181 In order to check compliance with a given rule, @command{gnatcheck} has to
20182 semantically analyze the Ada sources.
20183 Therefore, checks can only be performed on
20184 legal Ada units. Moreover, when a unit depends semantically upon units located
20185 outside the current directory, the source search path has to be provided when
20186 calling @command{gnatcheck}, either through a specified project file or
20187 through @command{gnatcheck} switches as described below.
20189 A number of rules are predefined in @command{gnatcheck} and are described
20190 later in this chapter.
20191 You can also add new rules, by modifying the @command{gnatcheck} code and
20192 rebuilding the tool. In order to add a simple rule making some local checks,
20193 a small amount of straightforward ASIS-based programming is usually needed.
20195 Project support for @command{gnatcheck} is provided by the GNAT
20196 driver (see @ref{The GNAT Driver and Project Files}).
20198 Invoking @command{gnatcheck} on the command line has the form:
20201 $ gnatcheck @ovar{switches} @{@var{filename}@}
20202 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20203 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20210 @var{switches} specify the general tool options
20213 Each @var{filename} is the name (including the extension) of a source
20214 file to process. ``Wildcards'' are allowed, and
20215 the file name may contain path information.
20218 Each @var{arg_list_filename} is the name (including the extension) of a text
20219 file containing the names of the source files to process, separated by spaces
20223 @var{gcc_switches} is a list of switches for
20224 @command{gcc}. They will be passed on to all compiler invocations made by
20225 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20226 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20227 and use the @option{-gnatec} switch to set the configuration file.
20230 @var{rule_options} is a list of options for controlling a set of
20231 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20235 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20238 * Format of the Report File::
20239 * General gnatcheck Switches::
20240 * gnatcheck Rule Options::
20241 * Adding the Results of Compiler Checks to gnatcheck Output::
20242 * Project-Wide Checks::
20243 * Predefined Rules::
20246 @node Format of the Report File
20247 @section Format of the Report File
20248 @cindex Report file (for @code{gnatcheck})
20251 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20253 It also creates, in the current
20254 directory, a text file named @file{^gnatcheck.out^GNATCHECK.OUT^} that
20255 contains the complete report of the last gnatcheck run. This report contains:
20257 @item a list of the Ada source files being checked,
20258 @item a list of enabled and disabled rules,
20259 @item a list of the diagnostic messages, ordered in three different ways
20260 and collected in three separate
20261 sections. Section 1 contains the raw list of diagnostic messages. It
20262 corresponds to the output going to @file{stdout}. Section 2 contains
20263 messages ordered by rules.
20264 Section 3 contains messages ordered by source files.
20267 @node General gnatcheck Switches
20268 @section General @command{gnatcheck} Switches
20271 The following switches control the general @command{gnatcheck} behavior
20275 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20277 Process all units including those with read-only ALI files such as
20278 those from GNAT Run-Time library.
20282 @cindex @option{-d} (@command{gnatcheck})
20287 @cindex @option{-dd} (@command{gnatcheck})
20289 Progress indicator mode (for use in GPS)
20292 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20294 List the predefined and user-defined rules. For more details see
20295 @ref{Predefined Rules}.
20297 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20299 Use full source locations references in the report file. For a construct from
20300 a generic instantiation a full source location is a chain from the location
20301 of this construct in the generic unit to the place where this unit is
20304 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20306 Quiet mode. All the diagnoses about rule violations are placed in the
20307 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20309 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20311 Short format of the report file (no version information, no list of applied
20312 rules, no list of checked sources is included)
20314 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20315 @item ^-s1^/COMPILER_STYLE^
20316 Include the compiler-style section in the report file
20318 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20319 @item ^-s2^/BY_RULES^
20320 Include the section containing diagnoses ordered by rules in the report file
20322 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20323 @item ^-s3^/BY_FILES_BY_RULES^
20324 Include the section containing diagnoses ordered by files and then by rules
20327 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20328 @item ^-v^/VERBOSE^
20329 Verbose mode; @command{gnatcheck} generates version information and then
20330 a trace of sources being processed.
20335 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20336 @option{^-s2^/BY_RULES^} or
20337 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20338 then the @command{gnatcheck} report file will only contain sections
20339 explicitly denoted by these options.
20341 @node gnatcheck Rule Options
20342 @section @command{gnatcheck} Rule Options
20345 The following options control the processing performed by
20346 @command{gnatcheck}.
20349 @cindex @option{+ALL} (@command{gnatcheck})
20351 Turn all the rule checks ON.
20353 @cindex @option{-ALL} (@command{gnatcheck})
20355 Turn all the rule checks OFF.
20357 @cindex @option{+R} (@command{gnatcheck})
20358 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20359 Turn on the check for a specified rule with the specified parameter, if any.
20360 @var{rule_id} must be the identifier of one of the currently implemented rules
20361 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20362 are not case-sensitive. The @var{param} item must
20363 be a string representing a valid parameter(s) for the specified rule.
20364 If it contains any space characters then this string must be enclosed in
20367 @cindex @option{-R} (@command{gnatcheck})
20368 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20369 Turn off the check for a specified rule with the specified parameter, if any.
20371 @cindex @option{-from} (@command{gnatcheck})
20372 @item -from=@var{rule_option_filename}
20373 Read the rule options from the text file @var{rule_option_filename}, referred as
20374 ``rule file'' below.
20379 The default behavior is that all the rule checks are enabled, except for
20380 the checks performed by the compiler.
20382 and the checks associated with the
20386 A rule file is a text file containing a set of rule options.
20387 @cindex Rule file (for @code{gnatcheck})
20388 The file may contain empty lines and Ada-style comments (comment
20389 lines and end-of-line comments). The rule file has free format; that is,
20390 you do not have to start a new rule option on a new line.
20392 A rule file may contain other @option{-from=@var{rule_option_filename}}
20393 options, each such option being replaced with the content of the
20394 corresponding rule file during the rule files processing. In case a
20395 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20396 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20397 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20398 the processing of rule files is interrupted and a part of their content
20402 @node Adding the Results of Compiler Checks to gnatcheck Output
20403 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20406 The @command{gnatcheck} tool can include in the generated diagnostic messages
20408 the report file the results of the checks performed by the compiler. Though
20409 disabled by default, this effect may be obtained by using @option{+R} with
20410 the following rule identifiers and parameters:
20414 To record restrictions violations (that are performed by the compiler if the
20415 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20417 @code{Restrictions} with the same parameters as pragma
20418 @code{Restrictions} or @code{Restriction_Warnings}.
20421 To record compiler style checks(@pxref{Style Checking}), use the rule named
20422 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20423 which enables all the standard style checks that corresponds to @option{-gnatyy}
20424 GNAT style check option, or a string that has exactly the same
20425 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20426 @code{Style_Checks} (for further information about this pragma,
20427 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}).
20430 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20431 named @code{Warnings} with a parameter that is a valid
20432 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20433 (for further information about this pragma, @pxref{Pragma Warnings,,,
20434 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20435 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20436 all the specific warnings, but not suppresses the warning mode,
20437 and 'e' parameter, corresponding to @option{-gnatwe} that means
20438 "treat warnings as errors", does not have any effect.
20442 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20443 option with the corresponding restriction name as a parameter. @code{-R} is
20444 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20445 warnings and style checks, use the corresponding warning and style options.
20447 @node Project-Wide Checks
20448 @section Project-Wide Checks
20449 @cindex Project-wide checks (for @command{gnatcheck})
20452 In order to perform checks on all units of a given project, you can use
20453 the GNAT driver along with the @option{-P} option:
20455 gnat check -Pproj -rules -from=my_rules
20459 If the project @code{proj} depends upon other projects, you can perform
20460 checks on the project closure using the @option{-U} option:
20462 gnat check -Pproj -U -rules -from=my_rules
20466 Finally, if not all the units are relevant to a particular main
20467 program in the project closure, you can perform checks for the set
20468 of units needed to create a given main program (unit closure) using
20469 the @option{-U} option followed by the name of the main unit:
20471 gnat check -Pproj -U main -rules -from=my_rules
20475 @node Predefined Rules
20476 @section Predefined Rules
20477 @cindex Predefined rules (for @command{gnatcheck})
20480 @c (Jan 2007) Since the global rules are still under development and are not
20481 @c documented, there is no point in explaining the difference between
20482 @c global and local rules
20484 A rule in @command{gnatcheck} is either local or global.
20485 A @emph{local rule} is a rule that applies to a well-defined section
20486 of a program and that can be checked by analyzing only this section.
20487 A @emph{global rule} requires analysis of some global properties of the
20488 whole program (mostly related to the program call graph).
20489 As of @value{NOW}, the implementation of global rules should be
20490 considered to be at a preliminary stage. You can use the
20491 @option{+GLOBAL} option to enable all the global rules, and the
20492 @option{-GLOBAL} rule option to disable all the global rules.
20494 All the global rules in the list below are
20495 so indicated by marking them ``GLOBAL''.
20496 This +GLOBAL and -GLOBAL options are not
20497 included in the list of gnatcheck options above, because at the moment they
20498 are considered as a temporary debug options.
20500 @command{gnatcheck} performs rule checks for generic
20501 instances only for global rules. This limitation may be relaxed in a later
20506 The following subsections document the rules implemented in
20507 @command{gnatcheck}.
20508 The subsection title is the same as the rule identifier, which may be
20509 used as a parameter of the @option{+R} or @option{-R} options.
20513 * Abstract_Type_Declarations::
20514 * Anonymous_Arrays::
20515 * Anonymous_Subtypes::
20517 * Boolean_Relational_Operators::
20519 * Ceiling_Violations::
20521 * Controlled_Type_Declarations::
20522 * Declarations_In_Blocks::
20523 * Default_Parameters::
20524 * Discriminated_Records::
20525 * Enumeration_Ranges_In_CASE_Statements::
20526 * Exceptions_As_Control_Flow::
20527 * EXIT_Statements_With_No_Loop_Name::
20528 * Expanded_Loop_Exit_Names::
20529 * Explicit_Full_Discrete_Ranges::
20530 * Float_Equality_Checks::
20531 * Forbidden_Pragmas::
20532 * Function_Style_Procedures::
20533 * Generics_In_Subprograms::
20534 * GOTO_Statements::
20535 * Implicit_IN_Mode_Parameters::
20536 * Implicit_SMALL_For_Fixed_Point_Types::
20537 * Improperly_Located_Instantiations::
20538 * Improper_Returns::
20539 * Library_Level_Subprograms::
20542 * Improperly_Called_Protected_Entries::
20545 * Misnamed_Identifiers::
20546 * Multiple_Entries_In_Protected_Definitions::
20548 * Non_Qualified_Aggregates::
20549 * Non_Short_Circuit_Operators::
20550 * Non_SPARK_Attributes::
20551 * Non_Tagged_Derived_Types::
20552 * Non_Visible_Exceptions::
20553 * Numeric_Literals::
20554 * OTHERS_In_Aggregates::
20555 * OTHERS_In_CASE_Statements::
20556 * OTHERS_In_Exception_Handlers::
20557 * Outer_Loop_Exits::
20558 * Overloaded_Operators::
20559 * Overly_Nested_Control_Structures::
20560 * Parameters_Out_Of_Order::
20561 * Positional_Actuals_For_Defaulted_Generic_Parameters::
20562 * Positional_Actuals_For_Defaulted_Parameters::
20563 * Positional_Components::
20564 * Positional_Generic_Parameters::
20565 * Positional_Parameters::
20566 * Predefined_Numeric_Types::
20567 * Raising_External_Exceptions::
20568 * Raising_Predefined_Exceptions::
20569 * Separate_Numeric_Error_Handlers::
20572 * Side_Effect_Functions::
20575 * Unassigned_OUT_Parameters::
20576 * Uncommented_BEGIN_In_Package_Bodies::
20577 * Unconstrained_Array_Returns::
20578 * Universal_Ranges::
20579 * Unnamed_Blocks_And_Loops::
20581 * Unused_Subprograms::
20583 * USE_PACKAGE_Clauses::
20584 * Volatile_Objects_Without_Address_Clauses::
20588 @node Abstract_Type_Declarations
20589 @subsection @code{Abstract_Type_Declarations}
20590 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
20593 Flag all declarations of abstract types. For an abstract private
20594 type, both the private and full type declarations are flagged.
20596 This rule has no parameters.
20599 @node Anonymous_Arrays
20600 @subsection @code{Anonymous_Arrays}
20601 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
20604 Flag all anonymous array type definitions (by Ada semantics these can only
20605 occur in object declarations).
20607 This rule has no parameters.
20609 @node Anonymous_Subtypes
20610 @subsection @code{Anonymous_Subtypes}
20611 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
20614 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
20615 any instance of a subtype indication with a constraint, other than one
20616 that occurs immediately within a subtype declaration. Any use of a range
20617 other than as a constraint used immediately within a subtype declaration
20618 is considered as an anonymous subtype.
20620 An effect of this rule is that @code{for} loops such as the following are
20621 flagged (since @code{1..N} is formally a ``range''):
20623 @smallexample @c ada
20624 for I in 1 .. N loop
20630 Declaring an explicit subtype solves the problem:
20632 @smallexample @c ada
20633 subtype S is Integer range 1..N;
20641 This rule has no parameters.
20644 @subsection @code{Blocks}
20645 @cindex @code{Blocks} rule (for @command{gnatcheck})
20648 Flag each block statement.
20650 This rule has no parameters.
20652 @node Boolean_Relational_Operators
20653 @subsection @code{Boolean_Relational_Operators}
20654 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
20657 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
20658 ``>='', ``='' and ``/='') for the predefined Boolean type.
20659 (This rule is useful in enforcing the SPARK language restrictions.)
20661 Calls to predefined relational operators of any type derived from
20662 @code{Standard.Boolean} are not detected. Calls to user-defined functions
20663 with these designators, and uses of operators that are renamings
20664 of the predefined relational operators for @code{Standard.Boolean},
20665 are likewise not detected.
20667 This rule has no parameters.
20670 @node Ceiling_Violations
20671 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
20672 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
20675 Flag invocations of a protected operation by a task whose priority exceeds
20676 the protected object's ceiling.
20678 As of @value{NOW}, this rule has the following limitations:
20683 We consider only pragmas Priority and Interrupt_Priority as means to define
20684 a task/protected operation priority. We do not consider the effect of using
20685 Ada.Dynamic_Priorities.Set_Priority procedure;
20688 We consider only base task priorities, and no priority inheritance. That is,
20689 we do not make a difference between calls issued during task activation and
20690 execution of the sequence of statements from task body;
20693 Any situation when the priority of protected operation caller is set by a
20694 dynamic expression (that is, the corresponding Priority or
20695 Interrupt_Priority pragma has a non-static expression as an argument) we
20696 treat as a priority inconsistency (and, therefore, detect this situation).
20700 At the moment the notion of the main subprogram is not implemented in
20701 gnatcheck, so any pragma Priority in a library level subprogram body (in case
20702 if this subprogram can be a main subprogram of a partition) changes the
20703 priority of an environment task. So if we have more then one such pragma in
20704 the set of processed sources, the pragma that is processed last, defines the
20705 priority of an environment task.
20707 This rule has no parameters.
20710 @node Controlled_Type_Declarations
20711 @subsection @code{Controlled_Type_Declarations}
20712 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
20715 Flag all declarations of controlled types. A declaration of a private type
20716 is flagged if its full declaration declares a controlled type. A declaration
20717 of a derived type is flagged if its ancestor type is controlled. Subtype
20718 declarations are not checked. A declaration of a type that itself is not a
20719 descendant of a type declared in @code{Ada.Finalization} but has a controlled
20720 component is not checked.
20722 This rule has no parameters.
20726 @node Declarations_In_Blocks
20727 @subsection @code{Declarations_In_Blocks}
20728 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
20731 Flag all block statements containing local declarations. A @code{declare}
20732 block with an empty @i{declarative_part} or with a @i{declarative part}
20733 containing only pragmas and/or @code{use} clauses is not flagged.
20735 This rule has no parameters.
20738 @node Default_Parameters
20739 @subsection @code{Default_Parameters}
20740 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
20743 Flag all default expressions for subprogram parameters. Parameter
20744 declarations of formal and generic subprograms are also checked.
20746 This rule has no parameters.
20749 @node Discriminated_Records
20750 @subsection @code{Discriminated_Records}
20751 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
20754 Flag all declarations of record types with discriminants. Only the
20755 declarations of record and record extension types are checked. Incomplete,
20756 formal, private, derived and private extension type declarations are not
20757 checked. Task and protected type declarations also are not checked.
20759 This rule has no parameters.
20762 @node Enumeration_Ranges_In_CASE_Statements
20763 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
20764 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
20767 Flag each use of a range of enumeration literals as a choice in a
20768 @code{case} statement.
20769 All forms for specifying a range (explicit ranges
20770 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
20771 An enumeration range is
20772 flagged even if contains exactly one enumeration value or no values at all. A
20773 type derived from an enumeration type is considered as an enumeration type.
20775 This rule helps prevent maintenance problems arising from adding an
20776 enumeration value to a type and having it implicitly handled by an existing
20777 @code{case} statement with an enumeration range that includes the new literal.
20779 This rule has no parameters.
20782 @node Exceptions_As_Control_Flow
20783 @subsection @code{Exceptions_As_Control_Flow}
20784 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
20787 Flag each place where an exception is explicitly raised and handled in the
20788 same subprogram body. A @code{raise} statement in an exception handler,
20789 package body, task body or entry body is not flagged.
20791 The rule has no parameters.
20793 @node EXIT_Statements_With_No_Loop_Name
20794 @subsection @code{EXIT_Statements_With_No_Loop_Name}
20795 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
20798 Flag each @code{exit} statement that does not specify the name of the loop
20801 The rule has no parameters.
20804 @node Expanded_Loop_Exit_Names
20805 @subsection @code{Expanded_Loop_Exit_Names}
20806 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
20809 Flag all expanded loop names in @code{exit} statements.
20811 This rule has no parameters.
20813 @node Explicit_Full_Discrete_Ranges
20814 @subsection @code{Explicit_Full_Discrete_Ranges}
20815 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
20818 Flag each discrete range that has the form @code{A'First .. A'Last}.
20820 This rule has no parameters.
20822 @node Float_Equality_Checks
20823 @subsection @code{Float_Equality_Checks}
20824 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
20827 Flag all calls to the predefined equality operations for floating-point types.
20828 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
20829 User-defined equality operations are not flagged, nor are ``@code{=}''
20830 and ``@code{/=}'' operations for fixed-point types.
20832 This rule has no parameters.
20835 @node Forbidden_Pragmas
20836 @subsection @code{Forbidden_Pragmas}
20837 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
20840 Flag each use of the specified pragmas. The pragmas to be detected
20841 are named in the rule's parameters.
20843 This rule has the following parameters:
20846 @item For the @option{+R} option
20849 @item @emph{Pragma_Name}
20850 Adds the specified pragma to the set of pragmas to be
20851 checked and sets the checks for all the specified pragmas
20852 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
20853 does not correspond to any pragma name defined in the Ada
20854 standard or to the name of a GNAT-specific pragma defined
20855 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
20856 Manual}, it is treated as the name of unknown pragma.
20859 All the GNAT-specific pragmas are detected; this sets
20860 the checks for all the specified pragmas ON.
20863 All pragmas are detected; this sets the rule ON.
20866 @item For the @option{-R} option
20868 @item @emph{Pragma_Name}
20869 Removes the specified pragma from the set of pragmas to be
20870 checked without affecting checks for
20871 other pragmas. @emph{Pragma_Name} is treated as a name
20872 of a pragma. If it does not correspond to any pragma
20873 defined in the Ada standard or to any name defined in
20874 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
20875 this option is treated as turning OFF detection of all unknown pragmas.
20878 Turn OFF detection of all GNAT-specific pragmas
20881 Clear the list of the pragmas to be detected and
20887 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
20888 the syntax of an Ada identifier and therefore can not be considered
20889 as a pragma name, a diagnostic message is generated and the corresponding
20890 parameter is ignored.
20892 When more then one parameter is given in the same rule option, the parameters
20893 must be separated by a comma.
20895 If more then one option for this rule is specified for the @command{gnatcheck}
20896 call, a new option overrides the previous one(s).
20898 The @option{+R} option with no parameters turns the rule ON with the set of
20899 pragmas to be detected defined by the previous rule options.
20900 (By default this set is empty, so if the only option specified for the rule is
20901 @option{+RForbidden_Pragmas} (with
20902 no parameter), then the rule is enabled, but it does not detect anything).
20903 The @option{-R} option with no parameter turns the rule OFF, but it does not
20904 affect the set of pragmas to be detected.
20909 @node Function_Style_Procedures
20910 @subsection @code{Function_Style_Procedures}
20911 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
20914 Flag each procedure that can be rewritten as a function. A procedure can be
20915 converted into a function if it has exactly one parameter of mode @code{out}
20916 and no parameters of mode @code{in out}. Procedure declarations,
20917 formal procedure declarations, and generic procedure declarations are always
20919 bodies and body stubs are flagged only if they do not have corresponding
20920 separate declarations. Procedure renamings and procedure instantiations are
20923 If a procedure can be rewritten as a function, but its @code{out} parameter is
20924 of a limited type, it is not flagged.
20926 Protected procedures are not flagged. Null procedures also are not flagged.
20928 This rule has no parameters.
20931 @node Generics_In_Subprograms
20932 @subsection @code{Generics_In_Subprograms}
20933 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
20936 Flag each declaration of a generic unit in a subprogram. Generic
20937 declarations in the bodies of generic subprograms are also flagged.
20938 A generic unit nested in another generic unit is not flagged.
20939 If a generic unit is
20940 declared in a local package that is declared in a subprogram body, the
20941 generic unit is flagged.
20943 This rule has no parameters.
20946 @node GOTO_Statements
20947 @subsection @code{GOTO_Statements}
20948 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
20951 Flag each occurrence of a @code{goto} statement.
20953 This rule has no parameters.
20956 @node Implicit_IN_Mode_Parameters
20957 @subsection @code{Implicit_IN_Mode_Parameters}
20958 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
20961 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
20962 Note that @code{access} parameters, although they technically behave
20963 like @code{in} parameters, are not flagged.
20965 This rule has no parameters.
20968 @node Implicit_SMALL_For_Fixed_Point_Types
20969 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
20970 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
20973 Flag each fixed point type declaration that lacks an explicit
20974 representation clause to define its @code{'Small} value.
20975 Since @code{'Small} can be defined only for ordinary fixed point types,
20976 decimal fixed point type declarations are not checked.
20978 This rule has no parameters.
20981 @node Improperly_Located_Instantiations
20982 @subsection @code{Improperly_Located_Instantiations}
20983 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
20986 Flag all generic instantiations in library-level package specs
20987 (including library generic packages) and in all subprogram bodies.
20989 Instantiations in task and entry bodies are not flagged. Instantiations in the
20990 bodies of protected subprograms are flagged.
20992 This rule has no parameters.
20996 @node Improper_Returns
20997 @subsection @code{Improper_Returns}
20998 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21001 Flag each explicit @code{return} statement in procedures, and
21002 multiple @code{return} statements in functions.
21003 Diagnostic messages are generated for all @code{return} statements
21004 in a procedure (thus each procedure must be written so that it
21005 returns implicitly at the end of its statement part),
21006 and for all @code{return} statements in a function after the first one.
21007 This rule supports the stylistic convention that each subprogram
21008 should have no more than one point of normal return.
21010 This rule has no parameters.
21013 @node Library_Level_Subprograms
21014 @subsection @code{Library_Level_Subprograms}
21015 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21018 Flag all library-level subprograms (including generic subprogram instantiations).
21020 This rule has no parameters.
21023 @node Local_Packages
21024 @subsection @code{Local_Packages}
21025 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21028 Flag all local packages declared in package and generic package
21030 Local packages in bodies are not flagged.
21032 This rule has no parameters.
21035 @node Improperly_Called_Protected_Entries
21036 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21037 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21040 Flag each protected entry that can be called from more than one task.
21042 This rule has no parameters.
21046 @subsection @code{Metrics}
21047 @cindex @code{Metrics} rule (for @command{gnatcheck})
21050 This is an umbrella rule for a set of metrics-based checks. Each metric-based
21051 check has its own rule name that starts from the common prefix
21052 @code{Metrics_}. For @option{+R} option, this name ends with @code{_GT}
21053 (greater then) or @code{_LT} (less then). The parameter of the rule
21054 @option{+R} option specifies bound (upper or lower, depending on the metric)
21055 for the given metric. A construct is flagged if a specified metric can be
21056 computed for it, and the resulting value is higher then the upper bound (or
21057 less than the lower bound) specified. Parameters and metric names are not
21058 case-sensitive @option{-R} option does not have a parameter and it turns OFF
21059 the check for the metric indicated by the metric rule name.
21061 The following table shows the available metrics-based checks, including the
21062 constraint that must be satisfied by the bound that is specified for the check
21063 and what bound - upper (U) or lower (L) - should be specified.
21065 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21067 @headitem Check Name @tab Description @tab Bounds Value
21070 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21072 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21073 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21074 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21075 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21079 The meaning and the computed values for all these metrics are exactly
21080 the same as for the corresponding metrics in @command{gnatmetric}.
21082 @emph{Example:} the rule
21084 +RMetrics_Cyclomatic_Complexity_GT : 7
21087 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21089 To turn OFF the check for cyclomatic complexity metric, use the following option:
21091 -RMetrics_Cyclomatic_Complexity
21094 @node Misnamed_Identifiers
21095 @subsection @code{Misnamed_Identifiers}
21096 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21099 Flag the declaration of each identifier that does not have a suffix
21100 corresponding to the kind of entity being declared.
21101 The following declarations are checked:
21108 constant declarations (but not number declarations)
21111 package renaming declarations (but not generic package renaming
21116 This rule may have parameters. When used without parameters, the rule enforces
21117 the following checks:
21121 type-defining names end with @code{_T}, unless the type is an access type,
21122 in which case the suffix must be @code{_A}
21124 constant names end with @code{_C}
21126 names defining package renamings end with @code{_R}
21130 For a private or incomplete type declaration the following checks are
21131 made for the defining name suffix:
21135 For an incomplete type declaration: if the corresponding full type
21136 declaration is available, the defining identifier from the full type
21137 declaration is checked, but the defining identifier from the incomplete type
21138 declaration is not; otherwise the defining identifier from the incomplete
21139 type declaration is checked against the suffix specified for type
21143 For a private type declaration (including private extensions), the defining
21144 identifier from the private type declaration is checked against the type
21145 suffix (even if the corresponding full declaration is an access type
21146 declaration), and the defining identifier from the corresponding full type
21147 declaration is not checked.
21151 For a deferred constant, the defining name in the corresponding full constant
21152 declaration is not checked.
21154 Defining names of formal types are not checked.
21156 The rule may have the following parameters:
21160 For the @option{+R} option:
21163 Sets the default listed above for all the names to be checked.
21165 @item Type_Suffix=@emph{string}
21166 Specifies the suffix for a type name.
21168 @item Access_Suffix=@emph{string}
21169 Specifies the suffix for an access type name. If
21170 this parameter is set, it overrides for access
21171 types the suffix set by the @code{Type_Suffix} parameter.
21173 @item Constant_Suffix=@emph{string}
21174 Specifies the suffix for a constant name.
21176 @item Renaming_Suffix=@emph{string}
21177 Specifies the suffix for a package renaming name.
21181 For the @option{-R} option:
21184 Remove all the suffixes specified for the
21185 identifier suffix checks, whether by default or
21186 as specified by other rule parameters. All the
21187 checks for this rule are disabled as a result.
21190 Removes the suffix specified for types. This
21191 disables checks for types but does not disable
21192 any other checks for this rule (including the
21193 check for access type names if @code{Access_Suffix} is
21196 @item Access_Suffix
21197 Removes the suffix specified for access types.
21198 This disables checks for access type names but
21199 does not disable any other checks for this rule.
21200 If @code{Type_Suffix} is set, access type names are
21201 checked as ordinary type names.
21203 @item Constant_Suffix
21204 Removes the suffix specified for constants. This
21205 disables checks for constant names but does not
21206 disable any other checks for this rule.
21208 @item Renaming_Suffix
21209 Removes the suffix specified for package
21210 renamings. This disables checks for package
21211 renamings but does not disable any other checks
21217 If more than one parameter is used, parameters must be separated by commas.
21219 If more than one option is specified for the @command{gnatcheck} invocation,
21220 a new option overrides the previous one(s).
21222 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21224 name suffixes specified by previous options used for this rule.
21226 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21227 all the checks but keeps
21228 all the suffixes specified by previous options used for this rule.
21230 The @emph{string} value must be a valid suffix for an Ada identifier (after
21231 trimming all the leading and trailing space characters, if any).
21232 Parameters are not case sensitive, except the @emph{string} part.
21234 If any error is detected in a rule parameter, the parameter is ignored.
21235 In such a case the options that are set for the rule are not
21240 @node Multiple_Entries_In_Protected_Definitions
21241 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21242 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21245 Flag each protected definition (i.e., each protected object/type declaration)
21246 that defines more than one entry.
21247 Diagnostic messages are generated for all the entry declarations
21248 except the first one. An entry family is counted as one entry. Entries from
21249 the private part of the protected definition are also checked.
21251 This rule has no parameters.
21254 @subsection @code{Name_Clashes}
21255 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21258 Check that certain names are not used as defining identifiers. To activate
21259 this rule, you need to supply a reference to the dictionary file(s) as a rule
21260 parameter(s) (more then one dictionary file can be specified). If no
21261 dictionary file is set, this rule will not cause anything to be flagged.
21262 Only defining occurrences, not references, are checked.
21263 The check is not case-sensitive.
21265 This rule is enabled by default, but without setting any corresponding
21266 dictionary file(s); thus the default effect is to do no checks.
21268 A dictionary file is a plain text file. The maximum line length for this file
21269 is 1024 characters. If the line is longer then this limit, extra characters
21272 Each line can be either an empty line, a comment line, or a line containing
21273 a list of identifiers separated by space or HT characters.
21274 A comment is an Ada-style comment (from @code{--} to end-of-line).
21275 Identifiers must follow the Ada syntax for identifiers.
21276 A line containing one or more identifiers may end with a comment.
21278 @node Non_Qualified_Aggregates
21279 @subsection @code{Non_Qualified_Aggregates}
21280 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21283 Flag each non-qualified aggregate.
21284 A non-qualified aggregate is an
21285 aggregate that is not the expression of a qualified expression. A
21286 string literal is not considered an aggregate, but an array
21287 aggregate of a string type is considered as a normal aggregate.
21288 Aggregates of anonymous array types are not flagged.
21290 This rule has no parameters.
21293 @node Non_Short_Circuit_Operators
21294 @subsection @code{Non_Short_Circuit_Operators}
21295 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21298 Flag all calls to predefined @code{and} and @code{or} operators for
21299 any boolean type. Calls to
21300 user-defined @code{and} and @code{or} and to operators defined by renaming
21301 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21302 operators for modular types or boolean array types are not flagged.
21304 This rule has no parameters.
21308 @node Non_SPARK_Attributes
21309 @subsection @code{Non_SPARK_Attributes}
21310 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21313 The SPARK language defines the following subset of Ada 95 attribute
21314 designators as those that can be used in SPARK programs. The use of
21315 any other attribute is flagged.
21318 @item @code{'Adjacent}
21321 @item @code{'Ceiling}
21322 @item @code{'Component_Size}
21323 @item @code{'Compose}
21324 @item @code{'Copy_Sign}
21325 @item @code{'Delta}
21326 @item @code{'Denorm}
21327 @item @code{'Digits}
21328 @item @code{'Exponent}
21329 @item @code{'First}
21330 @item @code{'Floor}
21332 @item @code{'Fraction}
21334 @item @code{'Leading_Part}
21335 @item @code{'Length}
21336 @item @code{'Machine}
21337 @item @code{'Machine_Emax}
21338 @item @code{'Machine_Emin}
21339 @item @code{'Machine_Mantissa}
21340 @item @code{'Machine_Overflows}
21341 @item @code{'Machine_Radix}
21342 @item @code{'Machine_Rounds}
21345 @item @code{'Model}
21346 @item @code{'Model_Emin}
21347 @item @code{'Model_Epsilon}
21348 @item @code{'Model_Mantissa}
21349 @item @code{'Model_Small}
21350 @item @code{'Modulus}
21353 @item @code{'Range}
21354 @item @code{'Remainder}
21355 @item @code{'Rounding}
21356 @item @code{'Safe_First}
21357 @item @code{'Safe_Last}
21358 @item @code{'Scaling}
21359 @item @code{'Signed_Zeros}
21361 @item @code{'Small}
21363 @item @code{'Truncation}
21364 @item @code{'Unbiased_Rounding}
21366 @item @code{'Valid}
21370 This rule has no parameters.
21373 @node Non_Tagged_Derived_Types
21374 @subsection @code{Non_Tagged_Derived_Types}
21375 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21378 Flag all derived type declarations that do not have a record extension part.
21380 This rule has no parameters.
21384 @node Non_Visible_Exceptions
21385 @subsection @code{Non_Visible_Exceptions}
21386 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21389 Flag constructs leading to the possibility of propagating an exception
21390 out of the scope in which the exception is declared.
21391 Two cases are detected:
21395 An exception declaration in a subprogram body, task body or block
21396 statement is flagged if the body or statement does not contain a handler for
21397 that exception or a handler with an @code{others} choice.
21400 A @code{raise} statement in an exception handler of a subprogram body,
21401 task body or block statement is flagged if it (re)raises a locally
21402 declared exception. This may occur under the following circumstances:
21405 it explicitly raises a locally declared exception, or
21407 it does not specify an exception name (i.e., it is simply @code{raise;})
21408 and the enclosing handler contains a locally declared exception in its
21414 Renamings of local exceptions are not flagged.
21416 This rule has no parameters.
21419 @node Numeric_Literals
21420 @subsection @code{Numeric_Literals}
21421 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21424 Flag each use of a numeric literal in an index expression, and in any
21425 circumstance except for the following:
21429 a literal occurring in the initialization expression for a constant
21430 declaration or a named number declaration, or
21433 an integer literal that is less than or equal to a value
21434 specified by the @option{N} rule parameter.
21438 This rule may have the following parameters for the @option{+R} option:
21442 @emph{N} is an integer literal used as the maximal value that is not flagged
21443 (i.e., integer literals not exceeding this value are allowed)
21446 All integer literals are flagged
21450 If no parameters are set, the maximum unflagged value is 1.
21452 The last specified check limit (or the fact that there is no limit at
21453 all) is used when multiple @option{+R} options appear.
21455 The @option{-R} option for this rule has no parameters.
21456 It disables the rule but retains the last specified maximum unflagged value.
21457 If the @option{+R} option subsequently appears, this value is used as the
21458 threshold for the check.
21461 @node OTHERS_In_Aggregates
21462 @subsection @code{OTHERS_In_Aggregates}
21463 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21466 Flag each use of an @code{others} choice in extension aggregates.
21467 In record and array aggregates, an @code{others} choice is flagged unless
21468 it is used to refer to all components, or to all but one component.
21470 If, in case of a named array aggregate, there are two associations, one
21471 with an @code{others} choice and another with a discrete range, the
21472 @code{others} choice is flagged even if the discrete range specifies
21473 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21475 This rule has no parameters.
21477 @node OTHERS_In_CASE_Statements
21478 @subsection @code{OTHERS_In_CASE_Statements}
21479 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21482 Flag any use of an @code{others} choice in a @code{case} statement.
21484 This rule has no parameters.
21486 @node OTHERS_In_Exception_Handlers
21487 @subsection @code{OTHERS_In_Exception_Handlers}
21488 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
21491 Flag any use of an @code{others} choice in an exception handler.
21493 This rule has no parameters.
21496 @node Outer_Loop_Exits
21497 @subsection @code{Outer_Loop_Exits}
21498 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
21501 Flag each @code{exit} statement containing a loop name that is not the name
21502 of the immediately enclosing @code{loop} statement.
21504 This rule has no parameters.
21507 @node Overloaded_Operators
21508 @subsection @code{Overloaded_Operators}
21509 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
21512 Flag each function declaration that overloads an operator symbol.
21513 A function body is checked only if the body does not have a
21514 separate spec. Formal functions are also checked. For a
21515 renaming declaration, only renaming-as-declaration is checked
21517 This rule has no parameters.
21520 @node Overly_Nested_Control_Structures
21521 @subsection @code{Overly_Nested_Control_Structures}
21522 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
21525 Flag each control structure whose nesting level exceeds the value provided
21526 in the rule parameter.
21528 The control structures checked are the following:
21531 @item @code{if} statement
21532 @item @code{case} statement
21533 @item @code{loop} statement
21534 @item Selective accept statement
21535 @item Timed entry call statement
21536 @item Conditional entry call
21537 @item Asynchronous select statement
21541 The rule has the following parameter for the @option{+R} option:
21545 Positive integer specifying the maximal control structure nesting
21546 level that is not flagged
21550 If the parameter for the @option{+R} option is not specified or
21551 if it is not a positive integer, @option{+R} option is ignored.
21553 If more then one option is specified for the gnatcheck call, the later option and
21554 new parameter override the previous one(s).
21557 @node Parameters_Out_Of_Order
21558 @subsection @code{Parameters_Out_Of_Order}
21559 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
21562 Flag each subprogram and entry declaration whose formal parameters are not
21563 ordered according to the following scheme:
21567 @item @code{in} and @code{access} parameters first,
21568 then @code{in out} parameters,
21569 and then @code{out} parameters;
21571 @item for @code{in} mode, parameters with default initialization expressions
21576 Only the first violation of the described order is flagged.
21578 The following constructs are checked:
21581 @item subprogram declarations (including null procedures);
21582 @item generic subprogram declarations;
21583 @item formal subprogram declarations;
21584 @item entry declarations;
21585 @item subprogram bodies and subprogram body stubs that do not
21586 have separate specifications
21590 Subprogram renamings are not checked.
21592 This rule has no parameters.
21595 @node Positional_Actuals_For_Defaulted_Generic_Parameters
21596 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
21597 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
21600 Flag each generic actual parameter corresponding to a generic formal
21601 parameter with a default initialization, if positional notation is used.
21603 This rule has no parameters.
21605 @node Positional_Actuals_For_Defaulted_Parameters
21606 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
21607 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
21610 Flag each actual parameter to a subprogram or entry call where the
21611 corresponding formal parameter has a default expression, if positional
21614 This rule has no parameters.
21616 @node Positional_Components
21617 @subsection @code{Positional_Components}
21618 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
21621 Flag each array, record and extension aggregate that includes positional
21624 This rule has no parameters.
21627 @node Positional_Generic_Parameters
21628 @subsection @code{Positional_Generic_Parameters}
21629 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
21632 Flag each instantiation using positional parameter notation.
21634 This rule has no parameters.
21637 @node Positional_Parameters
21638 @subsection @code{Positional_Parameters}
21639 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
21642 Flag each subprogram or entry call using positional parameter notation,
21643 except for the following:
21647 Invocations of prefix or infix operators are not flagged
21649 If the called subprogram or entry has only one formal parameter,
21650 the call is not flagged;
21652 If a subprogram call uses the @emph{Object.Operation} notation, then
21655 the first parameter (that is, @emph{Object}) is not flagged;
21657 if the called subprogram has only two parameters, the second parameter
21658 of the call is not flagged;
21663 This rule has no parameters.
21668 @node Predefined_Numeric_Types
21669 @subsection @code{Predefined_Numeric_Types}
21670 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
21673 Flag each explicit use of the name of any numeric type or subtype defined
21674 in package @code{Standard}.
21676 The rationale for this rule is to detect when the
21677 program may depend on platform-specific characteristics of the implementation
21678 of the predefined numeric types. Note that this rule is over-pessimistic;
21679 for example, a program that uses @code{String} indexing
21680 likely needs a variable of type @code{Integer}.
21681 Another example is the flagging of predefined numeric types with explicit
21684 @smallexample @c ada
21685 subtype My_Integer is Integer range Left .. Right;
21686 Vy_Var : My_Integer;
21690 This rule detects only numeric types and subtypes defined in
21691 @code{Standard}. The use of numeric types and subtypes defined in other
21692 predefined packages (such as @code{System.Any_Priority} or
21693 @code{Ada.Text_IO.Count}) is not flagged
21695 This rule has no parameters.
21699 @node Raising_External_Exceptions
21700 @subsection @code{Raising_External_Exceptions}
21701 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
21704 Flag any @code{raise} statement, in a program unit declared in a library
21705 package or in a generic library package, for an exception that is
21706 neither a predefined exception nor an exception that is also declared (or
21707 renamed) in the visible part of the package.
21709 This rule has no parameters.
21713 @node Raising_Predefined_Exceptions
21714 @subsection @code{Raising_Predefined_Exceptions}
21715 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
21718 Flag each @code{raise} statement that raises a predefined exception
21719 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
21720 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
21722 This rule has no parameters.
21724 @node Separate_Numeric_Error_Handlers
21725 @subsection @code{Separate_Numeric_Error_Handlers}
21726 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
21729 Flags each exception handler that contains a choice for
21730 the predefined @code{Constraint_Error} exception, but does not contain
21731 the choice for the predefined @code{Numeric_Error} exception, or
21732 that contains the choice for @code{Numeric_Error}, but does not contain the
21733 choice for @code{Constraint_Error}.
21735 This rule has no parameters.
21739 @subsection @code{Recursion} (under construction, GLOBAL)
21740 @cindex @code{Recursion} rule (for @command{gnatcheck})
21743 Flag recursive subprograms (cycles in the call graph). Declarations, and not
21744 calls, of recursive subprograms are detected.
21746 This rule has no parameters.
21750 @node Side_Effect_Functions
21751 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
21752 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
21755 Flag functions with side effects.
21757 We define a side effect as changing any data object that is not local for the
21758 body of this function.
21760 At the moment, we do NOT consider a side effect any input-output operations
21761 (changing a state or a content of any file).
21763 We do not consider protected functions for this rule (???)
21765 There are the following sources of side effect:
21768 @item Explicit (or direct) side-effect:
21772 direct assignment to a non-local variable;
21775 direct call to an entity that is known to change some data object that is
21776 not local for the body of this function (Note, that if F1 calls F2 and F2
21777 does have a side effect, this does not automatically mean that F1 also
21778 have a side effect, because it may be the case that F2 is declared in
21779 F1's body and it changes some data object that is global for F2, but
21783 @item Indirect side-effect:
21786 Subprogram calls implicitly issued by:
21789 computing initialization expressions from type declarations as a part
21790 of object elaboration or allocator evaluation;
21792 computing implicit parameters of subprogram or entry calls or generic
21797 activation of a task that change some non-local data object (directly or
21801 elaboration code of a package that is a result of a package instantiation;
21804 controlled objects;
21807 @item Situations when we can suspect a side-effect, but the full static check
21808 is either impossible or too hard:
21811 assignment to access variables or to the objects pointed by access
21815 call to a subprogram pointed by access-to-subprogram value
21823 This rule has no parameters.
21827 @subsection @code{Slices}
21828 @cindex @code{Slices} rule (for @command{gnatcheck})
21831 Flag all uses of array slicing
21833 This rule has no parameters.
21836 @node Unassigned_OUT_Parameters
21837 @subsection @code{Unassigned_OUT_Parameters}
21838 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
21841 Flags procedures' @code{out} parameters that are not assigned, and
21842 identifies the contexts in which the assignments are missing.
21844 An @code{out} parameter is flagged in the statements in the procedure
21845 body's handled sequence of statements (before the procedure body's
21846 @code{exception} part, if any) if this sequence of statements contains
21847 no assignments to the parameter.
21849 An @code{out} parameter is flagged in an exception handler in the exception
21850 part of the procedure body's handled sequence of statements if the handler
21851 contains no assignment to the parameter.
21853 Bodies of generic procedures are also considered.
21855 The following are treated as assignments to an @code{out} parameter:
21859 an assignment statement, with the parameter or some component as the target;
21862 passing the parameter (or one of its components) as an @code{out} or
21863 @code{in out} parameter.
21867 This rule does not have any parameters.
21871 @node Uncommented_BEGIN_In_Package_Bodies
21872 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
21873 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
21876 Flags each package body with declarations and a statement part that does not
21877 include a trailing comment on the line containing the @code{begin} keyword;
21878 this trailing comment needs to specify the package name and nothing else.
21879 The @code{begin} is not flagged if the package body does not
21880 contain any declarations.
21882 If the @code{begin} keyword is placed on the
21883 same line as the last declaration or the first statement, it is flagged
21884 independently of whether the line contains a trailing comment. The
21885 diagnostic message is attached to the line containing the first statement.
21887 This rule has no parameters.
21890 @node Unconstrained_Array_Returns
21891 @subsection @code{Unconstrained_Array_Returns}
21892 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
21895 Flag each function returning an unconstrained array. Function declarations,
21896 function bodies (and body stubs) having no separate specifications,
21897 and generic function instantiations are checked.
21898 Generic function declarations, function calls and function renamings are
21901 This rule has no parameters.
21903 @node Universal_Ranges
21904 @subsection @code{Universal_Ranges}
21905 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
21908 Flag discrete ranges that are a part of an index constraint, constrained
21909 array definition, or @code{for}-loop parameter specification, and whose bounds
21910 are both of type @i{universal_integer}. Ranges that have at least one
21911 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
21912 or an expression of non-universal type) are not flagged.
21914 This rule has no parameters.
21917 @node Unnamed_Blocks_And_Loops
21918 @subsection @code{Unnamed_Blocks_And_Loops}
21919 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
21922 Flag each unnamed block statement and loop statement.
21924 The rule has no parameters.
21929 @node Unused_Subprograms
21930 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
21931 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
21934 Flag all unused subprograms.
21936 This rule has no parameters.
21942 @node USE_PACKAGE_Clauses
21943 @subsection @code{USE_PACKAGE_Clauses}
21944 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
21947 Flag all @code{use} clauses for packages; @code{use type} clauses are
21950 This rule has no parameters.
21954 @node Volatile_Objects_Without_Address_Clauses
21955 @subsection @code{Volatile_Objects_Without_Address_Clauses}
21956 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
21959 Flag each volatile object that does not have an address clause.
21961 The following check is made: if the pragma @code{Volatile} is applied to a
21962 data object or to its type, then an address clause must
21963 be supplied for this object.
21965 This rule does not check the components of data objects,
21966 array components that are volatile as a result of the pragma
21967 @code{Volatile_Components}, or objects that are volatile because
21968 they are atomic as a result of pragmas @code{Atomic} or
21969 @code{Atomic_Components}.
21971 Only variable declarations, and not constant declarations, are checked.
21973 This rule has no parameters.
21976 @c *********************************
21977 @node Creating Sample Bodies Using gnatstub
21978 @chapter Creating Sample Bodies Using @command{gnatstub}
21982 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
21983 for library unit declarations.
21985 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
21986 driver (see @ref{The GNAT Driver and Project Files}).
21988 To create a body stub, @command{gnatstub} has to compile the library
21989 unit declaration. Therefore, bodies can be created only for legal
21990 library units. Moreover, if a library unit depends semantically upon
21991 units located outside the current directory, you have to provide
21992 the source search path when calling @command{gnatstub}, see the description
21993 of @command{gnatstub} switches below.
21996 * Running gnatstub::
21997 * Switches for gnatstub::
22000 @node Running gnatstub
22001 @section Running @command{gnatstub}
22004 @command{gnatstub} has the command-line interface of the form
22007 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22014 is the name of the source file that contains a library unit declaration
22015 for which a body must be created. The file name may contain the path
22017 The file name does not have to follow the GNAT file name conventions. If the
22019 does not follow GNAT file naming conventions, the name of the body file must
22021 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22022 If the file name follows the GNAT file naming
22023 conventions and the name of the body file is not provided,
22026 of the body file from the argument file name by replacing the @file{.ads}
22028 with the @file{.adb} suffix.
22031 indicates the directory in which the body stub is to be placed (the default
22036 is an optional sequence of switches as described in the next section
22039 @node Switches for gnatstub
22040 @section Switches for @command{gnatstub}
22046 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22047 If the destination directory already contains a file with the name of the
22049 for the argument spec file, replace it with the generated body stub.
22051 @item ^-hs^/HEADER=SPEC^
22052 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22053 Put the comment header (i.e., all the comments preceding the
22054 compilation unit) from the source of the library unit declaration
22055 into the body stub.
22057 @item ^-hg^/HEADER=GENERAL^
22058 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22059 Put a sample comment header into the body stub.
22061 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22062 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22063 Use the content of the file as the comment header for a generated body stub.
22067 @cindex @option{-IDIR} (@command{gnatstub})
22069 @cindex @option{-I-} (@command{gnatstub})
22072 @item /NOCURRENT_DIRECTORY
22073 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22075 ^These switches have ^This switch has^ the same meaning as in calls to
22077 ^They define ^It defines ^ the source search path in the call to
22078 @command{gcc} issued
22079 by @command{gnatstub} to compile an argument source file.
22081 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22082 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22083 This switch has the same meaning as in calls to @command{gcc}.
22084 It defines the additional configuration file to be passed to the call to
22085 @command{gcc} issued
22086 by @command{gnatstub} to compile an argument source file.
22088 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22089 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22090 (@var{n} is a non-negative integer). Set the maximum line length in the
22091 body stub to @var{n}; the default is 79. The maximum value that can be
22092 specified is 32767. Note that in the special case of configuration
22093 pragma files, the maximum is always 32767 regardless of whether or
22094 not this switch appears.
22096 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22097 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22098 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22099 the generated body sample to @var{n}.
22100 The default indentation is 3.
22102 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22103 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22104 Order local bodies alphabetically. (By default local bodies are ordered
22105 in the same way as the corresponding local specs in the argument spec file.)
22107 @item ^-i^/INDENTATION=^@var{n}
22108 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22109 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22111 @item ^-k^/TREE_FILE=SAVE^
22112 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22113 Do not remove the tree file (i.e., the snapshot of the compiler internal
22114 structures used by @command{gnatstub}) after creating the body stub.
22116 @item ^-l^/LINE_LENGTH=^@var{n}
22117 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22118 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22120 @item ^-o^/BODY=^@var{body-name}
22121 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22122 Body file name. This should be set if the argument file name does not
22124 the GNAT file naming
22125 conventions. If this switch is omitted the default name for the body will be
22127 from the argument file name according to the GNAT file naming conventions.
22130 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22131 Quiet mode: do not generate a confirmation when a body is
22132 successfully created, and do not generate a message when a body is not
22136 @item ^-r^/TREE_FILE=REUSE^
22137 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22138 Reuse the tree file (if it exists) instead of creating it. Instead of
22139 creating the tree file for the library unit declaration, @command{gnatstub}
22140 tries to find it in the current directory and use it for creating
22141 a body. If the tree file is not found, no body is created. This option
22142 also implies @option{^-k^/SAVE^}, whether or not
22143 the latter is set explicitly.
22145 @item ^-t^/TREE_FILE=OVERWRITE^
22146 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22147 Overwrite the existing tree file. If the current directory already
22148 contains the file which, according to the GNAT file naming rules should
22149 be considered as a tree file for the argument source file,
22151 will refuse to create the tree file needed to create a sample body
22152 unless this option is set.
22154 @item ^-v^/VERBOSE^
22155 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22156 Verbose mode: generate version information.
22160 @node Other Utility Programs
22161 @chapter Other Utility Programs
22164 This chapter discusses some other utility programs available in the Ada
22168 * Using Other Utility Programs with GNAT::
22169 * The External Symbol Naming Scheme of GNAT::
22170 * Converting Ada Files to html with gnathtml::
22171 * Installing gnathtml::
22178 @node Using Other Utility Programs with GNAT
22179 @section Using Other Utility Programs with GNAT
22182 The object files generated by GNAT are in standard system format and in
22183 particular the debugging information uses this format. This means
22184 programs generated by GNAT can be used with existing utilities that
22185 depend on these formats.
22188 In general, any utility program that works with C will also often work with
22189 Ada programs generated by GNAT. This includes software utilities such as
22190 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22194 @node The External Symbol Naming Scheme of GNAT
22195 @section The External Symbol Naming Scheme of GNAT
22198 In order to interpret the output from GNAT, when using tools that are
22199 originally intended for use with other languages, it is useful to
22200 understand the conventions used to generate link names from the Ada
22203 All link names are in all lowercase letters. With the exception of library
22204 procedure names, the mechanism used is simply to use the full expanded
22205 Ada name with dots replaced by double underscores. For example, suppose
22206 we have the following package spec:
22208 @smallexample @c ada
22219 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22220 the corresponding link name is @code{qrs__mn}.
22222 Of course if a @code{pragma Export} is used this may be overridden:
22224 @smallexample @c ada
22229 pragma Export (Var1, C, External_Name => "var1_name");
22231 pragma Export (Var2, C, Link_Name => "var2_link_name");
22238 In this case, the link name for @var{Var1} is whatever link name the
22239 C compiler would assign for the C function @var{var1_name}. This typically
22240 would be either @var{var1_name} or @var{_var1_name}, depending on operating
22241 system conventions, but other possibilities exist. The link name for
22242 @var{Var2} is @var{var2_link_name}, and this is not operating system
22246 One exception occurs for library level procedures. A potential ambiguity
22247 arises between the required name @code{_main} for the C main program,
22248 and the name we would otherwise assign to an Ada library level procedure
22249 called @code{Main} (which might well not be the main program).
22251 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
22252 names. So if we have a library level procedure such as
22254 @smallexample @c ada
22257 procedure Hello (S : String);
22263 the external name of this procedure will be @var{_ada_hello}.
22266 @node Converting Ada Files to html with gnathtml
22267 @section Converting Ada Files to HTML with @code{gnathtml}
22270 This @code{Perl} script allows Ada source files to be browsed using
22271 standard Web browsers. For installation procedure, see the section
22272 @xref{Installing gnathtml}.
22274 Ada reserved keywords are highlighted in a bold font and Ada comments in
22275 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
22276 switch to suppress the generation of cross-referencing information, user
22277 defined variables and types will appear in a different color; you will
22278 be able to click on any identifier and go to its declaration.
22280 The command line is as follow:
22282 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
22286 You can pass it as many Ada files as you want. @code{gnathtml} will generate
22287 an html file for every ada file, and a global file called @file{index.htm}.
22288 This file is an index of every identifier defined in the files.
22290 The available ^switches^options^ are the following ones:
22294 @cindex @option{-83} (@code{gnathtml})
22295 Only the Ada 83 subset of keywords will be highlighted.
22297 @item -cc @var{color}
22298 @cindex @option{-cc} (@code{gnathtml})
22299 This option allows you to change the color used for comments. The default
22300 value is green. The color argument can be any name accepted by html.
22303 @cindex @option{-d} (@code{gnathtml})
22304 If the Ada files depend on some other files (for instance through
22305 @code{with} clauses, the latter files will also be converted to html.
22306 Only the files in the user project will be converted to html, not the files
22307 in the run-time library itself.
22310 @cindex @option{-D} (@code{gnathtml})
22311 This command is the same as @option{-d} above, but @command{gnathtml} will
22312 also look for files in the run-time library, and generate html files for them.
22314 @item -ext @var{extension}
22315 @cindex @option{-ext} (@code{gnathtml})
22316 This option allows you to change the extension of the generated HTML files.
22317 If you do not specify an extension, it will default to @file{htm}.
22320 @cindex @option{-f} (@code{gnathtml})
22321 By default, gnathtml will generate html links only for global entities
22322 ('with'ed units, global variables and types,@dots{}). If you specify
22323 @option{-f} on the command line, then links will be generated for local
22326 @item -l @var{number}
22327 @cindex @option{-l} (@code{gnathtml})
22328 If this ^switch^option^ is provided and @var{number} is not 0, then
22329 @code{gnathtml} will number the html files every @var{number} line.
22332 @cindex @option{-I} (@code{gnathtml})
22333 Specify a directory to search for library files (@file{.ALI} files) and
22334 source files. You can provide several -I switches on the command line,
22335 and the directories will be parsed in the order of the command line.
22338 @cindex @option{-o} (@code{gnathtml})
22339 Specify the output directory for html files. By default, gnathtml will
22340 saved the generated html files in a subdirectory named @file{html/}.
22342 @item -p @var{file}
22343 @cindex @option{-p} (@code{gnathtml})
22344 If you are using Emacs and the most recent Emacs Ada mode, which provides
22345 a full Integrated Development Environment for compiling, checking,
22346 running and debugging applications, you may use @file{.gpr} files
22347 to give the directories where Emacs can find sources and object files.
22349 Using this ^switch^option^, you can tell gnathtml to use these files.
22350 This allows you to get an html version of your application, even if it
22351 is spread over multiple directories.
22353 @item -sc @var{color}
22354 @cindex @option{-sc} (@code{gnathtml})
22355 This ^switch^option^ allows you to change the color used for symbol
22357 The default value is red. The color argument can be any name accepted by html.
22359 @item -t @var{file}
22360 @cindex @option{-t} (@code{gnathtml})
22361 This ^switch^option^ provides the name of a file. This file contains a list of
22362 file names to be converted, and the effect is exactly as though they had
22363 appeared explicitly on the command line. This
22364 is the recommended way to work around the command line length limit on some
22369 @node Installing gnathtml
22370 @section Installing @code{gnathtml}
22373 @code{Perl} needs to be installed on your machine to run this script.
22374 @code{Perl} is freely available for almost every architecture and
22375 Operating System via the Internet.
22377 On Unix systems, you may want to modify the first line of the script
22378 @code{gnathtml}, to explicitly tell the Operating system where Perl
22379 is. The syntax of this line is:
22381 #!full_path_name_to_perl
22385 Alternatively, you may run the script using the following command line:
22388 $ perl gnathtml.pl @ovar{switches} @var{files}
22397 The GNAT distribution provides an Ada 95 template for the HP Language
22398 Sensitive Editor (LSE), a component of DECset. In order to
22399 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
22406 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
22407 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
22408 the collection phase with the /DEBUG qualifier.
22411 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
22412 $ DEFINE LIB$DEBUG PCA$COLLECTOR
22413 $ RUN/DEBUG <PROGRAM_NAME>
22419 @c ******************************
22420 @node Code Coverage and Profiling
22421 @chapter Code Coverage and Profiling
22422 @cindex Code Coverage
22426 This chapter describes how to use @code{gcov} - coverage testing tool - and
22427 @code{gprof} - profiler tool - on your Ada programs.
22430 * Code Coverage of Ada Programs using gcov::
22431 * Profiling an Ada Program using gprof::
22434 @node Code Coverage of Ada Programs using gcov
22435 @section Code Coverage of Ada Programs using gcov
22437 @cindex -fprofile-arcs
22438 @cindex -ftest-coverage
22440 @cindex Code Coverage
22443 @code{gcov} is a test coverage program: it analyzes the execution of a given
22444 program on selected tests, to help you determine the portions of the program
22445 that are still untested.
22447 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
22448 User's Guide. You can refer to this documentation for a more complete
22451 This chapter provides a quick startup guide, and
22452 details some Gnat-specific features.
22455 * Quick startup guide::
22459 @node Quick startup guide
22460 @subsection Quick startup guide
22462 In order to perform coverage analysis of a program using @code{gcov}, 3
22467 Code instrumentation during the compilation process
22469 Execution of the instrumented program
22471 Execution of the @code{gcov} tool to generate the result.
22474 The code instrumentation needed by gcov is created at the object level:
22475 The source code is not modified in any way, because the instrumentation code is
22476 inserted by gcc during the compilation process. To compile your code with code
22477 coverage activated, you need to recompile your whole project using the
22479 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
22480 @code{-fprofile-arcs}.
22483 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
22484 -largs -fprofile-arcs
22487 This compilation process will create @file{.gcno} files together with
22488 the usual object files.
22490 Once the program is compiled with coverage instrumentation, you can
22491 run it as many times as needed - on portions of a test suite for
22492 example. The first execution will produce @file{.gcda} files at the
22493 same location as the @file{.gcno} files. The following executions
22494 will update those files, so that a cumulative result of the covered
22495 portions of the program is generated.
22497 Finally, you need to call the @code{gcov} tool. The different options of
22498 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
22500 This will create annotated source files with a @file{.gcov} extension:
22501 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
22503 @node Gnat specifics
22504 @subsection Gnat specifics
22506 Because Ada semantics, portions of the source code may be shared among
22507 several object files. This is the case for example when generics are
22508 involved, when inlining is active or when declarations generate initialisation
22509 calls. In order to take
22510 into account this shared code, you need to call @code{gcov} on all
22511 source files of the tested program at once.
22513 The list of source files might exceed the system's maximum command line
22514 length. In order to bypass this limitation, a new mechanism has been
22515 implemented in @code{gcov}: you can now list all your project's files into a
22516 text file, and provide this file to gcov as a parameter, preceded by a @@
22517 (e.g. @samp{gcov @@mysrclist.txt}).
22519 @node Profiling an Ada Program using gprof
22520 @section Profiling an Ada Program using gprof
22526 This section is not meant to be an exhaustive documentation of @code{gprof}.
22527 Full documentation for it can be found in the GNU Profiler User's Guide
22528 documentation that is part of this GNAT distribution.
22530 Profiling a program helps determine the parts of a program that are executed
22531 most often, and are therefore the most time-consuming.
22533 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
22534 better handle Ada programs and multitasking.
22535 It is currently supported on the following platforms
22540 solaris sparc/sparc64/x86
22546 In order to profile a program using @code{gprof}, 3 steps are needed:
22550 Code instrumentation, requiring a full recompilation of the project with the
22553 Execution of the program under the analysis conditions, i.e. with the desired
22556 Analysis of the results using the @code{gprof} tool.
22560 The following sections detail the different steps, and indicate how
22561 to interpret the results:
22563 * Compilation for profiling::
22564 * Program execution::
22566 * Interpretation of profiling results::
22569 @node Compilation for profiling
22570 @subsection Compilation for profiling
22574 In order to profile a program the first step is to tell the compiler
22575 to generate the necessary profiling information. The compiler switch to be used
22576 is @code{-pg}, which must be added to other compilation switches. This
22577 switch needs to be specified both during compilation and link stages, and can
22578 be specified once when using gnatmake:
22581 gnatmake -f -pg -P my_project
22585 Note that only the objects that were compiled with the @samp{-pg} switch will be
22586 profiled; if you need to profile your whole project, use the
22587 @samp{-f} gnatmake switch to force full recompilation.
22589 @node Program execution
22590 @subsection Program execution
22593 Once the program has been compiled for profiling, you can run it as usual.
22595 The only constraint imposed by profiling is that the program must terminate
22596 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
22599 Once the program completes execution, a data file called @file{gmon.out} is
22600 generated in the directory where the program was launched from. If this file
22601 already exists, it will be overwritten.
22603 @node Running gprof
22604 @subsection Running gprof
22607 The @code{gprof} tool is called as follow:
22610 gprof my_prog gmon.out
22621 The complete form of the gprof command line is the following:
22624 gprof [^switches^options^] [executable [data-file]]
22628 @code{gprof} supports numerous ^switch^options^. The order of these
22629 ^switch^options^ does not matter. The full list of options can be found in
22630 the GNU Profiler User's Guide documentation that comes with this documentation.
22632 The following is the subset of those switches that is most relevant:
22636 @item --demangle[=@var{style}]
22637 @itemx --no-demangle
22638 @cindex @option{--demangle} (@code{gprof})
22639 These options control whether symbol names should be demangled when
22640 printing output. The default is to demangle C++ symbols. The
22641 @code{--no-demangle} option may be used to turn off demangling. Different
22642 compilers have different mangling styles. The optional demangling style
22643 argument can be used to choose an appropriate demangling style for your
22644 compiler, in particular Ada symbols generated by GNAT can be demangled using
22645 @code{--demangle=gnat}.
22647 @item -e @var{function_name}
22648 @cindex @option{-e} (@code{gprof})
22649 The @samp{-e @var{function}} option tells @code{gprof} not to print
22650 information about the function @var{function_name} (and its
22651 children@dots{}) in the call graph. The function will still be listed
22652 as a child of any functions that call it, but its index number will be
22653 shown as @samp{[not printed]}. More than one @samp{-e} option may be
22654 given; only one @var{function_name} may be indicated with each @samp{-e}
22657 @item -E @var{function_name}
22658 @cindex @option{-E} (@code{gprof})
22659 The @code{-E @var{function}} option works like the @code{-e} option, but
22660 execution time spent in the function (and children who were not called from
22661 anywhere else), will not be used to compute the percentages-of-time for
22662 the call graph. More than one @samp{-E} option may be given; only one
22663 @var{function_name} may be indicated with each @samp{-E} option.
22665 @item -f @var{function_name}
22666 @cindex @option{-f} (@code{gprof})
22667 The @samp{-f @var{function}} option causes @code{gprof} to limit the
22668 call graph to the function @var{function_name} and its children (and
22669 their children@dots{}). More than one @samp{-f} option may be given;
22670 only one @var{function_name} may be indicated with each @samp{-f}
22673 @item -F @var{function_name}
22674 @cindex @option{-F} (@code{gprof})
22675 The @samp{-F @var{function}} option works like the @code{-f} option, but
22676 only time spent in the function and its children (and their
22677 children@dots{}) will be used to determine total-time and
22678 percentages-of-time for the call graph. More than one @samp{-F} option
22679 may be given; only one @var{function_name} may be indicated with each
22680 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
22684 @node Interpretation of profiling results
22685 @subsection Interpretation of profiling results
22689 The results of the profiling analysis are represented by two arrays: the
22690 'flat profile' and the 'call graph'. Full documentation of those outputs
22691 can be found in the GNU Profiler User's Guide.
22693 The flat profile shows the time spent in each function of the program, and how
22694 many time it has been called. This allows you to locate easily the most
22695 time-consuming functions.
22697 The call graph shows, for each subprogram, the subprograms that call it,
22698 and the subprograms that it calls. It also provides an estimate of the time
22699 spent in each of those callers/called subprograms.
22702 @c ******************************
22703 @node Running and Debugging Ada Programs
22704 @chapter Running and Debugging Ada Programs
22708 This chapter discusses how to debug Ada programs.
22710 It applies to GNAT on the Alpha OpenVMS platform;
22711 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
22712 since HP has implemented Ada support in the OpenVMS debugger on I64.
22715 An incorrect Ada program may be handled in three ways by the GNAT compiler:
22719 The illegality may be a violation of the static semantics of Ada. In
22720 that case GNAT diagnoses the constructs in the program that are illegal.
22721 It is then a straightforward matter for the user to modify those parts of
22725 The illegality may be a violation of the dynamic semantics of Ada. In
22726 that case the program compiles and executes, but may generate incorrect
22727 results, or may terminate abnormally with some exception.
22730 When presented with a program that contains convoluted errors, GNAT
22731 itself may terminate abnormally without providing full diagnostics on
22732 the incorrect user program.
22736 * The GNAT Debugger GDB::
22738 * Introduction to GDB Commands::
22739 * Using Ada Expressions::
22740 * Calling User-Defined Subprograms::
22741 * Using the Next Command in a Function::
22744 * Debugging Generic Units::
22745 * GNAT Abnormal Termination or Failure to Terminate::
22746 * Naming Conventions for GNAT Source Files::
22747 * Getting Internal Debugging Information::
22748 * Stack Traceback::
22754 @node The GNAT Debugger GDB
22755 @section The GNAT Debugger GDB
22758 @code{GDB} is a general purpose, platform-independent debugger that
22759 can be used to debug mixed-language programs compiled with @command{gcc},
22760 and in particular is capable of debugging Ada programs compiled with
22761 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
22762 complex Ada data structures.
22764 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
22766 located in the GNU:[DOCS] directory,
22768 for full details on the usage of @code{GDB}, including a section on
22769 its usage on programs. This manual should be consulted for full
22770 details. The section that follows is a brief introduction to the
22771 philosophy and use of @code{GDB}.
22773 When GNAT programs are compiled, the compiler optionally writes debugging
22774 information into the generated object file, including information on
22775 line numbers, and on declared types and variables. This information is
22776 separate from the generated code. It makes the object files considerably
22777 larger, but it does not add to the size of the actual executable that
22778 will be loaded into memory, and has no impact on run-time performance. The
22779 generation of debug information is triggered by the use of the
22780 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
22781 used to carry out the compilations. It is important to emphasize that
22782 the use of these options does not change the generated code.
22784 The debugging information is written in standard system formats that
22785 are used by many tools, including debuggers and profilers. The format
22786 of the information is typically designed to describe C types and
22787 semantics, but GNAT implements a translation scheme which allows full
22788 details about Ada types and variables to be encoded into these
22789 standard C formats. Details of this encoding scheme may be found in
22790 the file exp_dbug.ads in the GNAT source distribution. However, the
22791 details of this encoding are, in general, of no interest to a user,
22792 since @code{GDB} automatically performs the necessary decoding.
22794 When a program is bound and linked, the debugging information is
22795 collected from the object files, and stored in the executable image of
22796 the program. Again, this process significantly increases the size of
22797 the generated executable file, but it does not increase the size of
22798 the executable program itself. Furthermore, if this program is run in
22799 the normal manner, it runs exactly as if the debug information were
22800 not present, and takes no more actual memory.
22802 However, if the program is run under control of @code{GDB}, the
22803 debugger is activated. The image of the program is loaded, at which
22804 point it is ready to run. If a run command is given, then the program
22805 will run exactly as it would have if @code{GDB} were not present. This
22806 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
22807 entirely non-intrusive until a breakpoint is encountered. If no
22808 breakpoint is ever hit, the program will run exactly as it would if no
22809 debugger were present. When a breakpoint is hit, @code{GDB} accesses
22810 the debugging information and can respond to user commands to inspect
22811 variables, and more generally to report on the state of execution.
22815 @section Running GDB
22818 This section describes how to initiate the debugger.
22819 @c The above sentence is really just filler, but it was otherwise
22820 @c clumsy to get the first paragraph nonindented given the conditional
22821 @c nature of the description
22824 The debugger can be launched from a @code{GPS} menu or
22825 directly from the command line. The description below covers the latter use.
22826 All the commands shown can be used in the @code{GPS} debug console window,
22827 but there are usually more GUI-based ways to achieve the same effect.
22830 The command to run @code{GDB} is
22833 $ ^gdb program^GDB PROGRAM^
22837 where @code{^program^PROGRAM^} is the name of the executable file. This
22838 activates the debugger and results in a prompt for debugger commands.
22839 The simplest command is simply @code{run}, which causes the program to run
22840 exactly as if the debugger were not present. The following section
22841 describes some of the additional commands that can be given to @code{GDB}.
22843 @c *******************************
22844 @node Introduction to GDB Commands
22845 @section Introduction to GDB Commands
22848 @code{GDB} contains a large repertoire of commands. @xref{Top,,
22849 Debugging with GDB, gdb, Debugging with GDB},
22851 located in the GNU:[DOCS] directory,
22853 for extensive documentation on the use
22854 of these commands, together with examples of their use. Furthermore,
22855 the command @command{help} invoked from within GDB activates a simple help
22856 facility which summarizes the available commands and their options.
22857 In this section we summarize a few of the most commonly
22858 used commands to give an idea of what @code{GDB} is about. You should create
22859 a simple program with debugging information and experiment with the use of
22860 these @code{GDB} commands on the program as you read through the
22864 @item set args @var{arguments}
22865 The @var{arguments} list above is a list of arguments to be passed to
22866 the program on a subsequent run command, just as though the arguments
22867 had been entered on a normal invocation of the program. The @code{set args}
22868 command is not needed if the program does not require arguments.
22871 The @code{run} command causes execution of the program to start from
22872 the beginning. If the program is already running, that is to say if
22873 you are currently positioned at a breakpoint, then a prompt will ask
22874 for confirmation that you want to abandon the current execution and
22877 @item breakpoint @var{location}
22878 The breakpoint command sets a breakpoint, that is to say a point at which
22879 execution will halt and @code{GDB} will await further
22880 commands. @var{location} is
22881 either a line number within a file, given in the format @code{file:linenumber},
22882 or it is the name of a subprogram. If you request that a breakpoint be set on
22883 a subprogram that is overloaded, a prompt will ask you to specify on which of
22884 those subprograms you want to breakpoint. You can also
22885 specify that all of them should be breakpointed. If the program is run
22886 and execution encounters the breakpoint, then the program
22887 stops and @code{GDB} signals that the breakpoint was encountered by
22888 printing the line of code before which the program is halted.
22890 @item breakpoint exception @var{name}
22891 A special form of the breakpoint command which breakpoints whenever
22892 exception @var{name} is raised.
22893 If @var{name} is omitted,
22894 then a breakpoint will occur when any exception is raised.
22896 @item print @var{expression}
22897 This will print the value of the given expression. Most simple
22898 Ada expression formats are properly handled by @code{GDB}, so the expression
22899 can contain function calls, variables, operators, and attribute references.
22902 Continues execution following a breakpoint, until the next breakpoint or the
22903 termination of the program.
22906 Executes a single line after a breakpoint. If the next statement
22907 is a subprogram call, execution continues into (the first statement of)
22908 the called subprogram.
22911 Executes a single line. If this line is a subprogram call, executes and
22912 returns from the call.
22915 Lists a few lines around the current source location. In practice, it
22916 is usually more convenient to have a separate edit window open with the
22917 relevant source file displayed. Successive applications of this command
22918 print subsequent lines. The command can be given an argument which is a
22919 line number, in which case it displays a few lines around the specified one.
22922 Displays a backtrace of the call chain. This command is typically
22923 used after a breakpoint has occurred, to examine the sequence of calls that
22924 leads to the current breakpoint. The display includes one line for each
22925 activation record (frame) corresponding to an active subprogram.
22928 At a breakpoint, @code{GDB} can display the values of variables local
22929 to the current frame. The command @code{up} can be used to
22930 examine the contents of other active frames, by moving the focus up
22931 the stack, that is to say from callee to caller, one frame at a time.
22934 Moves the focus of @code{GDB} down from the frame currently being
22935 examined to the frame of its callee (the reverse of the previous command),
22937 @item frame @var{n}
22938 Inspect the frame with the given number. The value 0 denotes the frame
22939 of the current breakpoint, that is to say the top of the call stack.
22944 The above list is a very short introduction to the commands that
22945 @code{GDB} provides. Important additional capabilities, including conditional
22946 breakpoints, the ability to execute command sequences on a breakpoint,
22947 the ability to debug at the machine instruction level and many other
22948 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
22949 Debugging with GDB}. Note that most commands can be abbreviated
22950 (for example, c for continue, bt for backtrace).
22952 @node Using Ada Expressions
22953 @section Using Ada Expressions
22954 @cindex Ada expressions
22957 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
22958 extensions. The philosophy behind the design of this subset is
22962 That @code{GDB} should provide basic literals and access to operations for
22963 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
22964 leaving more sophisticated computations to subprograms written into the
22965 program (which therefore may be called from @code{GDB}).
22968 That type safety and strict adherence to Ada language restrictions
22969 are not particularly important to the @code{GDB} user.
22972 That brevity is important to the @code{GDB} user.
22976 Thus, for brevity, the debugger acts as if there were
22977 implicit @code{with} and @code{use} clauses in effect for all user-written
22978 packages, thus making it unnecessary to fully qualify most names with
22979 their packages, regardless of context. Where this causes ambiguity,
22980 @code{GDB} asks the user's intent.
22982 For details on the supported Ada syntax, see @ref{Top,, Debugging with
22983 GDB, gdb, Debugging with GDB}.
22985 @node Calling User-Defined Subprograms
22986 @section Calling User-Defined Subprograms
22989 An important capability of @code{GDB} is the ability to call user-defined
22990 subprograms while debugging. This is achieved simply by entering
22991 a subprogram call statement in the form:
22994 call subprogram-name (parameters)
22998 The keyword @code{call} can be omitted in the normal case where the
22999 @code{subprogram-name} does not coincide with any of the predefined
23000 @code{GDB} commands.
23002 The effect is to invoke the given subprogram, passing it the
23003 list of parameters that is supplied. The parameters can be expressions and
23004 can include variables from the program being debugged. The
23005 subprogram must be defined
23006 at the library level within your program, and @code{GDB} will call the
23007 subprogram within the environment of your program execution (which
23008 means that the subprogram is free to access or even modify variables
23009 within your program).
23011 The most important use of this facility is in allowing the inclusion of
23012 debugging routines that are tailored to particular data structures
23013 in your program. Such debugging routines can be written to provide a suitably
23014 high-level description of an abstract type, rather than a low-level dump
23015 of its physical layout. After all, the standard
23016 @code{GDB print} command only knows the physical layout of your
23017 types, not their abstract meaning. Debugging routines can provide information
23018 at the desired semantic level and are thus enormously useful.
23020 For example, when debugging GNAT itself, it is crucial to have access to
23021 the contents of the tree nodes used to represent the program internally.
23022 But tree nodes are represented simply by an integer value (which in turn
23023 is an index into a table of nodes).
23024 Using the @code{print} command on a tree node would simply print this integer
23025 value, which is not very useful. But the PN routine (defined in file
23026 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23027 a useful high level representation of the tree node, which includes the
23028 syntactic category of the node, its position in the source, the integers
23029 that denote descendant nodes and parent node, as well as varied
23030 semantic information. To study this example in more detail, you might want to
23031 look at the body of the PN procedure in the stated file.
23033 @node Using the Next Command in a Function
23034 @section Using the Next Command in a Function
23037 When you use the @code{next} command in a function, the current source
23038 location will advance to the next statement as usual. A special case
23039 arises in the case of a @code{return} statement.
23041 Part of the code for a return statement is the ``epilog'' of the function.
23042 This is the code that returns to the caller. There is only one copy of
23043 this epilog code, and it is typically associated with the last return
23044 statement in the function if there is more than one return. In some
23045 implementations, this epilog is associated with the first statement
23048 The result is that if you use the @code{next} command from a return
23049 statement that is not the last return statement of the function you
23050 may see a strange apparent jump to the last return statement or to
23051 the start of the function. You should simply ignore this odd jump.
23052 The value returned is always that from the first return statement
23053 that was stepped through.
23055 @node Ada Exceptions
23056 @section Breaking on Ada Exceptions
23060 You can set breakpoints that trip when your program raises
23061 selected exceptions.
23064 @item break exception
23065 Set a breakpoint that trips whenever (any task in the) program raises
23068 @item break exception @var{name}
23069 Set a breakpoint that trips whenever (any task in the) program raises
23070 the exception @var{name}.
23072 @item break exception unhandled
23073 Set a breakpoint that trips whenever (any task in the) program raises an
23074 exception for which there is no handler.
23076 @item info exceptions
23077 @itemx info exceptions @var{regexp}
23078 The @code{info exceptions} command permits the user to examine all defined
23079 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23080 argument, prints out only those exceptions whose name matches @var{regexp}.
23088 @code{GDB} allows the following task-related commands:
23092 This command shows a list of current Ada tasks, as in the following example:
23099 ID TID P-ID Thread Pri State Name
23100 1 8088000 0 807e000 15 Child Activation Wait main_task
23101 2 80a4000 1 80ae000 15 Accept/Select Wait b
23102 3 809a800 1 80a4800 15 Child Activation Wait a
23103 * 4 80ae800 3 80b8000 15 Running c
23107 In this listing, the asterisk before the first task indicates it to be the
23108 currently running task. The first column lists the task ID that is used
23109 to refer to tasks in the following commands.
23111 @item break @var{linespec} task @var{taskid}
23112 @itemx break @var{linespec} task @var{taskid} if @dots{}
23113 @cindex Breakpoints and tasks
23114 These commands are like the @code{break @dots{} thread @dots{}}.
23115 @var{linespec} specifies source lines.
23117 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23118 to specify that you only want @code{GDB} to stop the program when a
23119 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23120 numeric task identifiers assigned by @code{GDB}, shown in the first
23121 column of the @samp{info tasks} display.
23123 If you do not specify @samp{task @var{taskid}} when you set a
23124 breakpoint, the breakpoint applies to @emph{all} tasks of your
23127 You can use the @code{task} qualifier on conditional breakpoints as
23128 well; in this case, place @samp{task @var{taskid}} before the
23129 breakpoint condition (before the @code{if}).
23131 @item task @var{taskno}
23132 @cindex Task switching
23134 This command allows to switch to the task referred by @var{taskno}. In
23135 particular, This allows to browse the backtrace of the specified
23136 task. It is advised to switch back to the original task before
23137 continuing execution otherwise the scheduling of the program may be
23142 For more detailed information on the tasking support,
23143 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23145 @node Debugging Generic Units
23146 @section Debugging Generic Units
23147 @cindex Debugging Generic Units
23151 GNAT always uses code expansion for generic instantiation. This means that
23152 each time an instantiation occurs, a complete copy of the original code is
23153 made, with appropriate substitutions of formals by actuals.
23155 It is not possible to refer to the original generic entities in
23156 @code{GDB}, but it is always possible to debug a particular instance of
23157 a generic, by using the appropriate expanded names. For example, if we have
23159 @smallexample @c ada
23164 generic package k is
23165 procedure kp (v1 : in out integer);
23169 procedure kp (v1 : in out integer) is
23175 package k1 is new k;
23176 package k2 is new k;
23178 var : integer := 1;
23191 Then to break on a call to procedure kp in the k2 instance, simply
23195 (gdb) break g.k2.kp
23199 When the breakpoint occurs, you can step through the code of the
23200 instance in the normal manner and examine the values of local variables, as for
23203 @node GNAT Abnormal Termination or Failure to Terminate
23204 @section GNAT Abnormal Termination or Failure to Terminate
23205 @cindex GNAT Abnormal Termination or Failure to Terminate
23208 When presented with programs that contain serious errors in syntax
23210 GNAT may on rare occasions experience problems in operation, such
23212 segmentation fault or illegal memory access, raising an internal
23213 exception, terminating abnormally, or failing to terminate at all.
23214 In such cases, you can activate
23215 various features of GNAT that can help you pinpoint the construct in your
23216 program that is the likely source of the problem.
23218 The following strategies are presented in increasing order of
23219 difficulty, corresponding to your experience in using GNAT and your
23220 familiarity with compiler internals.
23224 Run @command{gcc} with the @option{-gnatf}. This first
23225 switch causes all errors on a given line to be reported. In its absence,
23226 only the first error on a line is displayed.
23228 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23229 are encountered, rather than after compilation is terminated. If GNAT
23230 terminates prematurely or goes into an infinite loop, the last error
23231 message displayed may help to pinpoint the culprit.
23234 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
23235 mode, @command{gcc} produces ongoing information about the progress of the
23236 compilation and provides the name of each procedure as code is
23237 generated. This switch allows you to find which Ada procedure was being
23238 compiled when it encountered a code generation problem.
23241 @cindex @option{-gnatdc} switch
23242 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
23243 switch that does for the front-end what @option{^-v^VERBOSE^} does
23244 for the back end. The system prints the name of each unit,
23245 either a compilation unit or nested unit, as it is being analyzed.
23247 Finally, you can start
23248 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
23249 front-end of GNAT, and can be run independently (normally it is just
23250 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
23251 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
23252 @code{where} command is the first line of attack; the variable
23253 @code{lineno} (seen by @code{print lineno}), used by the second phase of
23254 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
23255 which the execution stopped, and @code{input_file name} indicates the name of
23259 @node Naming Conventions for GNAT Source Files
23260 @section Naming Conventions for GNAT Source Files
23263 In order to examine the workings of the GNAT system, the following
23264 brief description of its organization may be helpful:
23268 Files with prefix @file{^sc^SC^} contain the lexical scanner.
23271 All files prefixed with @file{^par^PAR^} are components of the parser. The
23272 numbers correspond to chapters of the Ada Reference Manual. For example,
23273 parsing of select statements can be found in @file{par-ch9.adb}.
23276 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
23277 numbers correspond to chapters of the Ada standard. For example, all
23278 issues involving context clauses can be found in @file{sem_ch10.adb}. In
23279 addition, some features of the language require sufficient special processing
23280 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
23281 dynamic dispatching, etc.
23284 All files prefixed with @file{^exp^EXP^} perform normalization and
23285 expansion of the intermediate representation (abstract syntax tree, or AST).
23286 these files use the same numbering scheme as the parser and semantics files.
23287 For example, the construction of record initialization procedures is done in
23288 @file{exp_ch3.adb}.
23291 The files prefixed with @file{^bind^BIND^} implement the binder, which
23292 verifies the consistency of the compilation, determines an order of
23293 elaboration, and generates the bind file.
23296 The files @file{atree.ads} and @file{atree.adb} detail the low-level
23297 data structures used by the front-end.
23300 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
23301 the abstract syntax tree as produced by the parser.
23304 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
23305 all entities, computed during semantic analysis.
23308 Library management issues are dealt with in files with prefix
23314 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
23315 defined in Annex A.
23320 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
23321 defined in Annex B.
23325 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
23326 both language-defined children and GNAT run-time routines.
23330 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
23331 general-purpose packages, fully documented in their specs. All
23332 the other @file{.c} files are modifications of common @command{gcc} files.
23335 @node Getting Internal Debugging Information
23336 @section Getting Internal Debugging Information
23339 Most compilers have internal debugging switches and modes. GNAT
23340 does also, except GNAT internal debugging switches and modes are not
23341 secret. A summary and full description of all the compiler and binder
23342 debug flags are in the file @file{debug.adb}. You must obtain the
23343 sources of the compiler to see the full detailed effects of these flags.
23345 The switches that print the source of the program (reconstructed from
23346 the internal tree) are of general interest for user programs, as are the
23348 the full internal tree, and the entity table (the symbol table
23349 information). The reconstructed source provides a readable version of the
23350 program after the front-end has completed analysis and expansion,
23351 and is useful when studying the performance of specific constructs.
23352 For example, constraint checks are indicated, complex aggregates
23353 are replaced with loops and assignments, and tasking primitives
23354 are replaced with run-time calls.
23356 @node Stack Traceback
23357 @section Stack Traceback
23359 @cindex stack traceback
23360 @cindex stack unwinding
23363 Traceback is a mechanism to display the sequence of subprogram calls that
23364 leads to a specified execution point in a program. Often (but not always)
23365 the execution point is an instruction at which an exception has been raised.
23366 This mechanism is also known as @i{stack unwinding} because it obtains
23367 its information by scanning the run-time stack and recovering the activation
23368 records of all active subprograms. Stack unwinding is one of the most
23369 important tools for program debugging.
23371 The first entry stored in traceback corresponds to the deepest calling level,
23372 that is to say the subprogram currently executing the instruction
23373 from which we want to obtain the traceback.
23375 Note that there is no runtime performance penalty when stack traceback
23376 is enabled, and no exception is raised during program execution.
23379 * Non-Symbolic Traceback::
23380 * Symbolic Traceback::
23383 @node Non-Symbolic Traceback
23384 @subsection Non-Symbolic Traceback
23385 @cindex traceback, non-symbolic
23388 Note: this feature is not supported on all platforms. See
23389 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
23393 * Tracebacks From an Unhandled Exception::
23394 * Tracebacks From Exception Occurrences (non-symbolic)::
23395 * Tracebacks From Anywhere in a Program (non-symbolic)::
23398 @node Tracebacks From an Unhandled Exception
23399 @subsubsection Tracebacks From an Unhandled Exception
23402 A runtime non-symbolic traceback is a list of addresses of call instructions.
23403 To enable this feature you must use the @option{-E}
23404 @code{gnatbind}'s option. With this option a stack traceback is stored as part
23405 of exception information. You can retrieve this information using the
23406 @code{addr2line} tool.
23408 Here is a simple example:
23410 @smallexample @c ada
23416 raise Constraint_Error;
23431 $ gnatmake stb -bargs -E
23434 Execution terminated by unhandled exception
23435 Exception name: CONSTRAINT_ERROR
23437 Call stack traceback locations:
23438 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23442 As we see the traceback lists a sequence of addresses for the unhandled
23443 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
23444 guess that this exception come from procedure P1. To translate these
23445 addresses into the source lines where the calls appear, the
23446 @code{addr2line} tool, described below, is invaluable. The use of this tool
23447 requires the program to be compiled with debug information.
23450 $ gnatmake -g stb -bargs -E
23453 Execution terminated by unhandled exception
23454 Exception name: CONSTRAINT_ERROR
23456 Call stack traceback locations:
23457 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23459 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
23460 0x4011f1 0x77e892a4
23462 00401373 at d:/stb/stb.adb:5
23463 0040138B at d:/stb/stb.adb:10
23464 0040139C at d:/stb/stb.adb:14
23465 00401335 at d:/stb/b~stb.adb:104
23466 004011C4 at /build/@dots{}/crt1.c:200
23467 004011F1 at /build/@dots{}/crt1.c:222
23468 77E892A4 in ?? at ??:0
23472 The @code{addr2line} tool has several other useful options:
23476 to get the function name corresponding to any location
23478 @item --demangle=gnat
23479 to use the gnat decoding mode for the function names. Note that
23480 for binutils version 2.9.x the option is simply @option{--demangle}.
23484 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
23485 0x40139c 0x401335 0x4011c4 0x4011f1
23487 00401373 in stb.p1 at d:/stb/stb.adb:5
23488 0040138B in stb.p2 at d:/stb/stb.adb:10
23489 0040139C in stb at d:/stb/stb.adb:14
23490 00401335 in main at d:/stb/b~stb.adb:104
23491 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
23492 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
23496 From this traceback we can see that the exception was raised in
23497 @file{stb.adb} at line 5, which was reached from a procedure call in
23498 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
23499 which contains the call to the main program.
23500 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
23501 and the output will vary from platform to platform.
23503 It is also possible to use @code{GDB} with these traceback addresses to debug
23504 the program. For example, we can break at a given code location, as reported
23505 in the stack traceback:
23511 Furthermore, this feature is not implemented inside Windows DLL. Only
23512 the non-symbolic traceback is reported in this case.
23515 (gdb) break *0x401373
23516 Breakpoint 1 at 0x401373: file stb.adb, line 5.
23520 It is important to note that the stack traceback addresses
23521 do not change when debug information is included. This is particularly useful
23522 because it makes it possible to release software without debug information (to
23523 minimize object size), get a field report that includes a stack traceback
23524 whenever an internal bug occurs, and then be able to retrieve the sequence
23525 of calls with the same program compiled with debug information.
23527 @node Tracebacks From Exception Occurrences (non-symbolic)
23528 @subsubsection Tracebacks From Exception Occurrences
23531 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
23532 The stack traceback is attached to the exception information string, and can
23533 be retrieved in an exception handler within the Ada program, by means of the
23534 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
23536 @smallexample @c ada
23538 with Ada.Exceptions;
23543 use Ada.Exceptions;
23551 Text_IO.Put_Line (Exception_Information (E));
23565 This program will output:
23570 Exception name: CONSTRAINT_ERROR
23571 Message: stb.adb:12
23572 Call stack traceback locations:
23573 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
23576 @node Tracebacks From Anywhere in a Program (non-symbolic)
23577 @subsubsection Tracebacks From Anywhere in a Program
23580 It is also possible to retrieve a stack traceback from anywhere in a
23581 program. For this you need to
23582 use the @code{GNAT.Traceback} API. This package includes a procedure called
23583 @code{Call_Chain} that computes a complete stack traceback, as well as useful
23584 display procedures described below. It is not necessary to use the
23585 @option{-E gnatbind} option in this case, because the stack traceback mechanism
23586 is invoked explicitly.
23589 In the following example we compute a traceback at a specific location in
23590 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
23591 convert addresses to strings:
23593 @smallexample @c ada
23595 with GNAT.Traceback;
23596 with GNAT.Debug_Utilities;
23602 use GNAT.Traceback;
23605 TB : Tracebacks_Array (1 .. 10);
23606 -- We are asking for a maximum of 10 stack frames.
23608 -- Len will receive the actual number of stack frames returned.
23610 Call_Chain (TB, Len);
23612 Text_IO.Put ("In STB.P1 : ");
23614 for K in 1 .. Len loop
23615 Text_IO.Put (Debug_Utilities.Image (TB (K)));
23636 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
23637 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
23641 You can then get further information by invoking the @code{addr2line}
23642 tool as described earlier (note that the hexadecimal addresses
23643 need to be specified in C format, with a leading ``0x'').
23645 @node Symbolic Traceback
23646 @subsection Symbolic Traceback
23647 @cindex traceback, symbolic
23650 A symbolic traceback is a stack traceback in which procedure names are
23651 associated with each code location.
23654 Note that this feature is not supported on all platforms. See
23655 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
23656 list of currently supported platforms.
23659 Note that the symbolic traceback requires that the program be compiled
23660 with debug information. If it is not compiled with debug information
23661 only the non-symbolic information will be valid.
23664 * Tracebacks From Exception Occurrences (symbolic)::
23665 * Tracebacks From Anywhere in a Program (symbolic)::
23668 @node Tracebacks From Exception Occurrences (symbolic)
23669 @subsubsection Tracebacks From Exception Occurrences
23671 @smallexample @c ada
23673 with GNAT.Traceback.Symbolic;
23679 raise Constraint_Error;
23696 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
23701 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
23704 0040149F in stb.p1 at stb.adb:8
23705 004014B7 in stb.p2 at stb.adb:13
23706 004014CF in stb.p3 at stb.adb:18
23707 004015DD in ada.stb at stb.adb:22
23708 00401461 in main at b~stb.adb:168
23709 004011C4 in __mingw_CRTStartup at crt1.c:200
23710 004011F1 in mainCRTStartup at crt1.c:222
23711 77E892A4 in ?? at ??:0
23715 In the above example the ``.\'' syntax in the @command{gnatmake} command
23716 is currently required by @command{addr2line} for files that are in
23717 the current working directory.
23718 Moreover, the exact sequence of linker options may vary from platform
23720 The above @option{-largs} section is for Windows platforms. By contrast,
23721 under Unix there is no need for the @option{-largs} section.
23722 Differences across platforms are due to details of linker implementation.
23724 @node Tracebacks From Anywhere in a Program (symbolic)
23725 @subsubsection Tracebacks From Anywhere in a Program
23728 It is possible to get a symbolic stack traceback
23729 from anywhere in a program, just as for non-symbolic tracebacks.
23730 The first step is to obtain a non-symbolic
23731 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
23732 information. Here is an example:
23734 @smallexample @c ada
23736 with GNAT.Traceback;
23737 with GNAT.Traceback.Symbolic;
23742 use GNAT.Traceback;
23743 use GNAT.Traceback.Symbolic;
23746 TB : Tracebacks_Array (1 .. 10);
23747 -- We are asking for a maximum of 10 stack frames.
23749 -- Len will receive the actual number of stack frames returned.
23751 Call_Chain (TB, Len);
23752 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
23765 @c ******************************
23767 @node Compatibility with HP Ada
23768 @chapter Compatibility with HP Ada
23769 @cindex Compatibility
23774 @cindex Compatibility between GNAT and HP Ada
23775 This chapter compares HP Ada (formerly known as ``DEC Ada'')
23776 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
23777 GNAT is highly compatible
23778 with HP Ada, and it should generally be straightforward to port code
23779 from the HP Ada environment to GNAT. However, there are a few language
23780 and implementation differences of which the user must be aware. These
23781 differences are discussed in this chapter. In
23782 addition, the operating environment and command structure for the
23783 compiler are different, and these differences are also discussed.
23785 For further details on these and other compatibility issues,
23786 see Appendix E of the HP publication
23787 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
23789 Except where otherwise indicated, the description of GNAT for OpenVMS
23790 applies to both the Alpha and I64 platforms.
23792 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
23793 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
23795 The discussion in this chapter addresses specifically the implementation
23796 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
23797 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
23798 GNAT always follows the Alpha implementation.
23800 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
23801 attributes are recognized, although only a subset of them can sensibly
23802 be implemented. The description of pragmas in
23803 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
23804 indicates whether or not they are applicable to non-VMS systems.
23807 * Ada Language Compatibility::
23808 * Differences in the Definition of Package System::
23809 * Language-Related Features::
23810 * The Package STANDARD::
23811 * The Package SYSTEM::
23812 * Tasking and Task-Related Features::
23813 * Pragmas and Pragma-Related Features::
23814 * Library of Predefined Units::
23816 * Main Program Definition::
23817 * Implementation-Defined Attributes::
23818 * Compiler and Run-Time Interfacing::
23819 * Program Compilation and Library Management::
23821 * Implementation Limits::
23822 * Tools and Utilities::
23825 @node Ada Language Compatibility
23826 @section Ada Language Compatibility
23829 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
23830 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
23831 with Ada 83, and therefore Ada 83 programs will compile
23832 and run under GNAT with
23833 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
23834 provides details on specific incompatibilities.
23836 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
23837 as well as the pragma @code{ADA_83}, to force the compiler to
23838 operate in Ada 83 mode. This mode does not guarantee complete
23839 conformance to Ada 83, but in practice is sufficient to
23840 eliminate most sources of incompatibilities.
23841 In particular, it eliminates the recognition of the
23842 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
23843 in Ada 83 programs is legal, and handles the cases of packages
23844 with optional bodies, and generics that instantiate unconstrained
23845 types without the use of @code{(<>)}.
23847 @node Differences in the Definition of Package System
23848 @section Differences in the Definition of Package @code{System}
23851 An Ada compiler is allowed to add
23852 implementation-dependent declarations to package @code{System}.
23854 GNAT does not take advantage of this permission, and the version of
23855 @code{System} provided by GNAT exactly matches that defined in the Ada
23858 However, HP Ada adds an extensive set of declarations to package
23860 as fully documented in the HP Ada manuals. To minimize changes required
23861 for programs that make use of these extensions, GNAT provides the pragma
23862 @code{Extend_System} for extending the definition of package System. By using:
23863 @cindex pragma @code{Extend_System}
23864 @cindex @code{Extend_System} pragma
23866 @smallexample @c ada
23869 pragma Extend_System (Aux_DEC);
23875 the set of definitions in @code{System} is extended to include those in
23876 package @code{System.Aux_DEC}.
23877 @cindex @code{System.Aux_DEC} package
23878 @cindex @code{Aux_DEC} package (child of @code{System})
23879 These definitions are incorporated directly into package @code{System},
23880 as though they had been declared there. For a
23881 list of the declarations added, see the spec of this package,
23882 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
23883 @cindex @file{s-auxdec.ads} file
23884 The pragma @code{Extend_System} is a configuration pragma, which means that
23885 it can be placed in the file @file{gnat.adc}, so that it will automatically
23886 apply to all subsequent compilations. See @ref{Configuration Pragmas},
23887 for further details.
23889 An alternative approach that avoids the use of the non-standard
23890 @code{Extend_System} pragma is to add a context clause to the unit that
23891 references these facilities:
23893 @smallexample @c ada
23895 with System.Aux_DEC;
23896 use System.Aux_DEC;
23901 The effect is not quite semantically identical to incorporating
23902 the declarations directly into package @code{System},
23903 but most programs will not notice a difference
23904 unless they use prefix notation (e.g.@: @code{System.Integer_8})
23905 to reference the entities directly in package @code{System}.
23906 For units containing such references,
23907 the prefixes must either be removed, or the pragma @code{Extend_System}
23910 @node Language-Related Features
23911 @section Language-Related Features
23914 The following sections highlight differences in types,
23915 representations of types, operations, alignment, and
23919 * Integer Types and Representations::
23920 * Floating-Point Types and Representations::
23921 * Pragmas Float_Representation and Long_Float::
23922 * Fixed-Point Types and Representations::
23923 * Record and Array Component Alignment::
23924 * Address Clauses::
23925 * Other Representation Clauses::
23928 @node Integer Types and Representations
23929 @subsection Integer Types and Representations
23932 The set of predefined integer types is identical in HP Ada and GNAT.
23933 Furthermore the representation of these integer types is also identical,
23934 including the capability of size clauses forcing biased representation.
23937 HP Ada for OpenVMS Alpha systems has defined the
23938 following additional integer types in package @code{System}:
23955 @code{LARGEST_INTEGER}
23959 In GNAT, the first four of these types may be obtained from the
23960 standard Ada package @code{Interfaces}.
23961 Alternatively, by use of the pragma @code{Extend_System}, identical
23962 declarations can be referenced directly in package @code{System}.
23963 On both GNAT and HP Ada, the maximum integer size is 64 bits.
23965 @node Floating-Point Types and Representations
23966 @subsection Floating-Point Types and Representations
23967 @cindex Floating-Point types
23970 The set of predefined floating-point types is identical in HP Ada and GNAT.
23971 Furthermore the representation of these floating-point
23972 types is also identical. One important difference is that the default
23973 representation for HP Ada is @code{VAX_Float}, but the default representation
23976 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
23977 pragma @code{Float_Representation} as described in the HP Ada
23979 For example, the declarations:
23981 @smallexample @c ada
23983 type F_Float is digits 6;
23984 pragma Float_Representation (VAX_Float, F_Float);
23989 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
23991 This set of declarations actually appears in @code{System.Aux_DEC},
23993 the full set of additional floating-point declarations provided in
23994 the HP Ada version of package @code{System}.
23995 This and similar declarations may be accessed in a user program
23996 by using pragma @code{Extend_System}. The use of this
23997 pragma, and the related pragma @code{Long_Float} is described in further
23998 detail in the following section.
24000 @node Pragmas Float_Representation and Long_Float
24001 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24004 HP Ada provides the pragma @code{Float_Representation}, which
24005 acts as a program library switch to allow control over
24006 the internal representation chosen for the predefined
24007 floating-point types declared in the package @code{Standard}.
24008 The format of this pragma is as follows:
24010 @smallexample @c ada
24012 pragma Float_Representation(VAX_Float | IEEE_Float);
24017 This pragma controls the representation of floating-point
24022 @code{VAX_Float} specifies that floating-point
24023 types are represented by default with the VAX system hardware types
24024 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24025 Note that the @code{H-floating}
24026 type was available only on VAX systems, and is not available
24027 in either HP Ada or GNAT.
24030 @code{IEEE_Float} specifies that floating-point
24031 types are represented by default with the IEEE single and
24032 double floating-point types.
24036 GNAT provides an identical implementation of the pragma
24037 @code{Float_Representation}, except that it functions as a
24038 configuration pragma. Note that the
24039 notion of configuration pragma corresponds closely to the
24040 HP Ada notion of a program library switch.
24042 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24044 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24045 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24046 advisable to change the format of numbers passed to standard library
24047 routines, and if necessary explicit type conversions may be needed.
24049 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24050 efficient, and (given that it conforms to an international standard)
24051 potentially more portable.
24052 The situation in which @code{VAX_Float} may be useful is in interfacing
24053 to existing code and data that expect the use of @code{VAX_Float}.
24054 In such a situation use the predefined @code{VAX_Float}
24055 types in package @code{System}, as extended by
24056 @code{Extend_System}. For example, use @code{System.F_Float}
24057 to specify the 32-bit @code{F-Float} format.
24060 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24061 to allow control over the internal representation chosen
24062 for the predefined type @code{Long_Float} and for floating-point
24063 type declarations with digits specified in the range 7 .. 15.
24064 The format of this pragma is as follows:
24066 @smallexample @c ada
24068 pragma Long_Float (D_FLOAT | G_FLOAT);
24072 @node Fixed-Point Types and Representations
24073 @subsection Fixed-Point Types and Representations
24076 On HP Ada for OpenVMS Alpha systems, rounding is
24077 away from zero for both positive and negative numbers.
24078 Therefore, @code{+0.5} rounds to @code{1},
24079 and @code{-0.5} rounds to @code{-1}.
24081 On GNAT the results of operations
24082 on fixed-point types are in accordance with the Ada
24083 rules. In particular, results of operations on decimal
24084 fixed-point types are truncated.
24086 @node Record and Array Component Alignment
24087 @subsection Record and Array Component Alignment
24090 On HP Ada for OpenVMS Alpha, all non-composite components
24091 are aligned on natural boundaries. For example, 1-byte
24092 components are aligned on byte boundaries, 2-byte
24093 components on 2-byte boundaries, 4-byte components on 4-byte
24094 byte boundaries, and so on. The OpenVMS Alpha hardware
24095 runs more efficiently with naturally aligned data.
24097 On GNAT, alignment rules are compatible
24098 with HP Ada for OpenVMS Alpha.
24100 @node Address Clauses
24101 @subsection Address Clauses
24104 In HP Ada and GNAT, address clauses are supported for
24105 objects and imported subprograms.
24106 The predefined type @code{System.Address} is a private type
24107 in both compilers on Alpha OpenVMS, with the same representation
24108 (it is simply a machine pointer). Addition, subtraction, and comparison
24109 operations are available in the standard Ada package
24110 @code{System.Storage_Elements}, or in package @code{System}
24111 if it is extended to include @code{System.Aux_DEC} using a
24112 pragma @code{Extend_System} as previously described.
24114 Note that code that @code{with}'s both this extended package @code{System}
24115 and the package @code{System.Storage_Elements} should not @code{use}
24116 both packages, or ambiguities will result. In general it is better
24117 not to mix these two sets of facilities. The Ada package was
24118 designed specifically to provide the kind of features that HP Ada
24119 adds directly to package @code{System}.
24121 The type @code{System.Address} is a 64-bit integer type in GNAT for
24122 I64 OpenVMS. For more information,
24123 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24125 GNAT is compatible with HP Ada in its handling of address
24126 clauses, except for some limitations in
24127 the form of address clauses for composite objects with
24128 initialization. Such address clauses are easily replaced
24129 by the use of an explicitly-defined constant as described
24130 in the Ada Reference Manual (13.1(22)). For example, the sequence
24133 @smallexample @c ada
24135 X, Y : Integer := Init_Func;
24136 Q : String (X .. Y) := "abc";
24138 for Q'Address use Compute_Address;
24143 will be rejected by GNAT, since the address cannot be computed at the time
24144 that @code{Q} is declared. To achieve the intended effect, write instead:
24146 @smallexample @c ada
24149 X, Y : Integer := Init_Func;
24150 Q_Address : constant Address := Compute_Address;
24151 Q : String (X .. Y) := "abc";
24153 for Q'Address use Q_Address;
24159 which will be accepted by GNAT (and other Ada compilers), and is also
24160 compatible with Ada 83. A fuller description of the restrictions
24161 on address specifications is found in @ref{Top, GNAT Reference Manual,
24162 About This Guide, gnat_rm, GNAT Reference Manual}.
24164 @node Other Representation Clauses
24165 @subsection Other Representation Clauses
24168 GNAT implements in a compatible manner all the representation
24169 clauses supported by HP Ada. In addition, GNAT
24170 implements the representation clause forms that were introduced in Ada 95,
24171 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24173 @node The Package STANDARD
24174 @section The Package @code{STANDARD}
24177 The package @code{STANDARD}, as implemented by HP Ada, is fully
24178 described in the @cite{Ada Reference Manual} and in the
24179 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24180 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24182 In addition, HP Ada supports the Latin-1 character set in
24183 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24184 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24185 the type @code{WIDE_CHARACTER}.
24187 The floating-point types supported by GNAT are those
24188 supported by HP Ada, but the defaults are different, and are controlled by
24189 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24191 @node The Package SYSTEM
24192 @section The Package @code{SYSTEM}
24195 HP Ada provides a specific version of the package
24196 @code{SYSTEM} for each platform on which the language is implemented.
24197 For the complete spec of the package @code{SYSTEM}, see
24198 Appendix F of the @cite{HP Ada Language Reference Manual}.
24200 On HP Ada, the package @code{SYSTEM} includes the following conversion
24203 @item @code{TO_ADDRESS(INTEGER)}
24205 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24207 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24209 @item @code{TO_INTEGER(ADDRESS)}
24211 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24213 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24214 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24218 By default, GNAT supplies a version of @code{SYSTEM} that matches
24219 the definition given in the @cite{Ada Reference Manual}.
24221 is a subset of the HP system definitions, which is as
24222 close as possible to the original definitions. The only difference
24223 is that the definition of @code{SYSTEM_NAME} is different:
24225 @smallexample @c ada
24227 type Name is (SYSTEM_NAME_GNAT);
24228 System_Name : constant Name := SYSTEM_NAME_GNAT;
24233 Also, GNAT adds the Ada declarations for
24234 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
24236 However, the use of the following pragma causes GNAT
24237 to extend the definition of package @code{SYSTEM} so that it
24238 encompasses the full set of HP-specific extensions,
24239 including the functions listed above:
24241 @smallexample @c ada
24243 pragma Extend_System (Aux_DEC);
24248 The pragma @code{Extend_System} is a configuration pragma that
24249 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
24250 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
24252 HP Ada does not allow the recompilation of the package
24253 @code{SYSTEM}. Instead HP Ada provides several pragmas
24254 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
24255 to modify values in the package @code{SYSTEM}.
24256 On OpenVMS Alpha systems, the pragma
24257 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
24258 its single argument.
24260 GNAT does permit the recompilation of package @code{SYSTEM} using
24261 the special switch @option{-gnatg}, and this switch can be used if
24262 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
24263 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
24264 or @code{MEMORY_SIZE} by any other means.
24266 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
24267 enumeration literal @code{SYSTEM_NAME_GNAT}.
24269 The definitions provided by the use of
24271 @smallexample @c ada
24272 pragma Extend_System (AUX_Dec);
24276 are virtually identical to those provided by the HP Ada 83 package
24277 @code{SYSTEM}. One important difference is that the name of the
24279 function for type @code{UNSIGNED_LONGWORD} is changed to
24280 @code{TO_ADDRESS_LONG}.
24281 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
24282 discussion of why this change was necessary.
24285 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
24287 an extension to Ada 83 not strictly compatible with the reference manual.
24288 GNAT, in order to be exactly compatible with the standard,
24289 does not provide this capability. In HP Ada 83, the
24290 point of this definition is to deal with a call like:
24292 @smallexample @c ada
24293 TO_ADDRESS (16#12777#);
24297 Normally, according to Ada 83 semantics, one would expect this to be
24298 ambiguous, since it matches both the @code{INTEGER} and
24299 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
24300 However, in HP Ada 83, there is no ambiguity, since the
24301 definition using @i{universal_integer} takes precedence.
24303 In GNAT, since the version with @i{universal_integer} cannot be supplied,
24305 not possible to be 100% compatible. Since there are many programs using
24306 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
24308 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
24309 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
24311 @smallexample @c ada
24312 function To_Address (X : Integer) return Address;
24313 pragma Pure_Function (To_Address);
24315 function To_Address_Long (X : Unsigned_Longword) return Address;
24316 pragma Pure_Function (To_Address_Long);
24320 This means that programs using @code{TO_ADDRESS} for
24321 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
24323 @node Tasking and Task-Related Features
24324 @section Tasking and Task-Related Features
24327 This section compares the treatment of tasking in GNAT
24328 and in HP Ada for OpenVMS Alpha.
24329 The GNAT description applies to both Alpha and I64 OpenVMS.
24330 For detailed information on tasking in
24331 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
24332 relevant run-time reference manual.
24335 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
24336 * Assigning Task IDs::
24337 * Task IDs and Delays::
24338 * Task-Related Pragmas::
24339 * Scheduling and Task Priority::
24341 * External Interrupts::
24344 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24345 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24348 On OpenVMS Alpha systems, each Ada task (except a passive
24349 task) is implemented as a single stream of execution
24350 that is created and managed by the kernel. On these
24351 systems, HP Ada tasking support is based on DECthreads,
24352 an implementation of the POSIX standard for threads.
24354 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
24355 code that calls DECthreads routines can be used together.
24356 The interaction between Ada tasks and DECthreads routines
24357 can have some benefits. For example when on OpenVMS Alpha,
24358 HP Ada can call C code that is already threaded.
24360 GNAT uses the facilities of DECthreads,
24361 and Ada tasks are mapped to threads.
24363 @node Assigning Task IDs
24364 @subsection Assigning Task IDs
24367 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
24368 the environment task that executes the main program. On
24369 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
24370 that have been created but are not yet activated.
24372 On OpenVMS Alpha systems, task IDs are assigned at
24373 activation. On GNAT systems, task IDs are also assigned at
24374 task creation but do not have the same form or values as
24375 task ID values in HP Ada. There is no null task, and the
24376 environment task does not have a specific task ID value.
24378 @node Task IDs and Delays
24379 @subsection Task IDs and Delays
24382 On OpenVMS Alpha systems, tasking delays are implemented
24383 using Timer System Services. The Task ID is used for the
24384 identification of the timer request (the @code{REQIDT} parameter).
24385 If Timers are used in the application take care not to use
24386 @code{0} for the identification, because cancelling such a timer
24387 will cancel all timers and may lead to unpredictable results.
24389 @node Task-Related Pragmas
24390 @subsection Task-Related Pragmas
24393 Ada supplies the pragma @code{TASK_STORAGE}, which allows
24394 specification of the size of the guard area for a task
24395 stack. (The guard area forms an area of memory that has no
24396 read or write access and thus helps in the detection of
24397 stack overflow.) On OpenVMS Alpha systems, if the pragma
24398 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
24399 area is created. In the absence of a pragma @code{TASK_STORAGE},
24400 a default guard area is created.
24402 GNAT supplies the following task-related pragmas:
24405 @item @code{TASK_INFO}
24407 This pragma appears within a task definition and
24408 applies to the task in which it appears. The argument
24409 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
24411 @item @code{TASK_STORAGE}
24413 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
24414 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
24415 @code{SUPPRESS}, and @code{VOLATILE}.
24417 @node Scheduling and Task Priority
24418 @subsection Scheduling and Task Priority
24421 HP Ada implements the Ada language requirement that
24422 when two tasks are eligible for execution and they have
24423 different priorities, the lower priority task does not
24424 execute while the higher priority task is waiting. The HP
24425 Ada Run-Time Library keeps a task running until either the
24426 task is suspended or a higher priority task becomes ready.
24428 On OpenVMS Alpha systems, the default strategy is round-
24429 robin with preemption. Tasks of equal priority take turns
24430 at the processor. A task is run for a certain period of
24431 time and then placed at the tail of the ready queue for
24432 its priority level.
24434 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
24435 which can be used to enable or disable round-robin
24436 scheduling of tasks with the same priority.
24437 See the relevant HP Ada run-time reference manual for
24438 information on using the pragmas to control HP Ada task
24441 GNAT follows the scheduling rules of Annex D (Real-Time
24442 Annex) of the @cite{Ada Reference Manual}. In general, this
24443 scheduling strategy is fully compatible with HP Ada
24444 although it provides some additional constraints (as
24445 fully documented in Annex D).
24446 GNAT implements time slicing control in a manner compatible with
24447 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
24448 are identical to the HP Ada 83 pragma of the same name.
24449 Note that it is not possible to mix GNAT tasking and
24450 HP Ada 83 tasking in the same program, since the two run-time
24451 libraries are not compatible.
24453 @node The Task Stack
24454 @subsection The Task Stack
24457 In HP Ada, a task stack is allocated each time a
24458 non-passive task is activated. As soon as the task is
24459 terminated, the storage for the task stack is deallocated.
24460 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
24461 a default stack size is used. Also, regardless of the size
24462 specified, some additional space is allocated for task
24463 management purposes. On OpenVMS Alpha systems, at least
24464 one page is allocated.
24466 GNAT handles task stacks in a similar manner. In accordance with
24467 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
24468 an alternative method for controlling the task stack size.
24469 The specification of the attribute @code{T'STORAGE_SIZE} is also
24470 supported in a manner compatible with HP Ada.
24472 @node External Interrupts
24473 @subsection External Interrupts
24476 On HP Ada, external interrupts can be associated with task entries.
24477 GNAT is compatible with HP Ada in its handling of external interrupts.
24479 @node Pragmas and Pragma-Related Features
24480 @section Pragmas and Pragma-Related Features
24483 Both HP Ada and GNAT supply all language-defined pragmas
24484 as specified by the Ada 83 standard. GNAT also supplies all
24485 language-defined pragmas introduced by Ada 95 and Ada 2005.
24486 In addition, GNAT implements the implementation-defined pragmas
24490 @item @code{AST_ENTRY}
24492 @item @code{COMMON_OBJECT}
24494 @item @code{COMPONENT_ALIGNMENT}
24496 @item @code{EXPORT_EXCEPTION}
24498 @item @code{EXPORT_FUNCTION}
24500 @item @code{EXPORT_OBJECT}
24502 @item @code{EXPORT_PROCEDURE}
24504 @item @code{EXPORT_VALUED_PROCEDURE}
24506 @item @code{FLOAT_REPRESENTATION}
24510 @item @code{IMPORT_EXCEPTION}
24512 @item @code{IMPORT_FUNCTION}
24514 @item @code{IMPORT_OBJECT}
24516 @item @code{IMPORT_PROCEDURE}
24518 @item @code{IMPORT_VALUED_PROCEDURE}
24520 @item @code{INLINE_GENERIC}
24522 @item @code{INTERFACE_NAME}
24524 @item @code{LONG_FLOAT}
24526 @item @code{MAIN_STORAGE}
24528 @item @code{PASSIVE}
24530 @item @code{PSECT_OBJECT}
24532 @item @code{SHARE_GENERIC}
24534 @item @code{SUPPRESS_ALL}
24536 @item @code{TASK_STORAGE}
24538 @item @code{TIME_SLICE}
24544 These pragmas are all fully implemented, with the exception of @code{TITLE},
24545 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
24546 recognized, but which have no
24547 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
24548 use of Ada protected objects. In GNAT, all generics are inlined.
24550 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
24551 a separate subprogram specification which must appear before the
24554 GNAT also supplies a number of implementation-defined pragmas as follows:
24556 @item @code{ABORT_DEFER}
24558 @item @code{ADA_83}
24560 @item @code{ADA_95}
24562 @item @code{ADA_05}
24564 @item @code{ANNOTATE}
24566 @item @code{ASSERT}
24568 @item @code{C_PASS_BY_COPY}
24570 @item @code{CPP_CLASS}
24572 @item @code{CPP_CONSTRUCTOR}
24574 @item @code{CPP_DESTRUCTOR}
24578 @item @code{EXTEND_SYSTEM}
24580 @item @code{LINKER_ALIAS}
24582 @item @code{LINKER_SECTION}
24584 @item @code{MACHINE_ATTRIBUTE}
24586 @item @code{NO_RETURN}
24588 @item @code{PURE_FUNCTION}
24590 @item @code{SOURCE_FILE_NAME}
24592 @item @code{SOURCE_REFERENCE}
24594 @item @code{TASK_INFO}
24596 @item @code{UNCHECKED_UNION}
24598 @item @code{UNIMPLEMENTED_UNIT}
24600 @item @code{UNIVERSAL_DATA}
24602 @item @code{UNSUPPRESS}
24604 @item @code{WARNINGS}
24606 @item @code{WEAK_EXTERNAL}
24610 For full details on these GNAT implementation-defined pragmas,
24611 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
24615 * Restrictions on the Pragma INLINE::
24616 * Restrictions on the Pragma INTERFACE::
24617 * Restrictions on the Pragma SYSTEM_NAME::
24620 @node Restrictions on the Pragma INLINE
24621 @subsection Restrictions on Pragma @code{INLINE}
24624 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
24626 @item Parameters cannot have a task type.
24628 @item Function results cannot be task types, unconstrained
24629 array types, or unconstrained types with discriminants.
24631 @item Bodies cannot declare the following:
24633 @item Subprogram body or stub (imported subprogram is allowed)
24637 @item Generic declarations
24639 @item Instantiations
24643 @item Access types (types derived from access types allowed)
24645 @item Array or record types
24647 @item Dependent tasks
24649 @item Direct recursive calls of subprogram or containing
24650 subprogram, directly or via a renaming
24656 In GNAT, the only restriction on pragma @code{INLINE} is that the
24657 body must occur before the call if both are in the same
24658 unit, and the size must be appropriately small. There are
24659 no other specific restrictions which cause subprograms to
24660 be incapable of being inlined.
24662 @node Restrictions on the Pragma INTERFACE
24663 @subsection Restrictions on Pragma @code{INTERFACE}
24666 The following restrictions on pragma @code{INTERFACE}
24667 are enforced by both HP Ada and GNAT:
24669 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
24670 Default is the default on OpenVMS Alpha systems.
24672 @item Parameter passing: Language specifies default
24673 mechanisms but can be overridden with an @code{EXPORT} pragma.
24676 @item Ada: Use internal Ada rules.
24678 @item Bliss, C: Parameters must be mode @code{in}; cannot be
24679 record or task type. Result cannot be a string, an
24680 array, or a record.
24682 @item Fortran: Parameters cannot have a task type. Result cannot
24683 be a string, an array, or a record.
24688 GNAT is entirely upwards compatible with HP Ada, and in addition allows
24689 record parameters for all languages.
24691 @node Restrictions on the Pragma SYSTEM_NAME
24692 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
24695 For HP Ada for OpenVMS Alpha, the enumeration literal
24696 for the type @code{NAME} is @code{OPENVMS_AXP}.
24697 In GNAT, the enumeration
24698 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
24700 @node Library of Predefined Units
24701 @section Library of Predefined Units
24704 A library of predefined units is provided as part of the
24705 HP Ada and GNAT implementations. HP Ada does not provide
24706 the package @code{MACHINE_CODE} but instead recommends importing
24709 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
24710 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
24712 The HP Ada Predefined Library units are modified to remove post-Ada 83
24713 incompatibilities and to make them interoperable with GNAT
24714 (@pxref{Changes to DECLIB}, for details).
24715 The units are located in the @file{DECLIB} directory.
24717 The GNAT RTL is contained in
24718 the @file{ADALIB} directory, and
24719 the default search path is set up to find @code{DECLIB} units in preference
24720 to @code{ADALIB} units with the same name (@code{TEXT_IO},
24721 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
24724 * Changes to DECLIB::
24727 @node Changes to DECLIB
24728 @subsection Changes to @code{DECLIB}
24731 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
24732 compatibility are minor and include the following:
24735 @item Adjusting the location of pragmas and record representation
24736 clauses to obey Ada 95 (and thus Ada 2005) rules
24738 @item Adding the proper notation to generic formal parameters
24739 that take unconstrained types in instantiation
24741 @item Adding pragma @code{ELABORATE_BODY} to package specs
24742 that have package bodies not otherwise allowed
24744 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
24745 ``@code{PROTECTD}''.
24746 Currently these are found only in the @code{STARLET} package spec.
24748 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
24749 where the address size is constrained to 32 bits.
24753 None of the above changes is visible to users.
24759 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
24762 @item Command Language Interpreter (CLI interface)
24764 @item DECtalk Run-Time Library (DTK interface)
24766 @item Librarian utility routines (LBR interface)
24768 @item General Purpose Run-Time Library (LIB interface)
24770 @item Math Run-Time Library (MTH interface)
24772 @item National Character Set Run-Time Library (NCS interface)
24774 @item Compiled Code Support Run-Time Library (OTS interface)
24776 @item Parallel Processing Run-Time Library (PPL interface)
24778 @item Screen Management Run-Time Library (SMG interface)
24780 @item Sort Run-Time Library (SOR interface)
24782 @item String Run-Time Library (STR interface)
24784 @item STARLET System Library
24787 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
24789 @item X Windows Toolkit (XT interface)
24791 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
24795 GNAT provides implementations of these HP bindings in the @code{DECLIB}
24796 directory, on both the Alpha and I64 OpenVMS platforms.
24798 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
24800 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
24801 A pragma @code{Linker_Options} has been added to packages @code{Xm},
24802 @code{Xt}, and @code{X_Lib}
24803 causing the default X/Motif sharable image libraries to be linked in. This
24804 is done via options files named @file{xm.opt}, @file{xt.opt}, and
24805 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
24807 It may be necessary to edit these options files to update or correct the
24808 library names if, for example, the newer X/Motif bindings from
24809 @file{ADA$EXAMPLES}
24810 had been (previous to installing GNAT) copied and renamed to supersede the
24811 default @file{ADA$PREDEFINED} versions.
24814 * Shared Libraries and Options Files::
24815 * Interfaces to C::
24818 @node Shared Libraries and Options Files
24819 @subsection Shared Libraries and Options Files
24822 When using the HP Ada
24823 predefined X and Motif bindings, the linking with their sharable images is
24824 done automatically by @command{GNAT LINK}.
24825 When using other X and Motif bindings, you need
24826 to add the corresponding sharable images to the command line for
24827 @code{GNAT LINK}. When linking with shared libraries, or with
24828 @file{.OPT} files, you must
24829 also add them to the command line for @command{GNAT LINK}.
24831 A shared library to be used with GNAT is built in the same way as other
24832 libraries under VMS. The VMS Link command can be used in standard fashion.
24834 @node Interfaces to C
24835 @subsection Interfaces to C
24839 provides the following Ada types and operations:
24842 @item C types package (@code{C_TYPES})
24844 @item C strings (@code{C_TYPES.NULL_TERMINATED})
24846 @item Other_types (@code{SHORT_INT})
24850 Interfacing to C with GNAT, you can use the above approach
24851 described for HP Ada or the facilities of Annex B of
24852 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
24853 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
24854 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
24856 The @option{-gnatF} qualifier forces default and explicit
24857 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
24858 to be uppercased for compatibility with the default behavior
24859 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
24861 @node Main Program Definition
24862 @section Main Program Definition
24865 The following section discusses differences in the
24866 definition of main programs on HP Ada and GNAT.
24867 On HP Ada, main programs are defined to meet the
24868 following conditions:
24870 @item Procedure with no formal parameters (returns @code{0} upon
24873 @item Procedure with no formal parameters (returns @code{42} when
24874 an unhandled exception is raised)
24876 @item Function with no formal parameters whose returned value
24877 is of a discrete type
24879 @item Procedure with one @code{out} formal of a discrete type for
24880 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
24885 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
24886 a main function or main procedure returns a discrete
24887 value whose size is less than 64 bits (32 on VAX systems),
24888 the value is zero- or sign-extended as appropriate.
24889 On GNAT, main programs are defined as follows:
24891 @item Must be a non-generic, parameterless subprogram that
24892 is either a procedure or function returning an Ada
24893 @code{STANDARD.INTEGER} (the predefined type)
24895 @item Cannot be a generic subprogram or an instantiation of a
24899 @node Implementation-Defined Attributes
24900 @section Implementation-Defined Attributes
24903 GNAT provides all HP Ada implementation-defined
24906 @node Compiler and Run-Time Interfacing
24907 @section Compiler and Run-Time Interfacing
24910 HP Ada provides the following qualifiers to pass options to the linker
24913 @item @option{/WAIT} and @option{/SUBMIT}
24915 @item @option{/COMMAND}
24917 @item @option{/@r{[}NO@r{]}MAP}
24919 @item @option{/OUTPUT=@var{file-spec}}
24921 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
24925 To pass options to the linker, GNAT provides the following
24929 @item @option{/EXECUTABLE=@var{exec-name}}
24931 @item @option{/VERBOSE}
24933 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
24937 For more information on these switches, see
24938 @ref{Switches for gnatlink}.
24939 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
24940 to control optimization. HP Ada also supplies the
24943 @item @code{OPTIMIZE}
24945 @item @code{INLINE}
24947 @item @code{INLINE_GENERIC}
24949 @item @code{SUPPRESS_ALL}
24951 @item @code{PASSIVE}
24955 In GNAT, optimization is controlled strictly by command
24956 line parameters, as described in the corresponding section of this guide.
24957 The HP pragmas for control of optimization are
24958 recognized but ignored.
24960 Note that in GNAT, the default is optimization off, whereas in HP Ada
24961 the default is that optimization is turned on.
24963 @node Program Compilation and Library Management
24964 @section Program Compilation and Library Management
24967 HP Ada and GNAT provide a comparable set of commands to
24968 build programs. HP Ada also provides a program library,
24969 which is a concept that does not exist on GNAT. Instead,
24970 GNAT provides directories of sources that are compiled as
24973 The following table summarizes
24974 the HP Ada commands and provides
24975 equivalent GNAT commands. In this table, some GNAT
24976 equivalents reflect the fact that GNAT does not use the
24977 concept of a program library. Instead, it uses a model
24978 in which collections of source and object files are used
24979 in a manner consistent with other languages like C and
24980 Fortran. Therefore, standard system file commands are used
24981 to manipulate these elements. Those GNAT commands are marked with
24983 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
24986 @multitable @columnfractions .35 .65
24988 @item @emph{HP Ada Command}
24989 @tab @emph{GNAT Equivalent / Description}
24991 @item @command{ADA}
24992 @tab @command{GNAT COMPILE}@*
24993 Invokes the compiler to compile one or more Ada source files.
24995 @item @command{ACS ATTACH}@*
24996 @tab [No equivalent]@*
24997 Switches control of terminal from current process running the program
25000 @item @command{ACS CHECK}
25001 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25002 Forms the execution closure of one
25003 or more compiled units and checks completeness and currency.
25005 @item @command{ACS COMPILE}
25006 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25007 Forms the execution closure of one or
25008 more specified units, checks completeness and currency,
25009 identifies units that have revised source files, compiles same,
25010 and recompiles units that are or will become obsolete.
25011 Also completes incomplete generic instantiations.
25013 @item @command{ACS COPY FOREIGN}
25015 Copies a foreign object file into the program library as a
25018 @item @command{ACS COPY UNIT}
25020 Copies a compiled unit from one program library to another.
25022 @item @command{ACS CREATE LIBRARY}
25023 @tab Create /directory (*)@*
25024 Creates a program library.
25026 @item @command{ACS CREATE SUBLIBRARY}
25027 @tab Create /directory (*)@*
25028 Creates a program sublibrary.
25030 @item @command{ACS DELETE LIBRARY}
25032 Deletes a program library and its contents.
25034 @item @command{ACS DELETE SUBLIBRARY}
25036 Deletes a program sublibrary and its contents.
25038 @item @command{ACS DELETE UNIT}
25039 @tab Delete file (*)@*
25040 On OpenVMS systems, deletes one or more compiled units from
25041 the current program library.
25043 @item @command{ACS DIRECTORY}
25044 @tab Directory (*)@*
25045 On OpenVMS systems, lists units contained in the current
25048 @item @command{ACS ENTER FOREIGN}
25050 Allows the import of a foreign body as an Ada library
25051 spec and enters a reference to a pointer.
25053 @item @command{ACS ENTER UNIT}
25055 Enters a reference (pointer) from the current program library to
25056 a unit compiled into another program library.
25058 @item @command{ACS EXIT}
25059 @tab [No equivalent]@*
25060 Exits from the program library manager.
25062 @item @command{ACS EXPORT}
25064 Creates an object file that contains system-specific object code
25065 for one or more units. With GNAT, object files can simply be copied
25066 into the desired directory.
25068 @item @command{ACS EXTRACT SOURCE}
25070 Allows access to the copied source file for each Ada compilation unit
25072 @item @command{ACS HELP}
25073 @tab @command{HELP GNAT}@*
25074 Provides online help.
25076 @item @command{ACS LINK}
25077 @tab @command{GNAT LINK}@*
25078 Links an object file containing Ada units into an executable file.
25080 @item @command{ACS LOAD}
25082 Loads (partially compiles) Ada units into the program library.
25083 Allows loading a program from a collection of files into a library
25084 without knowing the relationship among units.
25086 @item @command{ACS MERGE}
25088 Merges into the current program library, one or more units from
25089 another library where they were modified.
25091 @item @command{ACS RECOMPILE}
25092 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25093 Recompiles from external or copied source files any obsolete
25094 unit in the closure. Also, completes any incomplete generic
25097 @item @command{ACS REENTER}
25098 @tab @command{GNAT MAKE}@*
25099 Reenters current references to units compiled after last entered
25100 with the @command{ACS ENTER UNIT} command.
25102 @item @command{ACS SET LIBRARY}
25103 @tab Set default (*)@*
25104 Defines a program library to be the compilation context as well
25105 as the target library for compiler output and commands in general.
25107 @item @command{ACS SET PRAGMA}
25108 @tab Edit @file{gnat.adc} (*)@*
25109 Redefines specified values of the library characteristics
25110 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25111 and @code{Float_Representation}.
25113 @item @command{ACS SET SOURCE}
25114 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25115 Defines the source file search list for the @command{ACS COMPILE} command.
25117 @item @command{ACS SHOW LIBRARY}
25118 @tab Directory (*)@*
25119 Lists information about one or more program libraries.
25121 @item @command{ACS SHOW PROGRAM}
25122 @tab [No equivalent]@*
25123 Lists information about the execution closure of one or
25124 more units in the program library.
25126 @item @command{ACS SHOW SOURCE}
25127 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25128 Shows the source file search used when compiling units.
25130 @item @command{ACS SHOW VERSION}
25131 @tab Compile with @option{VERBOSE} option
25132 Displays the version number of the compiler and program library
25135 @item @command{ACS SPAWN}
25136 @tab [No equivalent]@*
25137 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25140 @item @command{ACS VERIFY}
25141 @tab [No equivalent]@*
25142 Performs a series of consistency checks on a program library to
25143 determine whether the library structure and library files are in
25150 @section Input-Output
25153 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25154 Management Services (RMS) to perform operations on
25158 HP Ada and GNAT predefine an identical set of input-
25159 output packages. To make the use of the
25160 generic @code{TEXT_IO} operations more convenient, HP Ada
25161 provides predefined library packages that instantiate the
25162 integer and floating-point operations for the predefined
25163 integer and floating-point types as shown in the following table.
25165 @multitable @columnfractions .45 .55
25166 @item @emph{Package Name} @tab Instantiation
25168 @item @code{INTEGER_TEXT_IO}
25169 @tab @code{INTEGER_IO(INTEGER)}
25171 @item @code{SHORT_INTEGER_TEXT_IO}
25172 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25174 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25175 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25177 @item @code{FLOAT_TEXT_IO}
25178 @tab @code{FLOAT_IO(FLOAT)}
25180 @item @code{LONG_FLOAT_TEXT_IO}
25181 @tab @code{FLOAT_IO(LONG_FLOAT)}
25185 The HP Ada predefined packages and their operations
25186 are implemented using OpenVMS Alpha files and input-output
25187 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25188 Familiarity with the following is recommended:
25190 @item RMS file organizations and access methods
25192 @item OpenVMS file specifications and directories
25194 @item OpenVMS File Definition Language (FDL)
25198 GNAT provides I/O facilities that are completely
25199 compatible with HP Ada. The distribution includes the
25200 standard HP Ada versions of all I/O packages, operating
25201 in a manner compatible with HP Ada. In particular, the
25202 following packages are by default the HP Ada (Ada 83)
25203 versions of these packages rather than the renamings
25204 suggested in Annex J of the Ada Reference Manual:
25206 @item @code{TEXT_IO}
25208 @item @code{SEQUENTIAL_IO}
25210 @item @code{DIRECT_IO}
25214 The use of the standard child package syntax (for
25215 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25217 GNAT provides HP-compatible predefined instantiations
25218 of the @code{TEXT_IO} packages, and also
25219 provides the standard predefined instantiations required
25220 by the @cite{Ada Reference Manual}.
25222 For further information on how GNAT interfaces to the file
25223 system or how I/O is implemented in programs written in
25224 mixed languages, see @ref{Implementation of the Standard I/O,,,
25225 gnat_rm, GNAT Reference Manual}.
25226 This chapter covers the following:
25228 @item Standard I/O packages
25230 @item @code{FORM} strings
25232 @item @code{ADA.DIRECT_IO}
25234 @item @code{ADA.SEQUENTIAL_IO}
25236 @item @code{ADA.TEXT_IO}
25238 @item Stream pointer positioning
25240 @item Reading and writing non-regular files
25242 @item @code{GET_IMMEDIATE}
25244 @item Treating @code{TEXT_IO} files as streams
25251 @node Implementation Limits
25252 @section Implementation Limits
25255 The following table lists implementation limits for HP Ada
25257 @multitable @columnfractions .60 .20 .20
25259 @item @emph{Compilation Parameter}
25264 @item In a subprogram or entry declaration, maximum number of
25265 formal parameters that are of an unconstrained record type
25270 @item Maximum identifier length (number of characters)
25275 @item Maximum number of characters in a source line
25280 @item Maximum collection size (number of bytes)
25285 @item Maximum number of discriminants for a record type
25290 @item Maximum number of formal parameters in an entry or
25291 subprogram declaration
25296 @item Maximum number of dimensions in an array type
25301 @item Maximum number of library units and subunits in a compilation.
25306 @item Maximum number of library units and subunits in an execution.
25311 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
25312 or @code{PSECT_OBJECT}
25317 @item Maximum number of enumeration literals in an enumeration type
25323 @item Maximum number of lines in a source file
25328 @item Maximum number of bits in any object
25333 @item Maximum size of the static portion of a stack frame (approximate)
25338 @node Tools and Utilities
25339 @section Tools and Utilities
25342 The following table lists some of the OpenVMS development tools
25343 available for HP Ada, and the corresponding tools for
25344 use with @value{EDITION} on Alpha and I64 platforms.
25345 Aside from the debugger, all the OpenVMS tools identified are part
25346 of the DECset package.
25349 @c Specify table in TeX since Texinfo does a poor job
25353 \settabs\+Language-Sensitive Editor\quad
25354 &Product with HP Ada\quad
25357 &\it Product with HP Ada
25358 & \it Product with GNAT Pro\cr
25360 \+Code Management System
25364 \+Language-Sensitive Editor
25366 & emacs or HP LSE (Alpha)\cr
25376 & OpenVMS Debug (I64)\cr
25378 \+Source Code Analyzer /
25395 \+Coverage Analyzer
25399 \+Module Management
25401 & Not applicable\cr
25411 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
25412 @c the TeX version above for the printed version
25414 @c @multitable @columnfractions .3 .4 .4
25415 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
25417 @tab @i{Tool with HP Ada}
25418 @tab @i{Tool with @value{EDITION}}
25419 @item Code Management@*System
25422 @item Language-Sensitive@*Editor
25424 @tab emacs or HP LSE (Alpha)
25433 @tab OpenVMS Debug (I64)
25434 @item Source Code Analyzer /@*Cross Referencer
25438 @tab HP Digital Test@*Manager (DTM)
25440 @item Performance and@*Coverage Analyzer
25443 @item Module Management@*System
25445 @tab Not applicable
25452 @c **************************************
25453 @node Platform-Specific Information for the Run-Time Libraries
25454 @appendix Platform-Specific Information for the Run-Time Libraries
25455 @cindex Tasking and threads libraries
25456 @cindex Threads libraries and tasking
25457 @cindex Run-time libraries (platform-specific information)
25460 The GNAT run-time implementation may vary with respect to both the
25461 underlying threads library and the exception handling scheme.
25462 For threads support, one or more of the following are supplied:
25464 @item @b{native threads library}, a binding to the thread package from
25465 the underlying operating system
25467 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
25468 POSIX thread package
25472 For exception handling, either or both of two models are supplied:
25474 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
25475 Most programs should experience a substantial speed improvement by
25476 being compiled with a ZCX run-time.
25477 This is especially true for
25478 tasking applications or applications with many exception handlers.}
25479 @cindex Zero-Cost Exceptions
25480 @cindex ZCX (Zero-Cost Exceptions)
25481 which uses binder-generated tables that
25482 are interrogated at run time to locate a handler
25484 @item @b{setjmp / longjmp} (``SJLJ''),
25485 @cindex setjmp/longjmp Exception Model
25486 @cindex SJLJ (setjmp/longjmp Exception Model)
25487 which uses dynamically-set data to establish
25488 the set of handlers
25492 This appendix summarizes which combinations of threads and exception support
25493 are supplied on various GNAT platforms.
25494 It then shows how to select a particular library either
25495 permanently or temporarily,
25496 explains the properties of (and tradeoffs among) the various threads
25497 libraries, and provides some additional
25498 information about several specific platforms.
25501 * Summary of Run-Time Configurations::
25502 * Specifying a Run-Time Library::
25503 * Choosing the Scheduling Policy::
25504 * Solaris-Specific Considerations::
25505 * Linux-Specific Considerations::
25506 * AIX-Specific Considerations::
25507 * Irix-Specific Considerations::
25508 * RTX-Specific Considerations::
25511 @node Summary of Run-Time Configurations
25512 @section Summary of Run-Time Configurations
25514 @multitable @columnfractions .30 .70
25515 @item @b{alpha-openvms}
25516 @item @code{@ @ }@i{rts-native (default)}
25517 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25518 @item @code{@ @ @ @ }Exceptions @tab ZCX
25520 @item @b{alpha-tru64}
25521 @item @code{@ @ }@i{rts-native (default)}
25522 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25523 @item @code{@ @ @ @ }Exceptions @tab ZCX
25525 @item @code{@ @ }@i{rts-sjlj}
25526 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25527 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25529 @item @b{ia64-hp_linux}
25530 @item @code{@ @ }@i{rts-native (default)}
25531 @item @code{@ @ @ @ }Tasking @tab pthread library
25532 @item @code{@ @ @ @ }Exceptions @tab ZCX
25534 @item @b{ia64-hpux}
25535 @item @code{@ @ }@i{rts-native (default)}
25536 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25537 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25539 @item @b{ia64-openvms}
25540 @item @code{@ @ }@i{rts-native (default)}
25541 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25542 @item @code{@ @ @ @ }Exceptions @tab ZCX
25544 @item @b{ia64-sgi_linux}
25545 @item @code{@ @ }@i{rts-native (default)}
25546 @item @code{@ @ @ @ }Tasking @tab pthread library
25547 @item @code{@ @ @ @ }Exceptions @tab ZCX
25549 @item @b{mips-irix}
25550 @item @code{@ @ }@i{rts-native (default)}
25551 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
25552 @item @code{@ @ @ @ }Exceptions @tab ZCX
25555 @item @code{@ @ }@i{rts-native (default)}
25556 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25557 @item @code{@ @ @ @ }Exceptions @tab ZCX
25559 @item @code{@ @ }@i{rts-sjlj}
25560 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25561 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25564 @item @code{@ @ }@i{rts-native (default)}
25565 @item @code{@ @ @ @ }Tasking @tab native AIX threads
25566 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25568 @item @b{ppc-darwin}
25569 @item @code{@ @ }@i{rts-native (default)}
25570 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
25571 @item @code{@ @ @ @ }Exceptions @tab ZCX
25573 @item @b{sparc-solaris} @tab
25574 @item @code{@ @ }@i{rts-native (default)}
25575 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25576 @item @code{@ @ @ @ }Exceptions @tab ZCX
25578 @item @code{@ @ }@i{rts-pthread}
25579 @item @code{@ @ @ @ }Tasking @tab pthread library
25580 @item @code{@ @ @ @ }Exceptions @tab ZCX
25582 @item @code{@ @ }@i{rts-sjlj}
25583 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25584 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25586 @item @b{sparc64-solaris} @tab
25587 @item @code{@ @ }@i{rts-native (default)}
25588 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25589 @item @code{@ @ @ @ }Exceptions @tab ZCX
25591 @item @b{x86-linux}
25592 @item @code{@ @ }@i{rts-native (default)}
25593 @item @code{@ @ @ @ }Tasking @tab pthread library
25594 @item @code{@ @ @ @ }Exceptions @tab ZCX
25596 @item @code{@ @ }@i{rts-sjlj}
25597 @item @code{@ @ @ @ }Tasking @tab pthread library
25598 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25601 @item @code{@ @ }@i{rts-native (default)}
25602 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
25603 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25605 @item @b{x86-solaris}
25606 @item @code{@ @ }@i{rts-native (default)}
25607 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
25608 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25610 @item @b{x86-windows}
25611 @item @code{@ @ }@i{rts-native (default)}
25612 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25613 @item @code{@ @ @ @ }Exceptions @tab ZCX
25615 @item @code{@ @ }@i{rts-sjlj (default)}
25616 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25617 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25619 @item @b{x86-windows-rtx}
25620 @item @code{@ @ }@i{rts-rtx-rtss (default)}
25621 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
25622 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25624 @item @code{@ @ }@i{rts-rtx-w32}
25625 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
25626 @item @code{@ @ @ @ }Exceptions @tab ZCX
25628 @item @b{x86_64-linux}
25629 @item @code{@ @ }@i{rts-native (default)}
25630 @item @code{@ @ @ @ }Tasking @tab pthread library
25631 @item @code{@ @ @ @ }Exceptions @tab ZCX
25633 @item @code{@ @ }@i{rts-sjlj}
25634 @item @code{@ @ @ @ }Tasking @tab pthread library
25635 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25639 @node Specifying a Run-Time Library
25640 @section Specifying a Run-Time Library
25643 The @file{adainclude} subdirectory containing the sources of the GNAT
25644 run-time library, and the @file{adalib} subdirectory containing the
25645 @file{ALI} files and the static and/or shared GNAT library, are located
25646 in the gcc target-dependent area:
25649 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
25653 As indicated above, on some platforms several run-time libraries are supplied.
25654 These libraries are installed in the target dependent area and
25655 contain a complete source and binary subdirectory. The detailed description
25656 below explains the differences between the different libraries in terms of
25657 their thread support.
25659 The default run-time library (when GNAT is installed) is @emph{rts-native}.
25660 This default run time is selected by the means of soft links.
25661 For example on x86-linux:
25667 +--- adainclude----------+
25669 +--- adalib-----------+ |
25671 +--- rts-native | |
25673 | +--- adainclude <---+
25675 | +--- adalib <----+
25686 If the @i{rts-sjlj} library is to be selected on a permanent basis,
25687 these soft links can be modified with the following commands:
25691 $ rm -f adainclude adalib
25692 $ ln -s rts-sjlj/adainclude adainclude
25693 $ ln -s rts-sjlj/adalib adalib
25697 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
25698 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
25699 @file{$target/ada_object_path}.
25701 Selecting another run-time library temporarily can be
25702 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
25703 @cindex @option{--RTS} option
25705 @node Choosing the Scheduling Policy
25706 @section Choosing the Scheduling Policy
25709 When using a POSIX threads implementation, you have a choice of several
25710 scheduling policies: @code{SCHED_FIFO},
25711 @cindex @code{SCHED_FIFO} scheduling policy
25713 @cindex @code{SCHED_RR} scheduling policy
25714 and @code{SCHED_OTHER}.
25715 @cindex @code{SCHED_OTHER} scheduling policy
25716 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
25717 or @code{SCHED_RR} requires special (e.g., root) privileges.
25719 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
25721 @cindex @code{SCHED_FIFO} scheduling policy
25722 you can use one of the following:
25726 @code{pragma Time_Slice (0.0)}
25727 @cindex pragma Time_Slice
25729 the corresponding binder option @option{-T0}
25730 @cindex @option{-T0} option
25732 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
25733 @cindex pragma Task_Dispatching_Policy
25737 To specify @code{SCHED_RR},
25738 @cindex @code{SCHED_RR} scheduling policy
25739 you should use @code{pragma Time_Slice} with a
25740 value greater than @code{0.0}, or else use the corresponding @option{-T}
25743 @node Solaris-Specific Considerations
25744 @section Solaris-Specific Considerations
25745 @cindex Solaris Sparc threads libraries
25748 This section addresses some topics related to the various threads libraries
25752 * Solaris Threads Issues::
25755 @node Solaris Threads Issues
25756 @subsection Solaris Threads Issues
25759 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
25760 library based on POSIX threads --- @emph{rts-pthread}.
25761 @cindex rts-pthread threads library
25762 This run-time library has the advantage of being mostly shared across all
25763 POSIX-compliant thread implementations, and it also provides under
25764 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
25765 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
25766 and @code{PTHREAD_PRIO_PROTECT}
25767 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
25768 semantics that can be selected using the predefined pragma
25769 @code{Locking_Policy}
25770 @cindex pragma Locking_Policy (under rts-pthread)
25772 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
25773 @cindex @code{Inheritance_Locking} (under rts-pthread)
25774 @cindex @code{Ceiling_Locking} (under rts-pthread)
25776 As explained above, the native run-time library is based on the Solaris thread
25777 library (@code{libthread}) and is the default library.
25779 When the Solaris threads library is used (this is the default), programs
25780 compiled with GNAT can automatically take advantage of
25781 and can thus execute on multiple processors.
25782 The user can alternatively specify a processor on which the program should run
25783 to emulate a single-processor system. The multiprocessor / uniprocessor choice
25785 setting the environment variable @env{GNAT_PROCESSOR}
25786 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
25787 to one of the following:
25791 Use the default configuration (run the program on all
25792 available processors) - this is the same as having @code{GNAT_PROCESSOR}
25796 Let the run-time implementation choose one processor and run the program on
25799 @item 0 .. Last_Proc
25800 Run the program on the specified processor.
25801 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
25802 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
25805 @node Linux-Specific Considerations
25806 @section Linux-Specific Considerations
25807 @cindex Linux threads libraries
25810 On GNU/Linux without NPTL support (usually system with GNU C Library
25811 older than 2.3), the signal model is not POSIX compliant, which means
25812 that to send a signal to the process, you need to send the signal to all
25813 threads, e.g.@: by using @code{killpg()}.
25815 @node AIX-Specific Considerations
25816 @section AIX-Specific Considerations
25817 @cindex AIX resolver library
25820 On AIX, the resolver library initializes some internal structure on
25821 the first call to @code{get*by*} functions, which are used to implement
25822 @code{GNAT.Sockets.Get_Host_By_Name} and
25823 @code{GNAT.Sockets.Get_Host_By_Address}.
25824 If such initialization occurs within an Ada task, and the stack size for
25825 the task is the default size, a stack overflow may occur.
25827 To avoid this overflow, the user should either ensure that the first call
25828 to @code{GNAT.Sockets.Get_Host_By_Name} or
25829 @code{GNAT.Sockets.Get_Host_By_Addrss}
25830 occurs in the environment task, or use @code{pragma Storage_Size} to
25831 specify a sufficiently large size for the stack of the task that contains
25834 @node Irix-Specific Considerations
25835 @section Irix-Specific Considerations
25836 @cindex Irix libraries
25839 The GCC support libraries coming with the Irix compiler have moved to
25840 their canonical place with respect to the general Irix ABI related
25841 conventions. Running applications built with the default shared GNAT
25842 run-time now requires the LD_LIBRARY_PATH environment variable to
25843 include this location. A possible way to achieve this is to issue the
25844 following command line on a bash prompt:
25848 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
25852 @node RTX-Specific Considerations
25853 @section RTX-Specific Considerations
25854 @cindex RTX libraries
25857 The Real-time Extension (RTX) to Windows is based on the Windows Win32
25858 API. Applications can be built to work in two different modes:
25862 Windows executables that run in Ring 3 to utilize memory protection
25863 (@emph{rts-rtx-w32}).
25866 Real-time subsystem (RTSS) executables that run in Ring 0, where
25867 performance can be optimized with RTSS applications taking precedent
25868 over all Windows applications (@emph{rts-rtx-rtss}).
25872 @c *******************************
25873 @node Example of Binder Output File
25874 @appendix Example of Binder Output File
25877 This Appendix displays the source code for @command{gnatbind}'s output
25878 file generated for a simple ``Hello World'' program.
25879 Comments have been added for clarification purposes.
25881 @smallexample @c adanocomment
25885 -- The package is called Ada_Main unless this name is actually used
25886 -- as a unit name in the partition, in which case some other unique
25890 package ada_main is
25892 Elab_Final_Code : Integer;
25893 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
25895 -- The main program saves the parameters (argument count,
25896 -- argument values, environment pointer) in global variables
25897 -- for later access by other units including
25898 -- Ada.Command_Line.
25900 gnat_argc : Integer;
25901 gnat_argv : System.Address;
25902 gnat_envp : System.Address;
25904 -- The actual variables are stored in a library routine. This
25905 -- is useful for some shared library situations, where there
25906 -- are problems if variables are not in the library.
25908 pragma Import (C, gnat_argc);
25909 pragma Import (C, gnat_argv);
25910 pragma Import (C, gnat_envp);
25912 -- The exit status is similarly an external location
25914 gnat_exit_status : Integer;
25915 pragma Import (C, gnat_exit_status);
25917 GNAT_Version : constant String :=
25918 "GNAT Version: 6.0.0w (20061115)";
25919 pragma Export (C, GNAT_Version, "__gnat_version");
25921 -- This is the generated adafinal routine that performs
25922 -- finalization at the end of execution. In the case where
25923 -- Ada is the main program, this main program makes a call
25924 -- to adafinal at program termination.
25926 procedure adafinal;
25927 pragma Export (C, adafinal, "adafinal");
25929 -- This is the generated adainit routine that performs
25930 -- initialization at the start of execution. In the case
25931 -- where Ada is the main program, this main program makes
25932 -- a call to adainit at program startup.
25935 pragma Export (C, adainit, "adainit");
25937 -- This routine is called at the start of execution. It is
25938 -- a dummy routine that is used by the debugger to breakpoint
25939 -- at the start of execution.
25941 procedure Break_Start;
25942 pragma Import (C, Break_Start, "__gnat_break_start");
25944 -- This is the actual generated main program (it would be
25945 -- suppressed if the no main program switch were used). As
25946 -- required by standard system conventions, this program has
25947 -- the external name main.
25951 argv : System.Address;
25952 envp : System.Address)
25954 pragma Export (C, main, "main");
25956 -- The following set of constants give the version
25957 -- identification values for every unit in the bound
25958 -- partition. This identification is computed from all
25959 -- dependent semantic units, and corresponds to the
25960 -- string that would be returned by use of the
25961 -- Body_Version or Version attributes.
25963 type Version_32 is mod 2 ** 32;
25964 u00001 : constant Version_32 := 16#7880BEB3#;
25965 u00002 : constant Version_32 := 16#0D24CBD0#;
25966 u00003 : constant Version_32 := 16#3283DBEB#;
25967 u00004 : constant Version_32 := 16#2359F9ED#;
25968 u00005 : constant Version_32 := 16#664FB847#;
25969 u00006 : constant Version_32 := 16#68E803DF#;
25970 u00007 : constant Version_32 := 16#5572E604#;
25971 u00008 : constant Version_32 := 16#46B173D8#;
25972 u00009 : constant Version_32 := 16#156A40CF#;
25973 u00010 : constant Version_32 := 16#033DABE0#;
25974 u00011 : constant Version_32 := 16#6AB38FEA#;
25975 u00012 : constant Version_32 := 16#22B6217D#;
25976 u00013 : constant Version_32 := 16#68A22947#;
25977 u00014 : constant Version_32 := 16#18CC4A56#;
25978 u00015 : constant Version_32 := 16#08258E1B#;
25979 u00016 : constant Version_32 := 16#367D5222#;
25980 u00017 : constant Version_32 := 16#20C9ECA4#;
25981 u00018 : constant Version_32 := 16#50D32CB6#;
25982 u00019 : constant Version_32 := 16#39A8BB77#;
25983 u00020 : constant Version_32 := 16#5CF8FA2B#;
25984 u00021 : constant Version_32 := 16#2F1EB794#;
25985 u00022 : constant Version_32 := 16#31AB6444#;
25986 u00023 : constant Version_32 := 16#1574B6E9#;
25987 u00024 : constant Version_32 := 16#5109C189#;
25988 u00025 : constant Version_32 := 16#56D770CD#;
25989 u00026 : constant Version_32 := 16#02F9DE3D#;
25990 u00027 : constant Version_32 := 16#08AB6B2C#;
25991 u00028 : constant Version_32 := 16#3FA37670#;
25992 u00029 : constant Version_32 := 16#476457A0#;
25993 u00030 : constant Version_32 := 16#731E1B6E#;
25994 u00031 : constant Version_32 := 16#23C2E789#;
25995 u00032 : constant Version_32 := 16#0F1BD6A1#;
25996 u00033 : constant Version_32 := 16#7C25DE96#;
25997 u00034 : constant Version_32 := 16#39ADFFA2#;
25998 u00035 : constant Version_32 := 16#571DE3E7#;
25999 u00036 : constant Version_32 := 16#5EB646AB#;
26000 u00037 : constant Version_32 := 16#4249379B#;
26001 u00038 : constant Version_32 := 16#0357E00A#;
26002 u00039 : constant Version_32 := 16#3784FB72#;
26003 u00040 : constant Version_32 := 16#2E723019#;
26004 u00041 : constant Version_32 := 16#623358EA#;
26005 u00042 : constant Version_32 := 16#107F9465#;
26006 u00043 : constant Version_32 := 16#6843F68A#;
26007 u00044 : constant Version_32 := 16#63305874#;
26008 u00045 : constant Version_32 := 16#31E56CE1#;
26009 u00046 : constant Version_32 := 16#02917970#;
26010 u00047 : constant Version_32 := 16#6CCBA70E#;
26011 u00048 : constant Version_32 := 16#41CD4204#;
26012 u00049 : constant Version_32 := 16#572E3F58#;
26013 u00050 : constant Version_32 := 16#20729FF5#;
26014 u00051 : constant Version_32 := 16#1D4F93E8#;
26015 u00052 : constant Version_32 := 16#30B2EC3D#;
26016 u00053 : constant Version_32 := 16#34054F96#;
26017 u00054 : constant Version_32 := 16#5A199860#;
26018 u00055 : constant Version_32 := 16#0E7F912B#;
26019 u00056 : constant Version_32 := 16#5760634A#;
26020 u00057 : constant Version_32 := 16#5D851835#;
26022 -- The following Export pragmas export the version numbers
26023 -- with symbolic names ending in B (for body) or S
26024 -- (for spec) so that they can be located in a link. The
26025 -- information provided here is sufficient to track down
26026 -- the exact versions of units used in a given build.
26028 pragma Export (C, u00001, "helloB");
26029 pragma Export (C, u00002, "system__standard_libraryB");
26030 pragma Export (C, u00003, "system__standard_libraryS");
26031 pragma Export (C, u00004, "adaS");
26032 pragma Export (C, u00005, "ada__text_ioB");
26033 pragma Export (C, u00006, "ada__text_ioS");
26034 pragma Export (C, u00007, "ada__exceptionsB");
26035 pragma Export (C, u00008, "ada__exceptionsS");
26036 pragma Export (C, u00009, "gnatS");
26037 pragma Export (C, u00010, "gnat__heap_sort_aB");
26038 pragma Export (C, u00011, "gnat__heap_sort_aS");
26039 pragma Export (C, u00012, "systemS");
26040 pragma Export (C, u00013, "system__exception_tableB");
26041 pragma Export (C, u00014, "system__exception_tableS");
26042 pragma Export (C, u00015, "gnat__htableB");
26043 pragma Export (C, u00016, "gnat__htableS");
26044 pragma Export (C, u00017, "system__exceptionsS");
26045 pragma Export (C, u00018, "system__machine_state_operationsB");
26046 pragma Export (C, u00019, "system__machine_state_operationsS");
26047 pragma Export (C, u00020, "system__machine_codeS");
26048 pragma Export (C, u00021, "system__storage_elementsB");
26049 pragma Export (C, u00022, "system__storage_elementsS");
26050 pragma Export (C, u00023, "system__secondary_stackB");
26051 pragma Export (C, u00024, "system__secondary_stackS");
26052 pragma Export (C, u00025, "system__parametersB");
26053 pragma Export (C, u00026, "system__parametersS");
26054 pragma Export (C, u00027, "system__soft_linksB");
26055 pragma Export (C, u00028, "system__soft_linksS");
26056 pragma Export (C, u00029, "system__stack_checkingB");
26057 pragma Export (C, u00030, "system__stack_checkingS");
26058 pragma Export (C, u00031, "system__tracebackB");
26059 pragma Export (C, u00032, "system__tracebackS");
26060 pragma Export (C, u00033, "ada__streamsS");
26061 pragma Export (C, u00034, "ada__tagsB");
26062 pragma Export (C, u00035, "ada__tagsS");
26063 pragma Export (C, u00036, "system__string_opsB");
26064 pragma Export (C, u00037, "system__string_opsS");
26065 pragma Export (C, u00038, "interfacesS");
26066 pragma Export (C, u00039, "interfaces__c_streamsB");
26067 pragma Export (C, u00040, "interfaces__c_streamsS");
26068 pragma Export (C, u00041, "system__file_ioB");
26069 pragma Export (C, u00042, "system__file_ioS");
26070 pragma Export (C, u00043, "ada__finalizationB");
26071 pragma Export (C, u00044, "ada__finalizationS");
26072 pragma Export (C, u00045, "system__finalization_rootB");
26073 pragma Export (C, u00046, "system__finalization_rootS");
26074 pragma Export (C, u00047, "system__finalization_implementationB");
26075 pragma Export (C, u00048, "system__finalization_implementationS");
26076 pragma Export (C, u00049, "system__string_ops_concat_3B");
26077 pragma Export (C, u00050, "system__string_ops_concat_3S");
26078 pragma Export (C, u00051, "system__stream_attributesB");
26079 pragma Export (C, u00052, "system__stream_attributesS");
26080 pragma Export (C, u00053, "ada__io_exceptionsS");
26081 pragma Export (C, u00054, "system__unsigned_typesS");
26082 pragma Export (C, u00055, "system__file_control_blockS");
26083 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26084 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26086 -- BEGIN ELABORATION ORDER
26089 -- gnat.heap_sort_a (spec)
26090 -- gnat.heap_sort_a (body)
26091 -- gnat.htable (spec)
26092 -- gnat.htable (body)
26093 -- interfaces (spec)
26095 -- system.machine_code (spec)
26096 -- system.parameters (spec)
26097 -- system.parameters (body)
26098 -- interfaces.c_streams (spec)
26099 -- interfaces.c_streams (body)
26100 -- system.standard_library (spec)
26101 -- ada.exceptions (spec)
26102 -- system.exception_table (spec)
26103 -- system.exception_table (body)
26104 -- ada.io_exceptions (spec)
26105 -- system.exceptions (spec)
26106 -- system.storage_elements (spec)
26107 -- system.storage_elements (body)
26108 -- system.machine_state_operations (spec)
26109 -- system.machine_state_operations (body)
26110 -- system.secondary_stack (spec)
26111 -- system.stack_checking (spec)
26112 -- system.soft_links (spec)
26113 -- system.soft_links (body)
26114 -- system.stack_checking (body)
26115 -- system.secondary_stack (body)
26116 -- system.standard_library (body)
26117 -- system.string_ops (spec)
26118 -- system.string_ops (body)
26121 -- ada.streams (spec)
26122 -- system.finalization_root (spec)
26123 -- system.finalization_root (body)
26124 -- system.string_ops_concat_3 (spec)
26125 -- system.string_ops_concat_3 (body)
26126 -- system.traceback (spec)
26127 -- system.traceback (body)
26128 -- ada.exceptions (body)
26129 -- system.unsigned_types (spec)
26130 -- system.stream_attributes (spec)
26131 -- system.stream_attributes (body)
26132 -- system.finalization_implementation (spec)
26133 -- system.finalization_implementation (body)
26134 -- ada.finalization (spec)
26135 -- ada.finalization (body)
26136 -- ada.finalization.list_controller (spec)
26137 -- ada.finalization.list_controller (body)
26138 -- system.file_control_block (spec)
26139 -- system.file_io (spec)
26140 -- system.file_io (body)
26141 -- ada.text_io (spec)
26142 -- ada.text_io (body)
26144 -- END ELABORATION ORDER
26148 -- The following source file name pragmas allow the generated file
26149 -- names to be unique for different main programs. They are needed
26150 -- since the package name will always be Ada_Main.
26152 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26153 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26155 -- Generated package body for Ada_Main starts here
26157 package body ada_main is
26159 -- The actual finalization is performed by calling the
26160 -- library routine in System.Standard_Library.Adafinal
26162 procedure Do_Finalize;
26163 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26170 procedure adainit is
26172 -- These booleans are set to True once the associated unit has
26173 -- been elaborated. It is also used to avoid elaborating the
26174 -- same unit twice.
26177 pragma Import (Ada, E040, "interfaces__c_streams_E");
26180 pragma Import (Ada, E008, "ada__exceptions_E");
26183 pragma Import (Ada, E014, "system__exception_table_E");
26186 pragma Import (Ada, E053, "ada__io_exceptions_E");
26189 pragma Import (Ada, E017, "system__exceptions_E");
26192 pragma Import (Ada, E024, "system__secondary_stack_E");
26195 pragma Import (Ada, E030, "system__stack_checking_E");
26198 pragma Import (Ada, E028, "system__soft_links_E");
26201 pragma Import (Ada, E035, "ada__tags_E");
26204 pragma Import (Ada, E033, "ada__streams_E");
26207 pragma Import (Ada, E046, "system__finalization_root_E");
26210 pragma Import (Ada, E048, "system__finalization_implementation_E");
26213 pragma Import (Ada, E044, "ada__finalization_E");
26216 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26219 pragma Import (Ada, E055, "system__file_control_block_E");
26222 pragma Import (Ada, E042, "system__file_io_E");
26225 pragma Import (Ada, E006, "ada__text_io_E");
26227 -- Set_Globals is a library routine that stores away the
26228 -- value of the indicated set of global values in global
26229 -- variables within the library.
26231 procedure Set_Globals
26232 (Main_Priority : Integer;
26233 Time_Slice_Value : Integer;
26234 WC_Encoding : Character;
26235 Locking_Policy : Character;
26236 Queuing_Policy : Character;
26237 Task_Dispatching_Policy : Character;
26238 Adafinal : System.Address;
26239 Unreserve_All_Interrupts : Integer;
26240 Exception_Tracebacks : Integer);
26241 @findex __gnat_set_globals
26242 pragma Import (C, Set_Globals, "__gnat_set_globals");
26244 -- SDP_Table_Build is a library routine used to build the
26245 -- exception tables. See unit Ada.Exceptions in files
26246 -- a-except.ads/adb for full details of how zero cost
26247 -- exception handling works. This procedure, the call to
26248 -- it, and the two following tables are all omitted if the
26249 -- build is in longjmp/setjmp exception mode.
26251 @findex SDP_Table_Build
26252 @findex Zero Cost Exceptions
26253 procedure SDP_Table_Build
26254 (SDP_Addresses : System.Address;
26255 SDP_Count : Natural;
26256 Elab_Addresses : System.Address;
26257 Elab_Addr_Count : Natural);
26258 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
26260 -- Table of Unit_Exception_Table addresses. Used for zero
26261 -- cost exception handling to build the top level table.
26263 ST : aliased constant array (1 .. 23) of System.Address := (
26265 Ada.Text_Io'UET_Address,
26266 Ada.Exceptions'UET_Address,
26267 Gnat.Heap_Sort_A'UET_Address,
26268 System.Exception_Table'UET_Address,
26269 System.Machine_State_Operations'UET_Address,
26270 System.Secondary_Stack'UET_Address,
26271 System.Parameters'UET_Address,
26272 System.Soft_Links'UET_Address,
26273 System.Stack_Checking'UET_Address,
26274 System.Traceback'UET_Address,
26275 Ada.Streams'UET_Address,
26276 Ada.Tags'UET_Address,
26277 System.String_Ops'UET_Address,
26278 Interfaces.C_Streams'UET_Address,
26279 System.File_Io'UET_Address,
26280 Ada.Finalization'UET_Address,
26281 System.Finalization_Root'UET_Address,
26282 System.Finalization_Implementation'UET_Address,
26283 System.String_Ops_Concat_3'UET_Address,
26284 System.Stream_Attributes'UET_Address,
26285 System.File_Control_Block'UET_Address,
26286 Ada.Finalization.List_Controller'UET_Address);
26288 -- Table of addresses of elaboration routines. Used for
26289 -- zero cost exception handling to make sure these
26290 -- addresses are included in the top level procedure
26293 EA : aliased constant array (1 .. 23) of System.Address := (
26294 adainit'Code_Address,
26295 Do_Finalize'Code_Address,
26296 Ada.Exceptions'Elab_Spec'Address,
26297 System.Exceptions'Elab_Spec'Address,
26298 Interfaces.C_Streams'Elab_Spec'Address,
26299 System.Exception_Table'Elab_Body'Address,
26300 Ada.Io_Exceptions'Elab_Spec'Address,
26301 System.Stack_Checking'Elab_Spec'Address,
26302 System.Soft_Links'Elab_Body'Address,
26303 System.Secondary_Stack'Elab_Body'Address,
26304 Ada.Tags'Elab_Spec'Address,
26305 Ada.Tags'Elab_Body'Address,
26306 Ada.Streams'Elab_Spec'Address,
26307 System.Finalization_Root'Elab_Spec'Address,
26308 Ada.Exceptions'Elab_Body'Address,
26309 System.Finalization_Implementation'Elab_Spec'Address,
26310 System.Finalization_Implementation'Elab_Body'Address,
26311 Ada.Finalization'Elab_Spec'Address,
26312 Ada.Finalization.List_Controller'Elab_Spec'Address,
26313 System.File_Control_Block'Elab_Spec'Address,
26314 System.File_Io'Elab_Body'Address,
26315 Ada.Text_Io'Elab_Spec'Address,
26316 Ada.Text_Io'Elab_Body'Address);
26318 -- Start of processing for adainit
26322 -- Call SDP_Table_Build to build the top level procedure
26323 -- table for zero cost exception handling (omitted in
26324 -- longjmp/setjmp mode).
26326 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
26328 -- Call Set_Globals to record various information for
26329 -- this partition. The values are derived by the binder
26330 -- from information stored in the ali files by the compiler.
26332 @findex __gnat_set_globals
26334 (Main_Priority => -1,
26335 -- Priority of main program, -1 if no pragma Priority used
26337 Time_Slice_Value => -1,
26338 -- Time slice from Time_Slice pragma, -1 if none used
26340 WC_Encoding => 'b',
26341 -- Wide_Character encoding used, default is brackets
26343 Locking_Policy => ' ',
26344 -- Locking_Policy used, default of space means not
26345 -- specified, otherwise it is the first character of
26346 -- the policy name.
26348 Queuing_Policy => ' ',
26349 -- Queuing_Policy used, default of space means not
26350 -- specified, otherwise it is the first character of
26351 -- the policy name.
26353 Task_Dispatching_Policy => ' ',
26354 -- Task_Dispatching_Policy used, default of space means
26355 -- not specified, otherwise first character of the
26358 Adafinal => System.Null_Address,
26359 -- Address of Adafinal routine, not used anymore
26361 Unreserve_All_Interrupts => 0,
26362 -- Set true if pragma Unreserve_All_Interrupts was used
26364 Exception_Tracebacks => 0);
26365 -- Indicates if exception tracebacks are enabled
26367 Elab_Final_Code := 1;
26369 -- Now we have the elaboration calls for all units in the partition.
26370 -- The Elab_Spec and Elab_Body attributes generate references to the
26371 -- implicit elaboration procedures generated by the compiler for
26372 -- each unit that requires elaboration.
26375 Interfaces.C_Streams'Elab_Spec;
26379 Ada.Exceptions'Elab_Spec;
26382 System.Exception_Table'Elab_Body;
26386 Ada.Io_Exceptions'Elab_Spec;
26390 System.Exceptions'Elab_Spec;
26394 System.Stack_Checking'Elab_Spec;
26397 System.Soft_Links'Elab_Body;
26402 System.Secondary_Stack'Elab_Body;
26406 Ada.Tags'Elab_Spec;
26409 Ada.Tags'Elab_Body;
26413 Ada.Streams'Elab_Spec;
26417 System.Finalization_Root'Elab_Spec;
26421 Ada.Exceptions'Elab_Body;
26425 System.Finalization_Implementation'Elab_Spec;
26428 System.Finalization_Implementation'Elab_Body;
26432 Ada.Finalization'Elab_Spec;
26436 Ada.Finalization.List_Controller'Elab_Spec;
26440 System.File_Control_Block'Elab_Spec;
26444 System.File_Io'Elab_Body;
26448 Ada.Text_Io'Elab_Spec;
26451 Ada.Text_Io'Elab_Body;
26455 Elab_Final_Code := 0;
26463 procedure adafinal is
26472 -- main is actually a function, as in the ANSI C standard,
26473 -- defined to return the exit status. The three parameters
26474 -- are the argument count, argument values and environment
26477 @findex Main Program
26480 argv : System.Address;
26481 envp : System.Address)
26484 -- The initialize routine performs low level system
26485 -- initialization using a standard library routine which
26486 -- sets up signal handling and performs any other
26487 -- required setup. The routine can be found in file
26490 @findex __gnat_initialize
26491 procedure initialize;
26492 pragma Import (C, initialize, "__gnat_initialize");
26494 -- The finalize routine performs low level system
26495 -- finalization using a standard library routine. The
26496 -- routine is found in file a-final.c and in the standard
26497 -- distribution is a dummy routine that does nothing, so
26498 -- really this is a hook for special user finalization.
26500 @findex __gnat_finalize
26501 procedure finalize;
26502 pragma Import (C, finalize, "__gnat_finalize");
26504 -- We get to the main program of the partition by using
26505 -- pragma Import because if we try to with the unit and
26506 -- call it Ada style, then not only do we waste time
26507 -- recompiling it, but also, we don't really know the right
26508 -- switches (e.g.@: identifier character set) to be used
26511 procedure Ada_Main_Program;
26512 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
26514 -- Start of processing for main
26517 -- Save global variables
26523 -- Call low level system initialization
26527 -- Call our generated Ada initialization routine
26531 -- This is the point at which we want the debugger to get
26536 -- Now we call the main program of the partition
26540 -- Perform Ada finalization
26544 -- Perform low level system finalization
26548 -- Return the proper exit status
26549 return (gnat_exit_status);
26552 -- This section is entirely comments, so it has no effect on the
26553 -- compilation of the Ada_Main package. It provides the list of
26554 -- object files and linker options, as well as some standard
26555 -- libraries needed for the link. The gnatlink utility parses
26556 -- this b~hello.adb file to read these comment lines to generate
26557 -- the appropriate command line arguments for the call to the
26558 -- system linker. The BEGIN/END lines are used for sentinels for
26559 -- this parsing operation.
26561 -- The exact file names will of course depend on the environment,
26562 -- host/target and location of files on the host system.
26564 @findex Object file list
26565 -- BEGIN Object file/option list
26568 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
26569 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
26570 -- END Object file/option list
26576 The Ada code in the above example is exactly what is generated by the
26577 binder. We have added comments to more clearly indicate the function
26578 of each part of the generated @code{Ada_Main} package.
26580 The code is standard Ada in all respects, and can be processed by any
26581 tools that handle Ada. In particular, it is possible to use the debugger
26582 in Ada mode to debug the generated @code{Ada_Main} package. For example,
26583 suppose that for reasons that you do not understand, your program is crashing
26584 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
26585 you can place a breakpoint on the call:
26587 @smallexample @c ada
26588 Ada.Text_Io'Elab_Body;
26592 and trace the elaboration routine for this package to find out where
26593 the problem might be (more usually of course you would be debugging
26594 elaboration code in your own application).
26596 @node Elaboration Order Handling in GNAT
26597 @appendix Elaboration Order Handling in GNAT
26598 @cindex Order of elaboration
26599 @cindex Elaboration control
26602 * Elaboration Code::
26603 * Checking the Elaboration Order::
26604 * Controlling the Elaboration Order::
26605 * Controlling Elaboration in GNAT - Internal Calls::
26606 * Controlling Elaboration in GNAT - External Calls::
26607 * Default Behavior in GNAT - Ensuring Safety::
26608 * Treatment of Pragma Elaborate::
26609 * Elaboration Issues for Library Tasks::
26610 * Mixing Elaboration Models::
26611 * What to Do If the Default Elaboration Behavior Fails::
26612 * Elaboration for Access-to-Subprogram Values::
26613 * Summary of Procedures for Elaboration Control::
26614 * Other Elaboration Order Considerations::
26618 This chapter describes the handling of elaboration code in Ada and
26619 in GNAT, and discusses how the order of elaboration of program units can
26620 be controlled in GNAT, either automatically or with explicit programming
26623 @node Elaboration Code
26624 @section Elaboration Code
26627 Ada provides rather general mechanisms for executing code at elaboration
26628 time, that is to say before the main program starts executing. Such code arises
26632 @item Initializers for variables.
26633 Variables declared at the library level, in package specs or bodies, can
26634 require initialization that is performed at elaboration time, as in:
26635 @smallexample @c ada
26637 Sqrt_Half : Float := Sqrt (0.5);
26641 @item Package initialization code
26642 Code in a @code{BEGIN-END} section at the outer level of a package body is
26643 executed as part of the package body elaboration code.
26645 @item Library level task allocators
26646 Tasks that are declared using task allocators at the library level
26647 start executing immediately and hence can execute at elaboration time.
26651 Subprogram calls are possible in any of these contexts, which means that
26652 any arbitrary part of the program may be executed as part of the elaboration
26653 code. It is even possible to write a program which does all its work at
26654 elaboration time, with a null main program, although stylistically this
26655 would usually be considered an inappropriate way to structure
26658 An important concern arises in the context of elaboration code:
26659 we have to be sure that it is executed in an appropriate order. What we
26660 have is a series of elaboration code sections, potentially one section
26661 for each unit in the program. It is important that these execute
26662 in the correct order. Correctness here means that, taking the above
26663 example of the declaration of @code{Sqrt_Half},
26664 if some other piece of
26665 elaboration code references @code{Sqrt_Half},
26666 then it must run after the
26667 section of elaboration code that contains the declaration of
26670 There would never be any order of elaboration problem if we made a rule
26671 that whenever you @code{with} a unit, you must elaborate both the spec and body
26672 of that unit before elaborating the unit doing the @code{with}'ing:
26674 @smallexample @c ada
26678 package Unit_2 is @dots{}
26684 would require that both the body and spec of @code{Unit_1} be elaborated
26685 before the spec of @code{Unit_2}. However, a rule like that would be far too
26686 restrictive. In particular, it would make it impossible to have routines
26687 in separate packages that were mutually recursive.
26689 You might think that a clever enough compiler could look at the actual
26690 elaboration code and determine an appropriate correct order of elaboration,
26691 but in the general case, this is not possible. Consider the following
26694 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
26696 the variable @code{Sqrt_1}, which is declared in the elaboration code
26697 of the body of @code{Unit_1}:
26699 @smallexample @c ada
26701 Sqrt_1 : Float := Sqrt (0.1);
26706 The elaboration code of the body of @code{Unit_1} also contains:
26708 @smallexample @c ada
26711 if expression_1 = 1 then
26712 Q := Unit_2.Func_2;
26719 @code{Unit_2} is exactly parallel,
26720 it has a procedure @code{Func_2} that references
26721 the variable @code{Sqrt_2}, which is declared in the elaboration code of
26722 the body @code{Unit_2}:
26724 @smallexample @c ada
26726 Sqrt_2 : Float := Sqrt (0.1);
26731 The elaboration code of the body of @code{Unit_2} also contains:
26733 @smallexample @c ada
26736 if expression_2 = 2 then
26737 Q := Unit_1.Func_1;
26744 Now the question is, which of the following orders of elaboration is
26769 If you carefully analyze the flow here, you will see that you cannot tell
26770 at compile time the answer to this question.
26771 If @code{expression_1} is not equal to 1,
26772 and @code{expression_2} is not equal to 2,
26773 then either order is acceptable, because neither of the function calls is
26774 executed. If both tests evaluate to true, then neither order is acceptable
26775 and in fact there is no correct order.
26777 If one of the two expressions is true, and the other is false, then one
26778 of the above orders is correct, and the other is incorrect. For example,
26779 if @code{expression_1} /= 1 and @code{expression_2} = 2,
26780 then the call to @code{Func_1}
26781 will occur, but not the call to @code{Func_2.}
26782 This means that it is essential
26783 to elaborate the body of @code{Unit_1} before
26784 the body of @code{Unit_2}, so the first
26785 order of elaboration is correct and the second is wrong.
26787 By making @code{expression_1} and @code{expression_2}
26788 depend on input data, or perhaps
26789 the time of day, we can make it impossible for the compiler or binder
26790 to figure out which of these expressions will be true, and hence it
26791 is impossible to guarantee a safe order of elaboration at run time.
26793 @node Checking the Elaboration Order
26794 @section Checking the Elaboration Order
26797 In some languages that involve the same kind of elaboration problems,
26798 e.g.@: Java and C++, the programmer is expected to worry about these
26799 ordering problems himself, and it is common to
26800 write a program in which an incorrect elaboration order gives
26801 surprising results, because it references variables before they
26803 Ada is designed to be a safe language, and a programmer-beware approach is
26804 clearly not sufficient. Consequently, the language provides three lines
26808 @item Standard rules
26809 Some standard rules restrict the possible choice of elaboration
26810 order. In particular, if you @code{with} a unit, then its spec is always
26811 elaborated before the unit doing the @code{with}. Similarly, a parent
26812 spec is always elaborated before the child spec, and finally
26813 a spec is always elaborated before its corresponding body.
26815 @item Dynamic elaboration checks
26816 @cindex Elaboration checks
26817 @cindex Checks, elaboration
26818 Dynamic checks are made at run time, so that if some entity is accessed
26819 before it is elaborated (typically by means of a subprogram call)
26820 then the exception (@code{Program_Error}) is raised.
26822 @item Elaboration control
26823 Facilities are provided for the programmer to specify the desired order
26827 Let's look at these facilities in more detail. First, the rules for
26828 dynamic checking. One possible rule would be simply to say that the
26829 exception is raised if you access a variable which has not yet been
26830 elaborated. The trouble with this approach is that it could require
26831 expensive checks on every variable reference. Instead Ada has two
26832 rules which are a little more restrictive, but easier to check, and
26836 @item Restrictions on calls
26837 A subprogram can only be called at elaboration time if its body
26838 has been elaborated. The rules for elaboration given above guarantee
26839 that the spec of the subprogram has been elaborated before the
26840 call, but not the body. If this rule is violated, then the
26841 exception @code{Program_Error} is raised.
26843 @item Restrictions on instantiations
26844 A generic unit can only be instantiated if the body of the generic
26845 unit has been elaborated. Again, the rules for elaboration given above
26846 guarantee that the spec of the generic unit has been elaborated
26847 before the instantiation, but not the body. If this rule is
26848 violated, then the exception @code{Program_Error} is raised.
26852 The idea is that if the body has been elaborated, then any variables
26853 it references must have been elaborated; by checking for the body being
26854 elaborated we guarantee that none of its references causes any
26855 trouble. As we noted above, this is a little too restrictive, because a
26856 subprogram that has no non-local references in its body may in fact be safe
26857 to call. However, it really would be unsafe to rely on this, because
26858 it would mean that the caller was aware of details of the implementation
26859 in the body. This goes against the basic tenets of Ada.
26861 A plausible implementation can be described as follows.
26862 A Boolean variable is associated with each subprogram
26863 and each generic unit. This variable is initialized to False, and is set to
26864 True at the point body is elaborated. Every call or instantiation checks the
26865 variable, and raises @code{Program_Error} if the variable is False.
26867 Note that one might think that it would be good enough to have one Boolean
26868 variable for each package, but that would not deal with cases of trying
26869 to call a body in the same package as the call
26870 that has not been elaborated yet.
26871 Of course a compiler may be able to do enough analysis to optimize away
26872 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
26873 does such optimizations, but still the easiest conceptual model is to
26874 think of there being one variable per subprogram.
26876 @node Controlling the Elaboration Order
26877 @section Controlling the Elaboration Order
26880 In the previous section we discussed the rules in Ada which ensure
26881 that @code{Program_Error} is raised if an incorrect elaboration order is
26882 chosen. This prevents erroneous executions, but we need mechanisms to
26883 specify a correct execution and avoid the exception altogether.
26884 To achieve this, Ada provides a number of features for controlling
26885 the order of elaboration. We discuss these features in this section.
26887 First, there are several ways of indicating to the compiler that a given
26888 unit has no elaboration problems:
26891 @item packages that do not require a body
26892 A library package that does not require a body does not permit
26893 a body (this rule was introduced in Ada 95).
26894 Thus if we have a such a package, as in:
26896 @smallexample @c ada
26899 package Definitions is
26901 type m is new integer;
26903 type a is array (1 .. 10) of m;
26904 type b is array (1 .. 20) of m;
26912 A package that @code{with}'s @code{Definitions} may safely instantiate
26913 @code{Definitions.Subp} because the compiler can determine that there
26914 definitely is no package body to worry about in this case
26917 @cindex pragma Pure
26919 Places sufficient restrictions on a unit to guarantee that
26920 no call to any subprogram in the unit can result in an
26921 elaboration problem. This means that the compiler does not need
26922 to worry about the point of elaboration of such units, and in
26923 particular, does not need to check any calls to any subprograms
26926 @item pragma Preelaborate
26927 @findex Preelaborate
26928 @cindex pragma Preelaborate
26929 This pragma places slightly less stringent restrictions on a unit than
26931 but these restrictions are still sufficient to ensure that there
26932 are no elaboration problems with any calls to the unit.
26934 @item pragma Elaborate_Body
26935 @findex Elaborate_Body
26936 @cindex pragma Elaborate_Body
26937 This pragma requires that the body of a unit be elaborated immediately
26938 after its spec. Suppose a unit @code{A} has such a pragma,
26939 and unit @code{B} does
26940 a @code{with} of unit @code{A}. Recall that the standard rules require
26941 the spec of unit @code{A}
26942 to be elaborated before the @code{with}'ing unit; given the pragma in
26943 @code{A}, we also know that the body of @code{A}
26944 will be elaborated before @code{B}, so
26945 that calls to @code{A} are safe and do not need a check.
26950 unlike pragma @code{Pure} and pragma @code{Preelaborate},
26952 @code{Elaborate_Body} does not guarantee that the program is
26953 free of elaboration problems, because it may not be possible
26954 to satisfy the requested elaboration order.
26955 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
26957 marks @code{Unit_1} as @code{Elaborate_Body},
26958 and not @code{Unit_2,} then the order of
26959 elaboration will be:
26971 Now that means that the call to @code{Func_1} in @code{Unit_2}
26972 need not be checked,
26973 it must be safe. But the call to @code{Func_2} in
26974 @code{Unit_1} may still fail if
26975 @code{Expression_1} is equal to 1,
26976 and the programmer must still take
26977 responsibility for this not being the case.
26979 If all units carry a pragma @code{Elaborate_Body}, then all problems are
26980 eliminated, except for calls entirely within a body, which are
26981 in any case fully under programmer control. However, using the pragma
26982 everywhere is not always possible.
26983 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
26984 we marked both of them as having pragma @code{Elaborate_Body}, then
26985 clearly there would be no possible elaboration order.
26987 The above pragmas allow a server to guarantee safe use by clients, and
26988 clearly this is the preferable approach. Consequently a good rule
26989 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
26990 and if this is not possible,
26991 mark them as @code{Elaborate_Body} if possible.
26992 As we have seen, there are situations where neither of these
26993 three pragmas can be used.
26994 So we also provide methods for clients to control the
26995 order of elaboration of the servers on which they depend:
26998 @item pragma Elaborate (unit)
27000 @cindex pragma Elaborate
27001 This pragma is placed in the context clause, after a @code{with} clause,
27002 and it requires that the body of the named unit be elaborated before
27003 the unit in which the pragma occurs. The idea is to use this pragma
27004 if the current unit calls at elaboration time, directly or indirectly,
27005 some subprogram in the named unit.
27007 @item pragma Elaborate_All (unit)
27008 @findex Elaborate_All
27009 @cindex pragma Elaborate_All
27010 This is a stronger version of the Elaborate pragma. Consider the
27014 Unit A @code{with}'s unit B and calls B.Func in elab code
27015 Unit B @code{with}'s unit C, and B.Func calls C.Func
27019 Now if we put a pragma @code{Elaborate (B)}
27020 in unit @code{A}, this ensures that the
27021 body of @code{B} is elaborated before the call, but not the
27022 body of @code{C}, so
27023 the call to @code{C.Func} could still cause @code{Program_Error} to
27026 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27027 not only that the body of the named unit be elaborated before the
27028 unit doing the @code{with}, but also the bodies of all units that the
27029 named unit uses, following @code{with} links transitively. For example,
27030 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27032 not only that the body of @code{B} be elaborated before @code{A},
27034 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27038 We are now in a position to give a usage rule in Ada for avoiding
27039 elaboration problems, at least if dynamic dispatching and access to
27040 subprogram values are not used. We will handle these cases separately
27043 The rule is simple. If a unit has elaboration code that can directly or
27044 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27045 a generic package in a @code{with}'ed unit,
27046 then if the @code{with}'ed unit does not have
27047 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27048 a pragma @code{Elaborate_All}
27049 for the @code{with}'ed unit. By following this rule a client is
27050 assured that calls can be made without risk of an exception.
27052 For generic subprogram instantiations, the rule can be relaxed to
27053 require only a pragma @code{Elaborate} since elaborating the body
27054 of a subprogram cannot cause any transitive elaboration (we are
27055 not calling the subprogram in this case, just elaborating its
27058 If this rule is not followed, then a program may be in one of four
27062 @item No order exists
27063 No order of elaboration exists which follows the rules, taking into
27064 account any @code{Elaborate}, @code{Elaborate_All},
27065 or @code{Elaborate_Body} pragmas. In
27066 this case, an Ada compiler must diagnose the situation at bind
27067 time, and refuse to build an executable program.
27069 @item One or more orders exist, all incorrect
27070 One or more acceptable elaboration orders exist, and all of them
27071 generate an elaboration order problem. In this case, the binder
27072 can build an executable program, but @code{Program_Error} will be raised
27073 when the program is run.
27075 @item Several orders exist, some right, some incorrect
27076 One or more acceptable elaboration orders exists, and some of them
27077 work, and some do not. The programmer has not controlled
27078 the order of elaboration, so the binder may or may not pick one of
27079 the correct orders, and the program may or may not raise an
27080 exception when it is run. This is the worst case, because it means
27081 that the program may fail when moved to another compiler, or even
27082 another version of the same compiler.
27084 @item One or more orders exists, all correct
27085 One ore more acceptable elaboration orders exist, and all of them
27086 work. In this case the program runs successfully. This state of
27087 affairs can be guaranteed by following the rule we gave above, but
27088 may be true even if the rule is not followed.
27092 Note that one additional advantage of following our rules on the use
27093 of @code{Elaborate} and @code{Elaborate_All}
27094 is that the program continues to stay in the ideal (all orders OK) state
27095 even if maintenance
27096 changes some bodies of some units. Conversely, if a program that does
27097 not follow this rule happens to be safe at some point, this state of affairs
27098 may deteriorate silently as a result of maintenance changes.
27100 You may have noticed that the above discussion did not mention
27101 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27102 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27103 code in the body makes calls to some other unit, so it is still necessary
27104 to use @code{Elaborate_All} on such units.
27106 @node Controlling Elaboration in GNAT - Internal Calls
27107 @section Controlling Elaboration in GNAT - Internal Calls
27110 In the case of internal calls, i.e., calls within a single package, the
27111 programmer has full control over the order of elaboration, and it is up
27112 to the programmer to elaborate declarations in an appropriate order. For
27115 @smallexample @c ada
27118 function One return Float;
27122 function One return Float is
27131 will obviously raise @code{Program_Error} at run time, because function
27132 One will be called before its body is elaborated. In this case GNAT will
27133 generate a warning that the call will raise @code{Program_Error}:
27139 2. function One return Float;
27141 4. Q : Float := One;
27143 >>> warning: cannot call "One" before body is elaborated
27144 >>> warning: Program_Error will be raised at run time
27147 6. function One return Float is
27160 Note that in this particular case, it is likely that the call is safe, because
27161 the function @code{One} does not access any global variables.
27162 Nevertheless in Ada, we do not want the validity of the check to depend on
27163 the contents of the body (think about the separate compilation case), so this
27164 is still wrong, as we discussed in the previous sections.
27166 The error is easily corrected by rearranging the declarations so that the
27167 body of @code{One} appears before the declaration containing the call
27168 (note that in Ada 95 and Ada 2005,
27169 declarations can appear in any order, so there is no restriction that
27170 would prevent this reordering, and if we write:
27172 @smallexample @c ada
27175 function One return Float;
27177 function One return Float is
27188 then all is well, no warning is generated, and no
27189 @code{Program_Error} exception
27191 Things are more complicated when a chain of subprograms is executed:
27193 @smallexample @c ada
27196 function A return Integer;
27197 function B return Integer;
27198 function C return Integer;
27200 function B return Integer is begin return A; end;
27201 function C return Integer is begin return B; end;
27205 function A return Integer is begin return 1; end;
27211 Now the call to @code{C}
27212 at elaboration time in the declaration of @code{X} is correct, because
27213 the body of @code{C} is already elaborated,
27214 and the call to @code{B} within the body of
27215 @code{C} is correct, but the call
27216 to @code{A} within the body of @code{B} is incorrect, because the body
27217 of @code{A} has not been elaborated, so @code{Program_Error}
27218 will be raised on the call to @code{A}.
27219 In this case GNAT will generate a
27220 warning that @code{Program_Error} may be
27221 raised at the point of the call. Let's look at the warning:
27227 2. function A return Integer;
27228 3. function B return Integer;
27229 4. function C return Integer;
27231 6. function B return Integer is begin return A; end;
27233 >>> warning: call to "A" before body is elaborated may
27234 raise Program_Error
27235 >>> warning: "B" called at line 7
27236 >>> warning: "C" called at line 9
27238 7. function C return Integer is begin return B; end;
27240 9. X : Integer := C;
27242 11. function A return Integer is begin return 1; end;
27252 Note that the message here says ``may raise'', instead of the direct case,
27253 where the message says ``will be raised''. That's because whether
27255 actually called depends in general on run-time flow of control.
27256 For example, if the body of @code{B} said
27258 @smallexample @c ada
27261 function B return Integer is
27263 if some-condition-depending-on-input-data then
27274 then we could not know until run time whether the incorrect call to A would
27275 actually occur, so @code{Program_Error} might
27276 or might not be raised. It is possible for a compiler to
27277 do a better job of analyzing bodies, to
27278 determine whether or not @code{Program_Error}
27279 might be raised, but it certainly
27280 couldn't do a perfect job (that would require solving the halting problem
27281 and is provably impossible), and because this is a warning anyway, it does
27282 not seem worth the effort to do the analysis. Cases in which it
27283 would be relevant are rare.
27285 In practice, warnings of either of the forms given
27286 above will usually correspond to
27287 real errors, and should be examined carefully and eliminated.
27288 In the rare case where a warning is bogus, it can be suppressed by any of
27289 the following methods:
27293 Compile with the @option{-gnatws} switch set
27296 Suppress @code{Elaboration_Check} for the called subprogram
27299 Use pragma @code{Warnings_Off} to turn warnings off for the call
27303 For the internal elaboration check case,
27304 GNAT by default generates the
27305 necessary run-time checks to ensure
27306 that @code{Program_Error} is raised if any
27307 call fails an elaboration check. Of course this can only happen if a
27308 warning has been issued as described above. The use of pragma
27309 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
27310 some of these checks, meaning that it may be possible (but is not
27311 guaranteed) for a program to be able to call a subprogram whose body
27312 is not yet elaborated, without raising a @code{Program_Error} exception.
27314 @node Controlling Elaboration in GNAT - External Calls
27315 @section Controlling Elaboration in GNAT - External Calls
27318 The previous section discussed the case in which the execution of a
27319 particular thread of elaboration code occurred entirely within a
27320 single unit. This is the easy case to handle, because a programmer
27321 has direct and total control over the order of elaboration, and
27322 furthermore, checks need only be generated in cases which are rare
27323 and which the compiler can easily detect.
27324 The situation is more complex when separate compilation is taken into account.
27325 Consider the following:
27327 @smallexample @c ada
27331 function Sqrt (Arg : Float) return Float;
27334 package body Math is
27335 function Sqrt (Arg : Float) return Float is
27344 X : Float := Math.Sqrt (0.5);
27357 where @code{Main} is the main program. When this program is executed, the
27358 elaboration code must first be executed, and one of the jobs of the
27359 binder is to determine the order in which the units of a program are
27360 to be elaborated. In this case we have four units: the spec and body
27362 the spec of @code{Stuff} and the body of @code{Main}).
27363 In what order should the four separate sections of elaboration code
27366 There are some restrictions in the order of elaboration that the binder
27367 can choose. In particular, if unit U has a @code{with}
27368 for a package @code{X}, then you
27369 are assured that the spec of @code{X}
27370 is elaborated before U , but you are
27371 not assured that the body of @code{X}
27372 is elaborated before U.
27373 This means that in the above case, the binder is allowed to choose the
27384 but that's not good, because now the call to @code{Math.Sqrt}
27385 that happens during
27386 the elaboration of the @code{Stuff}
27387 spec happens before the body of @code{Math.Sqrt} is
27388 elaborated, and hence causes @code{Program_Error} exception to be raised.
27389 At first glance, one might say that the binder is misbehaving, because
27390 obviously you want to elaborate the body of something you @code{with}
27392 that is not a general rule that can be followed in all cases. Consider
27394 @smallexample @c ada
27397 package X is @dots{}
27399 package Y is @dots{}
27402 package body Y is @dots{}
27405 package body X is @dots{}
27411 This is a common arrangement, and, apart from the order of elaboration
27412 problems that might arise in connection with elaboration code, this works fine.
27413 A rule that says that you must first elaborate the body of anything you
27414 @code{with} cannot work in this case:
27415 the body of @code{X} @code{with}'s @code{Y},
27416 which means you would have to
27417 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
27419 you have to elaborate the body of @code{X} first, but @dots{} and we have a
27420 loop that cannot be broken.
27422 It is true that the binder can in many cases guess an order of elaboration
27423 that is unlikely to cause a @code{Program_Error}
27424 exception to be raised, and it tries to do so (in the
27425 above example of @code{Math/Stuff/Spec}, the GNAT binder will
27427 elaborate the body of @code{Math} right after its spec, so all will be well).
27429 However, a program that blindly relies on the binder to be helpful can
27430 get into trouble, as we discussed in the previous sections, so
27432 provides a number of facilities for assisting the programmer in
27433 developing programs that are robust with respect to elaboration order.
27435 @node Default Behavior in GNAT - Ensuring Safety
27436 @section Default Behavior in GNAT - Ensuring Safety
27439 The default behavior in GNAT ensures elaboration safety. In its
27440 default mode GNAT implements the
27441 rule we previously described as the right approach. Let's restate it:
27445 @emph{If a unit has elaboration code that can directly or indirectly make a
27446 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
27447 package in a @code{with}'ed unit, then if the @code{with}'ed unit
27448 does not have pragma @code{Pure} or
27449 @code{Preelaborate}, then the client should have an
27450 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
27452 @emph{In the case of instantiating a generic subprogram, it is always
27453 sufficient to have only an @code{Elaborate} pragma for the
27454 @code{with}'ed unit.}
27458 By following this rule a client is assured that calls and instantiations
27459 can be made without risk of an exception.
27461 In this mode GNAT traces all calls that are potentially made from
27462 elaboration code, and puts in any missing implicit @code{Elaborate}
27463 and @code{Elaborate_All} pragmas.
27464 The advantage of this approach is that no elaboration problems
27465 are possible if the binder can find an elaboration order that is
27466 consistent with these implicit @code{Elaborate} and
27467 @code{Elaborate_All} pragmas. The
27468 disadvantage of this approach is that no such order may exist.
27470 If the binder does not generate any diagnostics, then it means that it has
27471 found an elaboration order that is guaranteed to be safe. However, the binder
27472 may still be relying on implicitly generated @code{Elaborate} and
27473 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
27476 If it is important to guarantee portability, then the compilations should
27479 (warn on elaboration problems) switch. This will cause warning messages
27480 to be generated indicating the missing @code{Elaborate} and
27481 @code{Elaborate_All} pragmas.
27482 Consider the following source program:
27484 @smallexample @c ada
27489 m : integer := k.r;
27496 where it is clear that there
27497 should be a pragma @code{Elaborate_All}
27498 for unit @code{k}. An implicit pragma will be generated, and it is
27499 likely that the binder will be able to honor it. However, if you want
27500 to port this program to some other Ada compiler than GNAT.
27501 it is safer to include the pragma explicitly in the source. If this
27502 unit is compiled with the
27504 switch, then the compiler outputs a warning:
27511 3. m : integer := k.r;
27513 >>> warning: call to "r" may raise Program_Error
27514 >>> warning: missing pragma Elaborate_All for "k"
27522 and these warnings can be used as a guide for supplying manually
27523 the missing pragmas. It is usually a bad idea to use this warning
27524 option during development. That's because it will warn you when
27525 you need to put in a pragma, but cannot warn you when it is time
27526 to take it out. So the use of pragma @code{Elaborate_All} may lead to
27527 unnecessary dependencies and even false circularities.
27529 This default mode is more restrictive than the Ada Reference
27530 Manual, and it is possible to construct programs which will compile
27531 using the dynamic model described there, but will run into a
27532 circularity using the safer static model we have described.
27534 Of course any Ada compiler must be able to operate in a mode
27535 consistent with the requirements of the Ada Reference Manual,
27536 and in particular must have the capability of implementing the
27537 standard dynamic model of elaboration with run-time checks.
27539 In GNAT, this standard mode can be achieved either by the use of
27540 the @option{-gnatE} switch on the compiler (@command{gcc} or
27541 @command{gnatmake}) command, or by the use of the configuration pragma:
27543 @smallexample @c ada
27544 pragma Elaboration_Checks (RM);
27548 Either approach will cause the unit affected to be compiled using the
27549 standard dynamic run-time elaboration checks described in the Ada
27550 Reference Manual. The static model is generally preferable, since it
27551 is clearly safer to rely on compile and link time checks rather than
27552 run-time checks. However, in the case of legacy code, it may be
27553 difficult to meet the requirements of the static model. This
27554 issue is further discussed in
27555 @ref{What to Do If the Default Elaboration Behavior Fails}.
27557 Note that the static model provides a strict subset of the allowed
27558 behavior and programs of the Ada Reference Manual, so if you do
27559 adhere to the static model and no circularities exist,
27560 then you are assured that your program will
27561 work using the dynamic model, providing that you remove any
27562 pragma Elaborate statements from the source.
27564 @node Treatment of Pragma Elaborate
27565 @section Treatment of Pragma Elaborate
27566 @cindex Pragma Elaborate
27569 The use of @code{pragma Elaborate}
27570 should generally be avoided in Ada 95 and Ada 2005 programs,
27571 since there is no guarantee that transitive calls
27572 will be properly handled. Indeed at one point, this pragma was placed
27573 in Annex J (Obsolescent Features), on the grounds that it is never useful.
27575 Now that's a bit restrictive. In practice, the case in which
27576 @code{pragma Elaborate} is useful is when the caller knows that there
27577 are no transitive calls, or that the called unit contains all necessary
27578 transitive @code{pragma Elaborate} statements, and legacy code often
27579 contains such uses.
27581 Strictly speaking the static mode in GNAT should ignore such pragmas,
27582 since there is no assurance at compile time that the necessary safety
27583 conditions are met. In practice, this would cause GNAT to be incompatible
27584 with correctly written Ada 83 code that had all necessary
27585 @code{pragma Elaborate} statements in place. Consequently, we made the
27586 decision that GNAT in its default mode will believe that if it encounters
27587 a @code{pragma Elaborate} then the programmer knows what they are doing,
27588 and it will trust that no elaboration errors can occur.
27590 The result of this decision is two-fold. First to be safe using the
27591 static mode, you should remove all @code{pragma Elaborate} statements.
27592 Second, when fixing circularities in existing code, you can selectively
27593 use @code{pragma Elaborate} statements to convince the static mode of
27594 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
27597 When using the static mode with @option{-gnatwl}, any use of
27598 @code{pragma Elaborate} will generate a warning about possible
27601 @node Elaboration Issues for Library Tasks
27602 @section Elaboration Issues for Library Tasks
27603 @cindex Library tasks, elaboration issues
27604 @cindex Elaboration of library tasks
27607 In this section we examine special elaboration issues that arise for
27608 programs that declare library level tasks.
27610 Generally the model of execution of an Ada program is that all units are
27611 elaborated, and then execution of the program starts. However, the
27612 declaration of library tasks definitely does not fit this model. The
27613 reason for this is that library tasks start as soon as they are declared
27614 (more precisely, as soon as the statement part of the enclosing package
27615 body is reached), that is to say before elaboration
27616 of the program is complete. This means that if such a task calls a
27617 subprogram, or an entry in another task, the callee may or may not be
27618 elaborated yet, and in the standard
27619 Reference Manual model of dynamic elaboration checks, you can even
27620 get timing dependent Program_Error exceptions, since there can be
27621 a race between the elaboration code and the task code.
27623 The static model of elaboration in GNAT seeks to avoid all such
27624 dynamic behavior, by being conservative, and the conservative
27625 approach in this particular case is to assume that all the code
27626 in a task body is potentially executed at elaboration time if
27627 a task is declared at the library level.
27629 This can definitely result in unexpected circularities. Consider
27630 the following example
27632 @smallexample @c ada
27638 type My_Int is new Integer;
27640 function Ident (M : My_Int) return My_Int;
27644 package body Decls is
27645 task body Lib_Task is
27651 function Ident (M : My_Int) return My_Int is
27659 procedure Put_Val (Arg : Decls.My_Int);
27663 package body Utils is
27664 procedure Put_Val (Arg : Decls.My_Int) is
27666 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
27673 Decls.Lib_Task.Start;
27678 If the above example is compiled in the default static elaboration
27679 mode, then a circularity occurs. The circularity comes from the call
27680 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
27681 this call occurs in elaboration code, we need an implicit pragma
27682 @code{Elaborate_All} for @code{Utils}. This means that not only must
27683 the spec and body of @code{Utils} be elaborated before the body
27684 of @code{Decls}, but also the spec and body of any unit that is
27685 @code{with'ed} by the body of @code{Utils} must also be elaborated before
27686 the body of @code{Decls}. This is the transitive implication of
27687 pragma @code{Elaborate_All} and it makes sense, because in general
27688 the body of @code{Put_Val} might have a call to something in a
27689 @code{with'ed} unit.
27691 In this case, the body of Utils (actually its spec) @code{with's}
27692 @code{Decls}. Unfortunately this means that the body of @code{Decls}
27693 must be elaborated before itself, in case there is a call from the
27694 body of @code{Utils}.
27696 Here is the exact chain of events we are worrying about:
27700 In the body of @code{Decls} a call is made from within the body of a library
27701 task to a subprogram in the package @code{Utils}. Since this call may
27702 occur at elaboration time (given that the task is activated at elaboration
27703 time), we have to assume the worst, i.e., that the
27704 call does happen at elaboration time.
27707 This means that the body and spec of @code{Util} must be elaborated before
27708 the body of @code{Decls} so that this call does not cause an access before
27712 Within the body of @code{Util}, specifically within the body of
27713 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
27717 One such @code{with}'ed package is package @code{Decls}, so there
27718 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
27719 In fact there is such a call in this example, but we would have to
27720 assume that there was such a call even if it were not there, since
27721 we are not supposed to write the body of @code{Decls} knowing what
27722 is in the body of @code{Utils}; certainly in the case of the
27723 static elaboration model, the compiler does not know what is in
27724 other bodies and must assume the worst.
27727 This means that the spec and body of @code{Decls} must also be
27728 elaborated before we elaborate the unit containing the call, but
27729 that unit is @code{Decls}! This means that the body of @code{Decls}
27730 must be elaborated before itself, and that's a circularity.
27734 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
27735 the body of @code{Decls} you will get a true Ada Reference Manual
27736 circularity that makes the program illegal.
27738 In practice, we have found that problems with the static model of
27739 elaboration in existing code often arise from library tasks, so
27740 we must address this particular situation.
27742 Note that if we compile and run the program above, using the dynamic model of
27743 elaboration (that is to say use the @option{-gnatE} switch),
27744 then it compiles, binds,
27745 links, and runs, printing the expected result of 2. Therefore in some sense
27746 the circularity here is only apparent, and we need to capture
27747 the properties of this program that distinguish it from other library-level
27748 tasks that have real elaboration problems.
27750 We have four possible answers to this question:
27755 Use the dynamic model of elaboration.
27757 If we use the @option{-gnatE} switch, then as noted above, the program works.
27758 Why is this? If we examine the task body, it is apparent that the task cannot
27760 @code{accept} statement until after elaboration has been completed, because
27761 the corresponding entry call comes from the main program, not earlier.
27762 This is why the dynamic model works here. But that's really giving
27763 up on a precise analysis, and we prefer to take this approach only if we cannot
27765 problem in any other manner. So let us examine two ways to reorganize
27766 the program to avoid the potential elaboration problem.
27769 Split library tasks into separate packages.
27771 Write separate packages, so that library tasks are isolated from
27772 other declarations as much as possible. Let us look at a variation on
27775 @smallexample @c ada
27783 package body Decls1 is
27784 task body Lib_Task is
27792 type My_Int is new Integer;
27793 function Ident (M : My_Int) return My_Int;
27797 package body Decls2 is
27798 function Ident (M : My_Int) return My_Int is
27806 procedure Put_Val (Arg : Decls2.My_Int);
27810 package body Utils is
27811 procedure Put_Val (Arg : Decls2.My_Int) is
27813 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
27820 Decls1.Lib_Task.Start;
27825 All we have done is to split @code{Decls} into two packages, one
27826 containing the library task, and one containing everything else. Now
27827 there is no cycle, and the program compiles, binds, links and executes
27828 using the default static model of elaboration.
27831 Declare separate task types.
27833 A significant part of the problem arises because of the use of the
27834 single task declaration form. This means that the elaboration of
27835 the task type, and the elaboration of the task itself (i.e.@: the
27836 creation of the task) happen at the same time. A good rule
27837 of style in Ada is to always create explicit task types. By
27838 following the additional step of placing task objects in separate
27839 packages from the task type declaration, many elaboration problems
27840 are avoided. Here is another modified example of the example program:
27842 @smallexample @c ada
27844 task type Lib_Task_Type is
27848 type My_Int is new Integer;
27850 function Ident (M : My_Int) return My_Int;
27854 package body Decls is
27855 task body Lib_Task_Type is
27861 function Ident (M : My_Int) return My_Int is
27869 procedure Put_Val (Arg : Decls.My_Int);
27873 package body Utils is
27874 procedure Put_Val (Arg : Decls.My_Int) is
27876 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
27882 Lib_Task : Decls.Lib_Task_Type;
27888 Declst.Lib_Task.Start;
27893 What we have done here is to replace the @code{task} declaration in
27894 package @code{Decls} with a @code{task type} declaration. Then we
27895 introduce a separate package @code{Declst} to contain the actual
27896 task object. This separates the elaboration issues for
27897 the @code{task type}
27898 declaration, which causes no trouble, from the elaboration issues
27899 of the task object, which is also unproblematic, since it is now independent
27900 of the elaboration of @code{Utils}.
27901 This separation of concerns also corresponds to
27902 a generally sound engineering principle of separating declarations
27903 from instances. This version of the program also compiles, binds, links,
27904 and executes, generating the expected output.
27907 Use No_Entry_Calls_In_Elaboration_Code restriction.
27908 @cindex No_Entry_Calls_In_Elaboration_Code
27910 The previous two approaches described how a program can be restructured
27911 to avoid the special problems caused by library task bodies. in practice,
27912 however, such restructuring may be difficult to apply to existing legacy code,
27913 so we must consider solutions that do not require massive rewriting.
27915 Let us consider more carefully why our original sample program works
27916 under the dynamic model of elaboration. The reason is that the code
27917 in the task body blocks immediately on the @code{accept}
27918 statement. Now of course there is nothing to prohibit elaboration
27919 code from making entry calls (for example from another library level task),
27920 so we cannot tell in isolation that
27921 the task will not execute the accept statement during elaboration.
27923 However, in practice it is very unusual to see elaboration code
27924 make any entry calls, and the pattern of tasks starting
27925 at elaboration time and then immediately blocking on @code{accept} or
27926 @code{select} statements is very common. What this means is that
27927 the compiler is being too pessimistic when it analyzes the
27928 whole package body as though it might be executed at elaboration
27931 If we know that the elaboration code contains no entry calls, (a very safe
27932 assumption most of the time, that could almost be made the default
27933 behavior), then we can compile all units of the program under control
27934 of the following configuration pragma:
27937 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
27941 This pragma can be placed in the @file{gnat.adc} file in the usual
27942 manner. If we take our original unmodified program and compile it
27943 in the presence of a @file{gnat.adc} containing the above pragma,
27944 then once again, we can compile, bind, link, and execute, obtaining
27945 the expected result. In the presence of this pragma, the compiler does
27946 not trace calls in a task body, that appear after the first @code{accept}
27947 or @code{select} statement, and therefore does not report a potential
27948 circularity in the original program.
27950 The compiler will check to the extent it can that the above
27951 restriction is not violated, but it is not always possible to do a
27952 complete check at compile time, so it is important to use this
27953 pragma only if the stated restriction is in fact met, that is to say
27954 no task receives an entry call before elaboration of all units is completed.
27958 @node Mixing Elaboration Models
27959 @section Mixing Elaboration Models
27961 So far, we have assumed that the entire program is either compiled
27962 using the dynamic model or static model, ensuring consistency. It
27963 is possible to mix the two models, but rules have to be followed
27964 if this mixing is done to ensure that elaboration checks are not
27967 The basic rule is that @emph{a unit compiled with the static model cannot
27968 be @code{with'ed} by a unit compiled with the dynamic model}. The
27969 reason for this is that in the static model, a unit assumes that
27970 its clients guarantee to use (the equivalent of) pragma
27971 @code{Elaborate_All} so that no elaboration checks are required
27972 in inner subprograms, and this assumption is violated if the
27973 client is compiled with dynamic checks.
27975 The precise rule is as follows. A unit that is compiled with dynamic
27976 checks can only @code{with} a unit that meets at least one of the
27977 following criteria:
27982 The @code{with'ed} unit is itself compiled with dynamic elaboration
27983 checks (that is with the @option{-gnatE} switch.
27986 The @code{with'ed} unit is an internal GNAT implementation unit from
27987 the System, Interfaces, Ada, or GNAT hierarchies.
27990 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
27993 The @code{with'ing} unit (that is the client) has an explicit pragma
27994 @code{Elaborate_All} for the @code{with'ed} unit.
27999 If this rule is violated, that is if a unit with dynamic elaboration
28000 checks @code{with's} a unit that does not meet one of the above four
28001 criteria, then the binder (@code{gnatbind}) will issue a warning
28002 similar to that in the following example:
28005 warning: "x.ads" has dynamic elaboration checks and with's
28006 warning: "y.ads" which has static elaboration checks
28010 These warnings indicate that the rule has been violated, and that as a result
28011 elaboration checks may be missed in the resulting executable file.
28012 This warning may be suppressed using the @option{-ws} binder switch
28013 in the usual manner.
28015 One useful application of this mixing rule is in the case of a subsystem
28016 which does not itself @code{with} units from the remainder of the
28017 application. In this case, the entire subsystem can be compiled with
28018 dynamic checks to resolve a circularity in the subsystem, while
28019 allowing the main application that uses this subsystem to be compiled
28020 using the more reliable default static model.
28022 @node What to Do If the Default Elaboration Behavior Fails
28023 @section What to Do If the Default Elaboration Behavior Fails
28026 If the binder cannot find an acceptable order, it outputs detailed
28027 diagnostics. For example:
28033 error: elaboration circularity detected
28034 info: "proc (body)" must be elaborated before "pack (body)"
28035 info: reason: Elaborate_All probably needed in unit "pack (body)"
28036 info: recompile "pack (body)" with -gnatwl
28037 info: for full details
28038 info: "proc (body)"
28039 info: is needed by its spec:
28040 info: "proc (spec)"
28041 info: which is withed by:
28042 info: "pack (body)"
28043 info: "pack (body)" must be elaborated before "proc (body)"
28044 info: reason: pragma Elaborate in unit "proc (body)"
28050 In this case we have a cycle that the binder cannot break. On the one
28051 hand, there is an explicit pragma Elaborate in @code{proc} for
28052 @code{pack}. This means that the body of @code{pack} must be elaborated
28053 before the body of @code{proc}. On the other hand, there is elaboration
28054 code in @code{pack} that calls a subprogram in @code{proc}. This means
28055 that for maximum safety, there should really be a pragma
28056 Elaborate_All in @code{pack} for @code{proc} which would require that
28057 the body of @code{proc} be elaborated before the body of
28058 @code{pack}. Clearly both requirements cannot be satisfied.
28059 Faced with a circularity of this kind, you have three different options.
28062 @item Fix the program
28063 The most desirable option from the point of view of long-term maintenance
28064 is to rearrange the program so that the elaboration problems are avoided.
28065 One useful technique is to place the elaboration code into separate
28066 child packages. Another is to move some of the initialization code to
28067 explicitly called subprograms, where the program controls the order
28068 of initialization explicitly. Although this is the most desirable option,
28069 it may be impractical and involve too much modification, especially in
28070 the case of complex legacy code.
28072 @item Perform dynamic checks
28073 If the compilations are done using the
28075 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28076 manner. Dynamic checks are generated for all calls that could possibly result
28077 in raising an exception. With this switch, the compiler does not generate
28078 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28079 exactly as specified in the @cite{Ada Reference Manual}.
28080 The binder will generate
28081 an executable program that may or may not raise @code{Program_Error}, and then
28082 it is the programmer's job to ensure that it does not raise an exception. Note
28083 that it is important to compile all units with the switch, it cannot be used
28086 @item Suppress checks
28087 The drawback of dynamic checks is that they generate a
28088 significant overhead at run time, both in space and time. If you
28089 are absolutely sure that your program cannot raise any elaboration
28090 exceptions, and you still want to use the dynamic elaboration model,
28091 then you can use the configuration pragma
28092 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28093 example this pragma could be placed in the @file{gnat.adc} file.
28095 @item Suppress checks selectively
28096 When you know that certain calls or instantiations in elaboration code cannot
28097 possibly lead to an elaboration error, and the binder nevertheless complains
28098 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28099 elaboration circularities, it is possible to remove those warnings locally and
28100 obtain a program that will bind. Clearly this can be unsafe, and it is the
28101 responsibility of the programmer to make sure that the resulting program has no
28102 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28103 used with different granularity to suppress warnings and break elaboration
28108 Place the pragma that names the called subprogram in the declarative part
28109 that contains the call.
28112 Place the pragma in the declarative part, without naming an entity. This
28113 disables warnings on all calls in the corresponding declarative region.
28116 Place the pragma in the package spec that declares the called subprogram,
28117 and name the subprogram. This disables warnings on all elaboration calls to
28121 Place the pragma in the package spec that declares the called subprogram,
28122 without naming any entity. This disables warnings on all elaboration calls to
28123 all subprograms declared in this spec.
28125 @item Use Pragma Elaborate
28126 As previously described in section @xref{Treatment of Pragma Elaborate},
28127 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28128 that no elaboration checks are required on calls to the designated unit.
28129 There may be cases in which the caller knows that no transitive calls
28130 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28131 case where @code{pragma Elaborate_All} would cause a circularity.
28135 These five cases are listed in order of decreasing safety, and therefore
28136 require increasing programmer care in their application. Consider the
28139 @smallexample @c adanocomment
28141 function F1 return Integer;
28146 function F2 return Integer;
28147 function Pure (x : integer) return integer;
28148 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28149 -- pragma Suppress (Elaboration_Check); -- (4)
28153 package body Pack1 is
28154 function F1 return Integer is
28158 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28161 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28162 -- pragma Suppress(Elaboration_Check); -- (2)
28164 X1 := Pack2.F2 + 1; -- Elab. call (2)
28169 package body Pack2 is
28170 function F2 return Integer is
28174 function Pure (x : integer) return integer is
28176 return x ** 3 - 3 * x;
28180 with Pack1, Ada.Text_IO;
28183 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28186 In the absence of any pragmas, an attempt to bind this program produces
28187 the following diagnostics:
28193 error: elaboration circularity detected
28194 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28195 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28196 info: recompile "pack1 (body)" with -gnatwl for full details
28197 info: "pack1 (body)"
28198 info: must be elaborated along with its spec:
28199 info: "pack1 (spec)"
28200 info: which is withed by:
28201 info: "pack2 (body)"
28202 info: which must be elaborated along with its spec:
28203 info: "pack2 (spec)"
28204 info: which is withed by:
28205 info: "pack1 (body)"
28208 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28209 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28210 F2 is safe, even though F2 calls F1, because the call appears after the
28211 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28212 remove the warning on the call. It is also possible to use pragma (2)
28213 because there are no other potentially unsafe calls in the block.
28216 The call to @code{Pure} is safe because this function does not depend on the
28217 state of @code{Pack2}. Therefore any call to this function is safe, and it
28218 is correct to place pragma (3) in the corresponding package spec.
28221 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28222 warnings on all calls to functions declared therein. Note that this is not
28223 necessarily safe, and requires more detailed examination of the subprogram
28224 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28225 be already elaborated.
28229 It is hard to generalize on which of these four approaches should be
28230 taken. Obviously if it is possible to fix the program so that the default
28231 treatment works, this is preferable, but this may not always be practical.
28232 It is certainly simple enough to use
28234 but the danger in this case is that, even if the GNAT binder
28235 finds a correct elaboration order, it may not always do so,
28236 and certainly a binder from another Ada compiler might not. A
28237 combination of testing and analysis (for which the warnings generated
28240 switch can be useful) must be used to ensure that the program is free
28241 of errors. One switch that is useful in this testing is the
28242 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
28245 Normally the binder tries to find an order that has the best chance
28246 of avoiding elaboration problems. However, if this switch is used, the binder
28247 plays a devil's advocate role, and tries to choose the order that
28248 has the best chance of failing. If your program works even with this
28249 switch, then it has a better chance of being error free, but this is still
28252 For an example of this approach in action, consider the C-tests (executable
28253 tests) from the ACVC suite. If these are compiled and run with the default
28254 treatment, then all but one of them succeed without generating any error
28255 diagnostics from the binder. However, there is one test that fails, and
28256 this is not surprising, because the whole point of this test is to ensure
28257 that the compiler can handle cases where it is impossible to determine
28258 a correct order statically, and it checks that an exception is indeed
28259 raised at run time.
28261 This one test must be compiled and run using the
28263 switch, and then it passes. Alternatively, the entire suite can
28264 be run using this switch. It is never wrong to run with the dynamic
28265 elaboration switch if your code is correct, and we assume that the
28266 C-tests are indeed correct (it is less efficient, but efficiency is
28267 not a factor in running the ACVC tests.)
28269 @node Elaboration for Access-to-Subprogram Values
28270 @section Elaboration for Access-to-Subprogram Values
28271 @cindex Access-to-subprogram
28274 Access-to-subprogram types (introduced in Ada 95) complicate
28275 the handling of elaboration. The trouble is that it becomes
28276 impossible to tell at compile time which procedure
28277 is being called. This means that it is not possible for the binder
28278 to analyze the elaboration requirements in this case.
28280 If at the point at which the access value is created
28281 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
28282 the body of the subprogram is
28283 known to have been elaborated, then the access value is safe, and its use
28284 does not require a check. This may be achieved by appropriate arrangement
28285 of the order of declarations if the subprogram is in the current unit,
28286 or, if the subprogram is in another unit, by using pragma
28287 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
28288 on the referenced unit.
28290 If the referenced body is not known to have been elaborated at the point
28291 the access value is created, then any use of the access value must do a
28292 dynamic check, and this dynamic check will fail and raise a
28293 @code{Program_Error} exception if the body has not been elaborated yet.
28294 GNAT will generate the necessary checks, and in addition, if the
28296 switch is set, will generate warnings that such checks are required.
28298 The use of dynamic dispatching for tagged types similarly generates
28299 a requirement for dynamic checks, and premature calls to any primitive
28300 operation of a tagged type before the body of the operation has been
28301 elaborated, will result in the raising of @code{Program_Error}.
28303 @node Summary of Procedures for Elaboration Control
28304 @section Summary of Procedures for Elaboration Control
28305 @cindex Elaboration control
28308 First, compile your program with the default options, using none of
28309 the special elaboration control switches. If the binder successfully
28310 binds your program, then you can be confident that, apart from issues
28311 raised by the use of access-to-subprogram types and dynamic dispatching,
28312 the program is free of elaboration errors. If it is important that the
28313 program be portable, then use the
28315 switch to generate warnings about missing @code{Elaborate} or
28316 @code{Elaborate_All} pragmas, and supply the missing pragmas.
28318 If the program fails to bind using the default static elaboration
28319 handling, then you can fix the program to eliminate the binder
28320 message, or recompile the entire program with the
28321 @option{-gnatE} switch to generate dynamic elaboration checks,
28322 and, if you are sure there really are no elaboration problems,
28323 use a global pragma @code{Suppress (Elaboration_Check)}.
28325 @node Other Elaboration Order Considerations
28326 @section Other Elaboration Order Considerations
28328 This section has been entirely concerned with the issue of finding a valid
28329 elaboration order, as defined by the Ada Reference Manual. In a case
28330 where several elaboration orders are valid, the task is to find one
28331 of the possible valid elaboration orders (and the static model in GNAT
28332 will ensure that this is achieved).
28334 The purpose of the elaboration rules in the Ada Reference Manual is to
28335 make sure that no entity is accessed before it has been elaborated. For
28336 a subprogram, this means that the spec and body must have been elaborated
28337 before the subprogram is called. For an object, this means that the object
28338 must have been elaborated before its value is read or written. A violation
28339 of either of these two requirements is an access before elaboration order,
28340 and this section has been all about avoiding such errors.
28342 In the case where more than one order of elaboration is possible, in the
28343 sense that access before elaboration errors are avoided, then any one of
28344 the orders is ``correct'' in the sense that it meets the requirements of
28345 the Ada Reference Manual, and no such error occurs.
28347 However, it may be the case for a given program, that there are
28348 constraints on the order of elaboration that come not from consideration
28349 of avoiding elaboration errors, but rather from extra-lingual logic
28350 requirements. Consider this example:
28352 @smallexample @c ada
28353 with Init_Constants;
28354 package Constants is
28359 package Init_Constants is
28360 procedure P; -- require a body
28361 end Init_Constants;
28364 package body Init_Constants is
28365 procedure P is begin null; end;
28369 end Init_Constants;
28373 Z : Integer := Constants.X + Constants.Y;
28377 with Text_IO; use Text_IO;
28380 Put_Line (Calc.Z'Img);
28385 In this example, there is more than one valid order of elaboration. For
28386 example both the following are correct orders:
28389 Init_Constants spec
28392 Init_Constants body
28397 Init_Constants spec
28398 Init_Constants body
28405 There is no language rule to prefer one or the other, both are correct
28406 from an order of elaboration point of view. But the programmatic effects
28407 of the two orders are very different. In the first, the elaboration routine
28408 of @code{Calc} initializes @code{Z} to zero, and then the main program
28409 runs with this value of zero. But in the second order, the elaboration
28410 routine of @code{Calc} runs after the body of Init_Constants has set
28411 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
28414 One could perhaps by applying pretty clever non-artificial intelligence
28415 to the situation guess that it is more likely that the second order of
28416 elaboration is the one desired, but there is no formal linguistic reason
28417 to prefer one over the other. In fact in this particular case, GNAT will
28418 prefer the second order, because of the rule that bodies are elaborated
28419 as soon as possible, but it's just luck that this is what was wanted
28420 (if indeed the second order was preferred).
28422 If the program cares about the order of elaboration routines in a case like
28423 this, it is important to specify the order required. In this particular
28424 case, that could have been achieved by adding to the spec of Calc:
28426 @smallexample @c ada
28427 pragma Elaborate_All (Constants);
28431 which requires that the body (if any) and spec of @code{Constants},
28432 as well as the body and spec of any unit @code{with}'ed by
28433 @code{Constants} be elaborated before @code{Calc} is elaborated.
28435 Clearly no automatic method can always guess which alternative you require,
28436 and if you are working with legacy code that had constraints of this kind
28437 which were not properly specified by adding @code{Elaborate} or
28438 @code{Elaborate_All} pragmas, then indeed it is possible that two different
28439 compilers can choose different orders.
28441 However, GNAT does attempt to diagnose the common situation where there
28442 are uninitialized variables in the visible part of a package spec, and the
28443 corresponding package body has an elaboration block that directly or
28444 indirectly initialized one or more of these variables. This is the situation
28445 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
28446 a warning that suggests this addition if it detects this situation.
28448 The @code{gnatbind}
28449 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
28450 out problems. This switch causes bodies to be elaborated as late as possible
28451 instead of as early as possible. In the example above, it would have forced
28452 the choice of the first elaboration order. If you get different results
28453 when using this switch, and particularly if one set of results is right,
28454 and one is wrong as far as you are concerned, it shows that you have some
28455 missing @code{Elaborate} pragmas. For the example above, we have the
28459 gnatmake -f -q main
28462 gnatmake -f -q main -bargs -p
28468 It is of course quite unlikely that both these results are correct, so
28469 it is up to you in a case like this to investigate the source of the
28470 difference, by looking at the two elaboration orders that are chosen,
28471 and figuring out which is correct, and then adding the necessary
28472 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
28476 @c *******************************
28477 @node Conditional Compilation
28478 @appendix Conditional Compilation
28479 @c *******************************
28480 @cindex Conditional compilation
28483 It is often necessary to arrange for a single source program
28484 to serve multiple purposes, where it is compiled in different
28485 ways to achieve these different goals. Some examples of the
28486 need for this feature are
28489 @item Adapting a program to a different hardware environment
28490 @item Adapting a program to a different target architecture
28491 @item Turning debugging features on and off
28492 @item Arranging for a program to compile with different compilers
28496 In C, or C++, the typical approach would be to use the preprocessor
28497 that is defined as part of the language. The Ada language does not
28498 contain such a feature. This is not an oversight, but rather a very
28499 deliberate design decision, based on the experience that overuse of
28500 the preprocessing features in C and C++ can result in programs that
28501 are extremely difficult to maintain. For example, if we have ten
28502 switches that can be on or off, this means that there are a thousand
28503 separate programs, any one of which might not even be syntactically
28504 correct, and even if syntactically correct, the resulting program
28505 might not work correctly. Testing all combinations can quickly become
28508 Nevertheless, the need to tailor programs certainly exists, and in
28509 this Appendix we will discuss how this can
28510 be achieved using Ada in general, and GNAT in particular.
28513 * Use of Boolean Constants::
28514 * Debugging - A Special Case::
28515 * Conditionalizing Declarations::
28516 * Use of Alternative Implementations::
28520 @node Use of Boolean Constants
28521 @section Use of Boolean Constants
28524 In the case where the difference is simply which code
28525 sequence is executed, the cleanest solution is to use Boolean
28526 constants to control which code is executed.
28528 @smallexample @c ada
28530 FP_Initialize_Required : constant Boolean := True;
28532 if FP_Initialize_Required then
28539 Not only will the code inside the @code{if} statement not be executed if
28540 the constant Boolean is @code{False}, but it will also be completely
28541 deleted from the program.
28542 However, the code is only deleted after the @code{if} statement
28543 has been checked for syntactic and semantic correctness.
28544 (In contrast, with preprocessors the code is deleted before the
28545 compiler ever gets to see it, so it is not checked until the switch
28547 @cindex Preprocessors (contrasted with conditional compilation)
28549 Typically the Boolean constants will be in a separate package,
28552 @smallexample @c ada
28555 FP_Initialize_Required : constant Boolean := True;
28556 Reset_Available : constant Boolean := False;
28563 The @code{Config} package exists in multiple forms for the various targets,
28564 with an appropriate script selecting the version of @code{Config} needed.
28565 Then any other unit requiring conditional compilation can do a @code{with}
28566 of @code{Config} to make the constants visible.
28569 @node Debugging - A Special Case
28570 @section Debugging - A Special Case
28573 A common use of conditional code is to execute statements (for example
28574 dynamic checks, or output of intermediate results) under control of a
28575 debug switch, so that the debugging behavior can be turned on and off.
28576 This can be done using a Boolean constant to control whether the code
28579 @smallexample @c ada
28582 Put_Line ("got to the first stage!");
28590 @smallexample @c ada
28592 if Debugging and then Temperature > 999.0 then
28593 raise Temperature_Crazy;
28599 Since this is a common case, there are special features to deal with
28600 this in a convenient manner. For the case of tests, Ada 2005 has added
28601 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
28602 @cindex pragma @code{Assert}
28603 on the @code{Assert} pragma that has always been available in GNAT, so this
28604 feature may be used with GNAT even if you are not using Ada 2005 features.
28605 The use of pragma @code{Assert} is described in
28606 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
28607 example, the last test could be written:
28609 @smallexample @c ada
28610 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
28616 @smallexample @c ada
28617 pragma Assert (Temperature <= 999.0);
28621 In both cases, if assertions are active and the temperature is excessive,
28622 the exception @code{Assert_Failure} will be raised, with the given string in
28623 the first case or a string indicating the location of the pragma in the second
28624 case used as the exception message.
28626 You can turn assertions on and off by using the @code{Assertion_Policy}
28628 @cindex pragma @code{Assertion_Policy}
28629 This is an Ada 2005 pragma which is implemented in all modes by
28630 GNAT, but only in the latest versions of GNAT which include Ada 2005
28631 capability. Alternatively, you can use the @option{-gnata} switch
28632 @cindex @option{-gnata} switch
28633 to enable assertions from the command line (this is recognized by all versions
28636 For the example above with the @code{Put_Line}, the GNAT-specific pragma
28637 @code{Debug} can be used:
28638 @cindex pragma @code{Debug}
28640 @smallexample @c ada
28641 pragma Debug (Put_Line ("got to the first stage!"));
28645 If debug pragmas are enabled, the argument, which must be of the form of
28646 a procedure call, is executed (in this case, @code{Put_Line} will be called).
28647 Only one call can be present, but of course a special debugging procedure
28648 containing any code you like can be included in the program and then
28649 called in a pragma @code{Debug} argument as needed.
28651 One advantage of pragma @code{Debug} over the @code{if Debugging then}
28652 construct is that pragma @code{Debug} can appear in declarative contexts,
28653 such as at the very beginning of a procedure, before local declarations have
28656 Debug pragmas are enabled using either the @option{-gnata} switch that also
28657 controls assertions, or with a separate Debug_Policy pragma.
28658 @cindex pragma @code{Debug_Policy}
28659 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
28660 in Ada 95 and Ada 83 programs as well), and is analogous to
28661 pragma @code{Assertion_Policy} to control assertions.
28663 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
28664 and thus they can appear in @file{gnat.adc} if you are not using a
28665 project file, or in the file designated to contain configuration pragmas
28667 They then apply to all subsequent compilations. In practice the use of
28668 the @option{-gnata} switch is often the most convenient method of controlling
28669 the status of these pragmas.
28671 Note that a pragma is not a statement, so in contexts where a statement
28672 sequence is required, you can't just write a pragma on its own. You have
28673 to add a @code{null} statement.
28675 @smallexample @c ada
28678 @dots{} -- some statements
28680 pragma Assert (Num_Cases < 10);
28687 @node Conditionalizing Declarations
28688 @section Conditionalizing Declarations
28691 In some cases, it may be necessary to conditionalize declarations to meet
28692 different requirements. For example we might want a bit string whose length
28693 is set to meet some hardware message requirement.
28695 In some cases, it may be possible to do this using declare blocks controlled
28696 by conditional constants:
28698 @smallexample @c ada
28700 if Small_Machine then
28702 X : Bit_String (1 .. 10);
28708 X : Large_Bit_String (1 .. 1000);
28717 Note that in this approach, both declarations are analyzed by the
28718 compiler so this can only be used where both declarations are legal,
28719 even though one of them will not be used.
28721 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
28722 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
28723 that are parameterized by these constants. For example
28725 @smallexample @c ada
28728 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
28734 If @code{Bits_Per_Word} is set to 32, this generates either
28736 @smallexample @c ada
28739 Field1 at 0 range 0 .. 32;
28745 for the big endian case, or
28747 @smallexample @c ada
28750 Field1 at 0 range 10 .. 32;
28756 for the little endian case. Since a powerful subset of Ada expression
28757 notation is usable for creating static constants, clever use of this
28758 feature can often solve quite difficult problems in conditionalizing
28759 compilation (note incidentally that in Ada 95, the little endian
28760 constant was introduced as @code{System.Default_Bit_Order}, so you do not
28761 need to define this one yourself).
28764 @node Use of Alternative Implementations
28765 @section Use of Alternative Implementations
28768 In some cases, none of the approaches described above are adequate. This
28769 can occur for example if the set of declarations required is radically
28770 different for two different configurations.
28772 In this situation, the official Ada way of dealing with conditionalizing
28773 such code is to write separate units for the different cases. As long as
28774 this does not result in excessive duplication of code, this can be done
28775 without creating maintenance problems. The approach is to share common
28776 code as far as possible, and then isolate the code and declarations
28777 that are different. Subunits are often a convenient method for breaking
28778 out a piece of a unit that is to be conditionalized, with separate files
28779 for different versions of the subunit for different targets, where the
28780 build script selects the right one to give to the compiler.
28781 @cindex Subunits (and conditional compilation)
28783 As an example, consider a situation where a new feature in Ada 2005
28784 allows something to be done in a really nice way. But your code must be able
28785 to compile with an Ada 95 compiler. Conceptually you want to say:
28787 @smallexample @c ada
28790 @dots{} neat Ada 2005 code
28792 @dots{} not quite as neat Ada 95 code
28798 where @code{Ada_2005} is a Boolean constant.
28800 But this won't work when @code{Ada_2005} is set to @code{False},
28801 since the @code{then} clause will be illegal for an Ada 95 compiler.
28802 (Recall that although such unreachable code would eventually be deleted
28803 by the compiler, it still needs to be legal. If it uses features
28804 introduced in Ada 2005, it will be illegal in Ada 95.)
28806 So instead we write
28808 @smallexample @c ada
28809 procedure Insert is separate;
28813 Then we have two files for the subunit @code{Insert}, with the two sets of
28815 If the package containing this is called @code{File_Queries}, then we might
28819 @item @file{file_queries-insert-2005.adb}
28820 @item @file{file_queries-insert-95.adb}
28824 and the build script renames the appropriate file to
28827 file_queries-insert.adb
28831 and then carries out the compilation.
28833 This can also be done with project files' naming schemes. For example:
28835 @smallexample @c project
28836 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
28840 Note also that with project files it is desirable to use a different extension
28841 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
28842 conflict may arise through another commonly used feature: to declare as part
28843 of the project a set of directories containing all the sources obeying the
28844 default naming scheme.
28846 The use of alternative units is certainly feasible in all situations,
28847 and for example the Ada part of the GNAT run-time is conditionalized
28848 based on the target architecture using this approach. As a specific example,
28849 consider the implementation of the AST feature in VMS. There is one
28857 which is the same for all architectures, and three bodies:
28861 used for all non-VMS operating systems
28862 @item s-asthan-vms-alpha.adb
28863 used for VMS on the Alpha
28864 @item s-asthan-vms-ia64.adb
28865 used for VMS on the ia64
28869 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
28870 this operating system feature is not available, and the two remaining
28871 versions interface with the corresponding versions of VMS to provide
28872 VMS-compatible AST handling. The GNAT build script knows the architecture
28873 and operating system, and automatically selects the right version,
28874 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
28876 Another style for arranging alternative implementations is through Ada's
28877 access-to-subprogram facility.
28878 In case some functionality is to be conditionally included,
28879 you can declare an access-to-procedure variable @code{Ref} that is initialized
28880 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
28882 In some library package, set @code{Ref} to @code{Proc'Access} for some
28883 procedure @code{Proc} that performs the relevant processing.
28884 The initialization only occurs if the library package is included in the
28886 The same idea can also be implemented using tagged types and dispatching
28890 @node Preprocessing
28891 @section Preprocessing
28892 @cindex Preprocessing
28895 Although it is quite possible to conditionalize code without the use of
28896 C-style preprocessing, as described earlier in this section, it is
28897 nevertheless convenient in some cases to use the C approach. Moreover,
28898 older Ada compilers have often provided some preprocessing capability,
28899 so legacy code may depend on this approach, even though it is not
28902 To accommodate such use, GNAT provides a preprocessor (modeled to a large
28903 extent on the various preprocessors that have been used
28904 with legacy code on other compilers, to enable easier transition).
28906 The preprocessor may be used in two separate modes. It can be used quite
28907 separately from the compiler, to generate a separate output source file
28908 that is then fed to the compiler as a separate step. This is the
28909 @code{gnatprep} utility, whose use is fully described in
28910 @ref{Preprocessing Using gnatprep}.
28911 @cindex @code{gnatprep}
28913 The preprocessing language allows such constructs as
28917 #if DEBUG or PRIORITY > 4 then
28918 bunch of declarations
28920 completely different bunch of declarations
28926 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
28927 defined either on the command line or in a separate file.
28929 The other way of running the preprocessor is even closer to the C style and
28930 often more convenient. In this approach the preprocessing is integrated into
28931 the compilation process. The compiler is fed the preprocessor input which
28932 includes @code{#if} lines etc, and then the compiler carries out the
28933 preprocessing internally and processes the resulting output.
28934 For more details on this approach, see @ref{Integrated Preprocessing}.
28937 @c *******************************
28938 @node Inline Assembler
28939 @appendix Inline Assembler
28940 @c *******************************
28943 If you need to write low-level software that interacts directly
28944 with the hardware, Ada provides two ways to incorporate assembly
28945 language code into your program. First, you can import and invoke
28946 external routines written in assembly language, an Ada feature fully
28947 supported by GNAT@. However, for small sections of code it may be simpler
28948 or more efficient to include assembly language statements directly
28949 in your Ada source program, using the facilities of the implementation-defined
28950 package @code{System.Machine_Code}, which incorporates the gcc
28951 Inline Assembler. The Inline Assembler approach offers a number of advantages,
28952 including the following:
28955 @item No need to use non-Ada tools
28956 @item Consistent interface over different targets
28957 @item Automatic usage of the proper calling conventions
28958 @item Access to Ada constants and variables
28959 @item Definition of intrinsic routines
28960 @item Possibility of inlining a subprogram comprising assembler code
28961 @item Code optimizer can take Inline Assembler code into account
28964 This chapter presents a series of examples to show you how to use
28965 the Inline Assembler. Although it focuses on the Intel x86,
28966 the general approach applies also to other processors.
28967 It is assumed that you are familiar with Ada
28968 and with assembly language programming.
28971 * Basic Assembler Syntax::
28972 * A Simple Example of Inline Assembler::
28973 * Output Variables in Inline Assembler::
28974 * Input Variables in Inline Assembler::
28975 * Inlining Inline Assembler Code::
28976 * Other Asm Functionality::
28979 @c ---------------------------------------------------------------------------
28980 @node Basic Assembler Syntax
28981 @section Basic Assembler Syntax
28984 The assembler used by GNAT and gcc is based not on the Intel assembly
28985 language, but rather on a language that descends from the AT&T Unix
28986 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
28987 The following table summarizes the main features of @emph{as} syntax
28988 and points out the differences from the Intel conventions.
28989 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
28990 pre-processor) documentation for further information.
28993 @item Register names
28994 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
28996 Intel: No extra punctuation; for example @code{eax}
28998 @item Immediate operand
28999 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29001 Intel: No extra punctuation; for example @code{4}
29004 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29006 Intel: No extra punctuation; for example @code{loc}
29008 @item Memory contents
29009 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29011 Intel: Square brackets; for example @code{[loc]}
29013 @item Register contents
29014 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29016 Intel: Square brackets; for example @code{[eax]}
29018 @item Hexadecimal numbers
29019 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29021 Intel: Trailing ``h''; for example @code{A0h}
29024 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29027 Intel: Implicit, deduced by assembler; for example @code{mov}
29029 @item Instruction repetition
29030 gcc / @emph{as}: Split into two lines; for example
29036 Intel: Keep on one line; for example @code{rep stosl}
29038 @item Order of operands
29039 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29041 Intel: Destination first; for example @code{mov eax, 4}
29044 @c ---------------------------------------------------------------------------
29045 @node A Simple Example of Inline Assembler
29046 @section A Simple Example of Inline Assembler
29049 The following example will generate a single assembly language statement,
29050 @code{nop}, which does nothing. Despite its lack of run-time effect,
29051 the example will be useful in illustrating the basics of
29052 the Inline Assembler facility.
29054 @smallexample @c ada
29056 with System.Machine_Code; use System.Machine_Code;
29057 procedure Nothing is
29064 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29065 here it takes one parameter, a @emph{template string} that must be a static
29066 expression and that will form the generated instruction.
29067 @code{Asm} may be regarded as a compile-time procedure that parses
29068 the template string and additional parameters (none here),
29069 from which it generates a sequence of assembly language instructions.
29071 The examples in this chapter will illustrate several of the forms
29072 for invoking @code{Asm}; a complete specification of the syntax
29073 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29076 Under the standard GNAT conventions, the @code{Nothing} procedure
29077 should be in a file named @file{nothing.adb}.
29078 You can build the executable in the usual way:
29082 However, the interesting aspect of this example is not its run-time behavior
29083 but rather the generated assembly code.
29084 To see this output, invoke the compiler as follows:
29086 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29088 where the options are:
29092 compile only (no bind or link)
29094 generate assembler listing
29095 @item -fomit-frame-pointer
29096 do not set up separate stack frames
29098 do not add runtime checks
29101 This gives a human-readable assembler version of the code. The resulting
29102 file will have the same name as the Ada source file, but with a @code{.s}
29103 extension. In our example, the file @file{nothing.s} has the following
29108 .file "nothing.adb"
29110 ___gnu_compiled_ada:
29113 .globl __ada_nothing
29125 The assembly code you included is clearly indicated by
29126 the compiler, between the @code{#APP} and @code{#NO_APP}
29127 delimiters. The character before the 'APP' and 'NOAPP'
29128 can differ on different targets. For example, GNU/Linux uses '#APP' while
29129 on NT you will see '/APP'.
29131 If you make a mistake in your assembler code (such as using the
29132 wrong size modifier, or using a wrong operand for the instruction) GNAT
29133 will report this error in a temporary file, which will be deleted when
29134 the compilation is finished. Generating an assembler file will help
29135 in such cases, since you can assemble this file separately using the
29136 @emph{as} assembler that comes with gcc.
29138 Assembling the file using the command
29141 as @file{nothing.s}
29144 will give you error messages whose lines correspond to the assembler
29145 input file, so you can easily find and correct any mistakes you made.
29146 If there are no errors, @emph{as} will generate an object file
29147 @file{nothing.out}.
29149 @c ---------------------------------------------------------------------------
29150 @node Output Variables in Inline Assembler
29151 @section Output Variables in Inline Assembler
29154 The examples in this section, showing how to access the processor flags,
29155 illustrate how to specify the destination operands for assembly language
29158 @smallexample @c ada
29160 with Interfaces; use Interfaces;
29161 with Ada.Text_IO; use Ada.Text_IO;
29162 with System.Machine_Code; use System.Machine_Code;
29163 procedure Get_Flags is
29164 Flags : Unsigned_32;
29167 Asm ("pushfl" & LF & HT & -- push flags on stack
29168 "popl %%eax" & LF & HT & -- load eax with flags
29169 "movl %%eax, %0", -- store flags in variable
29170 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29171 Put_Line ("Flags register:" & Flags'Img);
29176 In order to have a nicely aligned assembly listing, we have separated
29177 multiple assembler statements in the Asm template string with linefeed
29178 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29179 The resulting section of the assembly output file is:
29186 movl %eax, -40(%ebp)
29191 It would have been legal to write the Asm invocation as:
29194 Asm ("pushfl popl %%eax movl %%eax, %0")
29197 but in the generated assembler file, this would come out as:
29201 pushfl popl %eax movl %eax, -40(%ebp)
29205 which is not so convenient for the human reader.
29207 We use Ada comments
29208 at the end of each line to explain what the assembler instructions
29209 actually do. This is a useful convention.
29211 When writing Inline Assembler instructions, you need to precede each register
29212 and variable name with a percent sign. Since the assembler already requires
29213 a percent sign at the beginning of a register name, you need two consecutive
29214 percent signs for such names in the Asm template string, thus @code{%%eax}.
29215 In the generated assembly code, one of the percent signs will be stripped off.
29217 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29218 variables: operands you later define using @code{Input} or @code{Output}
29219 parameters to @code{Asm}.
29220 An output variable is illustrated in
29221 the third statement in the Asm template string:
29225 The intent is to store the contents of the eax register in a variable that can
29226 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29227 necessarily work, since the compiler might optimize by using a register
29228 to hold Flags, and the expansion of the @code{movl} instruction would not be
29229 aware of this optimization. The solution is not to store the result directly
29230 but rather to advise the compiler to choose the correct operand form;
29231 that is the purpose of the @code{%0} output variable.
29233 Information about the output variable is supplied in the @code{Outputs}
29234 parameter to @code{Asm}:
29236 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29239 The output is defined by the @code{Asm_Output} attribute of the target type;
29240 the general format is
29242 Type'Asm_Output (constraint_string, variable_name)
29245 The constraint string directs the compiler how
29246 to store/access the associated variable. In the example
29248 Unsigned_32'Asm_Output ("=m", Flags);
29250 the @code{"m"} (memory) constraint tells the compiler that the variable
29251 @code{Flags} should be stored in a memory variable, thus preventing
29252 the optimizer from keeping it in a register. In contrast,
29254 Unsigned_32'Asm_Output ("=r", Flags);
29256 uses the @code{"r"} (register) constraint, telling the compiler to
29257 store the variable in a register.
29259 If the constraint is preceded by the equal character (@strong{=}), it tells
29260 the compiler that the variable will be used to store data into it.
29262 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29263 allowing the optimizer to choose whatever it deems best.
29265 There are a fairly large number of constraints, but the ones that are
29266 most useful (for the Intel x86 processor) are the following:
29272 global (i.e.@: can be stored anywhere)
29290 use one of eax, ebx, ecx or edx
29292 use one of eax, ebx, ecx, edx, esi or edi
29295 The full set of constraints is described in the gcc and @emph{as}
29296 documentation; note that it is possible to combine certain constraints
29297 in one constraint string.
29299 You specify the association of an output variable with an assembler operand
29300 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
29302 @smallexample @c ada
29304 Asm ("pushfl" & LF & HT & -- push flags on stack
29305 "popl %%eax" & LF & HT & -- load eax with flags
29306 "movl %%eax, %0", -- store flags in variable
29307 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29311 @code{%0} will be replaced in the expanded code by the appropriate operand,
29313 the compiler decided for the @code{Flags} variable.
29315 In general, you may have any number of output variables:
29318 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29320 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29321 of @code{Asm_Output} attributes
29325 @smallexample @c ada
29327 Asm ("movl %%eax, %0" & LF & HT &
29328 "movl %%ebx, %1" & LF & HT &
29330 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29331 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29332 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29336 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29337 in the Ada program.
29339 As a variation on the @code{Get_Flags} example, we can use the constraints
29340 string to direct the compiler to store the eax register into the @code{Flags}
29341 variable, instead of including the store instruction explicitly in the
29342 @code{Asm} template string:
29344 @smallexample @c ada
29346 with Interfaces; use Interfaces;
29347 with Ada.Text_IO; use Ada.Text_IO;
29348 with System.Machine_Code; use System.Machine_Code;
29349 procedure Get_Flags_2 is
29350 Flags : Unsigned_32;
29353 Asm ("pushfl" & LF & HT & -- push flags on stack
29354 "popl %%eax", -- save flags in eax
29355 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29356 Put_Line ("Flags register:" & Flags'Img);
29362 The @code{"a"} constraint tells the compiler that the @code{Flags}
29363 variable will come from the eax register. Here is the resulting code:
29371 movl %eax,-40(%ebp)
29376 The compiler generated the store of eax into Flags after
29377 expanding the assembler code.
29379 Actually, there was no need to pop the flags into the eax register;
29380 more simply, we could just pop the flags directly into the program variable:
29382 @smallexample @c ada
29384 with Interfaces; use Interfaces;
29385 with Ada.Text_IO; use Ada.Text_IO;
29386 with System.Machine_Code; use System.Machine_Code;
29387 procedure Get_Flags_3 is
29388 Flags : Unsigned_32;
29391 Asm ("pushfl" & LF & HT & -- push flags on stack
29392 "pop %0", -- save flags in Flags
29393 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29394 Put_Line ("Flags register:" & Flags'Img);
29399 @c ---------------------------------------------------------------------------
29400 @node Input Variables in Inline Assembler
29401 @section Input Variables in Inline Assembler
29404 The example in this section illustrates how to specify the source operands
29405 for assembly language statements.
29406 The program simply increments its input value by 1:
29408 @smallexample @c ada
29410 with Interfaces; use Interfaces;
29411 with Ada.Text_IO; use Ada.Text_IO;
29412 with System.Machine_Code; use System.Machine_Code;
29413 procedure Increment is
29415 function Incr (Value : Unsigned_32) return Unsigned_32 is
29416 Result : Unsigned_32;
29419 Inputs => Unsigned_32'Asm_Input ("a", Value),
29420 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29424 Value : Unsigned_32;
29428 Put_Line ("Value before is" & Value'Img);
29429 Value := Incr (Value);
29430 Put_Line ("Value after is" & Value'Img);
29435 The @code{Outputs} parameter to @code{Asm} specifies
29436 that the result will be in the eax register and that it is to be stored
29437 in the @code{Result} variable.
29439 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29440 but with an @code{Asm_Input} attribute.
29441 The @code{"="} constraint, indicating an output value, is not present.
29443 You can have multiple input variables, in the same way that you can have more
29444 than one output variable.
29446 The parameter count (%0, %1) etc, now starts at the first input
29447 statement, and continues with the output statements.
29448 When both parameters use the same variable, the
29449 compiler will treat them as the same %n operand, which is the case here.
29451 Just as the @code{Outputs} parameter causes the register to be stored into the
29452 target variable after execution of the assembler statements, so does the
29453 @code{Inputs} parameter cause its variable to be loaded into the register
29454 before execution of the assembler statements.
29456 Thus the effect of the @code{Asm} invocation is:
29458 @item load the 32-bit value of @code{Value} into eax
29459 @item execute the @code{incl %eax} instruction
29460 @item store the contents of eax into the @code{Result} variable
29463 The resulting assembler file (with @option{-O2} optimization) contains:
29466 _increment__incr.1:
29479 @c ---------------------------------------------------------------------------
29480 @node Inlining Inline Assembler Code
29481 @section Inlining Inline Assembler Code
29484 For a short subprogram such as the @code{Incr} function in the previous
29485 section, the overhead of the call and return (creating / deleting the stack
29486 frame) can be significant, compared to the amount of code in the subprogram
29487 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29488 which directs the compiler to expand invocations of the subprogram at the
29489 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29490 Here is the resulting program:
29492 @smallexample @c ada
29494 with Interfaces; use Interfaces;
29495 with Ada.Text_IO; use Ada.Text_IO;
29496 with System.Machine_Code; use System.Machine_Code;
29497 procedure Increment_2 is
29499 function Incr (Value : Unsigned_32) return Unsigned_32 is
29500 Result : Unsigned_32;
29503 Inputs => Unsigned_32'Asm_Input ("a", Value),
29504 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29507 pragma Inline (Increment);
29509 Value : Unsigned_32;
29513 Put_Line ("Value before is" & Value'Img);
29514 Value := Increment (Value);
29515 Put_Line ("Value after is" & Value'Img);
29520 Compile the program with both optimization (@option{-O2}) and inlining
29521 (@option{-gnatn}) enabled.
29523 The @code{Incr} function is still compiled as usual, but at the
29524 point in @code{Increment} where our function used to be called:
29529 call _increment__incr.1
29534 the code for the function body directly appears:
29547 thus saving the overhead of stack frame setup and an out-of-line call.
29549 @c ---------------------------------------------------------------------------
29550 @node Other Asm Functionality
29551 @section Other @code{Asm} Functionality
29554 This section describes two important parameters to the @code{Asm}
29555 procedure: @code{Clobber}, which identifies register usage;
29556 and @code{Volatile}, which inhibits unwanted optimizations.
29559 * The Clobber Parameter::
29560 * The Volatile Parameter::
29563 @c ---------------------------------------------------------------------------
29564 @node The Clobber Parameter
29565 @subsection The @code{Clobber} Parameter
29568 One of the dangers of intermixing assembly language and a compiled language
29569 such as Ada is that the compiler needs to be aware of which registers are
29570 being used by the assembly code. In some cases, such as the earlier examples,
29571 the constraint string is sufficient to indicate register usage (e.g.,
29573 the eax register). But more generally, the compiler needs an explicit
29574 identification of the registers that are used by the Inline Assembly
29577 Using a register that the compiler doesn't know about
29578 could be a side effect of an instruction (like @code{mull}
29579 storing its result in both eax and edx).
29580 It can also arise from explicit register usage in your
29581 assembly code; for example:
29584 Asm ("movl %0, %%ebx" & LF & HT &
29586 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29587 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
29591 where the compiler (since it does not analyze the @code{Asm} template string)
29592 does not know you are using the ebx register.
29594 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
29595 to identify the registers that will be used by your assembly code:
29599 Asm ("movl %0, %%ebx" & LF & HT &
29601 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29602 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29607 The Clobber parameter is a static string expression specifying the
29608 register(s) you are using. Note that register names are @emph{not} prefixed
29609 by a percent sign. Also, if more than one register is used then their names
29610 are separated by commas; e.g., @code{"eax, ebx"}
29612 The @code{Clobber} parameter has several additional uses:
29614 @item Use ``register'' name @code{cc} to indicate that flags might have changed
29615 @item Use ``register'' name @code{memory} if you changed a memory location
29618 @c ---------------------------------------------------------------------------
29619 @node The Volatile Parameter
29620 @subsection The @code{Volatile} Parameter
29621 @cindex Volatile parameter
29624 Compiler optimizations in the presence of Inline Assembler may sometimes have
29625 unwanted effects. For example, when an @code{Asm} invocation with an input
29626 variable is inside a loop, the compiler might move the loading of the input
29627 variable outside the loop, regarding it as a one-time initialization.
29629 If this effect is not desired, you can disable such optimizations by setting
29630 the @code{Volatile} parameter to @code{True}; for example:
29632 @smallexample @c ada
29634 Asm ("movl %0, %%ebx" & LF & HT &
29636 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29637 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29643 By default, @code{Volatile} is set to @code{False} unless there is no
29644 @code{Outputs} parameter.
29646 Although setting @code{Volatile} to @code{True} prevents unwanted
29647 optimizations, it will also disable other optimizations that might be
29648 important for efficiency. In general, you should set @code{Volatile}
29649 to @code{True} only if the compiler's optimizations have created
29651 @c END OF INLINE ASSEMBLER CHAPTER
29652 @c ===============================
29654 @c ***********************************
29655 @c * Compatibility and Porting Guide *
29656 @c ***********************************
29657 @node Compatibility and Porting Guide
29658 @appendix Compatibility and Porting Guide
29661 This chapter describes the compatibility issues that may arise between
29662 GNAT and other Ada compilation systems (including those for Ada 83),
29663 and shows how GNAT can expedite porting
29664 applications developed in other Ada environments.
29667 * Compatibility with Ada 83::
29668 * Compatibility between Ada 95 and Ada 2005::
29669 * Implementation-dependent characteristics::
29670 * Compatibility with Other Ada Systems::
29671 * Representation Clauses::
29673 @c Brief section is only in non-VMS version
29674 @c Full chapter is in VMS version
29675 * Compatibility with HP Ada 83::
29678 * Transitioning to 64-Bit GNAT for OpenVMS::
29682 @node Compatibility with Ada 83
29683 @section Compatibility with Ada 83
29684 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
29687 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
29688 particular, the design intention was that the difficulties associated
29689 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
29690 that occur when moving from one Ada 83 system to another.
29692 However, there are a number of points at which there are minor
29693 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
29694 full details of these issues,
29695 and should be consulted for a complete treatment.
29697 following subsections treat the most likely issues to be encountered.
29700 * Legal Ada 83 programs that are illegal in Ada 95::
29701 * More deterministic semantics::
29702 * Changed semantics::
29703 * Other language compatibility issues::
29706 @node Legal Ada 83 programs that are illegal in Ada 95
29707 @subsection Legal Ada 83 programs that are illegal in Ada 95
29709 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
29710 Ada 95 and thus also in Ada 2005:
29713 @item Character literals
29714 Some uses of character literals are ambiguous. Since Ada 95 has introduced
29715 @code{Wide_Character} as a new predefined character type, some uses of
29716 character literals that were legal in Ada 83 are illegal in Ada 95.
29718 @smallexample @c ada
29719 for Char in 'A' .. 'Z' loop @dots{} end loop;
29723 The problem is that @code{'A'} and @code{'Z'} could be from either
29724 @code{Character} or @code{Wide_Character}. The simplest correction
29725 is to make the type explicit; e.g.:
29726 @smallexample @c ada
29727 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
29730 @item New reserved words
29731 The identifiers @code{abstract}, @code{aliased}, @code{protected},
29732 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
29733 Existing Ada 83 code using any of these identifiers must be edited to
29734 use some alternative name.
29736 @item Freezing rules
29737 The rules in Ada 95 are slightly different with regard to the point at
29738 which entities are frozen, and representation pragmas and clauses are
29739 not permitted past the freeze point. This shows up most typically in
29740 the form of an error message complaining that a representation item
29741 appears too late, and the appropriate corrective action is to move
29742 the item nearer to the declaration of the entity to which it refers.
29744 A particular case is that representation pragmas
29747 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
29749 cannot be applied to a subprogram body. If necessary, a separate subprogram
29750 declaration must be introduced to which the pragma can be applied.
29752 @item Optional bodies for library packages
29753 In Ada 83, a package that did not require a package body was nevertheless
29754 allowed to have one. This lead to certain surprises in compiling large
29755 systems (situations in which the body could be unexpectedly ignored by the
29756 binder). In Ada 95, if a package does not require a body then it is not
29757 permitted to have a body. To fix this problem, simply remove a redundant
29758 body if it is empty, or, if it is non-empty, introduce a dummy declaration
29759 into the spec that makes the body required. One approach is to add a private
29760 part to the package declaration (if necessary), and define a parameterless
29761 procedure called @code{Requires_Body}, which must then be given a dummy
29762 procedure body in the package body, which then becomes required.
29763 Another approach (assuming that this does not introduce elaboration
29764 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
29765 since one effect of this pragma is to require the presence of a package body.
29767 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
29768 In Ada 95, the exception @code{Numeric_Error} is a renaming of
29769 @code{Constraint_Error}.
29770 This means that it is illegal to have separate exception handlers for
29771 the two exceptions. The fix is simply to remove the handler for the
29772 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
29773 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
29775 @item Indefinite subtypes in generics
29776 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
29777 as the actual for a generic formal private type, but then the instantiation
29778 would be illegal if there were any instances of declarations of variables
29779 of this type in the generic body. In Ada 95, to avoid this clear violation
29780 of the methodological principle known as the ``contract model'',
29781 the generic declaration explicitly indicates whether
29782 or not such instantiations are permitted. If a generic formal parameter
29783 has explicit unknown discriminants, indicated by using @code{(<>)} after the
29784 type name, then it can be instantiated with indefinite types, but no
29785 stand-alone variables can be declared of this type. Any attempt to declare
29786 such a variable will result in an illegality at the time the generic is
29787 declared. If the @code{(<>)} notation is not used, then it is illegal
29788 to instantiate the generic with an indefinite type.
29789 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
29790 It will show up as a compile time error, and
29791 the fix is usually simply to add the @code{(<>)} to the generic declaration.
29794 @node More deterministic semantics
29795 @subsection More deterministic semantics
29799 Conversions from real types to integer types round away from 0. In Ada 83
29800 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
29801 implementation freedom was intended to support unbiased rounding in
29802 statistical applications, but in practice it interfered with portability.
29803 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
29804 is required. Numeric code may be affected by this change in semantics.
29805 Note, though, that this issue is no worse than already existed in Ada 83
29806 when porting code from one vendor to another.
29809 The Real-Time Annex introduces a set of policies that define the behavior of
29810 features that were implementation dependent in Ada 83, such as the order in
29811 which open select branches are executed.
29814 @node Changed semantics
29815 @subsection Changed semantics
29818 The worst kind of incompatibility is one where a program that is legal in
29819 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
29820 possible in Ada 83. Fortunately this is extremely rare, but the one
29821 situation that you should be alert to is the change in the predefined type
29822 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
29825 @item Range of type @code{Character}
29826 The range of @code{Standard.Character} is now the full 256 characters
29827 of Latin-1, whereas in most Ada 83 implementations it was restricted
29828 to 128 characters. Although some of the effects of
29829 this change will be manifest in compile-time rejection of legal
29830 Ada 83 programs it is possible for a working Ada 83 program to have
29831 a different effect in Ada 95, one that was not permitted in Ada 83.
29832 As an example, the expression
29833 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
29834 delivers @code{255} as its value.
29835 In general, you should look at the logic of any
29836 character-processing Ada 83 program and see whether it needs to be adapted
29837 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
29838 character handling package that may be relevant if code needs to be adapted
29839 to account for the additional Latin-1 elements.
29840 The desirable fix is to
29841 modify the program to accommodate the full character set, but in some cases
29842 it may be convenient to define a subtype or derived type of Character that
29843 covers only the restricted range.
29847 @node Other language compatibility issues
29848 @subsection Other language compatibility issues
29851 @item @option{-gnat83} switch
29852 All implementations of GNAT provide a switch that causes GNAT to operate
29853 in Ada 83 mode. In this mode, some but not all compatibility problems
29854 of the type described above are handled automatically. For example, the
29855 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
29856 as identifiers as in Ada 83.
29858 in practice, it is usually advisable to make the necessary modifications
29859 to the program to remove the need for using this switch.
29860 See @ref{Compiling Different Versions of Ada}.
29862 @item Support for removed Ada 83 pragmas and attributes
29863 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
29864 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
29865 compilers are allowed, but not required, to implement these missing
29866 elements. In contrast with some other compilers, GNAT implements all
29867 such pragmas and attributes, eliminating this compatibility concern. These
29868 include @code{pragma Interface} and the floating point type attributes
29869 (@code{Emax}, @code{Mantissa}, etc.), among other items.
29873 @node Compatibility between Ada 95 and Ada 2005
29874 @section Compatibility between Ada 95 and Ada 2005
29875 @cindex Compatibility between Ada 95 and Ada 2005
29878 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
29879 a number of incompatibilities. Several are enumerated below;
29880 for a complete description please see the
29881 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
29882 @cite{Rationale for Ada 2005}.
29885 @item New reserved words.
29886 The words @code{interface}, @code{overriding} and @code{synchronized} are
29887 reserved in Ada 2005.
29888 A pre-Ada 2005 program that uses any of these as an identifier will be
29891 @item New declarations in predefined packages.
29892 A number of packages in the predefined environment contain new declarations:
29893 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
29894 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
29895 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
29896 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
29897 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
29898 If an Ada 95 program does a @code{with} and @code{use} of any of these
29899 packages, the new declarations may cause name clashes.
29901 @item Access parameters.
29902 A nondispatching subprogram with an access parameter cannot be renamed
29903 as a dispatching operation. This was permitted in Ada 95.
29905 @item Access types, discriminants, and constraints.
29906 Rule changes in this area have led to some incompatibilities; for example,
29907 constrained subtypes of some access types are not permitted in Ada 2005.
29909 @item Aggregates for limited types.
29910 The allowance of aggregates for limited types in Ada 2005 raises the
29911 possibility of ambiguities in legal Ada 95 programs, since additional types
29912 now need to be considered in expression resolution.
29914 @item Fixed-point multiplication and division.
29915 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
29916 were legal in Ada 95 and invoked the predefined versions of these operations,
29918 The ambiguity may be resolved either by applying a type conversion to the
29919 expression, or by explicitly invoking the operation from package
29922 @item Return-by-reference types.
29923 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
29924 can declare a function returning a value from an anonymous access type.
29928 @node Implementation-dependent characteristics
29929 @section Implementation-dependent characteristics
29931 Although the Ada language defines the semantics of each construct as
29932 precisely as practical, in some situations (for example for reasons of
29933 efficiency, or where the effect is heavily dependent on the host or target
29934 platform) the implementation is allowed some freedom. In porting Ada 83
29935 code to GNAT, you need to be aware of whether / how the existing code
29936 exercised such implementation dependencies. Such characteristics fall into
29937 several categories, and GNAT offers specific support in assisting the
29938 transition from certain Ada 83 compilers.
29941 * Implementation-defined pragmas::
29942 * Implementation-defined attributes::
29944 * Elaboration order::
29945 * Target-specific aspects::
29948 @node Implementation-defined pragmas
29949 @subsection Implementation-defined pragmas
29952 Ada compilers are allowed to supplement the language-defined pragmas, and
29953 these are a potential source of non-portability. All GNAT-defined pragmas
29954 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
29955 Reference Manual}, and these include several that are specifically
29956 intended to correspond to other vendors' Ada 83 pragmas.
29957 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
29958 For compatibility with HP Ada 83, GNAT supplies the pragmas
29959 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
29960 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
29961 and @code{Volatile}.
29962 Other relevant pragmas include @code{External} and @code{Link_With}.
29963 Some vendor-specific
29964 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
29966 avoiding compiler rejection of units that contain such pragmas; they are not
29967 relevant in a GNAT context and hence are not otherwise implemented.
29969 @node Implementation-defined attributes
29970 @subsection Implementation-defined attributes
29972 Analogous to pragmas, the set of attributes may be extended by an
29973 implementation. All GNAT-defined attributes are described in
29974 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
29975 Manual}, and these include several that are specifically intended
29976 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
29977 the attribute @code{VADS_Size} may be useful. For compatibility with HP
29978 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
29982 @subsection Libraries
29984 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
29985 code uses vendor-specific libraries then there are several ways to manage
29986 this in Ada 95 or Ada 2005:
29989 If the source code for the libraries (specs and bodies) are
29990 available, then the libraries can be migrated in the same way as the
29993 If the source code for the specs but not the bodies are
29994 available, then you can reimplement the bodies.
29996 Some features introduced by Ada 95 obviate the need for library support. For
29997 example most Ada 83 vendors supplied a package for unsigned integers. The
29998 Ada 95 modular type feature is the preferred way to handle this need, so
29999 instead of migrating or reimplementing the unsigned integer package it may
30000 be preferable to retrofit the application using modular types.
30003 @node Elaboration order
30004 @subsection Elaboration order
30006 The implementation can choose any elaboration order consistent with the unit
30007 dependency relationship. This freedom means that some orders can result in
30008 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30009 to invoke a subprogram its body has been elaborated, or to instantiate a
30010 generic before the generic body has been elaborated. By default GNAT
30011 attempts to choose a safe order (one that will not encounter access before
30012 elaboration problems) by implicitly inserting @code{Elaborate} or
30013 @code{Elaborate_All} pragmas where
30014 needed. However, this can lead to the creation of elaboration circularities
30015 and a resulting rejection of the program by gnatbind. This issue is
30016 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30017 In brief, there are several
30018 ways to deal with this situation:
30022 Modify the program to eliminate the circularities, e.g.@: by moving
30023 elaboration-time code into explicitly-invoked procedures
30025 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30026 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30027 @code{Elaborate_All}
30028 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30029 (by selectively suppressing elaboration checks via pragma
30030 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30033 @node Target-specific aspects
30034 @subsection Target-specific aspects
30036 Low-level applications need to deal with machine addresses, data
30037 representations, interfacing with assembler code, and similar issues. If
30038 such an Ada 83 application is being ported to different target hardware (for
30039 example where the byte endianness has changed) then you will need to
30040 carefully examine the program logic; the porting effort will heavily depend
30041 on the robustness of the original design. Moreover, Ada 95 (and thus
30042 Ada 2005) are sometimes
30043 incompatible with typical Ada 83 compiler practices regarding implicit
30044 packing, the meaning of the Size attribute, and the size of access values.
30045 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30047 @node Compatibility with Other Ada Systems
30048 @section Compatibility with Other Ada Systems
30051 If programs avoid the use of implementation dependent and
30052 implementation defined features, as documented in the @cite{Ada
30053 Reference Manual}, there should be a high degree of portability between
30054 GNAT and other Ada systems. The following are specific items which
30055 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30056 compilers, but do not affect porting code to GNAT@.
30057 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30058 the following issues may or may not arise for Ada 2005 programs
30059 when other compilers appear.)
30062 @item Ada 83 Pragmas and Attributes
30063 Ada 95 compilers are allowed, but not required, to implement the missing
30064 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30065 GNAT implements all such pragmas and attributes, eliminating this as
30066 a compatibility concern, but some other Ada 95 compilers reject these
30067 pragmas and attributes.
30069 @item Specialized Needs Annexes
30070 GNAT implements the full set of special needs annexes. At the
30071 current time, it is the only Ada 95 compiler to do so. This means that
30072 programs making use of these features may not be portable to other Ada
30073 95 compilation systems.
30075 @item Representation Clauses
30076 Some other Ada 95 compilers implement only the minimal set of
30077 representation clauses required by the Ada 95 reference manual. GNAT goes
30078 far beyond this minimal set, as described in the next section.
30081 @node Representation Clauses
30082 @section Representation Clauses
30085 The Ada 83 reference manual was quite vague in describing both the minimal
30086 required implementation of representation clauses, and also their precise
30087 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30088 minimal set of capabilities required is still quite limited.
30090 GNAT implements the full required set of capabilities in
30091 Ada 95 and Ada 2005, but also goes much further, and in particular
30092 an effort has been made to be compatible with existing Ada 83 usage to the
30093 greatest extent possible.
30095 A few cases exist in which Ada 83 compiler behavior is incompatible with
30096 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30097 intentional or accidental dependence on specific implementation dependent
30098 characteristics of these Ada 83 compilers. The following is a list of
30099 the cases most likely to arise in existing Ada 83 code.
30102 @item Implicit Packing
30103 Some Ada 83 compilers allowed a Size specification to cause implicit
30104 packing of an array or record. This could cause expensive implicit
30105 conversions for change of representation in the presence of derived
30106 types, and the Ada design intends to avoid this possibility.
30107 Subsequent AI's were issued to make it clear that such implicit
30108 change of representation in response to a Size clause is inadvisable,
30109 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30110 Reference Manuals as implementation advice that is followed by GNAT@.
30111 The problem will show up as an error
30112 message rejecting the size clause. The fix is simply to provide
30113 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30114 a Component_Size clause.
30116 @item Meaning of Size Attribute
30117 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30118 the minimal number of bits required to hold values of the type. For example,
30119 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30120 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30121 some 32 in this situation. This problem will usually show up as a compile
30122 time error, but not always. It is a good idea to check all uses of the
30123 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30124 Object_Size can provide a useful way of duplicating the behavior of
30125 some Ada 83 compiler systems.
30127 @item Size of Access Types
30128 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30129 and that therefore it will be the same size as a System.Address value. This
30130 assumption is true for GNAT in most cases with one exception. For the case of
30131 a pointer to an unconstrained array type (where the bounds may vary from one
30132 value of the access type to another), the default is to use a ``fat pointer'',
30133 which is represented as two separate pointers, one to the bounds, and one to
30134 the array. This representation has a number of advantages, including improved
30135 efficiency. However, it may cause some difficulties in porting existing Ada 83
30136 code which makes the assumption that, for example, pointers fit in 32 bits on
30137 a machine with 32-bit addressing.
30139 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30140 access types in this case (where the designated type is an unconstrained array
30141 type). These thin pointers are indeed the same size as a System.Address value.
30142 To specify a thin pointer, use a size clause for the type, for example:
30144 @smallexample @c ada
30145 type X is access all String;
30146 for X'Size use Standard'Address_Size;
30150 which will cause the type X to be represented using a single pointer.
30151 When using this representation, the bounds are right behind the array.
30152 This representation is slightly less efficient, and does not allow quite
30153 such flexibility in the use of foreign pointers or in using the
30154 Unrestricted_Access attribute to create pointers to non-aliased objects.
30155 But for any standard portable use of the access type it will work in
30156 a functionally correct manner and allow porting of existing code.
30157 Note that another way of forcing a thin pointer representation
30158 is to use a component size clause for the element size in an array,
30159 or a record representation clause for an access field in a record.
30163 @c This brief section is only in the non-VMS version
30164 @c The complete chapter on HP Ada is in the VMS version
30165 @node Compatibility with HP Ada 83
30166 @section Compatibility with HP Ada 83
30169 The VMS version of GNAT fully implements all the pragmas and attributes
30170 provided by HP Ada 83, as well as providing the standard HP Ada 83
30171 libraries, including Starlet. In addition, data layouts and parameter
30172 passing conventions are highly compatible. This means that porting
30173 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30174 most other porting efforts. The following are some of the most
30175 significant differences between GNAT and HP Ada 83.
30178 @item Default floating-point representation
30179 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30180 it is VMS format. GNAT does implement the necessary pragmas
30181 (Long_Float, Float_Representation) for changing this default.
30184 The package System in GNAT exactly corresponds to the definition in the
30185 Ada 95 reference manual, which means that it excludes many of the
30186 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30187 that contains the additional definitions, and a special pragma,
30188 Extend_System allows this package to be treated transparently as an
30189 extension of package System.
30192 The definitions provided by Aux_DEC are exactly compatible with those
30193 in the HP Ada 83 version of System, with one exception.
30194 HP Ada provides the following declarations:
30196 @smallexample @c ada
30197 TO_ADDRESS (INTEGER)
30198 TO_ADDRESS (UNSIGNED_LONGWORD)
30199 TO_ADDRESS (@i{universal_integer})
30203 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30204 an extension to Ada 83 not strictly compatible with the reference manual.
30205 In GNAT, we are constrained to be exactly compatible with the standard,
30206 and this means we cannot provide this capability. In HP Ada 83, the
30207 point of this definition is to deal with a call like:
30209 @smallexample @c ada
30210 TO_ADDRESS (16#12777#);
30214 Normally, according to the Ada 83 standard, one would expect this to be
30215 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30216 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30217 definition using @i{universal_integer} takes precedence.
30219 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30220 is not possible to be 100% compatible. Since there are many programs using
30221 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30222 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30223 declarations provided in the GNAT version of AUX_Dec are:
30225 @smallexample @c ada
30226 function To_Address (X : Integer) return Address;
30227 pragma Pure_Function (To_Address);
30229 function To_Address_Long (X : Unsigned_Longword)
30231 pragma Pure_Function (To_Address_Long);
30235 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
30236 change the name to TO_ADDRESS_LONG@.
30238 @item Task_Id values
30239 The Task_Id values assigned will be different in the two systems, and GNAT
30240 does not provide a specified value for the Task_Id of the environment task,
30241 which in GNAT is treated like any other declared task.
30245 For full details on these and other less significant compatibility issues,
30246 see appendix E of the HP publication entitled @cite{HP Ada, Technical
30247 Overview and Comparison on HP Platforms}.
30249 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
30250 attributes are recognized, although only a subset of them can sensibly
30251 be implemented. The description of pragmas in @ref{Implementation
30252 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
30253 indicates whether or not they are applicable to non-VMS systems.
30257 @node Transitioning to 64-Bit GNAT for OpenVMS
30258 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
30261 This section is meant to assist users of pre-2006 @value{EDITION}
30262 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
30263 the version of the GNAT technology supplied in 2006 and later for
30264 OpenVMS on both Alpha and I64.
30267 * Introduction to transitioning::
30268 * Migration of 32 bit code::
30269 * Taking advantage of 64 bit addressing::
30270 * Technical details::
30273 @node Introduction to transitioning
30274 @subsection Introduction
30277 64-bit @value{EDITION} for Open VMS has been designed to meet
30282 Providing a full conforming implementation of Ada 95 and Ada 2005
30285 Allowing maximum backward compatibility, thus easing migration of existing
30289 Supplying a path for exploiting the full 64-bit address range
30293 Ada's strong typing semantics has made it
30294 impractical to have different 32-bit and 64-bit modes. As soon as
30295 one object could possibly be outside the 32-bit address space, this
30296 would make it necessary for the @code{System.Address} type to be 64 bits.
30297 In particular, this would cause inconsistencies if 32-bit code is
30298 called from 64-bit code that raises an exception.
30300 This issue has been resolved by always using 64-bit addressing
30301 at the system level, but allowing for automatic conversions between
30302 32-bit and 64-bit addresses where required. Thus users who
30303 do not currently require 64-bit addressing capabilities, can
30304 recompile their code with only minimal changes (and indeed
30305 if the code is written in portable Ada, with no assumptions about
30306 the size of the @code{Address} type, then no changes at all are necessary).
30308 this approach provides a simple, gradual upgrade path to future
30309 use of larger memories than available for 32-bit systems.
30310 Also, newly written applications or libraries will by default
30311 be fully compatible with future systems exploiting 64-bit
30312 addressing capabilities.
30314 @ref{Migration of 32 bit code}, will focus on porting applications
30315 that do not require more than 2 GB of
30316 addressable memory. This code will be referred to as
30317 @emph{32-bit code}.
30318 For applications intending to exploit the full 64-bit address space,
30319 @ref{Taking advantage of 64 bit addressing},
30320 will consider further changes that may be required.
30321 Such code will be referred to below as @emph{64-bit code}.
30323 @node Migration of 32 bit code
30324 @subsection Migration of 32-bit code
30329 * Unchecked conversions::
30330 * Predefined constants::
30331 * Interfacing with C::
30332 * Experience with source compatibility::
30335 @node Address types
30336 @subsubsection Address types
30339 To solve the problem of mixing 64-bit and 32-bit addressing,
30340 while maintaining maximum backward compatibility, the following
30341 approach has been taken:
30345 @code{System.Address} always has a size of 64 bits
30348 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
30352 Since @code{System.Short_Address} is a subtype of @code{System.Address},
30353 a @code{Short_Address}
30354 may be used where an @code{Address} is required, and vice versa, without
30355 needing explicit type conversions.
30356 By virtue of the Open VMS parameter passing conventions,
30358 and exported subprograms that have 32-bit address parameters are
30359 compatible with those that have 64-bit address parameters.
30360 (See @ref{Making code 64 bit clean} for details.)
30362 The areas that may need attention are those where record types have
30363 been defined that contain components of the type @code{System.Address}, and
30364 where objects of this type are passed to code expecting a record layout with
30367 Different compilers on different platforms cannot be
30368 expected to represent the same type in the same way,
30369 since alignment constraints
30370 and other system-dependent properties affect the compiler's decision.
30371 For that reason, Ada code
30372 generally uses representation clauses to specify the expected
30373 layout where required.
30375 If such a representation clause uses 32 bits for a component having
30376 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
30377 will detect that error and produce a specific diagnostic message.
30378 The developer should then determine whether the representation
30379 should be 64 bits or not and make either of two changes:
30380 change the size to 64 bits and leave the type as @code{System.Address}, or
30381 leave the size as 32 bits and change the type to @code{System.Short_Address}.
30382 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
30383 required in any code setting or accessing the field; the compiler will
30384 automatically perform any needed conversions between address
30388 @subsubsection Access types
30391 By default, objects designated by access values are always
30392 allocated in the 32-bit
30393 address space. Thus legacy code will never contain
30394 any objects that are not addressable with 32-bit addresses, and
30395 the compiler will never raise exceptions as result of mixing
30396 32-bit and 64-bit addresses.
30398 However, the access values themselves are represented in 64 bits, for optimum
30399 performance and future compatibility with 64-bit code. As was
30400 the case with @code{System.Address}, the compiler will give an error message
30401 if an object or record component has a representation clause that
30402 requires the access value to fit in 32 bits. In such a situation,
30403 an explicit size clause for the access type, specifying 32 bits,
30404 will have the desired effect.
30406 General access types (declared with @code{access all}) can never be
30407 32 bits, as values of such types must be able to refer to any object
30408 of the designated type,
30409 including objects residing outside the 32-bit address range.
30410 Existing Ada 83 code will not contain such type definitions,
30411 however, since general access types were introduced in Ada 95.
30413 @node Unchecked conversions
30414 @subsubsection Unchecked conversions
30417 In the case of an @code{Unchecked_Conversion} where the source type is a
30418 64-bit access type or the type @code{System.Address}, and the target
30419 type is a 32-bit type, the compiler will generate a warning.
30420 Even though the generated code will still perform the required
30421 conversions, it is highly recommended in these cases to use
30422 respectively a 32-bit access type or @code{System.Short_Address}
30423 as the source type.
30425 @node Predefined constants
30426 @subsubsection Predefined constants
30429 The following table shows the correspondence between pre-2006 versions of
30430 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
30433 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
30434 @item @b{Constant} @tab @b{Old} @tab @b{New}
30435 @item @code{System.Word_Size} @tab 32 @tab 64
30436 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
30437 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
30438 @item @code{System.Address_Size} @tab 32 @tab 64
30442 If you need to refer to the specific
30443 memory size of a 32-bit implementation, instead of the
30444 actual memory size, use @code{System.Short_Memory_Size}
30445 rather than @code{System.Memory_Size}.
30446 Similarly, references to @code{System.Address_Size} may need
30447 to be replaced by @code{System.Short_Address'Size}.
30448 The program @command{gnatfind} may be useful for locating
30449 references to the above constants, so that you can verify that they
30452 @node Interfacing with C
30453 @subsubsection Interfacing with C
30456 In order to minimize the impact of the transition to 64-bit addresses on
30457 legacy programs, some fundamental types in the @code{Interfaces.C}
30458 package hierarchy continue to be represented in 32 bits.
30459 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
30460 This eases integration with the default HP C layout choices, for example
30461 as found in the system routines in @code{DECC$SHR.EXE}.
30462 Because of this implementation choice, the type fully compatible with
30463 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
30464 Depending on the context the compiler will issue a
30465 warning or an error when type @code{Address} is used, alerting the user to a
30466 potential problem. Otherwise 32-bit programs that use
30467 @code{Interfaces.C} should normally not require code modifications
30469 The other issue arising with C interfacing concerns pragma @code{Convention}.
30470 For VMS 64-bit systems, there is an issue of the appropriate default size
30471 of C convention pointers in the absence of an explicit size clause. The HP
30472 C compiler can choose either 32 or 64 bits depending on compiler options.
30473 GNAT chooses 32-bits rather than 64-bits in the default case where no size
30474 clause is given. This proves a better choice for porting 32-bit legacy
30475 applications. In order to have a 64-bit representation, it is necessary to
30476 specify a size representation clause. For example:
30478 @smallexample @c ada
30479 type int_star is access Interfaces.C.int;
30480 pragma Convention(C, int_star);
30481 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
30484 @node Experience with source compatibility
30485 @subsubsection Experience with source compatibility
30488 The Security Server and STARLET on I64 provide an interesting ``test case''
30489 for source compatibility issues, since it is in such system code
30490 where assumptions about @code{Address} size might be expected to occur.
30491 Indeed, there were a small number of occasions in the Security Server
30492 file @file{jibdef.ads}
30493 where a representation clause for a record type specified
30494 32 bits for a component of type @code{Address}.
30495 All of these errors were detected by the compiler.
30496 The repair was obvious and immediate; to simply replace @code{Address} by
30497 @code{Short_Address}.
30499 In the case of STARLET, there were several record types that should
30500 have had representation clauses but did not. In these record types
30501 there was an implicit assumption that an @code{Address} value occupied
30503 These compiled without error, but their usage resulted in run-time error
30504 returns from STARLET system calls.
30505 Future GNAT technology enhancements may include a tool that detects and flags
30506 these sorts of potential source code porting problems.
30508 @c ****************************************
30509 @node Taking advantage of 64 bit addressing
30510 @subsection Taking advantage of 64-bit addressing
30513 * Making code 64 bit clean::
30514 * Allocating memory from the 64 bit storage pool::
30515 * Restrictions on use of 64 bit objects::
30516 * Using 64 bit storage pools by default::
30517 * General access types::
30518 * STARLET and other predefined libraries::
30521 @node Making code 64 bit clean
30522 @subsubsection Making code 64-bit clean
30525 In order to prevent problems that may occur when (parts of) a
30526 system start using memory outside the 32-bit address range,
30527 we recommend some additional guidelines:
30531 For imported subprograms that take parameters of the
30532 type @code{System.Address}, ensure that these subprograms can
30533 indeed handle 64-bit addresses. If not, or when in doubt,
30534 change the subprogram declaration to specify
30535 @code{System.Short_Address} instead.
30538 Resolve all warnings related to size mismatches in
30539 unchecked conversions. Failing to do so causes
30540 erroneous execution if the source object is outside
30541 the 32-bit address space.
30544 (optional) Explicitly use the 32-bit storage pool
30545 for access types used in a 32-bit context, or use
30546 generic access types where possible
30547 (@pxref{Restrictions on use of 64 bit objects}).
30551 If these rules are followed, the compiler will automatically insert
30552 any necessary checks to ensure that no addresses or access values
30553 passed to 32-bit code ever refer to objects outside the 32-bit
30555 Any attempt to do this will raise @code{Constraint_Error}.
30557 @node Allocating memory from the 64 bit storage pool
30558 @subsubsection Allocating memory from the 64-bit storage pool
30561 For any access type @code{T} that potentially requires memory allocations
30562 beyond the 32-bit address space,
30563 use the following representation clause:
30565 @smallexample @c ada
30566 for T'Storage_Pool use System.Pool_64;
30569 @node Restrictions on use of 64 bit objects
30570 @subsubsection Restrictions on use of 64-bit objects
30573 Taking the address of an object allocated from a 64-bit storage pool,
30574 and then passing this address to a subprogram expecting
30575 @code{System.Short_Address},
30576 or assigning it to a variable of type @code{Short_Address}, will cause
30577 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
30578 (@pxref{Making code 64 bit clean}), or checks are suppressed,
30579 no exception is raised and execution
30580 will become erroneous.
30582 @node Using 64 bit storage pools by default
30583 @subsubsection Using 64-bit storage pools by default
30586 In some cases it may be desirable to have the compiler allocate
30587 from 64-bit storage pools by default. This may be the case for
30588 libraries that are 64-bit clean, but may be used in both 32-bit
30589 and 64-bit contexts. For these cases the following configuration
30590 pragma may be specified:
30592 @smallexample @c ada
30593 pragma Pool_64_Default;
30597 Any code compiled in the context of this pragma will by default
30598 use the @code{System.Pool_64} storage pool. This default may be overridden
30599 for a specific access type @code{T} by the representation clause:
30601 @smallexample @c ada
30602 for T'Storage_Pool use System.Pool_32;
30606 Any object whose address may be passed to a subprogram with a
30607 @code{Short_Address} argument, or assigned to a variable of type
30608 @code{Short_Address}, needs to be allocated from this pool.
30610 @node General access types
30611 @subsubsection General access types
30614 Objects designated by access values from a
30615 general access type (declared with @code{access all}) are never allocated
30616 from a 64-bit storage pool. Code that uses general access types will
30617 accept objects allocated in either 32-bit or 64-bit address spaces,
30618 but never allocate objects outside the 32-bit address space.
30619 Using general access types ensures maximum compatibility with both
30620 32-bit and 64-bit code.
30622 @node STARLET and other predefined libraries
30623 @subsubsection STARLET and other predefined libraries
30626 All code that comes as part of GNAT is 64-bit clean, but the
30627 restrictions given in @ref{Restrictions on use of 64 bit objects},
30628 still apply. Look at the package
30629 specs to see in which contexts objects allocated
30630 in 64-bit address space are acceptable.
30632 @node Technical details
30633 @subsection Technical details
30636 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
30637 Ada standard with respect to the type of @code{System.Address}. Previous
30638 versions of GNAT Pro have defined this type as private and implemented it as a
30641 In order to allow defining @code{System.Short_Address} as a proper subtype,
30642 and to match the implicit sign extension in parameter passing,
30643 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
30644 visible (i.e., non-private) integer type.
30645 Standard operations on the type, such as the binary operators ``+'', ``-'',
30646 etc., that take @code{Address} operands and return an @code{Address} result,
30647 have been hidden by declaring these
30648 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
30649 ambiguities that would otherwise result from overloading.
30650 (Note that, although @code{Address} is a visible integer type,
30651 good programming practice dictates against exploiting the type's
30652 integer properties such as literals, since this will compromise
30655 Defining @code{Address} as a visible integer type helps achieve
30656 maximum compatibility for existing Ada code,
30657 without sacrificing the capabilities of the 64-bit architecture.
30660 @c ************************************************
30662 @node Microsoft Windows Topics
30663 @appendix Microsoft Windows Topics
30669 This chapter describes topics that are specific to the Microsoft Windows
30670 platforms (NT, 2000, and XP Professional).
30673 * Using GNAT on Windows::
30674 * Using a network installation of GNAT::
30675 * CONSOLE and WINDOWS subsystems::
30676 * Temporary Files::
30677 * Mixed-Language Programming on Windows::
30678 * Windows Calling Conventions::
30679 * Introduction to Dynamic Link Libraries (DLLs)::
30680 * Using DLLs with GNAT::
30681 * Building DLLs with GNAT::
30682 * Building DLLs with GNAT Project files::
30683 * Building DLLs with gnatdll::
30684 * GNAT and Windows Resources::
30685 * Debugging a DLL::
30686 * Setting Stack Size from gnatlink::
30687 * Setting Heap Size from gnatlink::
30690 @node Using GNAT on Windows
30691 @section Using GNAT on Windows
30694 One of the strengths of the GNAT technology is that its tool set
30695 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
30696 @code{gdb} debugger, etc.) is used in the same way regardless of the
30699 On Windows this tool set is complemented by a number of Microsoft-specific
30700 tools that have been provided to facilitate interoperability with Windows
30701 when this is required. With these tools:
30706 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
30710 You can use any Dynamically Linked Library (DLL) in your Ada code (both
30711 relocatable and non-relocatable DLLs are supported).
30714 You can build Ada DLLs for use in other applications. These applications
30715 can be written in a language other than Ada (e.g., C, C++, etc). Again both
30716 relocatable and non-relocatable Ada DLLs are supported.
30719 You can include Windows resources in your Ada application.
30722 You can use or create COM/DCOM objects.
30726 Immediately below are listed all known general GNAT-for-Windows restrictions.
30727 Other restrictions about specific features like Windows Resources and DLLs
30728 are listed in separate sections below.
30733 It is not possible to use @code{GetLastError} and @code{SetLastError}
30734 when tasking, protected records, or exceptions are used. In these
30735 cases, in order to implement Ada semantics, the GNAT run-time system
30736 calls certain Win32 routines that set the last error variable to 0 upon
30737 success. It should be possible to use @code{GetLastError} and
30738 @code{SetLastError} when tasking, protected record, and exception
30739 features are not used, but it is not guaranteed to work.
30742 It is not possible to link against Microsoft libraries except for
30743 import libraries. The library must be built to be compatible with
30744 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
30745 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
30746 not be compatible with the GNAT runtime. Even if the library is
30747 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
30750 When the compilation environment is located on FAT32 drives, users may
30751 experience recompilations of the source files that have not changed if
30752 Daylight Saving Time (DST) state has changed since the last time files
30753 were compiled. NTFS drives do not have this problem.
30756 No components of the GNAT toolset use any entries in the Windows
30757 registry. The only entries that can be created are file associations and
30758 PATH settings, provided the user has chosen to create them at installation
30759 time, as well as some minimal book-keeping information needed to correctly
30760 uninstall or integrate different GNAT products.
30763 @node Using a network installation of GNAT
30764 @section Using a network installation of GNAT
30767 Make sure the system on which GNAT is installed is accessible from the
30768 current machine, i.e., the install location is shared over the network.
30769 Shared resources are accessed on Windows by means of UNC paths, which
30770 have the format @code{\\server\sharename\path}
30772 In order to use such a network installation, simply add the UNC path of the
30773 @file{bin} directory of your GNAT installation in front of your PATH. For
30774 example, if GNAT is installed in @file{\GNAT} directory of a share location
30775 called @file{c-drive} on a machine @file{LOKI}, the following command will
30778 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
30780 Be aware that every compilation using the network installation results in the
30781 transfer of large amounts of data across the network and will likely cause
30782 serious performance penalty.
30784 @node CONSOLE and WINDOWS subsystems
30785 @section CONSOLE and WINDOWS subsystems
30786 @cindex CONSOLE Subsystem
30787 @cindex WINDOWS Subsystem
30791 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
30792 (which is the default subsystem) will always create a console when
30793 launching the application. This is not something desirable when the
30794 application has a Windows GUI. To get rid of this console the
30795 application must be using the @code{WINDOWS} subsystem. To do so
30796 the @option{-mwindows} linker option must be specified.
30799 $ gnatmake winprog -largs -mwindows
30802 @node Temporary Files
30803 @section Temporary Files
30804 @cindex Temporary files
30807 It is possible to control where temporary files gets created by setting
30808 the @env{TMP} environment variable. The file will be created:
30811 @item Under the directory pointed to by the @env{TMP} environment variable if
30812 this directory exists.
30814 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
30815 set (or not pointing to a directory) and if this directory exists.
30817 @item Under the current working directory otherwise.
30821 This allows you to determine exactly where the temporary
30822 file will be created. This is particularly useful in networked
30823 environments where you may not have write access to some
30826 @node Mixed-Language Programming on Windows
30827 @section Mixed-Language Programming on Windows
30830 Developing pure Ada applications on Windows is no different than on
30831 other GNAT-supported platforms. However, when developing or porting an
30832 application that contains a mix of Ada and C/C++, the choice of your
30833 Windows C/C++ development environment conditions your overall
30834 interoperability strategy.
30836 If you use @command{gcc} to compile the non-Ada part of your application,
30837 there are no Windows-specific restrictions that affect the overall
30838 interoperability with your Ada code. If you plan to use
30839 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
30840 the following limitations:
30844 You cannot link your Ada code with an object or library generated with
30845 Microsoft tools if these use the @code{.tls} section (Thread Local
30846 Storage section) since the GNAT linker does not yet support this section.
30849 You cannot link your Ada code with an object or library generated with
30850 Microsoft tools if these use I/O routines other than those provided in
30851 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
30852 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
30853 libraries can cause a conflict with @code{msvcrt.dll} services. For
30854 instance Visual C++ I/O stream routines conflict with those in
30859 If you do want to use the Microsoft tools for your non-Ada code and hit one
30860 of the above limitations, you have two choices:
30864 Encapsulate your non-Ada code in a DLL to be linked with your Ada
30865 application. In this case, use the Microsoft or whatever environment to
30866 build the DLL and use GNAT to build your executable
30867 (@pxref{Using DLLs with GNAT}).
30870 Or you can encapsulate your Ada code in a DLL to be linked with the
30871 other part of your application. In this case, use GNAT to build the DLL
30872 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
30873 environment to build your executable.
30876 @node Windows Calling Conventions
30877 @section Windows Calling Conventions
30882 * C Calling Convention::
30883 * Stdcall Calling Convention::
30884 * Win32 Calling Convention::
30885 * DLL Calling Convention::
30889 When a subprogram @code{F} (caller) calls a subprogram @code{G}
30890 (callee), there are several ways to push @code{G}'s parameters on the
30891 stack and there are several possible scenarios to clean up the stack
30892 upon @code{G}'s return. A calling convention is an agreed upon software
30893 protocol whereby the responsibilities between the caller (@code{F}) and
30894 the callee (@code{G}) are clearly defined. Several calling conventions
30895 are available for Windows:
30899 @code{C} (Microsoft defined)
30902 @code{Stdcall} (Microsoft defined)
30905 @code{Win32} (GNAT specific)
30908 @code{DLL} (GNAT specific)
30911 @node C Calling Convention
30912 @subsection @code{C} Calling Convention
30915 This is the default calling convention used when interfacing to C/C++
30916 routines compiled with either @command{gcc} or Microsoft Visual C++.
30918 In the @code{C} calling convention subprogram parameters are pushed on the
30919 stack by the caller from right to left. The caller itself is in charge of
30920 cleaning up the stack after the call. In addition, the name of a routine
30921 with @code{C} calling convention is mangled by adding a leading underscore.
30923 The name to use on the Ada side when importing (or exporting) a routine
30924 with @code{C} calling convention is the name of the routine. For
30925 instance the C function:
30928 int get_val (long);
30932 should be imported from Ada as follows:
30934 @smallexample @c ada
30936 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
30937 pragma Import (C, Get_Val, External_Name => "get_val");
30942 Note that in this particular case the @code{External_Name} parameter could
30943 have been omitted since, when missing, this parameter is taken to be the
30944 name of the Ada entity in lower case. When the @code{Link_Name} parameter
30945 is missing, as in the above example, this parameter is set to be the
30946 @code{External_Name} with a leading underscore.
30948 When importing a variable defined in C, you should always use the @code{C}
30949 calling convention unless the object containing the variable is part of a
30950 DLL (in which case you should use the @code{Stdcall} calling
30951 convention, @pxref{Stdcall Calling Convention}).
30953 @node Stdcall Calling Convention
30954 @subsection @code{Stdcall} Calling Convention
30957 This convention, which was the calling convention used for Pascal
30958 programs, is used by Microsoft for all the routines in the Win32 API for
30959 efficiency reasons. It must be used to import any routine for which this
30960 convention was specified.
30962 In the @code{Stdcall} calling convention subprogram parameters are pushed
30963 on the stack by the caller from right to left. The callee (and not the
30964 caller) is in charge of cleaning the stack on routine exit. In addition,
30965 the name of a routine with @code{Stdcall} calling convention is mangled by
30966 adding a leading underscore (as for the @code{C} calling convention) and a
30967 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
30968 bytes) of the parameters passed to the routine.
30970 The name to use on the Ada side when importing a C routine with a
30971 @code{Stdcall} calling convention is the name of the C routine. The leading
30972 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
30973 the compiler. For instance the Win32 function:
30976 @b{APIENTRY} int get_val (long);
30980 should be imported from Ada as follows:
30982 @smallexample @c ada
30984 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
30985 pragma Import (Stdcall, Get_Val);
30986 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
30991 As for the @code{C} calling convention, when the @code{External_Name}
30992 parameter is missing, it is taken to be the name of the Ada entity in lower
30993 case. If instead of writing the above import pragma you write:
30995 @smallexample @c ada
30997 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
30998 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31003 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31004 of specifying the @code{External_Name} parameter you specify the
31005 @code{Link_Name} as in the following example:
31007 @smallexample @c ada
31009 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31010 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31015 then the imported routine is @code{retrieve_val}, that is, there is no
31016 decoration at all. No leading underscore and no Stdcall suffix
31017 @code{@@}@code{@var{nn}}.
31020 This is especially important as in some special cases a DLL's entry
31021 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31022 name generated for a call has it.
31025 It is also possible to import variables defined in a DLL by using an
31026 import pragma for a variable. As an example, if a DLL contains a
31027 variable defined as:
31034 then, to access this variable from Ada you should write:
31036 @smallexample @c ada
31038 My_Var : Interfaces.C.int;
31039 pragma Import (Stdcall, My_Var);
31044 Note that to ease building cross-platform bindings this convention
31045 will be handled as a @code{C} calling convention on non-Windows platforms.
31047 @node Win32 Calling Convention
31048 @subsection @code{Win32} Calling Convention
31051 This convention, which is GNAT-specific is fully equivalent to the
31052 @code{Stdcall} calling convention described above.
31054 @node DLL Calling Convention
31055 @subsection @code{DLL} Calling Convention
31058 This convention, which is GNAT-specific is fully equivalent to the
31059 @code{Stdcall} calling convention described above.
31061 @node Introduction to Dynamic Link Libraries (DLLs)
31062 @section Introduction to Dynamic Link Libraries (DLLs)
31066 A Dynamically Linked Library (DLL) is a library that can be shared by
31067 several applications running under Windows. A DLL can contain any number of
31068 routines and variables.
31070 One advantage of DLLs is that you can change and enhance them without
31071 forcing all the applications that depend on them to be relinked or
31072 recompiled. However, you should be aware than all calls to DLL routines are
31073 slower since, as you will understand below, such calls are indirect.
31075 To illustrate the remainder of this section, suppose that an application
31076 wants to use the services of a DLL @file{API.dll}. To use the services
31077 provided by @file{API.dll} you must statically link against the DLL or
31078 an import library which contains a jump table with an entry for each
31079 routine and variable exported by the DLL. In the Microsoft world this
31080 import library is called @file{API.lib}. When using GNAT this import
31081 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31082 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31084 After you have linked your application with the DLL or the import library
31085 and you run your application, here is what happens:
31089 Your application is loaded into memory.
31092 The DLL @file{API.dll} is mapped into the address space of your
31093 application. This means that:
31097 The DLL will use the stack of the calling thread.
31100 The DLL will use the virtual address space of the calling process.
31103 The DLL will allocate memory from the virtual address space of the calling
31107 Handles (pointers) can be safely exchanged between routines in the DLL
31108 routines and routines in the application using the DLL.
31112 The entries in the jump table (from the import library @file{libAPI.dll.a}
31113 or @file{API.lib} or automatically created when linking against a DLL)
31114 which is part of your application are initialized with the addresses
31115 of the routines and variables in @file{API.dll}.
31118 If present in @file{API.dll}, routines @code{DllMain} or
31119 @code{DllMainCRTStartup} are invoked. These routines typically contain
31120 the initialization code needed for the well-being of the routines and
31121 variables exported by the DLL.
31125 There is an additional point which is worth mentioning. In the Windows
31126 world there are two kind of DLLs: relocatable and non-relocatable
31127 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31128 in the target application address space. If the addresses of two
31129 non-relocatable DLLs overlap and these happen to be used by the same
31130 application, a conflict will occur and the application will run
31131 incorrectly. Hence, when possible, it is always preferable to use and
31132 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31133 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31134 User's Guide) removes the debugging symbols from the DLL but the DLL can
31135 still be relocated.
31137 As a side note, an interesting difference between Microsoft DLLs and
31138 Unix shared libraries, is the fact that on most Unix systems all public
31139 routines are exported by default in a Unix shared library, while under
31140 Windows it is possible (but not required) to list exported routines in
31141 a definition file (@pxref{The Definition File}).
31143 @node Using DLLs with GNAT
31144 @section Using DLLs with GNAT
31147 * Creating an Ada Spec for the DLL Services::
31148 * Creating an Import Library::
31152 To use the services of a DLL, say @file{API.dll}, in your Ada application
31157 The Ada spec for the routines and/or variables you want to access in
31158 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31159 header files provided with the DLL.
31162 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31163 mentioned an import library is a statically linked library containing the
31164 import table which will be filled at load time to point to the actual
31165 @file{API.dll} routines. Sometimes you don't have an import library for the
31166 DLL you want to use. The following sections will explain how to build
31167 one. Note that this is optional.
31170 The actual DLL, @file{API.dll}.
31174 Once you have all the above, to compile an Ada application that uses the
31175 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31176 you simply issue the command
31179 $ gnatmake my_ada_app -largs -lAPI
31183 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31184 tells the GNAT linker to look first for a library named @file{API.lib}
31185 (Microsoft-style name) and if not found for a libraries named
31186 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31187 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31188 contains the following pragma
31190 @smallexample @c ada
31191 pragma Linker_Options ("-lAPI");
31195 you do not have to add @option{-largs -lAPI} at the end of the
31196 @command{gnatmake} command.
31198 If any one of the items above is missing you will have to create it
31199 yourself. The following sections explain how to do so using as an
31200 example a fictitious DLL called @file{API.dll}.
31202 @node Creating an Ada Spec for the DLL Services
31203 @subsection Creating an Ada Spec for the DLL Services
31206 A DLL typically comes with a C/C++ header file which provides the
31207 definitions of the routines and variables exported by the DLL. The Ada
31208 equivalent of this header file is a package spec that contains definitions
31209 for the imported entities. If the DLL you intend to use does not come with
31210 an Ada spec you have to generate one such spec yourself. For example if
31211 the header file of @file{API.dll} is a file @file{api.h} containing the
31212 following two definitions:
31224 then the equivalent Ada spec could be:
31226 @smallexample @c ada
31229 with Interfaces.C.Strings;
31234 function Get (Str : C.Strings.Chars_Ptr) return C.int;
31237 pragma Import (C, Get);
31238 pragma Import (DLL, Some_Var);
31245 Note that a variable is
31246 @strong{always imported with a Stdcall convention}. A function
31247 can have @code{C} or @code{Stdcall} convention.
31248 (@pxref{Windows Calling Conventions}).
31250 @node Creating an Import Library
31251 @subsection Creating an Import Library
31252 @cindex Import library
31255 * The Definition File::
31256 * GNAT-Style Import Library::
31257 * Microsoft-Style Import Library::
31261 If a Microsoft-style import library @file{API.lib} or a GNAT-style
31262 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
31263 with @file{API.dll} you can skip this section. You can also skip this
31264 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
31265 as in this case it is possible to link directly against the
31266 DLL. Otherwise read on.
31268 @node The Definition File
31269 @subsubsection The Definition File
31270 @cindex Definition file
31274 As previously mentioned, and unlike Unix systems, the list of symbols
31275 that are exported from a DLL must be provided explicitly in Windows.
31276 The main goal of a definition file is precisely that: list the symbols
31277 exported by a DLL. A definition file (usually a file with a @code{.def}
31278 suffix) has the following structure:
31283 @r{[}LIBRARY @var{name}@r{]}
31284 @r{[}DESCRIPTION @var{string}@r{]}
31294 @item LIBRARY @var{name}
31295 This section, which is optional, gives the name of the DLL.
31297 @item DESCRIPTION @var{string}
31298 This section, which is optional, gives a description string that will be
31299 embedded in the import library.
31302 This section gives the list of exported symbols (procedures, functions or
31303 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
31304 section of @file{API.def} looks like:
31318 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
31319 (@pxref{Windows Calling Conventions}) for a Stdcall
31320 calling convention function in the exported symbols list.
31323 There can actually be other sections in a definition file, but these
31324 sections are not relevant to the discussion at hand.
31326 @node GNAT-Style Import Library
31327 @subsubsection GNAT-Style Import Library
31330 To create a static import library from @file{API.dll} with the GNAT tools
31331 you should proceed as follows:
31335 Create the definition file @file{API.def} (@pxref{The Definition File}).
31336 For that use the @code{dll2def} tool as follows:
31339 $ dll2def API.dll > API.def
31343 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
31344 to standard output the list of entry points in the DLL. Note that if
31345 some routines in the DLL have the @code{Stdcall} convention
31346 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
31347 suffix then you'll have to edit @file{api.def} to add it, and specify
31348 @option{-k} to @command{gnatdll} when creating the import library.
31351 Here are some hints to find the right @code{@@}@var{nn} suffix.
31355 If you have the Microsoft import library (.lib), it is possible to get
31356 the right symbols by using Microsoft @code{dumpbin} tool (see the
31357 corresponding Microsoft documentation for further details).
31360 $ dumpbin /exports api.lib
31364 If you have a message about a missing symbol at link time the compiler
31365 tells you what symbol is expected. You just have to go back to the
31366 definition file and add the right suffix.
31370 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
31371 (@pxref{Using gnatdll}) as follows:
31374 $ gnatdll -e API.def -d API.dll
31378 @code{gnatdll} takes as input a definition file @file{API.def} and the
31379 name of the DLL containing the services listed in the definition file
31380 @file{API.dll}. The name of the static import library generated is
31381 computed from the name of the definition file as follows: if the
31382 definition file name is @var{xyz}@code{.def}, the import library name will
31383 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
31384 @option{-e} could have been removed because the name of the definition
31385 file (before the ``@code{.def}'' suffix) is the same as the name of the
31386 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
31389 @node Microsoft-Style Import Library
31390 @subsubsection Microsoft-Style Import Library
31393 With GNAT you can either use a GNAT-style or Microsoft-style import
31394 library. A Microsoft import library is needed only if you plan to make an
31395 Ada DLL available to applications developed with Microsoft
31396 tools (@pxref{Mixed-Language Programming on Windows}).
31398 To create a Microsoft-style import library for @file{API.dll} you
31399 should proceed as follows:
31403 Create the definition file @file{API.def} from the DLL. For this use either
31404 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
31405 tool (see the corresponding Microsoft documentation for further details).
31408 Build the actual import library using Microsoft's @code{lib} utility:
31411 $ lib -machine:IX86 -def:API.def -out:API.lib
31415 If you use the above command the definition file @file{API.def} must
31416 contain a line giving the name of the DLL:
31423 See the Microsoft documentation for further details about the usage of
31427 @node Building DLLs with GNAT
31428 @section Building DLLs with GNAT
31429 @cindex DLLs, building
31432 This section explain how to build DLLs using the GNAT built-in DLL
31433 support. With the following procedure it is straight forward to build
31434 and use DLLs with GNAT.
31438 @item building object files
31440 The first step is to build all objects files that are to be included
31441 into the DLL. This is done by using the standard @command{gnatmake} tool.
31443 @item building the DLL
31445 To build the DLL you must use @command{gcc}'s @option{-shared}
31446 option. It is quite simple to use this method:
31449 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
31452 It is important to note that in this case all symbols found in the
31453 object files are automatically exported. It is possible to restrict
31454 the set of symbols to export by passing to @command{gcc} a definition
31455 file, @pxref{The Definition File}. For example:
31458 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
31461 If you use a definition file you must export the elaboration procedures
31462 for every package that required one. Elaboration procedures are named
31463 using the package name followed by "_E".
31465 @item preparing DLL to be used
31467 For the DLL to be used by client programs the bodies must be hidden
31468 from it and the .ali set with read-only attribute. This is very important
31469 otherwise GNAT will recompile all packages and will not actually use
31470 the code in the DLL. For example:
31474 $ copy *.ads *.ali api.dll apilib
31475 $ attrib +R apilib\*.ali
31480 At this point it is possible to use the DLL by directly linking
31481 against it. Note that you must use the GNAT shared runtime when using
31482 GNAT shared libraries. This is achieved by using @option{-shared} binder's
31486 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
31489 @node Building DLLs with GNAT Project files
31490 @section Building DLLs with GNAT Project files
31491 @cindex DLLs, building
31494 There is nothing specific to Windows in the build process.
31495 @pxref{Library Projects}.
31498 Due to a system limitation, it is not possible under Windows to create threads
31499 when inside the @code{DllMain} routine which is used for auto-initialization
31500 of shared libraries, so it is not possible to have library level tasks in SALs.
31502 @node Building DLLs with gnatdll
31503 @section Building DLLs with gnatdll
31504 @cindex DLLs, building
31507 * Limitations When Using Ada DLLs from Ada::
31508 * Exporting Ada Entities::
31509 * Ada DLLs and Elaboration::
31510 * Ada DLLs and Finalization::
31511 * Creating a Spec for Ada DLLs::
31512 * Creating the Definition File::
31517 Note that it is preferred to use the built-in GNAT DLL support
31518 (@pxref{Building DLLs with GNAT}) or GNAT Project files
31519 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
31521 This section explains how to build DLLs containing Ada code using
31522 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
31523 remainder of this section.
31525 The steps required to build an Ada DLL that is to be used by Ada as well as
31526 non-Ada applications are as follows:
31530 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
31531 @code{Stdcall} calling convention to avoid any Ada name mangling for the
31532 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
31533 skip this step if you plan to use the Ada DLL only from Ada applications.
31536 Your Ada code must export an initialization routine which calls the routine
31537 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
31538 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
31539 routine exported by the Ada DLL must be invoked by the clients of the DLL
31540 to initialize the DLL.
31543 When useful, the DLL should also export a finalization routine which calls
31544 routine @code{adafinal} generated by @command{gnatbind} to perform the
31545 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
31546 The finalization routine exported by the Ada DLL must be invoked by the
31547 clients of the DLL when the DLL services are no further needed.
31550 You must provide a spec for the services exported by the Ada DLL in each
31551 of the programming languages to which you plan to make the DLL available.
31554 You must provide a definition file listing the exported entities
31555 (@pxref{The Definition File}).
31558 Finally you must use @code{gnatdll} to produce the DLL and the import
31559 library (@pxref{Using gnatdll}).
31563 Note that a relocatable DLL stripped using the @code{strip}
31564 binutils tool will not be relocatable anymore. To build a DLL without
31565 debug information pass @code{-largs -s} to @code{gnatdll}. This
31566 restriction does not apply to a DLL built using a Library Project.
31567 @pxref{Library Projects}.
31569 @node Limitations When Using Ada DLLs from Ada
31570 @subsection Limitations When Using Ada DLLs from Ada
31573 When using Ada DLLs from Ada applications there is a limitation users
31574 should be aware of. Because on Windows the GNAT run time is not in a DLL of
31575 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
31576 each Ada DLL includes the services of the GNAT run time that are necessary
31577 to the Ada code inside the DLL. As a result, when an Ada program uses an
31578 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
31579 one in the main program.
31581 It is therefore not possible to exchange GNAT run-time objects between the
31582 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
31583 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
31586 It is completely safe to exchange plain elementary, array or record types,
31587 Windows object handles, etc.
31589 @node Exporting Ada Entities
31590 @subsection Exporting Ada Entities
31591 @cindex Export table
31594 Building a DLL is a way to encapsulate a set of services usable from any
31595 application. As a result, the Ada entities exported by a DLL should be
31596 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
31597 any Ada name mangling. As an example here is an Ada package
31598 @code{API}, spec and body, exporting two procedures, a function, and a
31601 @smallexample @c ada
31604 with Interfaces.C; use Interfaces;
31606 Count : C.int := 0;
31607 function Factorial (Val : C.int) return C.int;
31609 procedure Initialize_API;
31610 procedure Finalize_API;
31611 -- Initialization & Finalization routines. More in the next section.
31613 pragma Export (C, Initialize_API);
31614 pragma Export (C, Finalize_API);
31615 pragma Export (C, Count);
31616 pragma Export (C, Factorial);
31622 @smallexample @c ada
31625 package body API is
31626 function Factorial (Val : C.int) return C.int is
31629 Count := Count + 1;
31630 for K in 1 .. Val loop
31636 procedure Initialize_API is
31638 pragma Import (C, Adainit);
31641 end Initialize_API;
31643 procedure Finalize_API is
31644 procedure Adafinal;
31645 pragma Import (C, Adafinal);
31655 If the Ada DLL you are building will only be used by Ada applications
31656 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
31657 convention. As an example, the previous package could be written as
31660 @smallexample @c ada
31664 Count : Integer := 0;
31665 function Factorial (Val : Integer) return Integer;
31667 procedure Initialize_API;
31668 procedure Finalize_API;
31669 -- Initialization and Finalization routines.
31675 @smallexample @c ada
31678 package body API is
31679 function Factorial (Val : Integer) return Integer is
31680 Fact : Integer := 1;
31682 Count := Count + 1;
31683 for K in 1 .. Val loop
31690 -- The remainder of this package body is unchanged.
31697 Note that if you do not export the Ada entities with a @code{C} or
31698 @code{Stdcall} convention you will have to provide the mangled Ada names
31699 in the definition file of the Ada DLL
31700 (@pxref{Creating the Definition File}).
31702 @node Ada DLLs and Elaboration
31703 @subsection Ada DLLs and Elaboration
31704 @cindex DLLs and elaboration
31707 The DLL that you are building contains your Ada code as well as all the
31708 routines in the Ada library that are needed by it. The first thing a
31709 user of your DLL must do is elaborate the Ada code
31710 (@pxref{Elaboration Order Handling in GNAT}).
31712 To achieve this you must export an initialization routine
31713 (@code{Initialize_API} in the previous example), which must be invoked
31714 before using any of the DLL services. This elaboration routine must call
31715 the Ada elaboration routine @code{adainit} generated by the GNAT binder
31716 (@pxref{Binding with Non-Ada Main Programs}). See the body of
31717 @code{Initialize_Api} for an example. Note that the GNAT binder is
31718 automatically invoked during the DLL build process by the @code{gnatdll}
31719 tool (@pxref{Using gnatdll}).
31721 When a DLL is loaded, Windows systematically invokes a routine called
31722 @code{DllMain}. It would therefore be possible to call @code{adainit}
31723 directly from @code{DllMain} without having to provide an explicit
31724 initialization routine. Unfortunately, it is not possible to call
31725 @code{adainit} from the @code{DllMain} if your program has library level
31726 tasks because access to the @code{DllMain} entry point is serialized by
31727 the system (that is, only a single thread can execute ``through'' it at a
31728 time), which means that the GNAT run time will deadlock waiting for the
31729 newly created task to complete its initialization.
31731 @node Ada DLLs and Finalization
31732 @subsection Ada DLLs and Finalization
31733 @cindex DLLs and finalization
31736 When the services of an Ada DLL are no longer needed, the client code should
31737 invoke the DLL finalization routine, if available. The DLL finalization
31738 routine is in charge of releasing all resources acquired by the DLL. In the
31739 case of the Ada code contained in the DLL, this is achieved by calling
31740 routine @code{adafinal} generated by the GNAT binder
31741 (@pxref{Binding with Non-Ada Main Programs}).
31742 See the body of @code{Finalize_Api} for an
31743 example. As already pointed out the GNAT binder is automatically invoked
31744 during the DLL build process by the @code{gnatdll} tool
31745 (@pxref{Using gnatdll}).
31747 @node Creating a Spec for Ada DLLs
31748 @subsection Creating a Spec for Ada DLLs
31751 To use the services exported by the Ada DLL from another programming
31752 language (e.g.@: C), you have to translate the specs of the exported Ada
31753 entities in that language. For instance in the case of @code{API.dll},
31754 the corresponding C header file could look like:
31759 extern int *_imp__count;
31760 #define count (*_imp__count)
31761 int factorial (int);
31767 It is important to understand that when building an Ada DLL to be used by
31768 other Ada applications, you need two different specs for the packages
31769 contained in the DLL: one for building the DLL and the other for using
31770 the DLL. This is because the @code{DLL} calling convention is needed to
31771 use a variable defined in a DLL, but when building the DLL, the variable
31772 must have either the @code{Ada} or @code{C} calling convention. As an
31773 example consider a DLL comprising the following package @code{API}:
31775 @smallexample @c ada
31779 Count : Integer := 0;
31781 -- Remainder of the package omitted.
31788 After producing a DLL containing package @code{API}, the spec that
31789 must be used to import @code{API.Count} from Ada code outside of the
31792 @smallexample @c ada
31797 pragma Import (DLL, Count);
31803 @node Creating the Definition File
31804 @subsection Creating the Definition File
31807 The definition file is the last file needed to build the DLL. It lists
31808 the exported symbols. As an example, the definition file for a DLL
31809 containing only package @code{API} (where all the entities are exported
31810 with a @code{C} calling convention) is:
31825 If the @code{C} calling convention is missing from package @code{API},
31826 then the definition file contains the mangled Ada names of the above
31827 entities, which in this case are:
31836 api__initialize_api
31841 @node Using gnatdll
31842 @subsection Using @code{gnatdll}
31846 * gnatdll Example::
31847 * gnatdll behind the Scenes::
31852 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
31853 and non-Ada sources that make up your DLL have been compiled.
31854 @code{gnatdll} is actually in charge of two distinct tasks: build the
31855 static import library for the DLL and the actual DLL. The form of the
31856 @code{gnatdll} command is
31860 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
31865 where @var{list-of-files} is a list of ALI and object files. The object
31866 file list must be the exact list of objects corresponding to the non-Ada
31867 sources whose services are to be included in the DLL. The ALI file list
31868 must be the exact list of ALI files for the corresponding Ada sources
31869 whose services are to be included in the DLL. If @var{list-of-files} is
31870 missing, only the static import library is generated.
31873 You may specify any of the following switches to @code{gnatdll}:
31876 @item -a@ovar{address}
31877 @cindex @option{-a} (@code{gnatdll})
31878 Build a non-relocatable DLL at @var{address}. If @var{address} is not
31879 specified the default address @var{0x11000000} will be used. By default,
31880 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
31881 advise the reader to build relocatable DLL.
31883 @item -b @var{address}
31884 @cindex @option{-b} (@code{gnatdll})
31885 Set the relocatable DLL base address. By default the address is
31888 @item -bargs @var{opts}
31889 @cindex @option{-bargs} (@code{gnatdll})
31890 Binder options. Pass @var{opts} to the binder.
31892 @item -d @var{dllfile}
31893 @cindex @option{-d} (@code{gnatdll})
31894 @var{dllfile} is the name of the DLL. This switch must be present for
31895 @code{gnatdll} to do anything. The name of the generated import library is
31896 obtained algorithmically from @var{dllfile} as shown in the following
31897 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
31898 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
31899 by option @option{-e}) is obtained algorithmically from @var{dllfile}
31900 as shown in the following example:
31901 if @var{dllfile} is @code{xyz.dll}, the definition
31902 file used is @code{xyz.def}.
31904 @item -e @var{deffile}
31905 @cindex @option{-e} (@code{gnatdll})
31906 @var{deffile} is the name of the definition file.
31909 @cindex @option{-g} (@code{gnatdll})
31910 Generate debugging information. This information is stored in the object
31911 file and copied from there to the final DLL file by the linker,
31912 where it can be read by the debugger. You must use the
31913 @option{-g} switch if you plan on using the debugger or the symbolic
31917 @cindex @option{-h} (@code{gnatdll})
31918 Help mode. Displays @code{gnatdll} switch usage information.
31921 @cindex @option{-I} (@code{gnatdll})
31922 Direct @code{gnatdll} to search the @var{dir} directory for source and
31923 object files needed to build the DLL.
31924 (@pxref{Search Paths and the Run-Time Library (RTL)}).
31927 @cindex @option{-k} (@code{gnatdll})
31928 Removes the @code{@@}@var{nn} suffix from the import library's exported
31929 names, but keeps them for the link names. You must specify this
31930 option if you want to use a @code{Stdcall} function in a DLL for which
31931 the @code{@@}@var{nn} suffix has been removed. This is the case for most
31932 of the Windows NT DLL for example. This option has no effect when
31933 @option{-n} option is specified.
31935 @item -l @var{file}
31936 @cindex @option{-l} (@code{gnatdll})
31937 The list of ALI and object files used to build the DLL are listed in
31938 @var{file}, instead of being given in the command line. Each line in
31939 @var{file} contains the name of an ALI or object file.
31942 @cindex @option{-n} (@code{gnatdll})
31943 No Import. Do not create the import library.
31946 @cindex @option{-q} (@code{gnatdll})
31947 Quiet mode. Do not display unnecessary messages.
31950 @cindex @option{-v} (@code{gnatdll})
31951 Verbose mode. Display extra information.
31953 @item -largs @var{opts}
31954 @cindex @option{-largs} (@code{gnatdll})
31955 Linker options. Pass @var{opts} to the linker.
31958 @node gnatdll Example
31959 @subsubsection @code{gnatdll} Example
31962 As an example the command to build a relocatable DLL from @file{api.adb}
31963 once @file{api.adb} has been compiled and @file{api.def} created is
31966 $ gnatdll -d api.dll api.ali
31970 The above command creates two files: @file{libapi.dll.a} (the import
31971 library) and @file{api.dll} (the actual DLL). If you want to create
31972 only the DLL, just type:
31975 $ gnatdll -d api.dll -n api.ali
31979 Alternatively if you want to create just the import library, type:
31982 $ gnatdll -d api.dll
31985 @node gnatdll behind the Scenes
31986 @subsubsection @code{gnatdll} behind the Scenes
31989 This section details the steps involved in creating a DLL. @code{gnatdll}
31990 does these steps for you. Unless you are interested in understanding what
31991 goes on behind the scenes, you should skip this section.
31993 We use the previous example of a DLL containing the Ada package @code{API},
31994 to illustrate the steps necessary to build a DLL. The starting point is a
31995 set of objects that will make up the DLL and the corresponding ALI
31996 files. In the case of this example this means that @file{api.o} and
31997 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32002 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32003 the information necessary to generate relocation information for the
32009 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32014 In addition to the base file, the @command{gnatlink} command generates an
32015 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32016 asks @command{gnatlink} to generate the routines @code{DllMain} and
32017 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32018 is loaded into memory.
32021 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32022 export table (@file{api.exp}). The export table contains the relocation
32023 information in a form which can be used during the final link to ensure
32024 that the Windows loader is able to place the DLL anywhere in memory.
32028 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32029 --output-exp api.exp
32034 @code{gnatdll} builds the base file using the new export table. Note that
32035 @command{gnatbind} must be called once again since the binder generated file
32036 has been deleted during the previous call to @command{gnatlink}.
32041 $ gnatlink api -o api.jnk api.exp -mdll
32042 -Wl,--base-file,api.base
32047 @code{gnatdll} builds the new export table using the new base file and
32048 generates the DLL import library @file{libAPI.dll.a}.
32052 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32053 --output-exp api.exp --output-lib libAPI.a
32058 Finally @code{gnatdll} builds the relocatable DLL using the final export
32064 $ gnatlink api api.exp -o api.dll -mdll
32069 @node Using dlltool
32070 @subsubsection Using @code{dlltool}
32073 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32074 DLLs and static import libraries. This section summarizes the most
32075 common @code{dlltool} switches. The form of the @code{dlltool} command
32079 $ dlltool @ovar{switches}
32083 @code{dlltool} switches include:
32086 @item --base-file @var{basefile}
32087 @cindex @option{--base-file} (@command{dlltool})
32088 Read the base file @var{basefile} generated by the linker. This switch
32089 is used to create a relocatable DLL.
32091 @item --def @var{deffile}
32092 @cindex @option{--def} (@command{dlltool})
32093 Read the definition file.
32095 @item --dllname @var{name}
32096 @cindex @option{--dllname} (@command{dlltool})
32097 Gives the name of the DLL. This switch is used to embed the name of the
32098 DLL in the static import library generated by @code{dlltool} with switch
32099 @option{--output-lib}.
32102 @cindex @option{-k} (@command{dlltool})
32103 Kill @code{@@}@var{nn} from exported names
32104 (@pxref{Windows Calling Conventions}
32105 for a discussion about @code{Stdcall}-style symbols.
32108 @cindex @option{--help} (@command{dlltool})
32109 Prints the @code{dlltool} switches with a concise description.
32111 @item --output-exp @var{exportfile}
32112 @cindex @option{--output-exp} (@command{dlltool})
32113 Generate an export file @var{exportfile}. The export file contains the
32114 export table (list of symbols in the DLL) and is used to create the DLL.
32116 @item --output-lib @var{libfile}
32117 @cindex @option{--output-lib} (@command{dlltool})
32118 Generate a static import library @var{libfile}.
32121 @cindex @option{-v} (@command{dlltool})
32124 @item --as @var{assembler-name}
32125 @cindex @option{--as} (@command{dlltool})
32126 Use @var{assembler-name} as the assembler. The default is @code{as}.
32129 @node GNAT and Windows Resources
32130 @section GNAT and Windows Resources
32131 @cindex Resources, windows
32134 * Building Resources::
32135 * Compiling Resources::
32136 * Using Resources::
32140 Resources are an easy way to add Windows specific objects to your
32141 application. The objects that can be added as resources include:
32170 This section explains how to build, compile and use resources.
32172 @node Building Resources
32173 @subsection Building Resources
32174 @cindex Resources, building
32177 A resource file is an ASCII file. By convention resource files have an
32178 @file{.rc} extension.
32179 The easiest way to build a resource file is to use Microsoft tools
32180 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32181 @code{dlgedit.exe} to build dialogs.
32182 It is always possible to build an @file{.rc} file yourself by writing a
32185 It is not our objective to explain how to write a resource file. A
32186 complete description of the resource script language can be found in the
32187 Microsoft documentation.
32189 @node Compiling Resources
32190 @subsection Compiling Resources
32193 @cindex Resources, compiling
32196 This section describes how to build a GNAT-compatible (COFF) object file
32197 containing the resources. This is done using the Resource Compiler
32198 @code{windres} as follows:
32201 $ windres -i myres.rc -o myres.o
32205 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32206 file. You can specify an alternate preprocessor (usually named
32207 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32208 parameter. A list of all possible options may be obtained by entering
32209 the command @code{windres} @option{--help}.
32211 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32212 to produce a @file{.res} file (binary resource file). See the
32213 corresponding Microsoft documentation for further details. In this case
32214 you need to use @code{windres} to translate the @file{.res} file to a
32215 GNAT-compatible object file as follows:
32218 $ windres -i myres.res -o myres.o
32221 @node Using Resources
32222 @subsection Using Resources
32223 @cindex Resources, using
32226 To include the resource file in your program just add the
32227 GNAT-compatible object file for the resource(s) to the linker
32228 arguments. With @command{gnatmake} this is done by using the @option{-largs}
32232 $ gnatmake myprog -largs myres.o
32235 @node Debugging a DLL
32236 @section Debugging a DLL
32237 @cindex DLL debugging
32240 * Program and DLL Both Built with GCC/GNAT::
32241 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
32245 Debugging a DLL is similar to debugging a standard program. But
32246 we have to deal with two different executable parts: the DLL and the
32247 program that uses it. We have the following four possibilities:
32251 The program and the DLL are built with @code{GCC/GNAT}.
32253 The program is built with foreign tools and the DLL is built with
32256 The program is built with @code{GCC/GNAT} and the DLL is built with
32262 In this section we address only cases one and two above.
32263 There is no point in trying to debug
32264 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
32265 information in it. To do so you must use a debugger compatible with the
32266 tools suite used to build the DLL.
32268 @node Program and DLL Both Built with GCC/GNAT
32269 @subsection Program and DLL Both Built with GCC/GNAT
32272 This is the simplest case. Both the DLL and the program have @code{GDB}
32273 compatible debugging information. It is then possible to break anywhere in
32274 the process. Let's suppose here that the main procedure is named
32275 @code{ada_main} and that in the DLL there is an entry point named
32279 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
32280 program must have been built with the debugging information (see GNAT -g
32281 switch). Here are the step-by-step instructions for debugging it:
32284 @item Launch @code{GDB} on the main program.
32290 @item Start the program and stop at the beginning of the main procedure
32297 This step is required to be able to set a breakpoint inside the DLL. As long
32298 as the program is not run, the DLL is not loaded. This has the
32299 consequence that the DLL debugging information is also not loaded, so it is not
32300 possible to set a breakpoint in the DLL.
32302 @item Set a breakpoint inside the DLL
32305 (gdb) break ada_dll
32312 At this stage a breakpoint is set inside the DLL. From there on
32313 you can use the standard approach to debug the whole program
32314 (@pxref{Running and Debugging Ada Programs}).
32317 @c This used to work, probably because the DLLs were non-relocatable
32318 @c keep this section around until the problem is sorted out.
32320 To break on the @code{DllMain} routine it is not possible to follow
32321 the procedure above. At the time the program stop on @code{ada_main}
32322 the @code{DllMain} routine as already been called. Either you can use
32323 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
32326 @item Launch @code{GDB} on the main program.
32332 @item Load DLL symbols
32335 (gdb) add-sym api.dll
32338 @item Set a breakpoint inside the DLL
32341 (gdb) break ada_dll.adb:45
32344 Note that at this point it is not possible to break using the routine symbol
32345 directly as the program is not yet running. The solution is to break
32346 on the proper line (break in @file{ada_dll.adb} line 45).
32348 @item Start the program
32357 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
32358 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
32361 * Debugging the DLL Directly::
32362 * Attaching to a Running Process::
32366 In this case things are slightly more complex because it is not possible to
32367 start the main program and then break at the beginning to load the DLL and the
32368 associated DLL debugging information. It is not possible to break at the
32369 beginning of the program because there is no @code{GDB} debugging information,
32370 and therefore there is no direct way of getting initial control. This
32371 section addresses this issue by describing some methods that can be used
32372 to break somewhere in the DLL to debug it.
32375 First suppose that the main procedure is named @code{main} (this is for
32376 example some C code built with Microsoft Visual C) and that there is a
32377 DLL named @code{test.dll} containing an Ada entry point named
32381 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
32382 been built with debugging information (see GNAT -g option).
32384 @node Debugging the DLL Directly
32385 @subsubsection Debugging the DLL Directly
32389 Find out the executable starting address
32392 $ objdump --file-header main.exe
32395 The starting address is reported on the last line. For example:
32398 main.exe: file format pei-i386
32399 architecture: i386, flags 0x0000010a:
32400 EXEC_P, HAS_DEBUG, D_PAGED
32401 start address 0x00401010
32405 Launch the debugger on the executable.
32412 Set a breakpoint at the starting address, and launch the program.
32415 $ (gdb) break *0x00401010
32419 The program will stop at the given address.
32422 Set a breakpoint on a DLL subroutine.
32425 (gdb) break ada_dll.adb:45
32428 Or if you want to break using a symbol on the DLL, you need first to
32429 select the Ada language (language used by the DLL).
32432 (gdb) set language ada
32433 (gdb) break ada_dll
32437 Continue the program.
32444 This will run the program until it reaches the breakpoint that has been
32445 set. From that point you can use the standard way to debug a program
32446 as described in (@pxref{Running and Debugging Ada Programs}).
32451 It is also possible to debug the DLL by attaching to a running process.
32453 @node Attaching to a Running Process
32454 @subsubsection Attaching to a Running Process
32455 @cindex DLL debugging, attach to process
32458 With @code{GDB} it is always possible to debug a running process by
32459 attaching to it. It is possible to debug a DLL this way. The limitation
32460 of this approach is that the DLL must run long enough to perform the
32461 attach operation. It may be useful for instance to insert a time wasting
32462 loop in the code of the DLL to meet this criterion.
32466 @item Launch the main program @file{main.exe}.
32472 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
32473 that the process PID for @file{main.exe} is 208.
32481 @item Attach to the running process to be debugged.
32487 @item Load the process debugging information.
32490 (gdb) symbol-file main.exe
32493 @item Break somewhere in the DLL.
32496 (gdb) break ada_dll
32499 @item Continue process execution.
32508 This last step will resume the process execution, and stop at
32509 the breakpoint we have set. From there you can use the standard
32510 approach to debug a program as described in
32511 (@pxref{Running and Debugging Ada Programs}).
32513 @node Setting Stack Size from gnatlink
32514 @section Setting Stack Size from @command{gnatlink}
32517 It is possible to specify the program stack size at link time. On modern
32518 versions of Windows, starting with XP, this is mostly useful to set the size of
32519 the main stack (environment task). The other task stacks are set with pragma
32520 Storage_Size or with the @command{gnatbind -d} command.
32522 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
32523 reserve size of individual tasks, the link-time stack size applies to all
32524 tasks, and pragma Storage_Size has no effect.
32525 In particular, Stack Overflow checks are made against this
32526 link-time specified size.
32528 This setting can be done with
32529 @command{gnatlink} using either:
32533 @item using @option{-Xlinker} linker option
32536 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
32539 This sets the stack reserve size to 0x10000 bytes and the stack commit
32540 size to 0x1000 bytes.
32542 @item using @option{-Wl} linker option
32545 $ gnatlink hello -Wl,--stack=0x1000000
32548 This sets the stack reserve size to 0x1000000 bytes. Note that with
32549 @option{-Wl} option it is not possible to set the stack commit size
32550 because the coma is a separator for this option.
32554 @node Setting Heap Size from gnatlink
32555 @section Setting Heap Size from @command{gnatlink}
32558 Under Windows systems, it is possible to specify the program heap size from
32559 @command{gnatlink} using either:
32563 @item using @option{-Xlinker} linker option
32566 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
32569 This sets the heap reserve size to 0x10000 bytes and the heap commit
32570 size to 0x1000 bytes.
32572 @item using @option{-Wl} linker option
32575 $ gnatlink hello -Wl,--heap=0x1000000
32578 This sets the heap reserve size to 0x1000000 bytes. Note that with
32579 @option{-Wl} option it is not possible to set the heap commit size
32580 because the coma is a separator for this option.
32586 @c **********************************
32587 @c * GNU Free Documentation License *
32588 @c **********************************
32590 @c GNU Free Documentation License
32592 @node Index,,GNU Free Documentation License, Top
32598 @c Put table of contents at end, otherwise it precedes the "title page" in
32599 @c the .txt version
32600 @c Edit the pdf file to move the contents to the beginning, after the title