1 \input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c Copyright (C) 1992-2004 Ada Core Technologies, Inc. o
12 @c GNAT is free software; you can redistribute it and/or modify it under o
13 @c terms of the GNU General Public License as published by the Free Soft- o
14 @c ware Foundation; either version 2, or (at your option) any later ver- o
15 @c sion. GNAT is distributed in the hope that it will be useful, but WITH- o
16 @c OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY o
17 @c or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License o
18 @c for more details. You should have received a copy of the GNU General o
19 @c Public License distributed with GNAT; see file COPYING. If not, write o
20 @c to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, o
21 @c MA 02111-1307, USA. o
23 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
25 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
27 @c GNAT_UGN Style Guide
29 @c 1. Always put a @noindent on the line before the first paragraph
30 @c after any of these commands:
42 @c 2. DO NOT use @example. Use @smallexample instead.
43 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
44 @c context. These can interfere with the readability of the texi
45 @c source file. Instead, use one of the following annotated
46 @c @smallexample commands, and preprocess the texi file with the
47 @c ada2texi tool (which generates appropriate highlighting):
48 @c @smallexample @c ada
49 @c @smallexample @c adanocomment
50 @c @smallexample @c projectfile
51 @c b) The "@c ada" markup will result in boldface for reserved words
52 @c and italics for comments
53 @c c) The "@c adanocomment" markup will result only in boldface for
54 @c reserved words (comments are left alone)
55 @c d) The "@c projectfile" markup is like "@c ada" except that the set
56 @c of reserved words include the new reserved words for project files
58 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
59 @c command must be preceded by two empty lines
61 @c 4. The @item command should be on a line of its own if it is in an
62 @c @itemize or @enumerate command.
64 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
67 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
68 @c cause the document build to fail.
70 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
71 @c This command inhibits page breaks, so long examples in a @cartouche can
72 @c lead to large, ugly patches of empty space on a page.
74 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
75 @c or the unw flag set. The unw flag covers topics for both Unix and
78 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
81 @setfilename gnat_ugn_vms.info
85 @setfilename gnat_ugn_unw.info
92 @set PLATFORM Unix and Windows
93 @set FILE gnat_ugn_unw
97 @set PLATFORM OpenVMS Alpha
98 @set FILE gnat_ugn_vms
103 @settitle @value{EDITION} User's Guide for Native Platforms / @value{PLATFORM}
104 @dircategory GNU Ada tools
106 * @value{EDITION} User's Guide (@value{FILE}) for Native Platforms / @value{PLATFORM}
109 @include gcc-common.texi
111 @setchapternewpage odd
116 Copyright @copyright{} 1995-2004, Free Software Foundation
118 Permission is granted to copy, distribute and/or modify this document
119 under the terms of the GNU Free Documentation License, Version 1.2
120 or any later version published by the Free Software Foundation;
121 with the Invariant Sections being ``GNU Free Documentation License'', with the
122 Front-Cover Texts being
123 ``GNAT User's Guide for Native Platforms / @value{PLATFORM}'',
124 and with no Back-Cover Texts.
125 A copy of the license is included in the section entitled
126 ``GNU Free Documentation License''.
131 @title @value{EDITION} User's Guide
132 @center @titlefont{for Native Platforms}
136 @titlefont{@i{@value{PLATFORM}}}
140 @subtitle GNAT, The GNU Ada 95 Compiler
141 @subtitle GCC version @value{version-GCC}
143 @author Ada Core Technologies, Inc.
146 @vskip 0pt plus 1filll
154 @node Top, About This Guide, (dir), (dir)
155 @top @value{EDITION} User's Guide
158 @value{EDITION} User's Guide for Native Platforms / @value{PLATFORM}
161 GNAT, The GNU Ada 95 Compiler@*
162 GCC version @value{version-GCC}@*
165 Ada Core Technologies, Inc.@*
169 * Getting Started with GNAT::
170 * The GNAT Compilation Model::
171 * Compiling Using gcc::
172 * Binding Using gnatbind::
173 * Linking Using gnatlink::
174 * The GNAT Make Program gnatmake::
175 * Improving Performance::
176 * Renaming Files Using gnatchop::
177 * Configuration Pragmas::
178 * Handling Arbitrary File Naming Conventions Using gnatname::
179 * GNAT Project Manager::
180 * The Cross-Referencing Tools gnatxref and gnatfind::
181 * The GNAT Pretty-Printer gnatpp::
182 * File Name Krunching Using gnatkr::
183 * Preprocessing Using gnatprep::
185 * The GNAT Run-Time Library Builder gnatlbr::
187 * The GNAT Library Browser gnatls::
188 * Cleaning Up Using gnatclean::
190 * GNAT and Libraries::
191 * Using the GNU make Utility::
193 * Finding Memory Problems::
194 * Creating Sample Bodies Using gnatstub::
195 * Other Utility Programs::
196 * Running and Debugging Ada Programs::
198 * Compatibility with DEC Ada::
200 * Platform-Specific Information for the Run-Time Libraries::
201 * Example of Binder Output File::
202 * Elaboration Order Handling in GNAT::
204 * Compatibility and Porting Guide::
206 * Microsoft Windows Topics::
208 * GNU Free Documentation License::
211 --- The Detailed Node Listing ---
215 * What This Guide Contains::
216 * What You Should Know before Reading This Guide::
217 * Related Information::
220 Getting Started with GNAT
223 * Running a Simple Ada Program::
224 * Running a Program with Multiple Units::
225 * Using the gnatmake Utility::
227 * Editing with Emacs::
230 * Introduction to GPS::
231 * Introduction to Glide and GVD::
234 The GNAT Compilation Model
236 * Source Representation::
237 * Foreign Language Representation::
238 * File Naming Rules::
239 * Using Other File Names::
240 * Alternative File Naming Schemes::
241 * Generating Object Files::
242 * Source Dependencies::
243 * The Ada Library Information Files::
244 * Binding an Ada Program::
245 * Mixed Language Programming::
246 * Building Mixed Ada & C++ Programs::
247 * 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 * Stack Overflow Checking::
276 * Using gcc for Syntax Checking::
277 * Using gcc for Semantic Checking::
278 * Compiling Ada 83 Programs::
279 * Character Set Control::
280 * File Naming Control::
281 * Subprogram Inlining Control::
282 * Auxiliary Output Control::
283 * Debugging Control::
284 * Exception Handling Control::
285 * Units to Sources Mapping Files::
286 * Integrated Preprocessing::
291 Binding Ada Programs With gnatbind
294 * Switches for gnatbind::
295 * Command-Line Access::
296 * Search Paths for gnatbind::
297 * Examples of gnatbind Usage::
299 Switches for gnatbind
301 * Consistency-Checking Modes::
302 * Binder Error Message Control::
303 * Elaboration Control::
305 * Binding with Non-Ada Main Programs::
306 * Binding Programs with No Main Subprogram::
308 Linking Using gnatlink
311 * Switches for gnatlink::
312 * Setting Stack Size from gnatlink::
313 * Setting Heap Size from gnatlink::
315 The GNAT Make Program gnatmake
318 * Switches for gnatmake::
319 * Mode Switches for gnatmake::
320 * Notes on the Command Line::
321 * How gnatmake Works::
322 * Examples of gnatmake Usage::
325 Improving Performance
326 * Performance Considerations::
327 * Reducing the Size of Ada Executables with gnatelim::
329 Performance Considerations
330 * Controlling Run-Time Checks::
331 * Use of Restrictions::
332 * Optimization Levels::
333 * Debugging Optimized Code::
334 * Inlining of Subprograms::
335 * Optimization and Strict Aliasing::
337 * Coverage Analysis::
340 Reducing the Size of Ada Executables with gnatelim
343 * Correcting the List of Eliminate Pragmas::
344 * Making Your Executables Smaller::
345 * Summary of the gnatelim Usage Cycle::
347 Renaming Files Using gnatchop
349 * Handling Files with Multiple Units::
350 * Operating gnatchop in Compilation Mode::
351 * Command Line for gnatchop::
352 * Switches for gnatchop::
353 * Examples of gnatchop Usage::
355 Configuration Pragmas
357 * Handling of Configuration Pragmas::
358 * The Configuration Pragmas Files::
360 Handling Arbitrary File Naming Conventions Using gnatname
362 * Arbitrary File Naming Conventions::
364 * Switches for gnatname::
365 * Examples of gnatname Usage::
370 * Examples of Project Files::
371 * Project File Syntax::
372 * Objects and Sources in Project Files::
373 * Importing Projects::
374 * Project Extension::
375 * External References in Project Files::
376 * Packages in Project Files::
377 * Variables from Imported Projects::
380 * Using Third-Party Libraries through Projects::
381 * Stand-alone Library Projects::
382 * Switches Related to Project Files::
383 * Tools Supporting Project Files::
384 * An Extended Example::
385 * Project File Complete Syntax::
388 The Cross-Referencing Tools gnatxref and gnatfind
390 * gnatxref Switches::
391 * gnatfind Switches::
392 * Project Files for gnatxref and gnatfind::
393 * Regular Expressions in gnatfind and gnatxref::
394 * Examples of gnatxref Usage::
395 * Examples of gnatfind Usage::
398 The GNAT Pretty-Printer gnatpp
400 * Switches for gnatpp::
404 File Name Krunching Using gnatkr
409 * Examples of gnatkr Usage::
411 Preprocessing Using gnatprep
414 * Switches for gnatprep::
415 * Form of Definitions File::
416 * Form of Input Text for gnatprep::
419 The GNAT Run-Time Library Builder gnatlbr
422 * Switches for gnatlbr::
423 * Examples of gnatlbr Usage::
426 The GNAT Library Browser gnatls
429 * Switches for gnatls::
430 * Examples of gnatls Usage::
432 Cleaning Up Using gnatclean
434 * Running gnatclean::
435 * Switches for gnatclean::
436 * Examples of gnatclean Usage::
442 * Introduction to Libraries in GNAT::
443 * General Ada Libraries::
444 * Stand-alone Ada Libraries::
445 * Rebuilding the GNAT Run-Time Library::
447 Using the GNU make Utility
449 * Using gnatmake in a Makefile::
450 * Automatically Creating a List of Directories::
451 * Generating the Command Line Switches::
452 * Overcoming Command Line Length Limits::
455 Finding Memory Problems
460 * The GNAT Debug Pool Facility::
466 * Switches for gnatmem::
467 * Example of gnatmem Usage::
470 The GNAT Debug Pool Facility
472 Creating Sample Bodies Using gnatstub
475 * Switches for gnatstub::
477 Other Utility Programs
479 * Using Other Utility Programs with GNAT::
480 * The External Symbol Naming Scheme of GNAT::
482 * Ada Mode for Glide::
484 * Converting Ada Files to html with gnathtml::
486 Running and Debugging Ada Programs
488 * The GNAT Debugger GDB::
490 * Introduction to GDB Commands::
491 * Using Ada Expressions::
492 * Calling User-Defined Subprograms::
493 * Using the Next Command in a Function::
496 * Debugging Generic Units::
497 * GNAT Abnormal Termination or Failure to Terminate::
498 * Naming Conventions for GNAT Source Files::
499 * Getting Internal Debugging Information::
507 Compatibility with DEC Ada
509 * Ada 95 Compatibility::
510 * Differences in the Definition of Package System::
511 * Language-Related Features::
512 * The Package STANDARD::
513 * The Package SYSTEM::
514 * Tasking and Task-Related Features::
515 * Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
516 * Pragmas and Pragma-Related Features::
517 * Library of Predefined Units::
519 * Main Program Definition::
520 * Implementation-Defined Attributes::
521 * Compiler and Run-Time Interfacing::
522 * Program Compilation and Library Management::
524 * Implementation Limits::
527 Language-Related Features
529 * Integer Types and Representations::
530 * Floating-Point Types and Representations::
531 * Pragmas Float_Representation and Long_Float::
532 * Fixed-Point Types and Representations::
533 * Record and Array Component Alignment::
535 * Other Representation Clauses::
537 Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
539 * Assigning Task IDs::
540 * Task IDs and Delays::
541 * Task-Related Pragmas::
542 * Scheduling and Task Priority::
544 * External Interrupts::
546 Pragmas and Pragma-Related Features
548 * Restrictions on the Pragma INLINE::
549 * Restrictions on the Pragma INTERFACE::
550 * Restrictions on the Pragma SYSTEM_NAME::
552 Library of Predefined Units
554 * Changes to DECLIB::
558 * Shared Libraries and Options Files::
562 Platform-Specific Information for the Run-Time Libraries
564 * Summary of Run-Time Configurations::
565 * Specifying a Run-Time Library::
566 * Choosing between Native and FSU Threads Libraries::
567 * Choosing the Scheduling Policy::
568 * Solaris-Specific Considerations::
569 * IRIX-Specific Considerations::
570 * Linux-Specific Considerations::
571 * AIX-Specific Considerations::
573 Example of Binder Output File
575 Elaboration Order Handling in GNAT
577 * Elaboration Code in Ada 95::
578 * Checking the Elaboration Order in Ada 95::
579 * Controlling the Elaboration Order in Ada 95::
580 * Controlling Elaboration in GNAT - Internal Calls::
581 * Controlling Elaboration in GNAT - External Calls::
582 * Default Behavior in GNAT - Ensuring Safety::
583 * Treatment of Pragma Elaborate::
584 * Elaboration Issues for Library Tasks::
585 * Mixing Elaboration Models::
586 * What to Do If the Default Elaboration Behavior Fails::
587 * Elaboration for Access-to-Subprogram Values::
588 * Summary of Procedures for Elaboration Control::
589 * Other Elaboration Order Considerations::
593 * Basic Assembler Syntax::
594 * A Simple Example of Inline Assembler::
595 * Output Variables in Inline Assembler::
596 * Input Variables in Inline Assembler::
597 * Inlining Inline Assembler Code::
598 * Other Asm Functionality::
599 * A Complete Example::
601 Compatibility and Porting Guide
603 * Compatibility with Ada 83::
604 * Implementation-dependent characteristics::
605 * Compatibility with DEC Ada 83::
606 * Compatibility with Other Ada 95 Systems::
607 * Representation Clauses::
610 Microsoft Windows Topics
612 * Using GNAT on Windows::
613 * CONSOLE and WINDOWS subsystems::
615 * Mixed-Language Programming on Windows::
616 * Windows Calling Conventions::
617 * Introduction to Dynamic Link Libraries (DLLs)::
618 * Using DLLs with GNAT::
619 * Building DLLs with GNAT::
620 * GNAT and Windows Resources::
622 * GNAT and COM/DCOM Objects::
630 @node About This Guide
631 @unnumbered About This Guide
635 This guide describes the use of of @value{EDITION},
636 a full language compiler for the Ada
637 95 programming language, implemented on HP OpenVMS Alpha platforms.
640 This guide describes the use of @value{EDITION},
641 a compiler and software development
642 toolset for the full Ada 95 programming language.
644 It describes the features of the compiler and tools, and details
645 how to use them to build Ada 95 applications.
648 For ease of exposition, ``GNAT Pro'' will be referred to simply as
649 ``GNAT'' in the remainder of this document.
655 * What This Guide Contains::
656 * What You Should Know before Reading This Guide::
657 * Related Information::
661 @node What This Guide Contains
662 @unnumberedsec What This Guide Contains
665 This guide contains the following chapters:
669 @ref{Getting Started with GNAT}, describes how to get started compiling
670 and running Ada programs with the GNAT Ada programming environment.
672 @ref{The GNAT Compilation Model}, describes the compilation model used
676 @ref{Compiling Using gcc}, describes how to compile
677 Ada programs with @code{gcc}, the Ada compiler.
680 @ref{Binding Using gnatbind}, describes how to
681 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
685 @ref{Linking Using gnatlink},
686 describes @code{gnatlink}, a
687 program that provides for linking using the GNAT run-time library to
688 construct a program. @code{gnatlink} can also incorporate foreign language
689 object units into the executable.
692 @ref{The GNAT Make Program gnatmake}, describes @code{gnatmake}, a
693 utility that automatically determines the set of sources
694 needed by an Ada compilation unit, and executes the necessary compilations
698 @ref{Improving Performance}, shows various techniques for making your
699 Ada program run faster or take less space.
700 It discusses the effect of the compiler's optimization switch and
701 also describes the @command{gnatelim} tool.
704 @ref{Renaming Files Using gnatchop}, describes
705 @code{gnatchop}, a utility that allows you to preprocess a file that
706 contains Ada source code, and split it into one or more new files, one
707 for each compilation unit.
710 @ref{Configuration Pragmas}, describes the configuration pragmas
714 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
715 shows how to override the default GNAT file naming conventions,
716 either for an individual unit or globally.
719 @ref{GNAT Project Manager}, describes how to use project files
720 to organize large projects.
723 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
724 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
725 way to navigate through sources.
728 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
729 version of an Ada source file with control over casing, indentation,
730 comment placement, and other elements of program presentation style.
734 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
735 file name krunching utility, used to handle shortened
736 file names on operating systems with a limit on the length of names.
739 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
740 preprocessor utility that allows a single source file to be used to
741 generate multiple or parameterized source files, by means of macro
746 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
747 a tool for rebuilding the GNAT run time with user-supplied
748 configuration pragmas.
752 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
753 utility that displays information about compiled units, including dependences
754 on the corresponding sources files, and consistency of compilations.
757 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
758 to delete files that are produced by the compiler, binder and linker.
762 @ref{GNAT and Libraries}, describes the process of creating and using
763 Libraries with GNAT. It also describes how to recompile the GNAT run-time
767 @ref{Using the GNU make Utility}, describes some techniques for using
768 the GNAT toolset in Makefiles.
772 @ref{Finding Memory Problems}, describes
774 @command{gnatmem}, a utility that monitors dynamic allocation and deallocation
775 and helps detect ``memory leaks'', and
777 the GNAT Debug Pool facility, which helps detect incorrect memory references.
780 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
781 a utility that generates empty but compilable bodies for library units.
784 @ref{Other Utility Programs}, discusses several other GNAT utilities,
785 including @code{gnathtml}.
788 @ref{Running and Debugging Ada Programs}, describes how to run and debug
793 @ref{Compatibility with DEC Ada}, details the compatibility of GNAT with
794 DEC Ada 83 @footnote{``DEC Ada'' refers to the legacy product originally
795 developed by Digital Equipment Corporation and currently supported by HP.}
800 @ref{Platform-Specific Information for the Run-Time Libraries},
801 describes the various run-time
802 libraries supported by GNAT on various platforms and explains how to
803 choose a particular library.
806 @ref{Example of Binder Output File}, shows the source code for the binder
807 output file for a sample program.
810 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
811 you deal with elaboration order issues.
814 @ref{Inline Assembler}, shows how to use the inline assembly facility
818 @ref{Compatibility and Porting Guide}, includes sections on compatibility
819 of GNAT with other Ada 83 and Ada 95 compilation systems, to assist
820 in porting code from other environments.
824 @ref{Microsoft Windows Topics}, presents information relevant to the
825 Microsoft Windows platform.
830 @c *************************************************
831 @node What You Should Know before Reading This Guide
832 @c *************************************************
833 @unnumberedsec What You Should Know before Reading This Guide
835 @cindex Ada 95 Language Reference Manual
837 This user's guide assumes that you are familiar with Ada 95 language, as
838 described in the International Standard ANSI/ISO/IEC-8652:1995, January
841 @node Related Information
842 @unnumberedsec Related Information
845 For further information about related tools, refer to the following
850 @cite{GNAT Reference Manual}, which contains all reference
851 material for the GNAT implementation of Ada 95.
855 @cite{Using the GNAT Programming System}, which describes the GPS
856 integrated development environment.
859 @cite{GNAT Programming System Tutorial}, which introduces the
860 main GPS features through examples.
864 @cite{Ada 95 Language Reference Manual}, which contains all reference
865 material for the Ada 95 programming language.
868 @cite{Debugging with GDB}
870 , located in the GNU:[DOCS] directory,
872 contains all details on the use of the GNU source-level debugger.
875 @cite{GNU Emacs Manual}
877 , located in the GNU:[DOCS] directory if the EMACS kit is installed,
879 contains full information on the extensible editor and programming
886 @unnumberedsec Conventions
888 @cindex Typographical conventions
891 Following are examples of the typographical and graphic conventions used
896 @code{Functions}, @code{utility program names}, @code{standard names},
903 @file{File Names}, @file{button names}, and @file{field names}.
912 [optional information or parameters]
915 Examples are described by text
917 and then shown this way.
922 Commands that are entered by the user are preceded in this manual by the
923 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
924 uses this sequence as a prompt, then the commands will appear exactly as
925 you see them in the manual. If your system uses some other prompt, then
926 the command will appear with the @code{$} replaced by whatever prompt
927 character you are using.
930 Full file names are shown with the ``@code{/}'' character
931 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
932 If you are using GNAT on a Windows platform, please note that
933 the ``@code{\}'' character should be used instead.
938 @c ****************************
939 @node Getting Started with GNAT
940 @chapter Getting Started with GNAT
943 This chapter describes some simple ways of using GNAT to build
944 executable Ada programs.
946 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
947 show how to use the command line environment.
948 @ref{Introduction to Glide and GVD}, provides a brief
949 introduction to the visually-oriented IDE for GNAT.
950 Supplementing Glide on some platforms is GPS, the
951 GNAT Programming System, which offers a richer graphical
952 ``look and feel'', enhanced configurability, support for
953 development in other programming language, comprehensive
954 browsing features, and many other capabilities.
955 For information on GPS please refer to
956 @cite{Using the GNAT Programming System}.
961 * Running a Simple Ada Program::
962 * Running a Program with Multiple Units::
963 * Using the gnatmake Utility::
965 * Editing with Emacs::
968 * Introduction to GPS::
969 * Introduction to Glide and GVD::
974 @section Running GNAT
977 Three steps are needed to create an executable file from an Ada source
982 The source file(s) must be compiled.
984 The file(s) must be bound using the GNAT binder.
986 All appropriate object files must be linked to produce an executable.
990 All three steps are most commonly handled by using the @code{gnatmake}
991 utility program that, given the name of the main program, automatically
992 performs the necessary compilation, binding and linking steps.
995 @node Running a Simple Ada Program
996 @section Running a Simple Ada Program
999 Any text editor may be used to prepare an Ada program.
1002 used, the optional Ada mode may be helpful in laying out the program.
1005 program text is a normal text file. We will suppose in our initial
1006 example that you have used your editor to prepare the following
1007 standard format text file:
1009 @smallexample @c ada
1011 with Ada.Text_IO; use Ada.Text_IO;
1014 Put_Line ("Hello WORLD!");
1020 This file should be named @file{hello.adb}.
1021 With the normal default file naming conventions, GNAT requires
1023 contain a single compilation unit whose file name is the
1025 with periods replaced by hyphens; the
1026 extension is @file{ads} for a
1027 spec and @file{adb} for a body.
1028 You can override this default file naming convention by use of the
1029 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1030 Alternatively, if you want to rename your files according to this default
1031 convention, which is probably more convenient if you will be using GNAT
1032 for all your compilations, then the @code{gnatchop} utility
1033 can be used to generate correctly-named source files
1034 (@pxref{Renaming Files Using gnatchop}).
1036 You can compile the program using the following command (@code{$} is used
1037 as the command prompt in the examples in this document):
1044 @code{gcc} is the command used to run the compiler. This compiler is
1045 capable of compiling programs in several languages, including Ada 95 and
1046 C. It assumes that you have given it an Ada program if the file extension is
1047 either @file{.ads} or @file{.adb}, and it will then call
1048 the GNAT compiler to compile the specified file.
1051 The @option{-c} switch is required. It tells @command{gcc} to only do a
1052 compilation. (For C programs, @command{gcc} can also do linking, but this
1053 capability is not used directly for Ada programs, so the @option{-c}
1054 switch must always be present.)
1057 This compile command generates a file
1058 @file{hello.o}, which is the object
1059 file corresponding to your Ada program. It also generates
1060 an ``Ada Library Information'' file @file{hello.ali},
1061 which contains additional information used to check
1062 that an Ada program is consistent.
1063 To build an executable file,
1064 use @code{gnatbind} to bind the program
1065 and @code{gnatlink} to link it. The
1066 argument to both @code{gnatbind} and @code{gnatlink} is the name of the
1067 @file{ALI} file, but the default extension of @file{.ali} can
1068 be omitted. This means that in the most common case, the argument
1069 is simply the name of the main program:
1077 A simpler method of carrying out these steps is to use
1079 a master program that invokes all the required
1080 compilation, binding and linking tools in the correct order. In particular,
1081 @command{gnatmake} automatically recompiles any sources that have been
1082 modified since they were last compiled, or sources that depend
1083 on such modified sources, so that ``version skew'' is avoided.
1084 @cindex Version skew (avoided by @command{gnatmake})
1087 $ gnatmake hello.adb
1091 The result is an executable program called @file{hello}, which can be
1094 @c The following should be removed (BMB 2001-01-23)
1096 @c $ ^./hello^$ RUN HELLO^
1097 @c @end smallexample
1104 assuming that the current directory is on the search path
1105 for executable programs.
1108 and, if all has gone well, you will see
1115 appear in response to this command.
1118 @c ****************************************
1119 @node Running a Program with Multiple Units
1120 @section Running a Program with Multiple Units
1123 Consider a slightly more complicated example that has three files: a
1124 main program, and the spec and body of a package:
1126 @smallexample @c ada
1129 package Greetings is
1134 with Ada.Text_IO; use Ada.Text_IO;
1135 package body Greetings is
1138 Put_Line ("Hello WORLD!");
1141 procedure Goodbye is
1143 Put_Line ("Goodbye WORLD!");
1160 Following the one-unit-per-file rule, place this program in the
1161 following three separate files:
1165 spec of package @code{Greetings}
1168 body of package @code{Greetings}
1171 body of main program
1175 To build an executable version of
1176 this program, we could use four separate steps to compile, bind, and link
1177 the program, as follows:
1181 $ gcc -c greetings.adb
1187 Note that there is no required order of compilation when using GNAT.
1188 In particular it is perfectly fine to compile the main program first.
1189 Also, it is not necessary to compile package specs in the case where
1190 there is an accompanying body; you only need to compile the body. If you want
1191 to submit these files to the compiler for semantic checking and not code
1192 generation, then use the
1193 @option{-gnatc} switch:
1196 $ gcc -c greetings.ads -gnatc
1200 Although the compilation can be done in separate steps as in the
1201 above example, in practice it is almost always more convenient
1202 to use the @code{gnatmake} tool. All you need to know in this case
1203 is the name of the main program's source file. The effect of the above four
1204 commands can be achieved with a single one:
1207 $ gnatmake gmain.adb
1211 In the next section we discuss the advantages of using @code{gnatmake} in
1214 @c *****************************
1215 @node Using the gnatmake Utility
1216 @section Using the @command{gnatmake} Utility
1219 If you work on a program by compiling single components at a time using
1220 @code{gcc}, you typically keep track of the units you modify. In order to
1221 build a consistent system, you compile not only these units, but also any
1222 units that depend on the units you have modified.
1223 For example, in the preceding case,
1224 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1225 you edit @file{greetings.ads}, you must recompile both
1226 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1227 units that depend on @file{greetings.ads}.
1229 @code{gnatbind} will warn you if you forget one of these compilation
1230 steps, so that it is impossible to generate an inconsistent program as a
1231 result of forgetting to do a compilation. Nevertheless it is tedious and
1232 error-prone to keep track of dependencies among units.
1233 One approach to handle the dependency-bookkeeping is to use a
1234 makefile. However, makefiles present maintenance problems of their own:
1235 if the dependencies change as you change the program, you must make
1236 sure that the makefile is kept up-to-date manually, which is also an
1237 error-prone process.
1239 The @code{gnatmake} utility takes care of these details automatically.
1240 Invoke it using either one of the following forms:
1243 $ gnatmake gmain.adb
1244 $ gnatmake ^gmain^GMAIN^
1248 The argument is the name of the file containing the main program;
1249 you may omit the extension. @code{gnatmake}
1250 examines the environment, automatically recompiles any files that need
1251 recompiling, and binds and links the resulting set of object files,
1252 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1253 In a large program, it
1254 can be extremely helpful to use @code{gnatmake}, because working out by hand
1255 what needs to be recompiled can be difficult.
1257 Note that @code{gnatmake}
1258 takes into account all the Ada 95 rules that
1259 establish dependencies among units. These include dependencies that result
1260 from inlining subprogram bodies, and from
1261 generic instantiation. Unlike some other
1262 Ada make tools, @code{gnatmake} does not rely on the dependencies that were
1263 found by the compiler on a previous compilation, which may possibly
1264 be wrong when sources change. @code{gnatmake} determines the exact set of
1265 dependencies from scratch each time it is run.
1268 @node Editing with Emacs
1269 @section Editing with Emacs
1273 Emacs is an extensible self-documenting text editor that is available in a
1274 separate VMSINSTAL kit.
1276 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1277 click on the Emacs Help menu and run the Emacs Tutorial.
1278 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1279 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1281 Documentation on Emacs and other tools is available in Emacs under the
1282 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1283 use the middle mouse button to select a topic (e.g. Emacs).
1285 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1286 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1287 get to the Emacs manual.
1288 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1291 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1292 which is sufficiently extensible to provide for a complete programming
1293 environment and shell for the sophisticated user.
1297 @node Introduction to GPS
1298 @section Introduction to GPS
1299 @cindex GPS (GNAT Programming System)
1300 @cindex GNAT Programming System (GPS)
1302 Although the command line interface (@command{gnatmake}, etc.) alone
1303 is sufficient, a graphical Interactive Development
1304 Environment can make it easier for you to compose, navigate, and debug
1305 programs. This section describes the main features of GPS
1306 (``GNAT Programming System''), the GNAT graphical IDE.
1307 You will see how to use GPS to build and debug an executable, and
1308 you will also learn some of the basics of the GNAT ``project'' facility.
1310 GPS enables you to do much more than is presented here;
1311 e.g., you can produce a call graph, interface to a third-party
1312 Version Control System, and inspect the generated assembly language
1314 Indeed, GPS also supports languages other than Ada.
1315 Such additional information, and an explanation of all of the GPS menu
1316 items. may be found in the on-line help, which includes
1317 a user's guide and a tutorial (these are also accessible from the GNAT
1321 * Building a New Program with GPS::
1322 * Simple Debugging with GPS::
1326 @node Building a New Program with GPS
1327 @subsection Building a New Program with GPS
1329 GPS invokes the GNAT compilation tools using information
1330 contained in a @emph{project} (also known as a @emph{project file}):
1331 a collection of properties such
1332 as source directories, identities of main subprograms, tool switches, etc.,
1333 and their associated values.
1334 (See @ref{GNAT Project Manager}, for details.)
1335 In order to run GPS, you will need to either create a new project
1336 or else open an existing one.
1338 This section will explain how you can use GPS to create a project,
1339 to associate Ada source files with a project, and to build and run
1343 @item @emph{Creating a project}
1345 Invoke GPS, either from the command line or the platform's IDE.
1346 After it starts, GPS will display a ``Welcome'' screen with three
1351 @code{Start with default project in directory}
1354 @code{Create new project with wizard}
1357 @code{Open existing project}
1361 Select @code{Create new project with wizard} and press @code{OK}.
1362 A new window will appear. In the text box labeled with
1363 @code{Enter the name of the project to create}, type @file{sample}
1364 as the project name.
1365 In the next box, browse to choose the directory in which you
1366 would like to create the project file.
1367 After selecting an appropriate directory, press @code{Forward}.
1369 A window will appear with the title
1370 @code{Version Control System Configuration}.
1371 Simply press @code{Forward}.
1373 A window will appear with the title
1374 @code{Please select the source directories for this project}.
1375 The directory that you specified for the project file will be selected
1376 by default as the one to use for sources; simply press @code{Forward}.
1378 A window will appear with the title
1379 @code{Please select the build directory for this project}.
1380 The directory that you specified for the project file will be selected
1381 by default for object files and executables;
1382 simply press @code{Forward}.
1384 A window will appear with the title
1385 @code{Please select the main units for this project}.
1386 You will supply this information later, after creating the source file.
1387 Simply press @code{Forward} for now.
1389 A window will appear with the title
1390 @code{Please select the switches to build the project}.
1391 Press @code{Apply}. This will create a project file named
1392 @file{sample.prj} in the directory that you had specified.
1394 @item @emph{Creating and saving the source file}
1396 After you create the new project, a GPS window will appear, which is
1397 partitioned into two main sections:
1401 A @emph{Workspace area}, initially greyed out, which you will use for
1402 creating and editing source files
1405 Directly below, a @emph{Messages area}, which initially displays a
1406 ``Welcome'' message.
1407 (If the Messages area is not visible, drag its border upward to expand it.)
1411 Select @code{File} on the menu bar, and then the @code{New} command.
1412 The Workspace area will become white, and you can now
1413 enter the source program explicitly.
1414 Type the following text
1416 @smallexample @c ada
1418 with Ada.Text_IO; use Ada.Text_IO;
1421 Put_Line("Hello from GPS!");
1427 Select @code{File}, then @code{Save As}, and enter the source file name
1429 The file will be saved in the same directory you specified as the
1430 location of the default project file.
1433 @item @emph{Updating the project file}
1435 You need to add the new source file to the project.
1437 the @code{Project} menu and then @code{Edit project properties}.
1438 Click the @code{Main files} tab on the left, and then the
1440 Choose @file{hello.adb} from the list, and press @code{Open}.
1441 The project settings window will reflect this action.
1444 @item @emph{Building and running the program}
1446 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1447 and select @file{hello.adb}.
1448 The Messages window will display the resulting invocations of @command{gcc},
1449 @command{gnatbind}, and @command{gnatlink}
1450 (reflecting the default switch settings from the
1451 project file that you created) and then a ``successful compilation/build''
1454 To run the program, choose the @code{Build} menu, then @code{Run}, and
1455 select @command{hello}.
1456 An @emph{Arguments Selection} window will appear.
1457 There are no command line arguments, so just click @code{OK}.
1459 The Messages window will now display the program's output (the string
1460 @code{Hello from GPS}), and at the bottom of the GPS window a status
1461 update is displayed (@code{Run: hello}).
1462 Close the GPS window (or select @code{File}, then @code{Exit}) to
1463 terminate this GPS session.
1468 @node Simple Debugging with GPS
1469 @subsection Simple Debugging with GPS
1471 This section illustrates basic debugging techniques (setting breakpoints,
1472 examining/modifying variables, single stepping).
1475 @item @emph{Opening a project}
1477 Start GPS and select @code{Open existing project}; browse to
1478 specify the project file @file{sample.prj} that you had created in the
1481 @item @emph{Creating a source file}
1483 Select @code{File}, then @code{New}, and type in the following program:
1485 @smallexample @c ada
1487 with Ada.Text_IO; use Ada.Text_IO;
1488 procedure Example is
1489 Line : String (1..80);
1492 Put_Line("Type a line of text at each prompt; an empty line to exit");
1496 Put_Line (Line (1..N) );
1504 Select @code{File}, then @code{Save as}, and enter the file name
1507 @item @emph{Updating the project file}
1509 Add @code{Example} as a new main unit for the project:
1512 Select @code{Project}, then @code{Edit Project Properties}.
1515 Select the @code{Main files} tab, click @code{Add}, then
1516 select the file @file{example.adb} from the list, and
1518 You will see the file name appear in the list of main units
1524 @item @emph{Building/running the executable}
1526 To build the executable
1527 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1529 Run the program to see its effect (in the Messages area).
1530 Each line that you enter is displayed; an empty line will
1531 cause the loop to exit and the program to terminate.
1533 @item @emph{Debugging the program}
1535 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1536 which are required for debugging, are on by default when you create
1538 Thus unless you intentionally remove these settings, you will be able
1539 to debug any program that you develop using GPS.
1542 @item @emph{Initializing}
1544 Select @code{Debug}, then @code{Initialize}, then @file{example}
1546 @item @emph{Setting a breakpoint}
1548 After performing the initialization step, you will observe a small
1549 icon to the right of each line number.
1550 This serves as a toggle for breakpoints; clicking the icon will
1551 set a breakpoint at the corresponding line (the icon will change to
1552 a red circle with an ``x''), and clicking it again
1553 will remove the breakpoint / reset the icon.
1555 For purposes of this example, set a breakpoint at line 10 (the
1556 statement @code{Put_Line@ (Line@ (1..N));}
1558 @item @emph{Starting program execution}
1560 Select @code{Debug}, then @code{Run}. When the
1561 @code{Program Arguments} window appears, click @code{OK}.
1562 A console window will appear; enter some line of text,
1563 e.g. @code{abcde}, at the prompt.
1564 The program will pause execution when it gets to the
1565 breakpoint, and the corresponding line is highlighted.
1567 @item @emph{Examining a variable}
1569 Move the mouse over one of the occurrences of the variable @code{N}.
1570 You will see the value (5) displayed, in ``tool tip'' fashion.
1571 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1572 You will see information about @code{N} appear in the @code{Debugger Data}
1573 pane, showing the value as 5.
1576 @item @emph{Assigning a new value to a variable}
1578 Right click on the @code{N} in the @code{Debugger Data} pane, and
1579 select @code{Set value of N}.
1580 When the input window appears, enter the value @code{4} and click
1582 This value does not automatically appear in the @code{Debugger Data}
1583 pane; to see it, right click again on the @code{N} in the
1584 @code{Debugger Data} pane and select @code{Update value}.
1585 The new value, 4, will appear in red.
1587 @item @emph{Single stepping}
1589 Select @code{Debug}, then @code{Next}.
1590 This will cause the next statement to be executed, in this case the
1591 call of @code{Put_Line} with the string slice.
1592 Notice in the console window that the displayed string is simply
1593 @code{abcd} and not @code{abcde} which you had entered.
1594 This is because the upper bound of the slice is now 4 rather than 5.
1596 @item @emph{Removing a breakpoint}
1598 Toggle the breakpoint icon at line 10.
1600 @item @emph{Resuming execution from a breakpoint}
1602 Select @code{Debug}, then @code{Continue}.
1603 The program will reach the next iteration of the loop, and
1604 wait for input after displaying the prompt.
1605 This time, just hit the @kbd{Enter} key.
1606 The value of @code{N} will be 0, and the program will terminate.
1607 The console window will disappear.
1612 @node Introduction to Glide and GVD
1613 @section Introduction to Glide and GVD
1617 This section describes the main features of Glide,
1618 a GNAT graphical IDE, and also shows how to use the basic commands in GVD,
1619 the GNU Visual Debugger.
1620 These tools may be present in addition to, or in place of, GPS on some
1622 Additional information on Glide and GVD may be found
1623 in the on-line help for these tools.
1626 * Building a New Program with Glide::
1627 * Simple Debugging with GVD::
1628 * Other Glide Features::
1631 @node Building a New Program with Glide
1632 @subsection Building a New Program with Glide
1634 The simplest way to invoke Glide is to enter @command{glide}
1635 at the command prompt. It will generally be useful to issue this
1636 as a background command, thus allowing you to continue using
1637 your command window for other purposes while Glide is running:
1644 Glide will start up with an initial screen displaying the top-level menu items
1645 as well as some other information. The menu selections are as follows
1647 @item @code{Buffers}
1658 For this introductory example, you will need to create a new Ada source file.
1659 First, select the @code{Files} menu. This will pop open a menu with around
1660 a dozen or so items. To create a file, select the @code{Open file...} choice.
1661 Depending on the platform, you may see a pop-up window where you can browse
1662 to an appropriate directory and then enter the file name, or else simply
1663 see a line at the bottom of the Glide window where you can likewise enter
1664 the file name. Note that in Glide, when you attempt to open a non-existent
1665 file, the effect is to create a file with that name. For this example enter
1666 @file{hello.adb} as the name of the file.
1668 A new buffer will now appear, occupying the entire Glide window,
1669 with the file name at the top. The menu selections are slightly different
1670 from the ones you saw on the opening screen; there is an @code{Entities} item,
1671 and in place of @code{Glide} there is now an @code{Ada} item. Glide uses
1672 the file extension to identify the source language, so @file{adb} indicates
1675 You will enter some of the source program lines explicitly,
1676 and use the syntax-oriented template mechanism to enter other lines.
1677 First, type the following text:
1679 with Ada.Text_IO; use Ada.Text_IO;
1685 Observe that Glide uses different colors to distinguish reserved words from
1686 identifiers. Also, after the @code{procedure Hello is} line, the cursor is
1687 automatically indented in anticipation of declarations. When you enter
1688 @code{begin}, Glide recognizes that there are no declarations and thus places
1689 @code{begin} flush left. But after the @code{begin} line the cursor is again
1690 indented, where the statement(s) will be placed.
1692 The main part of the program will be a @code{for} loop. Instead of entering
1693 the text explicitly, however, use a statement template. Select the @code{Ada}
1694 item on the top menu bar, move the mouse to the @code{Statements} item,
1695 and you will see a large selection of alternatives. Choose @code{for loop}.
1696 You will be prompted (at the bottom of the buffer) for a loop name;
1697 simply press the @key{Enter} key since a loop name is not needed.
1698 You should see the beginning of a @code{for} loop appear in the source
1699 program window. You will now be prompted for the name of the loop variable;
1700 enter a line with the identifier @code{ind} (lower case). Note that,
1701 by default, Glide capitalizes the name (you can override such behavior
1702 if you wish, although this is outside the scope of this introduction).
1703 Next, Glide prompts you for the loop range; enter a line containing
1704 @code{1..5} and you will see this also appear in the source program,
1705 together with the remaining elements of the @code{for} loop syntax.
1707 Next enter the statement (with an intentional error, a missing semicolon)
1708 that will form the body of the loop:
1710 Put_Line("Hello, World" & Integer'Image(I))
1714 Finally, type @code{end Hello;} as the last line in the program.
1715 Now save the file: choose the @code{File} menu item, and then the
1716 @code{Save buffer} selection. You will see a message at the bottom
1717 of the buffer confirming that the file has been saved.
1719 You are now ready to attempt to build the program. Select the @code{Ada}
1720 item from the top menu bar. Although we could choose simply to compile
1721 the file, we will instead attempt to do a build (which invokes
1722 @command{gnatmake}) since, if the compile is successful, we want to build
1723 an executable. Thus select @code{Ada build}. This will fail because of the
1724 compilation error, and you will notice that the Glide window has been split:
1725 the top window contains the source file, and the bottom window contains the
1726 output from the GNAT tools. Glide allows you to navigate from a compilation
1727 error to the source file position corresponding to the error: click the
1728 middle mouse button (or simultaneously press the left and right buttons,
1729 on a two-button mouse) on the diagnostic line in the tool window. The
1730 focus will shift to the source window, and the cursor will be positioned
1731 on the character at which the error was detected.
1733 Correct the error: type in a semicolon to terminate the statement.
1734 Although you can again save the file explicitly, you can also simply invoke
1735 @code{Ada} @result{} @code{Build} and you will be prompted to save the file.
1736 This time the build will succeed; the tool output window shows you the
1737 options that are supplied by default. The GNAT tools' output (e.g.
1738 object and ALI files, executable) will go in the directory from which
1741 To execute the program, choose @code{Ada} and then @code{Run}.
1742 You should see the program's output displayed in the bottom window:
1752 @node Simple Debugging with GVD
1753 @subsection Simple Debugging with GVD
1756 This section describes how to set breakpoints, examine/modify variables,
1757 and step through execution.
1759 In order to enable debugging, you need to pass the @option{-g} switch
1760 to both the compiler and to @command{gnatlink}. If you are using
1761 the command line, passing @option{-g} to @command{gnatmake} will have
1762 this effect. You can then launch GVD, e.g. on the @code{hello} program,
1763 by issuing the command:
1770 If you are using Glide, then @option{-g} is passed to the relevant tools
1771 by default when you do a build. Start the debugger by selecting the
1772 @code{Ada} menu item, and then @code{Debug}.
1774 GVD comes up in a multi-part window. One pane shows the names of files
1775 comprising your executable; another pane shows the source code of the current
1776 unit (initially your main subprogram), another pane shows the debugger output
1777 and user interactions, and the fourth pane (the data canvas at the top
1778 of the window) displays data objects that you have selected.
1780 To the left of the source file pane, you will notice green dots adjacent
1781 to some lines. These are lines for which object code exists and where
1782 breakpoints can thus be set. You set/reset a breakpoint by clicking
1783 the green dot. When a breakpoint is set, the dot is replaced by an @code{X}
1784 in a red circle. Clicking the circle toggles the breakpoint off,
1785 and the red circle is replaced by the green dot.
1787 For this example, set a breakpoint at the statement where @code{Put_Line}
1790 Start program execution by selecting the @code{Run} button on the top menu bar.
1791 (The @code{Start} button will also start your program, but it will
1792 cause program execution to break at the entry to your main subprogram.)
1793 Evidence of reaching the breakpoint will appear: the source file line will be
1794 highlighted, and the debugger interactions pane will display
1797 You can examine the values of variables in several ways. Move the mouse
1798 over an occurrence of @code{Ind} in the @code{for} loop, and you will see
1799 the value (now @code{1}) displayed. Alternatively, right-click on @code{Ind}
1800 and select @code{Display Ind}; a box showing the variable's name and value
1801 will appear in the data canvas.
1803 Although a loop index is a constant with respect to Ada semantics,
1804 you can change its value in the debugger. Right-click in the box
1805 for @code{Ind}, and select the @code{Set Value of Ind} item.
1806 Enter @code{2} as the new value, and press @command{OK}.
1807 The box for @code{Ind} shows the update.
1809 Press the @code{Step} button on the top menu bar; this will step through
1810 one line of program text (the invocation of @code{Put_Line}), and you can
1811 observe the effect of having modified @code{Ind} since the value displayed
1814 Remove the breakpoint, and resume execution by selecting the @code{Cont}
1815 button. You will see the remaining output lines displayed in the debugger
1816 interaction window, along with a message confirming normal program
1819 @node Other Glide Features
1820 @subsection Other Glide Features
1823 You may have observed that some of the menu selections contain abbreviations;
1824 e.g., @code{(C-x C-f)} for @code{Open file...} in the @code{Files} menu.
1825 These are @emph{shortcut keys} that you can use instead of selecting
1826 menu items. The @key{C} stands for @key{Ctrl}; thus @code{(C-x C-f)} means
1827 @key{Ctrl-x} followed by @key{Ctrl-f}, and this sequence can be used instead
1828 of selecting @code{Files} and then @code{Open file...}.
1830 To abort a Glide command, type @key{Ctrl-g}.
1832 If you want Glide to start with an existing source file, you can either
1833 launch Glide as above and then open the file via @code{Files} @result{}
1834 @code{Open file...}, or else simply pass the name of the source file
1835 on the command line:
1842 While you are using Glide, a number of @emph{buffers} exist.
1843 You create some explicitly; e.g., when you open/create a file.
1844 Others arise as an effect of the commands that you issue; e.g., the buffer
1845 containing the output of the tools invoked during a build. If a buffer
1846 is hidden, you can bring it into a visible window by first opening
1847 the @code{Buffers} menu and then selecting the desired entry.
1849 If a buffer occupies only part of the Glide screen and you want to expand it
1850 to fill the entire screen, then click in the buffer and then select
1851 @code{Files} @result{} @code{One Window}.
1853 If a window is occupied by one buffer and you want to split the window
1854 to bring up a second buffer, perform the following steps:
1856 @item Select @code{Files} @result{} @code{Split Window};
1857 this will produce two windows each of which holds the original buffer
1858 (these are not copies, but rather different views of the same buffer contents)
1860 @item With the focus in one of the windows,
1861 select the desired buffer from the @code{Buffers} menu
1865 To exit from Glide, choose @code{Files} @result{} @code{Exit}.
1868 @node The GNAT Compilation Model
1869 @chapter The GNAT Compilation Model
1870 @cindex GNAT compilation model
1871 @cindex Compilation model
1874 * Source Representation::
1875 * Foreign Language Representation::
1876 * File Naming Rules::
1877 * Using Other File Names::
1878 * Alternative File Naming Schemes::
1879 * Generating Object Files::
1880 * Source Dependencies::
1881 * The Ada Library Information Files::
1882 * Binding an Ada Program::
1883 * Mixed Language Programming::
1884 * Building Mixed Ada & C++ Programs::
1885 * Comparison between GNAT and C/C++ Compilation Models::
1886 * Comparison between GNAT and Conventional Ada Library Models::
1888 * Placement of temporary files::
1893 This chapter describes the compilation model used by GNAT. Although
1894 similar to that used by other languages, such as C and C++, this model
1895 is substantially different from the traditional Ada compilation models,
1896 which are based on a library. The model is initially described without
1897 reference to the library-based model. If you have not previously used an
1898 Ada compiler, you need only read the first part of this chapter. The
1899 last section describes and discusses the differences between the GNAT
1900 model and the traditional Ada compiler models. If you have used other
1901 Ada compilers, this section will help you to understand those
1902 differences, and the advantages of the GNAT model.
1904 @node Source Representation
1905 @section Source Representation
1909 Ada source programs are represented in standard text files, using
1910 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1911 7-bit ASCII set, plus additional characters used for
1912 representing foreign languages (@pxref{Foreign Language Representation}
1913 for support of non-USA character sets). The format effector characters
1914 are represented using their standard ASCII encodings, as follows:
1919 Vertical tab, @code{16#0B#}
1923 Horizontal tab, @code{16#09#}
1927 Carriage return, @code{16#0D#}
1931 Line feed, @code{16#0A#}
1935 Form feed, @code{16#0C#}
1939 Source files are in standard text file format. In addition, GNAT will
1940 recognize a wide variety of stream formats, in which the end of physical
1941 physical lines is marked by any of the following sequences:
1942 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1943 in accommodating files that are imported from other operating systems.
1945 @cindex End of source file
1946 @cindex Source file, end
1948 The end of a source file is normally represented by the physical end of
1949 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1950 recognized as signalling the end of the source file. Again, this is
1951 provided for compatibility with other operating systems where this
1952 code is used to represent the end of file.
1954 Each file contains a single Ada compilation unit, including any pragmas
1955 associated with the unit. For example, this means you must place a
1956 package declaration (a package @dfn{spec}) and the corresponding body in
1957 separate files. An Ada @dfn{compilation} (which is a sequence of
1958 compilation units) is represented using a sequence of files. Similarly,
1959 you will place each subunit or child unit in a separate file.
1961 @node Foreign Language Representation
1962 @section Foreign Language Representation
1965 GNAT supports the standard character sets defined in Ada 95 as well as
1966 several other non-standard character sets for use in localized versions
1967 of the compiler (@pxref{Character Set Control}).
1970 * Other 8-Bit Codes::
1971 * Wide Character Encodings::
1979 The basic character set is Latin-1. This character set is defined by ISO
1980 standard 8859, part 1. The lower half (character codes @code{16#00#}
1981 ... @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1982 is used to represent additional characters. These include extended letters
1983 used by European languages, such as French accents, the vowels with umlauts
1984 used in German, and the extra letter A-ring used in Swedish.
1986 @findex Ada.Characters.Latin_1
1987 For a complete list of Latin-1 codes and their encodings, see the source
1988 file of library unit @code{Ada.Characters.Latin_1} in file
1989 @file{a-chlat1.ads}.
1990 You may use any of these extended characters freely in character or
1991 string literals. In addition, the extended characters that represent
1992 letters can be used in identifiers.
1994 @node Other 8-Bit Codes
1995 @subsection Other 8-Bit Codes
1998 GNAT also supports several other 8-bit coding schemes:
2001 @item ISO 8859-2 (Latin-2)
2004 Latin-2 letters allowed in identifiers, with uppercase and lowercase
2007 @item ISO 8859-3 (Latin-3)
2010 Latin-3 letters allowed in identifiers, with uppercase and lowercase
2013 @item ISO 8859-4 (Latin-4)
2016 Latin-4 letters allowed in identifiers, with uppercase and lowercase
2019 @item ISO 8859-5 (Cyrillic)
2022 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
2023 lowercase equivalence.
2025 @item ISO 8859-15 (Latin-9)
2028 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
2029 lowercase equivalence
2031 @item IBM PC (code page 437)
2032 @cindex code page 437
2033 This code page is the normal default for PCs in the U.S. It corresponds
2034 to the original IBM PC character set. This set has some, but not all, of
2035 the extended Latin-1 letters, but these letters do not have the same
2036 encoding as Latin-1. In this mode, these letters are allowed in
2037 identifiers with uppercase and lowercase equivalence.
2039 @item IBM PC (code page 850)
2040 @cindex code page 850
2041 This code page is a modification of 437 extended to include all the
2042 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
2043 mode, all these letters are allowed in identifiers with uppercase and
2044 lowercase equivalence.
2046 @item Full Upper 8-bit
2047 Any character in the range 80-FF allowed in identifiers, and all are
2048 considered distinct. In other words, there are no uppercase and lowercase
2049 equivalences in this range. This is useful in conjunction with
2050 certain encoding schemes used for some foreign character sets (e.g.
2051 the typical method of representing Chinese characters on the PC).
2054 No upper-half characters in the range 80-FF are allowed in identifiers.
2055 This gives Ada 83 compatibility for identifier names.
2059 For precise data on the encodings permitted, and the uppercase and lowercase
2060 equivalences that are recognized, see the file @file{csets.adb} in
2061 the GNAT compiler sources. You will need to obtain a full source release
2062 of GNAT to obtain this file.
2064 @node Wide Character Encodings
2065 @subsection Wide Character Encodings
2068 GNAT allows wide character codes to appear in character and string
2069 literals, and also optionally in identifiers, by means of the following
2070 possible encoding schemes:
2075 In this encoding, a wide character is represented by the following five
2083 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
2084 characters (using uppercase letters) of the wide character code. For
2085 example, ESC A345 is used to represent the wide character with code
2087 This scheme is compatible with use of the full Wide_Character set.
2089 @item Upper-Half Coding
2090 @cindex Upper-Half Coding
2091 The wide character with encoding @code{16#abcd#} where the upper bit is on
2092 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
2093 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
2094 character, but is not required to be in the upper half. This method can
2095 be also used for shift-JIS or EUC, where the internal coding matches the
2098 @item Shift JIS Coding
2099 @cindex Shift JIS Coding
2100 A wide character is represented by a two-character sequence,
2102 @code{16#cd#}, with the restrictions described for upper-half encoding as
2103 described above. The internal character code is the corresponding JIS
2104 character according to the standard algorithm for Shift-JIS
2105 conversion. Only characters defined in the JIS code set table can be
2106 used with this encoding method.
2110 A wide character is represented by a two-character sequence
2112 @code{16#cd#}, with both characters being in the upper half. The internal
2113 character code is the corresponding JIS character according to the EUC
2114 encoding algorithm. Only characters defined in the JIS code set table
2115 can be used with this encoding method.
2118 A wide character is represented using
2119 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
2120 10646-1/Am.2. Depending on the character value, the representation
2121 is a one, two, or three byte sequence:
2126 16#0000#-16#007f#: 2#0xxxxxxx#
2127 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
2128 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
2133 where the xxx bits correspond to the left-padded bits of the
2134 16-bit character value. Note that all lower half ASCII characters
2135 are represented as ASCII bytes and all upper half characters and
2136 other wide characters are represented as sequences of upper-half
2137 (The full UTF-8 scheme allows for encoding 31-bit characters as
2138 6-byte sequences, but in this implementation, all UTF-8 sequences
2139 of four or more bytes length will be treated as illegal).
2140 @item Brackets Coding
2141 In this encoding, a wide character is represented by the following eight
2149 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
2150 characters (using uppercase letters) of the wide character code. For
2151 example, [``A345''] is used to represent the wide character with code
2152 @code{16#A345#}. It is also possible (though not required) to use the
2153 Brackets coding for upper half characters. For example, the code
2154 @code{16#A3#} can be represented as @code{[``A3'']}.
2156 This scheme is compatible with use of the full Wide_Character set,
2157 and is also the method used for wide character encoding in the standard
2158 ACVC (Ada Compiler Validation Capability) test suite distributions.
2163 Note: Some of these coding schemes do not permit the full use of the
2164 Ada 95 character set. For example, neither Shift JIS, nor EUC allow the
2165 use of the upper half of the Latin-1 set.
2167 @node File Naming Rules
2168 @section File Naming Rules
2171 The default file name is determined by the name of the unit that the
2172 file contains. The name is formed by taking the full expanded name of
2173 the unit and replacing the separating dots with hyphens and using
2174 ^lowercase^uppercase^ for all letters.
2176 An exception arises if the file name generated by the above rules starts
2177 with one of the characters
2184 and the second character is a
2185 minus. In this case, the character ^tilde^dollar sign^ is used in place
2186 of the minus. The reason for this special rule is to avoid clashes with
2187 the standard names for child units of the packages System, Ada,
2188 Interfaces, and GNAT, which use the prefixes
2197 The file extension is @file{.ads} for a spec and
2198 @file{.adb} for a body. The following list shows some
2199 examples of these rules.
2206 @item arith_functions.ads
2207 Arith_Functions (package spec)
2208 @item arith_functions.adb
2209 Arith_Functions (package body)
2211 Func.Spec (child package spec)
2213 Func.Spec (child package body)
2215 Sub (subunit of Main)
2216 @item ^a~bad.adb^A$BAD.ADB^
2217 A.Bad (child package body)
2221 Following these rules can result in excessively long
2222 file names if corresponding
2223 unit names are long (for example, if child units or subunits are
2224 heavily nested). An option is available to shorten such long file names
2225 (called file name ``krunching''). This may be particularly useful when
2226 programs being developed with GNAT are to be used on operating systems
2227 with limited file name lengths. @xref{Using gnatkr}.
2229 Of course, no file shortening algorithm can guarantee uniqueness over
2230 all possible unit names; if file name krunching is used, it is your
2231 responsibility to ensure no name clashes occur. Alternatively you
2232 can specify the exact file names that you want used, as described
2233 in the next section. Finally, if your Ada programs are migrating from a
2234 compiler with a different naming convention, you can use the gnatchop
2235 utility to produce source files that follow the GNAT naming conventions.
2236 (For details @pxref{Renaming Files Using gnatchop}.)
2238 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2239 systems, case is not significant. So for example on @code{Windows XP}
2240 if the canonical name is @code{main-sub.adb}, you can use the file name
2241 @code{Main-Sub.adb} instead. However, case is significant for other
2242 operating systems, so for example, if you want to use other than
2243 canonically cased file names on a Unix system, you need to follow
2244 the procedures described in the next section.
2246 @node Using Other File Names
2247 @section Using Other File Names
2251 In the previous section, we have described the default rules used by
2252 GNAT to determine the file name in which a given unit resides. It is
2253 often convenient to follow these default rules, and if you follow them,
2254 the compiler knows without being explicitly told where to find all
2257 However, in some cases, particularly when a program is imported from
2258 another Ada compiler environment, it may be more convenient for the
2259 programmer to specify which file names contain which units. GNAT allows
2260 arbitrary file names to be used by means of the Source_File_Name pragma.
2261 The form of this pragma is as shown in the following examples:
2262 @cindex Source_File_Name pragma
2264 @smallexample @c ada
2266 pragma Source_File_Name (My_Utilities.Stacks,
2267 Spec_File_Name => "myutilst_a.ada");
2268 pragma Source_File_name (My_Utilities.Stacks,
2269 Body_File_Name => "myutilst.ada");
2274 As shown in this example, the first argument for the pragma is the unit
2275 name (in this example a child unit). The second argument has the form
2276 of a named association. The identifier
2277 indicates whether the file name is for a spec or a body;
2278 the file name itself is given by a string literal.
2280 The source file name pragma is a configuration pragma, which means that
2281 normally it will be placed in the @file{gnat.adc}
2282 file used to hold configuration
2283 pragmas that apply to a complete compilation environment.
2284 For more details on how the @file{gnat.adc} file is created and used
2285 @pxref{Handling of Configuration Pragmas}
2286 @cindex @file{gnat.adc}
2289 GNAT allows completely arbitrary file names to be specified using the
2290 source file name pragma. However, if the file name specified has an
2291 extension other than @file{.ads} or @file{.adb} it is necessary to use
2292 a special syntax when compiling the file. The name in this case must be
2293 preceded by the special sequence @code{-x} followed by a space and the name
2294 of the language, here @code{ada}, as in:
2297 $ gcc -c -x ada peculiar_file_name.sim
2302 @code{gnatmake} handles non-standard file names in the usual manner (the
2303 non-standard file name for the main program is simply used as the
2304 argument to gnatmake). Note that if the extension is also non-standard,
2305 then it must be included in the gnatmake command, it may not be omitted.
2307 @node Alternative File Naming Schemes
2308 @section Alternative File Naming Schemes
2309 @cindex File naming schemes, alternative
2312 In the previous section, we described the use of the @code{Source_File_Name}
2313 pragma to allow arbitrary names to be assigned to individual source files.
2314 However, this approach requires one pragma for each file, and especially in
2315 large systems can result in very long @file{gnat.adc} files, and also create
2316 a maintenance problem.
2318 GNAT also provides a facility for specifying systematic file naming schemes
2319 other than the standard default naming scheme previously described. An
2320 alternative scheme for naming is specified by the use of
2321 @code{Source_File_Name} pragmas having the following format:
2322 @cindex Source_File_Name pragma
2324 @smallexample @c ada
2325 pragma Source_File_Name (
2326 Spec_File_Name => FILE_NAME_PATTERN
2327 [,Casing => CASING_SPEC]
2328 [,Dot_Replacement => STRING_LITERAL]);
2330 pragma Source_File_Name (
2331 Body_File_Name => FILE_NAME_PATTERN
2332 [,Casing => CASING_SPEC]
2333 [,Dot_Replacement => STRING_LITERAL]);
2335 pragma Source_File_Name (
2336 Subunit_File_Name => FILE_NAME_PATTERN
2337 [,Casing => CASING_SPEC]
2338 [,Dot_Replacement => STRING_LITERAL]);
2340 FILE_NAME_PATTERN ::= STRING_LITERAL
2341 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2345 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2346 It contains a single asterisk character, and the unit name is substituted
2347 systematically for this asterisk. The optional parameter
2348 @code{Casing} indicates
2349 whether the unit name is to be all upper-case letters, all lower-case letters,
2350 or mixed-case. If no
2351 @code{Casing} parameter is used, then the default is all
2352 ^lower-case^upper-case^.
2354 The optional @code{Dot_Replacement} string is used to replace any periods
2355 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2356 argument is used then separating dots appear unchanged in the resulting
2358 Although the above syntax indicates that the
2359 @code{Casing} argument must appear
2360 before the @code{Dot_Replacement} argument, but it
2361 is also permissible to write these arguments in the opposite order.
2363 As indicated, it is possible to specify different naming schemes for
2364 bodies, specs, and subunits. Quite often the rule for subunits is the
2365 same as the rule for bodies, in which case, there is no need to give
2366 a separate @code{Subunit_File_Name} rule, and in this case the
2367 @code{Body_File_name} rule is used for subunits as well.
2369 The separate rule for subunits can also be used to implement the rather
2370 unusual case of a compilation environment (e.g. a single directory) which
2371 contains a subunit and a child unit with the same unit name. Although
2372 both units cannot appear in the same partition, the Ada Reference Manual
2373 allows (but does not require) the possibility of the two units coexisting
2374 in the same environment.
2376 The file name translation works in the following steps:
2381 If there is a specific @code{Source_File_Name} pragma for the given unit,
2382 then this is always used, and any general pattern rules are ignored.
2385 If there is a pattern type @code{Source_File_Name} pragma that applies to
2386 the unit, then the resulting file name will be used if the file exists. If
2387 more than one pattern matches, the latest one will be tried first, and the
2388 first attempt resulting in a reference to a file that exists will be used.
2391 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2392 for which the corresponding file exists, then the standard GNAT default
2393 naming rules are used.
2398 As an example of the use of this mechanism, consider a commonly used scheme
2399 in which file names are all lower case, with separating periods copied
2400 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2401 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2404 @smallexample @c ada
2405 pragma Source_File_Name
2406 (Spec_File_Name => "*.1.ada");
2407 pragma Source_File_Name
2408 (Body_File_Name => "*.2.ada");
2412 The default GNAT scheme is actually implemented by providing the following
2413 default pragmas internally:
2415 @smallexample @c ada
2416 pragma Source_File_Name
2417 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2418 pragma Source_File_Name
2419 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2423 Our final example implements a scheme typically used with one of the
2424 Ada 83 compilers, where the separator character for subunits was ``__''
2425 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2426 by adding @file{.ADA}, and subunits by
2427 adding @file{.SEP}. All file names were
2428 upper case. Child units were not present of course since this was an
2429 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2430 the same double underscore separator for child units.
2432 @smallexample @c ada
2433 pragma Source_File_Name
2434 (Spec_File_Name => "*_.ADA",
2435 Dot_Replacement => "__",
2436 Casing = Uppercase);
2437 pragma Source_File_Name
2438 (Body_File_Name => "*.ADA",
2439 Dot_Replacement => "__",
2440 Casing = Uppercase);
2441 pragma Source_File_Name
2442 (Subunit_File_Name => "*.SEP",
2443 Dot_Replacement => "__",
2444 Casing = Uppercase);
2447 @node Generating Object Files
2448 @section Generating Object Files
2451 An Ada program consists of a set of source files, and the first step in
2452 compiling the program is to generate the corresponding object files.
2453 These are generated by compiling a subset of these source files.
2454 The files you need to compile are the following:
2458 If a package spec has no body, compile the package spec to produce the
2459 object file for the package.
2462 If a package has both a spec and a body, compile the body to produce the
2463 object file for the package. The source file for the package spec need
2464 not be compiled in this case because there is only one object file, which
2465 contains the code for both the spec and body of the package.
2468 For a subprogram, compile the subprogram body to produce the object file
2469 for the subprogram. The spec, if one is present, is as usual in a
2470 separate file, and need not be compiled.
2474 In the case of subunits, only compile the parent unit. A single object
2475 file is generated for the entire subunit tree, which includes all the
2479 Compile child units independently of their parent units
2480 (though, of course, the spec of all the ancestor unit must be present in order
2481 to compile a child unit).
2485 Compile generic units in the same manner as any other units. The object
2486 files in this case are small dummy files that contain at most the
2487 flag used for elaboration checking. This is because GNAT always handles generic
2488 instantiation by means of macro expansion. However, it is still necessary to
2489 compile generic units, for dependency checking and elaboration purposes.
2493 The preceding rules describe the set of files that must be compiled to
2494 generate the object files for a program. Each object file has the same
2495 name as the corresponding source file, except that the extension is
2498 You may wish to compile other files for the purpose of checking their
2499 syntactic and semantic correctness. For example, in the case where a
2500 package has a separate spec and body, you would not normally compile the
2501 spec. However, it is convenient in practice to compile the spec to make
2502 sure it is error-free before compiling clients of this spec, because such
2503 compilations will fail if there is an error in the spec.
2505 GNAT provides an option for compiling such files purely for the
2506 purposes of checking correctness; such compilations are not required as
2507 part of the process of building a program. To compile a file in this
2508 checking mode, use the @option{-gnatc} switch.
2510 @node Source Dependencies
2511 @section Source Dependencies
2514 A given object file clearly depends on the source file which is compiled
2515 to produce it. Here we are using @dfn{depends} in the sense of a typical
2516 @code{make} utility; in other words, an object file depends on a source
2517 file if changes to the source file require the object file to be
2519 In addition to this basic dependency, a given object may depend on
2520 additional source files as follows:
2524 If a file being compiled @code{with}'s a unit @var{X}, the object file
2525 depends on the file containing the spec of unit @var{X}. This includes
2526 files that are @code{with}'ed implicitly either because they are parents
2527 of @code{with}'ed child units or they are run-time units required by the
2528 language constructs used in a particular unit.
2531 If a file being compiled instantiates a library level generic unit, the
2532 object file depends on both the spec and body files for this generic
2536 If a file being compiled instantiates a generic unit defined within a
2537 package, the object file depends on the body file for the package as
2538 well as the spec file.
2542 @cindex @option{-gnatn} switch
2543 If a file being compiled contains a call to a subprogram for which
2544 pragma @code{Inline} applies and inlining is activated with the
2545 @option{-gnatn} switch, the object file depends on the file containing the
2546 body of this subprogram as well as on the file containing the spec. Note
2547 that for inlining to actually occur as a result of the use of this switch,
2548 it is necessary to compile in optimizing mode.
2550 @cindex @option{-gnatN} switch
2551 The use of @option{-gnatN} activates a more extensive inlining optimization
2552 that is performed by the front end of the compiler. This inlining does
2553 not require that the code generation be optimized. Like @option{-gnatn},
2554 the use of this switch generates additional dependencies.
2556 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
2557 to specify both options.
2560 If an object file O depends on the proper body of a subunit through inlining
2561 or instantiation, it depends on the parent unit of the subunit. This means that
2562 any modification of the parent unit or one of its subunits affects the
2566 The object file for a parent unit depends on all its subunit body files.
2569 The previous two rules meant that for purposes of computing dependencies and
2570 recompilation, a body and all its subunits are treated as an indivisible whole.
2573 These rules are applied transitively: if unit @code{A} @code{with}'s
2574 unit @code{B}, whose elaboration calls an inlined procedure in package
2575 @code{C}, the object file for unit @code{A} will depend on the body of
2576 @code{C}, in file @file{c.adb}.
2578 The set of dependent files described by these rules includes all the
2579 files on which the unit is semantically dependent, as described in the
2580 Ada 95 Language Reference Manual. However, it is a superset of what the
2581 ARM describes, because it includes generic, inline, and subunit dependencies.
2583 An object file must be recreated by recompiling the corresponding source
2584 file if any of the source files on which it depends are modified. For
2585 example, if the @code{make} utility is used to control compilation,
2586 the rule for an Ada object file must mention all the source files on
2587 which the object file depends, according to the above definition.
2588 The determination of the necessary
2589 recompilations is done automatically when one uses @code{gnatmake}.
2592 @node The Ada Library Information Files
2593 @section The Ada Library Information Files
2594 @cindex Ada Library Information files
2595 @cindex @file{ALI} files
2598 Each compilation actually generates two output files. The first of these
2599 is the normal object file that has a @file{.o} extension. The second is a
2600 text file containing full dependency information. It has the same
2601 name as the source file, but an @file{.ali} extension.
2602 This file is known as the Ada Library Information (@file{ALI}) file.
2603 The following information is contained in the @file{ALI} file.
2607 Version information (indicates which version of GNAT was used to compile
2608 the unit(s) in question)
2611 Main program information (including priority and time slice settings,
2612 as well as the wide character encoding used during compilation).
2615 List of arguments used in the @code{gcc} command for the compilation
2618 Attributes of the unit, including configuration pragmas used, an indication
2619 of whether the compilation was successful, exception model used etc.
2622 A list of relevant restrictions applying to the unit (used for consistency)
2626 Categorization information (e.g. use of pragma @code{Pure}).
2629 Information on all @code{with}'ed units, including presence of
2630 @code{Elaborate} or @code{Elaborate_All} pragmas.
2633 Information from any @code{Linker_Options} pragmas used in the unit
2636 Information on the use of @code{Body_Version} or @code{Version}
2637 attributes in the unit.
2640 Dependency information. This is a list of files, together with
2641 time stamp and checksum information. These are files on which
2642 the unit depends in the sense that recompilation is required
2643 if any of these units are modified.
2646 Cross-reference data. Contains information on all entities referenced
2647 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2648 provide cross-reference information.
2653 For a full detailed description of the format of the @file{ALI} file,
2654 see the source of the body of unit @code{Lib.Writ}, contained in file
2655 @file{lib-writ.adb} in the GNAT compiler sources.
2657 @node Binding an Ada Program
2658 @section Binding an Ada Program
2661 When using languages such as C and C++, once the source files have been
2662 compiled the only remaining step in building an executable program
2663 is linking the object modules together. This means that it is possible to
2664 link an inconsistent version of a program, in which two units have
2665 included different versions of the same header.
2667 The rules of Ada do not permit such an inconsistent program to be built.
2668 For example, if two clients have different versions of the same package,
2669 it is illegal to build a program containing these two clients.
2670 These rules are enforced by the GNAT binder, which also determines an
2671 elaboration order consistent with the Ada rules.
2673 The GNAT binder is run after all the object files for a program have
2674 been created. It is given the name of the main program unit, and from
2675 this it determines the set of units required by the program, by reading the
2676 corresponding ALI files. It generates error messages if the program is
2677 inconsistent or if no valid order of elaboration exists.
2679 If no errors are detected, the binder produces a main program, in Ada by
2680 default, that contains calls to the elaboration procedures of those
2681 compilation unit that require them, followed by
2682 a call to the main program. This Ada program is compiled to generate the
2683 object file for the main program. The name of
2684 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2685 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2688 Finally, the linker is used to build the resulting executable program,
2689 using the object from the main program from the bind step as well as the
2690 object files for the Ada units of the program.
2692 @node Mixed Language Programming
2693 @section Mixed Language Programming
2694 @cindex Mixed Language Programming
2697 This section describes how to develop a mixed-language program,
2698 specifically one that comprises units in both Ada and C.
2701 * Interfacing to C::
2702 * Calling Conventions::
2705 @node Interfacing to C
2706 @subsection Interfacing to C
2708 Interfacing Ada with a foreign language such as C involves using
2709 compiler directives to import and/or export entity definitions in each
2710 language---using @code{extern} statements in C, for instance, and the
2711 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada. For
2712 a full treatment of these topics, read Appendix B, section 1 of the Ada
2713 95 Language Reference Manual.
2715 There are two ways to build a program using GNAT that contains some Ada
2716 sources and some foreign language sources, depending on whether or not
2717 the main subprogram is written in Ada. Here is a source example with
2718 the main subprogram in Ada:
2724 void print_num (int num)
2726 printf ("num is %d.\n", num);
2732 /* num_from_Ada is declared in my_main.adb */
2733 extern int num_from_Ada;
2737 return num_from_Ada;
2741 @smallexample @c ada
2743 procedure My_Main is
2745 -- Declare then export an Integer entity called num_from_Ada
2746 My_Num : Integer := 10;
2747 pragma Export (C, My_Num, "num_from_Ada");
2749 -- Declare an Ada function spec for Get_Num, then use
2750 -- C function get_num for the implementation.
2751 function Get_Num return Integer;
2752 pragma Import (C, Get_Num, "get_num");
2754 -- Declare an Ada procedure spec for Print_Num, then use
2755 -- C function print_num for the implementation.
2756 procedure Print_Num (Num : Integer);
2757 pragma Import (C, Print_Num, "print_num");
2760 Print_Num (Get_Num);
2766 To build this example, first compile the foreign language files to
2767 generate object files:
2774 Then, compile the Ada units to produce a set of object files and ALI
2777 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2781 Run the Ada binder on the Ada main program:
2783 gnatbind my_main.ali
2787 Link the Ada main program, the Ada objects and the other language
2790 gnatlink my_main.ali file1.o file2.o
2794 The last three steps can be grouped in a single command:
2796 gnatmake my_main.adb -largs file1.o file2.o
2799 @cindex Binder output file
2801 If the main program is in a language other than Ada, then you may have
2802 more than one entry point into the Ada subsystem. You must use a special
2803 binder option to generate callable routines that initialize and
2804 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2805 Calls to the initialization and finalization routines must be inserted
2806 in the main program, or some other appropriate point in the code. The
2807 call to initialize the Ada units must occur before the first Ada
2808 subprogram is called, and the call to finalize the Ada units must occur
2809 after the last Ada subprogram returns. The binder will place the
2810 initialization and finalization subprograms into the
2811 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2812 sources. To illustrate, we have the following example:
2816 extern void adainit (void);
2817 extern void adafinal (void);
2818 extern int add (int, int);
2819 extern int sub (int, int);
2821 int main (int argc, char *argv[])
2827 /* Should print "21 + 7 = 28" */
2828 printf ("%d + %d = %d\n", a, b, add (a, b));
2829 /* Should print "21 - 7 = 14" */
2830 printf ("%d - %d = %d\n", a, b, sub (a, b));
2836 @smallexample @c ada
2839 function Add (A, B : Integer) return Integer;
2840 pragma Export (C, Add, "add");
2844 package body Unit1 is
2845 function Add (A, B : Integer) return Integer is
2853 function Sub (A, B : Integer) return Integer;
2854 pragma Export (C, Sub, "sub");
2858 package body Unit2 is
2859 function Sub (A, B : Integer) return Integer is
2868 The build procedure for this application is similar to the last
2869 example's. First, compile the foreign language files to generate object
2876 Next, compile the Ada units to produce a set of object files and ALI
2879 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2880 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2884 Run the Ada binder on every generated ALI file. Make sure to use the
2885 @option{-n} option to specify a foreign main program:
2887 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2891 Link the Ada main program, the Ada objects and the foreign language
2892 objects. You need only list the last ALI file here:
2894 gnatlink unit2.ali main.o -o exec_file
2897 This procedure yields a binary executable called @file{exec_file}.
2900 @node Calling Conventions
2901 @subsection Calling Conventions
2902 @cindex Foreign Languages
2903 @cindex Calling Conventions
2904 GNAT follows standard calling sequence conventions and will thus interface
2905 to any other language that also follows these conventions. The following
2906 Convention identifiers are recognized by GNAT:
2909 @cindex Interfacing to Ada
2910 @cindex Other Ada compilers
2911 @cindex Convention Ada
2913 This indicates that the standard Ada calling sequence will be
2914 used and all Ada data items may be passed without any limitations in the
2915 case where GNAT is used to generate both the caller and callee. It is also
2916 possible to mix GNAT generated code and code generated by another Ada
2917 compiler. In this case, the data types should be restricted to simple
2918 cases, including primitive types. Whether complex data types can be passed
2919 depends on the situation. Probably it is safe to pass simple arrays, such
2920 as arrays of integers or floats. Records may or may not work, depending
2921 on whether both compilers lay them out identically. Complex structures
2922 involving variant records, access parameters, tasks, or protected types,
2923 are unlikely to be able to be passed.
2925 Note that in the case of GNAT running
2926 on a platform that supports DEC Ada 83, a higher degree of compatibility
2927 can be guaranteed, and in particular records are layed out in an identical
2928 manner in the two compilers. Note also that if output from two different
2929 compilers is mixed, the program is responsible for dealing with elaboration
2930 issues. Probably the safest approach is to write the main program in the
2931 version of Ada other than GNAT, so that it takes care of its own elaboration
2932 requirements, and then call the GNAT-generated adainit procedure to ensure
2933 elaboration of the GNAT components. Consult the documentation of the other
2934 Ada compiler for further details on elaboration.
2936 However, it is not possible to mix the tasking run time of GNAT and
2937 DEC Ada 83, All the tasking operations must either be entirely within
2938 GNAT compiled sections of the program, or entirely within DEC Ada 83
2939 compiled sections of the program.
2941 @cindex Interfacing to Assembly
2942 @cindex Convention Assembler
2944 Specifies assembler as the convention. In practice this has the
2945 same effect as convention Ada (but is not equivalent in the sense of being
2946 considered the same convention).
2948 @cindex Convention Asm
2951 Equivalent to Assembler.
2953 @cindex Interfacing to COBOL
2954 @cindex Convention COBOL
2957 Data will be passed according to the conventions described
2958 in section B.4 of the Ada 95 Reference Manual.
2961 @cindex Interfacing to C
2962 @cindex Convention C
2964 Data will be passed according to the conventions described
2965 in section B.3 of the Ada 95 Reference Manual.
2967 @findex C varargs function
2968 @cindex Intefacing to C varargs function
2969 @cindex varargs function intefacs
2970 @item C varargs function
2971 In C, @code{varargs} allows a function to take a variable number of
2972 arguments. There is no direct equivalent in this to Ada. One
2973 approach that can be used is to create a C wrapper for each
2974 different profile and then interface to this C wrapper. For
2975 example, to print an @code{int} value using @code{printf},
2976 create a C function @code{printfi} that takes two arguments, a
2977 pointer to a string and an int, and calls @code{printf}.
2978 Then in the Ada program, use pragma @code{Import} to
2979 interface to printfi.
2981 It may work on some platforms to directly interface to
2982 a @code{varargs} function by providing a specific Ada profile
2983 for a a particular call. However, this does not work on
2984 all platforms, since there is no guarantee that the
2985 calling sequence for a two argument normal C function
2986 is the same as for calling a @code{varargs} C function with
2987 the same two arguments.
2989 @cindex Convention Default
2994 @cindex Convention External
3000 @cindex Interfacing to C++
3001 @cindex Convention C++
3003 This stands for C++. For most purposes this is identical to C.
3004 See the separate description of the specialized GNAT pragmas relating to
3005 C++ interfacing for further details.
3008 @cindex Interfacing to Fortran
3009 @cindex Convention Fortran
3011 Data will be passed according to the conventions described
3012 in section B.5 of the Ada 95 Reference Manual.
3015 This applies to an intrinsic operation, as defined in the Ada 95
3016 Reference Manual. If a a pragma Import (Intrinsic) applies to a subprogram,
3017 this means that the body of the subprogram is provided by the compiler itself,
3018 usually by means of an efficient code sequence, and that the user does not
3019 supply an explicit body for it. In an application program, the pragma can
3020 only be applied to the following two sets of names, which the GNAT compiler
3025 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_-
3026 Arithmetic. The corresponding subprogram declaration must have
3027 two formal parameters. The
3028 first one must be a signed integer type or a modular type with a binary
3029 modulus, and the second parameter must be of type Natural.
3030 The return type must be the same as the type of the first argument. The size
3031 of this type can only be 8, 16, 32, or 64.
3032 @item binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
3033 The corresponding operator declaration must have parameters and result type
3034 that have the same root numeric type (for example, all three are long_float
3035 types). This simplifies the definition of operations that use type checking
3036 to perform dimensional checks:
3038 @smallexample @c ada
3039 type Distance is new Long_Float;
3040 type Time is new Long_Float;
3041 type Velocity is new Long_Float;
3042 function "/" (D : Distance; T : Time)
3044 pragma Import (Intrinsic, "/");
3048 This common idiom is often programmed with a generic definition and an
3049 explicit body. The pragma makes it simpler to introduce such declarations.
3050 It incurs no overhead in compilation time or code size, because it is
3051 implemented as a single machine instruction.
3057 @cindex Convention Stdcall
3059 This is relevant only to NT/Win95 implementations of GNAT,
3060 and specifies that the Stdcall calling sequence will be used, as defined
3064 @cindex Convention DLL
3066 This is equivalent to Stdcall.
3069 @cindex Convention Win32
3071 This is equivalent to Stdcall.
3075 @cindex Convention Stubbed
3077 This is a special convention that indicates that the compiler
3078 should provide a stub body that raises @code{Program_Error}.
3082 GNAT additionally provides a useful pragma @code{Convention_Identifier}
3083 that can be used to parametrize conventions and allow additional synonyms
3084 to be specified. For example if you have legacy code in which the convention
3085 identifier Fortran77 was used for Fortran, you can use the configuration
3088 @smallexample @c ada
3089 pragma Convention_Identifier (Fortran77, Fortran);
3093 And from now on the identifier Fortran77 may be used as a convention
3094 identifier (for example in an @code{Import} pragma) with the same
3097 @node Building Mixed Ada & C++ Programs
3098 @section Building Mixed Ada & C++ Programs
3101 A programmer inexperienced with mixed-language development may find that
3102 building an application containing both Ada and C++ code can be a
3103 challenge. As a matter of fact, interfacing with C++ has not been
3104 standardized in the Ada 95 Reference Manual due to the immaturity of --
3105 and lack of standards for -- C++ at the time. This section gives a few
3106 hints that should make this task easier. The first section addresses
3107 the differences regarding interfacing with C. The second section
3108 looks into the delicate problem of linking the complete application from
3109 its Ada and C++ parts. The last section gives some hints on how the GNAT
3110 run time can be adapted in order to allow inter-language dispatching
3111 with a new C++ compiler.
3114 * Interfacing to C++::
3115 * Linking a Mixed C++ & Ada Program::
3116 * A Simple Example::
3117 * Adapting the Run Time to a New C++ Compiler::
3120 @node Interfacing to C++
3121 @subsection Interfacing to C++
3124 GNAT supports interfacing with C++ compilers generating code that is
3125 compatible with the standard Application Binary Interface of the given
3129 Interfacing can be done at 3 levels: simple data, subprograms, and
3130 classes. In the first two cases, GNAT offers a specific @var{Convention
3131 CPP} that behaves exactly like @var{Convention C}. Usually, C++ mangles
3132 the names of subprograms, and currently, GNAT does not provide any help
3133 to solve the demangling problem. This problem can be addressed in two
3137 by modifying the C++ code in order to force a C convention using
3138 the @code{extern "C"} syntax.
3141 by figuring out the mangled name and use it as the Link_Name argument of
3146 Interfacing at the class level can be achieved by using the GNAT specific
3147 pragmas such as @code{CPP_Class} and @code{CPP_Virtual}. See the GNAT
3148 Reference Manual for additional information.
3150 @node Linking a Mixed C++ & Ada Program
3151 @subsection Linking a Mixed C++ & Ada Program
3154 Usually the linker of the C++ development system must be used to link
3155 mixed applications because most C++ systems will resolve elaboration
3156 issues (such as calling constructors on global class instances)
3157 transparently during the link phase. GNAT has been adapted to ease the
3158 use of a foreign linker for the last phase. Three cases can be
3163 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3164 The C++ linker can simply be called by using the C++ specific driver
3165 called @code{c++}. Note that this setup is not very common because it
3166 may involve recompiling the whole GCC tree from sources, which makes it
3167 harder to upgrade the compilation system for one language without
3168 destabilizing the other.
3173 $ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
3177 Using GNAT and G++ from two different GCC installations: If both
3178 compilers are on the PATH, the previous method may be used. It is
3179 important to note that environment variables such as C_INCLUDE_PATH,
3180 GCC_EXEC_PREFIX, BINUTILS_ROOT, and GCC_ROOT will affect both compilers
3181 at the same time and may make one of the two compilers operate
3182 improperly if set during invocation of the wrong compiler. It is also
3183 very important that the linker uses the proper @file{libgcc.a} GCC
3184 library -- that is, the one from the C++ compiler installation. The
3185 implicit link command as suggested in the gnatmake command from the
3186 former example can be replaced by an explicit link command with the
3187 full-verbosity option in order to verify which library is used:
3190 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3192 If there is a problem due to interfering environment variables, it can
3193 be worked around by using an intermediate script. The following example
3194 shows the proper script to use when GNAT has not been installed at its
3195 default location and g++ has been installed at its default location:
3203 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3207 Using a non-GNU C++ compiler: The commands previously described can be
3208 used to insure that the C++ linker is used. Nonetheless, you need to add
3209 the path to libgcc explicitly, since some libraries needed by GNAT are
3210 located in this directory:
3215 CC $* `gcc -print-libgcc-file-name`
3216 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3219 Where CC is the name of the non-GNU C++ compiler.
3223 @node A Simple Example
3224 @subsection A Simple Example
3226 The following example, provided as part of the GNAT examples, shows how
3227 to achieve procedural interfacing between Ada and C++ in both
3228 directions. The C++ class A has two methods. The first method is exported
3229 to Ada by the means of an extern C wrapper function. The second method
3230 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3231 a limited record with a layout comparable to the C++ class. The Ada
3232 subprogram, in turn, calls the C++ method. So, starting from the C++
3233 main program, the process passes back and forth between the two
3237 Here are the compilation commands:
3239 $ gnatmake -c simple_cpp_interface
3242 $ gnatbind -n simple_cpp_interface
3243 $ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
3244 -lstdc++ ex7.o cpp_main.o
3248 Here are the corresponding sources:
3256 void adainit (void);
3257 void adafinal (void);
3258 void method1 (A *t);
3280 class A : public Origin @{
3282 void method1 (void);
3283 virtual void method2 (int v);
3293 extern "C" @{ void ada_method2 (A *t, int v);@}
3295 void A::method1 (void)
3298 printf ("in A::method1, a_value = %d \n",a_value);
3302 void A::method2 (int v)
3304 ada_method2 (this, v);
3305 printf ("in A::method2, a_value = %d \n",a_value);
3312 printf ("in A::A, a_value = %d \n",a_value);
3316 @b{package} @b{body} Simple_Cpp_Interface @b{is}
3318 @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer) @b{is}
3322 @b{end} Ada_Method2;
3324 @b{end} Simple_Cpp_Interface;
3326 @b{package} Simple_Cpp_Interface @b{is}
3327 @b{type} A @b{is} @b{limited}
3332 @b{pragma} Convention (C, A);
3334 @b{procedure} Method1 (This : @b{in} @b{out} A);
3335 @b{pragma} Import (C, Method1);
3337 @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer);
3338 @b{pragma} Export (C, Ada_Method2);
3340 @b{end} Simple_Cpp_Interface;
3343 @node Adapting the Run Time to a New C++ Compiler
3344 @subsection Adapting the Run Time to a New C++ Compiler
3346 GNAT offers the capability to derive Ada 95 tagged types directly from
3347 preexisting C++ classes and . See ``Interfacing with C++'' in the
3348 @cite{GNAT Reference Manual}. The mechanism used by GNAT for achieving
3350 has been made user configurable through a GNAT library unit
3351 @code{Interfaces.CPP}. The default version of this file is adapted to
3352 the GNU C++ compiler. Internal knowledge of the virtual
3353 table layout used by the new C++ compiler is needed to configure
3354 properly this unit. The Interface of this unit is known by the compiler
3355 and cannot be changed except for the value of the constants defining the
3356 characteristics of the virtual table: CPP_DT_Prologue_Size, CPP_DT_Entry_Size,
3357 CPP_TSD_Prologue_Size, CPP_TSD_Entry_Size. Read comments in the source
3358 of this unit for more details.
3360 @node Comparison between GNAT and C/C++ Compilation Models
3361 @section Comparison between GNAT and C/C++ Compilation Models
3364 The GNAT model of compilation is close to the C and C++ models. You can
3365 think of Ada specs as corresponding to header files in C. As in C, you
3366 don't need to compile specs; they are compiled when they are used. The
3367 Ada @code{with} is similar in effect to the @code{#include} of a C
3370 One notable difference is that, in Ada, you may compile specs separately
3371 to check them for semantic and syntactic accuracy. This is not always
3372 possible with C headers because they are fragments of programs that have
3373 less specific syntactic or semantic rules.
3375 The other major difference is the requirement for running the binder,
3376 which performs two important functions. First, it checks for
3377 consistency. In C or C++, the only defense against assembling
3378 inconsistent programs lies outside the compiler, in a makefile, for
3379 example. The binder satisfies the Ada requirement that it be impossible
3380 to construct an inconsistent program when the compiler is used in normal
3383 @cindex Elaboration order control
3384 The other important function of the binder is to deal with elaboration
3385 issues. There are also elaboration issues in C++ that are handled
3386 automatically. This automatic handling has the advantage of being
3387 simpler to use, but the C++ programmer has no control over elaboration.
3388 Where @code{gnatbind} might complain there was no valid order of
3389 elaboration, a C++ compiler would simply construct a program that
3390 malfunctioned at run time.
3392 @node Comparison between GNAT and Conventional Ada Library Models
3393 @section Comparison between GNAT and Conventional Ada Library Models
3396 This section is intended to be useful to Ada programmers who have
3397 previously used an Ada compiler implementing the traditional Ada library
3398 model, as described in the Ada 95 Language Reference Manual. If you
3399 have not used such a system, please go on to the next section.
3401 @cindex GNAT library
3402 In GNAT, there is no @dfn{library} in the normal sense. Instead, the set of
3403 source files themselves acts as the library. Compiling Ada programs does
3404 not generate any centralized information, but rather an object file and
3405 a ALI file, which are of interest only to the binder and linker.
3406 In a traditional system, the compiler reads information not only from
3407 the source file being compiled, but also from the centralized library.
3408 This means that the effect of a compilation depends on what has been
3409 previously compiled. In particular:
3413 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3414 to the version of the unit most recently compiled into the library.
3417 Inlining is effective only if the necessary body has already been
3418 compiled into the library.
3421 Compiling a unit may obsolete other units in the library.
3425 In GNAT, compiling one unit never affects the compilation of any other
3426 units because the compiler reads only source files. Only changes to source
3427 files can affect the results of a compilation. In particular:
3431 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3432 to the source version of the unit that is currently accessible to the
3437 Inlining requires the appropriate source files for the package or
3438 subprogram bodies to be available to the compiler. Inlining is always
3439 effective, independent of the order in which units are complied.
3442 Compiling a unit never affects any other compilations. The editing of
3443 sources may cause previous compilations to be out of date if they
3444 depended on the source file being modified.
3448 The most important result of these differences is that order of compilation
3449 is never significant in GNAT. There is no situation in which one is
3450 required to do one compilation before another. What shows up as order of
3451 compilation requirements in the traditional Ada library becomes, in
3452 GNAT, simple source dependencies; in other words, there is only a set
3453 of rules saying what source files must be present when a file is
3457 @node Placement of temporary files
3458 @section Placement of temporary files
3459 @cindex Temporary files (user control over placement)
3462 GNAT creates temporary files in the directory designated by the environment
3463 variable @env{TMPDIR}.
3464 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3465 for detailed information on how environment variables are resolved.
3466 For most users the easiest way to make use of this feature is to simply
3467 define @env{TMPDIR} as a job level logical name).
3468 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3469 for compiler temporary files, then you can include something like the
3470 following command in your @file{LOGIN.COM} file:
3473 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3477 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3478 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3479 designated by @env{TEMP}.
3480 If none of these environment variables are defined then GNAT uses the
3481 directory designated by the logical name @code{SYS$SCRATCH:}
3482 (by default the user's home directory). If all else fails
3483 GNAT uses the current directory for temporary files.
3487 @c *************************
3488 @node Compiling Using gcc
3489 @chapter Compiling Using @code{gcc}
3492 This chapter discusses how to compile Ada programs using the @code{gcc}
3493 command. It also describes the set of switches
3494 that can be used to control the behavior of the compiler.
3496 * Compiling Programs::
3497 * Switches for gcc::
3498 * Search Paths and the Run-Time Library (RTL)::
3499 * Order of Compilation Issues::
3503 @node Compiling Programs
3504 @section Compiling Programs
3507 The first step in creating an executable program is to compile the units
3508 of the program using the @code{gcc} command. You must compile the
3513 the body file (@file{.adb}) for a library level subprogram or generic
3517 the spec file (@file{.ads}) for a library level package or generic
3518 package that has no body
3521 the body file (@file{.adb}) for a library level package
3522 or generic package that has a body
3527 You need @emph{not} compile the following files
3532 the spec of a library unit which has a body
3539 because they are compiled as part of compiling related units. GNAT
3541 when the corresponding body is compiled, and subunits when the parent is
3544 @cindex cannot generate code
3545 If you attempt to compile any of these files, you will get one of the
3546 following error messages (where fff is the name of the file you compiled):
3549 cannot generate code for file @var{fff} (package spec)
3550 to check package spec, use -gnatc
3552 cannot generate code for file @var{fff} (missing subunits)
3553 to check parent unit, use -gnatc
3555 cannot generate code for file @var{fff} (subprogram spec)
3556 to check subprogram spec, use -gnatc
3558 cannot generate code for file @var{fff} (subunit)
3559 to check subunit, use -gnatc
3563 As indicated by the above error messages, if you want to submit
3564 one of these files to the compiler to check for correct semantics
3565 without generating code, then use the @option{-gnatc} switch.
3567 The basic command for compiling a file containing an Ada unit is
3570 $ gcc -c [@var{switches}] @file{file name}
3574 where @var{file name} is the name of the Ada file (usually
3576 @file{.ads} for a spec or @file{.adb} for a body).
3579 @option{-c} switch to tell @code{gcc} to compile, but not link, the file.
3581 The result of a successful compilation is an object file, which has the
3582 same name as the source file but an extension of @file{.o} and an Ada
3583 Library Information (ALI) file, which also has the same name as the
3584 source file, but with @file{.ali} as the extension. GNAT creates these
3585 two output files in the current directory, but you may specify a source
3586 file in any directory using an absolute or relative path specification
3587 containing the directory information.
3590 @code{gcc} is actually a driver program that looks at the extensions of
3591 the file arguments and loads the appropriate compiler. For example, the
3592 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3593 These programs are in directories known to the driver program (in some
3594 configurations via environment variables you set), but need not be in
3595 your path. The @code{gcc} driver also calls the assembler and any other
3596 utilities needed to complete the generation of the required object
3599 It is possible to supply several file names on the same @code{gcc}
3600 command. This causes @code{gcc} to call the appropriate compiler for
3601 each file. For example, the following command lists three separate
3602 files to be compiled:
3605 $ gcc -c x.adb y.adb z.c
3609 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3610 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3611 The compiler generates three object files @file{x.o}, @file{y.o} and
3612 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3613 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3616 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3619 @node Switches for gcc
3620 @section Switches for @code{gcc}
3623 The @code{gcc} command accepts switches that control the
3624 compilation process. These switches are fully described in this section.
3625 First we briefly list all the switches, in alphabetical order, then we
3626 describe the switches in more detail in functionally grouped sections.
3629 * Output and Error Message Control::
3630 * Warning Message Control::
3631 * Debugging and Assertion Control::
3632 * Validity Checking::
3635 * Stack Overflow Checking::
3636 * Using gcc for Syntax Checking::
3637 * Using gcc for Semantic Checking::
3638 * Compiling Ada 83 Programs::
3639 * Character Set Control::
3640 * File Naming Control::
3641 * Subprogram Inlining Control::
3642 * Auxiliary Output Control::
3643 * Debugging Control::
3644 * Exception Handling Control::
3645 * Units to Sources Mapping Files::
3646 * Integrated Preprocessing::
3647 * Code Generation Control::
3656 @cindex @option{-b} (@code{gcc})
3657 @item -b @var{target}
3658 Compile your program to run on @var{target}, which is the name of a
3659 system configuration. You must have a GNAT cross-compiler built if
3660 @var{target} is not the same as your host system.
3663 @cindex @option{-B} (@code{gcc})
3664 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3665 from @var{dir} instead of the default location. Only use this switch
3666 when multiple versions of the GNAT compiler are available. See the
3667 @code{gcc} manual page for further details. You would normally use the
3668 @option{-b} or @option{-V} switch instead.
3671 @cindex @option{-c} (@code{gcc})
3672 Compile. Always use this switch when compiling Ada programs.
3674 Note: for some other languages when using @code{gcc}, notably in
3675 the case of C and C++, it is possible to use
3676 use @code{gcc} without a @option{-c} switch to
3677 compile and link in one step. In the case of GNAT, you
3678 cannot use this approach, because the binder must be run
3679 and @code{gcc} cannot be used to run the GNAT binder.
3683 @cindex @option{-fno-inline} (@code{gcc})
3684 Suppresses all back-end inlining, even if other optimization or inlining
3686 This includes suppression of inlining that results
3687 from the use of the pragma @code{Inline_Always}.
3688 See also @option{-gnatn} and @option{-gnatN}.
3690 @item -fno-strict-aliasing
3691 @cindex @option{-fno-strict-aliasing} (@code{gcc})
3692 Causes the compiler to avoid assumptions regarding non-aliasing
3693 of objects of different types. See section
3694 @pxref{Optimization and Strict Aliasing} for details.
3697 @cindex @option{-fstack-check} (@code{gcc})
3698 Activates stack checking.
3699 See @ref{Stack Overflow Checking} for details of the use of this option.
3702 @cindex @option{^-g^/DEBUG^} (@code{gcc})
3703 Generate debugging information. This information is stored in the object
3704 file and copied from there to the final executable file by the linker,
3705 where it can be read by the debugger. You must use the
3706 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
3709 @cindex @option{-gnat83} (@code{gcc})
3710 Enforce Ada 83 restrictions.
3713 @cindex @option{-gnata} (@code{gcc})
3714 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
3718 @cindex @option{-gnatA} (@code{gcc})
3719 Avoid processing @file{gnat.adc}. If a gnat.adc file is present,
3723 @cindex @option{-gnatb} (@code{gcc})
3724 Generate brief messages to @file{stderr} even if verbose mode set.
3727 @cindex @option{-gnatc} (@code{gcc})
3728 Check syntax and semantics only (no code generation attempted).
3731 @cindex @option{-gnatd} (@code{gcc})
3732 Specify debug options for the compiler. The string of characters after
3733 the @option{-gnatd} specify the specific debug options. The possible
3734 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
3735 compiler source file @file{debug.adb} for details of the implemented
3736 debug options. Certain debug options are relevant to applications
3737 programmers, and these are documented at appropriate points in this
3741 @cindex @option{-gnatD} (@code{gcc})
3742 Create expanded source files for source level debugging. This switch
3743 also suppress generation of cross-reference information
3744 (see @option{-gnatx}).
3746 @item -gnatec=@var{path}
3747 @cindex @option{-gnatec} (@code{gcc})
3748 Specify a configuration pragma file
3750 (the equal sign is optional)
3752 (see @ref{The Configuration Pragmas Files}).
3754 @item ^-gnateD^/DATA_PREPROCESSING=^symbol[=value]
3755 @cindex @option{-gnateD} (@code{gcc})
3756 Defines a symbol, associated with value, for preprocessing.
3757 (see @ref{Integrated Preprocessing})
3760 @cindex @option{-gnatef} (@code{gcc})
3761 Display full source path name in brief error messages.
3763 @item -gnatem=@var{path}
3764 @cindex @option{-gnatem} (@code{gcc})
3765 Specify a mapping file
3767 (the equal sign is optional)
3769 (see @ref{Units to Sources Mapping Files}).
3771 @item -gnatep=@var{file}
3772 @cindex @option{-gnatep} (@code{gcc})
3773 Specify a preprocessing data file
3775 (the equal sign is optional)
3777 (see @ref{Integrated Preprocessing}).
3780 @cindex @option{-gnatE} (@code{gcc})
3781 Full dynamic elaboration checks.
3784 @cindex @option{-gnatf} (@code{gcc})
3785 Full errors. Multiple errors per line, all undefined references, do not
3786 attempt to suppress cascaded errors.
3789 @cindex @option{-gnatF} (@code{gcc})
3790 Externals names are folded to all uppercase.
3793 @cindex @option{-gnatg} (@code{gcc})
3794 Internal GNAT implementation mode. This should not be used for
3795 applications programs, it is intended only for use by the compiler
3796 and its run-time library. For documentation, see the GNAT sources.
3797 Note that @option{-gnatg} implies @option{-gnatwu} so that warnings
3798 are generated on unreferenced entities, and all warnings are treated
3802 @cindex @option{-gnatG} (@code{gcc})
3803 List generated expanded code in source form.
3805 @item ^-gnath^/HELP^
3806 @cindex @option{^-gnath^/HELP^} (@code{gcc})
3807 Output usage information. The output is written to @file{stdout}.
3809 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3810 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
3811 Identifier character set
3813 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3816 For details of the possible selections for @var{c},
3817 see @xref{Character Set Control}.
3820 @item -gnatk=@var{n}
3821 @cindex @option{-gnatk} (@code{gcc})
3822 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
3825 @cindex @option{-gnatl} (@code{gcc})
3826 Output full source listing with embedded error messages.
3829 @cindex @option{-gnatL} (@code{gcc})
3830 Use the longjmp/setjmp method for exception handling
3832 @item -gnatm=@var{n}
3833 @cindex @option{-gnatm} (@code{gcc})
3834 Limit number of detected error or warning messages to @var{n}
3835 where @var{n} is in the range 1..999_999. The default setting if
3836 no switch is given is 9999. Compilation is terminated if this
3840 @cindex @option{-gnatn} (@code{gcc})
3841 Activate inlining for subprograms for which
3842 pragma @code{inline} is specified. This inlining is performed
3843 by the GCC back-end.
3846 @cindex @option{-gnatN} (@code{gcc})
3847 Activate front end inlining for subprograms for which
3848 pragma @code{Inline} is specified. This inlining is performed
3849 by the front end and will be visible in the
3850 @option{-gnatG} output.
3851 In some cases, this has proved more effective than the back end
3852 inlining resulting from the use of
3855 @option{-gnatN} automatically implies
3856 @option{-gnatn} so it is not necessary
3857 to specify both options. There are a few cases that the back-end inlining
3858 catches that cannot be dealt with in the front-end.
3861 @cindex @option{-gnato} (@code{gcc})
3862 Enable numeric overflow checking (which is not normally enabled by
3863 default). Not that division by zero is a separate check that is not
3864 controlled by this switch (division by zero checking is on by default).
3867 @cindex @option{-gnatp} (@code{gcc})
3868 Suppress all checks.
3871 @cindex @option{-gnatP} (@code{gcc})
3872 Enable polling. This is required on some systems (notably Windows NT) to
3873 obtain asynchronous abort and asynchronous transfer of control capability.
3874 See the description of pragma Polling in the GNAT Reference Manual for
3878 @cindex @option{-gnatq} (@code{gcc})
3879 Don't quit; try semantics, even if parse errors.
3882 @cindex @option{-gnatQ} (@code{gcc})
3883 Don't quit; generate @file{ALI} and tree files even if illegalities.
3885 @item ^-gnatR[0/1/2/3[s]]^/REPRESENTATION_INFO^
3886 @cindex @option{-gnatR} (@code{gcc})
3887 Output representation information for declared types and objects.
3890 @cindex @option{-gnats} (@code{gcc})
3894 @cindex @option{-gnatS} (@code{gcc})
3895 Print package Standard.
3898 @cindex @option{-gnatt} (@code{gcc})
3899 Generate tree output file.
3901 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
3902 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@code{gcc})
3903 All compiler tables start at @var{nnn} times usual starting size.
3906 @cindex @option{-gnatu} (@code{gcc})
3907 List units for this compilation.
3910 @cindex @option{-gnatU} (@code{gcc})
3911 Tag all error messages with the unique string ``error:''
3914 @cindex @option{-gnatv} (@code{gcc})
3915 Verbose mode. Full error output with source lines to @file{stdout}.
3918 @cindex @option{-gnatV} (@code{gcc})
3919 Control level of validity checking. See separate section describing
3922 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}[,...])^
3923 @cindex @option{^-gnatw^/WARNINGS^} (@code{gcc})
3925 ^@var{xxx} is a string of option letters that^the list of options^ denotes
3926 the exact warnings that
3927 are enabled or disabled. (see @ref{Warning Message Control})
3929 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
3930 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
3931 Wide character encoding method
3933 (@var{e}=n/h/u/s/e/8).
3936 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
3940 @cindex @option{-gnatx} (@code{gcc})
3941 Suppress generation of cross-reference information.
3943 @item ^-gnaty^/STYLE_CHECKS=(option,option..)^
3944 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@code{gcc})
3945 Enable built-in style checks. (see @ref{Style Checking})
3947 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
3948 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@code{gcc})
3949 Distribution stub generation and compilation
3951 (@var{m}=r/c for receiver/caller stubs).
3954 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
3955 to be generated and compiled).
3959 Use the zero cost method for exception handling
3961 @item ^-I^/SEARCH=^@var{dir}
3962 @cindex @option{^-I^/SEARCH^} (@code{gcc})
3964 Direct GNAT to search the @var{dir} directory for source files needed by
3965 the current compilation
3966 (@pxref{Search Paths and the Run-Time Library (RTL)}).
3968 @item ^-I-^/NOCURRENT_DIRECTORY^
3969 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gcc})
3971 Except for the source file named in the command line, do not look for source
3972 files in the directory containing the source file named in the command line
3973 (@pxref{Search Paths and the Run-Time Library (RTL)}).
3977 @cindex @option{-mbig-switch} (@command{gcc})
3978 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
3979 This standard gcc switch causes the compiler to use larger offsets in its
3980 jump table representation for @code{case} statements.
3981 This may result in less efficient code, but is sometimes necessary
3982 (for example on HP-UX targets)
3983 @cindex HP-UX and @option{-mbig-switch} option
3984 in order to compile large and/or nested @code{case} statements.
3987 @cindex @option{-o} (@code{gcc})
3988 This switch is used in @code{gcc} to redirect the generated object file
3989 and its associated ALI file. Beware of this switch with GNAT, because it may
3990 cause the object file and ALI file to have different names which in turn
3991 may confuse the binder and the linker.
3995 @cindex @option{-nostdinc} (@command{gcc})
3996 Inhibit the search of the default location for the GNAT Run Time
3997 Library (RTL) source files.
4000 @cindex @option{-nostdlib} (@command{gcc})
4001 Inhibit the search of the default location for the GNAT Run Time
4002 Library (RTL) ALI files.
4006 @cindex @option{-O} (@code{gcc})
4007 @var{n} controls the optimization level.
4011 No optimization, the default setting if no @option{-O} appears
4014 Normal optimization, the default if you specify @option{-O} without
4018 Extensive optimization
4021 Extensive optimization with automatic inlining of subprograms not
4022 specified by pragma @code{Inline}. This applies only to
4023 inlining within a unit. For details on control of inlining
4024 see @xref{Subprogram Inlining Control}.
4030 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4031 Equivalent to @option{/OPTIMIZE=NONE}.
4032 This is the default behavior in the absence of an @option{/OPTMIZE}
4035 @item /OPTIMIZE[=(keyword[,...])]
4036 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4037 Selects the level of optimization for your program. The supported
4038 keywords are as follows:
4041 Perform most optimizations, including those that
4043 This is the default if the @option{/OPTMIZE} qualifier is supplied
4044 without keyword options.
4047 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4050 Perform some optimizations, but omit ones that are costly.
4053 Same as @code{SOME}.
4056 Full optimization, and also attempt automatic inlining of small
4057 subprograms within a unit even when pragma @code{Inline}
4058 is not specified (@pxref{Inlining of Subprograms}).
4061 Try to unroll loops. This keyword may be specified together with
4062 any keyword above other than @code{NONE}. Loop unrolling
4063 usually, but not always, improves the performance of programs.
4068 @item -pass-exit-codes
4069 @cindex @option{-pass-exit-codes} (@code{gcc})
4070 Catch exit codes from the compiler and use the most meaningful as
4074 @item --RTS=@var{rts-path}
4075 @cindex @option{--RTS} (@code{gcc})
4076 Specifies the default location of the runtime library. Same meaning as the
4077 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
4080 @cindex @option{^-S^/ASM^} (@code{gcc})
4081 ^Used in place of @option{-c} to^Used to^
4082 cause the assembler source file to be
4083 generated, using @file{^.s^.S^} as the extension,
4084 instead of the object file.
4085 This may be useful if you need to examine the generated assembly code.
4087 @item ^-fverbose-asm^/VERBOSE_ASM^
4088 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@code{gcc})
4089 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4090 to cause the generated assembly code file to be annotated with variable
4091 names, making it significantly easier to follow.
4094 @cindex @option{^-v^/VERBOSE^} (@code{gcc})
4095 Show commands generated by the @code{gcc} driver. Normally used only for
4096 debugging purposes or if you need to be sure what version of the
4097 compiler you are executing.
4101 @cindex @option{-V} (@code{gcc})
4102 Execute @var{ver} version of the compiler. This is the @code{gcc}
4103 version, not the GNAT version.
4109 You may combine a sequence of GNAT switches into a single switch. For
4110 example, the combined switch
4112 @cindex Combining GNAT switches
4118 is equivalent to specifying the following sequence of switches:
4121 -gnato -gnatf -gnati3
4126 @c NEED TO CHECK THIS FOR VMS
4129 The following restrictions apply to the combination of switches
4134 The switch @option{-gnatc} if combined with other switches must come
4135 first in the string.
4138 The switch @option{-gnats} if combined with other switches must come
4139 first in the string.
4143 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4144 may not be combined with any other switches.
4148 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4149 switch), then all further characters in the switch are interpreted
4150 as style modifiers (see description of @option{-gnaty}).
4153 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4154 switch), then all further characters in the switch are interpreted
4155 as debug flags (see description of @option{-gnatd}).
4158 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4159 switch), then all further characters in the switch are interpreted
4160 as warning mode modifiers (see description of @option{-gnatw}).
4163 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4164 switch), then all further characters in the switch are interpreted
4165 as validity checking options (see description of @option{-gnatV}).
4170 @node Output and Error Message Control
4171 @subsection Output and Error Message Control
4175 The standard default format for error messages is called ``brief format''.
4176 Brief format messages are written to @file{stderr} (the standard error
4177 file) and have the following form:
4180 e.adb:3:04: Incorrect spelling of keyword "function"
4181 e.adb:4:20: ";" should be "is"
4185 The first integer after the file name is the line number in the file,
4186 and the second integer is the column number within the line.
4187 @code{glide} can parse the error messages
4188 and point to the referenced character.
4189 The following switches provide control over the error message
4195 @cindex @option{-gnatv} (@code{gcc})
4198 The v stands for verbose.
4200 The effect of this setting is to write long-format error
4201 messages to @file{stdout} (the standard output file.
4202 The same program compiled with the
4203 @option{-gnatv} switch would generate:
4207 3. funcion X (Q : Integer)
4209 >>> Incorrect spelling of keyword "function"
4212 >>> ";" should be "is"
4217 The vertical bar indicates the location of the error, and the @samp{>>>}
4218 prefix can be used to search for error messages. When this switch is
4219 used the only source lines output are those with errors.
4222 @cindex @option{-gnatl} (@code{gcc})
4224 The @code{l} stands for list.
4226 This switch causes a full listing of
4227 the file to be generated. The output might look as follows:
4233 3. funcion X (Q : Integer)
4235 >>> Incorrect spelling of keyword "function"
4238 >>> ";" should be "is"
4250 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4251 standard output is redirected, a brief summary is written to
4252 @file{stderr} (standard error) giving the number of error messages and
4253 warning messages generated.
4256 @cindex @option{-gnatU} (@code{gcc})
4257 This switch forces all error messages to be preceded by the unique
4258 string ``error:''. This means that error messages take a few more
4259 characters in space, but allows easy searching for and identification
4263 @cindex @option{-gnatb} (@code{gcc})
4265 The @code{b} stands for brief.
4267 This switch causes GNAT to generate the
4268 brief format error messages to @file{stderr} (the standard error
4269 file) as well as the verbose
4270 format message or full listing (which as usual is written to
4271 @file{stdout} (the standard output file).
4273 @item -gnatm^^=^@var{n}
4274 @cindex @option{-gnatm} (@code{gcc})
4276 The @code{m} stands for maximum.
4278 @var{n} is a decimal integer in the
4279 range of 1 to 999 and limits the number of error messages to be
4280 generated. For example, using @option{-gnatm2} might yield
4283 e.adb:3:04: Incorrect spelling of keyword "function"
4284 e.adb:5:35: missing ".."
4285 fatal error: maximum errors reached
4286 compilation abandoned
4290 @cindex @option{-gnatf} (@code{gcc})
4291 @cindex Error messages, suppressing
4293 The @code{f} stands for full.
4295 Normally, the compiler suppresses error messages that are likely to be
4296 redundant. This switch causes all error
4297 messages to be generated. In particular, in the case of
4298 references to undefined variables. If a given variable is referenced
4299 several times, the normal format of messages is
4301 e.adb:7:07: "V" is undefined (more references follow)
4305 where the parenthetical comment warns that there are additional
4306 references to the variable @code{V}. Compiling the same program with the
4307 @option{-gnatf} switch yields
4310 e.adb:7:07: "V" is undefined
4311 e.adb:8:07: "V" is undefined
4312 e.adb:8:12: "V" is undefined
4313 e.adb:8:16: "V" is undefined
4314 e.adb:9:07: "V" is undefined
4315 e.adb:9:12: "V" is undefined
4319 The @option{-gnatf} switch also generates additional information for
4320 some error messages. Some examples are:
4324 Full details on entities not available in high integrity mode
4326 Details on possibly non-portable unchecked conversion
4328 List possible interpretations for ambiguous calls
4330 Additional details on incorrect parameters
4335 @cindex @option{-gnatq} (@code{gcc})
4337 The @code{q} stands for quit (really ``don't quit'').
4339 In normal operation mode, the compiler first parses the program and
4340 determines if there are any syntax errors. If there are, appropriate
4341 error messages are generated and compilation is immediately terminated.
4343 GNAT to continue with semantic analysis even if syntax errors have been
4344 found. This may enable the detection of more errors in a single run. On
4345 the other hand, the semantic analyzer is more likely to encounter some
4346 internal fatal error when given a syntactically invalid tree.
4349 @cindex @option{-gnatQ} (@code{gcc})
4350 In normal operation mode, the @file{ALI} file is not generated if any
4351 illegalities are detected in the program. The use of @option{-gnatQ} forces
4352 generation of the @file{ALI} file. This file is marked as being in
4353 error, so it cannot be used for binding purposes, but it does contain
4354 reasonably complete cross-reference information, and thus may be useful
4355 for use by tools (e.g. semantic browsing tools or integrated development
4356 environments) that are driven from the @file{ALI} file. This switch
4357 implies @option{-gnatq}, since the semantic phase must be run to get a
4358 meaningful ALI file.
4360 In addition, if @option{-gnatt} is also specified, then the tree file is
4361 generated even if there are illegalities. It may be useful in this case
4362 to also specify @option{-gnatq} to ensure that full semantic processing
4363 occurs. The resulting tree file can be processed by ASIS, for the purpose
4364 of providing partial information about illegal units, but if the error
4365 causes the tree to be badly malformed, then ASIS may crash during the
4368 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4369 being in error, @code{gnatmake} will attempt to recompile the source when it
4370 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4372 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4373 since ALI files are never generated if @option{-gnats} is set.
4378 @node Warning Message Control
4379 @subsection Warning Message Control
4380 @cindex Warning messages
4382 In addition to error messages, which correspond to illegalities as defined
4383 in the Ada 95 Reference Manual, the compiler detects two kinds of warning
4386 First, the compiler considers some constructs suspicious and generates a
4387 warning message to alert you to a possible error. Second, if the
4388 compiler detects a situation that is sure to raise an exception at
4389 run time, it generates a warning message. The following shows an example
4390 of warning messages:
4392 e.adb:4:24: warning: creation of object may raise Storage_Error
4393 e.adb:10:17: warning: static value out of range
4394 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4398 GNAT considers a large number of situations as appropriate
4399 for the generation of warning messages. As always, warnings are not
4400 definite indications of errors. For example, if you do an out-of-range
4401 assignment with the deliberate intention of raising a
4402 @code{Constraint_Error} exception, then the warning that may be
4403 issued does not indicate an error. Some of the situations for which GNAT
4404 issues warnings (at least some of the time) are given in the following
4405 list. This list is not complete, and new warnings are often added to
4406 subsequent versions of GNAT. The list is intended to give a general idea
4407 of the kinds of warnings that are generated.
4411 Possible infinitely recursive calls
4414 Out-of-range values being assigned
4417 Possible order of elaboration problems
4423 Fixed-point type declarations with a null range
4426 Direct_IO or Sequential_IO instantiated with a type that has access values
4429 Variables that are never assigned a value
4432 Variables that are referenced before being initialized
4435 Task entries with no corresponding @code{accept} statement
4438 Duplicate accepts for the same task entry in a @code{select}
4441 Objects that take too much storage
4444 Unchecked conversion between types of differing sizes
4447 Missing @code{return} statement along some execution path in a function
4450 Incorrect (unrecognized) pragmas
4453 Incorrect external names
4456 Allocation from empty storage pool
4459 Potentially blocking operation in protected type
4462 Suspicious parenthesization of expressions
4465 Mismatching bounds in an aggregate
4468 Attempt to return local value by reference
4472 Premature instantiation of a generic body
4475 Attempt to pack aliased components
4478 Out of bounds array subscripts
4481 Wrong length on string assignment
4484 Violations of style rules if style checking is enabled
4487 Unused @code{with} clauses
4490 @code{Bit_Order} usage that does not have any effect
4493 @code{Standard.Duration} used to resolve universal fixed expression
4496 Dereference of possibly null value
4499 Declaration that is likely to cause storage error
4502 Internal GNAT unit @code{with}'ed by application unit
4505 Values known to be out of range at compile time
4508 Unreferenced labels and variables
4511 Address overlays that could clobber memory
4514 Unexpected initialization when address clause present
4517 Bad alignment for address clause
4520 Useless type conversions
4523 Redundant assignment statements and other redundant constructs
4526 Useless exception handlers
4529 Accidental hiding of name by child unit
4533 Access before elaboration detected at compile time
4536 A range in a @code{for} loop that is known to be null or might be null
4541 The following switches are available to control the handling of
4547 @emph{Activate all optional errors.}
4548 @cindex @option{-gnatwa} (@code{gcc})
4549 This switch activates most optional warning messages, see remaining list
4550 in this section for details on optional warning messages that can be
4551 individually controlled. The warnings that are not turned on by this
4553 @option{-gnatwd} (implicit dereferencing),
4554 @option{-gnatwh} (hiding),
4555 and @option{-gnatwl} (elaboration warnings).
4556 All other optional warnings are turned on.
4559 @emph{Suppress all optional errors.}
4560 @cindex @option{-gnatwA} (@code{gcc})
4561 This switch suppresses all optional warning messages, see remaining list
4562 in this section for details on optional warning messages that can be
4563 individually controlled.
4566 @emph{Activate warnings on conditionals.}
4567 @cindex @option{-gnatwc} (@code{gcc})
4568 @cindex Conditionals, constant
4569 This switch activates warnings for conditional expressions used in
4570 tests that are known to be True or False at compile time. The default
4571 is that such warnings are not generated.
4572 Note that this warning does
4573 not get issued for the use of boolean variables or constants whose
4574 values are known at compile time, since this is a standard technique
4575 for conditional compilation in Ada, and this would generate too many
4576 ``false positive'' warnings.
4577 This warning can also be turned on using @option{-gnatwa}.
4580 @emph{Suppress warnings on conditionals.}
4581 @cindex @option{-gnatwC} (@code{gcc})
4582 This switch suppresses warnings for conditional expressions used in
4583 tests that are known to be True or False at compile time.
4586 @emph{Activate warnings on implicit dereferencing.}
4587 @cindex @option{-gnatwd} (@code{gcc})
4588 If this switch is set, then the use of a prefix of an access type
4589 in an indexed component, slice, or selected component without an
4590 explicit @code{.all} will generate a warning. With this warning
4591 enabled, access checks occur only at points where an explicit
4592 @code{.all} appears in the source code (assuming no warnings are
4593 generated as a result of this switch). The default is that such
4594 warnings are not generated.
4595 Note that @option{-gnatwa} does not affect the setting of
4596 this warning option.
4599 @emph{Suppress warnings on implicit dereferencing.}
4600 @cindex @option{-gnatwD} (@code{gcc})
4601 @cindex Implicit dereferencing
4602 @cindex Dereferencing, implicit
4603 This switch suppresses warnings for implicit dereferences in
4604 indexed components, slices, and selected components.
4607 @emph{Treat warnings as errors.}
4608 @cindex @option{-gnatwe} (@code{gcc})
4609 @cindex Warnings, treat as error
4610 This switch causes warning messages to be treated as errors.
4611 The warning string still appears, but the warning messages are counted
4612 as errors, and prevent the generation of an object file.
4615 @emph{Activate warnings on unreferenced formals.}
4616 @cindex @option{-gnatwf} (@code{gcc})
4617 @cindex Formals, unreferenced
4618 This switch causes a warning to be generated if a formal parameter
4619 is not referenced in the body of the subprogram. This warning can
4620 also be turned on using @option{-gnatwa} or @option{-gnatwu}.
4623 @emph{Suppress warnings on unreferenced formals.}
4624 @cindex @option{-gnatwF} (@code{gcc})
4625 This switch suppresses warnings for unreferenced formal
4626 parameters. Note that the
4627 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4628 effect of warning on unreferenced entities other than subprogram
4632 @emph{Activate warnings on unrecognized pragmas.}
4633 @cindex @option{-gnatwg} (@code{gcc})
4634 @cindex Pragmas, unrecognized
4635 This switch causes a warning to be generated if an unrecognized
4636 pragma is encountered. Apart from issuing this warning, the
4637 pragma is ignored and has no effect. This warning can
4638 also be turned on using @option{-gnatwa}. The default
4639 is that such warnings are issued (satisfying the Ada Reference
4640 Manual requirement that such warnings appear).
4643 @emph{Suppress warnings on unrecognized pragmas.}
4644 @cindex @option{-gnatwG} (@code{gcc})
4645 This switch suppresses warnings for unrecognized pragmas.
4648 @emph{Activate warnings on hiding.}
4649 @cindex @option{-gnatwh} (@code{gcc})
4650 @cindex Hiding of Declarations
4651 This switch activates warnings on hiding declarations.
4652 A declaration is considered hiding
4653 if it is for a non-overloadable entity, and it declares an entity with the
4654 same name as some other entity that is directly or use-visible. The default
4655 is that such warnings are not generated.
4656 Note that @option{-gnatwa} does not affect the setting of this warning option.
4659 @emph{Suppress warnings on hiding.}
4660 @cindex @option{-gnatwH} (@code{gcc})
4661 This switch suppresses warnings on hiding declarations.
4664 @emph{Activate warnings on implementation units.}
4665 @cindex @option{-gnatwi} (@code{gcc})
4666 This switch activates warnings for a @code{with} of an internal GNAT
4667 implementation unit, defined as any unit from the @code{Ada},
4668 @code{Interfaces}, @code{GNAT},
4669 ^^@code{DEC},^ or @code{System}
4670 hierarchies that is not
4671 documented in either the Ada Reference Manual or the GNAT
4672 Programmer's Reference Manual. Such units are intended only
4673 for internal implementation purposes and should not be @code{with}'ed
4674 by user programs. The default is that such warnings are generated
4675 This warning can also be turned on using @option{-gnatwa}.
4678 @emph{Disable warnings on implementation units.}
4679 @cindex @option{-gnatwI} (@code{gcc})
4680 This switch disables warnings for a @code{with} of an internal GNAT
4681 implementation unit.
4684 @emph{Activate warnings on obsolescent features (Annex J).}
4685 @cindex @option{-gnatwj} (@code{gcc})
4686 @cindex Features, obsolescent
4687 @cindex Obsolescent features
4688 If this warning option is activated, then warnings are generated for
4689 calls to subprograms marked with @code{pragma Obsolescent} and
4690 for use of features in Annex J of the Ada Reference Manual. In the
4691 case of Annex J, not all features are flagged. In particular use
4692 of the renamed packages (like @code{Text_IO}) and use of package
4693 @code{ASCII} are not flagged, since these are very common and
4694 would generate many annoying positive warnings. The default is that
4695 such warnings are not generated.
4698 @emph{Suppress warnings on obsolescent features (Annex J).}
4699 @cindex @option{-gnatwJ} (@code{gcc})
4700 This switch disables warnings on use of obsolescent features.
4703 @emph{Activate warnings on variables that could be constants.}
4704 @cindex @option{-gnatwk} (@code{gcc})
4705 This switch activates warnings for variables that are initialized but
4706 never modified, and then could be declared constants.
4709 @emph{Suppress warnings on variables that could be constants.}
4710 @cindex @option{-gnatwK} (@code{gcc})
4711 This switch disables warnings on variables that could be declared constants.
4714 @emph{Activate warnings for missing elaboration pragmas.}
4715 @cindex @option{-gnatwl} (@code{gcc})
4716 @cindex Elaboration, warnings
4717 This switch activates warnings on missing
4718 @code{pragma Elaborate_All} statements.
4719 See the section in this guide on elaboration checking for details on
4720 when such pragma should be used. Warnings are also generated if you
4721 are using the static mode of elaboration, and a @code{pragma Elaborate}
4722 is encountered. The default is that such warnings
4724 This warning is not automatically turned on by the use of @option{-gnatwa}.
4727 @emph{Suppress warnings for missing elaboration pragmas.}
4728 @cindex @option{-gnatwL} (@code{gcc})
4729 This switch suppresses warnings on missing pragma Elaborate_All statements.
4730 See the section in this guide on elaboration checking for details on
4731 when such pragma should be used.
4734 @emph{Activate warnings on modified but unreferenced variables.}
4735 @cindex @option{-gnatwm} (@code{gcc})
4736 This switch activates warnings for variables that are assigned (using
4737 an initialization value or with one or more assignment statements) but
4738 whose value is never read. The warning is suppressed for volatile
4739 variables and also for variables that are renamings of other variables
4740 or for which an address clause is given.
4741 This warning can also be turned on using @option{-gnatwa}.
4744 @emph{Disable warnings on modified but unreferenced variables.}
4745 @cindex @option{-gnatwM} (@code{gcc})
4746 This switch disables warnings for variables that are assigned or
4747 initialized, but never read.
4750 @emph{Set normal warnings mode.}
4751 @cindex @option{-gnatwn} (@code{gcc})
4752 This switch sets normal warning mode, in which enabled warnings are
4753 issued and treated as warnings rather than errors. This is the default
4754 mode. the switch @option{-gnatwn} can be used to cancel the effect of
4755 an explicit @option{-gnatws} or
4756 @option{-gnatwe}. It also cancels the effect of the
4757 implicit @option{-gnatwe} that is activated by the
4758 use of @option{-gnatg}.
4761 @emph{Activate warnings on address clause overlays.}
4762 @cindex @option{-gnatwo} (@code{gcc})
4763 @cindex Address Clauses, warnings
4764 This switch activates warnings for possibly unintended initialization
4765 effects of defining address clauses that cause one variable to overlap
4766 another. The default is that such warnings are generated.
4767 This warning can also be turned on using @option{-gnatwa}.
4770 @emph{Suppress warnings on address clause overlays.}
4771 @cindex @option{-gnatwO} (@code{gcc})
4772 This switch suppresses warnings on possibly unintended initialization
4773 effects of defining address clauses that cause one variable to overlap
4777 @emph{Activate warnings on ineffective pragma Inlines.}
4778 @cindex @option{-gnatwp} (@code{gcc})
4779 @cindex Inlining, warnings
4780 This switch activates warnings for failure of front end inlining
4781 (activated by @option{-gnatN}) to inline a particular call. There are
4782 many reasons for not being able to inline a call, including most
4783 commonly that the call is too complex to inline.
4784 This warning can also be turned on using @option{-gnatwa}.
4787 @emph{Suppress warnings on ineffective pragma Inlines.}
4788 @cindex @option{-gnatwP} (@code{gcc})
4789 This switch suppresses warnings on ineffective pragma Inlines. If the
4790 inlining mechanism cannot inline a call, it will simply ignore the
4794 @emph{Activate warnings on redundant constructs.}
4795 @cindex @option{-gnatwr} (@code{gcc})
4796 This switch activates warnings for redundant constructs. The following
4797 is the current list of constructs regarded as redundant:
4798 This warning can also be turned on using @option{-gnatwa}.
4802 Assignment of an item to itself.
4804 Type conversion that converts an expression to its own type.
4806 Use of the attribute @code{Base} where @code{typ'Base} is the same
4809 Use of pragma @code{Pack} when all components are placed by a record
4810 representation clause.
4812 Exception handler containing only a reraise statement (raise with no
4813 operand) which has no effect.
4815 Use of the operator abs on an operand that is known at compile time
4818 Use of an unnecessary extra level of parentheses (C-style) around conditions
4819 in @code{if} statements, @code{while} statements and @code{exit} statements.
4821 Comparison of boolean expressions to an explicit True value.
4825 @emph{Suppress warnings on redundant constructs.}
4826 @cindex @option{-gnatwR} (@code{gcc})
4827 This switch suppresses warnings for redundant constructs.
4830 @emph{Suppress all warnings.}
4831 @cindex @option{-gnatws} (@code{gcc})
4832 This switch completely suppresses the
4833 output of all warning messages from the GNAT front end.
4834 Note that it does not suppress warnings from the @code{gcc} back end.
4835 To suppress these back end warnings as well, use the switch @option{-w}
4836 in addition to @option{-gnatws}.
4839 @emph{Activate warnings on unused entities.}
4840 @cindex @option{-gnatwu} (@code{gcc})
4841 This switch activates warnings to be generated for entities that
4842 are declared but not referenced, and for units that are @code{with}'ed
4844 referenced. In the case of packages, a warning is also generated if
4845 no entities in the package are referenced. This means that if the package
4846 is referenced but the only references are in @code{use}
4847 clauses or @code{renames}
4848 declarations, a warning is still generated. A warning is also generated
4849 for a generic package that is @code{with}'ed but never instantiated.
4850 In the case where a package or subprogram body is compiled, and there
4851 is a @code{with} on the corresponding spec
4852 that is only referenced in the body,
4853 a warning is also generated, noting that the
4854 @code{with} can be moved to the body. The default is that
4855 such warnings are not generated.
4856 This switch also activates warnings on unreferenced formals
4857 (it is includes the effect of @option{-gnatwf}).
4858 This warning can also be turned on using @option{-gnatwa}.
4861 @emph{Suppress warnings on unused entities.}
4862 @cindex @option{-gnatwU} (@code{gcc})
4863 This switch suppresses warnings for unused entities and packages.
4864 It also turns off warnings on unreferenced formals (and thus includes
4865 the effect of @option{-gnatwF}).
4868 @emph{Activate warnings on unassigned variables.}
4869 @cindex @option{-gnatwv} (@code{gcc})
4870 @cindex Unassigned variable warnings
4871 This switch activates warnings for access to variables which
4872 may not be properly initialized. The default is that
4873 such warnings are generated.
4876 @emph{Suppress warnings on unassigned variables.}
4877 @cindex @option{-gnatwV} (@code{gcc})
4878 This switch suppresses warnings for access to variables which
4879 may not be properly initialized.
4882 @emph{Activate warnings on Export/Import pragmas.}
4883 @cindex @option{-gnatwx} (@code{gcc})
4884 @cindex Export/Import pragma warnings
4885 This switch activates warnings on Export/Import pragmas when
4886 the compiler detects a possible conflict between the Ada and
4887 foreign language calling sequences. For example, the use of
4888 default parameters in a convention C procedure is dubious
4889 because the C compiler cannot supply the proper default, so
4890 a warning is issued. The default is that such warnings are
4894 @emph{Suppress warnings on Export/Import pragmas.}
4895 @cindex @option{-gnatwX} (@code{gcc})
4896 This switch suppresses warnings on Export/Import pragmas.
4897 The sense of this is that you are telling the compiler that
4898 you know what you are doing in writing the pragma, and it
4899 should not complain at you.
4902 @emph{Activate warnings on unchecked conversions.}
4903 @cindex @option{-gnatwz} (@code{gcc})
4904 @cindex Unchecked_Conversion warnings
4905 This switch activates warnings for unchecked conversions
4906 where the types are known at compile time to have different
4908 is that such warnings are generated.
4911 @emph{Suppress warnings on unchecked conversions.}
4912 @cindex @option{-gnatwZ} (@code{gcc})
4913 This switch suppresses warnings for unchecked conversions
4914 where the types are known at compile time to have different
4917 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
4918 @cindex @option{-Wuninitialized}
4919 The warnings controlled by the @option{-gnatw} switch are generated by the
4920 front end of the compiler. In some cases, the @option{^gcc^GCC^} back end
4921 can provide additional warnings. One such useful warning is provided by
4922 @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^}. This must be used in
4923 conjunction with tunrning on optimization mode. This causes the flow
4924 analysis circuits of the back end optimizer to output additional
4925 warnings about uninitialized variables.
4927 @item ^-w^/NO_BACK_END_WARNINGS^
4929 This switch suppresses warnings from the @option{^gcc^GCC^} back end. It may
4930 be used in conjunction with @option{-gnatws} to ensure that all warnings
4931 are suppressed during the entire compilation process.
4937 A string of warning parameters can be used in the same parameter. For example:
4944 will turn on all optional warnings except for elaboration pragma warnings,
4945 and also specify that warnings should be treated as errors.
4947 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
4973 @node Debugging and Assertion Control
4974 @subsection Debugging and Assertion Control
4978 @cindex @option{-gnata} (@code{gcc})
4984 The pragmas @code{Assert} and @code{Debug} normally have no effect and
4985 are ignored. This switch, where @samp{a} stands for assert, causes
4986 @code{Assert} and @code{Debug} pragmas to be activated.
4988 The pragmas have the form:
4992 @b{pragma} Assert (@var{Boolean-expression} [,
4993 @var{static-string-expression}])
4994 @b{pragma} Debug (@var{procedure call})
4999 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5000 If the result is @code{True}, the pragma has no effect (other than
5001 possible side effects from evaluating the expression). If the result is
5002 @code{False}, the exception @code{Assert_Failure} declared in the package
5003 @code{System.Assertions} is
5004 raised (passing @var{static-string-expression}, if present, as the
5005 message associated with the exception). If no string expression is
5006 given the default is a string giving the file name and line number
5009 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5010 @code{pragma Debug} may appear within a declaration sequence, allowing
5011 debugging procedures to be called between declarations.
5014 @item /DEBUG[=debug-level]
5016 Specifies how much debugging information is to be included in
5017 the resulting object file where 'debug-level' is one of the following:
5020 Include both debugger symbol records and traceback
5022 This is the default setting.
5024 Include both debugger symbol records and traceback in
5027 Excludes both debugger symbol records and traceback
5028 the object file. Same as /NODEBUG.
5030 Includes only debugger symbol records in the object
5031 file. Note that this doesn't include traceback information.
5036 @node Validity Checking
5037 @subsection Validity Checking
5038 @findex Validity Checking
5041 The Ada 95 Reference Manual has specific requirements for checking
5042 for invalid values. In particular, RM 13.9.1 requires that the
5043 evaluation of invalid values (for example from unchecked conversions),
5044 not result in erroneous execution. In GNAT, the result of such an
5045 evaluation in normal default mode is to either use the value
5046 unmodified, or to raise Constraint_Error in those cases where use
5047 of the unmodified value would cause erroneous execution. The cases
5048 where unmodified values might lead to erroneous execution are case
5049 statements (where a wild jump might result from an invalid value),
5050 and subscripts on the left hand side (where memory corruption could
5051 occur as a result of an invalid value).
5053 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5056 The @code{x} argument is a string of letters that
5057 indicate validity checks that are performed or not performed in addition
5058 to the default checks described above.
5061 The options allowed for this qualifier
5062 indicate validity checks that are performed or not performed in addition
5063 to the default checks described above.
5070 @emph{All validity checks.}
5071 @cindex @option{-gnatVa} (@code{gcc})
5072 All validity checks are turned on.
5074 That is, @option{-gnatVa} is
5075 equivalent to @option{gnatVcdfimorst}.
5079 @emph{Validity checks for copies.}
5080 @cindex @option{-gnatVc} (@code{gcc})
5081 The right hand side of assignments, and the initializing values of
5082 object declarations are validity checked.
5085 @emph{Default (RM) validity checks.}
5086 @cindex @option{-gnatVd} (@code{gcc})
5087 Some validity checks are done by default following normal Ada semantics
5089 A check is done in case statements that the expression is within the range
5090 of the subtype. If it is not, Constraint_Error is raised.
5091 For assignments to array components, a check is done that the expression used
5092 as index is within the range. If it is not, Constraint_Error is raised.
5093 Both these validity checks may be turned off using switch @option{-gnatVD}.
5094 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5095 switch @option{-gnatVd} will leave the checks turned on.
5096 Switch @option{-gnatVD} should be used only if you are sure that all such
5097 expressions have valid values. If you use this switch and invalid values
5098 are present, then the program is erroneous, and wild jumps or memory
5099 overwriting may occur.
5102 @emph{Validity checks for floating-point values.}
5103 @cindex @option{-gnatVf} (@code{gcc})
5104 In the absence of this switch, validity checking occurs only for discrete
5105 values. If @option{-gnatVf} is specified, then validity checking also applies
5106 for floating-point values, and NaN's and infinities are considered invalid,
5107 as well as out of range values for constrained types. Note that this means
5108 that standard @code{IEEE} infinity mode is not allowed. The exact contexts
5109 in which floating-point values are checked depends on the setting of other
5110 options. For example,
5111 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5112 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5113 (the order does not matter) specifies that floating-point parameters of mode
5114 @code{in} should be validity checked.
5117 @emph{Validity checks for @code{in} mode parameters}
5118 @cindex @option{-gnatVi} (@code{gcc})
5119 Arguments for parameters of mode @code{in} are validity checked in function
5120 and procedure calls at the point of call.
5123 @emph{Validity checks for @code{in out} mode parameters.}
5124 @cindex @option{-gnatVm} (@code{gcc})
5125 Arguments for parameters of mode @code{in out} are validity checked in
5126 procedure calls at the point of call. The @code{'m'} here stands for
5127 modify, since this concerns parameters that can be modified by the call.
5128 Note that there is no specific option to test @code{out} parameters,
5129 but any reference within the subprogram will be tested in the usual
5130 manner, and if an invalid value is copied back, any reference to it
5131 will be subject to validity checking.
5134 @emph{No validity checks.}
5135 @cindex @option{-gnatVn} (@code{gcc})
5136 This switch turns off all validity checking, including the default checking
5137 for case statements and left hand side subscripts. Note that the use of
5138 the switch @option{-gnatp} suppresses all run-time checks, including
5139 validity checks, and thus implies @option{-gnatVn}. When this switch
5140 is used, it cancels any other @option{-gnatV} previously issued.
5143 @emph{Validity checks for operator and attribute operands.}
5144 @cindex @option{-gnatVo} (@code{gcc})
5145 Arguments for predefined operators and attributes are validity checked.
5146 This includes all operators in package @code{Standard},
5147 the shift operators defined as intrinsic in package @code{Interfaces}
5148 and operands for attributes such as @code{Pos}. Checks are also made
5149 on individual component values for composite comparisons.
5152 @emph{Validity checks for parameters.}
5153 @cindex @option{-gnatVp} (@code{gcc})
5154 This controls the treatment of parameters within a subprogram (as opposed
5155 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5156 of parameters on a call. If either of these call options is used, then
5157 normally an assumption is made within a subprogram that the input arguments
5158 have been validity checking at the point of call, and do not need checking
5159 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5160 is not made, and parameters are not assumed to be valid, so their validity
5161 will be checked (or rechecked) within the subprogram.
5164 @emph{Validity checks for function returns.}
5165 @cindex @option{-gnatVr} (@code{gcc})
5166 The expression in @code{return} statements in functions is validity
5170 @emph{Validity checks for subscripts.}
5171 @cindex @option{-gnatVs} (@code{gcc})
5172 All subscripts expressions are checked for validity, whether they appear
5173 on the right side or left side (in default mode only left side subscripts
5174 are validity checked).
5177 @emph{Validity checks for tests.}
5178 @cindex @option{-gnatVt} (@code{gcc})
5179 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5180 statements are checked, as well as guard expressions in entry calls.
5185 The @option{-gnatV} switch may be followed by
5186 ^a string of letters^a list of options^
5187 to turn on a series of validity checking options.
5189 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5190 specifies that in addition to the default validity checking, copies and
5191 function return expressions are to be validity checked.
5192 In order to make it easier
5193 to specify the desired combination of effects,
5195 the upper case letters @code{CDFIMORST} may
5196 be used to turn off the corresponding lower case option.
5199 the prefix @code{NO} on an option turns off the corresponding validity
5202 @item @code{NOCOPIES}
5203 @item @code{NODEFAULT}
5204 @item @code{NOFLOATS}
5205 @item @code{NOIN_PARAMS}
5206 @item @code{NOMOD_PARAMS}
5207 @item @code{NOOPERANDS}
5208 @item @code{NORETURNS}
5209 @item @code{NOSUBSCRIPTS}
5210 @item @code{NOTESTS}
5214 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5215 turns on all validity checking options except for
5216 checking of @code{@b{in out}} procedure arguments.
5218 The specification of additional validity checking generates extra code (and
5219 in the case of @option{-gnatVa} the code expansion can be substantial.
5220 However, these additional checks can be very useful in detecting
5221 uninitialized variables, incorrect use of unchecked conversion, and other
5222 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5223 is useful in conjunction with the extra validity checking, since this
5224 ensures that wherever possible uninitialized variables have invalid values.
5226 See also the pragma @code{Validity_Checks} which allows modification of
5227 the validity checking mode at the program source level, and also allows for
5228 temporary disabling of validity checks.
5231 @node Style Checking
5232 @subsection Style Checking
5233 @findex Style checking
5236 The @option{-gnaty^x^(option,option,...)^} switch
5237 @cindex @option{-gnaty} (@code{gcc})
5238 causes the compiler to
5239 enforce specified style rules. A limited set of style rules has been used
5240 in writing the GNAT sources themselves. This switch allows user programs
5241 to activate all or some of these checks. If the source program fails a
5242 specified style check, an appropriate warning message is given, preceded by
5243 the character sequence ``(style)''.
5245 @code{(option,option,...)} is a sequence of keywords
5248 The string @var{x} is a sequence of letters or digits
5250 indicating the particular style
5251 checks to be performed. The following checks are defined:
5256 @emph{Specify indentation level.}
5257 If a digit from 1-9 appears
5258 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5259 then proper indentation is checked, with the digit indicating the
5260 indentation level required.
5261 The general style of required indentation is as specified by
5262 the examples in the Ada Reference Manual. Full line comments must be
5263 aligned with the @code{--} starting on a column that is a multiple of
5264 the alignment level.
5267 @emph{Check attribute casing.}
5268 If the ^letter a^word ATTRIBUTE^ appears in the string after @option{-gnaty}
5269 then attribute names, including the case of keywords such as @code{digits}
5270 used as attributes names, must be written in mixed case, that is, the
5271 initial letter and any letter following an underscore must be uppercase.
5272 All other letters must be lowercase.
5275 @emph{Blanks not allowed at statement end.}
5276 If the ^letter b^word BLANKS^ appears in the string after @option{-gnaty} then
5277 trailing blanks are not allowed at the end of statements. The purpose of this
5278 rule, together with h (no horizontal tabs), is to enforce a canonical format
5279 for the use of blanks to separate source tokens.
5282 @emph{Check comments.}
5283 If the ^letter c^word COMMENTS^ appears in the string after @option{-gnaty}
5284 then comments must meet the following set of rules:
5289 The ``@code{--}'' that starts the column must either start in column one,
5290 or else at least one blank must precede this sequence.
5293 Comments that follow other tokens on a line must have at least one blank
5294 following the ``@code{--}'' at the start of the comment.
5297 Full line comments must have two blanks following the ``@code{--}'' that
5298 starts the comment, with the following exceptions.
5301 A line consisting only of the ``@code{--}'' characters, possibly preceded
5302 by blanks is permitted.
5305 A comment starting with ``@code{--x}'' where @code{x} is a special character
5307 This allows proper processing of the output generated by specialized tools
5308 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5310 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5311 special character is defined as being in one of the ASCII ranges
5312 @code{16#21#..16#2F#} or @code{16#3A#..16#3F#}.
5313 Note that this usage is not permitted
5314 in GNAT implementation units (i.e. when @option{-gnatg} is used).
5317 A line consisting entirely of minus signs, possibly preceded by blanks, is
5318 permitted. This allows the construction of box comments where lines of minus
5319 signs are used to form the top and bottom of the box.
5322 If a comment starts and ends with ``@code{--}'' is permitted as long as at
5323 least one blank follows the initial ``@code{--}''. Together with the preceding
5324 rule, this allows the construction of box comments, as shown in the following
5327 ---------------------------
5328 -- This is a box comment --
5329 -- with two text lines. --
5330 ---------------------------
5335 @emph{Check end/exit labels.}
5336 If the ^letter e^word END^ appears in the string after @option{-gnaty} then
5337 optional labels on @code{end} statements ending subprograms and on
5338 @code{exit} statements exiting named loops, are required to be present.
5341 @emph{No form feeds or vertical tabs.}
5342 If the ^letter f^word VTABS^ appears in the string after @option{-gnaty} then
5343 neither form feeds nor vertical tab characters are not permitted
5347 @emph{No horizontal tabs.}
5348 If the ^letter h^word HTABS^ appears in the string after @option{-gnaty} then
5349 horizontal tab characters are not permitted in the source text.
5350 Together with the b (no blanks at end of line) check, this
5351 enforces a canonical form for the use of blanks to separate
5355 @emph{Check if-then layout.}
5356 If the ^letter i^word IF_THEN^ appears in the string after @option{-gnaty},
5357 then the keyword @code{then} must appear either on the same
5358 line as corresponding @code{if}, or on a line on its own, lined
5359 up under the @code{if} with at least one non-blank line in between
5360 containing all or part of the condition to be tested.
5363 @emph{Check keyword casing.}
5364 If the ^letter k^word KEYWORD^ appears in the string after @option{-gnaty} then
5365 all keywords must be in lower case (with the exception of keywords
5366 such as @code{digits} used as attribute names to which this check
5370 @emph{Check layout.}
5371 If the ^letter l^word LAYOUT^ appears in the string after @option{-gnaty} then
5372 layout of statement and declaration constructs must follow the
5373 recommendations in the Ada Reference Manual, as indicated by the
5374 form of the syntax rules. For example an @code{else} keyword must
5375 be lined up with the corresponding @code{if} keyword.
5377 There are two respects in which the style rule enforced by this check
5378 option are more liberal than those in the Ada Reference Manual. First
5379 in the case of record declarations, it is permissible to put the
5380 @code{record} keyword on the same line as the @code{type} keyword, and
5381 then the @code{end} in @code{end record} must line up under @code{type}.
5382 For example, either of the following two layouts is acceptable:
5384 @smallexample @c ada
5400 Second, in the case of a block statement, a permitted alternative
5401 is to put the block label on the same line as the @code{declare} or
5402 @code{begin} keyword, and then line the @code{end} keyword up under
5403 the block label. For example both the following are permitted:
5405 @smallexample @c ada
5423 The same alternative format is allowed for loops. For example, both of
5424 the following are permitted:
5426 @smallexample @c ada
5428 Clear : while J < 10 loop
5439 @item ^Lnnn^MAX_NESTING=nnn^
5440 @emph{Set maximum nesting level}
5441 If the sequence ^Lnnn^MAX_NESTING=nnn^, where nnn is a decimal number in
5442 the range 0-999, appears in the string after @option{-gnaty} then the
5443 maximum level of nesting of constructs (including subprograms, loops,
5444 blocks, packages, and conditionals) may not exceed the given value. A
5445 value of zero disconnects this style check.
5447 @item ^m^LINE_LENGTH^
5448 @emph{Check maximum line length.}
5449 If the ^letter m^word LINE_LENGTH^ appears in the string after @option{-gnaty}
5450 then the length of source lines must not exceed 79 characters, including
5451 any trailing blanks. The value of 79 allows convenient display on an
5452 80 character wide device or window, allowing for possible special
5453 treatment of 80 character lines. Note that this count is of raw
5454 characters in the source text. This means that a tab character counts
5455 as one character in this count and a wide character sequence counts as
5456 several characters (however many are needed in the encoding).
5458 @item ^Mnnn^MAX_LENGTH=nnn^
5459 @emph{Set maximum line length.}
5460 If the sequence ^M^MAX_LENGTH=^nnn, where nnn is a decimal number, appears in
5461 the string after @option{-gnaty} then the length of lines must not exceed the
5464 @item ^n^STANDARD_CASING^
5465 @emph{Check casing of entities in Standard.}
5466 If the ^letter n^word STANDARD_CASING^ appears in the string
5467 after @option{-gnaty} then any identifier from Standard must be cased
5468 to match the presentation in the Ada Reference Manual (for example,
5469 @code{Integer} and @code{ASCII.NUL}).
5471 @item ^o^ORDERED_SUBPROGRAMS^
5472 @emph{Check order of subprogram bodies.}
5473 If the ^letter o^word ORDERED_SUBPROGRAMS^ appears in the string
5474 after @option{-gnaty} then all subprogram bodies in a given scope
5475 (e.g. a package body) must be in alphabetical order. The ordering
5476 rule uses normal Ada rules for comparing strings, ignoring casing
5477 of letters, except that if there is a trailing numeric suffix, then
5478 the value of this suffix is used in the ordering (e.g. Junk2 comes
5482 @emph{Check pragma casing.}
5483 If the ^letter p^word PRAGMA^ appears in the string after @option{-gnaty} then
5484 pragma names must be written in mixed case, that is, the
5485 initial letter and any letter following an underscore must be uppercase.
5486 All other letters must be lowercase.
5488 @item ^r^REFERENCES^
5489 @emph{Check references.}
5490 If the ^letter r^word REFERENCES^ appears in the string after @option{-gnaty}
5491 then all identifier references must be cased in the same way as the
5492 corresponding declaration. No specific casing style is imposed on
5493 identifiers. The only requirement is for consistency of references
5497 @emph{Check separate specs.}
5498 If the ^letter s^word SPECS^ appears in the string after @option{-gnaty} then
5499 separate declarations (``specs'') are required for subprograms (a
5500 body is not allowed to serve as its own declaration). The only
5501 exception is that parameterless library level procedures are
5502 not required to have a separate declaration. This exception covers
5503 the most frequent form of main program procedures.
5506 @emph{Check token spacing.}
5507 If the ^letter t^word TOKEN^ appears in the string after @option{-gnaty} then
5508 the following token spacing rules are enforced:
5513 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
5516 The token @code{=>} must be surrounded by spaces.
5519 The token @code{<>} must be preceded by a space or a left parenthesis.
5522 Binary operators other than @code{**} must be surrounded by spaces.
5523 There is no restriction on the layout of the @code{**} binary operator.
5526 Colon must be surrounded by spaces.
5529 Colon-equal (assignment, initialization) must be surrounded by spaces.
5532 Comma must be the first non-blank character on the line, or be
5533 immediately preceded by a non-blank character, and must be followed
5537 If the token preceding a left parenthesis ends with a letter or digit, then
5538 a space must separate the two tokens.
5541 A right parenthesis must either be the first non-blank character on
5542 a line, or it must be preceded by a non-blank character.
5545 A semicolon must not be preceded by a space, and must not be followed by
5546 a non-blank character.
5549 A unary plus or minus may not be followed by a space.
5552 A vertical bar must be surrounded by spaces.
5556 In the above rules, appearing in column one is always permitted, that is,
5557 counts as meeting either a requirement for a required preceding space,
5558 or as meeting a requirement for no preceding space.
5560 Appearing at the end of a line is also always permitted, that is, counts
5561 as meeting either a requirement for a following space, or as meeting
5562 a requirement for no following space.
5567 If any of these style rules is violated, a message is generated giving
5568 details on the violation. The initial characters of such messages are
5569 always ``@code{(style)}''. Note that these messages are treated as warning
5570 messages, so they normally do not prevent the generation of an object
5571 file. The @option{-gnatwe} switch can be used to treat warning messages,
5572 including style messages, as fatal errors.
5576 @option{-gnaty} on its own (that is not
5577 followed by any letters or digits),
5578 is equivalent to @code{gnaty3abcefhiklmprst}, that is all checking
5579 options enabled with the exception of -gnatyo,
5582 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
5583 the exception of ORDERED_SUBPROGRAMS,
5585 with an indentation level of 3. This is the standard
5586 checking option that is used for the GNAT sources.
5595 clears any previously set style checks.
5597 @node Run-Time Checks
5598 @subsection Run-Time Checks
5599 @cindex Division by zero
5600 @cindex Access before elaboration
5601 @cindex Checks, division by zero
5602 @cindex Checks, access before elaboration
5605 If you compile with the default options, GNAT will insert many run-time
5606 checks into the compiled code, including code that performs range
5607 checking against constraints, but not arithmetic overflow checking for
5608 integer operations (including division by zero) or checks for access
5609 before elaboration on subprogram calls. All other run-time checks, as
5610 required by the Ada 95 Reference Manual, are generated by default.
5611 The following @code{gcc} switches refine this default behavior:
5616 @cindex @option{-gnatp} (@code{gcc})
5617 @cindex Suppressing checks
5618 @cindex Checks, suppressing
5620 Suppress all run-time checks as though @code{pragma Suppress (all_checks})
5621 had been present in the source. Validity checks are also suppressed (in
5622 other words @option{-gnatp} also implies @option{-gnatVn}.
5623 Use this switch to improve the performance
5624 of the code at the expense of safety in the presence of invalid data or
5628 @cindex @option{-gnato} (@code{gcc})
5629 @cindex Overflow checks
5630 @cindex Check, overflow
5631 Enables overflow checking for integer operations.
5632 This causes GNAT to generate slower and larger executable
5633 programs by adding code to check for overflow (resulting in raising
5634 @code{Constraint_Error} as required by standard Ada
5635 semantics). These overflow checks correspond to situations in which
5636 the true value of the result of an operation may be outside the base
5637 range of the result type. The following example shows the distinction:
5639 @smallexample @c ada
5640 X1 : Integer := Integer'Last;
5641 X2 : Integer range 1 .. 5 := 5;
5642 X3 : Integer := Integer'Last;
5643 X4 : Integer range 1 .. 5 := 5;
5644 F : Float := 2.0E+20;
5653 Here the first addition results in a value that is outside the base range
5654 of Integer, and hence requires an overflow check for detection of the
5655 constraint error. Thus the first assignment to @code{X1} raises a
5656 @code{Constraint_Error} exception only if @option{-gnato} is set.
5658 The second increment operation results in a violation
5659 of the explicit range constraint, and such range checks are always
5660 performed (unless specifically suppressed with a pragma @code{suppress}
5661 or the use of @option{-gnatp}).
5663 The two conversions of @code{F} both result in values that are outside
5664 the base range of type @code{Integer} and thus will raise
5665 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
5666 The fact that the result of the second conversion is assigned to
5667 variable @code{X4} with a restricted range is irrelevant, since the problem
5668 is in the conversion, not the assignment.
5670 Basically the rule is that in the default mode (@option{-gnato} not
5671 used), the generated code assures that all integer variables stay
5672 within their declared ranges, or within the base range if there is
5673 no declared range. This prevents any serious problems like indexes
5674 out of range for array operations.
5676 What is not checked in default mode is an overflow that results in
5677 an in-range, but incorrect value. In the above example, the assignments
5678 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
5679 range of the target variable, but the result is wrong in the sense that
5680 it is too large to be represented correctly. Typically the assignment
5681 to @code{X1} will result in wrap around to the largest negative number.
5682 The conversions of @code{F} will result in some @code{Integer} value
5683 and if that integer value is out of the @code{X4} range then the
5684 subsequent assignment would generate an exception.
5686 @findex Machine_Overflows
5687 Note that the @option{-gnato} switch does not affect the code generated
5688 for any floating-point operations; it applies only to integer
5690 For floating-point, GNAT has the @code{Machine_Overflows}
5691 attribute set to @code{False} and the normal mode of operation is to
5692 generate IEEE NaN and infinite values on overflow or invalid operations
5693 (such as dividing 0.0 by 0.0).
5695 The reason that we distinguish overflow checking from other kinds of
5696 range constraint checking is that a failure of an overflow check can
5697 generate an incorrect value, but cannot cause erroneous behavior. This
5698 is unlike the situation with a constraint check on an array subscript,
5699 where failure to perform the check can result in random memory description,
5700 or the range check on a case statement, where failure to perform the check
5701 can cause a wild jump.
5703 Note again that @option{-gnato} is off by default, so overflow checking is
5704 not performed in default mode. This means that out of the box, with the
5705 default settings, GNAT does not do all the checks expected from the
5706 language description in the Ada Reference Manual. If you want all constraint
5707 checks to be performed, as described in this Manual, then you must
5708 explicitly use the -gnato switch either on the @code{gnatmake} or
5712 @cindex @option{-gnatE} (@code{gcc})
5713 @cindex Elaboration checks
5714 @cindex Check, elaboration
5715 Enables dynamic checks for access-before-elaboration
5716 on subprogram calls and generic instantiations.
5717 For full details of the effect and use of this switch,
5718 @xref{Compiling Using gcc}.
5723 The setting of these switches only controls the default setting of the
5724 checks. You may modify them using either @code{Suppress} (to remove
5725 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
5728 @node Stack Overflow Checking
5729 @subsection Stack Overflow Checking
5730 @cindex Stack Overflow Checking
5731 @cindex -fstack-check
5734 For most operating systems, @code{gcc} does not perform stack overflow
5735 checking by default. This means that if the main environment task or
5736 some other task exceeds the available stack space, then unpredictable
5737 behavior will occur.
5739 To activate stack checking, compile all units with the gcc option
5740 @option{-fstack-check}. For example:
5743 gcc -c -fstack-check package1.adb
5747 Units compiled with this option will generate extra instructions to check
5748 that any use of the stack (for procedure calls or for declaring local
5749 variables in declare blocks) do not exceed the available stack space.
5750 If the space is exceeded, then a @code{Storage_Error} exception is raised.
5752 For declared tasks, the stack size is always controlled by the size
5753 given in an applicable @code{Storage_Size} pragma (or is set to
5754 the default size if no pragma is used.
5756 For the environment task, the stack size depends on
5757 system defaults and is unknown to the compiler. The stack
5758 may even dynamically grow on some systems, precluding the
5759 normal Ada semantics for stack overflow. In the worst case,
5760 unbounded stack usage, causes unbounded stack expansion
5761 resulting in the system running out of virtual memory.
5763 The stack checking may still work correctly if a fixed
5764 size stack is allocated, but this cannot be guaranteed.
5765 To ensure that a clean exception is signalled for stack
5766 overflow, set the environment variable
5767 @code{GNAT_STACK_LIMIT} to indicate the maximum
5768 stack area that can be used, as in:
5769 @cindex GNAT_STACK_LIMIT
5772 SET GNAT_STACK_LIMIT 1600
5776 The limit is given in kilobytes, so the above declaration would
5777 set the stack limit of the environment task to 1.6 megabytes.
5778 Note that the only purpose of this usage is to limit the amount
5779 of stack used by the environment task. If it is necessary to
5780 increase the amount of stack for the environment task, then this
5781 is an operating systems issue, and must be addressed with the
5782 appropriate operating systems commands.
5785 @node Using gcc for Syntax Checking
5786 @subsection Using @code{gcc} for Syntax Checking
5789 @cindex @option{-gnats} (@code{gcc})
5793 The @code{s} stands for ``syntax''.
5796 Run GNAT in syntax checking only mode. For
5797 example, the command
5800 $ gcc -c -gnats x.adb
5804 compiles file @file{x.adb} in syntax-check-only mode. You can check a
5805 series of files in a single command
5807 , and can use wild cards to specify such a group of files.
5808 Note that you must specify the @option{-c} (compile
5809 only) flag in addition to the @option{-gnats} flag.
5812 You may use other switches in conjunction with @option{-gnats}. In
5813 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
5814 format of any generated error messages.
5816 When the source file is empty or contains only empty lines and/or comments,
5817 the output is a warning:
5820 $ gcc -c -gnats -x ada toto.txt
5821 toto.txt:1:01: warning: empty file, contains no compilation units
5825 Otherwise, the output is simply the error messages, if any. No object file or
5826 ALI file is generated by a syntax-only compilation. Also, no units other
5827 than the one specified are accessed. For example, if a unit @code{X}
5828 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
5829 check only mode does not access the source file containing unit
5832 @cindex Multiple units, syntax checking
5833 Normally, GNAT allows only a single unit in a source file. However, this
5834 restriction does not apply in syntax-check-only mode, and it is possible
5835 to check a file containing multiple compilation units concatenated
5836 together. This is primarily used by the @code{gnatchop} utility
5837 (@pxref{Renaming Files Using gnatchop}).
5841 @node Using gcc for Semantic Checking
5842 @subsection Using @code{gcc} for Semantic Checking
5845 @cindex @option{-gnatc} (@code{gcc})
5849 The @code{c} stands for ``check''.
5851 Causes the compiler to operate in semantic check mode,
5852 with full checking for all illegalities specified in the
5853 Ada 95 Reference Manual, but without generation of any object code
5854 (no object file is generated).
5856 Because dependent files must be accessed, you must follow the GNAT
5857 semantic restrictions on file structuring to operate in this mode:
5861 The needed source files must be accessible
5862 (@pxref{Search Paths and the Run-Time Library (RTL)}).
5865 Each file must contain only one compilation unit.
5868 The file name and unit name must match (@pxref{File Naming Rules}).
5871 The output consists of error messages as appropriate. No object file is
5872 generated. An @file{ALI} file is generated for use in the context of
5873 cross-reference tools, but this file is marked as not being suitable
5874 for binding (since no object file is generated).
5875 The checking corresponds exactly to the notion of
5876 legality in the Ada 95 Reference Manual.
5878 Any unit can be compiled in semantics-checking-only mode, including
5879 units that would not normally be compiled (subunits,
5880 and specifications where a separate body is present).
5883 @node Compiling Ada 83 Programs
5884 @subsection Compiling Ada 83 Programs
5886 @cindex Ada 83 compatibility
5888 @cindex @option{-gnat83} (@code{gcc})
5889 @cindex ACVC, Ada 83 tests
5892 Although GNAT is primarily an Ada 95 compiler, it accepts this switch to
5893 specify that an Ada 83 program is to be compiled in Ada 83 mode. If you specify
5894 this switch, GNAT rejects most Ada 95 extensions and applies Ada 83 semantics
5895 where this can be done easily.
5896 It is not possible to guarantee this switch does a perfect
5897 job; for example, some subtle tests, such as are
5898 found in earlier ACVC tests (and that have been removed from the ACATS suite
5899 for Ada 95), might not compile correctly.
5900 Nevertheless, this switch may be useful in some circumstances, for example
5901 where, due to contractual reasons, legacy code needs to be maintained
5902 using only Ada 83 features.
5904 With few exceptions (most notably the need to use @code{<>} on
5905 @cindex Generic formal parameters
5906 unconstrained generic formal parameters, the use of the new Ada 95
5907 reserved words, and the use of packages
5908 with optional bodies), it is not necessary to use the
5909 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
5910 exceptions, Ada 95 is upwardly compatible with Ada 83. This
5911 means that a correct Ada 83 program is usually also a correct Ada 95
5913 For further information, please refer to @ref{Compatibility and Porting Guide}.
5917 @node Character Set Control
5918 @subsection Character Set Control
5920 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
5921 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
5924 Normally GNAT recognizes the Latin-1 character set in source program
5925 identifiers, as described in the Ada 95 Reference Manual.
5927 GNAT to recognize alternate character sets in identifiers. @var{c} is a
5928 single character ^^or word^ indicating the character set, as follows:
5932 ISO 8859-1 (Latin-1) identifiers
5935 ISO 8859-2 (Latin-2) letters allowed in identifiers
5938 ISO 8859-3 (Latin-3) letters allowed in identifiers
5941 ISO 8859-4 (Latin-4) letters allowed in identifiers
5944 ISO 8859-5 (Cyrillic) letters allowed in identifiers
5947 ISO 8859-15 (Latin-9) letters allowed in identifiers
5950 IBM PC letters (code page 437) allowed in identifiers
5953 IBM PC letters (code page 850) allowed in identifiers
5955 @item ^f^FULL_UPPER^
5956 Full upper-half codes allowed in identifiers
5959 No upper-half codes allowed in identifiers
5962 Wide-character codes (that is, codes greater than 255)
5963 allowed in identifiers
5966 @xref{Foreign Language Representation}, for full details on the
5967 implementation of these character sets.
5969 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
5970 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
5971 Specify the method of encoding for wide characters.
5972 @var{e} is one of the following:
5977 Hex encoding (brackets coding also recognized)
5980 Upper half encoding (brackets encoding also recognized)
5983 Shift/JIS encoding (brackets encoding also recognized)
5986 EUC encoding (brackets encoding also recognized)
5989 UTF-8 encoding (brackets encoding also recognized)
5992 Brackets encoding only (default value)
5994 For full details on the these encoding
5995 methods see @xref{Wide Character Encodings}.
5996 Note that brackets coding is always accepted, even if one of the other
5997 options is specified, so for example @option{-gnatW8} specifies that both
5998 brackets and @code{UTF-8} encodings will be recognized. The units that are
5999 with'ed directly or indirectly will be scanned using the specified
6000 representation scheme, and so if one of the non-brackets scheme is
6001 used, it must be used consistently throughout the program. However,
6002 since brackets encoding is always recognized, it may be conveniently
6003 used in standard libraries, allowing these libraries to be used with
6004 any of the available coding schemes.
6005 scheme. If no @option{-gnatW?} parameter is present, then the default
6006 representation is Brackets encoding only.
6008 Note that the wide character representation that is specified (explicitly
6009 or by default) for the main program also acts as the default encoding used
6010 for Wide_Text_IO files if not specifically overridden by a WCEM form
6014 @node File Naming Control
6015 @subsection File Naming Control
6018 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6019 @cindex @option{-gnatk} (@code{gcc})
6020 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6021 1-999, indicates the maximum allowable length of a file name (not
6022 including the @file{.ads} or @file{.adb} extension). The default is not
6023 to enable file name krunching.
6025 For the source file naming rules, @xref{File Naming Rules}.
6029 @node Subprogram Inlining Control
6030 @subsection Subprogram Inlining Control
6035 @cindex @option{-gnatn} (@code{gcc})
6037 The @code{n} here is intended to suggest the first syllable of the
6040 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6041 inlining to actually occur, optimization must be enabled. To enable
6042 inlining of subprograms specified by pragma @code{Inline},
6043 you must also specify this switch.
6044 In the absence of this switch, GNAT does not attempt
6045 inlining and does not need to access the bodies of
6046 subprograms for which @code{pragma Inline} is specified if they are not
6047 in the current unit.
6049 If you specify this switch the compiler will access these bodies,
6050 creating an extra source dependency for the resulting object file, and
6051 where possible, the call will be inlined.
6052 For further details on when inlining is possible
6053 see @xref{Inlining of Subprograms}.
6056 @cindex @option{-gnatN} (@code{gcc})
6057 The front end inlining activated by this switch is generally more extensive,
6058 and quite often more effective than the standard @option{-gnatn} inlining mode.
6059 It will also generate additional dependencies.
6061 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
6062 to specify both options.
6065 @node Auxiliary Output Control
6066 @subsection Auxiliary Output Control
6070 @cindex @option{-gnatt} (@code{gcc})
6071 @cindex Writing internal trees
6072 @cindex Internal trees, writing to file
6073 Causes GNAT to write the internal tree for a unit to a file (with the
6074 extension @file{.adt}.
6075 This not normally required, but is used by separate analysis tools.
6077 these tools do the necessary compilations automatically, so you should
6078 not have to specify this switch in normal operation.
6081 @cindex @option{-gnatu} (@code{gcc})
6082 Print a list of units required by this compilation on @file{stdout}.
6083 The listing includes all units on which the unit being compiled depends
6084 either directly or indirectly.
6087 @item -pass-exit-codes
6088 @cindex @option{-pass-exit-codes} (@code{gcc})
6089 If this switch is not used, the exit code returned by @code{gcc} when
6090 compiling multiple files indicates whether all source files have
6091 been successfully used to generate object files or not.
6093 When @option{-pass-exit-codes} is used, @code{gcc} exits with an extended
6094 exit status and allows an integrated development environment to better
6095 react to a compilation failure. Those exit status are:
6099 There was an error in at least one source file.
6101 At least one source file did not generate an object file.
6103 The compiler died unexpectedly (internal error for example).
6105 An object file has been generated for every source file.
6110 @node Debugging Control
6111 @subsection Debugging Control
6115 @cindex Debugging options
6118 @cindex @option{-gnatd} (@code{gcc})
6119 Activate internal debugging switches. @var{x} is a letter or digit, or
6120 string of letters or digits, which specifies the type of debugging
6121 outputs desired. Normally these are used only for internal development
6122 or system debugging purposes. You can find full documentation for these
6123 switches in the body of the @code{Debug} unit in the compiler source
6124 file @file{debug.adb}.
6128 @cindex @option{-gnatG} (@code{gcc})
6129 This switch causes the compiler to generate auxiliary output containing
6130 a pseudo-source listing of the generated expanded code. Like most Ada
6131 compilers, GNAT works by first transforming the high level Ada code into
6132 lower level constructs. For example, tasking operations are transformed
6133 into calls to the tasking run-time routines. A unique capability of GNAT
6134 is to list this expanded code in a form very close to normal Ada source.
6135 This is very useful in understanding the implications of various Ada
6136 usage on the efficiency of the generated code. There are many cases in
6137 Ada (e.g. the use of controlled types), where simple Ada statements can
6138 generate a lot of run-time code. By using @option{-gnatG} you can identify
6139 these cases, and consider whether it may be desirable to modify the coding
6140 approach to improve efficiency.
6142 The format of the output is very similar to standard Ada source, and is
6143 easily understood by an Ada programmer. The following special syntactic
6144 additions correspond to low level features used in the generated code that
6145 do not have any exact analogies in pure Ada source form. The following
6146 is a partial list of these special constructions. See the specification
6147 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6150 @item new @var{xxx} [storage_pool = @var{yyy}]
6151 Shows the storage pool being used for an allocator.
6153 @item at end @var{procedure-name};
6154 Shows the finalization (cleanup) procedure for a scope.
6156 @item (if @var{expr} then @var{expr} else @var{expr})
6157 Conditional expression equivalent to the @code{x?y:z} construction in C.
6159 @item @var{target}^^^(@var{source})
6160 A conversion with floating-point truncation instead of rounding.
6162 @item @var{target}?(@var{source})
6163 A conversion that bypasses normal Ada semantic checking. In particular
6164 enumeration types and fixed-point types are treated simply as integers.
6166 @item @var{target}?^^^(@var{source})
6167 Combines the above two cases.
6169 @item @var{x} #/ @var{y}
6170 @itemx @var{x} #mod @var{y}
6171 @itemx @var{x} #* @var{y}
6172 @itemx @var{x} #rem @var{y}
6173 A division or multiplication of fixed-point values which are treated as
6174 integers without any kind of scaling.
6176 @item free @var{expr} [storage_pool = @var{xxx}]
6177 Shows the storage pool associated with a @code{free} statement.
6179 @item freeze @var{typename} [@var{actions}]
6180 Shows the point at which @var{typename} is frozen, with possible
6181 associated actions to be performed at the freeze point.
6183 @item reference @var{itype}
6184 Reference (and hence definition) to internal type @var{itype}.
6186 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6187 Intrinsic function call.
6189 @item @var{labelname} : label
6190 Declaration of label @var{labelname}.
6192 @item @var{expr} && @var{expr} && @var{expr} ... && @var{expr}
6193 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6194 @var{expr}, but handled more efficiently).
6196 @item [constraint_error]
6197 Raise the @code{Constraint_Error} exception.
6199 @item @var{expression}'reference
6200 A pointer to the result of evaluating @var{expression}.
6202 @item @var{target-type}!(@var{source-expression})
6203 An unchecked conversion of @var{source-expression} to @var{target-type}.
6205 @item [@var{numerator}/@var{denominator}]
6206 Used to represent internal real literals (that) have no exact
6207 representation in base 2-16 (for example, the result of compile time
6208 evaluation of the expression 1.0/27.0).
6212 @cindex @option{-gnatD} (@code{gcc})
6213 When used in conjunction with @option{-gnatG}, this switch causes
6214 the expanded source, as described above for
6215 @option{-gnatG} to be written to files with names
6216 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6217 instead of to the standard ooutput file. For
6218 example, if the source file name is @file{hello.adb}, then a file
6219 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6220 information generated by the @code{gcc} @option{^-g^/DEBUG^} switch
6221 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6222 you to do source level debugging using the generated code which is
6223 sometimes useful for complex code, for example to find out exactly
6224 which part of a complex construction raised an exception. This switch
6225 also suppress generation of cross-reference information (see
6226 @option{-gnatx}) since otherwise the cross-reference information
6227 would refer to the @file{^.dg^.DG^} file, which would cause
6228 confusion since this is not the original source file.
6230 Note that @option{-gnatD} actually implies @option{-gnatG}
6231 automatically, so it is not necessary to give both options.
6232 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6235 @item -gnatR[0|1|2|3[s]]
6236 @cindex @option{-gnatR} (@code{gcc})
6237 This switch controls output from the compiler of a listing showing
6238 representation information for declared types and objects. For
6239 @option{-gnatR0}, no information is output (equivalent to omitting
6240 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6241 so @option{-gnatR} with no parameter has the same effect), size and alignment
6242 information is listed for declared array and record types. For
6243 @option{-gnatR2}, size and alignment information is listed for all
6244 expression information for values that are computed at run time for
6245 variant records. These symbolic expressions have a mostly obvious
6246 format with #n being used to represent the value of the n'th
6247 discriminant. See source files @file{repinfo.ads/adb} in the
6248 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6249 output. If the switch is followed by an s (e.g. @option{-gnatR2s}), then
6250 the output is to a file with the name @file{^file.rep^file_REP^} where
6251 file is the name of the corresponding source file.
6254 @item /REPRESENTATION_INFO
6255 @cindex @option{/REPRESENTATION_INFO} (@code{gcc})
6256 This qualifier controls output from the compiler of a listing showing
6257 representation information for declared types and objects. For
6258 @option{/REPRESENTATION_INFO=NONE}, no information is output
6259 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6260 @option{/REPRESENTATION_INFO} without option is equivalent to
6261 @option{/REPRESENTATION_INFO=ARRAYS}.
6262 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6263 information is listed for declared array and record types. For
6264 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6265 is listed for all expression information for values that are computed
6266 at run time for variant records. These symbolic expressions have a mostly
6267 obvious format with #n being used to represent the value of the n'th
6268 discriminant. See source files @file{REPINFO.ADS/ADB} in the
6269 @code{GNAT} sources for full details on the format of
6270 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
6271 If _FILE is added at the end of an option
6272 (e.g. @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
6273 then the output is to a file with the name @file{file_REP} where
6274 file is the name of the corresponding source file.
6278 @cindex @option{-gnatS} (@code{gcc})
6279 The use of the switch @option{-gnatS} for an
6280 Ada compilation will cause the compiler to output a
6281 representation of package Standard in a form very
6282 close to standard Ada. It is not quite possible to
6283 do this entirely in standard Ada (since new
6284 numeric base types cannot be created in standard
6285 Ada), but the output is easily
6286 readable to any Ada programmer, and is useful to
6287 determine the characteristics of target dependent
6288 types in package Standard.
6291 @cindex @option{-gnatx} (@code{gcc})
6292 Normally the compiler generates full cross-referencing information in
6293 the @file{ALI} file. This information is used by a number of tools,
6294 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
6295 suppresses this information. This saves some space and may slightly
6296 speed up compilation, but means that these tools cannot be used.
6299 @node Exception Handling Control
6300 @subsection Exception Handling Control
6303 GNAT uses two methods for handling exceptions at run-time. The
6304 @code{longjmp/setjmp} method saves the context when entering
6305 a frame with an exception handler. Then when an exception is
6306 raised, the context can be restored immediately, without the
6307 need for tracing stack frames. This method provides very fast
6308 exception propagation, but introduces significant overhead for
6309 the use of exception handlers, even if no exception is raised.
6311 The other approach is called ``zero cost'' exception handling.
6312 With this method, the compiler builds static tables to describe
6313 the exception ranges. No dynamic code is required when entering
6314 a frame containing an exception handler. When an exception is
6315 raised, the tables are used to control a back trace of the
6316 subprogram invocation stack to locate the required exception
6317 handler. This method has considerably poorer performance for
6318 the propagation of exceptions, but there is no overhead for
6319 exception handlers if no exception is raised.
6321 The following switches can be used to control which of the
6322 two exception handling methods is used.
6328 @cindex @option{-gnatL} (@code{gcc})
6329 This switch causes the longjmp/setjmp approach to be used
6330 for exception handling. If this is the default mechanism for the
6331 target (see below), then this has no effect. If the default
6332 mechanism for the target is zero cost exceptions, then
6333 this switch can be used to modify this default, but it must be
6334 used for all units in the partition, including all run-time
6335 library units. One way to achieve this is to use the
6336 @option{-a} and @option{-f} switches for @code{gnatmake}.
6337 This option is rarely used. One case in which it may be
6338 advantageous is if you have an application where exception
6339 raising is common and the overall performance of the
6340 application is improved by favoring exception propagation.
6343 @cindex @option{-gnatZ} (@code{gcc})
6344 @cindex Zero Cost Exceptions
6345 This switch causes the zero cost approach to be sed
6346 for exception handling. If this is the default mechanism for the
6347 target (see below), then this has no effect. If the default
6348 mechanism for the target is longjmp/setjmp exceptions, then
6349 this switch can be used to modify this default, but it must be
6350 used for all units in the partition, including all run-time
6351 library units. One way to achieve this is to use the
6352 @option{-a} and @option{-f} switches for @code{gnatmake}.
6353 This option can only be used if the zero cost approach
6354 is available for the target in use (see below).
6358 The @code{longjmp/setjmp} approach is available on all targets, but
6359 the @code{zero cost} approach is only available on selected targets.
6360 To determine whether zero cost exceptions can be used for a
6361 particular target, look at the private part of the file system.ads.
6362 Either @code{GCC_ZCX_Support} or @code{Front_End_ZCX_Support} must
6363 be True to use the zero cost approach. If both of these switches
6364 are set to False, this means that zero cost exception handling
6365 is not yet available for that target. The switch
6366 @code{ZCX_By_Default} indicates the default approach. If this
6367 switch is set to True, then the @code{zero cost} approach is
6370 @node Units to Sources Mapping Files
6371 @subsection Units to Sources Mapping Files
6375 @item -gnatem^^=^@var{path}
6376 @cindex @option{-gnatem} (@code{gcc})
6377 A mapping file is a way to communicate to the compiler two mappings:
6378 from unit names to file names (without any directory information) and from
6379 file names to path names (with full directory information). These mappings
6380 are used by the compiler to short-circuit the path search.
6382 The use of mapping files is not required for correct operation of the
6383 compiler, but mapping files can improve efficiency, particularly when
6384 sources are read over a slow network connection. In normal operation,
6385 you need not be concerned with the format or use of mapping files,
6386 and the @option{-gnatem} switch is not a switch that you would use
6387 explicitly. it is intended only for use by automatic tools such as
6388 @code{gnatmake} running under the project file facility. The
6389 description here of the format of mapping files is provided
6390 for completeness and for possible use by other tools.
6392 A mapping file is a sequence of sets of three lines. In each set,
6393 the first line is the unit name, in lower case, with ``@code{%s}''
6395 specifications and ``@code{%b}'' appended for bodies; the second line is the
6396 file name; and the third line is the path name.
6402 /gnat/project1/sources/main.2.ada
6405 When the switch @option{-gnatem} is specified, the compiler will create
6406 in memory the two mappings from the specified file. If there is any problem
6407 (non existent file, truncated file or duplicate entries), no mapping
6410 Several @option{-gnatem} switches may be specified; however, only the last
6411 one on the command line will be taken into account.
6413 When using a project file, @code{gnatmake} create a temporary mapping file
6414 and communicates it to the compiler using this switch.
6419 @node Integrated Preprocessing
6420 @subsection Integrated Preprocessing
6423 GNAT sources may be preprocessed immediately before compilation; the actual
6424 text of the source is not the text of the source file, but is derived from it
6425 through a process called preprocessing. Integrated preprocessing is specified
6426 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
6427 indicates, through a text file, the preprocessing data to be used.
6428 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
6431 It is recommended that @code{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
6432 used when Integrated Preprocessing is used. The reason is that preprocessing
6433 with another Preprocessing Data file without changing the sources will
6434 not trigger recompilation without this switch.
6437 Note that @code{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
6438 always trigger recompilation for sources that are preprocessed,
6439 because @code{gnatmake} cannot compute the checksum of the source after
6443 The actual preprocessing function is described in details in section
6444 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
6445 preprocessing is triggered and parameterized.
6449 @item -gnatep=@var{file}
6450 @cindex @option{-gnatep} (@code{gcc})
6451 This switch indicates to the compiler the file name (without directory
6452 information) of the preprocessor data file to use. The preprocessor data file
6453 should be found in the source directories.
6456 A preprocessing data file is a text file with significant lines indicating
6457 how should be preprocessed either a specific source or all sources not
6458 mentioned in other lines. A significant line is a non empty, non comment line.
6459 Comments are similar to Ada comments.
6462 Each significant line starts with either a literal string or the character '*'.
6463 A literal string is the file name (without directory information) of the source
6464 to preprocess. A character '*' indicates the preprocessing for all the sources
6465 that are not specified explicitly on other lines (order of the lines is not
6466 significant). It is an error to have two lines with the same file name or two
6467 lines starting with the character '*'.
6470 After the file name or the character '*', another optional literal string
6471 indicating the file name of the definition file to be used for preprocessing.
6472 (see @ref{Form of Definitions File}. The definition files are found by the
6473 compiler in one of the source directories. In some cases, when compiling
6474 a source in a directory other than the current directory, if the definition
6475 file is in the current directory, it may be necessary to add the current
6476 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
6477 the compiler would not find the definition file.
6480 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
6481 be found. Those ^switches^switches^ are:
6486 Causes both preprocessor lines and the lines deleted by
6487 preprocessing to be replaced by blank lines, preserving the line number.
6488 This ^switch^switch^ is always implied; however, if specified after @option{-c}
6489 it cancels the effect of @option{-c}.
6492 Causes both preprocessor lines and the lines deleted
6493 by preprocessing to be retained as comments marked
6494 with the special string ``@code{--! }''.
6496 @item -Dsymbol=value
6497 Define or redefine a symbol, associated with value. A symbol is an Ada
6498 identifier, or an Ada reserved word, with the exception of @code{if},
6499 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
6500 @code{value} is either a literal string, an Ada identifier or any Ada reserved
6501 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
6502 same name defined in a definition file.
6505 Causes a sorted list of symbol names and values to be
6506 listed on the standard output file.
6509 Causes undefined symbols to be treated as having the value @code{FALSE}
6511 of a preprocessor test. In the absence of this option, an undefined symbol in
6512 a @code{#if} or @code{#elsif} test will be treated as an error.
6517 Examples of valid lines in a preprocessor data file:
6520 "toto.adb" "prep.def" -u
6521 -- preprocess "toto.adb", using definition file "prep.def",
6522 -- undefined symbol are False.
6525 -- preprocess all other sources without a definition file;
6526 -- suppressed lined are commented; symbol VERSION has the value V101.
6528 "titi.adb" "prep2.def" -s
6529 -- preprocess "titi.adb", using definition file "prep2.def";
6530 -- list all symbols with their values.
6533 @item ^-gnateD^/DATA_PREPROCESSING=^symbol[=value]
6534 @cindex @option{-gnateD} (@code{gcc})
6535 Define or redefine a preprocessing symbol, associated with value. If no value
6536 is given on the command line, then the value of the symbol is @code{True}.
6537 A symbol is an identifier, following normal Ada (case-insensitive)
6538 rules for its syntax, and value is any sequence (including an empty sequence)
6539 of characters from the set (letters, digits, period, underline).
6540 Ada reserved words may be used as symbols, with the exceptions of @code{if},
6541 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
6544 A symbol declared with this ^switch^switch^ on the command line replaces a
6545 symbol with the same name either in a definition file or specified with a
6546 ^switch^switch^ -D in the preprocessor data file.
6549 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
6553 @node Code Generation Control
6554 @subsection Code Generation Control
6558 The GCC technology provides a wide range of target dependent
6559 @option{-m} switches for controlling
6560 details of code generation with respect to different versions of
6561 architectures. This includes variations in instruction sets (e.g.
6562 different members of the power pc family), and different requirements
6563 for optimal arrangement of instructions (e.g. different members of
6564 the x86 family). The list of available @option{-m} switches may be
6565 found in the GCC documentation.
6567 Use of the these @option{-m} switches may in some cases result in improved
6570 The GNAT Pro technology is tested and qualified without any
6571 @option{-m} switches,
6572 so generally the most reliable approach is to avoid the use of these
6573 switches. However, we generally expect most of these switches to work
6574 successfully with GNAT Pro, and many customers have reported successful
6575 use of these options.
6577 Our general advice is to avoid the use of @option{-m} switches unless
6578 special needs lead to requirements in this area. In particular,
6579 there is no point in using @option{-m} switches to improve performance
6580 unless you actually see a performance improvement.
6584 @subsection Return Codes
6585 @cindex Return Codes
6586 @cindex @option{/RETURN_CODES=VMS}
6589 On VMS, GNAT compiled programs return POSIX-style codes by default,
6590 e.g. @option{/RETURN_CODES=POSIX}.
6592 To enable VMS style return codes, GNAT LINK with the option
6593 @option{/RETURN_CODES=VMS}. For example:
6596 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
6600 Programs built with /RETURN_CODES=VMS are suitable to be called in
6601 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
6602 are suitable for spawning with appropriate GNAT RTL routines.
6607 @node Search Paths and the Run-Time Library (RTL)
6608 @section Search Paths and the Run-Time Library (RTL)
6611 With the GNAT source-based library system, the compiler must be able to
6612 find source files for units that are needed by the unit being compiled.
6613 Search paths are used to guide this process.
6615 The compiler compiles one source file whose name must be given
6616 explicitly on the command line. In other words, no searching is done
6617 for this file. To find all other source files that are needed (the most
6618 common being the specs of units), the compiler examines the following
6619 directories, in the following order:
6623 The directory containing the source file of the main unit being compiled
6624 (the file name on the command line).
6627 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
6628 @code{gcc} command line, in the order given.
6631 @findex ADA_INCLUDE_PATH
6632 Each of the directories listed in the value of the
6633 @code{ADA_INCLUDE_PATH} ^environment variable^logical name^.
6635 Construct this value
6636 exactly as the @code{PATH} environment variable: a list of directory
6637 names separated by colons (semicolons when working with the NT version).
6640 Normally, define this value as a logical name containing a comma separated
6641 list of directory names.
6643 This variable can also be defined by means of an environment string
6644 (an argument to the DEC C exec* set of functions).
6648 DEFINE ANOTHER_PATH FOO:[BAG]
6649 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
6652 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
6653 first, followed by the standard Ada 95
6654 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
6655 If this is not redefined, the user will obtain the DEC Ada 83 IO packages
6656 (Text_IO, Sequential_IO, etc)
6657 instead of the Ada95 packages. Thus, in order to get the Ada 95
6658 packages by default, ADA_INCLUDE_PATH must be redefined.
6662 @findex ADA_PRJ_INCLUDE_FILE
6663 Each of the directories listed in the text file whose name is given
6664 by the @code{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
6667 @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
6668 driver when project files are used. It should not normally be set
6672 The content of the @file{ada_source_path} file which is part of the GNAT
6673 installation tree and is used to store standard libraries such as the
6674 GNAT Run Time Library (RTL) source files.
6676 @ref{Installing the library}
6681 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
6682 inhibits the use of the directory
6683 containing the source file named in the command line. You can still
6684 have this directory on your search path, but in this case it must be
6685 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
6687 Specifying the switch @option{-nostdinc}
6688 inhibits the search of the default location for the GNAT Run Time
6689 Library (RTL) source files.
6691 The compiler outputs its object files and ALI files in the current
6694 Caution: The object file can be redirected with the @option{-o} switch;
6695 however, @code{gcc} and @code{gnat1} have not been coordinated on this
6696 so the @file{ALI} file will not go to the right place. Therefore, you should
6697 avoid using the @option{-o} switch.
6701 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
6702 children make up the GNAT RTL, together with the simple @code{System.IO}
6703 package used in the @code{"Hello World"} example. The sources for these units
6704 are needed by the compiler and are kept together in one directory. Not
6705 all of the bodies are needed, but all of the sources are kept together
6706 anyway. In a normal installation, you need not specify these directory
6707 names when compiling or binding. Either the environment variables or
6708 the built-in defaults cause these files to be found.
6710 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
6711 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
6712 consisting of child units of @code{GNAT}. This is a collection of generally
6713 useful types, subprograms, etc. See the @cite{GNAT Reference Manual} for
6716 Besides simplifying access to the RTL, a major use of search paths is
6717 in compiling sources from multiple directories. This can make
6718 development environments much more flexible.
6721 @node Order of Compilation Issues
6722 @section Order of Compilation Issues
6725 If, in our earlier example, there was a spec for the @code{hello}
6726 procedure, it would be contained in the file @file{hello.ads}; yet this
6727 file would not have to be explicitly compiled. This is the result of the
6728 model we chose to implement library management. Some of the consequences
6729 of this model are as follows:
6733 There is no point in compiling specs (except for package
6734 specs with no bodies) because these are compiled as needed by clients. If
6735 you attempt a useless compilation, you will receive an error message.
6736 It is also useless to compile subunits because they are compiled as needed
6740 There are no order of compilation requirements: performing a
6741 compilation never obsoletes anything. The only way you can obsolete
6742 something and require recompilations is to modify one of the
6743 source files on which it depends.
6746 There is no library as such, apart from the ALI files
6747 (@pxref{The Ada Library Information Files}, for information on the format
6748 of these files). For now we find it convenient to create separate ALI files,
6749 but eventually the information therein may be incorporated into the object
6753 When you compile a unit, the source files for the specs of all units
6754 that it @code{with}'s, all its subunits, and the bodies of any generics it
6755 instantiates must be available (reachable by the search-paths mechanism
6756 described above), or you will receive a fatal error message.
6763 The following are some typical Ada compilation command line examples:
6766 @item $ gcc -c xyz.adb
6767 Compile body in file @file{xyz.adb} with all default options.
6770 @item $ gcc -c -O2 -gnata xyz-def.adb
6773 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
6776 Compile the child unit package in file @file{xyz-def.adb} with extensive
6777 optimizations, and pragma @code{Assert}/@code{Debug} statements
6780 @item $ gcc -c -gnatc abc-def.adb
6781 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
6785 @node Binding Using gnatbind
6786 @chapter Binding Using @code{gnatbind}
6790 * Running gnatbind::
6791 * Switches for gnatbind::
6792 * Command-Line Access::
6793 * Search Paths for gnatbind::
6794 * Examples of gnatbind Usage::
6798 This chapter describes the GNAT binder, @code{gnatbind}, which is used
6799 to bind compiled GNAT objects. The @code{gnatbind} program performs
6800 four separate functions:
6804 Checks that a program is consistent, in accordance with the rules in
6805 Chapter 10 of the Ada 95 Reference Manual. In particular, error
6806 messages are generated if a program uses inconsistent versions of a
6810 Checks that an acceptable order of elaboration exists for the program
6811 and issues an error message if it cannot find an order of elaboration
6812 that satisfies the rules in Chapter 10 of the Ada 95 Language Manual.
6815 Generates a main program incorporating the given elaboration order.
6816 This program is a small Ada package (body and spec) that
6817 must be subsequently compiled
6818 using the GNAT compiler. The necessary compilation step is usually
6819 performed automatically by @code{gnatlink}. The two most important
6820 functions of this program
6821 are to call the elaboration routines of units in an appropriate order
6822 and to call the main program.
6825 Determines the set of object files required by the given main program.
6826 This information is output in the forms of comments in the generated program,
6827 to be read by the @code{gnatlink} utility used to link the Ada application.
6831 @node Running gnatbind
6832 @section Running @code{gnatbind}
6835 The form of the @code{gnatbind} command is
6838 $ gnatbind [@i{switches}] @i{mainprog}[.ali] [@i{switches}]
6842 where @file{@i{mainprog}.adb} is the Ada file containing the main program
6843 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
6844 package in two files whose names are
6845 @file{b~@i{mainprog}.ads}, and @file{b~@i{mainprog}.adb}.
6846 For example, if given the
6847 parameter @file{hello.ali}, for a main program contained in file
6848 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
6849 and @file{b~hello.adb}.
6851 When doing consistency checking, the binder takes into consideration
6852 any source files it can locate. For example, if the binder determines
6853 that the given main program requires the package @code{Pack}, whose
6855 file is @file{pack.ali} and whose corresponding source spec file is
6856 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
6857 (using the same search path conventions as previously described for the
6858 @code{gcc} command). If it can locate this source file, it checks that
6860 or source checksums of the source and its references to in @file{ALI} files
6861 match. In other words, any @file{ALI} files that mentions this spec must have
6862 resulted from compiling this version of the source file (or in the case
6863 where the source checksums match, a version close enough that the
6864 difference does not matter).
6866 @cindex Source files, use by binder
6867 The effect of this consistency checking, which includes source files, is
6868 that the binder ensures that the program is consistent with the latest
6869 version of the source files that can be located at bind time. Editing a
6870 source file without compiling files that depend on the source file cause
6871 error messages to be generated by the binder.
6873 For example, suppose you have a main program @file{hello.adb} and a
6874 package @code{P}, from file @file{p.ads} and you perform the following
6879 Enter @code{gcc -c hello.adb} to compile the main program.
6882 Enter @code{gcc -c p.ads} to compile package @code{P}.
6885 Edit file @file{p.ads}.
6888 Enter @code{gnatbind hello}.
6892 At this point, the file @file{p.ali} contains an out-of-date time stamp
6893 because the file @file{p.ads} has been edited. The attempt at binding
6894 fails, and the binder generates the following error messages:
6897 error: "hello.adb" must be recompiled ("p.ads" has been modified)
6898 error: "p.ads" has been modified and must be recompiled
6902 Now both files must be recompiled as indicated, and then the bind can
6903 succeed, generating a main program. You need not normally be concerned
6904 with the contents of this file, but for reference purposes a sample
6905 binder output file is given in @ref{Example of Binder Output File}.
6907 In most normal usage, the default mode of @command{gnatbind} which is to
6908 generate the main package in Ada, as described in the previous section.
6909 In particular, this means that any Ada programmer can read and understand
6910 the generated main program. It can also be debugged just like any other
6911 Ada code provided the @option{^-g^/DEBUG^} switch is used for
6912 @command{gnatbind} and @command{gnatlink}.
6914 However for some purposes it may be convenient to generate the main
6915 program in C rather than Ada. This may for example be helpful when you
6916 are generating a mixed language program with the main program in C. The
6917 GNAT compiler itself is an example.
6918 The use of the @option{^-C^/BIND_FILE=C^} switch
6919 for both @code{gnatbind} and @code{gnatlink} will cause the program to
6920 be generated in C (and compiled using the gnu C compiler).
6923 @node Switches for gnatbind
6924 @section Switches for @command{gnatbind}
6927 The following switches are available with @code{gnatbind}; details will
6928 be presented in subsequent sections.
6931 * Consistency-Checking Modes::
6932 * Binder Error Message Control::
6933 * Elaboration Control::
6935 * Binding with Non-Ada Main Programs::
6936 * Binding Programs with No Main Subprogram::
6941 @item ^-aO^/OBJECT_SEARCH^
6942 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
6943 Specify directory to be searched for ALI files.
6945 @item ^-aI^/SOURCE_SEARCH^
6946 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
6947 Specify directory to be searched for source file.
6949 @item ^-A^/BIND_FILE=ADA^
6950 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
6951 Generate binder program in Ada (default)
6953 @item ^-b^/REPORT_ERRORS=BRIEF^
6954 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
6955 Generate brief messages to @file{stderr} even if verbose mode set.
6957 @item ^-c^/NOOUTPUT^
6958 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
6959 Check only, no generation of binder output file.
6961 @item ^-C^/BIND_FILE=C^
6962 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
6963 Generate binder program in C
6965 @item ^-e^/ELABORATION_DEPENDENCIES^
6966 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
6967 Output complete list of elaboration-order dependencies.
6969 @item ^-E^/STORE_TRACEBACKS^
6970 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
6971 Store tracebacks in exception occurrences when the target supports it.
6972 This is the default with the zero cost exception mechanism.
6974 @c The following may get moved to an appendix
6975 This option is currently supported on the following targets:
6976 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
6978 See also the packages @code{GNAT.Traceback} and
6979 @code{GNAT.Traceback.Symbolic} for more information.
6981 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
6985 @item ^-F^/FORCE_ELABS_FLAGS^
6986 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
6987 Force the checks of elaboration flags. @command{gnatbind} does not normally
6988 generate checks of elaboration flags for the main executable, except when
6989 a Stand-Alone Library is used. However, there are cases when this cannot be
6990 detected by gnatbind. An example is importing an interface of a Stand-Alone
6991 Library through a pragma Import and only specifying through a linker switch
6992 this Stand-Alone Library. This switch is used to guarantee that elaboration
6993 flag checks are generated.
6996 @cindex @option{^-h^/HELP^} (@command{gnatbind})
6997 Output usage (help) information
7000 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7001 Specify directory to be searched for source and ALI files.
7003 @item ^-I-^/NOCURRENT_DIRECTORY^
7004 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
7005 Do not look for sources in the current directory where @code{gnatbind} was
7006 invoked, and do not look for ALI files in the directory containing the
7007 ALI file named in the @code{gnatbind} command line.
7009 @item ^-l^/ORDER_OF_ELABORATION^
7010 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
7011 Output chosen elaboration order.
7013 @item ^-Lxxx^/BUILD_LIBRARY=xxx^
7014 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
7015 Binds the units for library building. In this case the adainit and
7016 adafinal procedures (See @pxref{Binding with Non-Ada Main Programs})
7017 are renamed to ^xxxinit^XXXINIT^ and
7018 ^xxxfinal^XXXFINAL^.
7019 Implies ^-n^/NOCOMPILE^.
7021 (@pxref{GNAT and Libraries}, for more details.)
7024 On OpenVMS, these init and final procedures are exported in uppercase
7025 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
7026 the init procedure will be "TOTOINIT" and the exported name of the final
7027 procedure will be "TOTOFINAL".
7030 @item ^-Mxyz^/RENAME_MAIN=xyz^
7031 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
7032 Rename generated main program from main to xyz
7034 @item ^-m^/ERROR_LIMIT=^@var{n}
7035 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
7036 Limit number of detected errors to @var{n}, where @var{n} is
7037 in the range 1..999_999. The default value if no switch is
7038 given is 9999. Binding is terminated if the limit is exceeded.
7040 Furthermore, under Windows, the sources pointed to by the libraries path
7041 set in the registry are not searched for.
7045 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7049 @cindex @option{-nostdinc} (@command{gnatbind})
7050 Do not look for sources in the system default directory.
7053 @cindex @option{-nostdlib} (@command{gnatbind})
7054 Do not look for library files in the system default directory.
7056 @item --RTS=@var{rts-path}
7057 @cindex @option{--RTS} (@code{gnatbind})
7058 Specifies the default location of the runtime library. Same meaning as the
7059 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
7061 @item ^-o ^/OUTPUT=^@var{file}
7062 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7063 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7064 Note that if this option is used, then linking must be done manually,
7065 gnatlink cannot be used.
7067 @item ^-O^/OBJECT_LIST^
7068 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7071 @item ^-p^/PESSIMISTIC_ELABORATION^
7072 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7073 Pessimistic (worst-case) elaboration order
7075 @item ^-s^/READ_SOURCES=ALL^
7076 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7077 Require all source files to be present.
7079 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7080 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7081 Specifies the value to be used when detecting uninitialized scalar
7082 objects with pragma Initialize_Scalars.
7083 The @var{xxx} ^string specified with the switch^option^ may be either
7085 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7086 @item ``@option{^lo^LOW^}'' for the lowest possible value
7087 possible, and the low
7088 @item ``@option{^hi^HIGH^}'' for the highest possible value
7089 @item ``@option{xx}'' for a value consisting of repeated bytes with the
7090 value 16#xx# (i.e. xx is a string of two hexadecimal digits).
7093 In addition, you can specify @option{-Sev} to indicate that the value is
7094 to be set at run time. In this case, the program will look for an environment
7095 @cindex GNAT_INIT_SCALARS
7096 variable of the form @code{GNAT_INIT_SCALARS=xx}, where xx is one
7097 of @option{in/lo/hi/xx} with the same meanings as above.
7098 If no environment variable is found, or if it does not have a valid value,
7099 then the default is @option{in} (invalid values).
7103 @cindex @option{-static} (@code{gnatbind})
7104 Link against a static GNAT run time.
7107 @cindex @option{-shared} (@code{gnatbind})
7108 Link against a shared GNAT run time when available.
7111 @item ^-t^/NOTIME_STAMP_CHECK^
7112 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7113 Tolerate time stamp and other consistency errors
7115 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7116 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7117 Set the time slice value to @var{n} milliseconds. If the system supports
7118 the specification of a specific time slice value, then the indicated value
7119 is used. If the system does not support specific time slice values, but
7120 does support some general notion of round-robin scheduling, then any
7121 non-zero value will activate round-robin scheduling.
7123 A value of zero is treated specially. It turns off time
7124 slicing, and in addition, indicates to the tasking run time that the
7125 semantics should match as closely as possible the Annex D
7126 requirements of the Ada RM, and in particular sets the default
7127 scheduling policy to @code{FIFO_Within_Priorities}.
7129 @item ^-v^/REPORT_ERRORS=VERBOSE^
7130 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7131 Verbose mode. Write error messages, header, summary output to
7136 @cindex @option{-w} (@code{gnatbind})
7137 Warning mode (@var{x}=s/e for suppress/treat as error)
7141 @item /WARNINGS=NORMAL
7142 @cindex @option{/WARNINGS} (@code{gnatbind})
7143 Normal warnings mode. Warnings are issued but ignored
7145 @item /WARNINGS=SUPPRESS
7146 @cindex @option{/WARNINGS} (@code{gnatbind})
7147 All warning messages are suppressed
7149 @item /WARNINGS=ERROR
7150 @cindex @option{/WARNINGS} (@code{gnatbind})
7151 Warning messages are treated as fatal errors
7154 @item ^-x^/READ_SOURCES=NONE^
7155 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7156 Exclude source files (check object consistency only).
7159 @item /READ_SOURCES=AVAILABLE
7160 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7161 Default mode, in which sources are checked for consistency only if
7165 @item ^-z^/ZERO_MAIN^
7166 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7172 You may obtain this listing of switches by running @code{gnatbind} with
7177 @node Consistency-Checking Modes
7178 @subsection Consistency-Checking Modes
7181 As described earlier, by default @code{gnatbind} checks
7182 that object files are consistent with one another and are consistent
7183 with any source files it can locate. The following switches control binder
7188 @item ^-s^/READ_SOURCES=ALL^
7189 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
7190 Require source files to be present. In this mode, the binder must be
7191 able to locate all source files that are referenced, in order to check
7192 their consistency. In normal mode, if a source file cannot be located it
7193 is simply ignored. If you specify this switch, a missing source
7196 @item ^-x^/READ_SOURCES=NONE^
7197 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
7198 Exclude source files. In this mode, the binder only checks that ALI
7199 files are consistent with one another. Source files are not accessed.
7200 The binder runs faster in this mode, and there is still a guarantee that
7201 the resulting program is self-consistent.
7202 If a source file has been edited since it was last compiled, and you
7203 specify this switch, the binder will not detect that the object
7204 file is out of date with respect to the source file. Note that this is the
7205 mode that is automatically used by @code{gnatmake} because in this
7206 case the checking against sources has already been performed by
7207 @code{gnatmake} in the course of compilation (i.e. before binding).
7210 @item /READ_SOURCES=AVAILABLE
7211 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
7212 This is the default mode in which source files are checked if they are
7213 available, and ignored if they are not available.
7217 @node Binder Error Message Control
7218 @subsection Binder Error Message Control
7221 The following switches provide control over the generation of error
7222 messages from the binder:
7226 @item ^-v^/REPORT_ERRORS=VERBOSE^
7227 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7228 Verbose mode. In the normal mode, brief error messages are generated to
7229 @file{stderr}. If this switch is present, a header is written
7230 to @file{stdout} and any error messages are directed to @file{stdout}.
7231 All that is written to @file{stderr} is a brief summary message.
7233 @item ^-b^/REPORT_ERRORS=BRIEF^
7234 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
7235 Generate brief error messages to @file{stderr} even if verbose mode is
7236 specified. This is relevant only when used with the
7237 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
7241 @cindex @option{-m} (@code{gnatbind})
7242 Limits the number of error messages to @var{n}, a decimal integer in the
7243 range 1-999. The binder terminates immediately if this limit is reached.
7246 @cindex @option{-M} (@code{gnatbind})
7247 Renames the generated main program from @code{main} to @code{xxx}.
7248 This is useful in the case of some cross-building environments, where
7249 the actual main program is separate from the one generated
7253 @item ^-ws^/WARNINGS=SUPPRESS^
7254 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
7256 Suppress all warning messages.
7258 @item ^-we^/WARNINGS=ERROR^
7259 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
7260 Treat any warning messages as fatal errors.
7263 @item /WARNINGS=NORMAL
7264 Standard mode with warnings generated, but warnings do not get treated
7268 @item ^-t^/NOTIME_STAMP_CHECK^
7269 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7270 @cindex Time stamp checks, in binder
7271 @cindex Binder consistency checks
7272 @cindex Consistency checks, in binder
7273 The binder performs a number of consistency checks including:
7277 Check that time stamps of a given source unit are consistent
7279 Check that checksums of a given source unit are consistent
7281 Check that consistent versions of @code{GNAT} were used for compilation
7283 Check consistency of configuration pragmas as required
7287 Normally failure of such checks, in accordance with the consistency
7288 requirements of the Ada Reference Manual, causes error messages to be
7289 generated which abort the binder and prevent the output of a binder
7290 file and subsequent link to obtain an executable.
7292 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
7293 into warnings, so that
7294 binding and linking can continue to completion even in the presence of such
7295 errors. The result may be a failed link (due to missing symbols), or a
7296 non-functional executable which has undefined semantics.
7297 @emph{This means that
7298 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
7302 @node Elaboration Control
7303 @subsection Elaboration Control
7306 The following switches provide additional control over the elaboration
7307 order. For full details see @xref{Elaboration Order Handling in GNAT}.
7310 @item ^-p^/PESSIMISTIC_ELABORATION^
7311 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
7312 Normally the binder attempts to choose an elaboration order that is
7313 likely to minimize the likelihood of an elaboration order error resulting
7314 in raising a @code{Program_Error} exception. This switch reverses the
7315 action of the binder, and requests that it deliberately choose an order
7316 that is likely to maximize the likelihood of an elaboration error.
7317 This is useful in ensuring portability and avoiding dependence on
7318 accidental fortuitous elaboration ordering.
7320 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
7322 elaboration checking is used (@option{-gnatE} switch used for compilation).
7323 This is because in the default static elaboration mode, all necessary
7324 @code{Elaborate_All} pragmas are implicitly inserted.
7325 These implicit pragmas are still respected by the binder in
7326 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
7327 safe elaboration order is assured.
7330 @node Output Control
7331 @subsection Output Control
7334 The following switches allow additional control over the output
7335 generated by the binder.
7340 @item ^-A^/BIND_FILE=ADA^
7341 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
7342 Generate binder program in Ada (default). The binder program is named
7343 @file{b~@var{mainprog}.adb} by default. This can be changed with
7344 @option{^-o^/OUTPUT^} @code{gnatbind} option.
7346 @item ^-c^/NOOUTPUT^
7347 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
7348 Check only. Do not generate the binder output file. In this mode the
7349 binder performs all error checks but does not generate an output file.
7351 @item ^-C^/BIND_FILE=C^
7352 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
7353 Generate binder program in C. The binder program is named
7354 @file{b_@var{mainprog}.c}.
7355 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
7358 @item ^-e^/ELABORATION_DEPENDENCIES^
7359 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
7360 Output complete list of elaboration-order dependencies, showing the
7361 reason for each dependency. This output can be rather extensive but may
7362 be useful in diagnosing problems with elaboration order. The output is
7363 written to @file{stdout}.
7366 @cindex @option{^-h^/HELP^} (@code{gnatbind})
7367 Output usage information. The output is written to @file{stdout}.
7369 @item ^-K^/LINKER_OPTION_LIST^
7370 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
7371 Output linker options to @file{stdout}. Includes library search paths,
7372 contents of pragmas Ident and Linker_Options, and libraries added
7375 @item ^-l^/ORDER_OF_ELABORATION^
7376 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
7377 Output chosen elaboration order. The output is written to @file{stdout}.
7379 @item ^-O^/OBJECT_LIST^
7380 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
7381 Output full names of all the object files that must be linked to provide
7382 the Ada component of the program. The output is written to @file{stdout}.
7383 This list includes the files explicitly supplied and referenced by the user
7384 as well as implicitly referenced run-time unit files. The latter are
7385 omitted if the corresponding units reside in shared libraries. The
7386 directory names for the run-time units depend on the system configuration.
7388 @item ^-o ^/OUTPUT=^@var{file}
7389 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
7390 Set name of output file to @var{file} instead of the normal
7391 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
7392 binder generated body filename. In C mode you would normally give
7393 @var{file} an extension of @file{.c} because it will be a C source program.
7394 Note that if this option is used, then linking must be done manually.
7395 It is not possible to use gnatlink in this case, since it cannot locate
7398 @item ^-r^/RESTRICTION_LIST^
7399 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
7400 Generate list of @code{pragma Restrictions} that could be applied to
7401 the current unit. This is useful for code audit purposes, and also may
7402 be used to improve code generation in some cases.
7406 @node Binding with Non-Ada Main Programs
7407 @subsection Binding with Non-Ada Main Programs
7410 In our description so far we have assumed that the main
7411 program is in Ada, and that the task of the binder is to generate a
7412 corresponding function @code{main} that invokes this Ada main
7413 program. GNAT also supports the building of executable programs where
7414 the main program is not in Ada, but some of the called routines are
7415 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
7416 The following switch is used in this situation:
7420 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
7421 No main program. The main program is not in Ada.
7425 In this case, most of the functions of the binder are still required,
7426 but instead of generating a main program, the binder generates a file
7427 containing the following callable routines:
7432 You must call this routine to initialize the Ada part of the program by
7433 calling the necessary elaboration routines. A call to @code{adainit} is
7434 required before the first call to an Ada subprogram.
7436 Note that it is assumed that the basic execution environment must be setup
7437 to be appropriate for Ada execution at the point where the first Ada
7438 subprogram is called. In particular, if the Ada code will do any
7439 floating-point operations, then the FPU must be setup in an appropriate
7440 manner. For the case of the x86, for example, full precision mode is
7441 required. The procedure GNAT.Float_Control.Reset may be used to ensure
7442 that the FPU is in the right state.
7446 You must call this routine to perform any library-level finalization
7447 required by the Ada subprograms. A call to @code{adafinal} is required
7448 after the last call to an Ada subprogram, and before the program
7453 If the @option{^-n^/NOMAIN^} switch
7454 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7455 @cindex Binder, multiple input files
7456 is given, more than one ALI file may appear on
7457 the command line for @code{gnatbind}. The normal @dfn{closure}
7458 calculation is performed for each of the specified units. Calculating
7459 the closure means finding out the set of units involved by tracing
7460 @code{with} references. The reason it is necessary to be able to
7461 specify more than one ALI file is that a given program may invoke two or
7462 more quite separate groups of Ada units.
7464 The binder takes the name of its output file from the last specified ALI
7465 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
7466 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
7467 The output is an Ada unit in source form that can
7468 be compiled with GNAT unless the -C switch is used in which case the
7469 output is a C source file, which must be compiled using the C compiler.
7470 This compilation occurs automatically as part of the @code{gnatlink}
7473 Currently the GNAT run time requires a FPU using 80 bits mode
7474 precision. Under targets where this is not the default it is required to
7475 call GNAT.Float_Control.Reset before using floating point numbers (this
7476 include float computation, float input and output) in the Ada code. A
7477 side effect is that this could be the wrong mode for the foreign code
7478 where floating point computation could be broken after this call.
7480 @node Binding Programs with No Main Subprogram
7481 @subsection Binding Programs with No Main Subprogram
7484 It is possible to have an Ada program which does not have a main
7485 subprogram. This program will call the elaboration routines of all the
7486 packages, then the finalization routines.
7488 The following switch is used to bind programs organized in this manner:
7491 @item ^-z^/ZERO_MAIN^
7492 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7493 Normally the binder checks that the unit name given on the command line
7494 corresponds to a suitable main subprogram. When this switch is used,
7495 a list of ALI files can be given, and the execution of the program
7496 consists of elaboration of these units in an appropriate order.
7500 @node Command-Line Access
7501 @section Command-Line Access
7504 The package @code{Ada.Command_Line} provides access to the command-line
7505 arguments and program name. In order for this interface to operate
7506 correctly, the two variables
7518 are declared in one of the GNAT library routines. These variables must
7519 be set from the actual @code{argc} and @code{argv} values passed to the
7520 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
7521 generates the C main program to automatically set these variables.
7522 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
7523 set these variables. If they are not set, the procedures in
7524 @code{Ada.Command_Line} will not be available, and any attempt to use
7525 them will raise @code{Constraint_Error}. If command line access is
7526 required, your main program must set @code{gnat_argc} and
7527 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
7531 @node Search Paths for gnatbind
7532 @section Search Paths for @code{gnatbind}
7535 The binder takes the name of an ALI file as its argument and needs to
7536 locate source files as well as other ALI files to verify object consistency.
7538 For source files, it follows exactly the same search rules as @code{gcc}
7539 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
7540 directories searched are:
7544 The directory containing the ALI file named in the command line, unless
7545 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
7548 All directories specified by @option{^-I^/SEARCH^}
7549 switches on the @code{gnatbind}
7550 command line, in the order given.
7553 @findex ADA_OBJECTS_PATH
7554 Each of the directories listed in the value of the
7555 @code{ADA_OBJECTS_PATH} ^environment variable^logical name^.
7557 Construct this value
7558 exactly as the @code{PATH} environment variable: a list of directory
7559 names separated by colons (semicolons when working with the NT version
7563 Normally, define this value as a logical name containing a comma separated
7564 list of directory names.
7566 This variable can also be defined by means of an environment string
7567 (an argument to the DEC C exec* set of functions).
7571 DEFINE ANOTHER_PATH FOO:[BAG]
7572 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7575 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7576 first, followed by the standard Ada 95
7577 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
7578 If this is not redefined, the user will obtain the DEC Ada 83 IO packages
7579 (Text_IO, Sequential_IO, etc)
7580 instead of the Ada95 packages. Thus, in order to get the Ada 95
7581 packages by default, ADA_OBJECTS_PATH must be redefined.
7585 @findex ADA_PRJ_OBJECTS_FILE
7586 Each of the directories listed in the text file whose name is given
7587 by the @code{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
7590 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7591 driver when project files are used. It should not normally be set
7595 The content of the @file{ada_object_path} file which is part of the GNAT
7596 installation tree and is used to store standard libraries such as the
7597 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
7600 @ref{Installing the library}
7605 In the binder the switch @option{^-I^/SEARCH^}
7606 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7607 is used to specify both source and
7608 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
7609 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7610 instead if you want to specify
7611 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
7612 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
7613 if you want to specify library paths
7614 only. This means that for the binder
7615 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
7616 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
7617 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
7618 The binder generates the bind file (a C language source file) in the
7619 current working directory.
7625 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7626 children make up the GNAT Run-Time Library, together with the package
7627 GNAT and its children, which contain a set of useful additional
7628 library functions provided by GNAT. The sources for these units are
7629 needed by the compiler and are kept together in one directory. The ALI
7630 files and object files generated by compiling the RTL are needed by the
7631 binder and the linker and are kept together in one directory, typically
7632 different from the directory containing the sources. In a normal
7633 installation, you need not specify these directory names when compiling
7634 or binding. Either the environment variables or the built-in defaults
7635 cause these files to be found.
7637 Besides simplifying access to the RTL, a major use of search paths is
7638 in compiling sources from multiple directories. This can make
7639 development environments much more flexible.
7641 @node Examples of gnatbind Usage
7642 @section Examples of @code{gnatbind} Usage
7645 This section contains a number of examples of using the GNAT binding
7646 utility @code{gnatbind}.
7649 @item gnatbind hello
7650 The main program @code{Hello} (source program in @file{hello.adb}) is
7651 bound using the standard switch settings. The generated main program is
7652 @file{b~hello.adb}. This is the normal, default use of the binder.
7655 @item gnatbind hello -o mainprog.adb
7658 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
7660 The main program @code{Hello} (source program in @file{hello.adb}) is
7661 bound using the standard switch settings. The generated main program is
7662 @file{mainprog.adb} with the associated spec in
7663 @file{mainprog.ads}. Note that you must specify the body here not the
7664 spec, in the case where the output is in Ada. Note that if this option
7665 is used, then linking must be done manually, since gnatlink will not
7666 be able to find the generated file.
7669 @item gnatbind main -C -o mainprog.c -x
7672 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
7674 The main program @code{Main} (source program in
7675 @file{main.adb}) is bound, excluding source files from the
7676 consistency checking, generating
7677 the file @file{mainprog.c}.
7680 @item gnatbind -x main_program -C -o mainprog.c
7681 This command is exactly the same as the previous example. Switches may
7682 appear anywhere in the command line, and single letter switches may be
7683 combined into a single switch.
7687 @item gnatbind -n math dbase -C -o ada-control.c
7690 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
7692 The main program is in a language other than Ada, but calls to
7693 subprograms in packages @code{Math} and @code{Dbase} appear. This call
7694 to @code{gnatbind} generates the file @file{ada-control.c} containing
7695 the @code{adainit} and @code{adafinal} routines to be called before and
7696 after accessing the Ada units.
7700 @c ------------------------------------
7701 @node Linking Using gnatlink
7702 @chapter Linking Using @code{gnatlink}
7703 @c ------------------------------------
7707 This chapter discusses @code{gnatlink}, a tool that links
7708 an Ada program and builds an executable file. This utility
7709 invokes the system linker ^(via the @code{gcc} command)^^
7710 with a correct list of object files and library references.
7711 @code{gnatlink} automatically determines the list of files and
7712 references for the Ada part of a program. It uses the binder file
7713 generated by the @command{gnatbind} to determine this list.
7716 * Running gnatlink::
7717 * Switches for gnatlink::
7718 * Setting Stack Size from gnatlink::
7719 * Setting Heap Size from gnatlink::
7722 @node Running gnatlink
7723 @section Running @code{gnatlink}
7726 The form of the @code{gnatlink} command is
7729 $ gnatlink [@var{switches}] @var{mainprog}[.ali]
7730 [@var{non-Ada objects}] [@var{linker options}]
7734 The arguments of @code{gnatlink} (switches, main @file{ALI} file,
7736 or linker options) may be in any order, provided that no non-Ada object may
7737 be mistaken for a main @file{ALI} file.
7738 Any file name @file{F} without the @file{.ali}
7739 extension will be taken as the main @file{ALI} file if a file exists
7740 whose name is the concatenation of @file{F} and @file{.ali}.
7743 @file{@var{mainprog}.ali} references the ALI file of the main program.
7744 The @file{.ali} extension of this file can be omitted. From this
7745 reference, @code{gnatlink} locates the corresponding binder file
7746 @file{b~@var{mainprog}.adb} and, using the information in this file along
7747 with the list of non-Ada objects and linker options, constructs a
7748 linker command file to create the executable.
7750 The arguments other than the @code{gnatlink} switches and the main @file{ALI}
7751 file are passed to the linker uninterpreted.
7752 They typically include the names of
7753 object files for units written in other languages than Ada and any library
7754 references required to resolve references in any of these foreign language
7755 units, or in @code{Import} pragmas in any Ada units.
7757 @var{linker options} is an optional list of linker specific
7759 The default linker called by gnatlink is @var{gcc} which in
7760 turn calls the appropriate system linker.
7761 Standard options for the linker such as @option{-lmy_lib} or
7762 @option{-Ldir} can be added as is.
7763 For options that are not recognized by
7764 @var{gcc} as linker options, use the @var{gcc} switches @option{-Xlinker} or
7766 Refer to the GCC documentation for
7767 details. Here is an example showing how to generate a linker map:
7771 $ gnatlink my_prog -Wl,-Map,MAPFILE
7776 <<Need example for VMS>>
7779 Using @var{linker options} it is possible to set the program stack and
7780 heap size. See @ref{Setting Stack Size from gnatlink}, and
7781 @ref{Setting Heap Size from gnatlink}.
7783 @code{gnatlink} determines the list of objects required by the Ada
7784 program and prepends them to the list of objects passed to the linker.
7785 @code{gnatlink} also gathers any arguments set by the use of
7786 @code{pragma Linker_Options} and adds them to the list of arguments
7787 presented to the linker.
7790 @code{gnatlink} accepts the following types of extra files on the command
7791 line: objects (.OBJ), libraries (.OLB), sharable images (.EXE), and
7792 options files (.OPT). These are recognized and handled according to their
7796 @node Switches for gnatlink
7797 @section Switches for @code{gnatlink}
7800 The following switches are available with the @code{gnatlink} utility:
7805 @item ^-A^/BIND_FILE=ADA^
7806 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatlink})
7807 The binder has generated code in Ada. This is the default.
7809 @item ^-C^/BIND_FILE=C^
7810 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatlink})
7811 If instead of generating a file in Ada, the binder has generated one in
7812 C, then the linker needs to know about it. Use this switch to signal
7813 to @code{gnatlink} that the binder has generated C code rather than
7816 @item ^-f^/FORCE_OBJECT_FILE_LIST^
7817 @cindex Command line length
7818 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@code{gnatlink})
7819 On some targets, the command line length is limited, and @code{gnatlink}
7820 will generate a separate file for the linker if the list of object files
7822 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
7823 to be generated even if
7824 the limit is not exceeded. This is useful in some cases to deal with
7825 special situations where the command line length is exceeded.
7828 @cindex Debugging information, including
7829 @cindex @option{^-g^/DEBUG^} (@code{gnatlink})
7830 The option to include debugging information causes the Ada bind file (in
7831 other words, @file{b~@var{mainprog}.adb}) to be compiled with
7832 @option{^-g^/DEBUG^}.
7833 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
7834 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
7835 Without @option{^-g^/DEBUG^}, the binder removes these files by
7836 default. The same procedure apply if a C bind file was generated using
7837 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
7838 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
7840 @item ^-n^/NOCOMPILE^
7841 @cindex @option{^-n^/NOCOMPILE^} (@code{gnatlink})
7842 Do not compile the file generated by the binder. This may be used when
7843 a link is rerun with different options, but there is no need to recompile
7847 @cindex @option{^-v^/VERBOSE^} (@code{gnatlink})
7848 Causes additional information to be output, including a full list of the
7849 included object files. This switch option is most useful when you want
7850 to see what set of object files are being used in the link step.
7852 @item ^-v -v^/VERBOSE/VERBOSE^
7853 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@code{gnatlink})
7854 Very verbose mode. Requests that the compiler operate in verbose mode when
7855 it compiles the binder file, and that the system linker run in verbose mode.
7857 @item ^-o ^/EXECUTABLE=^@var{exec-name}
7858 @cindex @option{^-o^/EXECUTABLE^} (@code{gnatlink})
7859 @var{exec-name} specifies an alternate name for the generated
7860 executable program. If this switch is omitted, the executable has the same
7861 name as the main unit. For example, @code{gnatlink try.ali} creates
7862 an executable called @file{^try^TRY.EXE^}.
7865 @item -b @var{target}
7866 @cindex @option{-b} (@code{gnatlink})
7867 Compile your program to run on @var{target}, which is the name of a
7868 system configuration. You must have a GNAT cross-compiler built if
7869 @var{target} is not the same as your host system.
7872 @cindex @option{-B} (@code{gnatlink})
7873 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
7874 from @var{dir} instead of the default location. Only use this switch
7875 when multiple versions of the GNAT compiler are available. See the
7876 @code{gcc} manual page for further details. You would normally use the
7877 @option{-b} or @option{-V} switch instead.
7879 @item --GCC=@var{compiler_name}
7880 @cindex @option{--GCC=compiler_name} (@code{gnatlink})
7881 Program used for compiling the binder file. The default is
7882 `@code{gcc}'. You need to use quotes around @var{compiler_name} if
7883 @code{compiler_name} contains spaces or other separator characters. As
7884 an example @option{--GCC="foo -x -y"} will instruct @code{gnatlink} to use
7885 @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
7886 inserted after your command name. Thus in the above example the compiler
7887 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
7888 If several @option{--GCC=compiler_name} are used, only the last
7889 @var{compiler_name} is taken into account. However, all the additional
7890 switches are also taken into account. Thus,
7891 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
7892 @option{--GCC="bar -x -y -z -t"}.
7894 @item --LINK=@var{name}
7895 @cindex @option{--LINK=} (@code{gnatlink})
7896 @var{name} is the name of the linker to be invoked. This is especially
7897 useful in mixed language programs since languages such as C++ require
7898 their own linker to be used. When this switch is omitted, the default
7899 name for the linker is (@file{gcc}). When this switch is used, the
7900 specified linker is called instead of (@file{gcc}) with exactly the same
7901 parameters that would have been passed to (@file{gcc}) so if the desired
7902 linker requires different parameters it is necessary to use a wrapper
7903 script that massages the parameters before invoking the real linker. It
7904 may be useful to control the exact invocation by using the verbose
7910 @item /DEBUG=TRACEBACK
7911 @cindex @code{/DEBUG=TRACEBACK} (@code{gnatlink})
7912 This qualifier causes sufficient information to be included in the
7913 executable file to allow a traceback, but does not include the full
7914 symbol information needed by the debugger.
7916 @item /IDENTIFICATION="<string>"
7917 @code{"<string>"} specifies the string to be stored in the image file
7918 identification field in the image header.
7919 It overrides any pragma @code{Ident} specified string.
7921 @item /NOINHIBIT-EXEC
7922 Generate the executable file even if there are linker warnings.
7924 @item /NOSTART_FILES
7925 Don't link in the object file containing the ``main'' transfer address.
7926 Used when linking with a foreign language main program compiled with a
7930 Prefer linking with object libraries over sharable images, even without
7936 @node Setting Stack Size from gnatlink
7937 @section Setting Stack Size from @code{gnatlink}
7940 Under Windows systems, it is possible to specify the program stack size from
7941 @code{gnatlink} using either:
7945 @item using @option{-Xlinker} linker option
7948 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
7951 This sets the stack reserve size to 0x10000 bytes and the stack commit
7952 size to 0x1000 bytes.
7954 @item using @option{-Wl} linker option
7957 $ gnatlink hello -Wl,--stack=0x1000000
7960 This sets the stack reserve size to 0x1000000 bytes. Note that with
7961 @option{-Wl} option it is not possible to set the stack commit size
7962 because the coma is a separator for this option.
7966 @node Setting Heap Size from gnatlink
7967 @section Setting Heap Size from @code{gnatlink}
7970 Under Windows systems, it is possible to specify the program heap size from
7971 @code{gnatlink} using either:
7975 @item using @option{-Xlinker} linker option
7978 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
7981 This sets the heap reserve size to 0x10000 bytes and the heap commit
7982 size to 0x1000 bytes.
7984 @item using @option{-Wl} linker option
7987 $ gnatlink hello -Wl,--heap=0x1000000
7990 This sets the heap reserve size to 0x1000000 bytes. Note that with
7991 @option{-Wl} option it is not possible to set the heap commit size
7992 because the coma is a separator for this option.
7996 @node The GNAT Make Program gnatmake
7997 @chapter The GNAT Make Program @code{gnatmake}
8001 * Running gnatmake::
8002 * Switches for gnatmake::
8003 * Mode Switches for gnatmake::
8004 * Notes on the Command Line::
8005 * How gnatmake Works::
8006 * Examples of gnatmake Usage::
8009 A typical development cycle when working on an Ada program consists of
8010 the following steps:
8014 Edit some sources to fix bugs.
8020 Compile all sources affected.
8030 The third step can be tricky, because not only do the modified files
8031 @cindex Dependency rules
8032 have to be compiled, but any files depending on these files must also be
8033 recompiled. The dependency rules in Ada can be quite complex, especially
8034 in the presence of overloading, @code{use} clauses, generics and inlined
8037 @code{gnatmake} automatically takes care of the third and fourth steps
8038 of this process. It determines which sources need to be compiled,
8039 compiles them, and binds and links the resulting object files.
8041 Unlike some other Ada make programs, the dependencies are always
8042 accurately recomputed from the new sources. The source based approach of
8043 the GNAT compilation model makes this possible. This means that if
8044 changes to the source program cause corresponding changes in
8045 dependencies, they will always be tracked exactly correctly by
8048 @node Running gnatmake
8049 @section Running @code{gnatmake}
8052 The usual form of the @code{gnatmake} command is
8055 $ gnatmake [@var{switches}] @var{file_name}
8056 [@var{file_names}] [@var{mode_switches}]
8060 The only required argument is one @var{file_name}, which specifies
8061 a compilation unit that is a main program. Several @var{file_names} can be
8062 specified: this will result in several executables being built.
8063 If @code{switches} are present, they can be placed before the first
8064 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8065 If @var{mode_switches} are present, they must always be placed after
8066 the last @var{file_name} and all @code{switches}.
8068 If you are using standard file extensions (.adb and .ads), then the
8069 extension may be omitted from the @var{file_name} arguments. However, if
8070 you are using non-standard extensions, then it is required that the
8071 extension be given. A relative or absolute directory path can be
8072 specified in a @var{file_name}, in which case, the input source file will
8073 be searched for in the specified directory only. Otherwise, the input
8074 source file will first be searched in the directory where
8075 @code{gnatmake} was invoked and if it is not found, it will be search on
8076 the source path of the compiler as described in
8077 @ref{Search Paths and the Run-Time Library (RTL)}.
8079 All @code{gnatmake} output (except when you specify
8080 @option{^-M^/DEPENDENCIES_LIST^}) is to
8081 @file{stderr}. The output produced by the
8082 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8085 @node Switches for gnatmake
8086 @section Switches for @code{gnatmake}
8089 You may specify any of the following switches to @code{gnatmake}:
8094 @item --GCC=@var{compiler_name}
8095 @cindex @option{--GCC=compiler_name} (@code{gnatmake})
8096 Program used for compiling. The default is `@code{gcc}'. You need to use
8097 quotes around @var{compiler_name} if @code{compiler_name} contains
8098 spaces or other separator characters. As an example @option{--GCC="foo -x
8099 -y"} will instruct @code{gnatmake} to use @code{foo -x -y} as your
8100 compiler. Note that switch @option{-c} is always inserted after your
8101 command name. Thus in the above example the compiler command that will
8102 be used by @code{gnatmake} will be @code{foo -c -x -y}.
8103 If several @option{--GCC=compiler_name} are used, only the last
8104 @var{compiler_name} is taken into account. However, all the additional
8105 switches are also taken into account. Thus,
8106 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8107 @option{--GCC="bar -x -y -z -t"}.
8109 @item --GNATBIND=@var{binder_name}
8110 @cindex @option{--GNATBIND=binder_name} (@code{gnatmake})
8111 Program used for binding. The default is `@code{gnatbind}'. You need to
8112 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8113 or other separator characters. As an example @option{--GNATBIND="bar -x
8114 -y"} will instruct @code{gnatmake} to use @code{bar -x -y} as your
8115 binder. Binder switches that are normally appended by @code{gnatmake} to
8116 `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8118 @item --GNATLINK=@var{linker_name}
8119 @cindex @option{--GNATLINK=linker_name} (@code{gnatmake})
8120 Program used for linking. The default is `@code{gnatlink}'. You need to
8121 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8122 or other separator characters. As an example @option{--GNATLINK="lan -x
8123 -y"} will instruct @code{gnatmake} to use @code{lan -x -y} as your
8124 linker. Linker switches that are normally appended by @code{gnatmake} to
8125 `@code{gnatlink}' are now appended to the end of @code{lan -x -y}.
8129 @item ^-a^/ALL_FILES^
8130 @cindex @option{^-a^/ALL_FILES^} (@code{gnatmake})
8131 Consider all files in the make process, even the GNAT internal system
8132 files (for example, the predefined Ada library files), as well as any
8133 locked files. Locked files are files whose ALI file is write-protected.
8135 @code{gnatmake} does not check these files,
8136 because the assumption is that the GNAT internal files are properly up
8137 to date, and also that any write protected ALI files have been properly
8138 installed. Note that if there is an installation problem, such that one
8139 of these files is not up to date, it will be properly caught by the
8141 You may have to specify this switch if you are working on GNAT
8142 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8143 in conjunction with @option{^-f^/FORCE_COMPILE^}
8144 if you need to recompile an entire application,
8145 including run-time files, using special configuration pragmas,
8146 such as a @code{Normalize_Scalars} pragma.
8149 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8152 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8155 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8158 @item ^-b^/ACTIONS=BIND^
8159 @cindex @option{^-b^/ACTIONS=BIND^} (@code{gnatmake})
8160 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8161 compilation and binding, but no link.
8162 Can be combined with @option{^-l^/ACTIONS=LINK^}
8163 to do binding and linking. When not combined with
8164 @option{^-c^/ACTIONS=COMPILE^}
8165 all the units in the closure of the main program must have been previously
8166 compiled and must be up to date. The root unit specified by @var{file_name}
8167 may be given without extension, with the source extension or, if no GNAT
8168 Project File is specified, with the ALI file extension.
8170 @item ^-c^/ACTIONS=COMPILE^
8171 @cindex @option{^-c^/ACTIONS=COMPILE^} (@code{gnatmake})
8172 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8173 is also specified. Do not perform linking, except if both
8174 @option{^-b^/ACTIONS=BIND^} and
8175 @option{^-l^/ACTIONS=LINK^} are also specified.
8176 If the root unit specified by @var{file_name} is not a main unit, this is the
8177 default. Otherwise @code{gnatmake} will attempt binding and linking
8178 unless all objects are up to date and the executable is more recent than
8182 @cindex @option{^-C^/MAPPING^} (@code{gnatmake})
8183 Use a temporary mapping file. A mapping file is a way to communicate to the
8184 compiler two mappings: from unit names to file names (without any directory
8185 information) and from file names to path names (with full directory
8186 information). These mappings are used by the compiler to short-circuit the path
8187 search. When @code{gnatmake} is invoked with this switch, it will create
8188 a temporary mapping file, initially populated by the project manager,
8189 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8190 Each invocation of the compiler will add the newly accessed sources to the
8191 mapping file. This will improve the source search during the next invocation
8194 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8195 @cindex @option{^-C=^/USE_MAPPING^} (@code{gnatmake})
8196 Use a specific mapping file. The file, specified as a path name (absolute or
8197 relative) by this switch, should already exist, otherwise the switch is
8198 ineffective. The specified mapping file will be communicated to the compiler.
8199 This switch is not compatible with a project file
8200 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
8201 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
8203 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
8204 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatmake})
8205 Put all object files and ALI file in directory @var{dir}.
8206 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
8207 and ALI files go in the current working directory.
8209 This switch cannot be used when using a project file.
8213 @cindex @option{-eL} (@code{gnatmake})
8214 Follow all symbolic links when processing project files.
8217 @item ^-f^/FORCE_COMPILE^
8218 @cindex @option{^-f^/FORCE_COMPILE^} (@code{gnatmake})
8219 Force recompilations. Recompile all sources, even though some object
8220 files may be up to date, but don't recompile predefined or GNAT internal
8221 files or locked files (files with a write-protected ALI file),
8222 unless the @option{^-a^/ALL_FILES^} switch is also specified.
8224 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
8225 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatmake})
8226 When using project files, if some errors or warnings are detected during
8227 parsing and verbose mode is not in effect (no use of switch
8228 ^-v^/VERBOSE^), then error lines start with the full path name of the project
8229 file, rather than its simple file name.
8231 @item ^-i^/IN_PLACE^
8232 @cindex @option{^-i^/IN_PLACE^} (@code{gnatmake})
8233 In normal mode, @code{gnatmake} compiles all object files and ALI files
8234 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
8235 then instead object files and ALI files that already exist are overwritten
8236 in place. This means that once a large project is organized into separate
8237 directories in the desired manner, then @code{gnatmake} will automatically
8238 maintain and update this organization. If no ALI files are found on the
8239 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
8240 the new object and ALI files are created in the
8241 directory containing the source being compiled. If another organization
8242 is desired, where objects and sources are kept in different directories,
8243 a useful technique is to create dummy ALI files in the desired directories.
8244 When detecting such a dummy file, @code{gnatmake} will be forced to recompile
8245 the corresponding source file, and it will be put the resulting object
8246 and ALI files in the directory where it found the dummy file.
8248 @item ^-j^/PROCESSES=^@var{n}
8249 @cindex @option{^-j^/PROCESSES^} (@code{gnatmake})
8250 @cindex Parallel make
8251 Use @var{n} processes to carry out the (re)compilations. On a
8252 multiprocessor machine compilations will occur in parallel. In the
8253 event of compilation errors, messages from various compilations might
8254 get interspersed (but @code{gnatmake} will give you the full ordered
8255 list of failing compiles at the end). If this is problematic, rerun
8256 the make process with n set to 1 to get a clean list of messages.
8258 @item ^-k^/CONTINUE_ON_ERROR^
8259 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@code{gnatmake})
8260 Keep going. Continue as much as possible after a compilation error. To
8261 ease the programmer's task in case of compilation errors, the list of
8262 sources for which the compile fails is given when @code{gnatmake}
8265 If @code{gnatmake} is invoked with several @file{file_names} and with this
8266 switch, if there are compilation errors when building an executable,
8267 @code{gnatmake} will not attempt to build the following executables.
8269 @item ^-l^/ACTIONS=LINK^
8270 @cindex @option{^-l^/ACTIONS=LINK^} (@code{gnatmake})
8271 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
8272 and linking. Linking will not be performed if combined with
8273 @option{^-c^/ACTIONS=COMPILE^}
8274 but not with @option{^-b^/ACTIONS=BIND^}.
8275 When not combined with @option{^-b^/ACTIONS=BIND^}
8276 all the units in the closure of the main program must have been previously
8277 compiled and must be up to date, and the main program need to have been bound.
8278 The root unit specified by @var{file_name}
8279 may be given without extension, with the source extension or, if no GNAT
8280 Project File is specified, with the ALI file extension.
8282 @item ^-m^/MINIMAL_RECOMPILATION^
8283 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@code{gnatmake})
8284 Specifies that the minimum necessary amount of recompilations
8285 be performed. In this mode @code{gnatmake} ignores time
8286 stamp differences when the only
8287 modifications to a source file consist in adding/removing comments,
8288 empty lines, spaces or tabs. This means that if you have changed the
8289 comments in a source file or have simply reformatted it, using this
8290 switch will tell gnatmake not to recompile files that depend on it
8291 (provided other sources on which these files depend have undergone no
8292 semantic modifications). Note that the debugging information may be
8293 out of date with respect to the sources if the @option{-m} switch causes
8294 a compilation to be switched, so the use of this switch represents a
8295 trade-off between compilation time and accurate debugging information.
8297 @item ^-M^/DEPENDENCIES_LIST^
8298 @cindex Dependencies, producing list
8299 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@code{gnatmake})
8300 Check if all objects are up to date. If they are, output the object
8301 dependences to @file{stdout} in a form that can be directly exploited in
8302 a @file{Makefile}. By default, each source file is prefixed with its
8303 (relative or absolute) directory name. This name is whatever you
8304 specified in the various @option{^-aI^/SOURCE_SEARCH^}
8305 and @option{^-I^/SEARCH^} switches. If you use
8306 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
8307 @option{^-q^/QUIET^}
8308 (see below), only the source file names,
8309 without relative paths, are output. If you just specify the
8310 @option{^-M^/DEPENDENCIES_LIST^}
8311 switch, dependencies of the GNAT internal system files are omitted. This
8312 is typically what you want. If you also specify
8313 the @option{^-a^/ALL_FILES^} switch,
8314 dependencies of the GNAT internal files are also listed. Note that
8315 dependencies of the objects in external Ada libraries (see switch
8316 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
8319 @item ^-n^/DO_OBJECT_CHECK^
8320 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@code{gnatmake})
8321 Don't compile, bind, or link. Checks if all objects are up to date.
8322 If they are not, the full name of the first file that needs to be
8323 recompiled is printed.
8324 Repeated use of this option, followed by compiling the indicated source
8325 file, will eventually result in recompiling all required units.
8327 @item ^-o ^/EXECUTABLE=^@var{exec_name}
8328 @cindex @option{^-o^/EXECUTABLE^} (@code{gnatmake})
8329 Output executable name. The name of the final executable program will be
8330 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
8331 name for the executable will be the name of the input file in appropriate form
8332 for an executable file on the host system.
8334 This switch cannot be used when invoking @code{gnatmake} with several
8337 @item ^-P^/PROJECT_FILE=^@var{project}
8338 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatmake})
8339 Use project file @var{project}. Only one such switch can be used.
8340 See @ref{gnatmake and Project Files}.
8343 @cindex @option{^-q^/QUIET^} (@code{gnatmake})
8344 Quiet. When this flag is not set, the commands carried out by
8345 @code{gnatmake} are displayed.
8347 @item ^-s^/SWITCH_CHECK/^
8348 @cindex @option{^-s^/SWITCH_CHECK^} (@code{gnatmake})
8349 Recompile if compiler switches have changed since last compilation.
8350 All compiler switches but -I and -o are taken into account in the
8352 orders between different ``first letter'' switches are ignored, but
8353 orders between same switches are taken into account. For example,
8354 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
8355 is equivalent to @option{-O -g}.
8357 This switch is recommended when Integrated Preprocessing is used.
8360 @cindex @option{^-u^/UNIQUE^} (@code{gnatmake})
8361 Unique. Recompile at most the main files. It implies -c. Combined with
8362 -f, it is equivalent to calling the compiler directly. Note that using
8363 ^-u^/UNIQUE^ with a project file and no main has a special meaning
8364 (see @ref{Project Files and Main Subprograms}).
8366 @item ^-U^/ALL_PROJECTS^
8367 @cindex @option{^-U^/ALL_PROJECTS^} (@code{gnatmake})
8368 When used without a project file or with one or several mains on the command
8369 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
8370 on the command line, all sources of all project files are checked and compiled
8371 if not up to date, and libraries are rebuilt, if necessary.
8374 @cindex @option{^-v^/REASONS^} (@code{gnatmake})
8375 Verbose. Displays the reason for all recompilations @code{gnatmake}
8376 decides are necessary.
8378 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
8379 Indicates the verbosity of the parsing of GNAT project files.
8380 See @ref{Switches Related to Project Files}.
8382 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
8383 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@code{gnatmake})
8384 Indicates that sources that are not part of any Project File may be compiled.
8385 Normally, when using Project Files, only sources that are part of a Project
8386 File may be compile. When this switch is used, a source outside of all Project
8387 Files may be compiled. The ALI file and the object file will be put in the
8388 object directory of the main Project. The compilation switches used will only
8389 be those specified on the command line.
8391 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
8392 Indicates that external variable @var{name} has the value @var{value}.
8393 The Project Manager will use this value for occurrences of
8394 @code{external(name)} when parsing the project file.
8395 See @ref{Switches Related to Project Files}.
8398 @cindex @option{^-z^/NOMAIN^} (@code{gnatmake})
8399 No main subprogram. Bind and link the program even if the unit name
8400 given on the command line is a package name. The resulting executable
8401 will execute the elaboration routines of the package and its closure,
8402 then the finalization routines.
8405 @cindex @option{^-g^/DEBUG^} (@code{gnatmake})
8406 Enable debugging. This switch is simply passed to the compiler and to the
8412 @item @code{gcc} @asis{switches}
8414 Any uppercase or multi-character switch that is not a @code{gnatmake} switch
8415 is passed to @code{gcc} (e.g. @option{-O}, @option{-gnato,} etc.)
8418 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
8419 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
8420 automatically treated as a compiler switch, and passed on to all
8421 compilations that are carried out.
8426 Source and library search path switches:
8430 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
8431 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatmake})
8432 When looking for source files also look in directory @var{dir}.
8433 The order in which source files search is undertaken is
8434 described in @ref{Search Paths and the Run-Time Library (RTL)}.
8436 @item ^-aL^/SKIP_MISSING=^@var{dir}
8437 @cindex @option{^-aL^/SKIP_MISSING^} (@code{gnatmake})
8438 Consider @var{dir} as being an externally provided Ada library.
8439 Instructs @code{gnatmake} to skip compilation units whose @file{.ALI}
8440 files have been located in directory @var{dir}. This allows you to have
8441 missing bodies for the units in @var{dir} and to ignore out of date bodies
8442 for the same units. You still need to specify
8443 the location of the specs for these units by using the switches
8444 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
8445 or @option{^-I^/SEARCH=^@var{dir}}.
8446 Note: this switch is provided for compatibility with previous versions
8447 of @code{gnatmake}. The easier method of causing standard libraries
8448 to be excluded from consideration is to write-protect the corresponding
8451 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
8452 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatmake})
8453 When searching for library and object files, look in directory
8454 @var{dir}. The order in which library files are searched is described in
8455 @ref{Search Paths for gnatbind}.
8457 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
8458 @cindex Search paths, for @code{gnatmake}
8459 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@code{gnatmake})
8460 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
8461 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
8463 @item ^-I^/SEARCH=^@var{dir}
8464 @cindex @option{^-I^/SEARCH^} (@code{gnatmake})
8465 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
8466 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
8468 @item ^-I-^/NOCURRENT_DIRECTORY^
8469 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatmake})
8470 @cindex Source files, suppressing search
8471 Do not look for source files in the directory containing the source
8472 file named in the command line.
8473 Do not look for ALI or object files in the directory
8474 where @code{gnatmake} was invoked.
8476 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
8477 @cindex @option{^-L^/LIBRARY_SEARCH^} (@code{gnatmake})
8478 @cindex Linker libraries
8479 Add directory @var{dir} to the list of directories in which the linker
8480 will search for libraries. This is equivalent to
8481 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
8483 Furthermore, under Windows, the sources pointed to by the libraries path
8484 set in the registry are not searched for.
8488 @cindex @option{-nostdinc} (@code{gnatmake})
8489 Do not look for source files in the system default directory.
8492 @cindex @option{-nostdlib} (@code{gnatmake})
8493 Do not look for library files in the system default directory.
8495 @item --RTS=@var{rts-path}
8496 @cindex @option{--RTS} (@code{gnatmake})
8497 Specifies the default location of the runtime library. GNAT looks for the
8499 in the following directories, and stops as soon as a valid runtime is found
8500 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
8501 @file{ada_object_path} present):
8504 @item <current directory>/$rts_path
8506 @item <default-search-dir>/$rts_path
8508 @item <default-search-dir>/rts-$rts_path
8512 The selected path is handled like a normal RTS path.
8516 @node Mode Switches for gnatmake
8517 @section Mode Switches for @code{gnatmake}
8520 The mode switches (referred to as @code{mode_switches}) allow the
8521 inclusion of switches that are to be passed to the compiler itself, the
8522 binder or the linker. The effect of a mode switch is to cause all
8523 subsequent switches up to the end of the switch list, or up to the next
8524 mode switch, to be interpreted as switches to be passed on to the
8525 designated component of GNAT.
8529 @item -cargs @var{switches}
8530 @cindex @option{-cargs} (@code{gnatmake})
8531 Compiler switches. Here @var{switches} is a list of switches
8532 that are valid switches for @code{gcc}. They will be passed on to
8533 all compile steps performed by @code{gnatmake}.
8535 @item -bargs @var{switches}
8536 @cindex @option{-bargs} (@code{gnatmake})
8537 Binder switches. Here @var{switches} is a list of switches
8538 that are valid switches for @code{gnatbind}. They will be passed on to
8539 all bind steps performed by @code{gnatmake}.
8541 @item -largs @var{switches}
8542 @cindex @option{-largs} (@code{gnatmake})
8543 Linker switches. Here @var{switches} is a list of switches
8544 that are valid switches for @code{gnatlink}. They will be passed on to
8545 all link steps performed by @code{gnatmake}.
8547 @item -margs @var{switches}
8548 @cindex @option{-margs} (@code{gnatmake})
8549 Make switches. The switches are directly interpreted by @code{gnatmake},
8550 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
8554 @node Notes on the Command Line
8555 @section Notes on the Command Line
8558 This section contains some additional useful notes on the operation
8559 of the @code{gnatmake} command.
8563 @cindex Recompilation, by @code{gnatmake}
8564 If @code{gnatmake} finds no ALI files, it recompiles the main program
8565 and all other units required by the main program.
8566 This means that @code{gnatmake}
8567 can be used for the initial compile, as well as during subsequent steps of
8568 the development cycle.
8571 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
8572 is a subunit or body of a generic unit, @code{gnatmake} recompiles
8573 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
8577 In @code{gnatmake} the switch @option{^-I^/SEARCH^}
8578 is used to specify both source and
8579 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8580 instead if you just want to specify
8581 source paths only and @option{^-aO^/OBJECT_SEARCH^}
8582 if you want to specify library paths
8586 @code{gnatmake} examines both an ALI file and its corresponding object file
8587 for consistency. If an ALI is more recent than its corresponding object,
8588 or if the object file is missing, the corresponding source will be recompiled.
8589 Note that @code{gnatmake} expects an ALI and the corresponding object file
8590 to be in the same directory.
8593 @code{gnatmake} will ignore any files whose ALI file is write-protected.
8594 This may conveniently be used to exclude standard libraries from
8595 consideration and in particular it means that the use of the
8596 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
8597 unless @option{^-a^/ALL_FILES^} is also specified.
8600 @code{gnatmake} has been designed to make the use of Ada libraries
8601 particularly convenient. Assume you have an Ada library organized
8602 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
8603 of your Ada compilation units,
8604 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
8605 specs of these units, but no bodies. Then to compile a unit
8606 stored in @code{main.adb}, which uses this Ada library you would just type
8610 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
8613 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
8614 /SKIP_MISSING=@i{[OBJ_DIR]} main
8619 Using @code{gnatmake} along with the
8620 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
8621 switch provides a mechanism for avoiding unnecessary rcompilations. Using
8623 you can update the comments/format of your
8624 source files without having to recompile everything. Note, however, that
8625 adding or deleting lines in a source files may render its debugging
8626 info obsolete. If the file in question is a spec, the impact is rather
8627 limited, as that debugging info will only be useful during the
8628 elaboration phase of your program. For bodies the impact can be more
8629 significant. In all events, your debugger will warn you if a source file
8630 is more recent than the corresponding object, and alert you to the fact
8631 that the debugging information may be out of date.
8634 @node How gnatmake Works
8635 @section How @code{gnatmake} Works
8638 Generally @code{gnatmake} automatically performs all necessary
8639 recompilations and you don't need to worry about how it works. However,
8640 it may be useful to have some basic understanding of the @code{gnatmake}
8641 approach and in particular to understand how it uses the results of
8642 previous compilations without incorrectly depending on them.
8644 First a definition: an object file is considered @dfn{up to date} if the
8645 corresponding ALI file exists and its time stamp predates that of the
8646 object file and if all the source files listed in the
8647 dependency section of this ALI file have time stamps matching those in
8648 the ALI file. This means that neither the source file itself nor any
8649 files that it depends on have been modified, and hence there is no need
8650 to recompile this file.
8652 @code{gnatmake} works by first checking if the specified main unit is up
8653 to date. If so, no compilations are required for the main unit. If not,
8654 @code{gnatmake} compiles the main program to build a new ALI file that
8655 reflects the latest sources. Then the ALI file of the main unit is
8656 examined to find all the source files on which the main program depends,
8657 and @code{gnatmake} recursively applies the above procedure on all these files.
8659 This process ensures that @code{gnatmake} only trusts the dependencies
8660 in an existing ALI file if they are known to be correct. Otherwise it
8661 always recompiles to determine a new, guaranteed accurate set of
8662 dependencies. As a result the program is compiled ``upside down'' from what may
8663 be more familiar as the required order of compilation in some other Ada
8664 systems. In particular, clients are compiled before the units on which
8665 they depend. The ability of GNAT to compile in any order is critical in
8666 allowing an order of compilation to be chosen that guarantees that
8667 @code{gnatmake} will recompute a correct set of new dependencies if
8670 When invoking @code{gnatmake} with several @var{file_names}, if a unit is
8671 imported by several of the executables, it will be recompiled at most once.
8673 Note: when using non-standard naming conventions
8674 (See @ref{Using Other File Names}), changing through a configuration pragmas
8675 file the version of a source and invoking @code{gnatmake} to recompile may
8676 have no effect, if the previous version of the source is still accessible
8677 by @code{gnatmake}. It may be necessary to use the switch ^-f^/FORCE_COMPILE^.
8679 @node Examples of gnatmake Usage
8680 @section Examples of @code{gnatmake} Usage
8683 @item gnatmake hello.adb
8684 Compile all files necessary to bind and link the main program
8685 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
8686 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
8688 @item gnatmake main1 main2 main3
8689 Compile all files necessary to bind and link the main programs
8690 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
8691 (containing unit @code{Main2}) and @file{main3.adb}
8692 (containing unit @code{Main3}) and bind and link the resulting object files
8693 to generate three executable files @file{^main1^MAIN1.EXE^},
8694 @file{^main2^MAIN2.EXE^}
8695 and @file{^main3^MAIN3.EXE^}.
8698 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
8702 @item gnatmake Main_Unit /QUIET
8703 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
8704 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
8706 Compile all files necessary to bind and link the main program unit
8707 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
8708 be done with optimization level 2 and the order of elaboration will be
8709 listed by the binder. @code{gnatmake} will operate in quiet mode, not
8710 displaying commands it is executing.
8714 @c *************************
8715 @node Improving Performance
8716 @chapter Improving Performance
8717 @cindex Improving performance
8720 This chapter presents several topics related to program performance.
8721 It first describes some of the tradeoffs that need to be considered
8722 and some of the techniques for making your program run faster.
8723 It then documents the @command{gnatelim} tool, which can reduce
8724 the size of program executables.
8728 * Performance Considerations::
8729 * Reducing the Size of Ada Executables with gnatelim::
8734 @c *****************************
8735 @node Performance Considerations
8736 @section Performance Considerations
8739 The GNAT system provides a number of options that allow a trade-off
8744 performance of the generated code
8747 speed of compilation
8750 minimization of dependences and recompilation
8753 the degree of run-time checking.
8757 The defaults (if no options are selected) aim at improving the speed
8758 of compilation and minimizing dependences, at the expense of performance
8759 of the generated code:
8766 no inlining of subprogram calls
8769 all run-time checks enabled except overflow and elaboration checks
8773 These options are suitable for most program development purposes. This
8774 chapter describes how you can modify these choices, and also provides
8775 some guidelines on debugging optimized code.
8778 * Controlling Run-Time Checks::
8779 * Use of Restrictions::
8780 * Optimization Levels::
8781 * Debugging Optimized Code::
8782 * Inlining of Subprograms::
8783 * Optimization and Strict Aliasing::
8785 * Coverage Analysis::
8789 @node Controlling Run-Time Checks
8790 @subsection Controlling Run-Time Checks
8793 By default, GNAT generates all run-time checks, except arithmetic overflow
8794 checking for integer operations and checks for access before elaboration on
8795 subprogram calls. The latter are not required in default mode, because all
8796 necessary checking is done at compile time.
8797 @cindex @option{-gnatp} (@code{gcc})
8798 @cindex @option{-gnato} (@code{gcc})
8799 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
8800 be modified. @xref{Run-Time Checks}.
8802 Our experience is that the default is suitable for most development
8805 We treat integer overflow specially because these
8806 are quite expensive and in our experience are not as important as other
8807 run-time checks in the development process. Note that division by zero
8808 is not considered an overflow check, and divide by zero checks are
8809 generated where required by default.
8811 Elaboration checks are off by default, and also not needed by default, since
8812 GNAT uses a static elaboration analysis approach that avoids the need for
8813 run-time checking. This manual contains a full chapter discussing the issue
8814 of elaboration checks, and if the default is not satisfactory for your use,
8815 you should read this chapter.
8817 For validity checks, the minimal checks required by the Ada Reference
8818 Manual (for case statements and assignments to array elements) are on
8819 by default. These can be suppressed by use of the @option{-gnatVn} switch.
8820 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
8821 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
8822 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
8823 are also suppressed entirely if @option{-gnatp} is used.
8825 @cindex Overflow checks
8826 @cindex Checks, overflow
8829 @cindex pragma Suppress
8830 @cindex pragma Unsuppress
8831 Note that the setting of the switches controls the default setting of
8832 the checks. They may be modified using either @code{pragma Suppress} (to
8833 remove checks) or @code{pragma Unsuppress} (to add back suppressed
8834 checks) in the program source.
8836 @node Use of Restrictions
8837 @subsection Use of Restrictions
8840 The use of pragma Restrictions allows you to control which features are
8841 permitted in your program. Apart from the obvious point that if you avoid
8842 relatively expensive features like finalization (enforceable by the use
8843 of pragma Restrictions (No_Finalization), the use of this pragma does not
8844 affect the generated code in most cases.
8846 One notable exception to this rule is that the possibility of task abort
8847 results in some distributed overhead, particularly if finalization or
8848 exception handlers are used. The reason is that certain sections of code
8849 have to be marked as non-abortable.
8851 If you use neither the @code{abort} statement, nor asynchronous transfer
8852 of control (@code{select .. then abort}), then this distributed overhead
8853 is removed, which may have a general positive effect in improving
8854 overall performance. Especially code involving frequent use of tasking
8855 constructs and controlled types will show much improved performance.
8856 The relevant restrictions pragmas are
8859 pragma Restrictions (No_Abort_Statements);
8860 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
8864 It is recommended that these restriction pragmas be used if possible. Note
8865 that this also means that you can write code without worrying about the
8866 possibility of an immediate abort at any point.
8868 @node Optimization Levels
8869 @subsection Optimization Levels
8870 @cindex @option{^-O^/OPTIMIZE^} (@code{gcc})
8873 The default is optimization off. This results in the fastest compile
8874 times, but GNAT makes absolutely no attempt to optimize, and the
8875 generated programs are considerably larger and slower than when
8876 optimization is enabled. You can use the
8878 @option{-O@var{n}} switch, where @var{n} is an integer from 0 to 3,
8881 @code{OPTIMIZE} qualifier
8883 to @code{gcc} to control the optimization level:
8886 @item ^-O0^/OPTIMIZE=NONE^
8887 No optimization (the default);
8888 generates unoptimized code but has
8889 the fastest compilation time.
8891 @item ^-O1^/OPTIMIZE=SOME^
8892 Medium level optimization;
8893 optimizes reasonably well but does not
8894 degrade compilation time significantly.
8896 @item ^-O2^/OPTIMIZE=ALL^
8898 @itemx /OPTIMIZE=DEVELOPMENT
8901 generates highly optimized code and has
8902 the slowest compilation time.
8904 @item ^-O3^/OPTIMIZE=INLINING^
8905 Full optimization as in @option{-O2},
8906 and also attempts automatic inlining of small
8907 subprograms within a unit (@pxref{Inlining of Subprograms}).
8911 Higher optimization levels perform more global transformations on the
8912 program and apply more expensive analysis algorithms in order to generate
8913 faster and more compact code. The price in compilation time, and the
8914 resulting improvement in execution time,
8915 both depend on the particular application and the hardware environment.
8916 You should experiment to find the best level for your application.
8918 Since the precise set of optimizations done at each level will vary from
8919 release to release (and sometime from target to target), it is best to think
8920 of the optimization settings in general terms.
8921 The @cite{Using GNU GCC} manual contains details about
8922 ^the @option{-O} settings and a number of @option{-f} options that^how to^
8923 individually enable or disable specific optimizations.
8925 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
8926 been tested extensively at all optimization levels. There are some bugs
8927 which appear only with optimization turned on, but there have also been
8928 bugs which show up only in @emph{unoptimized} code. Selecting a lower
8929 level of optimization does not improve the reliability of the code
8930 generator, which in practice is highly reliable at all optimization
8933 Note regarding the use of @option{-O3}: The use of this optimization level
8934 is generally discouraged with GNAT, since it often results in larger
8935 executables which run more slowly. See further discussion of this point
8936 in @pxref{Inlining of Subprograms}.
8939 @node Debugging Optimized Code
8940 @subsection Debugging Optimized Code
8941 @cindex Debugging optimized code
8942 @cindex Optimization and debugging
8945 Although it is possible to do a reasonable amount of debugging at
8947 non-zero optimization levels,
8948 the higher the level the more likely that
8951 @option{/OPTIMIZE} settings other than @code{NONE},
8952 such settings will make it more likely that
8954 source-level constructs will have been eliminated by optimization.
8955 For example, if a loop is strength-reduced, the loop
8956 control variable may be completely eliminated and thus cannot be
8957 displayed in the debugger.
8958 This can only happen at @option{-O2} or @option{-O3}.
8959 Explicit temporary variables that you code might be eliminated at
8960 ^level^setting^ @option{-O1} or higher.
8962 The use of the @option{^-g^/DEBUG^} switch,
8963 @cindex @option{^-g^/DEBUG^} (@code{gcc})
8964 which is needed for source-level debugging,
8965 affects the size of the program executable on disk,
8966 and indeed the debugging information can be quite large.
8967 However, it has no effect on the generated code (and thus does not
8968 degrade performance)
8970 Since the compiler generates debugging tables for a compilation unit before
8971 it performs optimizations, the optimizing transformations may invalidate some
8972 of the debugging data. You therefore need to anticipate certain
8973 anomalous situations that may arise while debugging optimized code.
8974 These are the most common cases:
8978 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
8980 the PC bouncing back and forth in the code. This may result from any of
8981 the following optimizations:
8985 @i{Common subexpression elimination:} using a single instance of code for a
8986 quantity that the source computes several times. As a result you
8987 may not be able to stop on what looks like a statement.
8990 @i{Invariant code motion:} moving an expression that does not change within a
8991 loop, to the beginning of the loop.
8994 @i{Instruction scheduling:} moving instructions so as to
8995 overlap loads and stores (typically) with other code, or in
8996 general to move computations of values closer to their uses. Often
8997 this causes you to pass an assignment statement without the assignment
8998 happening and then later bounce back to the statement when the
8999 value is actually needed. Placing a breakpoint on a line of code
9000 and then stepping over it may, therefore, not always cause all the
9001 expected side-effects.
9005 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
9006 two identical pieces of code are merged and the program counter suddenly
9007 jumps to a statement that is not supposed to be executed, simply because
9008 it (and the code following) translates to the same thing as the code
9009 that @emph{was} supposed to be executed. This effect is typically seen in
9010 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
9011 a @code{break} in a C @code{^switch^switch^} statement.
9014 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
9015 There are various reasons for this effect:
9019 In a subprogram prologue, a parameter may not yet have been moved to its
9023 A variable may be dead, and its register re-used. This is
9024 probably the most common cause.
9027 As mentioned above, the assignment of a value to a variable may
9031 A variable may be eliminated entirely by value propagation or
9032 other means. In this case, GCC may incorrectly generate debugging
9033 information for the variable
9037 In general, when an unexpected value appears for a local variable or parameter
9038 you should first ascertain if that value was actually computed by
9039 your program, as opposed to being incorrectly reported by the debugger.
9041 array elements in an object designated by an access value
9042 are generally less of a problem, once you have ascertained that the access
9044 Typically, this means checking variables in the preceding code and in the
9045 calling subprogram to verify that the value observed is explainable from other
9046 values (one must apply the procedure recursively to those
9047 other values); or re-running the code and stopping a little earlier
9048 (perhaps before the call) and stepping to better see how the variable obtained
9049 the value in question; or continuing to step @emph{from} the point of the
9050 strange value to see if code motion had simply moved the variable's
9055 In light of such anomalies, a recommended technique is to use @option{-O0}
9056 early in the software development cycle, when extensive debugging capabilities
9057 are most needed, and then move to @option{-O1} and later @option{-O2} as
9058 the debugger becomes less critical.
9059 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9060 a release management issue.
9062 Note that if you use @option{-g} you can then use the @command{strip} program
9063 on the resulting executable,
9064 which removes both debugging information and global symbols.
9068 @node Inlining of Subprograms
9069 @subsection Inlining of Subprograms
9072 A call to a subprogram in the current unit is inlined if all the
9073 following conditions are met:
9077 The optimization level is at least @option{-O1}.
9080 The called subprogram is suitable for inlining: It must be small enough
9081 and not contain nested subprograms or anything else that @code{gcc}
9082 cannot support in inlined subprograms.
9085 The call occurs after the definition of the body of the subprogram.
9088 @cindex pragma Inline
9090 Either @code{pragma Inline} applies to the subprogram or it is
9091 small and automatic inlining (optimization level @option{-O3}) is
9096 Calls to subprograms in @code{with}'ed units are normally not inlined.
9097 To achieve this level of inlining, the following conditions must all be
9102 The optimization level is at least @option{-O1}.
9105 The called subprogram is suitable for inlining: It must be small enough
9106 and not contain nested subprograms or anything else @code{gcc} cannot
9107 support in inlined subprograms.
9110 The call appears in a body (not in a package spec).
9113 There is a @code{pragma Inline} for the subprogram.
9116 @cindex @option{-gnatn} (@code{gcc})
9117 The @option{^-gnatn^/INLINE^} switch
9118 is used in the @code{gcc} command line
9121 Note that specifying the @option{-gnatn} switch causes additional
9122 compilation dependencies. Consider the following:
9124 @smallexample @c ada
9144 With the default behavior (no @option{-gnatn} switch specified), the
9145 compilation of the @code{Main} procedure depends only on its own source,
9146 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
9147 means that editing the body of @code{R} does not require recompiling
9150 On the other hand, the call @code{R.Q} is not inlined under these
9151 circumstances. If the @option{-gnatn} switch is present when @code{Main}
9152 is compiled, the call will be inlined if the body of @code{Q} is small
9153 enough, but now @code{Main} depends on the body of @code{R} in
9154 @file{r.adb} as well as on the spec. This means that if this body is edited,
9155 the main program must be recompiled. Note that this extra dependency
9156 occurs whether or not the call is in fact inlined by @code{gcc}.
9158 The use of front end inlining with @option{-gnatN} generates similar
9159 additional dependencies.
9161 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@code{gcc})
9162 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
9163 can be used to prevent
9164 all inlining. This switch overrides all other conditions and ensures
9165 that no inlining occurs. The extra dependences resulting from
9166 @option{-gnatn} will still be active, even if
9167 this switch is used to suppress the resulting inlining actions.
9169 Note regarding the use of @option{-O3}: There is no difference in inlining
9170 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
9171 pragma @code{Inline} assuming the use of @option{-gnatn}
9172 or @option{-gnatN} (the switches that activate inlining). If you have used
9173 pragma @code{Inline} in appropriate cases, then it is usually much better
9174 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
9175 in this case only has the effect of inlining subprograms you did not
9176 think should be inlined. We often find that the use of @option{-O3} slows
9177 down code by performing excessive inlining, leading to increased instruction
9178 cache pressure from the increased code size. So the bottom line here is
9179 that you should not automatically assume that @option{-O3} is better than
9180 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
9181 it actually improves performance.
9183 @node Optimization and Strict Aliasing
9184 @subsection Optimization and Strict Aliasing
9186 @cindex Strict Aliasing
9187 @cindex No_Strict_Aliasing
9190 The strong typing capabilities of Ada allow an optimizer to generate
9191 efficient code in situations where other languages would be forced to
9192 make worst case assumptions preventing such optimizations. Consider
9193 the following example:
9195 @smallexample @c ada
9198 type Int1 is new Integer;
9199 type Int2 is new Integer;
9200 type Int1A is access Int1;
9201 type Int2A is access Int2;
9208 for J in Data'Range loop
9209 if Data (J) = Int1V.all then
9210 Int2V.all := Int2V.all + 1;
9219 In this example, since the variable @code{Int1V} can only access objects
9220 of type @code{Int1}, and @code{Int2V} can only access objects of type
9221 @code{Int2}, there is no possibility that the assignment to
9222 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
9223 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
9224 for all iterations of the loop and avoid the extra memory reference
9225 required to dereference it each time through the loop.
9227 This kind of optimziation, called strict aliasing analysis, is
9228 triggered by specifying an optimization level of @option{-O2} or
9229 higher and allows @code{GNAT} to generate more efficient code
9230 when access values are involved.
9232 However, although this optimization is always correct in terms of
9233 the formal semantics of the Ada Reference Manual, difficulties can
9234 arise if features like @code{Unchecked_Conversion} are used to break
9235 the typing system. Consider the following complete program example:
9237 @smallexample @c ada
9240 type int1 is new integer;
9241 type int2 is new integer;
9242 type a1 is access int1;
9243 type a2 is access int2;
9248 function to_a2 (Input : a1) return a2;
9251 with Unchecked_Conversion;
9253 function to_a2 (Input : a1) return a2 is
9255 new Unchecked_Conversion (a1, a2);
9257 return to_a2u (Input);
9263 with Text_IO; use Text_IO;
9265 v1 : a1 := new int1;
9266 v2 : a2 := to_a2 (v1);
9270 put_line (int1'image (v1.all));
9276 This program prints out 0 in @code{-O0} or @code{-O1}
9277 mode, but it prints out 1 in @code{-O2} mode. That's
9278 because in strict aliasing mode, the compiler can and
9279 does assume that the assignment to @code{v2.all} could not
9280 affect the value of @code{v1.all}, since different types
9283 This behavior is not a case of non-conformance with the standard, since
9284 the Ada RM specifies that an unchecked conversion where the resulting
9285 bit pattern is not a correct value of the target type can result in an
9286 abnormal value and attempting to reference an abnormal value makes the
9287 execution of a program erroneous. That's the case here since the result
9288 does not point to an object of type @code{int2}. This means that the
9289 effect is entirely unpredictable.
9291 However, although that explanation may satisfy a language
9292 lawyer, in practice an applications programmer expects an
9293 unchecked conversion involving pointers to create true
9294 aliases and the behavior of printing 1 seems plain wrong.
9295 In this case, the strict aliasing optimization is unwelcome.
9297 Indeed the compiler recognizes this possibility, and the
9298 unchecked conversion generates a warning:
9301 p2.adb:5:07: warning: possible aliasing problem with type "a2"
9302 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
9303 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
9307 Unfortunately the problem is recognized when compiling the body of
9308 package @code{p2}, but the actual "bad" code is generated while
9309 compiling the body of @code{m} and this latter compilation does not see
9310 the suspicious @code{Unchecked_Conversion}.
9312 As implied by the warning message, there are approaches you can use to
9313 avoid the unwanted strict aliasing optimization in a case like this.
9315 One possibility is to simply avoid the use of @code{-O2}, but
9316 that is a bit drastic, since it throws away a number of useful
9317 optimizations that do not involve strict aliasing assumptions.
9319 A less drastic approach is to compile the program using the
9320 option @code{-fno-strict-aliasing}. Actually it is only the
9321 unit containing the dereferencing of the suspicious pointer
9322 that needs to be compiled. So in this case, if we compile
9323 unit @code{m} with this switch, then we get the expected
9324 value of zero printed. Analyzing which units might need
9325 the switch can be painful, so a more reasonable approach
9326 is to compile the entire program with options @code{-O2}
9327 and @code{-fno-strict-aliasing}. If the performance is
9328 satisfactory with this combination of options, then the
9329 advantage is that the entire issue of possible "wrong"
9330 optimization due to strict aliasing is avoided.
9332 To avoid the use of compiler switches, the configuration
9333 pragma @code{No_Strict_Aliasing} with no parameters may be
9334 used to specify that for all access types, the strict
9335 aliasing optimization should be suppressed.
9337 However, these approaches are still overkill, in that they causes
9338 all manipulations of all access values to be deoptimized. A more
9339 refined approach is to concentrate attention on the specific
9340 access type identified as problematic.
9342 First, if a careful analysis of uses of the pointer shows
9343 that there are no possible problematic references, then
9344 the warning can be suppressed by bracketing the
9345 instantiation of @code{Unchecked_Conversion} to turn
9348 @smallexample @c ada
9349 pragma Warnings (Off);
9351 new Unchecked_Conversion (a1, a2);
9352 pragma Warnings (On);
9356 Of course that approach is not appropriate for this particular
9357 example, since indeed there is a problematic reference. In this
9358 case we can take one of two other approaches.
9360 The first possibility is to move the instantiation of unchecked
9361 conversion to the unit in which the type is declared. In
9362 this example, we would move the instantiation of
9363 @code{Unchecked_Conversion} from the body of package
9364 @code{p2} to the spec of package @code{p1}. Now the
9365 warning disappears. That's because any use of the
9366 access type knows there is a suspicious unchecked
9367 conversion, and the strict aliasing optimization
9368 is automatically suppressed for the type.
9370 If it is not practical to move the unchecked conversion to the same unit
9371 in which the destination access type is declared (perhaps because the
9372 source type is not visible in that unit), you may use pragma
9373 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
9374 same declarative sequence as the declaration of the access type:
9376 @smallexample @c ada
9377 type a2 is access int2;
9378 pragma No_Strict_Aliasing (a2);
9382 Here again, the compiler now knows that the strict aliasing optimization
9383 should be suppressed for any reference to type @code{a2} and the
9384 expected behavior is obtained.
9386 Finally, note that although the compiler can generate warnings for
9387 simple cases of unchecked conversions, there are tricker and more
9388 indirect ways of creating type incorrect aliases which the compiler
9389 cannot detect. Examples are the use of address overlays and unchecked
9390 conversions involving composite types containing access types as
9391 components. In such cases, no warnings are generated, but there can
9392 still be aliasing problems. One safe coding practice is to forbid the
9393 use of address clauses for type overlaying, and to allow unchecked
9394 conversion only for primitive types. This is not really a significant
9395 restriction since any possible desired effect can be achieved by
9396 unchecked conversion of access values.
9399 @node Coverage Analysis
9400 @subsection Coverage Analysis
9403 GNAT supports the Digital Performance Coverage Analyzer (PCA), which allows
9404 the user to determine the distribution of execution time across a program,
9405 @pxref{Profiling} for details of usage.
9408 @node Reducing the Size of Ada Executables with gnatelim
9409 @section Reducing the Size of Ada Executables with @code{gnatelim}
9413 This section describes @command{gnatelim}, a tool which detects unused
9414 subprograms and helps the compiler to create a smaller executable for your
9419 * Running gnatelim::
9420 * Correcting the List of Eliminate Pragmas::
9421 * Making Your Executables Smaller::
9422 * Summary of the gnatelim Usage Cycle::
9425 @node About gnatelim
9426 @subsection About @code{gnatelim}
9429 When a program shares a set of Ada
9430 packages with other programs, it may happen that this program uses
9431 only a fraction of the subprograms defined in these packages. The code
9432 created for these unused subprograms increases the size of the executable.
9434 @code{gnatelim} tracks unused subprograms in an Ada program and
9435 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
9436 subprograms that are declared but never called. By placing the list of
9437 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
9438 recompiling your program, you may decrease the size of its executable,
9439 because the compiler will not generate the code for 'eliminated' subprograms.
9440 See GNAT Reference Manual for more information about this pragma.
9442 @code{gnatelim} needs as its input data the name of the main subprogram
9443 and a bind file for a main subprogram.
9445 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
9446 the main subprogram. @code{gnatelim} can work with both Ada and C
9447 bind files; when both are present, it uses the Ada bind file.
9448 The following commands will build the program and create the bind file:
9451 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
9452 $ gnatbind main_prog
9455 Note that @code{gnatelim} needs neither object nor ALI files.
9457 @node Running gnatelim
9458 @subsection Running @code{gnatelim}
9461 @code{gnatelim} has the following command-line interface:
9464 $ gnatelim [options] name
9468 @code{name} should be a name of a source file that contains the main subprogram
9469 of a program (partition).
9471 @code{gnatelim} has the following switches:
9476 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
9477 Quiet mode: by default @code{gnatelim} outputs to the standard error
9478 stream the number of program units left to be processed. This option turns
9482 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
9483 Verbose mode: @code{gnatelim} version information is printed as Ada
9484 comments to the standard output stream. Also, in addition to the number of
9485 program units left @code{gnatelim} will output the name of the current unit
9489 @cindex @option{^-a^/ALL^} (@command{gnatelim})
9490 Also look for subprograms from the GNAT run time that can be eliminated. Note
9491 that when @file{gnat.adc} is produced using this switch, the entire program
9492 must be recompiled with switch @option{^-a^/ALL_FILES^} to @code{gnatmake}.
9494 @item ^-I^/INCLUDE_DIRS=^@var{dir}
9495 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
9496 When looking for source files also look in directory @var{dir}. Specifying
9497 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
9498 sources in the current directory.
9500 @item ^-b^/BIND_FILE=^@var{bind_file}
9501 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
9502 Specifies @var{bind_file} as the bind file to process. If not set, the name
9503 of the bind file is computed from the full expanded Ada name
9504 of a main subprogram.
9506 @item ^-C^/CONFIG_FILE=^@var{config_file}
9507 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
9508 Specifies a file @var{config_file} that contains configuration pragmas. The
9509 file must be specified with full path.
9511 @item ^--GCC^/COMPILER^=@var{compiler_name}
9512 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
9513 Instructs @code{gnatelim} to use specific @code{gcc} compiler instead of one
9514 available on the path.
9516 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
9517 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
9518 Instructs @code{gnatelim} to use specific @code{gnatmake} instead of one
9519 available on the path.
9522 @cindex @option{-d@var{x}} (@command{gnatelim})
9523 Activate internal debugging switches. @var{x} is a letter or digit, or
9524 string of letters or digits, which specifies the type of debugging
9525 mode desired. Normally these are used only for internal development
9526 or system debugging purposes. You can find full documentation for these
9527 switches in the spec of the @code{Gnatelim} unit in the compiler
9528 source file @file{gnatelim.ads}.
9532 @code{gnatelim} sends its output to the standard output stream, and all the
9533 tracing and debug information is sent to the standard error stream.
9534 In order to produce a proper GNAT configuration file
9535 @file{gnat.adc}, redirection must be used:
9539 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
9542 $ gnatelim main_prog.adb > gnat.adc
9551 $ gnatelim main_prog.adb >> gnat.adc
9555 in order to append the @code{gnatelim} output to the existing contents of
9559 @node Correcting the List of Eliminate Pragmas
9560 @subsection Correcting the List of Eliminate Pragmas
9563 In some rare cases @code{gnatelim} may try to eliminate
9564 subprograms that are actually called in the program. In this case, the
9565 compiler will generate an error message of the form:
9568 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
9572 You will need to manually remove the wrong @code{Eliminate} pragmas from
9573 the @file{gnat.adc} file. You should recompile your program
9574 from scratch after that, because you need a consistent @file{gnat.adc} file
9575 during the entire compilation.
9578 @node Making Your Executables Smaller
9579 @subsection Making Your Executables Smaller
9582 In order to get a smaller executable for your program you now have to
9583 recompile the program completely with the new @file{gnat.adc} file
9584 created by @code{gnatelim} in your current directory:
9587 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
9591 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
9592 recompile everything
9593 with the set of pragmas @code{Eliminate} that you have obtained with
9594 @command{gnatelim}).
9596 Be aware that the set of @code{Eliminate} pragmas is specific to each
9597 program. It is not recommended to merge sets of @code{Eliminate}
9598 pragmas created for different programs in one @file{gnat.adc} file.
9600 @node Summary of the gnatelim Usage Cycle
9601 @subsection Summary of the gnatelim Usage Cycle
9604 Here is a quick summary of the steps to be taken in order to reduce
9605 the size of your executables with @code{gnatelim}. You may use
9606 other GNAT options to control the optimization level,
9607 to produce the debugging information, to set search path, etc.
9614 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
9615 $ gnatbind main_prog
9619 Generate a list of @code{Eliminate} pragmas
9622 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
9625 $ gnatelim main_prog >[>] gnat.adc
9630 Recompile the application
9633 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
9641 @c ********************************
9642 @node Renaming Files Using gnatchop
9643 @chapter Renaming Files Using @code{gnatchop}
9647 This chapter discusses how to handle files with multiple units by using
9648 the @code{gnatchop} utility. This utility is also useful in renaming
9649 files to meet the standard GNAT default file naming conventions.
9652 * Handling Files with Multiple Units::
9653 * Operating gnatchop in Compilation Mode::
9654 * Command Line for gnatchop::
9655 * Switches for gnatchop::
9656 * Examples of gnatchop Usage::
9659 @node Handling Files with Multiple Units
9660 @section Handling Files with Multiple Units
9663 The basic compilation model of GNAT requires that a file submitted to the
9664 compiler have only one unit and there be a strict correspondence
9665 between the file name and the unit name.
9667 The @code{gnatchop} utility allows both of these rules to be relaxed,
9668 allowing GNAT to process files which contain multiple compilation units
9669 and files with arbitrary file names. @code{gnatchop}
9670 reads the specified file and generates one or more output files,
9671 containing one unit per file. The unit and the file name correspond,
9672 as required by GNAT.
9674 If you want to permanently restructure a set of ``foreign'' files so that
9675 they match the GNAT rules, and do the remaining development using the
9676 GNAT structure, you can simply use @command{gnatchop} once, generate the
9677 new set of files and work with them from that point on.
9679 Alternatively, if you want to keep your files in the ``foreign'' format,
9680 perhaps to maintain compatibility with some other Ada compilation
9681 system, you can set up a procedure where you use @command{gnatchop} each
9682 time you compile, regarding the source files that it writes as temporary
9683 files that you throw away.
9686 @node Operating gnatchop in Compilation Mode
9687 @section Operating gnatchop in Compilation Mode
9690 The basic function of @code{gnatchop} is to take a file with multiple units
9691 and split it into separate files. The boundary between files is reasonably
9692 clear, except for the issue of comments and pragmas. In default mode, the
9693 rule is that any pragmas between units belong to the previous unit, except
9694 that configuration pragmas always belong to the following unit. Any comments
9695 belong to the following unit. These rules
9696 almost always result in the right choice of
9697 the split point without needing to mark it explicitly and most users will
9698 find this default to be what they want. In this default mode it is incorrect to
9699 submit a file containing only configuration pragmas, or one that ends in
9700 configuration pragmas, to @code{gnatchop}.
9702 However, using a special option to activate ``compilation mode'',
9704 can perform another function, which is to provide exactly the semantics
9705 required by the RM for handling of configuration pragmas in a compilation.
9706 In the absence of configuration pragmas (at the main file level), this
9707 option has no effect, but it causes such configuration pragmas to be handled
9708 in a quite different manner.
9710 First, in compilation mode, if @code{gnatchop} is given a file that consists of
9711 only configuration pragmas, then this file is appended to the
9712 @file{gnat.adc} file in the current directory. This behavior provides
9713 the required behavior described in the RM for the actions to be taken
9714 on submitting such a file to the compiler, namely that these pragmas
9715 should apply to all subsequent compilations in the same compilation
9716 environment. Using GNAT, the current directory, possibly containing a
9717 @file{gnat.adc} file is the representation
9718 of a compilation environment. For more information on the
9719 @file{gnat.adc} file, see the section on handling of configuration
9720 pragmas @pxref{Handling of Configuration Pragmas}.
9722 Second, in compilation mode, if @code{gnatchop}
9723 is given a file that starts with
9724 configuration pragmas, and contains one or more units, then these
9725 configuration pragmas are prepended to each of the chopped files. This
9726 behavior provides the required behavior described in the RM for the
9727 actions to be taken on compiling such a file, namely that the pragmas
9728 apply to all units in the compilation, but not to subsequently compiled
9731 Finally, if configuration pragmas appear between units, they are appended
9732 to the previous unit. This results in the previous unit being illegal,
9733 since the compiler does not accept configuration pragmas that follow
9734 a unit. This provides the required RM behavior that forbids configuration
9735 pragmas other than those preceding the first compilation unit of a
9738 For most purposes, @code{gnatchop} will be used in default mode. The
9739 compilation mode described above is used only if you need exactly
9740 accurate behavior with respect to compilations, and you have files
9741 that contain multiple units and configuration pragmas. In this
9742 circumstance the use of @code{gnatchop} with the compilation mode
9743 switch provides the required behavior, and is for example the mode
9744 in which GNAT processes the ACVC tests.
9746 @node Command Line for gnatchop
9747 @section Command Line for @code{gnatchop}
9750 The @code{gnatchop} command has the form:
9753 $ gnatchop switches @var{file name} [@var{file name} @var{file name} ...]
9758 The only required argument is the file name of the file to be chopped.
9759 There are no restrictions on the form of this file name. The file itself
9760 contains one or more Ada units, in normal GNAT format, concatenated
9761 together. As shown, more than one file may be presented to be chopped.
9763 When run in default mode, @code{gnatchop} generates one output file in
9764 the current directory for each unit in each of the files.
9766 @var{directory}, if specified, gives the name of the directory to which
9767 the output files will be written. If it is not specified, all files are
9768 written to the current directory.
9770 For example, given a
9771 file called @file{hellofiles} containing
9773 @smallexample @c ada
9778 with Text_IO; use Text_IO;
9791 $ gnatchop ^hellofiles^HELLOFILES.^
9795 generates two files in the current directory, one called
9796 @file{hello.ads} containing the single line that is the procedure spec,
9797 and the other called @file{hello.adb} containing the remaining text. The
9798 original file is not affected. The generated files can be compiled in
9802 When gnatchop is invoked on a file that is empty or that contains only empty
9803 lines and/or comments, gnatchop will not fail, but will not produce any
9806 For example, given a
9807 file called @file{toto.txt} containing
9809 @smallexample @c ada
9821 $ gnatchop ^toto.txt^TOT.TXT^
9825 will not produce any new file and will result in the following warnings:
9828 toto.txt:1:01: warning: empty file, contains no compilation units
9829 no compilation units found
9830 no source files written
9833 @node Switches for gnatchop
9834 @section Switches for @code{gnatchop}
9837 @command{gnatchop} recognizes the following switches:
9842 @item ^-c^/COMPILATION^
9843 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
9844 Causes @code{gnatchop} to operate in compilation mode, in which
9845 configuration pragmas are handled according to strict RM rules. See
9846 previous section for a full description of this mode.
9850 This passes the given @option{-gnatxxx} switch to @code{gnat} which is
9851 used to parse the given file. Not all @code{xxx} options make sense,
9852 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
9853 process a source file that uses Latin-2 coding for identifiers.
9857 Causes @code{gnatchop} to generate a brief help summary to the standard
9858 output file showing usage information.
9860 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
9861 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
9862 Limit generated file names to the specified number @code{mm}
9864 This is useful if the
9865 resulting set of files is required to be interoperable with systems
9866 which limit the length of file names.
9868 If no value is given, or
9869 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
9870 a default of 39, suitable for OpenVMS Alpha
9874 No space is allowed between the @option{-k} and the numeric value. The numeric
9875 value may be omitted in which case a default of @option{-k8},
9877 with DOS-like file systems, is used. If no @option{-k} switch
9879 there is no limit on the length of file names.
9882 @item ^-p^/PRESERVE^
9883 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
9884 Causes the file ^modification^creation^ time stamp of the input file to be
9885 preserved and used for the time stamp of the output file(s). This may be
9886 useful for preserving coherency of time stamps in an environment where
9887 @code{gnatchop} is used as part of a standard build process.
9890 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
9891 Causes output of informational messages indicating the set of generated
9892 files to be suppressed. Warnings and error messages are unaffected.
9894 @item ^-r^/REFERENCE^
9895 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
9896 @findex Source_Reference
9897 Generate @code{Source_Reference} pragmas. Use this switch if the output
9898 files are regarded as temporary and development is to be done in terms
9899 of the original unchopped file. This switch causes
9900 @code{Source_Reference} pragmas to be inserted into each of the
9901 generated files to refers back to the original file name and line number.
9902 The result is that all error messages refer back to the original
9904 In addition, the debugging information placed into the object file (when
9905 the @option{^-g^/DEBUG^} switch of @code{gcc} or @code{gnatmake} is specified)
9906 also refers back to this original file so that tools like profilers and
9907 debuggers will give information in terms of the original unchopped file.
9909 If the original file to be chopped itself contains
9910 a @code{Source_Reference}
9911 pragma referencing a third file, then gnatchop respects
9912 this pragma, and the generated @code{Source_Reference} pragmas
9913 in the chopped file refer to the original file, with appropriate
9914 line numbers. This is particularly useful when @code{gnatchop}
9915 is used in conjunction with @code{gnatprep} to compile files that
9916 contain preprocessing statements and multiple units.
9919 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
9920 Causes @code{gnatchop} to operate in verbose mode. The version
9921 number and copyright notice are output, as well as exact copies of
9922 the gnat1 commands spawned to obtain the chop control information.
9924 @item ^-w^/OVERWRITE^
9925 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
9926 Overwrite existing file names. Normally @code{gnatchop} regards it as a
9927 fatal error if there is already a file with the same name as a
9928 file it would otherwise output, in other words if the files to be
9929 chopped contain duplicated units. This switch bypasses this
9930 check, and causes all but the last instance of such duplicated
9931 units to be skipped.
9935 @cindex @option{--GCC=} (@code{gnatchop})
9936 Specify the path of the GNAT parser to be used. When this switch is used,
9937 no attempt is made to add the prefix to the GNAT parser executable.
9941 @node Examples of gnatchop Usage
9942 @section Examples of @code{gnatchop} Usage
9946 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
9949 @item gnatchop -w hello_s.ada prerelease/files
9952 Chops the source file @file{hello_s.ada}. The output files will be
9953 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
9955 files with matching names in that directory (no files in the current
9956 directory are modified).
9958 @item gnatchop ^archive^ARCHIVE.^
9959 Chops the source file @file{^archive^ARCHIVE.^}
9960 into the current directory. One
9961 useful application of @code{gnatchop} is in sending sets of sources
9962 around, for example in email messages. The required sources are simply
9963 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
9965 @code{gnatchop} is used at the other end to reconstitute the original
9968 @item gnatchop file1 file2 file3 direc
9969 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
9970 the resulting files in the directory @file{direc}. Note that if any units
9971 occur more than once anywhere within this set of files, an error message
9972 is generated, and no files are written. To override this check, use the
9973 @option{^-w^/OVERWRITE^} switch,
9974 in which case the last occurrence in the last file will
9975 be the one that is output, and earlier duplicate occurrences for a given
9976 unit will be skipped.
9979 @node Configuration Pragmas
9980 @chapter Configuration Pragmas
9981 @cindex Configuration pragmas
9982 @cindex Pragmas, configuration
9985 In Ada 95, configuration pragmas include those pragmas described as
9986 such in the Ada 95 Reference Manual, as well as
9987 implementation-dependent pragmas that are configuration pragmas. See the
9988 individual descriptions of pragmas in the GNAT Reference Manual for
9989 details on these additional GNAT-specific configuration pragmas. Most
9990 notably, the pragma @code{Source_File_Name}, which allows
9991 specifying non-default names for source files, is a configuration
9992 pragma. The following is a complete list of configuration pragmas
9993 recognized by @code{GNAT}:
10005 External_Name_Casing
10006 Float_Representation
10015 Propagate_Exceptions
10018 Restricted_Run_Time
10020 Restrictions_Warnings
10025 Task_Dispatching_Policy
10034 * Handling of Configuration Pragmas::
10035 * The Configuration Pragmas Files::
10038 @node Handling of Configuration Pragmas
10039 @section Handling of Configuration Pragmas
10041 Configuration pragmas may either appear at the start of a compilation
10042 unit, in which case they apply only to that unit, or they may apply to
10043 all compilations performed in a given compilation environment.
10045 GNAT also provides the @code{gnatchop} utility to provide an automatic
10046 way to handle configuration pragmas following the semantics for
10047 compilations (that is, files with multiple units), described in the RM.
10048 See section @pxref{Operating gnatchop in Compilation Mode} for details.
10049 However, for most purposes, it will be more convenient to edit the
10050 @file{gnat.adc} file that contains configuration pragmas directly,
10051 as described in the following section.
10053 @node The Configuration Pragmas Files
10054 @section The Configuration Pragmas Files
10055 @cindex @file{gnat.adc}
10058 In GNAT a compilation environment is defined by the current
10059 directory at the time that a compile command is given. This current
10060 directory is searched for a file whose name is @file{gnat.adc}. If
10061 this file is present, it is expected to contain one or more
10062 configuration pragmas that will be applied to the current compilation.
10063 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
10066 Configuration pragmas may be entered into the @file{gnat.adc} file
10067 either by running @code{gnatchop} on a source file that consists only of
10068 configuration pragmas, or more conveniently by
10069 direct editing of the @file{gnat.adc} file, which is a standard format
10072 In addition to @file{gnat.adc}, one additional file containing configuration
10073 pragmas may be applied to the current compilation using the switch
10074 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
10075 contains only configuration pragmas. These configuration pragmas are
10076 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
10077 is present and switch @option{-gnatA} is not used).
10079 It is allowed to specify several switches @option{-gnatec}, however only
10080 the last one on the command line will be taken into account.
10082 If you are using project file, a separate mechanism is provided using
10083 project attributes, see @ref{Specifying Configuration Pragmas} for more
10087 Of special interest to GNAT OpenVMS Alpha is the following
10088 configuration pragma:
10090 @smallexample @c ada
10092 pragma Extend_System (Aux_DEC);
10097 In the presence of this pragma, GNAT adds to the definition of the
10098 predefined package SYSTEM all the additional types and subprograms that are
10099 defined in DEC Ada. See @pxref{Compatibility with DEC Ada} for details.
10102 @node Handling Arbitrary File Naming Conventions Using gnatname
10103 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
10104 @cindex Arbitrary File Naming Conventions
10107 * Arbitrary File Naming Conventions::
10108 * Running gnatname::
10109 * Switches for gnatname::
10110 * Examples of gnatname Usage::
10113 @node Arbitrary File Naming Conventions
10114 @section Arbitrary File Naming Conventions
10117 The GNAT compiler must be able to know the source file name of a compilation
10118 unit. When using the standard GNAT default file naming conventions
10119 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
10120 does not need additional information.
10123 When the source file names do not follow the standard GNAT default file naming
10124 conventions, the GNAT compiler must be given additional information through
10125 a configuration pragmas file (see @ref{Configuration Pragmas})
10127 When the non standard file naming conventions are well-defined,
10128 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
10129 (see @ref{Alternative File Naming Schemes}) may be sufficient. However,
10130 if the file naming conventions are irregular or arbitrary, a number
10131 of pragma @code{Source_File_Name} for individual compilation units
10133 To help maintain the correspondence between compilation unit names and
10134 source file names within the compiler,
10135 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
10138 @node Running gnatname
10139 @section Running @code{gnatname}
10142 The usual form of the @code{gnatname} command is
10145 $ gnatname [@var{switches}] @var{naming_pattern} [@var{naming_patterns}]
10149 All of the arguments are optional. If invoked without any argument,
10150 @code{gnatname} will display its usage.
10153 When used with at least one naming pattern, @code{gnatname} will attempt to
10154 find all the compilation units in files that follow at least one of the
10155 naming patterns. To find these compilation units,
10156 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
10160 One or several Naming Patterns may be given as arguments to @code{gnatname}.
10161 Each Naming Pattern is enclosed between double quotes.
10162 A Naming Pattern is a regular expression similar to the wildcard patterns
10163 used in file names by the Unix shells or the DOS prompt.
10166 Examples of Naming Patterns are
10175 For a more complete description of the syntax of Naming Patterns,
10176 see the second kind of regular expressions described in @file{g-regexp.ads}
10177 (the ``Glob'' regular expressions).
10180 When invoked with no switches, @code{gnatname} will create a configuration
10181 pragmas file @file{gnat.adc} in the current working directory, with pragmas
10182 @code{Source_File_Name} for each file that contains a valid Ada unit.
10184 @node Switches for gnatname
10185 @section Switches for @code{gnatname}
10188 Switches for @code{gnatname} must precede any specified Naming Pattern.
10191 You may specify any of the following switches to @code{gnatname}:
10196 @item ^-c^/CONFIG_FILE=^@file{file}
10197 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
10198 Create a configuration pragmas file @file{file} (instead of the default
10201 There may be zero, one or more space between @option{-c} and
10204 @file{file} may include directory information. @file{file} must be
10205 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
10206 When a switch @option{^-c^/CONFIG_FILE^} is
10207 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
10209 @item ^-d^/SOURCE_DIRS=^@file{dir}
10210 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
10211 Look for source files in directory @file{dir}. There may be zero, one or more
10212 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
10213 When a switch @option{^-d^/SOURCE_DIRS^}
10214 is specified, the current working directory will not be searched for source
10215 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
10216 or @option{^-D^/DIR_FILES^} switch.
10217 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
10218 If @file{dir} is a relative path, it is relative to the directory of
10219 the configuration pragmas file specified with switch
10220 @option{^-c^/CONFIG_FILE^},
10221 or to the directory of the project file specified with switch
10222 @option{^-P^/PROJECT_FILE^} or,
10223 if neither switch @option{^-c^/CONFIG_FILE^}
10224 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
10225 current working directory. The directory
10226 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
10228 @item ^-D^/DIRS_FILE=^@file{file}
10229 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
10230 Look for source files in all directories listed in text file @file{file}.
10231 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
10233 @file{file} must be an existing, readable text file.
10234 Each non empty line in @file{file} must be a directory.
10235 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
10236 switches @option{^-d^/SOURCE_DIRS^} as there are non empty lines in
10239 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
10240 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
10241 Foreign patterns. Using this switch, it is possible to add sources of languages
10242 other than Ada to the list of sources of a project file.
10243 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
10246 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
10249 will look for Ada units in all files with the @file{.ada} extension,
10250 and will add to the list of file for project @file{prj.gpr} the C files
10251 with extension ".^c^C^".
10254 @cindex @option{^-h^/HELP^} (@code{gnatname})
10255 Output usage (help) information. The output is written to @file{stdout}.
10257 @item ^-P^/PROJECT_FILE=^@file{proj}
10258 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
10259 Create or update project file @file{proj}. There may be zero, one or more space
10260 between @option{-P} and @file{proj}. @file{proj} may include directory
10261 information. @file{proj} must be writable.
10262 There may be only one switch @option{^-P^/PROJECT_FILE^}.
10263 When a switch @option{^-P^/PROJECT_FILE^} is specified,
10264 no switch @option{^-c^/CONFIG_FILE^} may be specified.
10266 @item ^-v^/VERBOSE^
10267 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
10268 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
10269 This includes name of the file written, the name of the directories to search
10270 and, for each file in those directories whose name matches at least one of
10271 the Naming Patterns, an indication of whether the file contains a unit,
10272 and if so the name of the unit.
10274 @item ^-v -v^/VERBOSE /VERBOSE^
10275 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
10276 Very Verbose mode. In addition to the output produced in verbose mode,
10277 for each file in the searched directories whose name matches none of
10278 the Naming Patterns, an indication is given that there is no match.
10280 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
10281 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
10282 Excluded patterns. Using this switch, it is possible to exclude some files
10283 that would match the name patterns. For example,
10285 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
10288 will look for Ada units in all files with the @file{.ada} extension,
10289 except those whose names end with @file{_nt.ada}.
10293 @node Examples of gnatname Usage
10294 @section Examples of @code{gnatname} Usage
10298 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
10304 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
10309 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
10310 and be writable. In addition, the directory
10311 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
10312 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
10315 Note the optional spaces after @option{-c} and @option{-d}.
10320 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
10321 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
10324 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
10325 /EXCLUDED_PATTERN=*_nt_body.ada
10326 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
10327 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
10331 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
10332 even in conjunction with one or several switches
10333 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
10334 are used in this example.
10337 @c *****************************************
10338 @c * G N A T P r o j e c t M a n a g e r *
10339 @c *****************************************
10340 @node GNAT Project Manager
10341 @chapter GNAT Project Manager
10345 * Examples of Project Files::
10346 * Project File Syntax::
10347 * Objects and Sources in Project Files::
10348 * Importing Projects::
10349 * Project Extension::
10350 * External References in Project Files::
10351 * Packages in Project Files::
10352 * Variables from Imported Projects::
10354 * Library Projects::
10355 * Using Third-Party Libraries through Projects::
10356 * Stand-alone Library Projects::
10357 * Switches Related to Project Files::
10358 * Tools Supporting Project Files::
10359 * An Extended Example::
10360 * Project File Complete Syntax::
10363 @c ****************
10364 @c * Introduction *
10365 @c ****************
10368 @section Introduction
10371 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
10372 you to manage complex builds involving a number of source files, directories,
10373 and compilation options for different system configurations. In particular,
10374 project files allow you to specify:
10377 The directory or set of directories containing the source files, and/or the
10378 names of the specific source files themselves
10380 The directory in which the compiler's output
10381 (@file{ALI} files, object files, tree files) is to be placed
10383 The directory in which the executable programs is to be placed
10385 ^Switch^Switch^ settings for any of the project-enabled tools
10386 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
10387 @code{gnatfind}); you can apply these settings either globally or to individual
10390 The source files containing the main subprogram(s) to be built
10392 The source programming language(s) (currently Ada and/or C)
10394 Source file naming conventions; you can specify these either globally or for
10395 individual compilation units
10402 @node Project Files
10403 @subsection Project Files
10406 Project files are written in a syntax close to that of Ada, using familiar
10407 notions such as packages, context clauses, declarations, default values,
10408 assignments, and inheritance. Finally, project files can be built
10409 hierarchically from other project files, simplifying complex system
10410 integration and project reuse.
10412 A @dfn{project} is a specific set of values for various compilation properties.
10413 The settings for a given project are described by means of
10414 a @dfn{project file}, which is a text file written in an Ada-like syntax.
10415 Property values in project files are either strings or lists of strings.
10416 Properties that are not explicitly set receive default values. A project
10417 file may interrogate the values of @dfn{external variables} (user-defined
10418 command-line switches or environment variables), and it may specify property
10419 settings conditionally, based on the value of such variables.
10421 In simple cases, a project's source files depend only on other source files
10422 in the same project, or on the predefined libraries. (@emph{Dependence} is
10424 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
10425 the Project Manager also allows more sophisticated arrangements,
10426 where the source files in one project depend on source files in other
10430 One project can @emph{import} other projects containing needed source files.
10432 You can organize GNAT projects in a hierarchy: a @emph{child} project
10433 can extend a @emph{parent} project, inheriting the parent's source files and
10434 optionally overriding any of them with alternative versions
10438 More generally, the Project Manager lets you structure large development
10439 efforts into hierarchical subsystems, where build decisions are delegated
10440 to the subsystem level, and thus different compilation environments
10441 (^switch^switch^ settings) used for different subsystems.
10443 The Project Manager is invoked through the
10444 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
10445 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
10447 There may be zero, one or more spaces between @option{-P} and
10448 @option{@emph{projectfile}}.
10450 If you want to define (on the command line) an external variable that is
10451 queried by the project file, you must use the
10452 @option{^-X^/EXTERNAT_REFERENCE=^@emph{vbl}=@emph{value}} switch.
10453 The Project Manager parses and interprets the project file, and drives the
10454 invoked tool based on the project settings.
10456 The Project Manager supports a wide range of development strategies,
10457 for systems of all sizes. Here are some typical practices that are
10461 Using a common set of source files, but generating object files in different
10462 directories via different ^switch^switch^ settings
10464 Using a mostly-shared set of source files, but with different versions of
10469 The destination of an executable can be controlled inside a project file
10470 using the @option{^-o^-o^}
10472 In the absence of such a ^switch^switch^ either inside
10473 the project file or on the command line, any executable files generated by
10474 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
10475 in the project file. If no @code{Exec_Dir} is specified, they will be placed
10476 in the object directory of the project.
10478 You can use project files to achieve some of the effects of a source
10479 versioning system (for example, defining separate projects for
10480 the different sets of sources that comprise different releases) but the
10481 Project Manager is independent of any source configuration management tools
10482 that might be used by the developers.
10484 The next section introduces the main features of GNAT's project facility
10485 through a sequence of examples; subsequent sections will present the syntax
10486 and semantics in more detail. A more formal description of the project
10487 facility appears in the GNAT Reference Manual.
10489 @c *****************************
10490 @c * Examples of Project Files *
10491 @c *****************************
10493 @node Examples of Project Files
10494 @section Examples of Project Files
10496 This section illustrates some of the typical uses of project files and
10497 explains their basic structure and behavior.
10500 * Common Sources with Different ^Switches^Switches^ and Directories::
10501 * Using External Variables::
10502 * Importing Other Projects::
10503 * Extending a Project::
10506 @node Common Sources with Different ^Switches^Switches^ and Directories
10507 @subsection Common Sources with Different ^Switches^Switches^ and Directories
10511 * Specifying the Object Directory::
10512 * Specifying the Exec Directory::
10513 * Project File Packages::
10514 * Specifying ^Switch^Switch^ Settings::
10515 * Main Subprograms::
10516 * Executable File Names::
10517 * Source File Naming Conventions::
10518 * Source Language(s)::
10522 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
10523 @file{proc.adb} are in the @file{/common} directory. The file
10524 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
10525 package @code{Pack}. We want to compile these source files under two sets
10526 of ^switches^switches^:
10529 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
10530 and the @option{^-gnata^-gnata^},
10531 @option{^-gnato^-gnato^},
10532 and @option{^-gnatE^-gnatE^} switches to the
10533 compiler; the compiler's output is to appear in @file{/common/debug}
10535 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
10536 to the compiler; the compiler's output is to appear in @file{/common/release}
10540 The GNAT project files shown below, respectively @file{debug.gpr} and
10541 @file{release.gpr} in the @file{/common} directory, achieve these effects.
10554 ^/common/debug^[COMMON.DEBUG]^
10559 ^/common/release^[COMMON.RELEASE]^
10564 Here are the corresponding project files:
10566 @smallexample @c projectfile
10569 for Object_Dir use "debug";
10570 for Main use ("proc");
10573 for ^Default_Switches^Default_Switches^ ("Ada")
10575 for Executable ("proc.adb") use "proc1";
10580 package Compiler is
10581 for ^Default_Switches^Default_Switches^ ("Ada")
10582 use ("-fstack-check",
10585 "^-gnatE^-gnatE^");
10591 @smallexample @c projectfile
10594 for Object_Dir use "release";
10595 for Exec_Dir use ".";
10596 for Main use ("proc");
10598 package Compiler is
10599 for ^Default_Switches^Default_Switches^ ("Ada")
10607 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
10608 insensitive), and analogously the project defined by @file{release.gpr} is
10609 @code{"Release"}. For consistency the file should have the same name as the
10610 project, and the project file's extension should be @code{"gpr"}. These
10611 conventions are not required, but a warning is issued if they are not followed.
10613 If the current directory is @file{^/temp^[TEMP]^}, then the command
10615 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
10619 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
10620 as well as the @code{^proc1^PROC1.EXE^} executable,
10621 using the ^switch^switch^ settings defined in the project file.
10623 Likewise, the command
10625 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
10629 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
10630 and the @code{^proc^PROC.EXE^}
10631 executable in @file{^/common^[COMMON]^},
10632 using the ^switch^switch^ settings from the project file.
10635 @unnumberedsubsubsec Source Files
10638 If a project file does not explicitly specify a set of source directories or
10639 a set of source files, then by default the project's source files are the
10640 Ada source files in the project file directory. Thus @file{pack.ads},
10641 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
10643 @node Specifying the Object Directory
10644 @unnumberedsubsubsec Specifying the Object Directory
10647 Several project properties are modeled by Ada-style @emph{attributes};
10648 a property is defined by supplying the equivalent of an Ada attribute
10649 definition clause in the project file.
10650 A project's object directory is another such a property; the corresponding
10651 attribute is @code{Object_Dir}, and its value is also a string expression,
10652 specified either as absolute or relative. In the later case,
10653 it is relative to the project file directory. Thus the compiler's
10654 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
10655 (for the @code{Debug} project)
10656 and to @file{^/common/release^[COMMON.RELEASE]^}
10657 (for the @code{Release} project).
10658 If @code{Object_Dir} is not specified, then the default is the project file
10661 @node Specifying the Exec Directory
10662 @unnumberedsubsubsec Specifying the Exec Directory
10665 A project's exec directory is another property; the corresponding
10666 attribute is @code{Exec_Dir}, and its value is also a string expression,
10667 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
10668 then the default is the object directory (which may also be the project file
10669 directory if attribute @code{Object_Dir} is not specified). Thus the executable
10670 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
10671 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
10672 and in @file{^/common^[COMMON]^} for the @code{Release} project.
10674 @node Project File Packages
10675 @unnumberedsubsubsec Project File Packages
10678 A GNAT tool that is integrated with the Project Manager is modeled by a
10679 corresponding package in the project file. In the example above,
10680 The @code{Debug} project defines the packages @code{Builder}
10681 (for @command{gnatmake}) and @code{Compiler};
10682 the @code{Release} project defines only the @code{Compiler} package.
10684 The Ada-like package syntax is not to be taken literally. Although packages in
10685 project files bear a surface resemblance to packages in Ada source code, the
10686 notation is simply a way to convey a grouping of properties for a named
10687 entity. Indeed, the package names permitted in project files are restricted
10688 to a predefined set, corresponding to the project-aware tools, and the contents
10689 of packages are limited to a small set of constructs.
10690 The packages in the example above contain attribute definitions.
10692 @node Specifying ^Switch^Switch^ Settings
10693 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
10696 ^Switch^Switch^ settings for a project-aware tool can be specified through
10697 attributes in the package that corresponds to the tool.
10698 The example above illustrates one of the relevant attributes,
10699 @code{^Default_Switches^Default_Switches^}, which is defined in packages
10700 in both project files.
10701 Unlike simple attributes like @code{Source_Dirs},
10702 @code{^Default_Switches^Default_Switches^} is
10703 known as an @emph{associative array}. When you define this attribute, you must
10704 supply an ``index'' (a literal string), and the effect of the attribute
10705 definition is to set the value of the array at the specified index.
10706 For the @code{^Default_Switches^Default_Switches^} attribute,
10707 the index is a programming language (in our case, Ada),
10708 and the value specified (after @code{use}) must be a list
10709 of string expressions.
10711 The attributes permitted in project files are restricted to a predefined set.
10712 Some may appear at project level, others in packages.
10713 For any attribute that is an associative array, the index must always be a
10714 literal string, but the restrictions on this string (e.g., a file name or a
10715 language name) depend on the individual attribute.
10716 Also depending on the attribute, its specified value will need to be either a
10717 string or a string list.
10719 In the @code{Debug} project, we set the switches for two tools,
10720 @command{gnatmake} and the compiler, and thus we include the two corresponding
10721 packages; each package defines the @code{^Default_Switches^Default_Switches^}
10722 attribute with index @code{"Ada"}.
10723 Note that the package corresponding to
10724 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
10725 similar, but only includes the @code{Compiler} package.
10727 In project @code{Debug} above, the ^switches^switches^ starting with
10728 @option{-gnat} that are specified in package @code{Compiler}
10729 could have been placed in package @code{Builder}, since @command{gnatmake}
10730 transmits all such ^switches^switches^ to the compiler.
10732 @node Main Subprograms
10733 @unnumberedsubsubsec Main Subprograms
10736 One of the specifiable properties of a project is a list of files that contain
10737 main subprograms. This property is captured in the @code{Main} attribute,
10738 whose value is a list of strings. If a project defines the @code{Main}
10739 attribute, it is not necessary to identify the main subprogram(s) when
10740 invoking @command{gnatmake} (see @ref{gnatmake and Project Files}).
10742 @node Executable File Names
10743 @unnumberedsubsubsec Executable File Names
10746 By default, the executable file name corresponding to a main source is
10747 deducted from the main source file name. Through the attributes
10748 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
10749 it is possible to change this default.
10750 In project @code{Debug} above, the executable file name
10751 for main source @file{^proc.adb^PROC.ADB^} is
10752 @file{^proc1^PROC1.EXE^}.
10753 Attribute @code{Executable_Suffix}, when specified, may change the suffix
10754 of the the executable files, when no attribute @code{Executable} applies:
10755 its value replace the platform-specific executable suffix.
10756 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
10757 specify a non default executable file name when several mains are built at once
10758 in a single @command{gnatmake} command.
10760 @node Source File Naming Conventions
10761 @unnumberedsubsubsec Source File Naming Conventions
10764 Since the project files above do not specify any source file naming
10765 conventions, the GNAT defaults are used. The mechanism for defining source
10766 file naming conventions -- a package named @code{Naming} --
10767 is described below (@pxref{Naming Schemes}).
10769 @node Source Language(s)
10770 @unnumberedsubsubsec Source Language(s)
10773 Since the project files do not specify a @code{Languages} attribute, by
10774 default the GNAT tools assume that the language of the project file is Ada.
10775 More generally, a project can comprise source files
10776 in Ada, C, and/or other languages.
10778 @node Using External Variables
10779 @subsection Using External Variables
10782 Instead of supplying different project files for debug and release, we can
10783 define a single project file that queries an external variable (set either
10784 on the command line or via an ^environment variable^logical name^) in order to
10785 conditionally define the appropriate settings. Again, assume that the
10786 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
10787 located in directory @file{^/common^[COMMON]^}. The following project file,
10788 @file{build.gpr}, queries the external variable named @code{STYLE} and
10789 defines an object directory and ^switch^switch^ settings based on whether
10790 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
10791 the default is @code{"deb"}.
10793 @smallexample @c projectfile
10796 for Main use ("proc");
10798 type Style_Type is ("deb", "rel");
10799 Style : Style_Type := external ("STYLE", "deb");
10803 for Object_Dir use "debug";
10806 for Object_Dir use "release";
10807 for Exec_Dir use ".";
10816 for ^Default_Switches^Default_Switches^ ("Ada")
10818 for Executable ("proc") use "proc1";
10827 package Compiler is
10831 for ^Default_Switches^Default_Switches^ ("Ada")
10832 use ("^-gnata^-gnata^",
10834 "^-gnatE^-gnatE^");
10837 for ^Default_Switches^Default_Switches^ ("Ada")
10848 @code{Style_Type} is an example of a @emph{string type}, which is the project
10849 file analog of an Ada enumeration type but whose components are string literals
10850 rather than identifiers. @code{Style} is declared as a variable of this type.
10852 The form @code{external("STYLE", "deb")} is known as an
10853 @emph{external reference}; its first argument is the name of an
10854 @emph{external variable}, and the second argument is a default value to be
10855 used if the external variable doesn't exist. You can define an external
10856 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
10857 or you can use ^an environment variable^a logical name^
10858 as an external variable.
10860 Each @code{case} construct is expanded by the Project Manager based on the
10861 value of @code{Style}. Thus the command
10864 gnatmake -P/common/build.gpr -XSTYLE=deb
10870 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
10875 is equivalent to the @command{gnatmake} invocation using the project file
10876 @file{debug.gpr} in the earlier example. So is the command
10878 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
10882 since @code{"deb"} is the default for @code{STYLE}.
10888 gnatmake -P/common/build.gpr -XSTYLE=rel
10894 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
10899 is equivalent to the @command{gnatmake} invocation using the project file
10900 @file{release.gpr} in the earlier example.
10902 @node Importing Other Projects
10903 @subsection Importing Other Projects
10906 A compilation unit in a source file in one project may depend on compilation
10907 units in source files in other projects. To compile this unit under
10908 control of a project file, the
10909 dependent project must @emph{import} the projects containing the needed source
10911 This effect is obtained using syntax similar to an Ada @code{with} clause,
10912 but where @code{with}ed entities are strings that denote project files.
10914 As an example, suppose that the two projects @code{GUI_Proj} and
10915 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
10916 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
10917 and @file{^/comm^[COMM]^}, respectively.
10918 Suppose that the source files for @code{GUI_Proj} are
10919 @file{gui.ads} and @file{gui.adb}, and that the source files for
10920 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
10921 files is located in its respective project file directory. Schematically:
10940 We want to develop an application in directory @file{^/app^[APP]^} that
10941 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
10942 the corresponding project files (e.g. the ^switch^switch^ settings
10943 and object directory).
10944 Skeletal code for a main procedure might be something like the following:
10946 @smallexample @c ada
10949 procedure App_Main is
10958 Here is a project file, @file{app_proj.gpr}, that achieves the desired
10961 @smallexample @c projectfile
10963 with "/gui/gui_proj", "/comm/comm_proj";
10964 project App_Proj is
10965 for Main use ("app_main");
10971 Building an executable is achieved through the command:
10973 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
10976 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
10977 in the directory where @file{app_proj.gpr} resides.
10979 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
10980 (as illustrated above) the @code{with} clause can omit the extension.
10982 Our example specified an absolute path for each imported project file.
10983 Alternatively, the directory name of an imported object can be omitted
10987 The imported project file is in the same directory as the importing project
10990 You have defined ^an environment variable^a logical name^
10991 that includes the directory containing
10992 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
10993 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
10994 directory names separated by colons (semicolons on Windows).
10998 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
10999 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
11002 @smallexample @c projectfile
11004 with "gui_proj", "comm_proj";
11005 project App_Proj is
11006 for Main use ("app_main");
11012 Importing other projects can create ambiguities.
11013 For example, the same unit might be present in different imported projects, or
11014 it might be present in both the importing project and in an imported project.
11015 Both of these conditions are errors. Note that in the current version of
11016 the Project Manager, it is illegal to have an ambiguous unit even if the
11017 unit is never referenced by the importing project. This restriction may be
11018 relaxed in a future release.
11020 @node Extending a Project
11021 @subsection Extending a Project
11024 In large software systems it is common to have multiple
11025 implementations of a common interface; in Ada terms, multiple versions of a
11026 package body for the same specification. For example, one implementation
11027 might be safe for use in tasking programs, while another might only be used
11028 in sequential applications. This can be modeled in GNAT using the concept
11029 of @emph{project extension}. If one project (the ``child'') @emph{extends}
11030 another project (the ``parent'') then by default all source files of the
11031 parent project are inherited by the child, but the child project can
11032 override any of the parent's source files with new versions, and can also
11033 add new files. This facility is the project analog of a type extension in
11034 Object-Oriented Programming. Project hierarchies are permitted (a child
11035 project may be the parent of yet another project), and a project that
11036 inherits one project can also import other projects.
11038 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
11039 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
11040 @file{pack.adb}, and @file{proc.adb}:
11053 Note that the project file can simply be empty (that is, no attribute or
11054 package is defined):
11056 @smallexample @c projectfile
11058 project Seq_Proj is
11064 implying that its source files are all the Ada source files in the project
11067 Suppose we want to supply an alternate version of @file{pack.adb}, in
11068 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
11069 @file{pack.ads} and @file{proc.adb}. We can define a project
11070 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
11074 ^/tasking^[TASKING]^
11080 project Tasking_Proj extends "/seq/seq_proj" is
11086 The version of @file{pack.adb} used in a build depends on which project file
11089 Note that we could have obtained the desired behavior using project import
11090 rather than project inheritance; a @code{base} project would contain the
11091 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
11092 import @code{base} and add @file{pack.adb}, and likewise a tasking project
11093 would import @code{base} and add a different version of @file{pack.adb}. The
11094 choice depends on whether other sources in the original project need to be
11095 overridden. If they do, then project extension is necessary, otherwise,
11096 importing is sufficient.
11099 In a project file that extends another project file, it is possible to
11100 indicate that an inherited source is not part of the sources of the extending
11101 project. This is necessary sometimes when a package spec has been overloaded
11102 and no longer requires a body: in this case, it is necessary to indicate that
11103 the inherited body is not part of the sources of the project, otherwise there
11104 will be a compilation error when compiling the spec.
11106 For that purpose, the attribute @code{Locally_Removed_Files} is used.
11107 Its value is a string list: a list of file names.
11109 @smallexample @c @projectfile
11110 project B extends "a" is
11111 for Source_Files use ("pkg.ads");
11112 -- New spec of Pkg does not need a completion
11113 for Locally_Removed_Files use ("pkg.adb");
11117 Attribute @code{Locally_Removed_Files} may also be used to check if a source
11118 is still needed: if it is possible to build using @code{gnatmake} when such
11119 a source is put in attribute @code{Locally_Removed_Files} of a project P, then
11120 it is possible to remove the source completely from a system that includes
11123 @c ***********************
11124 @c * Project File Syntax *
11125 @c ***********************
11127 @node Project File Syntax
11128 @section Project File Syntax
11137 * Associative Array Attributes::
11138 * case Constructions::
11142 This section describes the structure of project files.
11144 A project may be an @emph{independent project}, entirely defined by a single
11145 project file. Any Ada source file in an independent project depends only
11146 on the predefined library and other Ada source files in the same project.
11149 A project may also @dfn{depend on} other projects, in either or both of
11150 the following ways:
11152 @item It may import any number of projects
11153 @item It may extend at most one other project
11157 The dependence relation is a directed acyclic graph (the subgraph reflecting
11158 the ``extends'' relation is a tree).
11160 A project's @dfn{immediate sources} are the source files directly defined by
11161 that project, either implicitly by residing in the project file's directory,
11162 or explicitly through any of the source-related attributes described below.
11163 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
11164 of @var{proj} together with the immediate sources (unless overridden) of any
11165 project on which @var{proj} depends (either directly or indirectly).
11168 @subsection Basic Syntax
11171 As seen in the earlier examples, project files have an Ada-like syntax.
11172 The minimal project file is:
11173 @smallexample @c projectfile
11182 The identifier @code{Empty} is the name of the project.
11183 This project name must be present after the reserved
11184 word @code{end} at the end of the project file, followed by a semi-colon.
11186 Any name in a project file, such as the project name or a variable name,
11187 has the same syntax as an Ada identifier.
11189 The reserved words of project files are the Ada reserved words plus
11190 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
11191 reserved words currently used in project file syntax are:
11219 Comments in project files have the same syntax as in Ada, two consecutives
11220 hyphens through the end of the line.
11223 @subsection Packages
11226 A project file may contain @emph{packages}. The name of a package must be one
11227 of the identifiers from the following list. A package
11228 with a given name may only appear once in a project file. Package names are
11229 case insensitive. The following package names are legal:
11245 @code{Cross_Reference}
11257 In its simplest form, a package may be empty:
11259 @smallexample @c projectfile
11269 A package may contain @emph{attribute declarations},
11270 @emph{variable declarations} and @emph{case constructions}, as will be
11273 When there is ambiguity between a project name and a package name,
11274 the name always designates the project. To avoid possible confusion, it is
11275 always a good idea to avoid naming a project with one of the
11276 names allowed for packages or any name that starts with @code{gnat}.
11279 @subsection Expressions
11282 An @emph{expression} is either a @emph{string expression} or a
11283 @emph{string list expression}.
11285 A @emph{string expression} is either a @emph{simple string expression} or a
11286 @emph{compound string expression}.
11288 A @emph{simple string expression} is one of the following:
11290 @item A literal string; e.g.@code{"comm/my_proj.gpr"}
11291 @item A string-valued variable reference (see @ref{Variables})
11292 @item A string-valued attribute reference (see @ref{Attributes})
11293 @item An external reference (see @ref{External References in Project Files})
11297 A @emph{compound string expression} is a concatenation of string expressions,
11298 using the operator @code{"&"}
11300 Path & "/" & File_Name & ".ads"
11304 A @emph{string list expression} is either a
11305 @emph{simple string list expression} or a
11306 @emph{compound string list expression}.
11308 A @emph{simple string list expression} is one of the following:
11310 @item A parenthesized list of zero or more string expressions,
11311 separated by commas
11313 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
11316 @item A string list-valued variable reference
11317 @item A string list-valued attribute reference
11321 A @emph{compound string list expression} is the concatenation (using
11322 @code{"&"}) of a simple string list expression and an expression. Note that
11323 each term in a compound string list expression, except the first, may be
11324 either a string expression or a string list expression.
11326 @smallexample @c projectfile
11328 File_Name_List := () & File_Name; -- One string in this list
11329 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
11331 Big_List := File_Name_List & Extended_File_Name_List;
11332 -- Concatenation of two string lists: three strings
11333 Illegal_List := "gnat.adc" & Extended_File_Name_List;
11334 -- Illegal: must start with a string list
11339 @subsection String Types
11342 A @emph{string type declaration} introduces a discrete set of string literals.
11343 If a string variable is declared to have this type, its value
11344 is restricted to the given set of literals.
11346 Here is an example of a string type declaration:
11348 @smallexample @c projectfile
11349 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
11353 Variables of a string type are called @emph{typed variables}; all other
11354 variables are called @emph{untyped variables}. Typed variables are
11355 particularly useful in @code{case} constructions, to support conditional
11356 attribute declarations.
11357 (see @ref{case Constructions}).
11359 The string literals in the list are case sensitive and must all be different.
11360 They may include any graphic characters allowed in Ada, including spaces.
11362 A string type may only be declared at the project level, not inside a package.
11364 A string type may be referenced by its name if it has been declared in the same
11365 project file, or by an expanded name whose prefix is the name of the project
11366 in which it is declared.
11369 @subsection Variables
11372 A variable may be declared at the project file level, or within a package.
11373 Here are some examples of variable declarations:
11375 @smallexample @c projectfile
11377 This_OS : OS := external ("OS"); -- a typed variable declaration
11378 That_OS := "GNU/Linux"; -- an untyped variable declaration
11383 The syntax of a @emph{typed variable declaration} is identical to the Ada
11384 syntax for an object declaration. By contrast, the syntax of an untyped
11385 variable declaration is identical to an Ada assignment statement. In fact,
11386 variable declarations in project files have some of the characteristics of
11387 an assignment, in that successive declarations for the same variable are
11388 allowed. Untyped variable declarations do establish the expected kind of the
11389 variable (string or string list), and successive declarations for it must
11390 respect the initial kind.
11393 A string variable declaration (typed or untyped) declares a variable
11394 whose value is a string. This variable may be used as a string expression.
11395 @smallexample @c projectfile
11396 File_Name := "readme.txt";
11397 Saved_File_Name := File_Name & ".saved";
11401 A string list variable declaration declares a variable whose value is a list
11402 of strings. The list may contain any number (zero or more) of strings.
11404 @smallexample @c projectfile
11406 List_With_One_Element := ("^-gnaty^-gnaty^");
11407 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
11408 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
11409 "pack2.ada", "util_.ada", "util.ada");
11413 The same typed variable may not be declared more than once at project level,
11414 and it may not be declared more than once in any package; it is in effect
11417 The same untyped variable may be declared several times. Declarations are
11418 elaborated in the order in which they appear, so the new value replaces
11419 the old one, and any subsequent reference to the variable uses the new value.
11420 However, as noted above, if a variable has been declared as a string, all
11422 declarations must give it a string value. Similarly, if a variable has
11423 been declared as a string list, all subsequent declarations
11424 must give it a string list value.
11426 A @emph{variable reference} may take several forms:
11429 @item The simple variable name, for a variable in the current package (if any)
11430 or in the current project
11431 @item An expanded name, whose prefix is a context name.
11435 A @emph{context} may be one of the following:
11438 @item The name of an existing package in the current project
11439 @item The name of an imported project of the current project
11440 @item The name of an ancestor project (i.e., a project extended by the current
11441 project, either directly or indirectly)
11442 @item An expanded name whose prefix is an imported/parent project name, and
11443 whose selector is a package name in that project.
11447 A variable reference may be used in an expression.
11450 @subsection Attributes
11453 A project (and its packages) may have @emph{attributes} that define
11454 the project's properties. Some attributes have values that are strings;
11455 others have values that are string lists.
11457 There are two categories of attributes: @emph{simple attributes}
11458 and @emph{associative arrays} (see @ref{Associative Array Attributes}).
11460 Legal project attribute names, and attribute names for each legal package are
11461 listed below. Attributes names are case-insensitive.
11463 The following attributes are defined on projects (all are simple attributes):
11465 @multitable @columnfractions .4 .3
11466 @item @emph{Attribute Name}
11468 @item @code{Source_Files}
11470 @item @code{Source_Dirs}
11472 @item @code{Source_List_File}
11474 @item @code{Object_Dir}
11476 @item @code{Exec_Dir}
11478 @item @code{Locally_Removed_Files}
11482 @item @code{Languages}
11484 @item @code{Main_Language}
11486 @item @code{Library_Dir}
11488 @item @code{Library_Name}
11490 @item @code{Library_Kind}
11492 @item @code{Library_Version}
11494 @item @code{Library_Interface}
11496 @item @code{Library_Auto_Init}
11498 @item @code{Library_Options}
11500 @item @code{Library_GCC}
11505 The following attributes are defined for package @code{Naming}
11506 (see @ref{Naming Schemes}):
11508 @multitable @columnfractions .4 .2 .2 .2
11509 @item Attribute Name @tab Category @tab Index @tab Value
11510 @item @code{Spec_Suffix}
11511 @tab associative array
11514 @item @code{Body_Suffix}
11515 @tab associative array
11518 @item @code{Separate_Suffix}
11519 @tab simple attribute
11522 @item @code{Casing}
11523 @tab simple attribute
11526 @item @code{Dot_Replacement}
11527 @tab simple attribute
11531 @tab associative array
11535 @tab associative array
11538 @item @code{Specification_Exceptions}
11539 @tab associative array
11542 @item @code{Implementation_Exceptions}
11543 @tab associative array
11549 The following attributes are defined for packages @code{Builder},
11550 @code{Compiler}, @code{Binder},
11551 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
11552 (see @ref{^Switches^Switches^ and Project Files}).
11554 @multitable @columnfractions .4 .2 .2 .2
11555 @item Attribute Name @tab Category @tab Index @tab Value
11556 @item @code{^Default_Switches^Default_Switches^}
11557 @tab associative array
11560 @item @code{^Switches^Switches^}
11561 @tab associative array
11567 In addition, package @code{Compiler} has a single string attribute
11568 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
11569 string attribute @code{Global_Configuration_Pragmas}.
11572 Each simple attribute has a default value: the empty string (for string-valued
11573 attributes) and the empty list (for string list-valued attributes).
11575 An attribute declaration defines a new value for an attribute.
11577 Examples of simple attribute declarations:
11579 @smallexample @c projectfile
11580 for Object_Dir use "objects";
11581 for Source_Dirs use ("units", "test/drivers");
11585 The syntax of a @dfn{simple attribute declaration} is similar to that of an
11586 attribute definition clause in Ada.
11588 Attributes references may be appear in expressions.
11589 The general form for such a reference is @code{<entity>'<attribute>}:
11590 Associative array attributes are functions. Associative
11591 array attribute references must have an argument that is a string literal.
11595 @smallexample @c projectfile
11597 Naming'Dot_Replacement
11598 Imported_Project'Source_Dirs
11599 Imported_Project.Naming'Casing
11600 Builder'^Default_Switches^Default_Switches^("Ada")
11604 The prefix of an attribute may be:
11606 @item @code{project} for an attribute of the current project
11607 @item The name of an existing package of the current project
11608 @item The name of an imported project
11609 @item The name of a parent project that is extended by the current project
11610 @item An expanded name whose prefix is imported/parent project name,
11611 and whose selector is a package name
11616 @smallexample @c projectfile
11619 for Source_Dirs use project'Source_Dirs & "units";
11620 for Source_Dirs use project'Source_Dirs & "test/drivers"
11626 In the first attribute declaration, initially the attribute @code{Source_Dirs}
11627 has the default value: an empty string list. After this declaration,
11628 @code{Source_Dirs} is a string list of one element: @code{"units"}.
11629 After the second attribute declaration @code{Source_Dirs} is a string list of
11630 two elements: @code{"units"} and @code{"test/drivers"}.
11632 Note: this example is for illustration only. In practice,
11633 the project file would contain only one attribute declaration:
11635 @smallexample @c projectfile
11636 for Source_Dirs use ("units", "test/drivers");
11639 @node Associative Array Attributes
11640 @subsection Associative Array Attributes
11643 Some attributes are defined as @emph{associative arrays}. An associative
11644 array may be regarded as a function that takes a string as a parameter
11645 and delivers a string or string list value as its result.
11647 Here are some examples of single associative array attribute associations:
11649 @smallexample @c projectfile
11650 for Body ("main") use "Main.ada";
11651 for ^Switches^Switches^ ("main.ada")
11653 "^-gnatv^-gnatv^");
11654 for ^Switches^Switches^ ("main.ada")
11655 use Builder'^Switches^Switches^ ("main.ada")
11660 Like untyped variables and simple attributes, associative array attributes
11661 may be declared several times. Each declaration supplies a new value for the
11662 attribute, and replaces the previous setting.
11665 An associative array attribute may be declared as a full associative array
11666 declaration, with the value of the same attribute in an imported or extended
11669 @smallexample @c projectfile
11671 for Default_Switches use Default.Builder'Default_Switches;
11676 In this example, @code{Default} must be either an project imported by the
11677 current project, or the project that the current project extends. If the
11678 attribute is in a package (in this case, in package @code{Builder}), the same
11679 package needs to be specified.
11682 A full associative array declaration replaces any other declaration for the
11683 attribute, including other full associative array declaration. Single
11684 associative array associations may be declare after a full associative
11685 declaration, modifying the value for a single association of the attribute.
11687 @node case Constructions
11688 @subsection @code{case} Constructions
11691 A @code{case} construction is used in a project file to effect conditional
11693 Here is a typical example:
11695 @smallexample @c projectfile
11698 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
11700 OS : OS_Type := external ("OS", "GNU/Linux");
11704 package Compiler is
11706 when "GNU/Linux" | "Unix" =>
11707 for ^Default_Switches^Default_Switches^ ("Ada")
11708 use ("^-gnath^-gnath^");
11710 for ^Default_Switches^Default_Switches^ ("Ada")
11711 use ("^-gnatP^-gnatP^");
11720 The syntax of a @code{case} construction is based on the Ada case statement
11721 (although there is no @code{null} construction for empty alternatives).
11723 The case expression must a typed string variable.
11724 Each alternative comprises the reserved word @code{when}, either a list of
11725 literal strings separated by the @code{"|"} character or the reserved word
11726 @code{others}, and the @code{"=>"} token.
11727 Each literal string must belong to the string type that is the type of the
11729 An @code{others} alternative, if present, must occur last.
11731 After each @code{=>}, there are zero or more constructions. The only
11732 constructions allowed in a case construction are other case constructions and
11733 attribute declarations. String type declarations, variable declarations and
11734 package declarations are not allowed.
11736 The value of the case variable is often given by an external reference
11737 (see @ref{External References in Project Files}).
11739 @c ****************************************
11740 @c * Objects and Sources in Project Files *
11741 @c ****************************************
11743 @node Objects and Sources in Project Files
11744 @section Objects and Sources in Project Files
11747 * Object Directory::
11749 * Source Directories::
11750 * Source File Names::
11754 Each project has exactly one object directory and one or more source
11755 directories. The source directories must contain at least one source file,
11756 unless the project file explicitly specifies that no source files are present
11757 (see @ref{Source File Names}).
11759 @node Object Directory
11760 @subsection Object Directory
11763 The object directory for a project is the directory containing the compiler's
11764 output (such as @file{ALI} files and object files) for the project's immediate
11767 The object directory is given by the value of the attribute @code{Object_Dir}
11768 in the project file.
11770 @smallexample @c projectfile
11771 for Object_Dir use "objects";
11775 The attribute @var{Object_Dir} has a string value, the path name of the object
11776 directory. The path name may be absolute or relative to the directory of the
11777 project file. This directory must already exist, and be readable and writable.
11779 By default, when the attribute @code{Object_Dir} is not given an explicit value
11780 or when its value is the empty string, the object directory is the same as the
11781 directory containing the project file.
11783 @node Exec Directory
11784 @subsection Exec Directory
11787 The exec directory for a project is the directory containing the executables
11788 for the project's main subprograms.
11790 The exec directory is given by the value of the attribute @code{Exec_Dir}
11791 in the project file.
11793 @smallexample @c projectfile
11794 for Exec_Dir use "executables";
11798 The attribute @var{Exec_Dir} has a string value, the path name of the exec
11799 directory. The path name may be absolute or relative to the directory of the
11800 project file. This directory must already exist, and be writable.
11802 By default, when the attribute @code{Exec_Dir} is not given an explicit value
11803 or when its value is the empty string, the exec directory is the same as the
11804 object directory of the project file.
11806 @node Source Directories
11807 @subsection Source Directories
11810 The source directories of a project are specified by the project file
11811 attribute @code{Source_Dirs}.
11813 This attribute's value is a string list. If the attribute is not given an
11814 explicit value, then there is only one source directory, the one where the
11815 project file resides.
11817 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
11820 @smallexample @c projectfile
11821 for Source_Dirs use ();
11825 indicates that the project contains no source files.
11827 Otherwise, each string in the string list designates one or more
11828 source directories.
11830 @smallexample @c projectfile
11831 for Source_Dirs use ("sources", "test/drivers");
11835 If a string in the list ends with @code{"/**"}, then the directory whose path
11836 name precedes the two asterisks, as well as all its subdirectories
11837 (recursively), are source directories.
11839 @smallexample @c projectfile
11840 for Source_Dirs use ("/system/sources/**");
11844 Here the directory @code{/system/sources} and all of its subdirectories
11845 (recursively) are source directories.
11847 To specify that the source directories are the directory of the project file
11848 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
11849 @smallexample @c projectfile
11850 for Source_Dirs use ("./**");
11854 Each of the source directories must exist and be readable.
11856 @node Source File Names
11857 @subsection Source File Names
11860 In a project that contains source files, their names may be specified by the
11861 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
11862 (a string). Source file names never include any directory information.
11864 If the attribute @code{Source_Files} is given an explicit value, then each
11865 element of the list is a source file name.
11867 @smallexample @c projectfile
11868 for Source_Files use ("main.adb");
11869 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
11873 If the attribute @code{Source_Files} is not given an explicit value,
11874 but the attribute @code{Source_List_File} is given a string value,
11875 then the source file names are contained in the text file whose path name
11876 (absolute or relative to the directory of the project file) is the
11877 value of the attribute @code{Source_List_File}.
11879 Each line in the file that is not empty or is not a comment
11880 contains a source file name.
11882 @smallexample @c projectfile
11883 for Source_List_File use "source_list.txt";
11887 By default, if neither the attribute @code{Source_Files} nor the attribute
11888 @code{Source_List_File} is given an explicit value, then each file in the
11889 source directories that conforms to the project's naming scheme
11890 (see @ref{Naming Schemes}) is an immediate source of the project.
11892 A warning is issued if both attributes @code{Source_Files} and
11893 @code{Source_List_File} are given explicit values. In this case, the attribute
11894 @code{Source_Files} prevails.
11896 Each source file name must be the name of one existing source file
11897 in one of the source directories.
11899 A @code{Source_Files} attribute whose value is an empty list
11900 indicates that there are no source files in the project.
11902 If the order of the source directories is known statically, that is if
11903 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
11904 be several files with the same source file name. In this case, only the file
11905 in the first directory is considered as an immediate source of the project
11906 file. If the order of the source directories is not known statically, it is
11907 an error to have several files with the same source file name.
11909 Projects can be specified to have no Ada source
11910 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
11911 list, or the @code{"Ada"} may be absent from @code{Languages}:
11913 @smallexample @c projectfile
11914 for Source_Dirs use ();
11915 for Source_Files use ();
11916 for Languages use ("C", "C++");
11920 Otherwise, a project must contain at least one immediate source.
11922 Projects with no source files are useful as template packages
11923 (see @ref{Packages in Project Files}) for other projects; in particular to
11924 define a package @code{Naming} (see @ref{Naming Schemes}).
11926 @c ****************************
11927 @c * Importing Projects *
11928 @c ****************************
11930 @node Importing Projects
11931 @section Importing Projects
11934 An immediate source of a project P may depend on source files that
11935 are neither immediate sources of P nor in the predefined library.
11936 To get this effect, P must @emph{import} the projects that contain the needed
11939 @smallexample @c projectfile
11941 with "project1", "utilities.gpr";
11942 with "/namings/apex.gpr";
11949 As can be seen in this example, the syntax for importing projects is similar
11950 to the syntax for importing compilation units in Ada. However, project files
11951 use literal strings instead of names, and the @code{with} clause identifies
11952 project files rather than packages.
11954 Each literal string is the file name or path name (absolute or relative) of a
11955 project file. If a string is simply a file name, with no path, then its
11956 location is determined by the @emph{project path}:
11960 If the ^environment variable^logical name^ @env{ADA_PROJECT_PATH} exists,
11961 then the project path includes all the directories in this
11962 ^environment variable^logical name^, plus the directory of the project file.
11965 If the ^environment variable^logical name^ @env{ADA_PROJECT_PATH} does not
11966 exist, then the project path contains only one directory, namely the one where
11967 the project file is located.
11971 If a relative pathname is used, as in
11973 @smallexample @c projectfile
11978 then the path is relative to the directory where the importing project file is
11979 located. Any symbolic link will be fully resolved in the directory
11980 of the importing project file before the imported project file is examined.
11982 If the @code{with}'ed project file name does not have an extension,
11983 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
11984 then the file name as specified in the @code{with} clause (no extension) will
11985 be used. In the above example, if a file @code{project1.gpr} is found, then it
11986 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
11987 then it will be used; if neither file exists, this is an error.
11989 A warning is issued if the name of the project file does not match the
11990 name of the project; this check is case insensitive.
11992 Any source file that is an immediate source of the imported project can be
11993 used by the immediate sources of the importing project, transitively. Thus
11994 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
11995 sources of @code{A} may depend on the immediate sources of @code{C}, even if
11996 @code{A} does not import @code{C} explicitly. However, this is not recommended,
11997 because if and when @code{B} ceases to import @code{C}, some sources in
11998 @code{A} will no longer compile.
12000 A side effect of this capability is that normally cyclic dependencies are not
12001 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
12002 is not allowed to import @code{A}. However, there are cases when cyclic
12003 dependencies would be beneficial. For these cases, another form of import
12004 between projects exists, the @code{limited with}: a project @code{A} that
12005 imports a project @code{B} with a straigh @code{with} may also be imported,
12006 directly or indirectly, by @code{B} on the condition that imports from @code{B}
12007 to @code{A} include at least one @code{limited with}.
12009 @smallexample @c 0projectfile
12015 limited with "../a/a.gpr";
12023 limited with "../a/a.gpr";
12029 In the above legal example, there are two project cycles:
12032 @item A -> C -> D -> A
12036 In each of these cycle there is one @code{limited with}: import of @code{A}
12037 from @code{B} and import of @code{A} from @code{D}.
12039 The difference between straight @code{with} and @code{limited with} is that
12040 the name of a project imported with a @code{limited with} cannot be used in the
12041 project that imports it. In particular, its packages cannot be renamed and
12042 its variables cannot be referred to.
12044 An exception to the above rules for @code{limited with} is that for the main
12045 project specified to @command{gnatmake} or to the @command{GNAT} driver a
12046 @code{limited with} is equivalent to a straight @code{with}. For example,
12047 in the example above, projects @code{B} and @code{D} could not be main
12048 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
12049 each have a @code{limited with} that is the only one in a cycle of importing
12052 @c *********************
12053 @c * Project Extension *
12054 @c *********************
12056 @node Project Extension
12057 @section Project Extension
12060 During development of a large system, it is sometimes necessary to use
12061 modified versions of some of the source files, without changing the original
12062 sources. This can be achieved through the @emph{project extension} facility.
12064 @smallexample @c projectfile
12065 project Modified_Utilities extends "/baseline/utilities.gpr" is ...
12069 A project extension declaration introduces an extending project
12070 (the @emph{child}) and a project being extended (the @emph{parent}).
12072 By default, a child project inherits all the sources of its parent.
12073 However, inherited sources can be overridden: a unit in a parent is hidden
12074 by a unit of the same name in the child.
12076 Inherited sources are considered to be sources (but not immediate sources)
12077 of the child project; see @ref{Project File Syntax}.
12079 An inherited source file retains any switches specified in the parent project.
12081 For example if the project @code{Utilities} contains the specification and the
12082 body of an Ada package @code{Util_IO}, then the project
12083 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
12084 The original body of @code{Util_IO} will not be considered in program builds.
12085 However, the package specification will still be found in the project
12088 A child project can have only one parent but it may import any number of other
12091 A project is not allowed to import directly or indirectly at the same time a
12092 child project and any of its ancestors.
12094 @c ****************************************
12095 @c * External References in Project Files *
12096 @c ****************************************
12098 @node External References in Project Files
12099 @section External References in Project Files
12102 A project file may contain references to external variables; such references
12103 are called @emph{external references}.
12105 An external variable is either defined as part of the environment (an
12106 environment variable in Unix, for example) or else specified on the command
12107 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
12108 If both, then the command line value is used.
12110 The value of an external reference is obtained by means of the built-in
12111 function @code{external}, which returns a string value.
12112 This function has two forms:
12114 @item @code{external (external_variable_name)}
12115 @item @code{external (external_variable_name, default_value)}
12119 Each parameter must be a string literal. For example:
12121 @smallexample @c projectfile
12123 external ("OS", "GNU/Linux")
12127 In the form with one parameter, the function returns the value of
12128 the external variable given as parameter. If this name is not present in the
12129 environment, the function returns an empty string.
12131 In the form with two string parameters, the second argument is
12132 the value returned when the variable given as the first argument is not
12133 present in the environment. In the example above, if @code{"OS"} is not
12134 the name of ^an environment variable^a logical name^ and is not passed on
12135 the command line, then the returned value is @code{"GNU/Linux"}.
12137 An external reference may be part of a string expression or of a string
12138 list expression, and can therefore appear in a variable declaration or
12139 an attribute declaration.
12141 @smallexample @c projectfile
12143 type Mode_Type is ("Debug", "Release");
12144 Mode : Mode_Type := external ("MODE");
12151 @c *****************************
12152 @c * Packages in Project Files *
12153 @c *****************************
12155 @node Packages in Project Files
12156 @section Packages in Project Files
12159 A @emph{package} defines the settings for project-aware tools within a
12161 For each such tool one can declare a package; the names for these
12162 packages are preset (see @ref{Packages}).
12163 A package may contain variable declarations, attribute declarations, and case
12166 @smallexample @c projectfile
12169 package Builder is -- used by gnatmake
12170 for ^Default_Switches^Default_Switches^ ("Ada")
12179 The syntax of package declarations mimics that of package in Ada.
12181 Most of the packages have an attribute
12182 @code{^Default_Switches^Default_Switches^}.
12183 This attribute is an associative array, and its value is a string list.
12184 The index of the associative array is the name of a programming language (case
12185 insensitive). This attribute indicates the ^switch^switch^
12186 or ^switches^switches^ to be used
12187 with the corresponding tool.
12189 Some packages also have another attribute, @code{^Switches^Switches^},
12190 an associative array whose value is a string list.
12191 The index is the name of a source file.
12192 This attribute indicates the ^switch^switch^
12193 or ^switches^switches^ to be used by the corresponding
12194 tool when dealing with this specific file.
12196 Further information on these ^switch^switch^-related attributes is found in
12197 @ref{^Switches^Switches^ and Project Files}.
12199 A package may be declared as a @emph{renaming} of another package; e.g., from
12200 the project file for an imported project.
12202 @smallexample @c projectfile
12204 with "/global/apex.gpr";
12206 package Naming renames Apex.Naming;
12213 Packages that are renamed in other project files often come from project files
12214 that have no sources: they are just used as templates. Any modification in the
12215 template will be reflected automatically in all the project files that rename
12216 a package from the template.
12218 In addition to the tool-oriented packages, you can also declare a package
12219 named @code{Naming} to establish specialized source file naming conventions
12220 (see @ref{Naming Schemes}).
12222 @c ************************************
12223 @c * Variables from Imported Projects *
12224 @c ************************************
12226 @node Variables from Imported Projects
12227 @section Variables from Imported Projects
12230 An attribute or variable defined in an imported or parent project can
12231 be used in expressions in the importing / extending project.
12232 Such an attribute or variable is denoted by an expanded name whose prefix
12233 is either the name of the project or the expanded name of a package within
12236 @smallexample @c projectfile
12239 project Main extends "base" is
12240 Var1 := Imported.Var;
12241 Var2 := Base.Var & ".new";
12246 for ^Default_Switches^Default_Switches^ ("Ada")
12247 use Imported.Builder.Ada_^Switches^Switches^ &
12248 "^-gnatg^-gnatg^" &
12254 package Compiler is
12255 for ^Default_Switches^Default_Switches^ ("Ada")
12256 use Base.Compiler.Ada_^Switches^Switches^;
12267 The value of @code{Var1} is a copy of the variable @code{Var} defined
12268 in the project file @file{"imported.gpr"}
12270 the value of @code{Var2} is a copy of the value of variable @code{Var}
12271 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
12273 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
12274 @code{Builder} is a string list that includes in its value a copy of the value
12275 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
12276 in project file @file{imported.gpr} plus two new elements:
12277 @option{"^-gnatg^-gnatg^"}
12278 and @option{"^-v^-v^"};
12280 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
12281 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
12282 defined in the @code{Compiler} package in project file @file{base.gpr},
12283 the project being extended.
12286 @c ******************
12287 @c * Naming Schemes *
12288 @c ******************
12290 @node Naming Schemes
12291 @section Naming Schemes
12294 Sometimes an Ada software system is ported from a foreign compilation
12295 environment to GNAT, and the file names do not use the default GNAT
12296 conventions. Instead of changing all the file names (which for a variety
12297 of reasons might not be possible), you can define the relevant file
12298 naming scheme in the @code{Naming} package in your project file.
12301 Note that the use of pragmas described in @ref{Alternative
12302 File Naming Schemes} by mean of a configuration pragmas file is not
12303 supported when using project files. You must use the features described
12304 in this paragraph. You can however use specify other configuration
12305 pragmas (see @ref{Specifying Configuration Pragmas}).
12308 For example, the following
12309 package models the Apex file naming rules:
12311 @smallexample @c projectfile
12314 for Casing use "lowercase";
12315 for Dot_Replacement use ".";
12316 for Spec_Suffix ("Ada") use ".1.ada";
12317 for Body_Suffix ("Ada") use ".2.ada";
12324 For example, the following package models the DEC Ada file naming rules:
12326 @smallexample @c projectfile
12329 for Casing use "lowercase";
12330 for Dot_Replacement use "__";
12331 for Spec_Suffix ("Ada") use "_.^ada^ada^";
12332 for Body_Suffix ("Ada") use ".^ada^ada^";
12338 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
12339 names in lower case)
12343 You can define the following attributes in package @code{Naming}:
12348 This must be a string with one of the three values @code{"lowercase"},
12349 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
12352 If @var{Casing} is not specified, then the default is @code{"lowercase"}.
12354 @item @var{Dot_Replacement}
12355 This must be a string whose value satisfies the following conditions:
12358 @item It must not be empty
12359 @item It cannot start or end with an alphanumeric character
12360 @item It cannot be a single underscore
12361 @item It cannot start with an underscore followed by an alphanumeric
12362 @item It cannot contain a dot @code{'.'} except if the entire string
12367 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
12369 @item @var{Spec_Suffix}
12370 This is an associative array (indexed by the programming language name, case
12371 insensitive) whose value is a string that must satisfy the following
12375 @item It must not be empty
12376 @item It must include at least one dot
12379 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
12380 @code{"^.ads^.ADS^"}.
12382 @item @var{Body_Suffix}
12383 This is an associative array (indexed by the programming language name, case
12384 insensitive) whose value is a string that must satisfy the following
12388 @item It must not be empty
12389 @item It must include at least one dot
12390 @item It cannot end with the same string as @code{Spec_Suffix ("Ada")}
12393 If @code{Body_Suffix ("Ada")} is not specified, then the default is
12394 @code{"^.adb^.ADB^"}.
12396 @item @var{Separate_Suffix}
12397 This must be a string whose value satisfies the same conditions as
12398 @code{Body_Suffix}.
12401 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
12402 value as @code{Body_Suffix ("Ada")}.
12406 You can use the associative array attribute @code{Spec} to define
12407 the source file name for an individual Ada compilation unit's spec. The array
12408 index must be a string literal that identifies the Ada unit (case insensitive).
12409 The value of this attribute must be a string that identifies the file that
12410 contains this unit's spec (case sensitive or insensitive depending on the
12413 @smallexample @c projectfile
12414 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
12419 You can use the associative array attribute @code{Body} to
12420 define the source file name for an individual Ada compilation unit's body
12421 (possibly a subunit). The array index must be a string literal that identifies
12422 the Ada unit (case insensitive). The value of this attribute must be a string
12423 that identifies the file that contains this unit's body or subunit (case
12424 sensitive or insensitive depending on the operating system).
12426 @smallexample @c projectfile
12427 for Body ("MyPack.MyChild") use "mypack.mychild.body";
12431 @c ********************
12432 @c * Library Projects *
12433 @c ********************
12435 @node Library Projects
12436 @section Library Projects
12439 @emph{Library projects} are projects whose object code is placed in a library.
12440 (Note that this facility is not yet supported on all platforms)
12442 To create a library project, you need to define in its project file
12443 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
12444 Additionally, you may define the library-related attributes
12445 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
12446 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
12448 The @code{Library_Name} attribute has a string value. There is no restriction
12449 on the name of a library. It is the responsability of the developer to
12450 choose a name that will be accepted by the platform. It is recommanded to
12451 choose names that could be Ada identifiers; such names are almost guaranteed
12452 to be acceptable on all platforms.
12454 The @code{Library_Dir} attribute has a string value that designates the path
12455 (absolute or relative) of the directory where the library will reside.
12456 It must designate an existing directory, and this directory must be
12457 different from the project's object directory. It also needs to be writable.
12458 The directory should only be used for one library; the reason is that all
12459 files contained in this directory may be deleted by the Project Manager.
12461 If both @code{Library_Name} and @code{Library_Dir} are specified and
12462 are legal, then the project file defines a library project. The optional
12463 library-related attributes are checked only for such project files.
12465 The @code{Library_Kind} attribute has a string value that must be one of the
12466 following (case insensitive): @code{"static"}, @code{"dynamic"} or
12467 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
12468 attribute is not specified, the library is a static library, that is
12469 an archive of object files that can be potentially linked into an
12470 static executable. Otherwise, the library may be dynamic or
12471 relocatable, that is a library that is loaded only at the start of execution.
12473 If you need to build both a static and a dynamic library, you should use two
12474 different object directories, since in some cases some extra code needs to
12475 be generated for the latter. For such cases, it is recommended to either use
12476 two different project files, or a single one which uses external variables
12477 to indicate what kind of library should be build.
12479 The @code{Library_Version} attribute has a string value whose interpretation
12480 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
12481 used only for dynamic/relocatable libraries as the internal name of the
12482 library (the @code{"soname"}). If the library file name (built from the
12483 @code{Library_Name}) is different from the @code{Library_Version}, then the
12484 library file will be a symbolic link to the actual file whose name will be
12485 @code{Library_Version}.
12489 @smallexample @c projectfile
12495 for Library_Dir use "lib_dir";
12496 for Library_Name use "dummy";
12497 for Library_Kind use "relocatable";
12498 for Library_Version use "libdummy.so." & Version;
12505 Directory @file{lib_dir} will contain the internal library file whose name
12506 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
12507 @file{libdummy.so.1}.
12509 When @command{gnatmake} detects that a project file
12510 is a library project file, it will check all immediate sources of the project
12511 and rebuild the library if any of the sources have been recompiled.
12513 Standard project files can import library project files. In such cases,
12514 the libraries will only be rebuild if some of its sources are recompiled
12515 because they are in the closure of some other source in an importing project.
12516 Sources of the library project files that are not in such a closure will
12517 not be checked, unless the full library is checked, because one of its sources
12518 needs to be recompiled.
12520 For instance, assume the project file @code{A} imports the library project file
12521 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
12522 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
12523 @file{l2.ads}, @file{l2.adb}.
12525 If @file{l1.adb} has been modified, then the library associated with @code{L}
12526 will be rebuild when compiling all the immediate sources of @code{A} only
12527 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
12530 To be sure that all the sources in the library associated with @code{L} are
12531 up to date, and that all the sources of parject @code{A} are also up to date,
12532 the following two commands needs to be used:
12539 When a library is built or rebuilt, an attempt is made first to delete all
12540 files in the library directory.
12541 All @file{ALI} files will also be copied from the object directory to the
12542 library directory. To build executables, @command{gnatmake} will use the
12543 library rather than the individual object files.
12546 @c **********************************************
12547 @c * Using Third-Party Libraries through Projects
12548 @c **********************************************
12549 @node Using Third-Party Libraries through Projects
12550 @section Using Third-Party Libraries through Projects
12552 Whether you are exporting your own library to make it available to
12553 clients, or you are using a library provided by a third party, it is
12554 convenient to have project files that automatically set the correct
12555 command line switches for the compiler and linker.
12557 Such project files are very similar to the library project files;
12558 @xref{Library Projects}. The only difference is that you set the
12559 @code{Source_Dirs} and @code{Object_Dir} attribute so that they point to the
12560 directories where, respectively, the sources and the read-only ALI files have
12563 If you need to interface with a set of libraries, as opposed to a
12564 single one, you need to create one library project for each of the
12565 libraries. In addition, a top-level project that imports all these
12566 library projects should be provided, so that the user of your library
12567 has a single @code{with} clause to add to his own projects.
12569 For instance, let's assume you are providing two static libraries
12570 @file{liba.a} and @file{libb.a}. The user needs to link with
12571 both of these libraries. Each of these is associated with its
12572 own set of header files. Let's assume furthermore that all the
12573 header files for the two libraries have been installed in the same
12574 directory @file{headers}. The @file{ALI} files are found in the same
12575 @file{headers} directory.
12577 In this case, you should provide the following three projects:
12579 @smallexample @c projectfile
12581 with "liba", "libb";
12582 project My_Library is
12583 for Source_Dirs use ("headers");
12584 for Object_Dir use "headers";
12590 for Source_Dirs use ();
12591 for Library_Dir use "lib";
12592 for Library_Name use "a";
12593 for Library_Kind use "static";
12599 for Source_Dirs use ();
12600 for Library_Dir use "lib";
12601 for Library_Name use "b";
12602 for Library_Kind use "static";
12607 @c *******************************
12608 @c * Stand-alone Library Projects *
12609 @c *******************************
12611 @node Stand-alone Library Projects
12612 @section Stand-alone Library Projects
12615 A Stand-alone Library is a library that contains the necessary code to
12616 elaborate the Ada units that are included in the library. A Stand-alone
12617 Library is suitable to be used in an executable when the main is not
12618 in Ada. However, Stand-alone Libraries may also be used with an Ada main
12621 A Stand-alone Library Project is a Library Project where the library is
12622 a Stand-alone Library.
12624 To be a Stand-alone Library Project, in addition to the two attributes
12625 that make a project a Library Project (@code{Library_Name} and
12626 @code{Library_Dir}, see @ref{Library Projects}), the attribute
12627 @code{Library_Interface} must be defined.
12629 @smallexample @c projectfile
12631 for Library_Dir use "lib_dir";
12632 for Library_Name use "dummy";
12633 for Library_Interface use ("int1", "int1.child");
12637 Attribute @code{Library_Interface} has a non empty string list value,
12638 each string in the list designating a unit contained in an immediate source
12639 of the project file.
12641 When a Stand-alone Library is built, first the binder is invoked to build
12642 a package whose name depends on the library name
12643 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
12644 This binder-generated package includes initialization and
12645 finalization procedures whose
12646 names depend on the library name (dummyinit and dummyfinal in the example
12647 above). The object corresponding to this package is included in the library.
12649 A dynamic or relocatable Stand-alone Library is automatically initialized
12650 if automatic initialization of Stand-alone Libraries is supported on the
12651 platform and if attribute @code{Library_Auto_Init} is not specified or
12652 is specified with the value "true". A static Stand-alone Library is never
12653 automatically initialized.
12655 Single string attribute @code{Library_Auto_Init} may be specified with only
12656 two possible values: "false" or "true" (case-insensitive). Specifying
12657 "false" for attribute @code{Library_Auto_Init} will prevent automatic
12658 initialization of dynamic or relocatable libraries.
12660 When a non automatically initialized Stand-alone Library is used
12661 in an executable, its initialization procedure must be called before
12662 any service of the library is used.
12663 When the main subprogram is in Ada, it may mean that the initialization
12664 procedure has to be called during elaboration of another package.
12666 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
12667 (those that are listed in attribute @code{Library_Interface}) are copied to
12668 the Library Directory. As a consequence, only the Interface Units may be
12669 imported from Ada units outside of the library. If other units are imported,
12670 the binding phase will fail.
12672 When a Stand-Alone Library is bound, the switches that are specified in
12673 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
12674 used in the call to @command{gnatbind}.
12676 The string list attribute @code{Library_Options} may be used to specified
12677 additional switches to the call to @command{gcc} to link the library.
12679 The attribute @code{Library_Src_Dir}, may be specified for a
12680 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
12681 single string value. Its value must be the path (absolute or relative to the
12682 project directory) of an existing directory. This directory cannot be the
12683 object directory or one of the source directories, but it can be the same as
12684 the library directory. The sources of the Interface
12685 Units of the library, necessary to an Ada client of the library, will be
12686 copied to the designated directory, called Interface Copy directory.
12687 These sources includes the specs of the Interface Units, but they may also
12688 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
12689 are used, or when there is a generic units in the spec. Before the sources
12690 are copied to the Interface Copy directory, an attempt is made to delete all
12691 files in the Interface Copy directory.
12693 @c *************************************
12694 @c * Switches Related to Project Files *
12695 @c *************************************
12696 @node Switches Related to Project Files
12697 @section Switches Related to Project Files
12700 The following switches are used by GNAT tools that support project files:
12704 @item ^-P^/PROJECT_FILE=^@var{project}
12705 @cindex @option{^-P^/PROJECT_FILE^} (any tool supporting project files)
12706 Indicates the name of a project file. This project file will be parsed with
12707 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
12708 if any, and using the external references indicated
12709 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
12711 There may zero, one or more spaces between @option{-P} and @var{project}.
12715 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
12718 Since the Project Manager parses the project file only after all the switches
12719 on the command line are checked, the order of the switches
12720 @option{^-P^/PROJECT_FILE^},
12721 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
12722 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
12724 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
12725 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any tool supporting project files)
12726 Indicates that external variable @var{name} has the value @var{value}.
12727 The Project Manager will use this value for occurrences of
12728 @code{external(name)} when parsing the project file.
12732 If @var{name} or @var{value} includes a space, then @var{name=value} should be
12733 put between quotes.
12741 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
12742 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
12743 @var{name}, only the last one is used.
12746 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
12747 takes precedence over the value of the same name in the environment.
12749 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
12750 @cindex @code{^-vP^/MESSAGES_PROJECT_FILE^} (any tool supporting project files)
12751 @c Previous line uses code vs option command, to stay less than 80 chars
12752 Indicates the verbosity of the parsing of GNAT project files.
12755 @option{-vP0} means Default;
12756 @option{-vP1} means Medium;
12757 @option{-vP2} means High.
12761 There are three possible options for this qualifier: DEFAULT, MEDIUM and
12766 The default is ^Default^DEFAULT^: no output for syntactically correct
12769 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
12770 only the last one is used.
12774 @c **********************************
12775 @c * Tools Supporting Project Files *
12776 @c **********************************
12778 @node Tools Supporting Project Files
12779 @section Tools Supporting Project Files
12782 * gnatmake and Project Files::
12783 * The GNAT Driver and Project Files::
12785 * Glide and Project Files::
12789 @node gnatmake and Project Files
12790 @subsection gnatmake and Project Files
12793 This section covers several topics related to @command{gnatmake} and
12794 project files: defining ^switches^switches^ for @command{gnatmake}
12795 and for the tools that it invokes; specifying configuration pragmas;
12796 the use of the @code{Main} attribute; building and rebuilding library project
12800 * ^Switches^Switches^ and Project Files::
12801 * Specifying Configuration Pragmas::
12802 * Project Files and Main Subprograms::
12803 * Library Project Files::
12806 @node ^Switches^Switches^ and Project Files
12807 @subsubsection ^Switches^Switches^ and Project Files
12810 It is not currently possible to specify VMS style qualifiers in the project
12811 files; only Unix style ^switches^switches^ may be specified.
12815 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
12816 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
12817 attribute, a @code{^Switches^Switches^} attribute, or both;
12818 as their names imply, these ^switch^switch^-related
12819 attributes affect the ^switches^switches^ that are used for each of these GNAT
12821 @command{gnatmake} is invoked. As will be explained below, these
12822 component-specific ^switches^switches^ precede
12823 the ^switches^switches^ provided on the @command{gnatmake} command line.
12825 The @code{^Default_Switches^Default_Switches^} attribute is an associative
12826 array indexed by language name (case insensitive) whose value is a string list.
12829 @smallexample @c projectfile
12831 package Compiler is
12832 for ^Default_Switches^Default_Switches^ ("Ada")
12833 use ("^-gnaty^-gnaty^",
12840 The @code{^Switches^Switches^} attribute is also an associative array,
12841 indexed by a file name (which may or may not be case sensitive, depending
12842 on the operating system) whose value is a string list. For example:
12844 @smallexample @c projectfile
12847 for ^Switches^Switches^ ("main1.adb")
12849 for ^Switches^Switches^ ("main2.adb")
12856 For the @code{Builder} package, the file names must designate source files
12857 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
12858 file names must designate @file{ALI} or source files for main subprograms.
12859 In each case just the file name without an explicit extension is acceptable.
12861 For each tool used in a program build (@command{gnatmake}, the compiler, the
12862 binder, and the linker), the corresponding package @dfn{contributes} a set of
12863 ^switches^switches^ for each file on which the tool is invoked, based on the
12864 ^switch^switch^-related attributes defined in the package.
12865 In particular, the ^switches^switches^
12866 that each of these packages contributes for a given file @var{f} comprise:
12870 the value of attribute @code{^Switches^Switches^ (@var{f})},
12871 if it is specified in the package for the given file,
12873 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
12874 if it is specified in the package.
12878 If neither of these attributes is defined in the package, then the package does
12879 not contribute any ^switches^switches^ for the given file.
12881 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
12882 two sets, in the following order: those contributed for the file
12883 by the @code{Builder} package;
12884 and the switches passed on the command line.
12886 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
12887 the ^switches^switches^ passed to the tool comprise three sets,
12888 in the following order:
12892 the applicable ^switches^switches^ contributed for the file
12893 by the @code{Builder} package in the project file supplied on the command line;
12896 those contributed for the file by the package (in the relevant project file --
12897 see below) corresponding to the tool; and
12900 the applicable switches passed on the command line.
12904 The term @emph{applicable ^switches^switches^} reflects the fact that
12905 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
12906 tools, depending on the individual ^switch^switch^.
12908 @command{gnatmake} may invoke the compiler on source files from different
12909 projects. The Project Manager will use the appropriate project file to
12910 determine the @code{Compiler} package for each source file being compiled.
12911 Likewise for the @code{Binder} and @code{Linker} packages.
12913 As an example, consider the following package in a project file:
12915 @smallexample @c projectfile
12918 package Compiler is
12919 for ^Default_Switches^Default_Switches^ ("Ada")
12921 for ^Switches^Switches^ ("a.adb")
12923 for ^Switches^Switches^ ("b.adb")
12925 "^-gnaty^-gnaty^");
12932 If @command{gnatmake} is invoked with this project file, and it needs to
12933 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
12934 @file{a.adb} will be compiled with the ^switch^switch^
12935 @option{^-O1^-O1^},
12936 @file{b.adb} with ^switches^switches^
12938 and @option{^-gnaty^-gnaty^},
12939 and @file{c.adb} with @option{^-g^-g^}.
12941 The following example illustrates the ordering of the ^switches^switches^
12942 contributed by different packages:
12944 @smallexample @c projectfile
12948 for ^Switches^Switches^ ("main.adb")
12956 package Compiler is
12957 for ^Switches^Switches^ ("main.adb")
12965 If you issue the command:
12968 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
12972 then the compiler will be invoked on @file{main.adb} with the following
12973 sequence of ^switches^switches^
12976 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
12979 with the last @option{^-O^-O^}
12980 ^switch^switch^ having precedence over the earlier ones;
12981 several other ^switches^switches^
12982 (such as @option{^-c^-c^}) are added implicitly.
12984 The ^switches^switches^
12986 and @option{^-O1^-O1^} are contributed by package
12987 @code{Builder}, @option{^-O2^-O2^} is contributed
12988 by the package @code{Compiler}
12989 and @option{^-O0^-O0^} comes from the command line.
12991 The @option{^-g^-g^}
12992 ^switch^switch^ will also be passed in the invocation of
12993 @command{Gnatlink.}
12995 A final example illustrates switch contributions from packages in different
12998 @smallexample @c projectfile
13001 for Source_Files use ("pack.ads", "pack.adb");
13002 package Compiler is
13003 for ^Default_Switches^Default_Switches^ ("Ada")
13004 use ("^-gnata^-gnata^");
13012 for Source_Files use ("foo_main.adb", "bar_main.adb");
13014 for ^Switches^Switches^ ("foo_main.adb")
13022 -- Ada source file:
13024 procedure Foo_Main is
13032 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
13036 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
13037 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
13038 @option{^-gnato^-gnato^} (passed on the command line).
13039 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
13040 are @option{^-g^-g^} from @code{Proj4.Builder},
13041 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
13042 and @option{^-gnato^-gnato^} from the command line.
13045 When using @command{gnatmake} with project files, some ^switches^switches^ or
13046 arguments may be expressed as relative paths. As the working directory where
13047 compilation occurs may change, these relative paths are converted to absolute
13048 paths. For the ^switches^switches^ found in a project file, the relative paths
13049 are relative to the project file directory, for the switches on the command
13050 line, they are relative to the directory where @command{gnatmake} is invoked.
13051 The ^switches^switches^ for which this occurs are:
13057 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
13059 ^-o^-o^, object files specified in package @code{Linker} or after
13060 -largs on the command line). The exception to this rule is the ^switch^switch^
13061 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
13063 @node Specifying Configuration Pragmas
13064 @subsubsection Specifying Configuration Pragmas
13066 When using @command{gnatmake} with project files, if there exists a file
13067 @file{gnat.adc} that contains configuration pragmas, this file will be
13070 Configuration pragmas can be defined by means of the following attributes in
13071 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
13072 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
13074 Both these attributes are single string attributes. Their values is the path
13075 name of a file containing configuration pragmas. If a path name is relative,
13076 then it is relative to the project directory of the project file where the
13077 attribute is defined.
13079 When compiling a source, the configuration pragmas used are, in order,
13080 those listed in the file designated by attribute
13081 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
13082 project file, if it is specified, and those listed in the file designated by
13083 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
13084 the project file of the source, if it exists.
13086 @node Project Files and Main Subprograms
13087 @subsubsection Project Files and Main Subprograms
13090 When using a project file, you can invoke @command{gnatmake}
13091 with one or several main subprograms, by specifying their source files on the
13095 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
13099 Each of these needs to be a source file of the same project, except
13100 when the switch ^-u^/UNIQUE^ is used.
13103 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
13104 same project, one of the project in the tree rooted at the project specified
13105 on the command line. The package @code{Builder} of this common project, the
13106 "main project" is the one that is considered by @command{gnatmake}.
13109 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
13110 imported directly or indirectly by the project specified on the command line.
13111 Note that if such a source file is not part of the project specified on the
13112 command line, the ^switches^switches^ found in package @code{Builder} of the
13113 project specified on the command line, if any, that are transmitted
13114 to the compiler will still be used, not those found in the project file of
13118 When using a project file, you can also invoke @command{gnatmake} without
13119 explicitly specifying any main, and the effect depends on whether you have
13120 defined the @code{Main} attribute. This attribute has a string list value,
13121 where each element in the list is the name of a source file (the file
13122 extension is optional) that contains a unit that can be a main subprogram.
13124 If the @code{Main} attribute is defined in a project file as a non-empty
13125 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
13126 line, then invoking @command{gnatmake} with this project file but without any
13127 main on the command line is equivalent to invoking @command{gnatmake} with all
13128 the file names in the @code{Main} attribute on the command line.
13131 @smallexample @c projectfile
13134 for Main use ("main1", "main2", "main3");
13140 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
13142 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
13144 When the project attribute @code{Main} is not specified, or is specified
13145 as an empty string list, or when the switch @option{-u} is used on the command
13146 line, then invoking @command{gnatmake} with no main on the command line will
13147 result in all immediate sources of the project file being checked, and
13148 potentially recompiled. Depending on the presence of the switch @option{-u},
13149 sources from other project files on which the immediate sources of the main
13150 project file depend are also checked and potentially recompiled. In other
13151 words, the @option{-u} switch is applied to all of the immediate sources of the
13154 When no main is specified on the command line and attribute @code{Main} exists
13155 and includes several mains, or when several mains are specified on the
13156 command line, the default ^switches^switches^ in package @code{Builder} will
13157 be used for all mains, even if there are specific ^switches^switches^
13158 specified for one or several mains.
13160 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
13161 the specific ^switches^switches^ for each main, if they are specified.
13163 @node Library Project Files
13164 @subsubsection Library Project Files
13167 When @command{gnatmake} is invoked with a main project file that is a library
13168 project file, it is not allowed to specify one or more mains on the command
13172 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
13173 ^-l^/ACTION=LINK^ have special meanings.
13176 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
13177 to @command{gnatmake} that @command{gnatbind} should be invoked for the
13180 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
13181 to @command{gnatmake} that the binder generated file should be compiled
13182 (in the case of a stand-alone library) and that the library should be built.
13186 @node The GNAT Driver and Project Files
13187 @subsection The GNAT Driver and Project Files
13190 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
13192 @command{^gnatbind^gnatbind^},
13193 @command{^gnatfind^gnatfind^},
13194 @command{^gnatlink^gnatlink^},
13195 @command{^gnatls^gnatls^},
13196 @command{^gnatelim^gnatelim^},
13197 @command{^gnatpp^gnatpp^},
13198 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
13199 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
13200 They must be invoked through the @command{gnat} driver.
13202 The @command{gnat} driver is a front-end that accepts a number of commands and
13203 call the corresponding tool. It has been designed initially for VMS to convert
13204 VMS style qualifiers to Unix style switches, but it is now available to all
13205 the GNAT supported platforms.
13207 On non VMS platforms, the @command{gnat} driver accepts the following commands
13208 (case insensitive):
13212 BIND to invoke @command{^gnatbind^gnatbind^}
13214 CHOP to invoke @command{^gnatchop^gnatchop^}
13216 CLEAN to invoke @command{^gnatclean^gnatclean^}
13218 COMP or COMPILE to invoke the compiler
13220 ELIM to invoke @command{^gnatelim^gnatelim^}
13222 FIND to invoke @command{^gnatfind^gnatfind^}
13224 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
13226 LINK to invoke @command{^gnatlink^gnatlink^}
13228 LS or LIST to invoke @command{^gnatls^gnatls^}
13230 MAKE to invoke @command{^gnatmake^gnatmake^}
13232 NAME to invoke @command{^gnatname^gnatname^}
13234 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
13236 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
13238 STUB to invoke @command{^gnatstub^gnatstub^}
13240 XREF to invoke @command{^gnatxref^gnatxref^}
13244 (note that the compiler is invoked using the command
13245 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
13248 On non VMS platforms, between @command{gnat} and the command, two
13249 special switches may be used:
13253 @command{-v} to display the invocation of the tool.
13255 @command{-dn} to prevent the @command{gnat} driver from removing
13256 the temporary files it has created. These temporary files are
13257 configuration files and temporary file list files.
13261 The command may be followed by switches and arguments for the invoked
13265 gnat bind -C main.ali
13271 Switches may also be put in text files, one switch per line, and the text
13272 files may be specified with their path name preceded by '@@'.
13275 gnat bind @@args.txt main.ali
13279 In addition, for command BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
13280 PP or PRETTY and XREF, the project file related switches
13281 (@option{^-P^/PROJECT_FILE^},
13282 @option{^-X^/EXTERNAL_REFERENCE^} and
13283 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
13284 the switches of the invoking tool.
13287 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
13288 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
13289 the immediate sources of the specified project file.
13292 For each of these commands, there is optionally a corresponding package
13293 in the main project.
13297 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
13300 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
13303 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
13306 package @code{Eliminate} for command ELIM (invoking
13307 @code{^gnatelim^gnatelim^})
13310 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
13313 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
13316 package @code{Pretty_Printer} for command PP or PRETTY
13317 (invoking @code{^gnatpp^gnatpp^})
13320 package @code{Cross_Reference} for command XREF (invoking
13321 @code{^gnatxref^gnatxref^})
13326 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
13327 a simple variable with a string list value. It contains ^switches^switches^
13328 for the invocation of @code{^gnatls^gnatls^}.
13330 @smallexample @c projectfile
13334 for ^Switches^Switches^
13343 All other packages have two attribute @code{^Switches^Switches^} and
13344 @code{^Default_Switches^Default_Switches^}.
13347 @code{^Switches^Switches^} is an associated array attribute, indexed by the
13348 source file name, that has a string list value: the ^switches^switches^ to be
13349 used when the tool corresponding to the package is invoked for the specific
13353 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
13354 indexed by the programming language that has a string list value.
13355 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
13356 ^switches^switches^ for the invocation of the tool corresponding
13357 to the package, except if a specific @code{^Switches^Switches^} attribute
13358 is specified for the source file.
13360 @smallexample @c projectfile
13364 for Source_Dirs use ("./**");
13367 for ^Switches^Switches^ use
13374 package Compiler is
13375 for ^Default_Switches^Default_Switches^ ("Ada")
13376 use ("^-gnatv^-gnatv^",
13377 "^-gnatwa^-gnatwa^");
13383 for ^Default_Switches^Default_Switches^ ("Ada")
13391 for ^Default_Switches^Default_Switches^ ("Ada")
13393 for ^Switches^Switches^ ("main.adb")
13402 for ^Default_Switches^Default_Switches^ ("Ada")
13409 package Cross_Reference is
13410 for ^Default_Switches^Default_Switches^ ("Ada")
13415 end Cross_Reference;
13421 With the above project file, commands such as
13424 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
13425 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
13426 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
13427 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
13428 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
13432 will set up the environment properly and invoke the tool with the switches
13433 found in the package corresponding to the tool:
13434 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
13435 except @code{^Switches^Switches^ ("main.adb")}
13436 for @code{^gnatlink^gnatlink^}.
13439 @node Glide and Project Files
13440 @subsection Glide and Project Files
13443 Glide will automatically recognize the @file{.gpr} extension for
13444 project files, and will
13445 convert them to its own internal format automatically. However, it
13446 doesn't provide a syntax-oriented editor for modifying these
13448 The project file will be loaded as text when you select the menu item
13449 @code{Ada} @result{} @code{Project} @result{} @code{Edit}.
13450 You can edit this text and save the @file{gpr} file;
13451 when you next select this project file in Glide it
13452 will be automatically reloaded.
13455 @c **********************
13456 @node An Extended Example
13457 @section An Extended Example
13460 Suppose that we have two programs, @var{prog1} and @var{prog2},
13461 whose sources are in corresponding directories. We would like
13462 to build them with a single @command{gnatmake} command, and we want to place
13463 their object files into @file{build} subdirectories of the source directories.
13464 Furthermore, we want to have to have two separate subdirectories
13465 in @file{build} -- @file{release} and @file{debug} -- which will contain
13466 the object files compiled with different set of compilation flags.
13468 In other words, we have the following structure:
13485 Here are the project files that we must place in a directory @file{main}
13486 to maintain this structure:
13490 @item We create a @code{Common} project with a package @code{Compiler} that
13491 specifies the compilation ^switches^switches^:
13496 @b{project} Common @b{is}
13498 @b{for} Source_Dirs @b{use} (); -- No source files
13502 @b{type} Build_Type @b{is} ("release", "debug");
13503 Build : Build_Type := External ("BUILD", "debug");
13506 @b{package} Compiler @b{is}
13507 @b{case} Build @b{is}
13508 @b{when} "release" =>
13509 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
13510 @b{use} ("^-O2^-O2^");
13511 @b{when} "debug" =>
13512 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
13513 @b{use} ("^-g^-g^");
13521 @item We create separate projects for the two programs:
13528 @b{project} Prog1 @b{is}
13530 @b{for} Source_Dirs @b{use} ("prog1");
13531 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
13533 @b{package} Compiler @b{renames} Common.Compiler;
13544 @b{project} Prog2 @b{is}
13546 @b{for} Source_Dirs @b{use} ("prog2");
13547 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
13549 @b{package} Compiler @b{renames} Common.Compiler;
13555 @item We create a wrapping project @code{Main}:
13564 @b{project} Main @b{is}
13566 @b{package} Compiler @b{renames} Common.Compiler;
13572 @item Finally we need to create a dummy procedure that @code{with}s (either
13573 explicitly or implicitly) all the sources of our two programs.
13578 Now we can build the programs using the command
13581 gnatmake ^-P^/PROJECT_FILE=^main dummy
13585 for the Debug mode, or
13589 gnatmake -Pmain -XBUILD=release
13595 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
13600 for the Release mode.
13602 @c ********************************
13603 @c * Project File Complete Syntax *
13604 @c ********************************
13606 @node Project File Complete Syntax
13607 @section Project File Complete Syntax
13611 context_clause project_declaration
13617 @b{with} path_name @{ , path_name @} ;
13622 project_declaration ::=
13623 simple_project_declaration | project_extension
13625 simple_project_declaration ::=
13626 @b{project} <project_>simple_name @b{is}
13627 @{declarative_item@}
13628 @b{end} <project_>simple_name;
13630 project_extension ::=
13631 @b{project} <project_>simple_name @b{extends} path_name @b{is}
13632 @{declarative_item@}
13633 @b{end} <project_>simple_name;
13635 declarative_item ::=
13636 package_declaration |
13637 typed_string_declaration |
13638 other_declarative_item
13640 package_declaration ::=
13641 package_specification | package_renaming
13643 package_specification ::=
13644 @b{package} package_identifier @b{is}
13645 @{simple_declarative_item@}
13646 @b{end} package_identifier ;
13648 package_identifier ::=
13649 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
13650 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
13651 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
13653 package_renaming ::==
13654 @b{package} package_identifier @b{renames}
13655 <project_>simple_name.package_identifier ;
13657 typed_string_declaration ::=
13658 @b{type} <typed_string_>_simple_name @b{is}
13659 ( string_literal @{, string_literal@} );
13661 other_declarative_item ::=
13662 attribute_declaration |
13663 typed_variable_declaration |
13664 variable_declaration |
13667 attribute_declaration ::=
13668 full_associative_array_declaration |
13669 @b{for} attribute_designator @b{use} expression ;
13671 full_associative_array_declaration ::=
13672 @b{for} <associative_array_attribute_>simple_name @b{use}
13673 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
13675 attribute_designator ::=
13676 <simple_attribute_>simple_name |
13677 <associative_array_attribute_>simple_name ( string_literal )
13679 typed_variable_declaration ::=
13680 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
13682 variable_declaration ::=
13683 <variable_>simple_name := expression;
13693 attribute_reference
13699 ( <string_>expression @{ , <string_>expression @} )
13702 @b{external} ( string_literal [, string_literal] )
13704 attribute_reference ::=
13705 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
13707 attribute_prefix ::=
13709 <project_>simple_name | package_identifier |
13710 <project_>simple_name . package_identifier
13712 case_construction ::=
13713 @b{case} <typed_variable_>name @b{is}
13718 @b{when} discrete_choice_list =>
13719 @{case_construction | attribute_declaration@}
13721 discrete_choice_list ::=
13722 string_literal @{| string_literal@} |
13726 simple_name @{. simple_name@}
13729 identifier (same as Ada)
13734 @node The Cross-Referencing Tools gnatxref and gnatfind
13735 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
13740 The compiler generates cross-referencing information (unless
13741 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
13742 This information indicates where in the source each entity is declared and
13743 referenced. Note that entities in package Standard are not included, but
13744 entities in all other predefined units are included in the output.
13746 Before using any of these two tools, you need to compile successfully your
13747 application, so that GNAT gets a chance to generate the cross-referencing
13750 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
13751 information to provide the user with the capability to easily locate the
13752 declaration and references to an entity. These tools are quite similar,
13753 the difference being that @code{gnatfind} is intended for locating
13754 definitions and/or references to a specified entity or entities, whereas
13755 @code{gnatxref} is oriented to generating a full report of all
13758 To use these tools, you must not compile your application using the
13759 @option{-gnatx} switch on the @file{gnatmake} command line
13760 (see @ref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
13761 information will not be generated.
13764 * gnatxref Switches::
13765 * gnatfind Switches::
13766 * Project Files for gnatxref and gnatfind::
13767 * Regular Expressions in gnatfind and gnatxref::
13768 * Examples of gnatxref Usage::
13769 * Examples of gnatfind Usage::
13772 @node gnatxref Switches
13773 @section @code{gnatxref} Switches
13776 The command invocation for @code{gnatxref} is:
13778 $ gnatxref [switches] sourcefile1 [sourcefile2 ...]
13785 @item sourcefile1, sourcefile2
13786 identifies the source files for which a report is to be generated. The
13787 ``with''ed units will be processed too. You must provide at least one file.
13789 These file names are considered to be regular expressions, so for instance
13790 specifying @file{source*.adb} is the same as giving every file in the current
13791 directory whose name starts with @file{source} and whose extension is
13794 You shouldn't specify any directory name, just base names. @command{gnatxref}
13795 and @command{gnatfind} will be able to locate these files by themselves using
13796 the source path. If you specify directories, no result is produced.
13801 The switches can be :
13804 @item ^-a^/ALL_FILES^
13805 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
13806 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
13807 the read-only files found in the library search path. Otherwise, these files
13808 will be ignored. This option can be used to protect Gnat sources or your own
13809 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
13810 much faster, and their output much smaller. Read-only here refers to access
13811 or permissions status in the file system for the current user.
13814 @cindex @option{-aIDIR} (@command{gnatxref})
13815 When looking for source files also look in directory DIR. The order in which
13816 source file search is undertaken is the same as for @file{gnatmake}.
13819 @cindex @option{-aODIR} (@command{gnatxref})
13820 When searching for library and object files, look in directory
13821 DIR. The order in which library files are searched is the same as for
13825 @cindex @option{-nostdinc} (@command{gnatxref})
13826 Do not look for sources in the system default directory.
13829 @cindex @option{-nostdlib} (@command{gnatxref})
13830 Do not look for library files in the system default directory.
13832 @item --RTS=@var{rts-path}
13833 @cindex @option{--RTS} (@command{gnatxref})
13834 Specifies the default location of the runtime library. Same meaning as the
13835 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
13837 @item ^-d^/DERIVED_TYPES^
13838 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
13839 If this switch is set @code{gnatxref} will output the parent type
13840 reference for each matching derived types.
13842 @item ^-f^/FULL_PATHNAME^
13843 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
13844 If this switch is set, the output file names will be preceded by their
13845 directory (if the file was found in the search path). If this switch is
13846 not set, the directory will not be printed.
13848 @item ^-g^/IGNORE_LOCALS^
13849 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
13850 If this switch is set, information is output only for library-level
13851 entities, ignoring local entities. The use of this switch may accelerate
13852 @code{gnatfind} and @code{gnatxref}.
13855 @cindex @option{-IDIR} (@command{gnatxref})
13856 Equivalent to @samp{-aODIR -aIDIR}.
13859 @cindex @option{-pFILE} (@command{gnatxref})
13860 Specify a project file to use @xref{Project Files}. These project files are
13861 the @file{.adp} files used by Glide. If you need to use the @file{.gpr}
13862 project files, you should use gnatxref through the GNAT driver
13863 (@command{gnat xref -Pproject}).
13865 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
13866 project file in the current directory.
13868 If a project file is either specified or found by the tools, then the content
13869 of the source directory and object directory lines are added as if they
13870 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
13871 and @samp{^-aO^OBJECT_SEARCH^}.
13873 Output only unused symbols. This may be really useful if you give your
13874 main compilation unit on the command line, as @code{gnatxref} will then
13875 display every unused entity and 'with'ed package.
13879 Instead of producing the default output, @code{gnatxref} will generate a
13880 @file{tags} file that can be used by vi. For examples how to use this
13881 feature, see @xref{Examples of gnatxref Usage}. The tags file is output
13882 to the standard output, thus you will have to redirect it to a file.
13888 All these switches may be in any order on the command line, and may even
13889 appear after the file names. They need not be separated by spaces, thus
13890 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
13891 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
13893 @node gnatfind Switches
13894 @section @code{gnatfind} Switches
13897 The command line for @code{gnatfind} is:
13900 $ gnatfind [switches] pattern[:sourcefile[:line[:column]]]
13909 An entity will be output only if it matches the regular expression found
13910 in @samp{pattern}, see @xref{Regular Expressions in gnatfind and gnatxref}.
13912 Omitting the pattern is equivalent to specifying @samp{*}, which
13913 will match any entity. Note that if you do not provide a pattern, you
13914 have to provide both a sourcefile and a line.
13916 Entity names are given in Latin-1, with uppercase/lowercase equivalence
13917 for matching purposes. At the current time there is no support for
13918 8-bit codes other than Latin-1, or for wide characters in identifiers.
13921 @code{gnatfind} will look for references, bodies or declarations
13922 of symbols referenced in @file{sourcefile}, at line @samp{line}
13923 and column @samp{column}. See @pxref{Examples of gnatfind Usage}
13924 for syntax examples.
13927 is a decimal integer identifying the line number containing
13928 the reference to the entity (or entities) to be located.
13931 is a decimal integer identifying the exact location on the
13932 line of the first character of the identifier for the
13933 entity reference. Columns are numbered from 1.
13935 @item file1 file2 ...
13936 The search will be restricted to these source files. If none are given, then
13937 the search will be done for every library file in the search path.
13938 These file must appear only after the pattern or sourcefile.
13940 These file names are considered to be regular expressions, so for instance
13941 specifying 'source*.adb' is the same as giving every file in the current
13942 directory whose name starts with 'source' and whose extension is 'adb'.
13944 The location of the spec of the entity will always be displayed, even if it
13945 isn't in one of file1, file2,... The occurrences of the entity in the
13946 separate units of the ones given on the command line will also be displayed.
13948 Note that if you specify at least one file in this part, @code{gnatfind} may
13949 sometimes not be able to find the body of the subprograms...
13954 At least one of 'sourcefile' or 'pattern' has to be present on
13957 The following switches are available:
13961 @item ^-a^/ALL_FILES^
13962 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
13963 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
13964 the read-only files found in the library search path. Otherwise, these files
13965 will be ignored. This option can be used to protect Gnat sources or your own
13966 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
13967 much faster, and their output much smaller. Read-only here refers to access
13968 or permission status in the file system for the current user.
13971 @cindex @option{-aIDIR} (@command{gnatfind})
13972 When looking for source files also look in directory DIR. The order in which
13973 source file search is undertaken is the same as for @file{gnatmake}.
13976 @cindex @option{-aODIR} (@command{gnatfind})
13977 When searching for library and object files, look in directory
13978 DIR. The order in which library files are searched is the same as for
13982 @cindex @option{-nostdinc} (@command{gnatfind})
13983 Do not look for sources in the system default directory.
13986 @cindex @option{-nostdlib} (@command{gnatfind})
13987 Do not look for library files in the system default directory.
13989 @item --RTS=@var{rts-path}
13990 @cindex @option{--RTS} (@command{gnatfind})
13991 Specifies the default location of the runtime library. Same meaning as the
13992 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
13994 @item ^-d^/DERIVED_TYPE_INFORMATION^
13995 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
13996 If this switch is set, then @code{gnatfind} will output the parent type
13997 reference for each matching derived types.
13999 @item ^-e^/EXPRESSIONS^
14000 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
14001 By default, @code{gnatfind} accept the simple regular expression set for
14002 @samp{pattern}. If this switch is set, then the pattern will be
14003 considered as full Unix-style regular expression.
14005 @item ^-f^/FULL_PATHNAME^
14006 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
14007 If this switch is set, the output file names will be preceded by their
14008 directory (if the file was found in the search path). If this switch is
14009 not set, the directory will not be printed.
14011 @item ^-g^/IGNORE_LOCALS^
14012 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
14013 If this switch is set, information is output only for library-level
14014 entities, ignoring local entities. The use of this switch may accelerate
14015 @code{gnatfind} and @code{gnatxref}.
14018 @cindex @option{-IDIR} (@command{gnatfind})
14019 Equivalent to @samp{-aODIR -aIDIR}.
14022 @cindex @option{-pFILE} (@command{gnatfind})
14023 Specify a project file (@pxref{Project Files}) to use.
14024 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
14025 project file in the current directory.
14027 If a project file is either specified or found by the tools, then the content
14028 of the source directory and object directory lines are added as if they
14029 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
14030 @samp{^-aO^/OBJECT_SEARCH^}.
14032 @item ^-r^/REFERENCES^
14033 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
14034 By default, @code{gnatfind} will output only the information about the
14035 declaration, body or type completion of the entities. If this switch is
14036 set, the @code{gnatfind} will locate every reference to the entities in
14037 the files specified on the command line (or in every file in the search
14038 path if no file is given on the command line).
14040 @item ^-s^/PRINT_LINES^
14041 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
14042 If this switch is set, then @code{gnatfind} will output the content
14043 of the Ada source file lines were the entity was found.
14045 @item ^-t^/TYPE_HIERARCHY^
14046 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
14047 If this switch is set, then @code{gnatfind} will output the type hierarchy for
14048 the specified type. It act like -d option but recursively from parent
14049 type to parent type. When this switch is set it is not possible to
14050 specify more than one file.
14055 All these switches may be in any order on the command line, and may even
14056 appear after the file names. They need not be separated by spaces, thus
14057 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
14058 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
14060 As stated previously, gnatfind will search in every directory in the
14061 search path. You can force it to look only in the current directory if
14062 you specify @code{*} at the end of the command line.
14064 @node Project Files for gnatxref and gnatfind
14065 @section Project Files for @command{gnatxref} and @command{gnatfind}
14068 Project files allow a programmer to specify how to compile its
14069 application, where to find sources, etc. These files are used
14071 primarily by the Glide Ada mode, but they can also be used
14074 @code{gnatxref} and @code{gnatfind}.
14076 A project file name must end with @file{.gpr}. If a single one is
14077 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
14078 extract the information from it. If multiple project files are found, none of
14079 them is read, and you have to use the @samp{-p} switch to specify the one
14082 The following lines can be included, even though most of them have default
14083 values which can be used in most cases.
14084 The lines can be entered in any order in the file.
14085 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
14086 each line. If you have multiple instances, only the last one is taken into
14091 [default: @code{"^./^[]^"}]
14092 specifies a directory where to look for source files. Multiple @code{src_dir}
14093 lines can be specified and they will be searched in the order they
14097 [default: @code{"^./^[]^"}]
14098 specifies a directory where to look for object and library files. Multiple
14099 @code{obj_dir} lines can be specified, and they will be searched in the order
14102 @item comp_opt=SWITCHES
14103 [default: @code{""}]
14104 creates a variable which can be referred to subsequently by using
14105 the @code{$@{comp_opt@}} notation. This is intended to store the default
14106 switches given to @command{gnatmake} and @command{gcc}.
14108 @item bind_opt=SWITCHES
14109 [default: @code{""}]
14110 creates a variable which can be referred to subsequently by using
14111 the @samp{$@{bind_opt@}} notation. This is intended to store the default
14112 switches given to @command{gnatbind}.
14114 @item link_opt=SWITCHES
14115 [default: @code{""}]
14116 creates a variable which can be referred to subsequently by using
14117 the @samp{$@{link_opt@}} notation. This is intended to store the default
14118 switches given to @command{gnatlink}.
14120 @item main=EXECUTABLE
14121 [default: @code{""}]
14122 specifies the name of the executable for the application. This variable can
14123 be referred to in the following lines by using the @samp{$@{main@}} notation.
14126 @item comp_cmd=COMMAND
14127 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
14130 @item comp_cmd=COMMAND
14131 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
14133 specifies the command used to compile a single file in the application.
14136 @item make_cmd=COMMAND
14137 [default: @code{"GNAT MAKE $@{main@}
14138 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
14139 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
14140 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
14143 @item make_cmd=COMMAND
14144 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
14145 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
14146 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
14148 specifies the command used to recompile the whole application.
14150 @item run_cmd=COMMAND
14151 [default: @code{"$@{main@}"}]
14152 specifies the command used to run the application.
14154 @item debug_cmd=COMMAND
14155 [default: @code{"gdb $@{main@}"}]
14156 specifies the command used to debug the application
14161 @command{gnatxref} and @command{gnatfind} only take into account the
14162 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
14164 @node Regular Expressions in gnatfind and gnatxref
14165 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
14168 As specified in the section about @command{gnatfind}, the pattern can be a
14169 regular expression. Actually, there are to set of regular expressions
14170 which are recognized by the program :
14173 @item globbing patterns
14174 These are the most usual regular expression. They are the same that you
14175 generally used in a Unix shell command line, or in a DOS session.
14177 Here is a more formal grammar :
14184 term ::= elmt -- matches elmt
14185 term ::= elmt elmt -- concatenation (elmt then elmt)
14186 term ::= * -- any string of 0 or more characters
14187 term ::= ? -- matches any character
14188 term ::= [char @{char@}] -- matches any character listed
14189 term ::= [char - char] -- matches any character in range
14193 @item full regular expression
14194 The second set of regular expressions is much more powerful. This is the
14195 type of regular expressions recognized by utilities such a @file{grep}.
14197 The following is the form of a regular expression, expressed in Ada
14198 reference manual style BNF is as follows
14205 regexp ::= term @{| term@} -- alternation (term or term ...)
14207 term ::= item @{item@} -- concatenation (item then item)
14209 item ::= elmt -- match elmt
14210 item ::= elmt * -- zero or more elmt's
14211 item ::= elmt + -- one or more elmt's
14212 item ::= elmt ? -- matches elmt or nothing
14215 elmt ::= nschar -- matches given character
14216 elmt ::= [nschar @{nschar@}] -- matches any character listed
14217 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
14218 elmt ::= [char - char] -- matches chars in given range
14219 elmt ::= \ char -- matches given character
14220 elmt ::= . -- matches any single character
14221 elmt ::= ( regexp ) -- parens used for grouping
14223 char ::= any character, including special characters
14224 nschar ::= any character except ()[].*+?^^^
14228 Following are a few examples :
14232 will match any of the two strings 'abcde' and 'fghi'.
14235 will match any string like 'abd', 'abcd', 'abccd', 'abcccd', and so on
14238 will match any string which has only lowercase characters in it (and at
14239 least one character
14244 @node Examples of gnatxref Usage
14245 @section Examples of @code{gnatxref} Usage
14247 @subsection General Usage
14250 For the following examples, we will consider the following units :
14252 @smallexample @c ada
14258 3: procedure Foo (B : in Integer);
14265 1: package body Main is
14266 2: procedure Foo (B : in Integer) is
14277 2: procedure Print (B : Integer);
14286 The first thing to do is to recompile your application (for instance, in
14287 that case just by doing a @samp{gnatmake main}, so that GNAT generates
14288 the cross-referencing information.
14289 You can then issue any of the following commands:
14291 @item gnatxref main.adb
14292 @code{gnatxref} generates cross-reference information for main.adb
14293 and every unit 'with'ed by main.adb.
14295 The output would be:
14303 Decl: main.ads 3:20
14304 Body: main.adb 2:20
14305 Ref: main.adb 4:13 5:13 6:19
14308 Ref: main.adb 6:8 7:8
14318 Decl: main.ads 3:15
14319 Body: main.adb 2:15
14322 Body: main.adb 1:14
14325 Ref: main.adb 6:12 7:12
14329 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
14330 its body is in main.adb, line 1, column 14 and is not referenced any where.
14332 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
14333 it referenced in main.adb, line 6 column 12 and line 7 column 12.
14335 @item gnatxref package1.adb package2.ads
14336 @code{gnatxref} will generates cross-reference information for
14337 package1.adb, package2.ads and any other package 'with'ed by any
14343 @subsection Using gnatxref with vi
14345 @code{gnatxref} can generate a tags file output, which can be used
14346 directly from @file{vi}. Note that the standard version of @file{vi}
14347 will not work properly with overloaded symbols. Consider using another
14348 free implementation of @file{vi}, such as @file{vim}.
14351 $ gnatxref -v gnatfind.adb > tags
14355 will generate the tags file for @code{gnatfind} itself (if the sources
14356 are in the search path!).
14358 From @file{vi}, you can then use the command @samp{:tag @i{entity}}
14359 (replacing @i{entity} by whatever you are looking for), and vi will
14360 display a new file with the corresponding declaration of entity.
14363 @node Examples of gnatfind Usage
14364 @section Examples of @code{gnatfind} Usage
14368 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
14369 Find declarations for all entities xyz referenced at least once in
14370 main.adb. The references are search in every library file in the search
14373 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
14376 The output will look like:
14378 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
14379 ^directory/^[directory]^main.adb:24:10: xyz <= body
14380 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
14384 that is to say, one of the entities xyz found in main.adb is declared at
14385 line 12 of main.ads (and its body is in main.adb), and another one is
14386 declared at line 45 of foo.ads
14388 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
14389 This is the same command as the previous one, instead @code{gnatfind} will
14390 display the content of the Ada source file lines.
14392 The output will look like:
14395 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
14397 ^directory/^[directory]^main.adb:24:10: xyz <= body
14399 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
14404 This can make it easier to find exactly the location your are looking
14407 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
14408 Find references to all entities containing an x that are
14409 referenced on line 123 of main.ads.
14410 The references will be searched only in main.ads and foo.adb.
14412 @item gnatfind main.ads:123
14413 Find declarations and bodies for all entities that are referenced on
14414 line 123 of main.ads.
14416 This is the same as @code{gnatfind "*":main.adb:123}.
14418 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
14419 Find the declaration for the entity referenced at column 45 in
14420 line 123 of file main.adb in directory mydir. Note that it
14421 is usual to omit the identifier name when the column is given,
14422 since the column position identifies a unique reference.
14424 The column has to be the beginning of the identifier, and should not
14425 point to any character in the middle of the identifier.
14430 @c *********************************
14431 @node The GNAT Pretty-Printer gnatpp
14432 @chapter The GNAT Pretty-Printer @command{gnatpp}
14434 @cindex Pretty-Printer
14437 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
14438 for source reformatting / pretty-printing.
14439 It takes an Ada source file as input and generates a reformatted
14441 You can specify various style directives via switches; e.g.,
14442 identifier case conventions, rules of indentation, and comment layout.
14444 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
14445 tree for the input source and thus requires the input to be syntactically and
14446 semantically legal.
14447 If this condition is not met, @command{gnatpp} will terminate with an
14448 error message; no output file will be generated.
14450 If the compilation unit
14451 contained in the input source depends semantically upon units located
14452 outside the current directory, you have to provide the source search path
14453 when invoking @command{gnatpp}, if these units are contained in files with
14454 names that do not follow the GNAT file naming rules, you have to provide
14455 the configuration file describing the corresponding naming scheme;
14456 see the description of the @command{gnatpp}
14457 switches below. Another possibility is to use a project file and to
14458 call @command{gnatpp} through the @command{gnat} driver
14460 The @command{gnatpp} command has the form
14463 $ gnatpp [@var{switches}] @var{filename}
14470 @var{switches} is an optional sequence of switches defining such properties as
14471 the formatting rules, the source search path, and the destination for the
14475 @var{filename} is the name (including the extension) of the source file to
14476 reformat; ``wildcards'' or several file names on the same gnatpp command are
14477 allowed. The file name may contain path information; it does not have to
14478 follow the GNAT file naming rules
14483 * Switches for gnatpp::
14484 * Formatting Rules::
14487 @node Switches for gnatpp
14488 @section Switches for @command{gnatpp}
14491 The following subsections describe the various switches accepted by
14492 @command{gnatpp}, organized by category.
14495 You specify a switch by supplying a name and generally also a value.
14496 In many cases the values for a switch with a given name are incompatible with
14498 (for example the switch that controls the casing of a reserved word may have
14499 exactly one value: upper case, lower case, or
14500 mixed case) and thus exactly one such switch can be in effect for an
14501 invocation of @command{gnatpp}.
14502 If more than one is supplied, the last one is used.
14503 However, some values for the same switch are mutually compatible.
14504 You may supply several such switches to @command{gnatpp}, but then
14505 each must be specified in full, with both the name and the value.
14506 Abbreviated forms (the name appearing once, followed by each value) are
14508 For example, to set
14509 the alignment of the assignment delimiter both in declarations and in
14510 assignment statements, you must write @option{-A2A3}
14511 (or @option{-A2 -A3}), but not @option{-A23}.
14515 In many cases the set of options for a given qualifier are incompatible with
14516 each other (for example the qualifier that controls the casing of a reserved
14517 word may have exactly one option, which specifies either upper case, lower
14518 case, or mixed case), and thus exactly one such option can be in effect for
14519 an invocation of @command{gnatpp}.
14520 If more than one is supplied, the last one is used.
14521 However, some qualifiers have options that are mutually compatible,
14522 and then you may then supply several such options when invoking
14526 In most cases, it is obvious whether or not the
14527 ^values for a switch with a given name^options for a given qualifier^
14528 are compatible with each other.
14529 When the semantics might not be evident, the summaries below explicitly
14530 indicate the effect.
14533 * Alignment Control::
14535 * Construct Layout Control::
14536 * General Text Layout Control::
14537 * Other Formatting Options::
14538 * Setting the Source Search Path::
14539 * Output File Control::
14540 * Other gnatpp Switches::
14544 @node Alignment Control
14545 @subsection Alignment Control
14546 @cindex Alignment control in @command{gnatpp}
14549 Programs can be easier to read if certain constructs are vertically aligned.
14550 By default all alignments are set ON.
14551 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
14552 OFF, and then use one or more of the other
14553 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
14554 to activate alignment for specific constructs.
14557 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
14561 Set all alignments to ON
14564 @item ^-A0^/ALIGN=OFF^
14565 Set all alignments to OFF
14567 @item ^-A1^/ALIGN=COLONS^
14568 Align @code{:} in declarations
14570 @item ^-A2^/ALIGN=DECLARATIONS^
14571 Align @code{:=} in initializations in declarations
14573 @item ^-A3^/ALIGN=STATEMENTS^
14574 Align @code{:=} in assignment statements
14576 @item ^-A4^/ALIGN=ARROWS^
14577 Align @code{=>} in associations
14581 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
14585 @node Casing Control
14586 @subsection Casing Control
14587 @cindex Casing control in @command{gnatpp}
14590 @command{gnatpp} allows you to specify the casing for reserved words,
14591 pragma names, attribute designators and identifiers.
14592 For identifiers you may define a
14593 general rule for name casing but also override this rule
14594 via a set of dictionary files.
14596 Three types of casing are supported: lower case, upper case, and mixed case.
14597 Lower and upper case are self-explanatory (but since some letters in
14598 Latin1 and other GNAT-supported character sets
14599 exist only in lower-case form, an upper case conversion will have no
14601 ``Mixed case'' means that the first letter, and also each letter immediately
14602 following an underscore, are converted to their uppercase forms;
14603 all the other letters are converted to their lowercase forms.
14606 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
14607 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
14608 Attribute designators are lower case
14610 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
14611 Attribute designators are upper case
14613 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
14614 Attribute designators are mixed case (this is the default)
14616 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
14617 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
14618 Keywords (technically, these are known in Ada as @emph{reserved words}) are
14619 lower case (this is the default)
14621 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
14622 Keywords are upper case
14624 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
14625 @item ^-nD^/NAME_CASING=AS_DECLARED^
14626 Name casing for defining occurrences are as they appear in the source file
14627 (this is the default)
14629 @item ^-nU^/NAME_CASING=UPPER_CASE^
14630 Names are in upper case
14632 @item ^-nL^/NAME_CASING=LOWER_CASE^
14633 Names are in lower case
14635 @item ^-nM^/NAME_CASING=MIXED_CASE^
14636 Names are in mixed case
14638 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
14639 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
14640 Pragma names are lower case
14642 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
14643 Pragma names are upper case
14645 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
14646 Pragma names are mixed case (this is the default)
14648 @item ^-D@var{file}^/DICTIONARY=@var{file}^
14649 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
14650 Use @var{file} as a @emph{dictionary file} that defines
14651 the casing for a set of specified names,
14652 thereby overriding the effect on these names by
14653 any explicit or implicit
14654 ^-n^/NAME_CASING^ switch.
14655 To supply more than one dictionary file,
14656 use ^several @option{-D} switches^a list of files as options^.
14659 @option{gnatpp} implicitly uses a @emph{default dictionary file}
14660 to define the casing for the Ada predefined names and
14661 the names declared in the GNAT libraries.
14663 @item ^-D-^/SPECIFIC_CASING^
14664 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
14665 Do not use the default dictionary file;
14666 instead, use the casing
14667 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
14672 The structure of a dictionary file, and details on the conventions
14673 used in the default dictionary file, are defined in @ref{Name Casing}.
14675 The @option{^-D-^/SPECIFIC_CASING^} and
14676 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
14680 @node Construct Layout Control
14681 @subsection Construct Layout Control
14682 @cindex Layout control in @command{gnatpp}
14685 This group of @command{gnatpp} switches controls the layout of comments and
14686 complex syntactic constructs. See @ref{Formatting Comments}, for details
14690 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
14691 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
14692 All the comments remain unchanged
14694 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
14695 GNAT-style comment line indentation (this is the default).
14697 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
14698 Reference-manual comment line indentation.
14700 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
14701 GNAT-style comment beginning
14703 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
14704 Reformat comment blocks
14706 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
14707 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
14708 GNAT-style layout (this is the default)
14710 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
14713 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
14716 @item ^-notab^/NOTABS^
14717 All the VT characters are removed from the comment text. All the HT characters
14718 are expanded with the sequences of space characters to get to the next tab
14725 The @option{-c1} and @option{-c2} switches are incompatible.
14726 The @option{-c3} and @option{-c4} switches are compatible with each other and
14727 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
14728 the other comment formatting switches.
14730 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
14735 For the @option{/COMMENTS_LAYOUT} qualifier:
14738 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
14740 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
14741 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
14745 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
14746 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
14749 @node General Text Layout Control
14750 @subsection General Text Layout Control
14753 These switches allow control over line length and indentation.
14756 @item ^-M@i{nnn}^/LINE_LENGTH_MAX=@i{nnn}^
14757 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
14758 Maximum line length, @i{nnn} from 32 ..256, the default value is 79
14760 @item ^-i@i{nnn}^/INDENTATION_LEVEL=@i{nnn}^
14761 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
14762 Indentation level, @i{nnn} from 1 .. 9, the default value is 3
14764 @item ^-cl@i{nnn}^/CONTINUATION_INDENT=@i{nnn}^
14765 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
14766 Indentation level for continuation lines (relative to the line being
14767 continued), @i{nnn} from 1 .. 9.
14769 value is one less then the (normal) indentation level, unless the
14770 indentation is set to 1 (in which case the default value for continuation
14771 line indentation is also 1)
14775 @node Other Formatting Options
14776 @subsection Other Formatting Options
14779 These switches control the inclusion of missing end/exit labels, and
14780 the indentation level in @b{case} statements.
14783 @item ^-e^/NO_MISSED_LABELS^
14784 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
14785 Do not insert missing end/exit labels. An end label is the name of
14786 a construct that may optionally be repeated at the end of the
14787 construct's declaration;
14788 e.g., the names of packages, subprograms, and tasks.
14789 An exit label is the name of a loop that may appear as target
14790 of an exit statement within the loop.
14791 By default, @command{gnatpp} inserts these end/exit labels when
14792 they are absent from the original source. This option suppresses such
14793 insertion, so that the formatted source reflects the original.
14795 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
14796 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
14797 Insert a Form Feed character after a pragma Page.
14799 @item ^-T@i{nnn}^/MAX_INDENT=@i{nnn}^
14800 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
14801 Do not use an additional indentation level for @b{case} alternatives
14802 and variants if there are @i{nnn} or more (the default
14804 If @i{nnn} is 0, an additional indentation level is
14805 used for @b{case} alternatives and variants regardless of their number.
14808 @node Setting the Source Search Path
14809 @subsection Setting the Source Search Path
14812 To define the search path for the input source file, @command{gnatpp}
14813 uses the same switches as the GNAT compiler, with the same effects.
14816 @item ^-I^/SEARCH=^@var{dir}
14817 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
14818 The same as the corresponding gcc switch
14820 @item ^-I-^/NOCURRENT_DIRECTORY^
14821 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
14822 The same as the corresponding gcc switch
14824 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
14825 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
14826 The same as the corresponding gcc switch
14828 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
14829 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
14830 The same as the corresponding gcc switch
14835 @node Output File Control
14836 @subsection Output File Control
14839 By default the output is sent to the file whose name is obtained by appending
14840 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
14841 (if the file with this name already exists, it is unconditionally overwritten).
14842 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
14843 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
14845 The output may be redirected by the following switches:
14848 @item ^-pipe^/STANDARD_OUTPUT^
14849 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
14850 Send the output to @code{Standard_Output}
14852 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
14853 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
14854 Write the output into @var{output_file}.
14855 If @var{output_file} already exists, @command{gnatpp} terminates without
14856 reading or processing the input file.
14858 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
14859 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
14860 Write the output into @var{output_file}, overwriting the existing file
14861 (if one is present).
14863 @item ^-r^/REPLACE^
14864 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
14865 Replace the input source file with the reformatted output, and copy the
14866 original input source into the file whose name is obtained by appending the
14867 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
14868 If a file with this name already exists, @command{gnatpp} terminates without
14869 reading or processing the input file.
14871 @item ^-rf^/OVERRIDING_REPLACE^
14872 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
14873 Like @option{^-r^/REPLACE^} except that if the file with the specified name
14874 already exists, it is overwritten.
14876 @item ^-rnb^/NO_BACKUP^
14877 @cindex @option{^-rnb^/NO_BACKUP^} (@code{gnatpp})
14878 Replace the input source file with the reformatted output without
14879 creating any backup copy of the input source.
14883 Options @option{^-pipe^/STANDARD_OUTPUT^},
14884 @option{^-o^/OUTPUT^} and
14885 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
14886 contains only one file to reformat
14888 @node Other gnatpp Switches
14889 @subsection Other @code{gnatpp} Switches
14892 The additional @command{gnatpp} switches are defined in this subsection.
14895 @item ^-files @var{filename}^/FILES=@var{output_file}^
14896 @cindex @option{^-files^/FILES^} (@code{gnatpp})
14897 Take the argument source files from the specified file. This file should be an
14898 ordinary textual file containing file names separated by spaces or
14899 line breaks. You can use this switch more then once in the same call to
14900 @command{gnatpp}. You also can combine this switch with explicit list of
14903 @item ^-v^/VERBOSE^
14904 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
14906 @command{gnatpp} generates version information and then
14907 a trace of the actions it takes to produce or obtain the ASIS tree.
14909 @item ^-w^/WARNINGS^
14910 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
14912 @command{gnatpp} generates a warning whenever it can not provide
14913 a required layout in the result source.
14917 @node Formatting Rules
14918 @section Formatting Rules
14921 The following subsections show how @command{gnatpp} treats ``white space'',
14922 comments, program layout, and name casing.
14923 They provide the detailed descriptions of the switches shown above.
14926 * White Space and Empty Lines::
14927 * Formatting Comments::
14928 * Construct Layout::
14933 @node White Space and Empty Lines
14934 @subsection White Space and Empty Lines
14937 @command{gnatpp} does not have an option to control space characters.
14938 It will add or remove spaces according to the style illustrated by the
14939 examples in the @cite{Ada Reference Manual}.
14941 The only format effectors
14942 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
14943 that will appear in the output file are platform-specific line breaks,
14944 and also format effectors within (but not at the end of) comments.
14945 In particular, each horizontal tab character that is not inside
14946 a comment will be treated as a space and thus will appear in the
14947 output file as zero or more spaces depending on
14948 the reformatting of the line in which it appears.
14949 The only exception is a Form Feed character, which is inserted after a
14950 pragma @code{Page} when @option{-ff} is set.
14952 The output file will contain no lines with trailing ``white space'' (spaces,
14955 Empty lines in the original source are preserved
14956 only if they separate declarations or statements.
14957 In such contexts, a
14958 sequence of two or more empty lines is replaced by exactly one empty line.
14959 Note that a blank line will be removed if it separates two ``comment blocks''
14960 (a comment block is a sequence of whole-line comments).
14961 In order to preserve a visual separation between comment blocks, use an
14962 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
14963 Likewise, if for some reason you wish to have a sequence of empty lines,
14964 use a sequence of empty comments instead.
14967 @node Formatting Comments
14968 @subsection Formatting Comments
14971 Comments in Ada code are of two kinds:
14974 a @emph{whole-line comment}, which appears by itself (possibly preceded by
14975 ``white space'') on a line
14978 an @emph{end-of-line comment}, which follows some other Ada lexical element
14983 The indentation of a whole-line comment is that of either
14984 the preceding or following line in
14985 the formatted source, depending on switch settings as will be described below.
14987 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
14988 between the end of the preceding Ada lexical element and the beginning
14989 of the comment as appear in the original source,
14990 unless either the comment has to be split to
14991 satisfy the line length limitation, or else the next line contains a
14992 whole line comment that is considered a continuation of this end-of-line
14993 comment (because it starts at the same position).
14995 cases, the start of the end-of-line comment is moved right to the nearest
14996 multiple of the indentation level.
14997 This may result in a ``line overflow'' (the right-shifted comment extending
14998 beyond the maximum line length), in which case the comment is split as
15001 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
15002 (GNAT-style comment line indentation)
15003 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
15004 (reference-manual comment line indentation).
15005 With reference-manual style, a whole-line comment is indented as if it
15006 were a declaration or statement at the same place
15007 (i.e., according to the indentation of the preceding line(s)).
15008 With GNAT style, a whole-line comment that is immediately followed by an
15009 @b{if} or @b{case} statement alternative, a record variant, or the reserved
15010 word @b{begin}, is indented based on the construct that follows it.
15013 @smallexample @c ada
15025 Reference-manual indentation produces:
15027 @smallexample @c ada
15039 while GNAT-style indentation produces:
15041 @smallexample @c ada
15053 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
15054 (GNAT style comment beginning) has the following
15059 For each whole-line comment that does not end with two hyphens,
15060 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
15061 to ensure that there are at least two spaces between these hyphens and the
15062 first non-blank character of the comment.
15066 For an end-of-line comment, if in the original source the next line is a
15067 whole-line comment that starts at the same position
15068 as the end-of-line comment,
15069 then the whole-line comment (and all whole-line comments
15070 that follow it and that start at the same position)
15071 will start at this position in the output file.
15074 That is, if in the original source we have:
15076 @smallexample @c ada
15079 A := B + C; -- B must be in the range Low1..High1
15080 -- C must be in the range Low2..High2
15081 --B+C will be in the range Low1+Low2..High1+High2
15087 Then in the formatted source we get
15089 @smallexample @c ada
15092 A := B + C; -- B must be in the range Low1..High1
15093 -- C must be in the range Low2..High2
15094 -- B+C will be in the range Low1+Low2..High1+High2
15100 A comment that exceeds the line length limit will be split.
15102 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
15103 the line belongs to a reformattable block, splitting the line generates a
15104 @command{gnatpp} warning.
15105 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
15106 comments may be reformatted in typical
15107 word processor style (that is, moving words between lines and putting as
15108 many words in a line as possible).
15111 @node Construct Layout
15112 @subsection Construct Layout
15115 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
15116 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
15117 layout on the one hand, and uncompact layout
15118 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
15119 can be illustrated by the following examples:
15123 @multitable @columnfractions .5 .5
15124 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
15127 @smallexample @c ada
15134 @smallexample @c ada
15143 @smallexample @c ada
15151 @smallexample @c ada
15161 @smallexample @c ada
15162 Clear : for J in 1 .. 10 loop
15167 @smallexample @c ada
15169 for J in 1 .. 10 loop
15180 GNAT style, compact layout Uncompact layout
15182 type q is record type q is
15183 a : integer; record
15184 b : integer; a : integer;
15185 end record; b : integer;
15189 Block : declare Block :
15190 A : Integer := 3; declare
15191 begin A : Integer := 3;
15193 end Block; Proc (A, A);
15196 Clear : for J in 1 .. 10 loop Clear :
15197 A (J) := 0; for J in 1 .. 10 loop
15198 end loop Clear; A (J) := 0;
15205 A further difference between GNAT style layout and compact layout is that
15206 GNAT style layout inserts empty lines as separation for
15207 compound statements, return statements and bodies.
15211 @subsection Name Casing
15214 @command{gnatpp} always converts the usage occurrence of a (simple) name to
15215 the same casing as the corresponding defining identifier.
15217 You control the casing for defining occurrences via the
15218 @option{^-n^/NAME_CASING^} switch.
15220 With @option{-nD} (``as declared'', which is the default),
15223 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
15225 defining occurrences appear exactly as in the source file
15226 where they are declared.
15227 The other ^values for this switch^options for this qualifier^ ---
15228 @option{^-nU^UPPER_CASE^},
15229 @option{^-nL^LOWER_CASE^},
15230 @option{^-nM^MIXED_CASE^} ---
15232 ^upper, lower, or mixed case, respectively^the corresponding casing^.
15233 If @command{gnatpp} changes the casing of a defining
15234 occurrence, it analogously changes the casing of all the
15235 usage occurrences of this name.
15237 If the defining occurrence of a name is not in the source compilation unit
15238 currently being processed by @command{gnatpp}, the casing of each reference to
15239 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
15240 switch (subject to the dictionary file mechanism described below).
15241 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
15243 casing for the defining occurrence of the name.
15245 Some names may need to be spelled with casing conventions that are not
15246 covered by the upper-, lower-, and mixed-case transformations.
15247 You can arrange correct casing by placing such names in a
15248 @emph{dictionary file},
15249 and then supplying a @option{^-D^/DICTIONARY^} switch.
15250 The casing of names from dictionary files overrides
15251 any @option{^-n^/NAME_CASING^} switch.
15253 To handle the casing of Ada predefined names and the names from GNAT libraries,
15254 @command{gnatpp} assumes a default dictionary file.
15255 The name of each predefined entity is spelled with the same casing as is used
15256 for the entity in the @cite{Ada Reference Manual}.
15257 The name of each entity in the GNAT libraries is spelled with the same casing
15258 as is used in the declaration of that entity.
15260 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
15261 default dictionary file.
15262 Instead, the casing for predefined and GNAT-defined names will be established
15263 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
15264 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
15265 will appear as just shown,
15266 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
15267 To ensure that even such names are rendered in uppercase,
15268 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
15269 (or else, less conveniently, place these names in upper case in a dictionary
15272 A dictionary file is
15273 a plain text file; each line in this file can be either a blank line
15274 (containing only space characters and ASCII.HT characters), an Ada comment
15275 line, or the specification of exactly one @emph{casing schema}.
15277 A casing schema is a string that has the following syntax:
15281 @var{casing_schema} ::= @var{identifier} | [*]@var{simple_identifier}[*]
15283 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
15288 (The @code{[]} metanotation stands for an optional part;
15289 see @cite{Ada Reference Manual}, Section 2.3) for the definition of the
15290 @var{identifier} lexical element and the @var{letter_or_digit} category).
15292 The casing schema string can be followed by white space and/or an Ada-style
15293 comment; any amount of white space is allowed before the string.
15295 If a dictionary file is passed as
15297 the value of a @option{-D@var{file}} switch
15300 an option to the @option{/DICTIONARY} qualifier
15303 simple name and every identifier, @command{gnatpp} checks if the dictionary
15304 defines the casing for the name or for some of its parts (the term ``subword''
15305 is used below to denote the part of a name which is delimited by ``_'' or by
15306 the beginning or end of the word and which does not contain any ``_'' inside):
15310 if the whole name is in the dictionary, @command{gnatpp} uses for this name
15311 the casing defined by the dictionary; no subwords are checked for this word
15314 for the first subword (that is, for the subword preceding the leftmost
15315 ``_''), @command{gnatpp} checks if the dictionary contains the corresponding
15316 string of the form @code{@var{simple_identifier}*}, and if it does, the
15317 casing of this @var{simple_identifier} is used for this subword
15320 for the last subword (following the rightmost ``_'') @command{gnatpp}
15321 checks if the dictionary contains the corresponding string of the form
15322 @code{*@var{simple_identifier}}, and if it does, the casing of this
15323 @var{simple_identifier} is used for this subword
15326 for every intermediate subword (surrounded by two'_') @command{gnatpp} checks
15327 if the dictionary contains the corresponding string of the form
15328 @code{*@var{simple_identifier}*}, and if it does, the casing of this
15329 simple_identifier is used for this subword
15332 if more than one dictionary file is passed as @command{gnatpp} switches, each
15333 dictionary adds new casing exceptions and overrides all the existing casing
15334 exceptions set by the previous dictionaries
15337 when @command{gnatpp} checks if the word or subword is in the dictionary,
15338 this check is not case sensitive
15342 For example, suppose we have the following source to reformat:
15344 @smallexample @c ada
15347 name1 : integer := 1;
15348 name4_name3_name2 : integer := 2;
15349 name2_name3_name4 : Boolean;
15352 name2_name3_name4 := name4_name3_name2 > name1;
15358 And suppose we have two dictionaries:
15375 If @command{gnatpp} is called with the following switches:
15379 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
15382 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
15387 then we will get the following name casing in the @command{gnatpp} output:
15389 @smallexample @c ada
15392 NAME1 : Integer := 1;
15393 Name4_NAME3_NAME2 : integer := 2;
15394 Name2_NAME3_Name4 : Boolean;
15397 Name2_NAME3_Name4 := Name4_NAME3_NAME2 > NAME1;
15404 @c ***********************************
15405 @node File Name Krunching Using gnatkr
15406 @chapter File Name Krunching Using @code{gnatkr}
15410 This chapter discusses the method used by the compiler to shorten
15411 the default file names chosen for Ada units so that they do not
15412 exceed the maximum length permitted. It also describes the
15413 @code{gnatkr} utility that can be used to determine the result of
15414 applying this shortening.
15418 * Krunching Method::
15419 * Examples of gnatkr Usage::
15423 @section About @code{gnatkr}
15426 The default file naming rule in GNAT
15427 is that the file name must be derived from
15428 the unit name. The exact default rule is as follows:
15431 Take the unit name and replace all dots by hyphens.
15433 If such a replacement occurs in the
15434 second character position of a name, and the first character is
15435 ^a, g, s, or i^A, G, S, or I^ then replace the dot by the character
15436 ^~ (tilde)^$ (dollar sign)^
15437 instead of a minus.
15439 The reason for this exception is to avoid clashes
15440 with the standard names for children of System, Ada, Interfaces,
15441 and GNAT, which use the prefixes ^s- a- i- and g-^S- A- I- and G-^
15444 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
15445 switch of the compiler activates a ``krunching''
15446 circuit that limits file names to nn characters (where nn is a decimal
15447 integer). For example, using OpenVMS,
15448 where the maximum file name length is
15449 39, the value of nn is usually set to 39, but if you want to generate
15450 a set of files that would be usable if ported to a system with some
15451 different maximum file length, then a different value can be specified.
15452 The default value of 39 for OpenVMS need not be specified.
15454 The @code{gnatkr} utility can be used to determine the krunched name for
15455 a given file, when krunched to a specified maximum length.
15458 @section Using @code{gnatkr}
15461 The @code{gnatkr} command has the form
15465 $ gnatkr @var{name} [@var{length}]
15471 $ gnatkr @var{name} /COUNT=nn
15476 @var{name} is the uncrunched file name, derived from the name of the unit
15477 in the standard manner described in the previous section (i.e. in particular
15478 all dots are replaced by hyphens). The file name may or may not have an
15479 extension (defined as a suffix of the form period followed by arbitrary
15480 characters other than period). If an extension is present then it will
15481 be preserved in the output. For example, when krunching @file{hellofile.ads}
15482 to eight characters, the result will be hellofil.ads.
15484 Note: for compatibility with previous versions of @code{gnatkr} dots may
15485 appear in the name instead of hyphens, but the last dot will always be
15486 taken as the start of an extension. So if @code{gnatkr} is given an argument
15487 such as @file{Hello.World.adb} it will be treated exactly as if the first
15488 period had been a hyphen, and for example krunching to eight characters
15489 gives the result @file{hellworl.adb}.
15491 Note that the result is always all lower case (except on OpenVMS where it is
15492 all upper case). Characters of the other case are folded as required.
15494 @var{length} represents the length of the krunched name. The default
15495 when no argument is given is ^8^39^ characters. A length of zero stands for
15496 unlimited, in other words do not chop except for system files where the
15497 impled crunching length is always eight characters.
15500 The output is the krunched name. The output has an extension only if the
15501 original argument was a file name with an extension.
15503 @node Krunching Method
15504 @section Krunching Method
15507 The initial file name is determined by the name of the unit that the file
15508 contains. The name is formed by taking the full expanded name of the
15509 unit and replacing the separating dots with hyphens and
15510 using ^lowercase^uppercase^
15511 for all letters, except that a hyphen in the second character position is
15512 replaced by a ^tilde^dollar sign^ if the first character is
15513 ^a, i, g, or s^A, I, G, or S^.
15514 The extension is @code{.ads} for a
15515 specification and @code{.adb} for a body.
15516 Krunching does not affect the extension, but the file name is shortened to
15517 the specified length by following these rules:
15521 The name is divided into segments separated by hyphens, tildes or
15522 underscores and all hyphens, tildes, and underscores are
15523 eliminated. If this leaves the name short enough, we are done.
15526 If the name is too long, the longest segment is located (left-most
15527 if there are two of equal length), and shortened by dropping
15528 its last character. This is repeated until the name is short enough.
15530 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
15531 to fit the name into 8 characters as required by some operating systems.
15534 our-strings-wide_fixed 22
15535 our strings wide fixed 19
15536 our string wide fixed 18
15537 our strin wide fixed 17
15538 our stri wide fixed 16
15539 our stri wide fixe 15
15540 our str wide fixe 14
15541 our str wid fixe 13
15547 Final file name: oustwifi.adb
15551 The file names for all predefined units are always krunched to eight
15552 characters. The krunching of these predefined units uses the following
15553 special prefix replacements:
15557 replaced by @file{^a^A^-}
15560 replaced by @file{^g^G^-}
15563 replaced by @file{^i^I^-}
15566 replaced by @file{^s^S^-}
15569 These system files have a hyphen in the second character position. That
15570 is why normal user files replace such a character with a
15571 ^tilde^dollar sign^, to
15572 avoid confusion with system file names.
15574 As an example of this special rule, consider
15575 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
15578 ada-strings-wide_fixed 22
15579 a- strings wide fixed 18
15580 a- string wide fixed 17
15581 a- strin wide fixed 16
15582 a- stri wide fixed 15
15583 a- stri wide fixe 14
15584 a- str wide fixe 13
15590 Final file name: a-stwifi.adb
15594 Of course no file shortening algorithm can guarantee uniqueness over all
15595 possible unit names, and if file name krunching is used then it is your
15596 responsibility to ensure that no name clashes occur. The utility
15597 program @code{gnatkr} is supplied for conveniently determining the
15598 krunched name of a file.
15600 @node Examples of gnatkr Usage
15601 @section Examples of @code{gnatkr} Usage
15608 $ gnatkr very_long_unit_name.ads --> velounna.ads
15609 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
15610 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
15611 $ gnatkr grandparent-parent-child --> grparchi
15613 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
15614 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
15617 @node Preprocessing Using gnatprep
15618 @chapter Preprocessing Using @code{gnatprep}
15622 The @code{gnatprep} utility provides
15623 a simple preprocessing capability for Ada programs.
15624 It is designed for use with GNAT, but is not dependent on any special
15629 * Switches for gnatprep::
15630 * Form of Definitions File::
15631 * Form of Input Text for gnatprep::
15634 @node Using gnatprep
15635 @section Using @code{gnatprep}
15638 To call @code{gnatprep} use
15641 $ gnatprep [-bcrsu] [-Dsymbol=value] infile outfile [deffile]
15648 is the full name of the input file, which is an Ada source
15649 file containing preprocessor directives.
15652 is the full name of the output file, which is an Ada source
15653 in standard Ada form. When used with GNAT, this file name will
15654 normally have an ads or adb suffix.
15657 is the full name of a text file containing definitions of
15658 symbols to be referenced by the preprocessor. This argument is
15659 optional, and can be replaced by the use of the @option{-D} switch.
15662 is an optional sequence of switches as described in the next section.
15665 @node Switches for gnatprep
15666 @section Switches for @code{gnatprep}
15671 @item ^-b^/BLANK_LINES^
15672 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
15673 Causes both preprocessor lines and the lines deleted by
15674 preprocessing to be replaced by blank lines in the output source file,
15675 preserving line numbers in the output file.
15677 @item ^-c^/COMMENTS^
15678 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
15679 Causes both preprocessor lines and the lines deleted
15680 by preprocessing to be retained in the output source as comments marked
15681 with the special string @code{"--! "}. This option will result in line numbers
15682 being preserved in the output file.
15684 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
15685 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
15686 Defines a new symbol, associated with value. If no value is given on the
15687 command line, then symbol is considered to be @code{True}. This switch
15688 can be used in place of a definition file.
15692 @cindex @option{/REMOVE} (@command{gnatprep})
15693 This is the default setting which causes lines deleted by preprocessing
15694 to be entirely removed from the output file.
15697 @item ^-r^/REFERENCE^
15698 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
15699 Causes a @code{Source_Reference} pragma to be generated that
15700 references the original input file, so that error messages will use
15701 the file name of this original file. The use of this switch implies
15702 that preprocessor lines are not to be removed from the file, so its
15703 use will force @option{^-b^/BLANK_LINES^} mode if
15704 @option{^-c^/COMMENTS^}
15705 has not been specified explicitly.
15707 Note that if the file to be preprocessed contains multiple units, then
15708 it will be necessary to @code{gnatchop} the output file from
15709 @code{gnatprep}. If a @code{Source_Reference} pragma is present
15710 in the preprocessed file, it will be respected by
15711 @code{gnatchop ^-r^/REFERENCE^}
15712 so that the final chopped files will correctly refer to the original
15713 input source file for @code{gnatprep}.
15715 @item ^-s^/SYMBOLS^
15716 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
15717 Causes a sorted list of symbol names and values to be
15718 listed on the standard output file.
15720 @item ^-u^/UNDEFINED^
15721 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
15722 Causes undefined symbols to be treated as having the value FALSE in the context
15723 of a preprocessor test. In the absence of this option, an undefined symbol in
15724 a @code{#if} or @code{#elsif} test will be treated as an error.
15730 Note: if neither @option{-b} nor @option{-c} is present,
15731 then preprocessor lines and
15732 deleted lines are completely removed from the output, unless -r is
15733 specified, in which case -b is assumed.
15736 @node Form of Definitions File
15737 @section Form of Definitions File
15740 The definitions file contains lines of the form
15747 where symbol is an identifier, following normal Ada (case-insensitive)
15748 rules for its syntax, and value is one of the following:
15752 Empty, corresponding to a null substitution
15754 A string literal using normal Ada syntax
15756 Any sequence of characters from the set
15757 (letters, digits, period, underline).
15761 Comment lines may also appear in the definitions file, starting with
15762 the usual @code{--},
15763 and comments may be added to the definitions lines.
15765 @node Form of Input Text for gnatprep
15766 @section Form of Input Text for @code{gnatprep}
15769 The input text may contain preprocessor conditional inclusion lines,
15770 as well as general symbol substitution sequences.
15772 The preprocessor conditional inclusion commands have the form
15777 #if @i{expression} [then]
15779 #elsif @i{expression} [then]
15781 #elsif @i{expression} [then]
15792 In this example, @i{expression} is defined by the following grammar:
15794 @i{expression} ::= <symbol>
15795 @i{expression} ::= <symbol> = "<value>"
15796 @i{expression} ::= <symbol> = <symbol>
15797 @i{expression} ::= <symbol> 'Defined
15798 @i{expression} ::= not @i{expression}
15799 @i{expression} ::= @i{expression} and @i{expression}
15800 @i{expression} ::= @i{expression} or @i{expression}
15801 @i{expression} ::= @i{expression} and then @i{expression}
15802 @i{expression} ::= @i{expression} or else @i{expression}
15803 @i{expression} ::= ( @i{expression} )
15807 For the first test (@i{expression} ::= <symbol>) the symbol must have
15808 either the value true or false, that is to say the right-hand of the
15809 symbol definition must be one of the (case-insensitive) literals
15810 @code{True} or @code{False}. If the value is true, then the
15811 corresponding lines are included, and if the value is false, they are
15814 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
15815 the symbol has been defined in the definition file or by a @option{-D}
15816 switch on the command line. Otherwise, the test is false.
15818 The equality tests are case insensitive, as are all the preprocessor lines.
15820 If the symbol referenced is not defined in the symbol definitions file,
15821 then the effect depends on whether or not switch @option{-u}
15822 is specified. If so, then the symbol is treated as if it had the value
15823 false and the test fails. If this switch is not specified, then
15824 it is an error to reference an undefined symbol. It is also an error to
15825 reference a symbol that is defined with a value other than @code{True}
15828 The use of the @code{not} operator inverts the sense of this logical test, so
15829 that the lines are included only if the symbol is not defined.
15830 The @code{then} keyword is optional as shown
15832 The @code{#} must be the first non-blank character on a line, but
15833 otherwise the format is free form. Spaces or tabs may appear between
15834 the @code{#} and the keyword. The keywords and the symbols are case
15835 insensitive as in normal Ada code. Comments may be used on a
15836 preprocessor line, but other than that, no other tokens may appear on a
15837 preprocessor line. Any number of @code{elsif} clauses can be present,
15838 including none at all. The @code{else} is optional, as in Ada.
15840 The @code{#} marking the start of a preprocessor line must be the first
15841 non-blank character on the line, i.e. it must be preceded only by
15842 spaces or horizontal tabs.
15844 Symbol substitution outside of preprocessor lines is obtained by using
15852 anywhere within a source line, except in a comment or within a
15853 string literal. The identifier
15854 following the @code{$} must match one of the symbols defined in the symbol
15855 definition file, and the result is to substitute the value of the
15856 symbol in place of @code{$symbol} in the output file.
15858 Note that although the substitution of strings within a string literal
15859 is not possible, it is possible to have a symbol whose defined value is
15860 a string literal. So instead of setting XYZ to @code{hello} and writing:
15863 Header : String := "$XYZ";
15867 you should set XYZ to @code{"hello"} and write:
15870 Header : String := $XYZ;
15874 and then the substitution will occur as desired.
15877 @node The GNAT Run-Time Library Builder gnatlbr
15878 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
15880 @cindex Library builder
15883 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
15884 supplied configuration pragmas.
15887 * Running gnatlbr::
15888 * Switches for gnatlbr::
15889 * Examples of gnatlbr Usage::
15892 @node Running gnatlbr
15893 @section Running @code{gnatlbr}
15896 The @code{gnatlbr} command has the form
15899 $ GNAT LIBRARY /[CREATE | SET | DELETE]=directory [/CONFIG=file]
15902 @node Switches for gnatlbr
15903 @section Switches for @code{gnatlbr}
15906 @code{gnatlbr} recognizes the following switches:
15910 @item /CREATE=directory
15911 @cindex @code{/CREATE} (@code{gnatlbr})
15912 Create the new run-time library in the specified directory.
15914 @item /SET=directory
15915 @cindex @code{/SET} (@code{gnatlbr})
15916 Make the library in the specified directory the current run-time
15919 @item /DELETE=directory
15920 @cindex @code{/DELETE} (@code{gnatlbr})
15921 Delete the run-time library in the specified directory.
15924 @cindex @code{/CONFIG} (@code{gnatlbr})
15926 Use the configuration pragmas in the specified file when building
15930 Use the configuration pragmas in the specified file when compiling.
15934 @node Examples of gnatlbr Usage
15935 @section Example of @code{gnatlbr} Usage
15938 Contents of VAXFLOAT.ADC:
15939 pragma Float_Representation (VAX_Float);
15941 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
15943 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
15948 @node The GNAT Library Browser gnatls
15949 @chapter The GNAT Library Browser @code{gnatls}
15951 @cindex Library browser
15954 @code{gnatls} is a tool that outputs information about compiled
15955 units. It gives the relationship between objects, unit names and source
15956 files. It can also be used to check the source dependencies of a unit
15957 as well as various characteristics.
15961 * Switches for gnatls::
15962 * Examples of gnatls Usage::
15965 @node Running gnatls
15966 @section Running @code{gnatls}
15969 The @code{gnatls} command has the form
15972 $ gnatls switches @var{object_or_ali_file}
15976 The main argument is the list of object or @file{ali} files
15977 (@pxref{The Ada Library Information Files})
15978 for which information is requested.
15980 In normal mode, without additional option, @code{gnatls} produces a
15981 four-column listing. Each line represents information for a specific
15982 object. The first column gives the full path of the object, the second
15983 column gives the name of the principal unit in this object, the third
15984 column gives the status of the source and the fourth column gives the
15985 full path of the source representing this unit.
15986 Here is a simple example of use:
15990 ^./^[]^demo1.o demo1 DIF demo1.adb
15991 ^./^[]^demo2.o demo2 OK demo2.adb
15992 ^./^[]^hello.o h1 OK hello.adb
15993 ^./^[]^instr-child.o instr.child MOK instr-child.adb
15994 ^./^[]^instr.o instr OK instr.adb
15995 ^./^[]^tef.o tef DIF tef.adb
15996 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
15997 ^./^[]^tgef.o tgef DIF tgef.adb
16001 The first line can be interpreted as follows: the main unit which is
16003 object file @file{demo1.o} is demo1, whose main source is in
16004 @file{demo1.adb}. Furthermore, the version of the source used for the
16005 compilation of demo1 has been modified (DIF). Each source file has a status
16006 qualifier which can be:
16009 @item OK (unchanged)
16010 The version of the source file used for the compilation of the
16011 specified unit corresponds exactly to the actual source file.
16013 @item MOK (slightly modified)
16014 The version of the source file used for the compilation of the
16015 specified unit differs from the actual source file but not enough to
16016 require recompilation. If you use gnatmake with the qualifier
16017 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
16018 MOK will not be recompiled.
16020 @item DIF (modified)
16021 No version of the source found on the path corresponds to the source
16022 used to build this object.
16024 @item ??? (file not found)
16025 No source file was found for this unit.
16027 @item HID (hidden, unchanged version not first on PATH)
16028 The version of the source that corresponds exactly to the source used
16029 for compilation has been found on the path but it is hidden by another
16030 version of the same source that has been modified.
16034 @node Switches for gnatls
16035 @section Switches for @code{gnatls}
16038 @code{gnatls} recognizes the following switches:
16042 @item ^-a^/ALL_UNITS^
16043 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
16044 Consider all units, including those of the predefined Ada library.
16045 Especially useful with @option{^-d^/DEPENDENCIES^}.
16047 @item ^-d^/DEPENDENCIES^
16048 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
16049 List sources from which specified units depend on.
16051 @item ^-h^/OUTPUT=OPTIONS^
16052 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
16053 Output the list of options.
16055 @item ^-o^/OUTPUT=OBJECTS^
16056 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
16057 Only output information about object files.
16059 @item ^-s^/OUTPUT=SOURCES^
16060 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
16061 Only output information about source files.
16063 @item ^-u^/OUTPUT=UNITS^
16064 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
16065 Only output information about compilation units.
16067 @item ^-files^/FILES^=@var{file}
16068 @cindex @option{^-files^/FILES^} (@code{gnatls})
16069 Take as arguments the files listed in text file @var{file}.
16070 Text file @var{file} may contain empty lines that are ignored.
16071 Each non empty line should contain the name of an existing file.
16072 Several such switches may be specified simultaneously.
16074 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
16075 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
16076 @itemx ^-I^/SEARCH=^@var{dir}
16077 @itemx ^-I-^/NOCURRENT_DIRECTORY^
16079 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
16080 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
16081 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
16082 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
16083 Source path manipulation. Same meaning as the equivalent @code{gnatmake} flags
16084 (see @ref{Switches for gnatmake}).
16086 @item --RTS=@var{rts-path}
16087 @cindex @option{--RTS} (@code{gnatls})
16088 Specifies the default location of the runtime library. Same meaning as the
16089 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
16091 @item ^-v^/OUTPUT=VERBOSE^
16092 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
16093 Verbose mode. Output the complete source and object paths. Do not use
16094 the default column layout but instead use long format giving as much as
16095 information possible on each requested units, including special
16096 characteristics such as:
16099 @item Preelaborable
16100 The unit is preelaborable in the Ada 95 sense.
16103 No elaboration code has been produced by the compiler for this unit.
16106 The unit is pure in the Ada 95 sense.
16108 @item Elaborate_Body
16109 The unit contains a pragma Elaborate_Body.
16112 The unit contains a pragma Remote_Types.
16114 @item Shared_Passive
16115 The unit contains a pragma Shared_Passive.
16118 This unit is part of the predefined environment and cannot be modified
16121 @item Remote_Call_Interface
16122 The unit contains a pragma Remote_Call_Interface.
16128 @node Examples of gnatls Usage
16129 @section Example of @code{gnatls} Usage
16133 Example of using the verbose switch. Note how the source and
16134 object paths are affected by the -I switch.
16137 $ gnatls -v -I.. demo1.o
16139 GNATLS 3.10w (970212) Copyright 1999 Free Software Foundation, Inc.
16141 Source Search Path:
16142 <Current_Directory>
16144 /home/comar/local/adainclude/
16146 Object Search Path:
16147 <Current_Directory>
16149 /home/comar/local/lib/gcc-lib/mips-sni-sysv4/2.7.2/adalib/
16154 Kind => subprogram body
16155 Flags => No_Elab_Code
16156 Source => demo1.adb modified
16160 The following is an example of use of the dependency list.
16161 Note the use of the -s switch
16162 which gives a straight list of source files. This can be useful for
16163 building specialized scripts.
16166 $ gnatls -d demo2.o
16167 ./demo2.o demo2 OK demo2.adb
16173 $ gnatls -d -s -a demo1.o
16175 /home/comar/local/adainclude/ada.ads
16176 /home/comar/local/adainclude/a-finali.ads
16177 /home/comar/local/adainclude/a-filico.ads
16178 /home/comar/local/adainclude/a-stream.ads
16179 /home/comar/local/adainclude/a-tags.ads
16182 /home/comar/local/adainclude/gnat.ads
16183 /home/comar/local/adainclude/g-io.ads
16185 /home/comar/local/adainclude/system.ads
16186 /home/comar/local/adainclude/s-exctab.ads
16187 /home/comar/local/adainclude/s-finimp.ads
16188 /home/comar/local/adainclude/s-finroo.ads
16189 /home/comar/local/adainclude/s-secsta.ads
16190 /home/comar/local/adainclude/s-stalib.ads
16191 /home/comar/local/adainclude/s-stoele.ads
16192 /home/comar/local/adainclude/s-stratt.ads
16193 /home/comar/local/adainclude/s-tasoli.ads
16194 /home/comar/local/adainclude/s-unstyp.ads
16195 /home/comar/local/adainclude/unchconv.ads
16201 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
16203 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
16204 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
16205 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
16206 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
16207 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
16211 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
16212 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
16214 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
16215 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
16216 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
16217 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
16218 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
16219 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
16220 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
16221 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
16222 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
16223 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
16224 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
16228 @node Cleaning Up Using gnatclean
16229 @chapter Cleaning Up Using @code{gnatclean}
16231 @cindex Cleaning tool
16234 @code{gnatclean} is a tool that allows the deletion of files produced by the
16235 compiler, binder and linker, including ALI files, object files, tree files,
16236 expanded source files, library files, interface copy source files, binder
16237 generated files and executable files.
16240 * Running gnatclean::
16241 * Switches for gnatclean::
16242 * Examples of gnatclean Usage::
16245 @node Running gnatclean
16246 @section Running @code{gnatclean}
16249 The @code{gnatclean} command has the form:
16252 $ gnatclean switches @var{names}
16256 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
16257 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
16258 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
16261 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
16262 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
16263 the linker. In informative-only mode, specified by switch
16264 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
16265 normal mode is listed, but no file is actually deleted.
16267 @node Switches for gnatclean
16268 @section Switches for @code{gnatclean}
16271 @code{gnatclean} recognizes the following switches:
16275 @item ^-c^/COMPILER_FILES_ONLY^
16276 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
16277 Only attempt to delete the files produced by the compiler, not those produced
16278 by the binder or the linker. The files that are not to be deleted are library
16279 files, interface copy files, binder generated files and executable files.
16281 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
16282 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
16283 Indicate that ALI and object files should normally be found in directory
16286 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
16287 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
16288 When using project files, if some errors or warnings are detected during
16289 parsing and verbose mode is not in effect (no use of switch
16290 ^-v^/VERBOSE^), then error lines start with the full path name of the project
16291 file, rather than its simple file name.
16294 @cindex @option{^-h^/HELP^} (@code{gnatclean})
16295 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
16297 @item ^-n^/NODELETE^
16298 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
16299 Informative-only mode. Do not delete any files. Output the list of the files
16300 that would have been deleted if this switch was not specified.
16302 @item ^-P^/PROJECT_FILE=^@var{project}
16303 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
16304 Use project file @var{project}. Only one such switch can be used.
16305 When cleaning a project file, the files produced by the compilation of the
16306 immediate sources or inherited sources of the project files are to be
16307 deleted. This is not depending on the presence or not of executable names
16308 on the command line.
16311 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
16312 Quiet output. If there are no error, do not ouuput anything, except in
16313 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
16314 (switch ^-n^/NODELETE^).
16316 @item ^-r^/RECURSIVE^
16317 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
16318 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
16319 clean all imported and extended project files, recursively. If this switch
16320 is not specified, only the files related to the main project file are to be
16321 deleted. This switch has no effect if no project file is specified.
16323 @item ^-v^/VERBOSE^
16324 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
16327 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
16328 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
16329 Indicates the verbosity of the parsing of GNAT project files.
16330 See @ref{Switches Related to Project Files}.
16332 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
16333 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
16334 Indicates that external variable @var{name} has the value @var{value}.
16335 The Project Manager will use this value for occurrences of
16336 @code{external(name)} when parsing the project file.
16337 See @ref{Switches Related to Project Files}.
16339 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
16340 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
16341 When searching for ALI and object files, look in directory
16344 @item ^-I^/SEARCH=^@var{dir}
16345 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
16346 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
16348 @item ^-I-^/NOCURRENT_DIRECTORY^
16349 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
16350 @cindex Source files, suppressing search
16351 Do not look for ALI or object files in the directory
16352 where @code{gnatclean} was invoked.
16356 @node Examples of gnatclean Usage
16357 @section Examples of @code{gnatclean} Usage
16360 @node GNAT and Libraries
16361 @chapter GNAT and Libraries
16362 @cindex Library, building, installing, using
16365 This chapter describes how to build and use
16366 libraries with GNAT, and also shows how to recompile the GNAT run-time library.
16367 You should be familiar with the
16368 Project Manager facility (see @ref{GNAT Project Manager}) before reading this
16372 * Introduction to Libraries in GNAT::
16373 * General Ada Libraries::
16374 * Stand-alone Ada Libraries::
16375 * Rebuilding the GNAT Run-Time Library::
16378 @node Introduction to Libraries in GNAT
16379 @section Introduction to Libraries in GNAT
16382 A library is, conceptually, a collection of objects which does not have its
16383 own main thread of execution, but rather provides certain services to the
16384 applications that use it. A library can be either statically linked with the
16385 application, in which case its code is directly included in the application,
16386 or, on platforms that support it, be dynamically linked, in which case
16387 its code is shared by all applications making use of this library.
16389 GNAT supports both types of libraries.
16390 In the static case, the compiled code can be provided in different ways.
16391 The simplest approach is to provide directly the
16392 set of objects resulting from compilation of the library source files.
16393 Alternatively, you can group the objects into an archive using whatever
16394 commands are provided by the operating system. For the latter case,
16395 the objects are grouped into a shared library.
16397 In the GNAT environment, a library has two types of components:
16402 Compiled code and @file{ALI} files.
16403 See @ref{The Ada Library Information Files}.
16407 A GNAT library may either completely expose its source files to the
16408 compilation context of the user's application.
16409 Alternatively, it may expose
16410 a limited subset of its source files, called @emph{interface units},
16411 in which case the library is referred to as a @emph{stand-alone library}
16412 (see @ref{Stand-alone Ada Libraries}). In addition, GNAT fully supports
16413 foreign libraries, which are only available in the object format.
16415 All compilation units comprising
16416 an application are elaborated, in an order partially defined by Ada language
16418 Where possible, GNAT provides facilities
16419 to ensure that compilation units of a library are automatically elaborated;
16420 however, there are cases where this must be responsibility of a user. This will
16421 be addressed in greater detail below.
16423 @node General Ada Libraries
16424 @section General Ada Libraries
16427 * Building the library::
16428 * Installing the library::
16429 * Using the library::
16432 @node Building the library
16433 @subsection Building the library
16436 The easiest way to build a library is to use the Project Manager,
16437 which supports a special type of projects called Library Projects
16438 (see @ref{Library Projects}).
16440 A project is considered a library project, when two project-level attributes
16441 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
16442 control different aspects of library configuration, additional optional
16443 project-level attributes can be specified:
16446 This attribute controls whether the library is to be static or shared
16448 @item Library_Version
16449 This attribute specifies what is the library version; this value is used
16450 during dynamic linking of shared libraries to determine if the currently
16451 installed versions of the binaries are compatible.
16453 @item Library_Options
16455 These attributes specify additional low-level options to be used during
16456 library generation, and redefine the actual application used to generate
16461 The GNAT Project Manager takes full care of the library maintenance task,
16462 including recompilation of the source files for which objects do not exist
16463 or are not up to date, assembly of the library archive, and installation of
16464 the library, i.e. copying associated source, object and @file{ALI} files
16465 to the specified location.
16467 It is not entirely trivial to correctly perform all the steps required to
16468 produce a library. We recommend that you use the GNAT Project Manager
16469 for this task. In special cases where this is not desired, the necessary
16470 steps are discussed below.
16472 There are various possibilities for compiling the units that make up the
16473 library: for example with a Makefile (see @ref{Using the GNU make Utility})
16474 or with a conventional script.
16475 For simple libraries, it is also possible to create a
16476 dummy main program which depends upon all the packages that comprise the
16477 interface of the library. This dummy main program can then be given to
16478 @command{gnatmake}, which will ensure that all necessary objects are built.
16480 After this task is accomplished, you should follow the standard procedure
16481 of the underlying operating system to produce the static or shared library.
16483 Here is an example of such a dummy program:
16484 @smallexample @c ada
16486 with My_Lib.Service1;
16487 with My_Lib.Service2;
16488 with My_Lib.Service3;
16489 procedure My_Lib_Dummy is
16497 Here are the generic commands that will build an archive or a shared library.
16500 # compiling the library
16501 $ gnatmake -c my_lib_dummy.adb
16503 # we don't need the dummy object itself
16504 $ rm my_lib_dummy.o my_lib_dummy.ali
16506 # create an archive with the remaining objects
16507 $ ar rc libmy_lib.a *.o
16508 # some systems may require "ranlib" to be run as well
16510 # or create a shared library
16511 $ gcc -shared -o libmy_lib.so *.o
16512 # some systems may require the code to have been compiled with -fPIC
16514 # remove the object files that are now in the library
16517 # Make the ALI files read-only so that gnatmake will not try to
16518 # regenerate the objects that are in the library
16523 Please note that the library must have a name of the form @file{libxxx.a} or
16524 @file{libxxx.so} in order to be accessed by the directive @option{-lxxx}
16527 @node Installing the library
16528 @subsection Installing the library
16531 In the GNAT model, installing a library consists in copying into a specific
16532 location the files that make up this library. When the library is built using
16533 projects, it is automatically installed in the location specified in the
16534 project by means of the attribute @code{Library_Dir},
16535 otherwise the user must specify the destination.
16536 GNAT also supports installing the sources in a
16537 different directory from the other files (@file{ALI}, objects, archives)
16538 since the source path and the object path can be specified separately.
16540 The system administrator can place general purpose libraries in the default
16541 compiler paths, by specifying the libraries' location in the configuration
16542 files @file{ada_source_path} and @file{ada_object_path}.
16543 These configuration files must be located in the GNAT
16544 installation tree at the same place as the gcc spec file. The location of
16545 the gcc spec file can be determined as follows:
16551 The configuration files mentioned above have a simple format: each line
16552 must contain one unique directory name.
16553 Those names are added to the corresponding path
16554 in their order of appearance in the file. The names can be either absolute
16555 or relative; in the latter case, they are relative to where theses files
16558 The files @file{ada_source_path} and @file{ada_object_path} might not be
16560 GNAT installation, in which case, GNAT will look for its run-time library in
16561 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
16562 objects and @file{ALI} files). When the files exist, the compiler does not
16563 look in @file{adainclude} and @file{adalib}, and thus the
16564 @file{ada_source_path} file
16565 must contain the location for the GNAT run-time sources (which can simply
16566 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
16567 contain the location for the GNAT run-time objects (which can simply
16570 You can also specify a new default path to the run-time library at compilation
16571 time with the switch @option{--RTS=rts-path}. You can thus choose / change
16572 the run-time library you want your program to be compiled with. This switch is
16573 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
16574 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
16576 It is possible to install a library before or after the standard GNAT
16577 library, by reordering the lines in the configuration files. In general, a
16578 library must be installed before the GNAT library if it redefines
16582 @node Using the library
16583 @subsection Using the library
16586 Once again, the project facility greatly simplifies the addition of libraries
16587 to the compilation. If the project file for an application lists a library
16588 project in its @code{with} clause, the Project Manager will ensure that the
16589 library files are consistent, and that they are considered during the
16590 compilation and linking of the application.
16592 Even if you have a third-party, non-Ada library, you can still use GNAT's
16593 Project Manager facility to provide a wrapper for it. The following project for
16594 example, when @code{with}ed in your main project, will link with the
16595 third-party library @file{liba.a}:
16597 @smallexample @c projectfile
16600 for Source_Dirs use ();
16601 for Library_Dir use "lib";
16602 for Library_Name use "a";
16603 for Library_Kind use "static";
16609 In order to use an Ada library manually, you need to make sure that this
16610 library is on both your source and object path
16611 (see @ref{Search Paths and the Run-Time Library (RTL)},
16612 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
16613 in an archive or a shared library, you need to specify the desired
16614 library at link time.
16616 For example, you can use the library @file{mylib} installed in
16617 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
16620 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
16625 This can be expressed more simply:
16630 when the following conditions are met:
16633 @file{/dir/my_lib_src} has been added by the user to the environment
16634 variable @code{ADA_INCLUDE_PATH}, or by the administrator to the file
16635 @file{ada_source_path}
16637 @file{/dir/my_lib_obj} has been added by the user to the environment
16638 variable @code{ADA_OBJECTS_PATH}, or by the administrator to the file
16639 @file{ada_object_path}
16641 a pragma @code{Linker_Options} has been added to one of the sources.
16644 @smallexample @c ada
16645 pragma Linker_Options ("-lmy_lib");
16650 @node Stand-alone Ada Libraries
16651 @section Stand-alone Ada Libraries
16652 @cindex Stand-alone library, building, using
16655 * Introduction to Stand-alone Libraries::
16656 * Building a Stand-alone Library::
16657 * Creating a Stand-alone Library to be used in a non-Ada context::
16658 * Restrictions in Stand-alone Libraries::
16661 @node Introduction to Stand-alone Libraries
16662 @subsection Introduction to Stand-alone Libraries
16665 A Stand-alone Library (SAL) is a library that contains the necessary code to
16666 elaborate the Ada units that are included in the library. In contrast with
16667 an ordinary library, which consists of all sources, objects and @file{ALI}
16669 library, a SAL may specify a restricted subset of compilation units
16670 to serve as a library interface. In this case, the fully
16671 self-sufficient set of files will normally consist of an objects
16672 archive, the sources of interface units' specs, and the @file{ALI}
16673 files of interface units.
16674 If an interface spec contains a generic unit or an inlined subprogram,
16676 source must also be provided; if the units that must be provided in the source
16677 form depend on other units, the source and @file{ALI} files of those must
16680 The main purpose of a SAL is to minimize the recompilation overhead of client
16681 applications when a new version of the library is installed. Specifically,
16682 if the interface sources have not changed, client applications do not need to
16683 be recompiled. If, furthermore, a SAL is provided in the shared form and its
16684 version, controlled by @code{Library_Version} attribute, is not changed,
16685 then the clients do not need to be relinked.
16687 SALs also allow the library providers to minimize the amount of library source
16688 text exposed to the clients. Such ``information hiding'' might be useful or
16689 necessary for various reasons.
16691 Stand-alone libraries are also well suited to be used in an executable whose
16692 main routine is not written in Ada.
16694 @node Building a Stand-alone Library
16695 @subsection Building a Stand-alone Library
16698 GNAT's Project facility provides a simple way of building and installing
16699 stand-alone libraries; see @ref{Stand-alone Library Projects}.
16700 To be a Stand-alone Library Project, in addition to the two attributes
16701 that make a project a Library Project (@code{Library_Name} and
16702 @code{Library_Dir}; see @ref{Library Projects}), the attribute
16703 @code{Library_Interface} must be defined. For example:
16705 @smallexample @c projectfile
16707 for Library_Dir use "lib_dir";
16708 for Library_Name use "dummy";
16709 for Library_Interface use ("int1", "int1.child");
16714 Attribute @code{Library_Interface} has a non empty string list value,
16715 each string in the list designating a unit contained in an immediate source
16716 of the project file.
16718 When a Stand-alone Library is built, first the binder is invoked to build
16719 a package whose name depends on the library name
16720 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
16721 This binder-generated package includes initialization and
16722 finalization procedures whose
16723 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
16725 above). The object corresponding to this package is included in the library.
16727 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
16728 calling of these procedures if a static SAL is built, or if a shared SAL
16730 with the project-level attribute @code{Library_Auto_Init} set to
16733 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
16734 (those that are listed in attribute @code{Library_Interface}) are copied to
16735 the Library Directory. As a consequence, only the Interface Units may be
16736 imported from Ada units outside of the library. If other units are imported,
16737 the binding phase will fail.
16739 The attribute @code{Library_Src_Dir} may be specified for a
16740 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
16741 single string value. Its value must be the path (absolute or relative to the
16742 project directory) of an existing directory. This directory cannot be the
16743 object directory or one of the source directories, but it can be the same as
16744 the library directory. The sources of the Interface
16745 Units of the library that are needed by an Ada client of the library will be
16746 copied to the designated directory, called the Interface Copy directory.
16747 These sources includes the specs of the Interface Units, but they may also
16748 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
16749 are used, or when there is a generic unit in the spec. Before the sources
16750 are copied to the Interface Copy directory, an attempt is made to delete all
16751 files in the Interface Copy directory.
16753 Building stand-alone libraries by hand is somewhat tedious, but for those
16754 occasions when it is necessary here are the steps that you need to perform:
16757 Compile all library sources.
16760 Invoke the binder with the switch @option{-n} (No Ada main program),
16761 with all the @file{ALI} files of the interfaces, and
16762 with the switch @option{-L} to give specific names to the @code{init}
16763 and @code{final} procedures. For example:
16765 gnatbind -n int1.ali int2.ali -Lsal1
16769 Compile the binder generated file:
16775 Link the dynamic library with all the necessary object files,
16776 indicating to the linker the names of the @code{init} (and possibly
16777 @code{final}) procedures for automatic initialization (and finalization).
16778 The built library should be placed in a directory different from
16779 the object directory.
16782 Copy the @code{ALI} files of the interface to the library directory,
16783 add in this copy an indication that it is an interface to a SAL
16784 (i.e. add a word @option{SL} on the line in the @file{ALI} file that starts
16785 with letter ``P'') and make the modified copy of the @file{ALI} file
16790 Using SALs is not different from using other libraries
16791 (see @ref{Using the library}).
16793 @node Creating a Stand-alone Library to be used in a non-Ada context
16794 @subsection Creating a Stand-alone Library to be used in a non-Ada context
16797 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
16800 The only extra step required is to ensure that library interface subprograms
16801 are compatible with the main program, by means of @code{pragma Export}
16802 or @code{pragma Convention}.
16804 Here is an example of simple library interface for use with C main program:
16806 @smallexample @c ada
16807 package Interface is
16809 procedure Do_Something;
16810 pragma Export (C, Do_Something, "do_something");
16812 procedure Do_Something_Else;
16813 pragma Export (C, Do_Something_Else, "do_something_else");
16819 On the foreign language side, you must provide a ``foreign'' view of the
16820 library interface; remember that it should contain elaboration routines in
16821 addition to interface subprograms.
16823 The example below shows the content of @code{mylib_interface.h} (note
16824 that there is no rule for the naming of this file, any name can be used)
16826 /* the library elaboration procedure */
16827 extern void mylibinit (void);
16829 /* the library finalization procedure */
16830 extern void mylibfinal (void);
16832 /* the interface exported by the library */
16833 extern void do_something (void);
16834 extern void do_something_else (void);
16838 Libraries built as explained above can be used from any program, provided
16839 that the elaboration procedures (named @code{mylibinit} in the previous
16840 example) are called before the library services are used. Any number of
16841 libraries can be used simultaneously, as long as the elaboration
16842 procedure of each library is called.
16844 Below is an example of C program that uses the @code{mylib} library.
16847 #include "mylib_interface.h"
16852 /* First, elaborate the library before using it */
16855 /* Main program, using the library exported entities */
16857 do_something_else ();
16859 /* Library finalization at the end of the program */
16866 Note that invoking any library finalization procedure generated by
16867 @code{gnatbind} shuts down the Ada run-time environment.
16869 finalization of all Ada libraries must be performed at the end of the program.
16870 No call to these libraries nor to the Ada run-time library should be made
16871 after the finalization phase.
16873 @node Restrictions in Stand-alone Libraries
16874 @subsection Restrictions in Stand-alone Libraries
16877 The pragmas listed below should be used with caution inside libraries,
16878 as they can create incompatibilities with other Ada libraries:
16880 @item pragma @code{Locking_Policy}
16881 @item pragma @code{Queuing_Policy}
16882 @item pragma @code{Task_Dispatching_Policy}
16883 @item pragma @code{Unreserve_All_Interrupts}
16887 When using a library that contains such pragmas, the user must make sure
16888 that all libraries use the same pragmas with the same values. Otherwise,
16889 @code{Program_Error} will
16890 be raised during the elaboration of the conflicting
16891 libraries. The usage of these pragmas and its consequences for the user
16892 should therefore be well documented.
16894 Similarly, the traceback in the exception occurrence mechanism should be
16895 enabled or disabled in a consistent manner across all libraries.
16896 Otherwise, Program_Error will be raised during the elaboration of the
16897 conflicting libraries.
16899 If the @code{Version} or @code{Body_Version}
16900 attributes are used inside a library, then you need to
16901 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
16902 libraries, so that version identifiers can be properly computed.
16903 In practice these attributes are rarely used, so this is unlikely
16904 to be a consideration.
16906 @node Rebuilding the GNAT Run-Time Library
16907 @section Rebuilding the GNAT Run-Time Library
16908 @cindex GNAT Run-Time Library, rebuilding
16911 It may be useful to recompile the GNAT library in various contexts, the
16912 most important one being the use of partition-wide configuration pragmas
16913 such as @code{Normalize_Scalars}. A special Makefile called
16914 @code{Makefile.adalib} is provided to that effect and can be found in
16915 the directory containing the GNAT library. The location of this
16916 directory depends on the way the GNAT environment has been installed and can
16917 be determined by means of the command:
16924 The last entry in the object search path usually contains the
16925 gnat library. This Makefile contains its own documentation and in
16926 particular the set of instructions needed to rebuild a new library and
16930 @node Using the GNU make Utility
16931 @chapter Using the GNU @code{make} Utility
16935 This chapter offers some examples of makefiles that solve specific
16936 problems. It does not explain how to write a makefile (see the GNU make
16937 documentation), nor does it try to replace the @code{gnatmake} utility
16938 (@pxref{The GNAT Make Program gnatmake}).
16940 All the examples in this section are specific to the GNU version of
16941 make. Although @code{make} is a standard utility, and the basic language
16942 is the same, these examples use some advanced features found only in
16946 * Using gnatmake in a Makefile::
16947 * Automatically Creating a List of Directories::
16948 * Generating the Command Line Switches::
16949 * Overcoming Command Line Length Limits::
16952 @node Using gnatmake in a Makefile
16953 @section Using gnatmake in a Makefile
16958 Complex project organizations can be handled in a very powerful way by
16959 using GNU make combined with gnatmake. For instance, here is a Makefile
16960 which allows you to build each subsystem of a big project into a separate
16961 shared library. Such a makefile allows you to significantly reduce the link
16962 time of very big applications while maintaining full coherence at
16963 each step of the build process.
16965 The list of dependencies are handled automatically by
16966 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
16967 the appropriate directories.
16969 Note that you should also read the example on how to automatically
16970 create the list of directories
16971 (@pxref{Automatically Creating a List of Directories})
16972 which might help you in case your project has a lot of subdirectories.
16977 @font@heightrm=cmr8
16980 ## This Makefile is intended to be used with the following directory
16982 ## - The sources are split into a series of csc (computer software components)
16983 ## Each of these csc is put in its own directory.
16984 ## Their name are referenced by the directory names.
16985 ## They will be compiled into shared library (although this would also work
16986 ## with static libraries
16987 ## - The main program (and possibly other packages that do not belong to any
16988 ## csc is put in the top level directory (where the Makefile is).
16989 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
16990 ## \_ second_csc (sources) __ lib (will contain the library)
16992 ## Although this Makefile is build for shared library, it is easy to modify
16993 ## to build partial link objects instead (modify the lines with -shared and
16996 ## With this makefile, you can change any file in the system or add any new
16997 ## file, and everything will be recompiled correctly (only the relevant shared
16998 ## objects will be recompiled, and the main program will be re-linked).
17000 # The list of computer software component for your project. This might be
17001 # generated automatically.
17004 # Name of the main program (no extension)
17007 # If we need to build objects with -fPIC, uncomment the following line
17010 # The following variable should give the directory containing libgnat.so
17011 # You can get this directory through 'gnatls -v'. This is usually the last
17012 # directory in the Object_Path.
17015 # The directories for the libraries
17016 # (This macro expands the list of CSC to the list of shared libraries, you
17017 # could simply use the expanded form :
17018 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
17019 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
17021 $@{MAIN@}: objects $@{LIB_DIR@}
17022 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
17023 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
17026 # recompile the sources
17027 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
17029 # Note: In a future version of GNAT, the following commands will be simplified
17030 # by a new tool, gnatmlib
17032 mkdir -p $@{dir $@@ @}
17033 cd $@{dir $@@ @}; gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
17034 cd $@{dir $@@ @}; cp -f ../*.ali .
17036 # The dependencies for the modules
17037 # Note that we have to force the expansion of *.o, since in some cases
17038 # make won't be able to do it itself.
17039 aa/lib/libaa.so: $@{wildcard aa/*.o@}
17040 bb/lib/libbb.so: $@{wildcard bb/*.o@}
17041 cc/lib/libcc.so: $@{wildcard cc/*.o@}
17043 # Make sure all of the shared libraries are in the path before starting the
17046 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
17049 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
17050 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
17051 $@{RM@} $@{CSC_LIST:%=%/*.o@}
17052 $@{RM@} *.o *.ali $@{MAIN@}
17055 @node Automatically Creating a List of Directories
17056 @section Automatically Creating a List of Directories
17059 In most makefiles, you will have to specify a list of directories, and
17060 store it in a variable. For small projects, it is often easier to
17061 specify each of them by hand, since you then have full control over what
17062 is the proper order for these directories, which ones should be
17065 However, in larger projects, which might involve hundreds of
17066 subdirectories, it might be more convenient to generate this list
17069 The example below presents two methods. The first one, although less
17070 general, gives you more control over the list. It involves wildcard
17071 characters, that are automatically expanded by @code{make}. Its
17072 shortcoming is that you need to explicitly specify some of the
17073 organization of your project, such as for instance the directory tree
17074 depth, whether some directories are found in a separate tree,...
17076 The second method is the most general one. It requires an external
17077 program, called @code{find}, which is standard on all Unix systems. All
17078 the directories found under a given root directory will be added to the
17084 @font@heightrm=cmr8
17087 # The examples below are based on the following directory hierarchy:
17088 # All the directories can contain any number of files
17089 # ROOT_DIRECTORY -> a -> aa -> aaa
17092 # -> b -> ba -> baa
17095 # This Makefile creates a variable called DIRS, that can be reused any time
17096 # you need this list (see the other examples in this section)
17098 # The root of your project's directory hierarchy
17102 # First method: specify explicitly the list of directories
17103 # This allows you to specify any subset of all the directories you need.
17106 DIRS := a/aa/ a/ab/ b/ba/
17109 # Second method: use wildcards
17110 # Note that the argument(s) to wildcard below should end with a '/'.
17111 # Since wildcards also return file names, we have to filter them out
17112 # to avoid duplicate directory names.
17113 # We thus use make's @code{dir} and @code{sort} functions.
17114 # It sets DIRs to the following value (note that the directories aaa and baa
17115 # are not given, unless you change the arguments to wildcard).
17116 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
17119 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
17120 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
17123 # Third method: use an external program
17124 # This command is much faster if run on local disks, avoiding NFS slowdowns.
17125 # This is the most complete command: it sets DIRs to the following value:
17126 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
17129 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
17133 @node Generating the Command Line Switches
17134 @section Generating the Command Line Switches
17137 Once you have created the list of directories as explained in the
17138 previous section (@pxref{Automatically Creating a List of Directories}),
17139 you can easily generate the command line arguments to pass to gnatmake.
17141 For the sake of completeness, this example assumes that the source path
17142 is not the same as the object path, and that you have two separate lists
17146 # see "Automatically creating a list of directories" to create
17151 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
17152 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
17155 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
17158 @node Overcoming Command Line Length Limits
17159 @section Overcoming Command Line Length Limits
17162 One problem that might be encountered on big projects is that many
17163 operating systems limit the length of the command line. It is thus hard to give
17164 gnatmake the list of source and object directories.
17166 This example shows how you can set up environment variables, which will
17167 make @code{gnatmake} behave exactly as if the directories had been
17168 specified on the command line, but have a much higher length limit (or
17169 even none on most systems).
17171 It assumes that you have created a list of directories in your Makefile,
17172 using one of the methods presented in
17173 @ref{Automatically Creating a List of Directories}.
17174 For the sake of completeness, we assume that the object
17175 path (where the ALI files are found) is different from the sources patch.
17177 Note a small trick in the Makefile below: for efficiency reasons, we
17178 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
17179 expanded immediately by @code{make}. This way we overcome the standard
17180 make behavior which is to expand the variables only when they are
17183 On Windows, if you are using the standard Windows command shell, you must
17184 replace colons with semicolons in the assignments to these variables.
17189 @font@heightrm=cmr8
17192 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
17193 # This is the same thing as putting the -I arguments on the command line.
17194 # (the equivalent of using -aI on the command line would be to define
17195 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
17196 # You can of course have different values for these variables.
17198 # Note also that we need to keep the previous values of these variables, since
17199 # they might have been set before running 'make' to specify where the GNAT
17200 # library is installed.
17202 # see "Automatically creating a list of directories" to create these
17208 space:=$@{empty@} $@{empty@}
17209 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
17210 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
17211 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
17212 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
17213 export ADA_INCLUDE_PATH
17214 export ADA_OBJECT_PATH
17222 @node Finding Memory Problems
17223 @chapter Finding Memory Problems
17226 This chapter describes
17228 the @command{gnatmem} tool, which can be used to track down
17229 ``memory leaks'', and
17231 the GNAT Debug Pool facility, which can be used to detect incorrect uses of
17232 access values (including ``dangling references'').
17236 * The gnatmem Tool::
17238 * The GNAT Debug Pool Facility::
17243 @node The gnatmem Tool
17244 @section The @command{gnatmem} Tool
17248 The @code{gnatmem} utility monitors dynamic allocation and
17249 deallocation activity in a program, and displays information about
17250 incorrect deallocations and possible sources of memory leaks.
17251 It provides three type of information:
17254 General information concerning memory management, such as the total
17255 number of allocations and deallocations, the amount of allocated
17256 memory and the high water mark, i.e. the largest amount of allocated
17257 memory in the course of program execution.
17260 Backtraces for all incorrect deallocations, that is to say deallocations
17261 which do not correspond to a valid allocation.
17264 Information on each allocation that is potentially the origin of a memory
17269 * Running gnatmem::
17270 * Switches for gnatmem::
17271 * Example of gnatmem Usage::
17274 @node Running gnatmem
17275 @subsection Running @code{gnatmem}
17278 @code{gnatmem} makes use of the output created by the special version of
17279 allocation and deallocation routines that record call information. This
17280 allows to obtain accurate dynamic memory usage history at a minimal cost to
17281 the execution speed. Note however, that @code{gnatmem} is not supported on
17282 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux x86,
17283 Solaris (sparc and x86) and Windows NT/2000/XP (x86).
17286 The @code{gnatmem} command has the form
17289 $ gnatmem [switches] user_program
17293 The program must have been linked with the instrumented version of the
17294 allocation and deallocation routines. This is done by linking with the
17295 @file{libgmem.a} library. For correct symbolic backtrace information,
17296 the user program should be compiled with debugging options
17297 @ref{Switches for gcc}. For example to build @file{my_program}:
17300 $ gnatmake -g my_program -largs -lgmem
17304 When running @file{my_program} the file @file{gmem.out} is produced. This file
17305 contains information about all allocations and deallocations done by the
17306 program. It is produced by the instrumented allocations and
17307 deallocations routines and will be used by @code{gnatmem}.
17310 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
17311 examine. If the location of @file{gmem.out} file was not explicitly supplied by
17312 @code{-i} switch, gnatmem will assume that this file can be found in the
17313 current directory. For example, after you have executed @file{my_program},
17314 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
17317 $ gnatmem my_program
17321 This will produce the output with the following format:
17323 *************** debut cc
17325 $ gnatmem my_program
17329 Total number of allocations : 45
17330 Total number of deallocations : 6
17331 Final Water Mark (non freed mem) : 11.29 Kilobytes
17332 High Water Mark : 11.40 Kilobytes
17337 Allocation Root # 2
17338 -------------------
17339 Number of non freed allocations : 11
17340 Final Water Mark (non freed mem) : 1.16 Kilobytes
17341 High Water Mark : 1.27 Kilobytes
17343 my_program.adb:23 my_program.alloc
17349 The first block of output gives general information. In this case, the
17350 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
17351 Unchecked_Deallocation routine occurred.
17354 Subsequent paragraphs display information on all allocation roots.
17355 An allocation root is a specific point in the execution of the program
17356 that generates some dynamic allocation, such as a ``@code{@b{new}}''
17357 construct. This root is represented by an execution backtrace (or subprogram
17358 call stack). By default the backtrace depth for allocations roots is 1, so
17359 that a root corresponds exactly to a source location. The backtrace can
17360 be made deeper, to make the root more specific.
17362 @node Switches for gnatmem
17363 @subsection Switches for @code{gnatmem}
17366 @code{gnatmem} recognizes the following switches:
17371 @cindex @option{-q} (@code{gnatmem})
17372 Quiet. Gives the minimum output needed to identify the origin of the
17373 memory leaks. Omits statistical information.
17376 @cindex @var{N} (@code{gnatmem})
17377 N is an integer literal (usually between 1 and 10) which controls the
17378 depth of the backtraces defining allocation root. The default value for
17379 N is 1. The deeper the backtrace, the more precise the localization of
17380 the root. Note that the total number of roots can depend on this
17381 parameter. This parameter must be specified @emph{before} the name of the
17382 executable to be analyzed, to avoid ambiguity.
17385 @cindex @option{-b} (@code{gnatmem})
17386 This switch has the same effect as just depth parameter.
17388 @item -i @var{file}
17389 @cindex @option{-i} (@code{gnatmem})
17390 Do the @code{gnatmem} processing starting from @file{file}, rather than
17391 @file{gmem.out} in the current directory.
17394 @cindex @option{-m} (@code{gnatmem})
17395 This switch causes @code{gnatmem} to mask the allocation roots that have less
17396 than n leaks. The default value is 1. Specifying the value of 0 will allow to
17397 examine even the roots that didn't result in leaks.
17400 @cindex @option{-s} (@code{gnatmem})
17401 This switch causes @code{gnatmem} to sort the allocation roots according to the
17402 specified order of sort criteria, each identified by a single letter. The
17403 currently supported criteria are @code{n, h, w} standing respectively for
17404 number of unfreed allocations, high watermark, and final watermark
17405 corresponding to a specific root. The default order is @code{nwh}.
17409 @node Example of gnatmem Usage
17410 @subsection Example of @code{gnatmem} Usage
17413 The following example shows the use of @code{gnatmem}
17414 on a simple memory-leaking program.
17415 Suppose that we have the following Ada program:
17417 @smallexample @c ada
17420 with Unchecked_Deallocation;
17421 procedure Test_Gm is
17423 type T is array (1..1000) of Integer;
17424 type Ptr is access T;
17425 procedure Free is new Unchecked_Deallocation (T, Ptr);
17428 procedure My_Alloc is
17433 procedure My_DeAlloc is
17441 for I in 1 .. 5 loop
17442 for J in I .. 5 loop
17453 The program needs to be compiled with debugging option and linked with
17454 @code{gmem} library:
17457 $ gnatmake -g test_gm -largs -lgmem
17461 Then we execute the program as usual:
17468 Then @code{gnatmem} is invoked simply with
17474 which produces the following output (result may vary on different platforms):
17479 Total number of allocations : 18
17480 Total number of deallocations : 5
17481 Final Water Mark (non freed mem) : 53.00 Kilobytes
17482 High Water Mark : 56.90 Kilobytes
17484 Allocation Root # 1
17485 -------------------
17486 Number of non freed allocations : 11
17487 Final Water Mark (non freed mem) : 42.97 Kilobytes
17488 High Water Mark : 46.88 Kilobytes
17490 test_gm.adb:11 test_gm.my_alloc
17492 Allocation Root # 2
17493 -------------------
17494 Number of non freed allocations : 1
17495 Final Water Mark (non freed mem) : 10.02 Kilobytes
17496 High Water Mark : 10.02 Kilobytes
17498 s-secsta.adb:81 system.secondary_stack.ss_init
17500 Allocation Root # 3
17501 -------------------
17502 Number of non freed allocations : 1
17503 Final Water Mark (non freed mem) : 12 Bytes
17504 High Water Mark : 12 Bytes
17506 s-secsta.adb:181 system.secondary_stack.ss_init
17510 Note that the GNAT run time contains itself a certain number of
17511 allocations that have no corresponding deallocation,
17512 as shown here for root #2 and root
17513 #3. This is a normal behavior when the number of non freed allocations
17514 is one, it allocates dynamic data structures that the run time needs for
17515 the complete lifetime of the program. Note also that there is only one
17516 allocation root in the user program with a single line back trace:
17517 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
17518 program shows that 'My_Alloc' is called at 2 different points in the
17519 source (line 21 and line 24). If those two allocation roots need to be
17520 distinguished, the backtrace depth parameter can be used:
17523 $ gnatmem 3 test_gm
17527 which will give the following output:
17532 Total number of allocations : 18
17533 Total number of deallocations : 5
17534 Final Water Mark (non freed mem) : 53.00 Kilobytes
17535 High Water Mark : 56.90 Kilobytes
17537 Allocation Root # 1
17538 -------------------
17539 Number of non freed allocations : 10
17540 Final Water Mark (non freed mem) : 39.06 Kilobytes
17541 High Water Mark : 42.97 Kilobytes
17543 test_gm.adb:11 test_gm.my_alloc
17544 test_gm.adb:24 test_gm
17545 b_test_gm.c:52 main
17547 Allocation Root # 2
17548 -------------------
17549 Number of non freed allocations : 1
17550 Final Water Mark (non freed mem) : 10.02 Kilobytes
17551 High Water Mark : 10.02 Kilobytes
17553 s-secsta.adb:81 system.secondary_stack.ss_init
17554 s-secsta.adb:283 <system__secondary_stack___elabb>
17555 b_test_gm.c:33 adainit
17557 Allocation Root # 3
17558 -------------------
17559 Number of non freed allocations : 1
17560 Final Water Mark (non freed mem) : 3.91 Kilobytes
17561 High Water Mark : 3.91 Kilobytes
17563 test_gm.adb:11 test_gm.my_alloc
17564 test_gm.adb:21 test_gm
17565 b_test_gm.c:52 main
17567 Allocation Root # 4
17568 -------------------
17569 Number of non freed allocations : 1
17570 Final Water Mark (non freed mem) : 12 Bytes
17571 High Water Mark : 12 Bytes
17573 s-secsta.adb:181 system.secondary_stack.ss_init
17574 s-secsta.adb:283 <system__secondary_stack___elabb>
17575 b_test_gm.c:33 adainit
17579 The allocation root #1 of the first example has been split in 2 roots #1
17580 and #3 thanks to the more precise associated backtrace.
17585 @node The GNAT Debug Pool Facility
17586 @section The GNAT Debug Pool Facility
17588 @cindex storage, pool, memory corruption
17591 The use of unchecked deallocation and unchecked conversion can easily
17592 lead to incorrect memory references. The problems generated by such
17593 references are usually difficult to tackle because the symptoms can be
17594 very remote from the origin of the problem. In such cases, it is
17595 very helpful to detect the problem as early as possible. This is the
17596 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
17598 In order to use the GNAT specific debugging pool, the user must
17599 associate a debug pool object with each of the access types that may be
17600 related to suspected memory problems. See Ada Reference Manual 13.11.
17601 @smallexample @c ada
17602 type Ptr is access Some_Type;
17603 Pool : GNAT.Debug_Pools.Debug_Pool;
17604 for Ptr'Storage_Pool use Pool;
17608 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
17609 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
17610 allow the user to redefine allocation and deallocation strategies. They
17611 also provide a checkpoint for each dereference, through the use of
17612 the primitive operation @code{Dereference} which is implicitly called at
17613 each dereference of an access value.
17615 Once an access type has been associated with a debug pool, operations on
17616 values of the type may raise four distinct exceptions,
17617 which correspond to four potential kinds of memory corruption:
17620 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
17622 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
17624 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
17626 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
17630 For types associated with a Debug_Pool, dynamic allocation is performed using
17632 GNAT allocation routine. References to all allocated chunks of memory
17633 are kept in an internal dictionary.
17634 Several deallocation strategies are provided, whereupon the user can choose
17635 to release the memory to the system, keep it allocated for further invalid
17636 access checks, or fill it with an easily recognizable pattern for debug
17638 The memory pattern is the old IBM hexadecimal convention: @code{16#DEADBEEF#}.
17640 See the documentation in the file g-debpoo.ads for more information on the
17641 various strategies.
17643 Upon each dereference, a check is made that the access value denotes a
17644 properly allocated memory location. Here is a complete example of use of
17645 @code{Debug_Pools}, that includes typical instances of memory corruption:
17646 @smallexample @c ada
17650 with Gnat.Io; use Gnat.Io;
17651 with Unchecked_Deallocation;
17652 with Unchecked_Conversion;
17653 with GNAT.Debug_Pools;
17654 with System.Storage_Elements;
17655 with Ada.Exceptions; use Ada.Exceptions;
17656 procedure Debug_Pool_Test is
17658 type T is access Integer;
17659 type U is access all T;
17661 P : GNAT.Debug_Pools.Debug_Pool;
17662 for T'Storage_Pool use P;
17664 procedure Free is new Unchecked_Deallocation (Integer, T);
17665 function UC is new Unchecked_Conversion (U, T);
17668 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
17678 Put_Line (Integer'Image(B.all));
17680 when E : others => Put_Line ("raised: " & Exception_Name (E));
17685 when E : others => Put_Line ("raised: " & Exception_Name (E));
17689 Put_Line (Integer'Image(B.all));
17691 when E : others => Put_Line ("raised: " & Exception_Name (E));
17696 when E : others => Put_Line ("raised: " & Exception_Name (E));
17699 end Debug_Pool_Test;
17703 The debug pool mechanism provides the following precise diagnostics on the
17704 execution of this erroneous program:
17707 Total allocated bytes : 0
17708 Total deallocated bytes : 0
17709 Current Water Mark: 0
17713 Total allocated bytes : 8
17714 Total deallocated bytes : 0
17715 Current Water Mark: 8
17718 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
17719 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
17720 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
17721 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
17723 Total allocated bytes : 8
17724 Total deallocated bytes : 4
17725 Current Water Mark: 4
17730 @node Creating Sample Bodies Using gnatstub
17731 @chapter Creating Sample Bodies Using @command{gnatstub}
17735 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
17736 for library unit declarations.
17738 To create a body stub, @command{gnatstub} has to compile the library
17739 unit declaration. Therefore, bodies can be created only for legal
17740 library units. Moreover, if a library unit depends semantically upon
17741 units located outside the current directory, you have to provide
17742 the source search path when calling @command{gnatstub}, see the description
17743 of @command{gnatstub} switches below.
17746 * Running gnatstub::
17747 * Switches for gnatstub::
17750 @node Running gnatstub
17751 @section Running @command{gnatstub}
17754 @command{gnatstub} has the command-line interface of the form
17757 $ gnatstub [switches] filename [directory]
17764 is the name of the source file that contains a library unit declaration
17765 for which a body must be created. The file name may contain the path
17767 The file name does not have to follow the GNAT file name conventions. If the
17769 does not follow GNAT file naming conventions, the name of the body file must
17771 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
17772 If the file name follows the GNAT file naming
17773 conventions and the name of the body file is not provided,
17776 of the body file from the argument file name by replacing the @file{.ads}
17778 with the @file{.adb} suffix.
17781 indicates the directory in which the body stub is to be placed (the default
17786 is an optional sequence of switches as described in the next section
17789 @node Switches for gnatstub
17790 @section Switches for @command{gnatstub}
17796 @cindex @option{^-f^/FULL^} (@command{gnatstub})
17797 If the destination directory already contains a file with the name of the
17799 for the argument spec file, replace it with the generated body stub.
17801 @item ^-hs^/HEADER=SPEC^
17802 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
17803 Put the comment header (i.e., all the comments preceding the
17804 compilation unit) from the source of the library unit declaration
17805 into the body stub.
17807 @item ^-hg^/HEADER=GENERAL^
17808 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
17809 Put a sample comment header into the body stub.
17813 @cindex @option{-IDIR} (@command{gnatstub})
17815 @cindex @option{-I-} (@command{gnatstub})
17818 @item /NOCURRENT_DIRECTORY
17819 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
17821 ^These switches have ^This switch has^ the same meaning as in calls to
17823 ^They define ^It defines ^ the source search path in the call to
17824 @command{gcc} issued
17825 by @command{gnatstub} to compile an argument source file.
17827 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
17828 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
17829 This switch has the same meaning as in calls to @command{gcc}.
17830 It defines the additional configuration file to be passed to the call to
17831 @command{gcc} issued
17832 by @command{gnatstub} to compile an argument source file.
17834 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
17835 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
17836 (@var{n} is a non-negative integer). Set the maximum line length in the
17837 body stub to @var{n}; the default is 79. The maximum value that can be
17838 specified is 32767. Note that in the special case of configuration
17839 pragma files, the maximum is always 32767 regardless of whether or
17840 not this switch appears.
17842 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
17843 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
17844 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
17845 the generated body sample to @var{n}.
17846 The default indentation is 3.
17848 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
17849 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
17850 Order local bodies alphabetically. (By default local bodies are ordered
17851 in the same way as the corresponding local specs in the argument spec file.)
17853 @item ^-i^/INDENTATION=^@var{n}
17854 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
17855 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
17857 @item ^-k^/TREE_FILE=SAVE^
17858 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
17859 Do not remove the tree file (i.e., the snapshot of the compiler internal
17860 structures used by @command{gnatstub}) after creating the body stub.
17862 @item ^-l^/LINE_LENGTH=^@var{n}
17863 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
17864 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
17866 @item ^-o^/BODY=^@var{body-name}
17867 @cindex @option{^-o^/BODY^} (@command{gnatstub})
17868 Body file name. This should be set if the argument file name does not
17870 the GNAT file naming
17871 conventions. If this switch is omitted the default name for the body will be
17873 from the argument file name according to the GNAT file naming conventions.
17876 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
17877 Quiet mode: do not generate a confirmation when a body is
17878 successfully created, and do not generate a message when a body is not
17882 @item ^-r^/TREE_FILE=REUSE^
17883 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
17884 Reuse the tree file (if it exists) instead of creating it. Instead of
17885 creating the tree file for the library unit declaration, @command{gnatstub}
17886 tries to find it in the current directory and use it for creating
17887 a body. If the tree file is not found, no body is created. This option
17888 also implies @option{^-k^/SAVE^}, whether or not
17889 the latter is set explicitly.
17891 @item ^-t^/TREE_FILE=OVERWRITE^
17892 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
17893 Overwrite the existing tree file. If the current directory already
17894 contains the file which, according to the GNAT file naming rules should
17895 be considered as a tree file for the argument source file,
17897 will refuse to create the tree file needed to create a sample body
17898 unless this option is set.
17900 @item ^-v^/VERBOSE^
17901 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
17902 Verbose mode: generate version information.
17907 @node Other Utility Programs
17908 @chapter Other Utility Programs
17911 This chapter discusses some other utility programs available in the Ada
17915 * Using Other Utility Programs with GNAT::
17916 * The External Symbol Naming Scheme of GNAT::
17918 * Ada Mode for Glide::
17920 * Converting Ada Files to html with gnathtml::
17921 * Installing gnathtml::
17928 @node Using Other Utility Programs with GNAT
17929 @section Using Other Utility Programs with GNAT
17932 The object files generated by GNAT are in standard system format and in
17933 particular the debugging information uses this format. This means
17934 programs generated by GNAT can be used with existing utilities that
17935 depend on these formats.
17938 In general, any utility program that works with C will also often work with
17939 Ada programs generated by GNAT. This includes software utilities such as
17940 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
17944 @node The External Symbol Naming Scheme of GNAT
17945 @section The External Symbol Naming Scheme of GNAT
17948 In order to interpret the output from GNAT, when using tools that are
17949 originally intended for use with other languages, it is useful to
17950 understand the conventions used to generate link names from the Ada
17953 All link names are in all lowercase letters. With the exception of library
17954 procedure names, the mechanism used is simply to use the full expanded
17955 Ada name with dots replaced by double underscores. For example, suppose
17956 we have the following package spec:
17958 @smallexample @c ada
17969 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
17970 the corresponding link name is @code{qrs__mn}.
17972 Of course if a @code{pragma Export} is used this may be overridden:
17974 @smallexample @c ada
17979 pragma Export (Var1, C, External_Name => "var1_name");
17981 pragma Export (Var2, C, Link_Name => "var2_link_name");
17988 In this case, the link name for @var{Var1} is whatever link name the
17989 C compiler would assign for the C function @var{var1_name}. This typically
17990 would be either @var{var1_name} or @var{_var1_name}, depending on operating
17991 system conventions, but other possibilities exist. The link name for
17992 @var{Var2} is @var{var2_link_name}, and this is not operating system
17996 One exception occurs for library level procedures. A potential ambiguity
17997 arises between the required name @code{_main} for the C main program,
17998 and the name we would otherwise assign to an Ada library level procedure
17999 called @code{Main} (which might well not be the main program).
18001 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
18002 names. So if we have a library level procedure such as
18004 @smallexample @c ada
18007 procedure Hello (S : String);
18013 the external name of this procedure will be @var{_ada_hello}.
18016 @node Ada Mode for Glide
18017 @section Ada Mode for @code{Glide}
18018 @cindex Ada mode (for Glide)
18021 The Glide mode for programming in Ada (both Ada83 and Ada95) helps the
18022 user to understand and navigate existing code, and facilitates writing
18023 new code. It furthermore provides some utility functions for easier
18024 integration of standard Emacs features when programming in Ada.
18026 Its general features include:
18030 An Integrated Development Environment with functionality such as the
18035 ``Project files'' for configuration-specific aspects
18036 (e.g. directories and compilation options)
18039 Compiling and stepping through error messages.
18042 Running and debugging an applications within Glide.
18049 User configurability
18052 Some of the specific Ada mode features are:
18056 Functions for easy and quick stepping through Ada code
18059 Getting cross reference information for identifiers (e.g., finding a
18060 defining occurrence)
18063 Displaying an index menu of types and subprograms, allowing
18064 direct selection for browsing
18067 Automatic color highlighting of the various Ada entities
18070 Glide directly supports writing Ada code, via several facilities:
18074 Switching between spec and body files with possible
18075 autogeneration of body files
18078 Automatic formating of subprogram parameter lists
18081 Automatic indentation according to Ada syntax
18084 Automatic completion of identifiers
18087 Automatic (and configurable) casing of identifiers, keywords, and attributes
18090 Insertion of syntactic templates
18093 Block commenting / uncommenting
18097 For more information, please refer to the online documentation
18098 available in the @code{Glide} @result{} @code{Help} menu.
18102 @node Converting Ada Files to html with gnathtml
18103 @section Converting Ada Files to HTML with @code{gnathtml}
18106 This @code{Perl} script allows Ada source files to be browsed using
18107 standard Web browsers. For installation procedure, see the section
18108 @xref{Installing gnathtml}.
18110 Ada reserved keywords are highlighted in a bold font and Ada comments in
18111 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
18112 switch to suppress the generation of cross-referencing information, user
18113 defined variables and types will appear in a different color; you will
18114 be able to click on any identifier and go to its declaration.
18116 The command line is as follow:
18118 $ perl gnathtml.pl [switches] ada-files
18122 You can pass it as many Ada files as you want. @code{gnathtml} will generate
18123 an html file for every ada file, and a global file called @file{index.htm}.
18124 This file is an index of every identifier defined in the files.
18126 The available switches are the following ones :
18130 @cindex @option{-83} (@code{gnathtml})
18131 Only the subset on the Ada 83 keywords will be highlighted, not the full
18132 Ada 95 keywords set.
18134 @item -cc @var{color}
18135 @cindex @option{-cc} (@code{gnathtml})
18136 This option allows you to change the color used for comments. The default
18137 value is green. The color argument can be any name accepted by html.
18140 @cindex @option{-d} (@code{gnathtml})
18141 If the ada files depend on some other files (using for instance the
18142 @code{with} command, the latter will also be converted to html.
18143 Only the files in the user project will be converted to html, not the files
18144 in the run-time library itself.
18147 @cindex @option{-D} (@code{gnathtml})
18148 This command is the same as @option{-d} above, but @command{gnathtml} will
18149 also look for files in the run-time library, and generate html files for them.
18151 @item -ext @var{extension}
18152 @cindex @option{-ext} (@code{gnathtml})
18153 This option allows you to change the extension of the generated HTML files.
18154 If you do not specify an extension, it will default to @file{htm}.
18157 @cindex @option{-f} (@code{gnathtml})
18158 By default, gnathtml will generate html links only for global entities
18159 ('with'ed units, global variables and types,...). If you specify the
18160 @option{-f} on the command line, then links will be generated for local
18163 @item -l @var{number}
18164 @cindex @option{-l} (@code{gnathtml})
18165 If this switch is provided and @var{number} is not 0, then @code{gnathtml}
18166 will number the html files every @var{number} line.
18169 @cindex @option{-I} (@code{gnathtml})
18170 Specify a directory to search for library files (@file{.ALI} files) and
18171 source files. You can provide several -I switches on the command line,
18172 and the directories will be parsed in the order of the command line.
18175 @cindex @option{-o} (@code{gnathtml})
18176 Specify the output directory for html files. By default, gnathtml will
18177 saved the generated html files in a subdirectory named @file{html/}.
18179 @item -p @var{file}
18180 @cindex @option{-p} (@code{gnathtml})
18181 If you are using Emacs and the most recent Emacs Ada mode, which provides
18182 a full Integrated Development Environment for compiling, checking,
18183 running and debugging applications, you may use @file{.gpr} files
18184 to give the directories where Emacs can find sources and object files.
18186 Using this switch, you can tell gnathtml to use these files. This allows
18187 you to get an html version of your application, even if it is spread
18188 over multiple directories.
18190 @item -sc @var{color}
18191 @cindex @option{-sc} (@code{gnathtml})
18192 This option allows you to change the color used for symbol definitions.
18193 The default value is red. The color argument can be any name accepted by html.
18195 @item -t @var{file}
18196 @cindex @option{-t} (@code{gnathtml})
18197 This switch provides the name of a file. This file contains a list of
18198 file names to be converted, and the effect is exactly as though they had
18199 appeared explicitly on the command line. This
18200 is the recommended way to work around the command line length limit on some
18205 @node Installing gnathtml
18206 @section Installing @code{gnathtml}
18209 @code{Perl} needs to be installed on your machine to run this script.
18210 @code{Perl} is freely available for almost every architecture and
18211 Operating System via the Internet.
18213 On Unix systems, you may want to modify the first line of the script
18214 @code{gnathtml}, to explicitly tell the Operating system where Perl
18215 is. The syntax of this line is :
18217 #!full_path_name_to_perl
18221 Alternatively, you may run the script using the following command line:
18224 $ perl gnathtml.pl [switches] files
18233 The GNAT distribution provides an Ada 95 template for the Digital Language
18234 Sensitive Editor (LSE), a component of DECset. In order to
18235 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
18242 GNAT supports The Digital Performance Coverage Analyzer (PCA), a component
18243 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
18244 the collection phase with the /DEBUG qualifier.
18247 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
18248 $ DEFINE LIB$DEBUG PCA$COLLECTOR
18249 $ RUN/DEBUG <PROGRAM_NAME>
18254 @node Running and Debugging Ada Programs
18255 @chapter Running and Debugging Ada Programs
18259 This chapter discusses how to debug Ada programs. An incorrect Ada program
18260 may be handled in three ways by the GNAT compiler:
18264 The illegality may be a violation of the static semantics of Ada. In
18265 that case GNAT diagnoses the constructs in the program that are illegal.
18266 It is then a straightforward matter for the user to modify those parts of
18270 The illegality may be a violation of the dynamic semantics of Ada. In
18271 that case the program compiles and executes, but may generate incorrect
18272 results, or may terminate abnormally with some exception.
18275 When presented with a program that contains convoluted errors, GNAT
18276 itself may terminate abnormally without providing full diagnostics on
18277 the incorrect user program.
18281 * The GNAT Debugger GDB::
18283 * Introduction to GDB Commands::
18284 * Using Ada Expressions::
18285 * Calling User-Defined Subprograms::
18286 * Using the Next Command in a Function::
18289 * Debugging Generic Units::
18290 * GNAT Abnormal Termination or Failure to Terminate::
18291 * Naming Conventions for GNAT Source Files::
18292 * Getting Internal Debugging Information::
18293 * Stack Traceback::
18299 @node The GNAT Debugger GDB
18300 @section The GNAT Debugger GDB
18303 @code{GDB} is a general purpose, platform-independent debugger that
18304 can be used to debug mixed-language programs compiled with @code{GCC},
18305 and in particular is capable of debugging Ada programs compiled with
18306 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
18307 complex Ada data structures.
18309 The manual @cite{Debugging with GDB}
18311 , located in the GNU:[DOCS] directory,
18313 contains full details on the usage of @code{GDB}, including a section on
18314 its usage on programs. This manual should be consulted for full
18315 details. The section that follows is a brief introduction to the
18316 philosophy and use of @code{GDB}.
18318 When GNAT programs are compiled, the compiler optionally writes debugging
18319 information into the generated object file, including information on
18320 line numbers, and on declared types and variables. This information is
18321 separate from the generated code. It makes the object files considerably
18322 larger, but it does not add to the size of the actual executable that
18323 will be loaded into memory, and has no impact on run-time performance. The
18324 generation of debug information is triggered by the use of the
18325 ^-g^/DEBUG^ switch in the gcc or gnatmake command used to carry out
18326 the compilations. It is important to emphasize that the use of these
18327 options does not change the generated code.
18329 The debugging information is written in standard system formats that
18330 are used by many tools, including debuggers and profilers. The format
18331 of the information is typically designed to describe C types and
18332 semantics, but GNAT implements a translation scheme which allows full
18333 details about Ada types and variables to be encoded into these
18334 standard C formats. Details of this encoding scheme may be found in
18335 the file exp_dbug.ads in the GNAT source distribution. However, the
18336 details of this encoding are, in general, of no interest to a user,
18337 since @code{GDB} automatically performs the necessary decoding.
18339 When a program is bound and linked, the debugging information is
18340 collected from the object files, and stored in the executable image of
18341 the program. Again, this process significantly increases the size of
18342 the generated executable file, but it does not increase the size of
18343 the executable program itself. Furthermore, if this program is run in
18344 the normal manner, it runs exactly as if the debug information were
18345 not present, and takes no more actual memory.
18347 However, if the program is run under control of @code{GDB}, the
18348 debugger is activated. The image of the program is loaded, at which
18349 point it is ready to run. If a run command is given, then the program
18350 will run exactly as it would have if @code{GDB} were not present. This
18351 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
18352 entirely non-intrusive until a breakpoint is encountered. If no
18353 breakpoint is ever hit, the program will run exactly as it would if no
18354 debugger were present. When a breakpoint is hit, @code{GDB} accesses
18355 the debugging information and can respond to user commands to inspect
18356 variables, and more generally to report on the state of execution.
18360 @section Running GDB
18363 The debugger can be launched directly and simply from @code{glide} or
18364 through its graphical interface: @code{gvd}. It can also be used
18365 directly in text mode. Here is described the basic use of @code{GDB}
18366 in text mode. All the commands described below can be used in the
18367 @code{gvd} console window even though there is usually other more
18368 graphical ways to achieve the same goals.
18372 The command to run the graphical interface of the debugger is
18379 The command to run @code{GDB} in text mode is
18382 $ ^gdb program^$ GDB PROGRAM^
18386 where @code{^program^PROGRAM^} is the name of the executable file. This
18387 activates the debugger and results in a prompt for debugger commands.
18388 The simplest command is simply @code{run}, which causes the program to run
18389 exactly as if the debugger were not present. The following section
18390 describes some of the additional commands that can be given to @code{GDB}.
18393 @c *******************************
18394 @node Introduction to GDB Commands
18395 @section Introduction to GDB Commands
18398 @code{GDB} contains a large repertoire of commands. The manual
18399 @cite{Debugging with GDB}
18401 , located in the GNU:[DOCS] directory,
18403 includes extensive documentation on the use
18404 of these commands, together with examples of their use. Furthermore,
18405 the command @var{help} invoked from within @code{GDB} activates a simple help
18406 facility which summarizes the available commands and their options.
18407 In this section we summarize a few of the most commonly
18408 used commands to give an idea of what @code{GDB} is about. You should create
18409 a simple program with debugging information and experiment with the use of
18410 these @code{GDB} commands on the program as you read through the
18414 @item set args @var{arguments}
18415 The @var{arguments} list above is a list of arguments to be passed to
18416 the program on a subsequent run command, just as though the arguments
18417 had been entered on a normal invocation of the program. The @code{set args}
18418 command is not needed if the program does not require arguments.
18421 The @code{run} command causes execution of the program to start from
18422 the beginning. If the program is already running, that is to say if
18423 you are currently positioned at a breakpoint, then a prompt will ask
18424 for confirmation that you want to abandon the current execution and
18427 @item breakpoint @var{location}
18428 The breakpoint command sets a breakpoint, that is to say a point at which
18429 execution will halt and @code{GDB} will await further
18430 commands. @var{location} is
18431 either a line number within a file, given in the format @code{file:linenumber},
18432 or it is the name of a subprogram. If you request that a breakpoint be set on
18433 a subprogram that is overloaded, a prompt will ask you to specify on which of
18434 those subprograms you want to breakpoint. You can also
18435 specify that all of them should be breakpointed. If the program is run
18436 and execution encounters the breakpoint, then the program
18437 stops and @code{GDB} signals that the breakpoint was encountered by
18438 printing the line of code before which the program is halted.
18440 @item breakpoint exception @var{name}
18441 A special form of the breakpoint command which breakpoints whenever
18442 exception @var{name} is raised.
18443 If @var{name} is omitted,
18444 then a breakpoint will occur when any exception is raised.
18446 @item print @var{expression}
18447 This will print the value of the given expression. Most simple
18448 Ada expression formats are properly handled by @code{GDB}, so the expression
18449 can contain function calls, variables, operators, and attribute references.
18452 Continues execution following a breakpoint, until the next breakpoint or the
18453 termination of the program.
18456 Executes a single line after a breakpoint. If the next statement
18457 is a subprogram call, execution continues into (the first statement of)
18458 the called subprogram.
18461 Executes a single line. If this line is a subprogram call, executes and
18462 returns from the call.
18465 Lists a few lines around the current source location. In practice, it
18466 is usually more convenient to have a separate edit window open with the
18467 relevant source file displayed. Successive applications of this command
18468 print subsequent lines. The command can be given an argument which is a
18469 line number, in which case it displays a few lines around the specified one.
18472 Displays a backtrace of the call chain. This command is typically
18473 used after a breakpoint has occurred, to examine the sequence of calls that
18474 leads to the current breakpoint. The display includes one line for each
18475 activation record (frame) corresponding to an active subprogram.
18478 At a breakpoint, @code{GDB} can display the values of variables local
18479 to the current frame. The command @code{up} can be used to
18480 examine the contents of other active frames, by moving the focus up
18481 the stack, that is to say from callee to caller, one frame at a time.
18484 Moves the focus of @code{GDB} down from the frame currently being
18485 examined to the frame of its callee (the reverse of the previous command),
18487 @item frame @var{n}
18488 Inspect the frame with the given number. The value 0 denotes the frame
18489 of the current breakpoint, that is to say the top of the call stack.
18493 The above list is a very short introduction to the commands that
18494 @code{GDB} provides. Important additional capabilities, including conditional
18495 breakpoints, the ability to execute command sequences on a breakpoint,
18496 the ability to debug at the machine instruction level and many other
18497 features are described in detail in @cite{Debugging with GDB}.
18498 Note that most commands can be abbreviated
18499 (for example, c for continue, bt for backtrace).
18501 @node Using Ada Expressions
18502 @section Using Ada Expressions
18503 @cindex Ada expressions
18506 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
18507 extensions. The philosophy behind the design of this subset is
18511 That @code{GDB} should provide basic literals and access to operations for
18512 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18513 leaving more sophisticated computations to subprograms written into the
18514 program (which therefore may be called from @code{GDB}).
18517 That type safety and strict adherence to Ada language restrictions
18518 are not particularly important to the @code{GDB} user.
18521 That brevity is important to the @code{GDB} user.
18524 Thus, for brevity, the debugger acts as if there were
18525 implicit @code{with} and @code{use} clauses in effect for all user-written
18526 packages, thus making it unnecessary to fully qualify most names with
18527 their packages, regardless of context. Where this causes ambiguity,
18528 @code{GDB} asks the user's intent.
18530 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
18532 @node Calling User-Defined Subprograms
18533 @section Calling User-Defined Subprograms
18536 An important capability of @code{GDB} is the ability to call user-defined
18537 subprograms while debugging. This is achieved simply by entering
18538 a subprogram call statement in the form:
18541 call subprogram-name (parameters)
18545 The keyword @code{call} can be omitted in the normal case where the
18546 @code{subprogram-name} does not coincide with any of the predefined
18547 @code{GDB} commands.
18549 The effect is to invoke the given subprogram, passing it the
18550 list of parameters that is supplied. The parameters can be expressions and
18551 can include variables from the program being debugged. The
18552 subprogram must be defined
18553 at the library level within your program, and @code{GDB} will call the
18554 subprogram within the environment of your program execution (which
18555 means that the subprogram is free to access or even modify variables
18556 within your program).
18558 The most important use of this facility is in allowing the inclusion of
18559 debugging routines that are tailored to particular data structures
18560 in your program. Such debugging routines can be written to provide a suitably
18561 high-level description of an abstract type, rather than a low-level dump
18562 of its physical layout. After all, the standard
18563 @code{GDB print} command only knows the physical layout of your
18564 types, not their abstract meaning. Debugging routines can provide information
18565 at the desired semantic level and are thus enormously useful.
18567 For example, when debugging GNAT itself, it is crucial to have access to
18568 the contents of the tree nodes used to represent the program internally.
18569 But tree nodes are represented simply by an integer value (which in turn
18570 is an index into a table of nodes).
18571 Using the @code{print} command on a tree node would simply print this integer
18572 value, which is not very useful. But the PN routine (defined in file
18573 treepr.adb in the GNAT sources) takes a tree node as input, and displays
18574 a useful high level representation of the tree node, which includes the
18575 syntactic category of the node, its position in the source, the integers
18576 that denote descendant nodes and parent node, as well as varied
18577 semantic information. To study this example in more detail, you might want to
18578 look at the body of the PN procedure in the stated file.
18580 @node Using the Next Command in a Function
18581 @section Using the Next Command in a Function
18584 When you use the @code{next} command in a function, the current source
18585 location will advance to the next statement as usual. A special case
18586 arises in the case of a @code{return} statement.
18588 Part of the code for a return statement is the ``epilog'' of the function.
18589 This is the code that returns to the caller. There is only one copy of
18590 this epilog code, and it is typically associated with the last return
18591 statement in the function if there is more than one return. In some
18592 implementations, this epilog is associated with the first statement
18595 The result is that if you use the @code{next} command from a return
18596 statement that is not the last return statement of the function you
18597 may see a strange apparent jump to the last return statement or to
18598 the start of the function. You should simply ignore this odd jump.
18599 The value returned is always that from the first return statement
18600 that was stepped through.
18602 @node Ada Exceptions
18603 @section Breaking on Ada Exceptions
18607 You can set breakpoints that trip when your program raises
18608 selected exceptions.
18611 @item break exception
18612 Set a breakpoint that trips whenever (any task in the) program raises
18615 @item break exception @var{name}
18616 Set a breakpoint that trips whenever (any task in the) program raises
18617 the exception @var{name}.
18619 @item break exception unhandled
18620 Set a breakpoint that trips whenever (any task in the) program raises an
18621 exception for which there is no handler.
18623 @item info exceptions
18624 @itemx info exceptions @var{regexp}
18625 The @code{info exceptions} command permits the user to examine all defined
18626 exceptions within Ada programs. With a regular expression, @var{regexp}, as
18627 argument, prints out only those exceptions whose name matches @var{regexp}.
18635 @code{GDB} allows the following task-related commands:
18639 This command shows a list of current Ada tasks, as in the following example:
18646 ID TID P-ID Thread Pri State Name
18647 1 8088000 0 807e000 15 Child Activation Wait main_task
18648 2 80a4000 1 80ae000 15 Accept/Select Wait b
18649 3 809a800 1 80a4800 15 Child Activation Wait a
18650 * 4 80ae800 3 80b8000 15 Running c
18654 In this listing, the asterisk before the first task indicates it to be the
18655 currently running task. The first column lists the task ID that is used
18656 to refer to tasks in the following commands.
18658 @item break @var{linespec} task @var{taskid}
18659 @itemx break @var{linespec} task @var{taskid} if @dots{}
18660 @cindex Breakpoints and tasks
18661 These commands are like the @code{break @dots{} thread @dots{}}.
18662 @var{linespec} specifies source lines.
18664 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
18665 to specify that you only want @code{GDB} to stop the program when a
18666 particular Ada task reaches this breakpoint. @var{taskid} is one of the
18667 numeric task identifiers assigned by @code{GDB}, shown in the first
18668 column of the @samp{info tasks} display.
18670 If you do not specify @samp{task @var{taskid}} when you set a
18671 breakpoint, the breakpoint applies to @emph{all} tasks of your
18674 You can use the @code{task} qualifier on conditional breakpoints as
18675 well; in this case, place @samp{task @var{taskid}} before the
18676 breakpoint condition (before the @code{if}).
18678 @item task @var{taskno}
18679 @cindex Task switching
18681 This command allows to switch to the task referred by @var{taskno}. In
18682 particular, This allows to browse the backtrace of the specified
18683 task. It is advised to switch back to the original task before
18684 continuing execution otherwise the scheduling of the program may be
18689 For more detailed information on the tasking support,
18690 see @cite{Debugging with GDB}.
18692 @node Debugging Generic Units
18693 @section Debugging Generic Units
18694 @cindex Debugging Generic Units
18698 GNAT always uses code expansion for generic instantiation. This means that
18699 each time an instantiation occurs, a complete copy of the original code is
18700 made, with appropriate substitutions of formals by actuals.
18702 It is not possible to refer to the original generic entities in
18703 @code{GDB}, but it is always possible to debug a particular instance of
18704 a generic, by using the appropriate expanded names. For example, if we have
18706 @smallexample @c ada
18711 generic package k is
18712 procedure kp (v1 : in out integer);
18716 procedure kp (v1 : in out integer) is
18722 package k1 is new k;
18723 package k2 is new k;
18725 var : integer := 1;
18738 Then to break on a call to procedure kp in the k2 instance, simply
18742 (gdb) break g.k2.kp
18746 When the breakpoint occurs, you can step through the code of the
18747 instance in the normal manner and examine the values of local variables, as for
18750 @node GNAT Abnormal Termination or Failure to Terminate
18751 @section GNAT Abnormal Termination or Failure to Terminate
18752 @cindex GNAT Abnormal Termination or Failure to Terminate
18755 When presented with programs that contain serious errors in syntax
18757 GNAT may on rare occasions experience problems in operation, such
18759 segmentation fault or illegal memory access, raising an internal
18760 exception, terminating abnormally, or failing to terminate at all.
18761 In such cases, you can activate
18762 various features of GNAT that can help you pinpoint the construct in your
18763 program that is the likely source of the problem.
18765 The following strategies are presented in increasing order of
18766 difficulty, corresponding to your experience in using GNAT and your
18767 familiarity with compiler internals.
18771 Run @code{gcc} with the @option{-gnatf}. This first
18772 switch causes all errors on a given line to be reported. In its absence,
18773 only the first error on a line is displayed.
18775 The @option{-gnatdO} switch causes errors to be displayed as soon as they
18776 are encountered, rather than after compilation is terminated. If GNAT
18777 terminates prematurely or goes into an infinite loop, the last error
18778 message displayed may help to pinpoint the culprit.
18781 Run @code{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this mode,
18782 @code{gcc} produces ongoing information about the progress of the
18783 compilation and provides the name of each procedure as code is
18784 generated. This switch allows you to find which Ada procedure was being
18785 compiled when it encountered a code generation problem.
18788 @cindex @option{-gnatdc} switch
18789 Run @code{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
18790 switch that does for the front-end what @option{^-v^VERBOSE^} does
18791 for the back end. The system prints the name of each unit,
18792 either a compilation unit or nested unit, as it is being analyzed.
18794 Finally, you can start
18795 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
18796 front-end of GNAT, and can be run independently (normally it is just
18797 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
18798 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
18799 @code{where} command is the first line of attack; the variable
18800 @code{lineno} (seen by @code{print lineno}), used by the second phase of
18801 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
18802 which the execution stopped, and @code{input_file name} indicates the name of
18806 @node Naming Conventions for GNAT Source Files
18807 @section Naming Conventions for GNAT Source Files
18810 In order to examine the workings of the GNAT system, the following
18811 brief description of its organization may be helpful:
18815 Files with prefix @file{^sc^SC^} contain the lexical scanner.
18818 All files prefixed with @file{^par^PAR^} are components of the parser. The
18819 numbers correspond to chapters of the Ada 95 Reference Manual. For example,
18820 parsing of select statements can be found in @file{par-ch9.adb}.
18823 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
18824 numbers correspond to chapters of the Ada standard. For example, all
18825 issues involving context clauses can be found in @file{sem_ch10.adb}. In
18826 addition, some features of the language require sufficient special processing
18827 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
18828 dynamic dispatching, etc.
18831 All files prefixed with @file{^exp^EXP^} perform normalization and
18832 expansion of the intermediate representation (abstract syntax tree, or AST).
18833 these files use the same numbering scheme as the parser and semantics files.
18834 For example, the construction of record initialization procedures is done in
18835 @file{exp_ch3.adb}.
18838 The files prefixed with @file{^bind^BIND^} implement the binder, which
18839 verifies the consistency of the compilation, determines an order of
18840 elaboration, and generates the bind file.
18843 The files @file{atree.ads} and @file{atree.adb} detail the low-level
18844 data structures used by the front-end.
18847 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
18848 the abstract syntax tree as produced by the parser.
18851 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
18852 all entities, computed during semantic analysis.
18855 Library management issues are dealt with in files with prefix
18861 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
18862 defined in Annex A.
18867 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
18868 defined in Annex B.
18872 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
18873 both language-defined children and GNAT run-time routines.
18877 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
18878 general-purpose packages, fully documented in their specifications. All
18879 the other @file{.c} files are modifications of common @code{gcc} files.
18882 @node Getting Internal Debugging Information
18883 @section Getting Internal Debugging Information
18886 Most compilers have internal debugging switches and modes. GNAT
18887 does also, except GNAT internal debugging switches and modes are not
18888 secret. A summary and full description of all the compiler and binder
18889 debug flags are in the file @file{debug.adb}. You must obtain the
18890 sources of the compiler to see the full detailed effects of these flags.
18892 The switches that print the source of the program (reconstructed from
18893 the internal tree) are of general interest for user programs, as are the
18895 the full internal tree, and the entity table (the symbol table
18896 information). The reconstructed source provides a readable version of the
18897 program after the front-end has completed analysis and expansion,
18898 and is useful when studying the performance of specific constructs.
18899 For example, constraint checks are indicated, complex aggregates
18900 are replaced with loops and assignments, and tasking primitives
18901 are replaced with run-time calls.
18903 @node Stack Traceback
18904 @section Stack Traceback
18906 @cindex stack traceback
18907 @cindex stack unwinding
18910 Traceback is a mechanism to display the sequence of subprogram calls that
18911 leads to a specified execution point in a program. Often (but not always)
18912 the execution point is an instruction at which an exception has been raised.
18913 This mechanism is also known as @i{stack unwinding} because it obtains
18914 its information by scanning the run-time stack and recovering the activation
18915 records of all active subprograms. Stack unwinding is one of the most
18916 important tools for program debugging.
18918 The first entry stored in traceback corresponds to the deepest calling level,
18919 that is to say the subprogram currently executing the instruction
18920 from which we want to obtain the traceback.
18922 Note that there is no runtime performance penalty when stack traceback
18923 is enabled, and no exception is raised during program execution.
18926 * Non-Symbolic Traceback::
18927 * Symbolic Traceback::
18930 @node Non-Symbolic Traceback
18931 @subsection Non-Symbolic Traceback
18932 @cindex traceback, non-symbolic
18935 Note: this feature is not supported on all platforms. See
18936 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
18940 * Tracebacks From an Unhandled Exception::
18941 * Tracebacks From Exception Occurrences (non-symbolic)::
18942 * Tracebacks From Anywhere in a Program (non-symbolic)::
18945 @node Tracebacks From an Unhandled Exception
18946 @subsubsection Tracebacks From an Unhandled Exception
18949 A runtime non-symbolic traceback is a list of addresses of call instructions.
18950 To enable this feature you must use the @option{-E}
18951 @code{gnatbind}'s option. With this option a stack traceback is stored as part
18952 of exception information. You can retrieve this information using the
18953 @code{addr2line} tool.
18955 Here is a simple example:
18957 @smallexample @c ada
18963 raise Constraint_Error;
18978 $ gnatmake stb -bargs -E
18981 Execution terminated by unhandled exception
18982 Exception name: CONSTRAINT_ERROR
18984 Call stack traceback locations:
18985 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
18989 As we see the traceback lists a sequence of addresses for the unhandled
18990 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
18991 guess that this exception come from procedure P1. To translate these
18992 addresses into the source lines where the calls appear, the
18993 @code{addr2line} tool, described below, is invaluable. The use of this tool
18994 requires the program to be compiled with debug information.
18997 $ gnatmake -g stb -bargs -E
19000 Execution terminated by unhandled exception
19001 Exception name: CONSTRAINT_ERROR
19003 Call stack traceback locations:
19004 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
19006 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
19007 0x4011f1 0x77e892a4
19009 00401373 at d:/stb/stb.adb:5
19010 0040138B at d:/stb/stb.adb:10
19011 0040139C at d:/stb/stb.adb:14
19012 00401335 at d:/stb/b~stb.adb:104
19013 004011C4 at /build/.../crt1.c:200
19014 004011F1 at /build/.../crt1.c:222
19015 77E892A4 in ?? at ??:0
19019 The @code{addr2line} tool has several other useful options:
19023 to get the function name corresponding to any location
19025 @item --demangle=gnat
19026 to use the gnat decoding mode for the function names. Note that
19027 for binutils version 2.9.x the option is simply @option{--demangle}.
19031 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
19032 0x40139c 0x401335 0x4011c4 0x4011f1
19034 00401373 in stb.p1 at d:/stb/stb.adb:5
19035 0040138B in stb.p2 at d:/stb/stb.adb:10
19036 0040139C in stb at d:/stb/stb.adb:14
19037 00401335 in main at d:/stb/b~stb.adb:104
19038 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
19039 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
19043 From this traceback we can see that the exception was raised in
19044 @file{stb.adb} at line 5, which was reached from a procedure call in
19045 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
19046 which contains the call to the main program.
19047 @pxref{Running gnatbind}. The remaining entries are assorted runtime routines,
19048 and the output will vary from platform to platform.
19050 It is also possible to use @code{GDB} with these traceback addresses to debug
19051 the program. For example, we can break at a given code location, as reported
19052 in the stack traceback:
19058 Furthermore, this feature is not implemented inside Windows DLL. Only
19059 the non-symbolic traceback is reported in this case.
19062 (gdb) break *0x401373
19063 Breakpoint 1 at 0x401373: file stb.adb, line 5.
19067 It is important to note that the stack traceback addresses
19068 do not change when debug information is included. This is particularly useful
19069 because it makes it possible to release software without debug information (to
19070 minimize object size), get a field report that includes a stack traceback
19071 whenever an internal bug occurs, and then be able to retrieve the sequence
19072 of calls with the same program compiled with debug information.
19074 @node Tracebacks From Exception Occurrences (non-symbolic)
19075 @subsubsection Tracebacks From Exception Occurrences
19078 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
19079 The stack traceback is attached to the exception information string, and can
19080 be retrieved in an exception handler within the Ada program, by means of the
19081 Ada95 facilities defined in @code{Ada.Exceptions}. Here is a simple example:
19083 @smallexample @c ada
19085 with Ada.Exceptions;
19090 use Ada.Exceptions;
19098 Text_IO.Put_Line (Exception_Information (E));
19112 This program will output:
19117 Exception name: CONSTRAINT_ERROR
19118 Message: stb.adb:12
19119 Call stack traceback locations:
19120 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
19123 @node Tracebacks From Anywhere in a Program (non-symbolic)
19124 @subsubsection Tracebacks From Anywhere in a Program
19127 It is also possible to retrieve a stack traceback from anywhere in a
19128 program. For this you need to
19129 use the @code{GNAT.Traceback} API. This package includes a procedure called
19130 @code{Call_Chain} that computes a complete stack traceback, as well as useful
19131 display procedures described below. It is not necessary to use the
19132 @option{-E gnatbind} option in this case, because the stack traceback mechanism
19133 is invoked explicitly.
19136 In the following example we compute a traceback at a specific location in
19137 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
19138 convert addresses to strings:
19140 @smallexample @c ada
19142 with GNAT.Traceback;
19143 with GNAT.Debug_Utilities;
19149 use GNAT.Traceback;
19152 TB : Tracebacks_Array (1 .. 10);
19153 -- We are asking for a maximum of 10 stack frames.
19155 -- Len will receive the actual number of stack frames returned.
19157 Call_Chain (TB, Len);
19159 Text_IO.Put ("In STB.P1 : ");
19161 for K in 1 .. Len loop
19162 Text_IO.Put (Debug_Utilities.Image (TB (K)));
19183 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
19184 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
19188 You can then get further information by invoking the @code{addr2line}
19189 tool as described earlier (note that the hexadecimal addresses
19190 need to be specified in C format, with a leading ``0x'').
19193 @node Symbolic Traceback
19194 @subsection Symbolic Traceback
19195 @cindex traceback, symbolic
19198 A symbolic traceback is a stack traceback in which procedure names are
19199 associated with each code location.
19202 Note that this feature is not supported on all platforms. See
19203 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
19204 list of currently supported platforms.
19207 Note that the symbolic traceback requires that the program be compiled
19208 with debug information. If it is not compiled with debug information
19209 only the non-symbolic information will be valid.
19212 * Tracebacks From Exception Occurrences (symbolic)::
19213 * Tracebacks From Anywhere in a Program (symbolic)::
19216 @node Tracebacks From Exception Occurrences (symbolic)
19217 @subsubsection Tracebacks From Exception Occurrences
19219 @smallexample @c ada
19221 with GNAT.Traceback.Symbolic;
19227 raise Constraint_Error;
19244 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
19249 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
19252 0040149F in stb.p1 at stb.adb:8
19253 004014B7 in stb.p2 at stb.adb:13
19254 004014CF in stb.p3 at stb.adb:18
19255 004015DD in ada.stb at stb.adb:22
19256 00401461 in main at b~stb.adb:168
19257 004011C4 in __mingw_CRTStartup at crt1.c:200
19258 004011F1 in mainCRTStartup at crt1.c:222
19259 77E892A4 in ?? at ??:0
19263 In the above example the ``.\'' syntax in the @command{gnatmake} command
19264 is currently required by @command{addr2line} for files that are in
19265 the current working directory.
19266 Moreover, the exact sequence of linker options may vary from platform
19268 The above @option{-largs} section is for Windows platforms. By contrast,
19269 under Unix there is no need for the @option{-largs} section.
19270 Differences across platforms are due to details of linker implementation.
19272 @node Tracebacks From Anywhere in a Program (symbolic)
19273 @subsubsection Tracebacks From Anywhere in a Program
19276 It is possible to get a symbolic stack traceback
19277 from anywhere in a program, just as for non-symbolic tracebacks.
19278 The first step is to obtain a non-symbolic
19279 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
19280 information. Here is an example:
19282 @smallexample @c ada
19284 with GNAT.Traceback;
19285 with GNAT.Traceback.Symbolic;
19290 use GNAT.Traceback;
19291 use GNAT.Traceback.Symbolic;
19294 TB : Tracebacks_Array (1 .. 10);
19295 -- We are asking for a maximum of 10 stack frames.
19297 -- Len will receive the actual number of stack frames returned.
19299 Call_Chain (TB, Len);
19300 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
19314 @node Compatibility with DEC Ada
19315 @chapter Compatibility with DEC Ada
19316 @cindex Compatibility
19319 This section of the manual compares DEC Ada for OpenVMS Alpha and GNAT
19320 OpenVMS Alpha. GNAT achieves a high level of compatibility
19321 with DEC Ada, and it should generally be straightforward to port code
19322 from the DEC Ada environment to GNAT. However, there are a few language
19323 and implementation differences of which the user must be aware. These
19324 differences are discussed in this section. In
19325 addition, the operating environment and command structure for the
19326 compiler are different, and these differences are also discussed.
19328 Note that this discussion addresses specifically the implementation
19329 of Ada 83 for DIGITAL OpenVMS Alpha Systems. In cases where the implementation
19330 of DEC Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
19331 GNAT always follows the Alpha implementation.
19334 * Ada 95 Compatibility::
19335 * Differences in the Definition of Package System::
19336 * Language-Related Features::
19337 * The Package STANDARD::
19338 * The Package SYSTEM::
19339 * Tasking and Task-Related Features::
19340 * Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
19341 * Pragmas and Pragma-Related Features::
19342 * Library of Predefined Units::
19344 * Main Program Definition::
19345 * Implementation-Defined Attributes::
19346 * Compiler and Run-Time Interfacing::
19347 * Program Compilation and Library Management::
19349 * Implementation Limits::
19353 @node Ada 95 Compatibility
19354 @section Ada 95 Compatibility
19357 GNAT is an Ada 95 compiler, and DEC Ada is an Ada 83
19358 compiler. Ada 95 is almost completely upwards compatible
19359 with Ada 83, and therefore Ada 83 programs will compile
19360 and run under GNAT with
19361 no changes or only minor changes. The Ada 95 Reference
19362 Manual (ANSI/ISO/IEC-8652:1995) provides details on specific
19365 GNAT provides the switch /83 on the GNAT COMPILE command,
19366 as well as the pragma ADA_83, to force the compiler to
19367 operate in Ada 83 mode. This mode does not guarantee complete
19368 conformance to Ada 83, but in practice is sufficient to
19369 eliminate most sources of incompatibilities.
19370 In particular, it eliminates the recognition of the
19371 additional Ada 95 keywords, so that their use as identifiers
19372 in Ada83 program is legal, and handles the cases of packages
19373 with optional bodies, and generics that instantiate unconstrained
19374 types without the use of @code{(<>)}.
19376 @node Differences in the Definition of Package System
19377 @section Differences in the Definition of Package System
19380 Both the Ada 95 and Ada 83 reference manuals permit a compiler to add
19381 implementation-dependent declarations to package System. In normal mode,
19382 GNAT does not take advantage of this permission, and the version of System
19383 provided by GNAT exactly matches that in the Ada 95 Reference Manual.
19385 However, DEC Ada adds an extensive set of declarations to package System,
19386 as fully documented in the DEC Ada manuals. To minimize changes required
19387 for programs that make use of these extensions, GNAT provides the pragma
19388 Extend_System for extending the definition of package System. By using:
19390 @smallexample @c ada
19393 pragma Extend_System (Aux_DEC);
19399 The set of definitions in System is extended to include those in package
19400 @code{System.Aux_DEC}.
19401 These definitions are incorporated directly into package
19402 System, as though they had been declared there in the first place. For a
19403 list of the declarations added, see the specification of this package,
19404 which can be found in the file @code{s-auxdec.ads} in the GNAT library.
19405 The pragma Extend_System is a configuration pragma, which means that
19406 it can be placed in the file @file{gnat.adc}, so that it will automatically
19407 apply to all subsequent compilations. See the section on Configuration
19408 Pragmas for further details.
19410 An alternative approach that avoids the use of the non-standard
19411 Extend_System pragma is to add a context clause to the unit that
19412 references these facilities:
19414 @smallexample @c ada
19417 with System.Aux_DEC;
19418 use System.Aux_DEC;
19424 The effect is not quite semantically identical to incorporating
19425 the declarations directly into package @code{System},
19426 but most programs will not notice a difference
19427 unless they use prefix notation (e.g. @code{System.Integer_8})
19429 entities directly in package @code{System}.
19430 For units containing such references,
19431 the prefixes must either be removed, or the pragma @code{Extend_System}
19434 @node Language-Related Features
19435 @section Language-Related Features
19438 The following sections highlight differences in types,
19439 representations of types, operations, alignment, and
19443 * Integer Types and Representations::
19444 * Floating-Point Types and Representations::
19445 * Pragmas Float_Representation and Long_Float::
19446 * Fixed-Point Types and Representations::
19447 * Record and Array Component Alignment::
19448 * Address Clauses::
19449 * Other Representation Clauses::
19452 @node Integer Types and Representations
19453 @subsection Integer Types and Representations
19456 The set of predefined integer types is identical in DEC Ada and GNAT.
19457 Furthermore the representation of these integer types is also identical,
19458 including the capability of size clauses forcing biased representation.
19461 DEC Ada for OpenVMS Alpha systems has defined the
19462 following additional integer types in package System:
19483 When using GNAT, the first four of these types may be obtained from the
19484 standard Ada 95 package @code{Interfaces}.
19485 Alternatively, by use of the pragma
19486 @code{Extend_System}, identical
19487 declarations can be referenced directly in package @code{System}.
19488 On both GNAT and DEC Ada, the maximum integer size is 64 bits.
19490 @node Floating-Point Types and Representations
19491 @subsection Floating-Point Types and Representations
19492 @cindex Floating-Point types
19495 The set of predefined floating-point types is identical in DEC Ada and GNAT.
19496 Furthermore the representation of these floating-point
19497 types is also identical. One important difference is that the default
19498 representation for DEC Ada is VAX_Float, but the default representation
19501 Specific types may be declared to be VAX_Float or IEEE, using the pragma
19502 @code{Float_Representation} as described in the DEC Ada documentation.
19503 For example, the declarations:
19505 @smallexample @c ada
19508 type F_Float is digits 6;
19509 pragma Float_Representation (VAX_Float, F_Float);
19515 declare a type F_Float that will be represented in VAX_Float format.
19516 This set of declarations actually appears in System.Aux_DEC, which provides
19517 the full set of additional floating-point declarations provided in
19518 the DEC Ada version of package
19519 System. This and similar declarations may be accessed in a user program
19520 by using pragma @code{Extend_System}. The use of this
19521 pragma, and the related pragma @code{Long_Float} is described in further
19522 detail in the following section.
19524 @node Pragmas Float_Representation and Long_Float
19525 @subsection Pragmas Float_Representation and Long_Float
19528 DEC Ada provides the pragma @code{Float_Representation}, which
19529 acts as a program library switch to allow control over
19530 the internal representation chosen for the predefined
19531 floating-point types declared in the package @code{Standard}.
19532 The format of this pragma is as follows:
19537 @b{pragma} @code{Float_Representation}(VAX_Float | IEEE_Float);
19543 This pragma controls the representation of floating-point
19548 @code{VAX_Float} specifies that floating-point
19549 types are represented by default with the VAX hardware types
19550 F-floating, D-floating, G-floating. Note that the H-floating
19551 type is available only on DIGITAL Vax systems, and is not available
19552 in either DEC Ada or GNAT for Alpha systems.
19555 @code{IEEE_Float} specifies that floating-point
19556 types are represented by default with the IEEE single and
19557 double floating-point types.
19561 GNAT provides an identical implementation of the pragma
19562 @code{Float_Representation}, except that it functions as a
19563 configuration pragma, as defined by Ada 95. Note that the
19564 notion of configuration pragma corresponds closely to the
19565 DEC Ada notion of a program library switch.
19567 When no pragma is used in GNAT, the default is IEEE_Float, which is different
19568 from DEC Ada 83, where the default is VAX_Float. In addition, the
19569 predefined libraries in GNAT are built using IEEE_Float, so it is not
19570 advisable to change the format of numbers passed to standard library
19571 routines, and if necessary explicit type conversions may be needed.
19573 The use of IEEE_Float is recommended in GNAT since it is more efficient,
19574 and (given that it conforms to an international standard) potentially more
19575 portable. The situation in which VAX_Float may be useful is in interfacing
19576 to existing code and data that expects the use of VAX_Float. There are
19577 two possibilities here. If the requirement for the use of VAX_Float is
19578 localized, then the best approach is to use the predefined VAX_Float
19579 types in package @code{System}, as extended by
19580 @code{Extend_System}. For example, use @code{System.F_Float}
19581 to specify the 32-bit @code{F-Float} format.
19583 Alternatively, if an entire program depends heavily on the use of
19584 the @code{VAX_Float} and in particular assumes that the types in
19585 package @code{Standard} are in @code{Vax_Float} format, then it
19586 may be desirable to reconfigure GNAT to assume Vax_Float by default.
19587 This is done by using the GNAT LIBRARY command to rebuild the library, and
19588 then using the general form of the @code{Float_Representation}
19589 pragma to ensure that this default format is used throughout.
19590 The form of the GNAT LIBRARY command is:
19593 GNAT LIBRARY /CONFIG=@i{file} /CREATE=@i{directory}
19597 where @i{file} contains the new configuration pragmas
19598 and @i{directory} is the directory to be created to contain
19602 On OpenVMS systems, DEC Ada provides the pragma @code{Long_Float}
19603 to allow control over the internal representation chosen
19604 for the predefined type @code{Long_Float} and for floating-point
19605 type declarations with digits specified in the range 7 .. 15.
19606 The format of this pragma is as follows:
19608 @smallexample @c ada
19610 pragma Long_Float (D_FLOAT | G_FLOAT);
19614 @node Fixed-Point Types and Representations
19615 @subsection Fixed-Point Types and Representations
19618 On DEC Ada for OpenVMS Alpha systems, rounding is
19619 away from zero for both positive and negative numbers.
19620 Therefore, +0.5 rounds to 1 and -0.5 rounds to -1.
19622 On GNAT for OpenVMS Alpha, the results of operations
19623 on fixed-point types are in accordance with the Ada 95
19624 rules. In particular, results of operations on decimal
19625 fixed-point types are truncated.
19627 @node Record and Array Component Alignment
19628 @subsection Record and Array Component Alignment
19631 On DEC Ada for OpenVMS Alpha, all non composite components
19632 are aligned on natural boundaries. For example, 1-byte
19633 components are aligned on byte boundaries, 2-byte
19634 components on 2-byte boundaries, 4-byte components on 4-byte
19635 byte boundaries, and so on. The OpenVMS Alpha hardware
19636 runs more efficiently with naturally aligned data.
19638 ON GNAT for OpenVMS Alpha, alignment rules are compatible
19639 with DEC Ada for OpenVMS Alpha.
19641 @node Address Clauses
19642 @subsection Address Clauses
19645 In DEC Ada and GNAT, address clauses are supported for
19646 objects and imported subprograms.
19647 The predefined type @code{System.Address} is a private type
19648 in both compilers, with the same representation (it is simply
19649 a machine pointer). Addition, subtraction, and comparison
19650 operations are available in the standard Ada 95 package
19651 @code{System.Storage_Elements}, or in package @code{System}
19652 if it is extended to include @code{System.Aux_DEC} using a
19653 pragma @code{Extend_System} as previously described.
19655 Note that code that with's both this extended package @code{System}
19656 and the package @code{System.Storage_Elements} should not @code{use}
19657 both packages, or ambiguities will result. In general it is better
19658 not to mix these two sets of facilities. The Ada 95 package was
19659 designed specifically to provide the kind of features that DEC Ada
19660 adds directly to package @code{System}.
19662 GNAT is compatible with DEC Ada in its handling of address
19663 clauses, except for some limitations in
19664 the form of address clauses for composite objects with
19665 initialization. Such address clauses are easily replaced
19666 by the use of an explicitly-defined constant as described
19667 in the Ada 95 Reference Manual (13.1(22)). For example, the sequence
19670 @smallexample @c ada
19672 X, Y : Integer := Init_Func;
19673 Q : String (X .. Y) := "abc";
19675 for Q'Address use Compute_Address;
19680 will be rejected by GNAT, since the address cannot be computed at the time
19681 that Q is declared. To achieve the intended effect, write instead:
19683 @smallexample @c ada
19686 X, Y : Integer := Init_Func;
19687 Q_Address : constant Address := Compute_Address;
19688 Q : String (X .. Y) := "abc";
19690 for Q'Address use Q_Address;
19696 which will be accepted by GNAT (and other Ada 95 compilers), and is also
19697 backwards compatible with Ada 83. A fuller description of the restrictions
19698 on address specifications is found in the GNAT Reference Manual.
19700 @node Other Representation Clauses
19701 @subsection Other Representation Clauses
19704 GNAT supports in a compatible manner all the representation
19705 clauses supported by DEC Ada. In addition, it
19706 supports representation clause forms that are new in Ada 95
19707 including COMPONENT_SIZE and SIZE clauses for objects.
19709 @node The Package STANDARD
19710 @section The Package STANDARD
19713 The package STANDARD, as implemented by DEC Ada, is fully
19714 described in the Reference Manual for the Ada Programming
19715 Language (ANSI/MIL-STD-1815A-1983) and in the DEC Ada
19716 Language Reference Manual. As implemented by GNAT, the
19717 package STANDARD is described in the Ada 95 Reference
19720 In addition, DEC Ada supports the Latin-1 character set in
19721 the type CHARACTER. GNAT supports the Latin-1 character set
19722 in the type CHARACTER and also Unicode (ISO 10646 BMP) in
19723 the type WIDE_CHARACTER.
19725 The floating-point types supported by GNAT are those
19726 supported by DEC Ada, but defaults are different, and are controlled by
19727 pragmas. See @pxref{Floating-Point Types and Representations} for details.
19729 @node The Package SYSTEM
19730 @section The Package SYSTEM
19733 DEC Ada provides a system-specific version of the package
19734 SYSTEM for each platform on which the language ships.
19735 For the complete specification of the package SYSTEM, see
19736 Appendix F of the DEC Ada Language Reference Manual.
19738 On DEC Ada, the package SYSTEM includes the following conversion functions:
19740 @item TO_ADDRESS(INTEGER)
19742 @item TO_ADDRESS(UNSIGNED_LONGWORD)
19744 @item TO_ADDRESS(universal_integer)
19746 @item TO_INTEGER(ADDRESS)
19748 @item TO_UNSIGNED_LONGWORD(ADDRESS)
19750 @item Function IMPORT_VALUE return UNSIGNED_LONGWORD and the
19751 functions IMPORT_ADDRESS and IMPORT_LARGEST_VALUE
19755 By default, GNAT supplies a version of SYSTEM that matches
19756 the definition given in the Ada 95 Reference Manual.
19758 is a subset of the DIGITAL system definitions, which is as
19759 close as possible to the original definitions. The only difference
19760 is that the definition of SYSTEM_NAME is different:
19762 @smallexample @c ada
19765 type Name is (SYSTEM_NAME_GNAT);
19766 System_Name : constant Name := SYSTEM_NAME_GNAT;
19772 Also, GNAT adds the new Ada 95 declarations for
19773 BIT_ORDER and DEFAULT_BIT_ORDER.
19775 However, the use of the following pragma causes GNAT
19776 to extend the definition of package SYSTEM so that it
19777 encompasses the full set of DIGITAL-specific extensions,
19778 including the functions listed above:
19780 @smallexample @c ada
19782 pragma Extend_System (Aux_DEC);
19787 The pragma Extend_System is a configuration pragma that
19788 is most conveniently placed in the @file{gnat.adc} file. See the
19789 GNAT Reference Manual for further details.
19791 DEC Ada does not allow the recompilation of the package
19792 SYSTEM. Instead DEC Ada provides several pragmas (SYSTEM_
19793 NAME, STORAGE_UNIT, and MEMORY_SIZE) to modify values in
19794 the package SYSTEM. On OpenVMS Alpha systems, the pragma
19795 SYSTEM_NAME takes the enumeration literal OPENVMS_AXP as
19796 its single argument.
19798 GNAT does permit the recompilation of package SYSTEM using
19799 a special switch (@option{-gnatg}) and this switch can be used if
19800 it is necessary to modify the definitions in SYSTEM. GNAT does
19801 not permit the specification of SYSTEM_NAME, STORAGE_UNIT
19802 or MEMORY_SIZE by any other means.
19804 On GNAT systems, the pragma SYSTEM_NAME takes the
19805 enumeration literal SYSTEM_NAME_GNAT.
19807 The definitions provided by the use of
19809 @smallexample @c ada
19810 pragma Extend_System (AUX_Dec);
19814 are virtually identical to those provided by the DEC Ada 83 package
19815 System. One important difference is that the name of the TO_ADDRESS
19816 function for type UNSIGNED_LONGWORD is changed to TO_ADDRESS_LONG.
19817 See the GNAT Reference manual for a discussion of why this change was
19821 The version of TO_ADDRESS taking a universal integer argument is in fact
19822 an extension to Ada 83 not strictly compatible with the reference manual.
19823 In GNAT, we are constrained to be exactly compatible with the standard,
19824 and this means we cannot provide this capability. In DEC Ada 83, the
19825 point of this definition is to deal with a call like:
19827 @smallexample @c ada
19828 TO_ADDRESS (16#12777#);
19832 Normally, according to the Ada 83 standard, one would expect this to be
19833 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
19834 of TO_ADDRESS. However, in DEC Ada 83, there is no ambiguity, since the
19835 definition using universal_integer takes precedence.
19837 In GNAT, since the version with universal_integer cannot be supplied, it is
19838 not possible to be 100% compatible. Since there are many programs using
19839 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
19840 to change the name of the function in the UNSIGNED_LONGWORD case, so the
19841 declarations provided in the GNAT version of AUX_Dec are:
19843 @smallexample @c ada
19844 function To_Address (X : Integer) return Address;
19845 pragma Pure_Function (To_Address);
19847 function To_Address_Long (X : Unsigned_Longword) return Address;
19848 pragma Pure_Function (To_Address_Long);
19852 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
19853 change the name to TO_ADDRESS_LONG.
19855 @node Tasking and Task-Related Features
19856 @section Tasking and Task-Related Features
19859 The concepts relevant to a comparison of tasking on GNAT
19860 and on DEC Ada for OpenVMS Alpha systems are discussed in
19861 the following sections.
19863 For detailed information on concepts related to tasking in
19864 DEC Ada, see the DEC Ada Language Reference Manual and the
19865 relevant run-time reference manual.
19867 @node Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
19868 @section Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
19871 On OpenVMS Alpha systems, each Ada task (except a passive
19872 task) is implemented as a single stream of execution
19873 that is created and managed by the kernel. On these
19874 systems, DEC Ada tasking support is based on DECthreads,
19875 an implementation of the POSIX standard for threads.
19877 Although tasks are implemented as threads, all tasks in
19878 an Ada program are part of the same process. As a result,
19879 resources such as open files and virtual memory can be
19880 shared easily among tasks. Having all tasks in one process
19881 allows better integration with the programming environment
19882 (the shell and the debugger, for example).
19884 Also, on OpenVMS Alpha systems, DEC Ada tasks and foreign
19885 code that calls DECthreads routines can be used together.
19886 The interaction between Ada tasks and DECthreads routines
19887 can have some benefits. For example when on OpenVMS Alpha,
19888 DEC Ada can call C code that is already threaded.
19889 GNAT on OpenVMS Alpha uses the facilities of DECthreads,
19890 and Ada tasks are mapped to threads.
19893 * Assigning Task IDs::
19894 * Task IDs and Delays::
19895 * Task-Related Pragmas::
19896 * Scheduling and Task Priority::
19898 * External Interrupts::
19901 @node Assigning Task IDs
19902 @subsection Assigning Task IDs
19905 The DEC Ada Run-Time Library always assigns %TASK 1 to
19906 the environment task that executes the main program. On
19907 OpenVMS Alpha systems, %TASK 0 is often used for tasks
19908 that have been created but are not yet activated.
19910 On OpenVMS Alpha systems, task IDs are assigned at
19911 activation. On GNAT systems, task IDs are also assigned at
19912 task creation but do not have the same form or values as
19913 task ID values in DEC Ada. There is no null task, and the
19914 environment task does not have a specific task ID value.
19916 @node Task IDs and Delays
19917 @subsection Task IDs and Delays
19920 On OpenVMS Alpha systems, tasking delays are implemented
19921 using Timer System Services. The Task ID is used for the
19922 identification of the timer request (the REQIDT parameter).
19923 If Timers are used in the application take care not to use
19924 0 for the identification, because cancelling such a timer
19925 will cancel all timers and may lead to unpredictable results.
19927 @node Task-Related Pragmas
19928 @subsection Task-Related Pragmas
19931 Ada supplies the pragma TASK_STORAGE, which allows
19932 specification of the size of the guard area for a task
19933 stack. (The guard area forms an area of memory that has no
19934 read or write access and thus helps in the detection of
19935 stack overflow.) On OpenVMS Alpha systems, if the pragma
19936 TASK_STORAGE specifies a value of zero, a minimal guard
19937 area is created. In the absence of a pragma TASK_STORAGE, a default guard
19940 GNAT supplies the following task-related pragmas:
19945 This pragma appears within a task definition and
19946 applies to the task in which it appears. The argument
19947 must be of type SYSTEM.TASK_INFO.TASK_INFO_TYPE.
19951 GNAT implements pragma TASK_STORAGE in the same way as
19953 Both DEC Ada and GNAT supply the pragmas PASSIVE,
19954 SUPPRESS, and VOLATILE.
19956 @node Scheduling and Task Priority
19957 @subsection Scheduling and Task Priority
19960 DEC Ada implements the Ada language requirement that
19961 when two tasks are eligible for execution and they have
19962 different priorities, the lower priority task does not
19963 execute while the higher priority task is waiting. The DEC
19964 Ada Run-Time Library keeps a task running until either the
19965 task is suspended or a higher priority task becomes ready.
19967 On OpenVMS Alpha systems, the default strategy is round-
19968 robin with preemption. Tasks of equal priority take turns
19969 at the processor. A task is run for a certain period of
19970 time and then placed at the rear of the ready queue for
19971 its priority level.
19973 DEC Ada provides the implementation-defined pragma TIME_SLICE,
19974 which can be used to enable or disable round-robin
19975 scheduling of tasks with the same priority.
19976 See the relevant DEC Ada run-time reference manual for
19977 information on using the pragmas to control DEC Ada task
19980 GNAT follows the scheduling rules of Annex D (real-time
19981 Annex) of the Ada 95 Reference Manual. In general, this
19982 scheduling strategy is fully compatible with DEC Ada
19983 although it provides some additional constraints (as
19984 fully documented in Annex D).
19985 GNAT implements time slicing control in a manner compatible with
19986 DEC Ada 83, by means of the pragma Time_Slice, whose semantics are identical
19987 to the DEC Ada 83 pragma of the same name.
19988 Note that it is not possible to mix GNAT tasking and
19989 DEC Ada 83 tasking in the same program, since the two run times are
19992 @node The Task Stack
19993 @subsection The Task Stack
19996 In DEC Ada, a task stack is allocated each time a
19997 non passive task is activated. As soon as the task is
19998 terminated, the storage for the task stack is deallocated.
19999 If you specify a size of zero (bytes) with T'STORAGE_SIZE,
20000 a default stack size is used. Also, regardless of the size
20001 specified, some additional space is allocated for task
20002 management purposes. On OpenVMS Alpha systems, at least
20003 one page is allocated.
20005 GNAT handles task stacks in a similar manner. According to
20006 the Ada 95 rules, it provides the pragma STORAGE_SIZE as
20007 an alternative method for controlling the task stack size.
20008 The specification of the attribute T'STORAGE_SIZE is also
20009 supported in a manner compatible with DEC Ada.
20011 @node External Interrupts
20012 @subsection External Interrupts
20015 On DEC Ada, external interrupts can be associated with task entries.
20016 GNAT is compatible with DEC Ada in its handling of external interrupts.
20018 @node Pragmas and Pragma-Related Features
20019 @section Pragmas and Pragma-Related Features
20022 Both DEC Ada and GNAT supply all language-defined pragmas
20023 as specified by the Ada 83 standard. GNAT also supplies all
20024 language-defined pragmas specified in the Ada 95 Reference Manual.
20025 In addition, GNAT implements the implementation-defined pragmas
20031 @item COMMON_OBJECT
20033 @item COMPONENT_ALIGNMENT
20035 @item EXPORT_EXCEPTION
20037 @item EXPORT_FUNCTION
20039 @item EXPORT_OBJECT
20041 @item EXPORT_PROCEDURE
20043 @item EXPORT_VALUED_PROCEDURE
20045 @item FLOAT_REPRESENTATION
20049 @item IMPORT_EXCEPTION
20051 @item IMPORT_FUNCTION
20053 @item IMPORT_OBJECT
20055 @item IMPORT_PROCEDURE
20057 @item IMPORT_VALUED_PROCEDURE
20059 @item INLINE_GENERIC
20061 @item INTERFACE_NAME
20071 @item SHARE_GENERIC
20083 These pragmas are all fully implemented, with the exception of @code{Title},
20084 @code{Passive}, and @code{Share_Generic}, which are
20085 recognized, but which have no
20086 effect in GNAT. The effect of @code{Passive} may be obtained by the
20087 use of protected objects in Ada 95. In GNAT, all generics are inlined.
20089 Unlike DEC Ada, the GNAT 'EXPORT_@i{subprogram}' pragmas require
20090 a separate subprogram specification which must appear before the
20093 GNAT also supplies a number of implementation-defined pragmas as follows:
20095 @item C_PASS_BY_COPY
20097 @item EXTEND_SYSTEM
20099 @item SOURCE_FILE_NAME
20117 @item CPP_CONSTRUCTOR
20119 @item CPP_DESTRUCTOR
20129 @item LINKER_SECTION
20131 @item MACHINE_ATTRIBUTE
20135 @item PURE_FUNCTION
20137 @item SOURCE_REFERENCE
20141 @item UNCHECKED_UNION
20143 @item UNIMPLEMENTED_UNIT
20145 @item UNIVERSAL_DATA
20147 @item WEAK_EXTERNAL
20151 For full details on these GNAT implementation-defined pragmas, see
20152 the GNAT Reference Manual.
20155 * Restrictions on the Pragma INLINE::
20156 * Restrictions on the Pragma INTERFACE::
20157 * Restrictions on the Pragma SYSTEM_NAME::
20160 @node Restrictions on the Pragma INLINE
20161 @subsection Restrictions on the Pragma INLINE
20164 DEC Ada applies the following restrictions to the pragma INLINE:
20166 @item Parameters cannot be a task type.
20168 @item Function results cannot be task types, unconstrained
20169 array types, or unconstrained types with discriminants.
20171 @item Bodies cannot declare the following:
20173 @item Subprogram body or stub (imported subprogram is allowed)
20177 @item Generic declarations
20179 @item Instantiations
20183 @item Access types (types derived from access types allowed)
20185 @item Array or record types
20187 @item Dependent tasks
20189 @item Direct recursive calls of subprogram or containing
20190 subprogram, directly or via a renaming
20196 In GNAT, the only restriction on pragma INLINE is that the
20197 body must occur before the call if both are in the same
20198 unit, and the size must be appropriately small. There are
20199 no other specific restrictions which cause subprograms to
20200 be incapable of being inlined.
20202 @node Restrictions on the Pragma INTERFACE
20203 @subsection Restrictions on the Pragma INTERFACE
20206 The following lists and describes the restrictions on the
20207 pragma INTERFACE on DEC Ada and GNAT:
20209 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
20210 Default is the default on OpenVMS Alpha systems.
20212 @item Parameter passing: Language specifies default
20213 mechanisms but can be overridden with an EXPORT pragma.
20216 @item Ada: Use internal Ada rules.
20218 @item Bliss, C: Parameters must be mode @code{in}; cannot be
20219 record or task type. Result cannot be a string, an
20220 array, or a record.
20222 @item Fortran: Parameters cannot be a task. Result cannot
20223 be a string, an array, or a record.
20228 GNAT is entirely upwards compatible with DEC Ada, and in addition allows
20229 record parameters for all languages.
20231 @node Restrictions on the Pragma SYSTEM_NAME
20232 @subsection Restrictions on the Pragma SYSTEM_NAME
20235 For DEC Ada for OpenVMS Alpha, the enumeration literal
20236 for the type NAME is OPENVMS_AXP. In GNAT, the enumeration
20237 literal for the type NAME is SYSTEM_NAME_GNAT.
20239 @node Library of Predefined Units
20240 @section Library of Predefined Units
20243 A library of predefined units is provided as part of the
20244 DEC Ada and GNAT implementations. DEC Ada does not provide
20245 the package MACHINE_CODE but instead recommends importing
20248 The GNAT versions of the DEC Ada Run-Time Library (ADA$PREDEFINED:)
20249 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
20250 version. During GNAT installation, the DEC Ada Predefined
20251 Library units are copied into the GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
20252 (aka DECLIB) directory and patched to remove Ada 95 incompatibilities
20253 and to make them interoperable with GNAT, @pxref{Changes to DECLIB}
20256 The GNAT RTL is contained in
20257 the GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB] (aka ADALIB) directory and
20258 the default search path is set up to find DECLIB units in preference
20259 to ADALIB units with the same name (TEXT_IO, SEQUENTIAL_IO, and DIRECT_IO,
20262 However, it is possible to change the default so that the
20263 reverse is true, or even to mix them using child package
20264 notation. The DEC Ada 83 units are available as DEC.xxx where xxx
20265 is the package name, and the Ada units are available in the
20266 standard manner defined for Ada 95, that is to say as Ada.xxx. To
20267 change the default, set ADA_INCLUDE_PATH and ADA_OBJECTS_PATH
20268 appropriately. For example, to change the default to use the Ada95
20272 $ DEFINE ADA_INCLUDE_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADAINCLUDE],-
20273 GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
20274 $ DEFINE ADA_OBJECTS_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB],-
20275 GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
20279 * Changes to DECLIB::
20282 @node Changes to DECLIB
20283 @subsection Changes to DECLIB
20286 The changes made to the DEC Ada predefined library for GNAT and Ada 95
20287 compatibility are minor and include the following:
20290 @item Adjusting the location of pragmas and record representation
20291 clauses to obey Ada 95 rules
20293 @item Adding the proper notation to generic formal parameters
20294 that take unconstrained types in instantiation
20296 @item Adding pragma ELABORATE_BODY to package specifications
20297 that have package bodies not otherwise allowed
20299 @item Occurrences of the identifier @code{"PROTECTED"} are renamed to
20301 Currently these are found only in the STARLET package spec.
20305 None of the above changes is visible to users.
20311 On OpenVMS Alpha, DEC Ada provides the following strongly-typed bindings:
20314 @item Command Language Interpreter (CLI interface)
20316 @item DECtalk Run-Time Library (DTK interface)
20318 @item Librarian utility routines (LBR interface)
20320 @item General Purpose Run-Time Library (LIB interface)
20322 @item Math Run-Time Library (MTH interface)
20324 @item National Character Set Run-Time Library (NCS interface)
20326 @item Compiled Code Support Run-Time Library (OTS interface)
20328 @item Parallel Processing Run-Time Library (PPL interface)
20330 @item Screen Management Run-Time Library (SMG interface)
20332 @item Sort Run-Time Library (SOR interface)
20334 @item String Run-Time Library (STR interface)
20336 @item STARLET System Library
20339 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
20341 @item X Windows Toolkit (XT interface)
20343 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
20347 GNAT provides implementations of these DEC bindings in the DECLIB directory.
20349 The X/Motif bindings used to build DECLIB are whatever versions are in the
20350 DEC Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
20351 The build script will
20352 automatically add a pragma Linker_Options to packages @code{Xm}, @code{Xt},
20354 causing the default X/Motif sharable image libraries to be linked in. This
20355 is done via options files named @file{xm.opt}, @file{xt.opt}, and
20356 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
20358 It may be necessary to edit these options files to update or correct the
20359 library names if, for example, the newer X/Motif bindings from
20360 @file{ADA$EXAMPLES}
20361 had been (previous to installing GNAT) copied and renamed to supersede the
20362 default @file{ADA$PREDEFINED} versions.
20365 * Shared Libraries and Options Files::
20366 * Interfaces to C::
20369 @node Shared Libraries and Options Files
20370 @subsection Shared Libraries and Options Files
20373 When using the DEC Ada
20374 predefined X and Motif bindings, the linking with their sharable images is
20375 done automatically by @command{GNAT LINK}.
20376 When using other X and Motif bindings, you need
20377 to add the corresponding sharable images to the command line for
20378 @code{GNAT LINK}. When linking with shared libraries, or with
20379 @file{.OPT} files, you must
20380 also add them to the command line for @command{GNAT LINK}.
20382 A shared library to be used with GNAT is built in the same way as other
20383 libraries under VMS. The VMS Link command can be used in standard fashion.
20385 @node Interfaces to C
20386 @subsection Interfaces to C
20390 provides the following Ada types and operations:
20393 @item C types package (C_TYPES)
20395 @item C strings (C_TYPES.NULL_TERMINATED)
20397 @item Other_types (SHORT_INT)
20401 Interfacing to C with GNAT, one can use the above approach
20402 described for DEC Ada or the facilities of Annex B of
20403 the Ada 95 Reference Manual (packages INTERFACES.C,
20404 INTERFACES.C.STRINGS and INTERFACES.C.POINTERS). For more
20405 information, see the section ``Interfacing to C'' in the
20406 @cite{GNAT Reference Manual}.
20408 The @option{-gnatF} qualifier forces default and explicit
20409 @code{External_Name} parameters in pragmas Import and Export
20410 to be uppercased for compatibility with the default behavior
20411 of Compaq C. The qualifier has no effect on @code{Link_Name} parameters.
20413 @node Main Program Definition
20414 @section Main Program Definition
20417 The following section discusses differences in the
20418 definition of main programs on DEC Ada and GNAT.
20419 On DEC Ada, main programs are defined to meet the
20420 following conditions:
20422 @item Procedure with no formal parameters (returns 0 upon
20425 @item Procedure with no formal parameters (returns 42 when
20426 unhandled exceptions are raised)
20428 @item Function with no formal parameters whose returned value
20429 is of a discrete type
20431 @item Procedure with one OUT formal of a discrete type for
20432 which a specification of pragma EXPORT_VALUED_PROCEDURE is given.
20437 When declared with the pragma EXPORT_VALUED_PROCEDURE,
20438 a main function or main procedure returns a discrete
20439 value whose size is less than 64 bits (32 on VAX systems),
20440 the value is zero- or sign-extended as appropriate.
20441 On GNAT, main programs are defined as follows:
20443 @item Must be a non-generic, parameter-less subprogram that
20444 is either a procedure or function returning an Ada
20445 STANDARD.INTEGER (the predefined type)
20447 @item Cannot be a generic subprogram or an instantiation of a
20451 @node Implementation-Defined Attributes
20452 @section Implementation-Defined Attributes
20455 GNAT provides all DEC Ada implementation-defined
20458 @node Compiler and Run-Time Interfacing
20459 @section Compiler and Run-Time Interfacing
20462 DEC Ada provides the following ways to pass options to the linker
20465 @item /WAIT and /SUBMIT qualifiers
20467 @item /COMMAND qualifier
20469 @item /[NO]MAP qualifier
20471 @item /OUTPUT=file-spec
20473 @item /[NO]DEBUG and /[NO]TRACEBACK qualifiers
20477 To pass options to the linker, GNAT provides the following
20481 @item @option{/EXECUTABLE=exec-name}
20483 @item @option{/VERBOSE qualifier}
20485 @item @option{/[NO]DEBUG} and @option{/[NO]TRACEBACK} qualifiers
20489 For more information on these switches, see
20490 @ref{Switches for gnatlink}.
20491 In DEC Ada, the command-line switch @option{/OPTIMIZE} is available
20492 to control optimization. DEC Ada also supplies the
20495 @item @code{OPTIMIZE}
20497 @item @code{INLINE}
20499 @item @code{INLINE_GENERIC}
20501 @item @code{SUPPRESS_ALL}
20503 @item @code{PASSIVE}
20507 In GNAT, optimization is controlled strictly by command
20508 line parameters, as described in the corresponding section of this guide.
20509 The DIGITAL pragmas for control of optimization are
20510 recognized but ignored.
20512 Note that in GNAT, the default is optimization off, whereas in DEC Ada 83,
20513 the default is that optimization is turned on.
20515 @node Program Compilation and Library Management
20516 @section Program Compilation and Library Management
20519 DEC Ada and GNAT provide a comparable set of commands to
20520 build programs. DEC Ada also provides a program library,
20521 which is a concept that does not exist on GNAT. Instead,
20522 GNAT provides directories of sources that are compiled as
20525 The following table summarizes
20526 the DEC Ada commands and provides
20527 equivalent GNAT commands. In this table, some GNAT
20528 equivalents reflect the fact that GNAT does not use the
20529 concept of a program library. Instead, it uses a model
20530 in which collections of source and object files are used
20531 in a manner consistent with other languages like C and
20532 Fortran. Therefore, standard system file commands are used
20533 to manipulate these elements. Those GNAT commands are marked with
20535 Note that, unlike DEC Ada, none of the GNAT commands accepts wild cards.
20538 @multitable @columnfractions .35 .65
20540 @item @emph{DEC Ada Command}
20541 @tab @emph{GNAT Equivalent / Description}
20543 @item @command{ADA}
20544 @tab @command{GNAT COMPILE}@*
20545 Invokes the compiler to compile one or more Ada source files.
20547 @item @command{ACS ATTACH}@*
20548 @tab [No equivalent]@*
20549 Switches control of terminal from current process running the program
20552 @item @command{ACS CHECK}
20553 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
20554 Forms the execution closure of one
20555 or more compiled units and checks completeness and currency.
20557 @item @command{ACS COMPILE}
20558 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20559 Forms the execution closure of one or
20560 more specified units, checks completeness and currency,
20561 identifies units that have revised source files, compiles same,
20562 and recompiles units that are or will become obsolete.
20563 Also completes incomplete generic instantiations.
20565 @item @command{ACS COPY FOREIGN}
20567 Copies a foreign object file into the program library as a
20570 @item @command{ACS COPY UNIT}
20572 Copies a compiled unit from one program library to another.
20574 @item @command{ACS CREATE LIBRARY}
20575 @tab Create /directory (*)@*
20576 Creates a program library.
20578 @item @command{ACS CREATE SUBLIBRARY}
20579 @tab Create /directory (*)@*
20580 Creates a program sublibrary.
20582 @item @command{ACS DELETE LIBRARY}
20584 Deletes a program library and its contents.
20586 @item @command{ACS DELETE SUBLIBRARY}
20588 Deletes a program sublibrary and its contents.
20590 @item @command{ACS DELETE UNIT}
20591 @tab Delete file (*)@*
20592 On OpenVMS systems, deletes one or more compiled units from
20593 the current program library.
20595 @item @command{ACS DIRECTORY}
20596 @tab Directory (*)@*
20597 On OpenVMS systems, lists units contained in the current
20600 @item @command{ACS ENTER FOREIGN}
20602 Allows the import of a foreign body as an Ada library
20603 specification and enters a reference to a pointer.
20605 @item @command{ACS ENTER UNIT}
20607 Enters a reference (pointer) from the current program library to
20608 a unit compiled into another program library.
20610 @item @command{ACS EXIT}
20611 @tab [No equivalent]@*
20612 Exits from the program library manager.
20614 @item @command{ACS EXPORT}
20616 Creates an object file that contains system-specific object code
20617 for one or more units. With GNAT, object files can simply be copied
20618 into the desired directory.
20620 @item @command{ACS EXTRACT SOURCE}
20622 Allows access to the copied source file for each Ada compilation unit
20624 @item @command{ACS HELP}
20625 @tab @command{HELP GNAT}@*
20626 Provides online help.
20628 @item @command{ACS LINK}
20629 @tab @command{GNAT LINK}@*
20630 Links an object file containing Ada units into an executable file.
20632 @item @command{ACS LOAD}
20634 Loads (partially compiles) Ada units into the program library.
20635 Allows loading a program from a collection of files into a library
20636 without knowing the relationship among units.
20638 @item @command{ACS MERGE}
20640 Merges into the current program library, one or more units from
20641 another library where they were modified.
20643 @item @command{ACS RECOMPILE}
20644 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20645 Recompiles from external or copied source files any obsolete
20646 unit in the closure. Also, completes any incomplete generic
20649 @item @command{ACS REENTER}
20650 @tab @command{GNAT MAKE}@*
20651 Reenters current references to units compiled after last entered
20652 with the @command{ACS ENTER UNIT} command.
20654 @item @command{ACS SET LIBRARY}
20655 @tab Set default (*)@*
20656 Defines a program library to be the compilation context as well
20657 as the target library for compiler output and commands in general.
20659 @item @command{ACS SET PRAGMA}
20660 @tab Edit @file{gnat.adc} (*)@*
20661 Redefines specified values of the library characteristics
20662 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
20663 and @code{Float_Representation}.
20665 @item @command{ACS SET SOURCE}
20666 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
20667 Defines the source file search list for the @command{ACS COMPILE} command.
20669 @item @command{ACS SHOW LIBRARY}
20670 @tab Directory (*)@*
20671 Lists information about one or more program libraries.
20673 @item @command{ACS SHOW PROGRAM}
20674 @tab [No equivalent]@*
20675 Lists information about the execution closure of one or
20676 more units in the program library.
20678 @item @command{ACS SHOW SOURCE}
20679 @tab Show logical @code{ADA_INCLUDE_PATH}@*
20680 Shows the source file search used when compiling units.
20682 @item @command{ACS SHOW VERSION}
20683 @tab Compile with @option{VERBOSE} option
20684 Displays the version number of the compiler and program library
20687 @item @command{ACS SPAWN}
20688 @tab [No equivalent]@*
20689 Creates a subprocess of the current process (same as @command{DCL SPAWN}
20692 @item @command{ACS VERIFY}
20693 @tab [No equivalent]@*
20694 Performs a series of consistency checks on a program library to
20695 determine whether the library structure and library files are in
20702 @section Input-Output
20705 On OpenVMS Alpha systems, DEC Ada uses OpenVMS Record
20706 Management Services (RMS) to perform operations on
20710 DEC Ada and GNAT predefine an identical set of input-
20711 output packages. To make the use of the
20712 generic TEXT_IO operations more convenient, DEC Ada
20713 provides predefined library packages that instantiate the
20714 integer and floating-point operations for the predefined
20715 integer and floating-point types as shown in the following table.
20717 @multitable @columnfractions .45 .55
20718 @item @emph{Package Name} @tab Instantiation
20720 @item @code{INTEGER_TEXT_IO}
20721 @tab @code{INTEGER_IO(INTEGER)}
20723 @item @code{SHORT_INTEGER_TEXT_IO}
20724 @tab @code{INTEGER_IO(SHORT_INTEGER)}
20726 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
20727 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
20729 @item @code{FLOAT_TEXT_IO}
20730 @tab @code{FLOAT_IO(FLOAT)}
20732 @item @code{LONG_FLOAT_TEXT_IO}
20733 @tab @code{FLOAT_IO(LONG_FLOAT)}
20737 The DEC Ada predefined packages and their operations
20738 are implemented using OpenVMS Alpha files and input-
20739 output facilities. DEC Ada supports asynchronous input-
20740 output on OpenVMS Alpha. Familiarity with the following is
20743 @item RMS file organizations and access methods
20745 @item OpenVMS file specifications and directories
20747 @item OpenVMS File Definition Language (FDL)
20751 GNAT provides I/O facilities that are completely
20752 compatible with DEC Ada. The distribution includes the
20753 standard DEC Ada versions of all I/O packages, operating
20754 in a manner compatible with DEC Ada. In particular, the
20755 following packages are by default the DEC Ada (Ada 83)
20756 versions of these packages rather than the renamings
20757 suggested in annex J of the Ada 95 Reference Manual:
20759 @item @code{TEXT_IO}
20761 @item @code{SEQUENTIAL_IO}
20763 @item @code{DIRECT_IO}
20767 The use of the standard Ada 95 syntax for child packages (for
20768 example, @code{ADA.TEXT_IO}) retrieves the Ada 95 versions of these
20769 packages, as defined in the Ada 95 Reference Manual.
20770 GNAT provides DIGITAL-compatible predefined instantiations
20771 of the @code{TEXT_IO} packages, and also
20772 provides the standard predefined instantiations required
20773 by the Ada 95 Reference Manual.
20775 For further information on how GNAT interfaces to the file
20776 system or how I/O is implemented in programs written in
20777 mixed languages, see the chapter ``Implementation of the
20778 Standard I/O'' in the @cite{GNAT Reference Manual}.
20779 This chapter covers the following:
20781 @item Standard I/O packages
20783 @item @code{FORM} strings
20785 @item @code{ADA.DIRECT_IO}
20787 @item @code{ADA.SEQUENTIAL_IO}
20789 @item @code{ADA.TEXT_IO}
20791 @item Stream pointer positioning
20793 @item Reading and writing non-regular files
20795 @item @code{GET_IMMEDIATE}
20797 @item Treating @code{TEXT_IO} files as streams
20804 @node Implementation Limits
20805 @section Implementation Limits
20808 The following table lists implementation limits for DEC Ada
20810 @multitable @columnfractions .60 .20 .20
20812 @item @emph{Compilation Parameter}
20813 @tab @emph{DEC Ada}
20817 @item In a subprogram or entry declaration, maximum number of
20818 formal parameters that are of an unconstrained record type
20823 @item Maximum identifier length (number of characters)
20828 @item Maximum number of characters in a source line
20833 @item Maximum collection size (number of bytes)
20838 @item Maximum number of discriminants for a record type
20843 @item Maximum number of formal parameters in an entry or
20844 subprogram declaration
20849 @item Maximum number of dimensions in an array type
20854 @item Maximum number of library units and subunits in a compilation.
20859 @item Maximum number of library units and subunits in an execution.
20864 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
20865 or @code{PSECT_OBJECT}
20870 @item Maximum number of enumeration literals in an enumeration type
20876 @item Maximum number of lines in a source file
20881 @item Maximum number of bits in any object
20886 @item Maximum size of the static portion of a stack frame (approximate)
20897 @c **************************************
20898 @node Platform-Specific Information for the Run-Time Libraries
20899 @appendix Platform-Specific Information for the Run-Time Libraries
20900 @cindex Tasking and threads libraries
20901 @cindex Threads libraries and tasking
20902 @cindex Run-time libraries (platform-specific information)
20905 The GNAT run-time implementation
20906 may vary with respect to both the underlying threads library and
20907 the exception handling scheme.
20908 For threads support, one or more of the following are supplied:
20910 @item @b{native threads library}, a binding to the thread package from
20911 the underlying operating system
20913 @item @b{FSU threads library}, a binding to the Florida State University
20914 threads implementation, which complies fully with the requirements of Annex D
20916 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
20917 POSIX thread package
20921 For exception handling, either or both of two models are supplied:
20923 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
20924 Most programs should experience a substantial speed improvement by
20925 being compiled with a ZCX run-time.
20926 This is especially true for
20927 tasking applications or applications with many exception handlers.}
20928 @cindex Zero-Cost Exceptions
20929 @cindex ZCX (Zero-Cost Exceptions)
20930 which uses binder-generated tables that
20931 are interrogated at run time to locate a handler
20933 @item @b{setjmp / longjmp} (``SJLJ''),
20934 @cindex setjmp/longjmp Exception Model
20935 @cindex SJLJ (setjmp/longjmp Exception Model)
20936 which uses dynamically-set data to establish
20937 the set of handlers
20941 This appendix summarizes which combinations of threads and exception support
20942 are supplied on various GNAT platforms.
20943 It then shows how to select a particular library either
20944 permanently or temporarily,
20945 explains the properties of (and tradeoffs among) the various threads
20946 libraries, and provides some additional
20947 information about several specific platforms.
20950 * Summary of Run-Time Configurations::
20951 * Specifying a Run-Time Library::
20952 * Choosing between Native and FSU Threads Libraries::
20953 * Choosing the Scheduling Policy::
20954 * Solaris-Specific Considerations::
20955 * IRIX-Specific Considerations::
20956 * Linux-Specific Considerations::
20957 * AIX-Specific Considerations::
20961 @node Summary of Run-Time Configurations
20962 @section Summary of Run-Time Configurations
20965 @multitable @columnfractions .30 .70
20966 @item @b{alpha-openvms}
20967 @item @code{@ @ }@i{rts-native (default)}
20968 @item @code{@ @ @ @ }Tasking @tab native VMS threads
20969 @item @code{@ @ @ @ }Exceptions @tab ZCX
20972 @item @code{@ @ }@i{rts-native (default)}
20973 @item @code{@ @ @ @ }Tasking @tab native HP threads library
20974 @item @code{@ @ @ @ }Exceptions @tab ZCX
20976 @item @code{@ @ }@i{rts-sjlj}
20977 @item @code{@ @ @ @ }Tasking @tab native HP threads library
20978 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20980 @item @b{sparc-solaris} @tab
20981 @item @code{@ @ }@i{rts-native (default)}
20982 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20983 @item @code{@ @ @ @ }Exceptions @tab ZCX
20985 @item @code{@ @ }@i{rts-fsu} @tab
20986 @item @code{@ @ @ @ }Tasking @tab FSU threads library
20987 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20989 @item @code{@ @ }@i{rts-m64}
20990 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20991 @item @code{@ @ @ @ }Exceptions @tab ZCX
20992 @item @code{@ @ @ @ }Constraints @tab Use only when compiling in 64-bit mode;
20993 @item @tab Use only on Solaris 8 or later.
20994 @item @tab @xref{Building and Debugging 64-bit Applications}, for details.
20996 @item @code{@ @ }@i{rts-pthread}
20997 @item @code{@ @ @ @ }Tasking @tab pthreads library
20998 @item @code{@ @ @ @ }Exceptions @tab ZCX
21000 @item @code{@ @ }@i{rts-sjlj}
21001 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21002 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21004 @item @b{x86-linux}
21005 @item @code{@ @ }@i{rts-native (default)}
21006 @item @code{@ @ @ @ }Tasking @tab LinuxThread library
21007 @item @code{@ @ @ @ }Exceptions @tab ZCX
21009 @item @code{@ @ }@i{rts-fsu}
21010 @item @code{@ @ @ @ }Tasking @tab FSU threads library
21011 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21013 @item @code{@ @ }@i{rts-sjlj}
21014 @item @code{@ @ @ @ }Tasking @tab LinuxThread library
21015 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21017 @item @b{x86-windows}
21018 @item @code{@ @ }@i{rts-native (default)}
21019 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
21020 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21026 @node Specifying a Run-Time Library
21027 @section Specifying a Run-Time Library
21030 The @file{adainclude} subdirectory containing the sources of the GNAT
21031 run-time library, and the @file{adalib} subdirectory containing the
21032 @file{ALI} files and the static and/or shared GNAT library, are located
21033 in the gcc target-dependent area:
21036 target=$prefix/lib/gcc-lib/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
21040 As indicated above, on some platforms several run-time libraries are supplied.
21041 These libraries are installed in the target dependent area and
21042 contain a complete source and binary subdirectory. The detailed description
21043 below explains the differences between the different libraries in terms of
21044 their thread support.
21046 The default run-time library (when GNAT is installed) is @emph{rts-native}.
21047 This default run time is selected by the means of soft links.
21048 For example on x86-linux:
21054 +--- adainclude----------+
21056 +--- adalib-----------+ |
21058 +--- rts-native | |
21060 | +--- adainclude <---+
21062 | +--- adalib <----+
21079 If the @i{rts-fsu} library is to be selected on a permanent basis,
21080 these soft links can be modified with the following commands:
21084 $ rm -f adainclude adalib
21085 $ ln -s rts-fsu/adainclude adainclude
21086 $ ln -s rts-fsu/adalib adalib
21090 Alternatively, you can specify @file{rts-fsu/adainclude} in the file
21091 @file{$target/ada_source_path} and @file{rts-fsu/adalib} in
21092 @file{$target/ada_object_path}.
21094 Selecting another run-time library temporarily can be
21095 achieved by the regular mechanism for GNAT object or source path selection:
21099 Set the environment variables:
21102 $ ADA_INCLUDE_PATH=$target/rts-fsu/adainclude:$ADA_INCLUDE_PATH
21103 $ ADA_OBJECTS_PATH=$target/rts-fsu/adalib:$ADA_OBJECTS_PATH
21104 $ export ADA_INCLUDE_PATH ADA_OBJECTS_PATH
21108 Use @option{-aI$target/rts-fsu/adainclude}
21109 and @option{-aO$target/rts-fsu/adalib}
21110 on the @command{gnatmake} command line
21113 Use the switch @option{--RTS}; e.g., @option{--RTS=fsu}
21114 @cindex @option{--RTS} option
21118 You can similarly switch to @emph{rts-sjlj}.
21120 @node Choosing between Native and FSU Threads Libraries
21121 @section Choosing between Native and FSU Threads Libraries
21122 @cindex Native threads library
21123 @cindex FSU threads library
21126 Some GNAT implementations offer a choice between
21127 native threads and FSU threads.
21131 The @emph{native threads} library correspond to the standard system threads
21132 implementation (e.g. LinuxThreads on GNU/Linux,
21133 @cindex LinuxThreads library
21134 POSIX threads on AIX, or
21135 Solaris threads on Solaris). When this option is chosen, GNAT provides
21136 a full and accurate implementation of the core language tasking model
21137 as described in Chapter 9 of the Ada Reference Manual,
21138 but might not (and probably does not) implement
21139 the exact semantics as specified in @w{Annex D} (the Real-Time Systems Annex).
21140 @cindex Annex D (Real-Time Systems Annex) compliance
21141 @cindex Real-Time Systems Annex compliance
21142 Indeed, the reason that a choice of libraries is offered
21143 on a given target is because some of the
21144 ACATS tests for @w{Annex D} fail using the native threads library.
21145 As far as possible, this library is implemented
21146 in accordance with Ada semantics (e.g., modifying priorities as required
21147 to simulate ceiling locking),
21148 but there are often slight inaccuracies, most often in the area of
21149 absolutely respecting the priority rules on a single
21151 Moreover, it is not possible in general to define the exact behavior,
21152 because the native threads implementations
21153 are not well enough documented.
21155 On systems where the @code{SCHED_FIFO} POSIX scheduling policy is supported,
21156 @cindex POSIX scheduling policies
21157 @cindex @code{SCHED_FIFO} scheduling policy
21158 native threads will provide a behavior very close to the @w{Annex D}
21159 requirements (i.e., a run-till-blocked scheduler with fixed priorities), but
21160 on some systems (in particular GNU/Linux and Solaris), you need to have root
21161 privileges to use the @code{SCHED_FIFO} policy.
21164 The @emph{FSU threads} library provides a completely accurate implementation
21166 Thus, operating with this library, GNAT is 100% compliant with both the core
21167 and all @w{Annex D}
21169 The formal validations for implementations offering
21170 a choice of threads packages are always carried out using the FSU
21175 From these considerations, it might seem that FSU threads are the
21177 but that is by no means always the case. The FSU threads package
21178 operates with all Ada tasks appearing to the system to be a single
21179 thread. This is often considerably more efficient than operating
21180 with separate threads, since for example, switching between tasks
21181 can be accomplished without the (in some cases considerable)
21182 overhead of a context switch between two system threads. However,
21183 it means that you may well lose concurrency at the system
21184 level. Notably, some system operations (such as I/O) may block all
21185 tasks in a program and not just the calling task. More
21186 significantly, the FSU threads approach likely means you cannot
21187 take advantage of multiple processors, since for this you need
21188 separate threads (or even separate processes) to operate on
21189 different processors.
21191 For most programs, the native threads library is
21192 usually the better choice. Use the FSU threads if absolute
21193 conformance to @w{Annex D} is important for your application, or if
21194 you find that the improved efficiency of FSU threads is significant to you.
21196 Note also that to take full advantage of Florist and Glade, it is highly
21197 recommended that you use native threads.
21200 @node Choosing the Scheduling Policy
21201 @section Choosing the Scheduling Policy
21204 When using a POSIX threads implementation, you have a choice of several
21205 scheduling policies: @code{SCHED_FIFO},
21206 @cindex @code{SCHED_FIFO} scheduling policy
21208 @cindex @code{SCHED_RR} scheduling policy
21209 and @code{SCHED_OTHER}.
21210 @cindex @code{SCHED_OTHER} scheduling policy
21211 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
21212 or @code{SCHED_RR} requires special (e.g., root) privileges.
21214 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
21216 @cindex @code{SCHED_FIFO} scheduling policy
21217 you can use one of the following:
21221 @code{pragma Time_Slice (0.0)}
21222 @cindex pragma Time_Slice
21224 the corresponding binder option @option{-T0}
21225 @cindex @option{-T0} option
21227 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
21228 @cindex pragma Task_Dispatching_Policy
21232 To specify @code{SCHED_RR},
21233 @cindex @code{SCHED_RR} scheduling policy
21234 you should use @code{pragma Time_Slice} with a
21235 value greater than @code{0.0}, or else use the corresponding @option{-T}
21240 @node Solaris-Specific Considerations
21241 @section Solaris-Specific Considerations
21242 @cindex Solaris Sparc threads libraries
21245 This section addresses some topics related to the various threads libraries
21246 on Sparc Solaris and then provides some information on building and
21247 debugging 64-bit applications.
21250 * Solaris Threads Issues::
21251 * Building and Debugging 64-bit Applications::
21255 @node Solaris Threads Issues
21256 @subsection Solaris Threads Issues
21259 Starting with version 3.14, GNAT under Solaris comes with a new tasking
21260 run-time library based on POSIX threads --- @emph{rts-pthread}.
21261 @cindex rts-pthread threads library
21262 This run-time library has the advantage of being mostly shared across all
21263 POSIX-compliant thread implementations, and it also provides under
21264 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
21265 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
21266 and @code{PTHREAD_PRIO_PROTECT}
21267 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
21268 semantics that can be selected using the predefined pragma
21269 @code{Locking_Policy}
21270 @cindex pragma Locking_Policy (under rts-pthread)
21272 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
21273 @cindex @code{Inheritance_Locking} (under rts-pthread)
21274 @cindex @code{Ceiling_Locking} (under rts-pthread)
21276 As explained above, the native run-time library is based on the Solaris thread
21277 library (@code{libthread}) and is the default library.
21278 The FSU run-time library is based on the FSU threads.
21279 @cindex FSU threads library
21281 Starting with Solaris 2.5.1, when the Solaris threads library is used
21282 (this is the default), programs
21283 compiled with GNAT can automatically take advantage of
21284 and can thus execute on multiple processors.
21285 The user can alternatively specify a processor on which the program should run
21286 to emulate a single-processor system. The multiprocessor / uniprocessor choice
21288 setting the environment variable @code{GNAT_PROCESSOR}
21289 @cindex @code{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
21290 to one of the following:
21294 Use the default configuration (run the program on all
21295 available processors) - this is the same as having
21296 @code{GNAT_PROCESSOR} unset
21299 Let the run-time implementation choose one processor and run the program on
21302 @item 0 .. Last_Proc
21303 Run the program on the specified processor.
21304 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
21305 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
21309 @node Building and Debugging 64-bit Applications
21310 @subsection Building and Debugging 64-bit Applications
21313 In a 64-bit application, all the sources involved must be compiled with the
21314 @option{-m64} command-line option, and a specific GNAT library (compiled with
21315 this option) is required.
21316 The easiest way to build a 64bit application is to add
21317 @option{-m64 --RTS=m64} to the @command{gnatmake} flags.
21319 To debug these applications, dwarf-2 debug information is required, so you
21320 have to add @option{-gdwarf-2} to your gnatmake arguments.
21321 In addition, a special
21322 version of gdb, called @command{gdb64}, needs to be used.
21324 To summarize, building and debugging a ``Hello World'' program in 64-bit mode
21328 $ gnatmake -m64 -gdwarf-2 --RTS=m64 hello.adb
21334 @node IRIX-Specific Considerations
21335 @section IRIX-Specific Considerations
21336 @cindex IRIX thread library
21339 On SGI IRIX, the thread library depends on which compiler is used.
21340 The @emph{o32 ABI} compiler comes with a run-time library based on the
21341 user-level @code{athread}
21342 library. Thus kernel-level capabilities such as nonblocking system
21343 calls or time slicing can only be achieved reliably by specifying different
21344 @code{sprocs} via the pragma @code{Task_Info}
21345 @cindex pragma Task_Info (and IRIX threads)
21347 @code{System.Task_Info} package.
21348 @cindex @code{System.Task_Info} package (and IRIX threads)
21349 See the @cite{GNAT Reference Manual} for further information.
21351 The @emph{n32 ABI} compiler comes with a run-time library based on the
21352 kernel POSIX threads and thus does not have the limitations mentioned above.
21355 @node Linux-Specific Considerations
21356 @section Linux-Specific Considerations
21357 @cindex Linux threads libraries
21360 The default thread library under GNU/Linux has the following disadvantages
21361 compared to other native thread libraries:
21364 @item The size of the task's stack is limited to 2 megabytes.
21365 @item The signal model is not POSIX compliant, which means that to send a
21366 signal to the process, you need to send the signal to all threads,
21367 e.g. by using @code{killpg()}.
21370 @node AIX-Specific Considerations
21371 @section AIX-Specific Considerations
21372 @cindex AIX resolver library
21375 On AIX, the resolver library initializes some internal structure on
21376 the first call to @code{get*by*} functions, which are used to implement
21377 @code{GNAT.Sockets.Get_Host_By_Name} and
21378 @code{GNAT.Sockets.Get_Host_By_Addrss}.
21379 If such initialization occurs within an Ada task, and the stack size for
21380 the task is the default size, a stack overflow may occur.
21382 To avoid this overflow, the user should either ensure that the first call
21383 to @code{GNAT.Sockets.Get_Host_By_Name} or
21384 @code{GNAT.Sockets.Get_Host_By_Addrss}
21385 occurs in the environment task, or use @code{pragma Storage_Size} to
21386 specify a sufficiently large size for the stack of the task that contains
21389 @c *******************************
21390 @node Example of Binder Output File
21391 @appendix Example of Binder Output File
21394 This Appendix displays the source code for @command{gnatbind}'s output
21395 file generated for a simple ``Hello World'' program.
21396 Comments have been added for clarification purposes.
21399 @smallexample @c adanocomment
21403 -- The package is called Ada_Main unless this name is actually used
21404 -- as a unit name in the partition, in which case some other unique
21408 package ada_main is
21410 Elab_Final_Code : Integer;
21411 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
21413 -- The main program saves the parameters (argument count,
21414 -- argument values, environment pointer) in global variables
21415 -- for later access by other units including
21416 -- Ada.Command_Line.
21418 gnat_argc : Integer;
21419 gnat_argv : System.Address;
21420 gnat_envp : System.Address;
21422 -- The actual variables are stored in a library routine. This
21423 -- is useful for some shared library situations, where there
21424 -- are problems if variables are not in the library.
21426 pragma Import (C, gnat_argc);
21427 pragma Import (C, gnat_argv);
21428 pragma Import (C, gnat_envp);
21430 -- The exit status is similarly an external location
21432 gnat_exit_status : Integer;
21433 pragma Import (C, gnat_exit_status);
21435 GNAT_Version : constant String :=
21436 "GNAT Version: 3.15w (20010315)";
21437 pragma Export (C, GNAT_Version, "__gnat_version");
21439 -- This is the generated adafinal routine that performs
21440 -- finalization at the end of execution. In the case where
21441 -- Ada is the main program, this main program makes a call
21442 -- to adafinal at program termination.
21444 procedure adafinal;
21445 pragma Export (C, adafinal, "adafinal");
21447 -- This is the generated adainit routine that performs
21448 -- initialization at the start of execution. In the case
21449 -- where Ada is the main program, this main program makes
21450 -- a call to adainit at program startup.
21453 pragma Export (C, adainit, "adainit");
21455 -- This routine is called at the start of execution. It is
21456 -- a dummy routine that is used by the debugger to breakpoint
21457 -- at the start of execution.
21459 procedure Break_Start;
21460 pragma Import (C, Break_Start, "__gnat_break_start");
21462 -- This is the actual generated main program (it would be
21463 -- suppressed if the no main program switch were used). As
21464 -- required by standard system conventions, this program has
21465 -- the external name main.
21469 argv : System.Address;
21470 envp : System.Address)
21472 pragma Export (C, main, "main");
21474 -- The following set of constants give the version
21475 -- identification values for every unit in the bound
21476 -- partition. This identification is computed from all
21477 -- dependent semantic units, and corresponds to the
21478 -- string that would be returned by use of the
21479 -- Body_Version or Version attributes.
21481 type Version_32 is mod 2 ** 32;
21482 u00001 : constant Version_32 := 16#7880BEB3#;
21483 u00002 : constant Version_32 := 16#0D24CBD0#;
21484 u00003 : constant Version_32 := 16#3283DBEB#;
21485 u00004 : constant Version_32 := 16#2359F9ED#;
21486 u00005 : constant Version_32 := 16#664FB847#;
21487 u00006 : constant Version_32 := 16#68E803DF#;
21488 u00007 : constant Version_32 := 16#5572E604#;
21489 u00008 : constant Version_32 := 16#46B173D8#;
21490 u00009 : constant Version_32 := 16#156A40CF#;
21491 u00010 : constant Version_32 := 16#033DABE0#;
21492 u00011 : constant Version_32 := 16#6AB38FEA#;
21493 u00012 : constant Version_32 := 16#22B6217D#;
21494 u00013 : constant Version_32 := 16#68A22947#;
21495 u00014 : constant Version_32 := 16#18CC4A56#;
21496 u00015 : constant Version_32 := 16#08258E1B#;
21497 u00016 : constant Version_32 := 16#367D5222#;
21498 u00017 : constant Version_32 := 16#20C9ECA4#;
21499 u00018 : constant Version_32 := 16#50D32CB6#;
21500 u00019 : constant Version_32 := 16#39A8BB77#;
21501 u00020 : constant Version_32 := 16#5CF8FA2B#;
21502 u00021 : constant Version_32 := 16#2F1EB794#;
21503 u00022 : constant Version_32 := 16#31AB6444#;
21504 u00023 : constant Version_32 := 16#1574B6E9#;
21505 u00024 : constant Version_32 := 16#5109C189#;
21506 u00025 : constant Version_32 := 16#56D770CD#;
21507 u00026 : constant Version_32 := 16#02F9DE3D#;
21508 u00027 : constant Version_32 := 16#08AB6B2C#;
21509 u00028 : constant Version_32 := 16#3FA37670#;
21510 u00029 : constant Version_32 := 16#476457A0#;
21511 u00030 : constant Version_32 := 16#731E1B6E#;
21512 u00031 : constant Version_32 := 16#23C2E789#;
21513 u00032 : constant Version_32 := 16#0F1BD6A1#;
21514 u00033 : constant Version_32 := 16#7C25DE96#;
21515 u00034 : constant Version_32 := 16#39ADFFA2#;
21516 u00035 : constant Version_32 := 16#571DE3E7#;
21517 u00036 : constant Version_32 := 16#5EB646AB#;
21518 u00037 : constant Version_32 := 16#4249379B#;
21519 u00038 : constant Version_32 := 16#0357E00A#;
21520 u00039 : constant Version_32 := 16#3784FB72#;
21521 u00040 : constant Version_32 := 16#2E723019#;
21522 u00041 : constant Version_32 := 16#623358EA#;
21523 u00042 : constant Version_32 := 16#107F9465#;
21524 u00043 : constant Version_32 := 16#6843F68A#;
21525 u00044 : constant Version_32 := 16#63305874#;
21526 u00045 : constant Version_32 := 16#31E56CE1#;
21527 u00046 : constant Version_32 := 16#02917970#;
21528 u00047 : constant Version_32 := 16#6CCBA70E#;
21529 u00048 : constant Version_32 := 16#41CD4204#;
21530 u00049 : constant Version_32 := 16#572E3F58#;
21531 u00050 : constant Version_32 := 16#20729FF5#;
21532 u00051 : constant Version_32 := 16#1D4F93E8#;
21533 u00052 : constant Version_32 := 16#30B2EC3D#;
21534 u00053 : constant Version_32 := 16#34054F96#;
21535 u00054 : constant Version_32 := 16#5A199860#;
21536 u00055 : constant Version_32 := 16#0E7F912B#;
21537 u00056 : constant Version_32 := 16#5760634A#;
21538 u00057 : constant Version_32 := 16#5D851835#;
21540 -- The following Export pragmas export the version numbers
21541 -- with symbolic names ending in B (for body) or S
21542 -- (for spec) so that they can be located in a link. The
21543 -- information provided here is sufficient to track down
21544 -- the exact versions of units used in a given build.
21546 pragma Export (C, u00001, "helloB");
21547 pragma Export (C, u00002, "system__standard_libraryB");
21548 pragma Export (C, u00003, "system__standard_libraryS");
21549 pragma Export (C, u00004, "adaS");
21550 pragma Export (C, u00005, "ada__text_ioB");
21551 pragma Export (C, u00006, "ada__text_ioS");
21552 pragma Export (C, u00007, "ada__exceptionsB");
21553 pragma Export (C, u00008, "ada__exceptionsS");
21554 pragma Export (C, u00009, "gnatS");
21555 pragma Export (C, u00010, "gnat__heap_sort_aB");
21556 pragma Export (C, u00011, "gnat__heap_sort_aS");
21557 pragma Export (C, u00012, "systemS");
21558 pragma Export (C, u00013, "system__exception_tableB");
21559 pragma Export (C, u00014, "system__exception_tableS");
21560 pragma Export (C, u00015, "gnat__htableB");
21561 pragma Export (C, u00016, "gnat__htableS");
21562 pragma Export (C, u00017, "system__exceptionsS");
21563 pragma Export (C, u00018, "system__machine_state_operationsB");
21564 pragma Export (C, u00019, "system__machine_state_operationsS");
21565 pragma Export (C, u00020, "system__machine_codeS");
21566 pragma Export (C, u00021, "system__storage_elementsB");
21567 pragma Export (C, u00022, "system__storage_elementsS");
21568 pragma Export (C, u00023, "system__secondary_stackB");
21569 pragma Export (C, u00024, "system__secondary_stackS");
21570 pragma Export (C, u00025, "system__parametersB");
21571 pragma Export (C, u00026, "system__parametersS");
21572 pragma Export (C, u00027, "system__soft_linksB");
21573 pragma Export (C, u00028, "system__soft_linksS");
21574 pragma Export (C, u00029, "system__stack_checkingB");
21575 pragma Export (C, u00030, "system__stack_checkingS");
21576 pragma Export (C, u00031, "system__tracebackB");
21577 pragma Export (C, u00032, "system__tracebackS");
21578 pragma Export (C, u00033, "ada__streamsS");
21579 pragma Export (C, u00034, "ada__tagsB");
21580 pragma Export (C, u00035, "ada__tagsS");
21581 pragma Export (C, u00036, "system__string_opsB");
21582 pragma Export (C, u00037, "system__string_opsS");
21583 pragma Export (C, u00038, "interfacesS");
21584 pragma Export (C, u00039, "interfaces__c_streamsB");
21585 pragma Export (C, u00040, "interfaces__c_streamsS");
21586 pragma Export (C, u00041, "system__file_ioB");
21587 pragma Export (C, u00042, "system__file_ioS");
21588 pragma Export (C, u00043, "ada__finalizationB");
21589 pragma Export (C, u00044, "ada__finalizationS");
21590 pragma Export (C, u00045, "system__finalization_rootB");
21591 pragma Export (C, u00046, "system__finalization_rootS");
21592 pragma Export (C, u00047, "system__finalization_implementationB");
21593 pragma Export (C, u00048, "system__finalization_implementationS");
21594 pragma Export (C, u00049, "system__string_ops_concat_3B");
21595 pragma Export (C, u00050, "system__string_ops_concat_3S");
21596 pragma Export (C, u00051, "system__stream_attributesB");
21597 pragma Export (C, u00052, "system__stream_attributesS");
21598 pragma Export (C, u00053, "ada__io_exceptionsS");
21599 pragma Export (C, u00054, "system__unsigned_typesS");
21600 pragma Export (C, u00055, "system__file_control_blockS");
21601 pragma Export (C, u00056, "ada__finalization__list_controllerB");
21602 pragma Export (C, u00057, "ada__finalization__list_controllerS");
21604 -- BEGIN ELABORATION ORDER
21607 -- gnat.heap_sort_a (spec)
21608 -- gnat.heap_sort_a (body)
21609 -- gnat.htable (spec)
21610 -- gnat.htable (body)
21611 -- interfaces (spec)
21613 -- system.machine_code (spec)
21614 -- system.parameters (spec)
21615 -- system.parameters (body)
21616 -- interfaces.c_streams (spec)
21617 -- interfaces.c_streams (body)
21618 -- system.standard_library (spec)
21619 -- ada.exceptions (spec)
21620 -- system.exception_table (spec)
21621 -- system.exception_table (body)
21622 -- ada.io_exceptions (spec)
21623 -- system.exceptions (spec)
21624 -- system.storage_elements (spec)
21625 -- system.storage_elements (body)
21626 -- system.machine_state_operations (spec)
21627 -- system.machine_state_operations (body)
21628 -- system.secondary_stack (spec)
21629 -- system.stack_checking (spec)
21630 -- system.soft_links (spec)
21631 -- system.soft_links (body)
21632 -- system.stack_checking (body)
21633 -- system.secondary_stack (body)
21634 -- system.standard_library (body)
21635 -- system.string_ops (spec)
21636 -- system.string_ops (body)
21639 -- ada.streams (spec)
21640 -- system.finalization_root (spec)
21641 -- system.finalization_root (body)
21642 -- system.string_ops_concat_3 (spec)
21643 -- system.string_ops_concat_3 (body)
21644 -- system.traceback (spec)
21645 -- system.traceback (body)
21646 -- ada.exceptions (body)
21647 -- system.unsigned_types (spec)
21648 -- system.stream_attributes (spec)
21649 -- system.stream_attributes (body)
21650 -- system.finalization_implementation (spec)
21651 -- system.finalization_implementation (body)
21652 -- ada.finalization (spec)
21653 -- ada.finalization (body)
21654 -- ada.finalization.list_controller (spec)
21655 -- ada.finalization.list_controller (body)
21656 -- system.file_control_block (spec)
21657 -- system.file_io (spec)
21658 -- system.file_io (body)
21659 -- ada.text_io (spec)
21660 -- ada.text_io (body)
21662 -- END ELABORATION ORDER
21666 -- The following source file name pragmas allow the generated file
21667 -- names to be unique for different main programs. They are needed
21668 -- since the package name will always be Ada_Main.
21670 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
21671 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
21673 -- Generated package body for Ada_Main starts here
21675 package body ada_main is
21677 -- The actual finalization is performed by calling the
21678 -- library routine in System.Standard_Library.Adafinal
21680 procedure Do_Finalize;
21681 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
21688 procedure adainit is
21690 -- These booleans are set to True once the associated unit has
21691 -- been elaborated. It is also used to avoid elaborating the
21692 -- same unit twice.
21695 pragma Import (Ada, E040, "interfaces__c_streams_E");
21698 pragma Import (Ada, E008, "ada__exceptions_E");
21701 pragma Import (Ada, E014, "system__exception_table_E");
21704 pragma Import (Ada, E053, "ada__io_exceptions_E");
21707 pragma Import (Ada, E017, "system__exceptions_E");
21710 pragma Import (Ada, E024, "system__secondary_stack_E");
21713 pragma Import (Ada, E030, "system__stack_checking_E");
21716 pragma Import (Ada, E028, "system__soft_links_E");
21719 pragma Import (Ada, E035, "ada__tags_E");
21722 pragma Import (Ada, E033, "ada__streams_E");
21725 pragma Import (Ada, E046, "system__finalization_root_E");
21728 pragma Import (Ada, E048, "system__finalization_implementation_E");
21731 pragma Import (Ada, E044, "ada__finalization_E");
21734 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
21737 pragma Import (Ada, E055, "system__file_control_block_E");
21740 pragma Import (Ada, E042, "system__file_io_E");
21743 pragma Import (Ada, E006, "ada__text_io_E");
21745 -- Set_Globals is a library routine that stores away the
21746 -- value of the indicated set of global values in global
21747 -- variables within the library.
21749 procedure Set_Globals
21750 (Main_Priority : Integer;
21751 Time_Slice_Value : Integer;
21752 WC_Encoding : Character;
21753 Locking_Policy : Character;
21754 Queuing_Policy : Character;
21755 Task_Dispatching_Policy : Character;
21756 Adafinal : System.Address;
21757 Unreserve_All_Interrupts : Integer;
21758 Exception_Tracebacks : Integer);
21759 @findex __gnat_set_globals
21760 pragma Import (C, Set_Globals, "__gnat_set_globals");
21762 -- SDP_Table_Build is a library routine used to build the
21763 -- exception tables. See unit Ada.Exceptions in files
21764 -- a-except.ads/adb for full details of how zero cost
21765 -- exception handling works. This procedure, the call to
21766 -- it, and the two following tables are all omitted if the
21767 -- build is in longjmp/setjump exception mode.
21769 @findex SDP_Table_Build
21770 @findex Zero Cost Exceptions
21771 procedure SDP_Table_Build
21772 (SDP_Addresses : System.Address;
21773 SDP_Count : Natural;
21774 Elab_Addresses : System.Address;
21775 Elab_Addr_Count : Natural);
21776 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
21778 -- Table of Unit_Exception_Table addresses. Used for zero
21779 -- cost exception handling to build the top level table.
21781 ST : aliased constant array (1 .. 23) of System.Address := (
21783 Ada.Text_Io'UET_Address,
21784 Ada.Exceptions'UET_Address,
21785 Gnat.Heap_Sort_A'UET_Address,
21786 System.Exception_Table'UET_Address,
21787 System.Machine_State_Operations'UET_Address,
21788 System.Secondary_Stack'UET_Address,
21789 System.Parameters'UET_Address,
21790 System.Soft_Links'UET_Address,
21791 System.Stack_Checking'UET_Address,
21792 System.Traceback'UET_Address,
21793 Ada.Streams'UET_Address,
21794 Ada.Tags'UET_Address,
21795 System.String_Ops'UET_Address,
21796 Interfaces.C_Streams'UET_Address,
21797 System.File_Io'UET_Address,
21798 Ada.Finalization'UET_Address,
21799 System.Finalization_Root'UET_Address,
21800 System.Finalization_Implementation'UET_Address,
21801 System.String_Ops_Concat_3'UET_Address,
21802 System.Stream_Attributes'UET_Address,
21803 System.File_Control_Block'UET_Address,
21804 Ada.Finalization.List_Controller'UET_Address);
21806 -- Table of addresses of elaboration routines. Used for
21807 -- zero cost exception handling to make sure these
21808 -- addresses are included in the top level procedure
21811 EA : aliased constant array (1 .. 23) of System.Address := (
21812 adainit'Code_Address,
21813 Do_Finalize'Code_Address,
21814 Ada.Exceptions'Elab_Spec'Address,
21815 System.Exceptions'Elab_Spec'Address,
21816 Interfaces.C_Streams'Elab_Spec'Address,
21817 System.Exception_Table'Elab_Body'Address,
21818 Ada.Io_Exceptions'Elab_Spec'Address,
21819 System.Stack_Checking'Elab_Spec'Address,
21820 System.Soft_Links'Elab_Body'Address,
21821 System.Secondary_Stack'Elab_Body'Address,
21822 Ada.Tags'Elab_Spec'Address,
21823 Ada.Tags'Elab_Body'Address,
21824 Ada.Streams'Elab_Spec'Address,
21825 System.Finalization_Root'Elab_Spec'Address,
21826 Ada.Exceptions'Elab_Body'Address,
21827 System.Finalization_Implementation'Elab_Spec'Address,
21828 System.Finalization_Implementation'Elab_Body'Address,
21829 Ada.Finalization'Elab_Spec'Address,
21830 Ada.Finalization.List_Controller'Elab_Spec'Address,
21831 System.File_Control_Block'Elab_Spec'Address,
21832 System.File_Io'Elab_Body'Address,
21833 Ada.Text_Io'Elab_Spec'Address,
21834 Ada.Text_Io'Elab_Body'Address);
21836 -- Start of processing for adainit
21840 -- Call SDP_Table_Build to build the top level procedure
21841 -- table for zero cost exception handling (omitted in
21842 -- longjmp/setjump mode).
21844 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
21846 -- Call Set_Globals to record various information for
21847 -- this partition. The values are derived by the binder
21848 -- from information stored in the ali files by the compiler.
21850 @findex __gnat_set_globals
21852 (Main_Priority => -1,
21853 -- Priority of main program, -1 if no pragma Priority used
21855 Time_Slice_Value => -1,
21856 -- Time slice from Time_Slice pragma, -1 if none used
21858 WC_Encoding => 'b',
21859 -- Wide_Character encoding used, default is brackets
21861 Locking_Policy => ' ',
21862 -- Locking_Policy used, default of space means not
21863 -- specified, otherwise it is the first character of
21864 -- the policy name.
21866 Queuing_Policy => ' ',
21867 -- Queuing_Policy used, default of space means not
21868 -- specified, otherwise it is the first character of
21869 -- the policy name.
21871 Task_Dispatching_Policy => ' ',
21872 -- Task_Dispatching_Policy used, default of space means
21873 -- not specified, otherwise first character of the
21876 Adafinal => System.Null_Address,
21877 -- Address of Adafinal routine, not used anymore
21879 Unreserve_All_Interrupts => 0,
21880 -- Set true if pragma Unreserve_All_Interrupts was used
21882 Exception_Tracebacks => 0);
21883 -- Indicates if exception tracebacks are enabled
21885 Elab_Final_Code := 1;
21887 -- Now we have the elaboration calls for all units in the partition.
21888 -- The Elab_Spec and Elab_Body attributes generate references to the
21889 -- implicit elaboration procedures generated by the compiler for
21890 -- each unit that requires elaboration.
21893 Interfaces.C_Streams'Elab_Spec;
21897 Ada.Exceptions'Elab_Spec;
21900 System.Exception_Table'Elab_Body;
21904 Ada.Io_Exceptions'Elab_Spec;
21908 System.Exceptions'Elab_Spec;
21912 System.Stack_Checking'Elab_Spec;
21915 System.Soft_Links'Elab_Body;
21920 System.Secondary_Stack'Elab_Body;
21924 Ada.Tags'Elab_Spec;
21927 Ada.Tags'Elab_Body;
21931 Ada.Streams'Elab_Spec;
21935 System.Finalization_Root'Elab_Spec;
21939 Ada.Exceptions'Elab_Body;
21943 System.Finalization_Implementation'Elab_Spec;
21946 System.Finalization_Implementation'Elab_Body;
21950 Ada.Finalization'Elab_Spec;
21954 Ada.Finalization.List_Controller'Elab_Spec;
21958 System.File_Control_Block'Elab_Spec;
21962 System.File_Io'Elab_Body;
21966 Ada.Text_Io'Elab_Spec;
21969 Ada.Text_Io'Elab_Body;
21973 Elab_Final_Code := 0;
21981 procedure adafinal is
21990 -- main is actually a function, as in the ANSI C standard,
21991 -- defined to return the exit status. The three parameters
21992 -- are the argument count, argument values and environment
21995 @findex Main Program
21998 argv : System.Address;
21999 envp : System.Address)
22002 -- The initialize routine performs low level system
22003 -- initialization using a standard library routine which
22004 -- sets up signal handling and performs any other
22005 -- required setup. The routine can be found in file
22008 @findex __gnat_initialize
22009 procedure initialize;
22010 pragma Import (C, initialize, "__gnat_initialize");
22012 -- The finalize routine performs low level system
22013 -- finalization using a standard library routine. The
22014 -- routine is found in file a-final.c and in the standard
22015 -- distribution is a dummy routine that does nothing, so
22016 -- really this is a hook for special user finalization.
22018 @findex __gnat_finalize
22019 procedure finalize;
22020 pragma Import (C, finalize, "__gnat_finalize");
22022 -- We get to the main program of the partition by using
22023 -- pragma Import because if we try to with the unit and
22024 -- call it Ada style, then not only do we waste time
22025 -- recompiling it, but also, we don't really know the right
22026 -- switches (e.g. identifier character set) to be used
22029 procedure Ada_Main_Program;
22030 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
22032 -- Start of processing for main
22035 -- Save global variables
22041 -- Call low level system initialization
22045 -- Call our generated Ada initialization routine
22049 -- This is the point at which we want the debugger to get
22054 -- Now we call the main program of the partition
22058 -- Perform Ada finalization
22062 -- Perform low level system finalization
22066 -- Return the proper exit status
22067 return (gnat_exit_status);
22070 -- This section is entirely comments, so it has no effect on the
22071 -- compilation of the Ada_Main package. It provides the list of
22072 -- object files and linker options, as well as some standard
22073 -- libraries needed for the link. The gnatlink utility parses
22074 -- this b~hello.adb file to read these comment lines to generate
22075 -- the appropriate command line arguments for the call to the
22076 -- system linker. The BEGIN/END lines are used for sentinels for
22077 -- this parsing operation.
22079 -- The exact file names will of course depend on the environment,
22080 -- host/target and location of files on the host system.
22082 @findex Object file list
22083 -- BEGIN Object file/option list
22086 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
22087 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
22088 -- END Object file/option list
22094 The Ada code in the above example is exactly what is generated by the
22095 binder. We have added comments to more clearly indicate the function
22096 of each part of the generated @code{Ada_Main} package.
22098 The code is standard Ada in all respects, and can be processed by any
22099 tools that handle Ada. In particular, it is possible to use the debugger
22100 in Ada mode to debug the generated @code{Ada_Main} package. For example,
22101 suppose that for reasons that you do not understand, your program is crashing
22102 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
22103 you can place a breakpoint on the call:
22105 @smallexample @c ada
22106 Ada.Text_Io'Elab_Body;
22110 and trace the elaboration routine for this package to find out where
22111 the problem might be (more usually of course you would be debugging
22112 elaboration code in your own application).
22115 @node Elaboration Order Handling in GNAT
22116 @appendix Elaboration Order Handling in GNAT
22117 @cindex Order of elaboration
22118 @cindex Elaboration control
22121 * Elaboration Code in Ada 95::
22122 * Checking the Elaboration Order in Ada 95::
22123 * Controlling the Elaboration Order in Ada 95::
22124 * Controlling Elaboration in GNAT - Internal Calls::
22125 * Controlling Elaboration in GNAT - External Calls::
22126 * Default Behavior in GNAT - Ensuring Safety::
22127 * Treatment of Pragma Elaborate::
22128 * Elaboration Issues for Library Tasks::
22129 * Mixing Elaboration Models::
22130 * What to Do If the Default Elaboration Behavior Fails::
22131 * Elaboration for Access-to-Subprogram Values::
22132 * Summary of Procedures for Elaboration Control::
22133 * Other Elaboration Order Considerations::
22137 This chapter describes the handling of elaboration code in Ada 95 and
22138 in GNAT, and discusses how the order of elaboration of program units can
22139 be controlled in GNAT, either automatically or with explicit programming
22142 @node Elaboration Code in Ada 95
22143 @section Elaboration Code in Ada 95
22146 Ada 95 provides rather general mechanisms for executing code at elaboration
22147 time, that is to say before the main program starts executing. Such code arises
22151 @item Initializers for variables.
22152 Variables declared at the library level, in package specs or bodies, can
22153 require initialization that is performed at elaboration time, as in:
22154 @smallexample @c ada
22156 Sqrt_Half : Float := Sqrt (0.5);
22160 @item Package initialization code
22161 Code in a @code{BEGIN-END} section at the outer level of a package body is
22162 executed as part of the package body elaboration code.
22164 @item Library level task allocators
22165 Tasks that are declared using task allocators at the library level
22166 start executing immediately and hence can execute at elaboration time.
22170 Subprogram calls are possible in any of these contexts, which means that
22171 any arbitrary part of the program may be executed as part of the elaboration
22172 code. It is even possible to write a program which does all its work at
22173 elaboration time, with a null main program, although stylistically this
22174 would usually be considered an inappropriate way to structure
22177 An important concern arises in the context of elaboration code:
22178 we have to be sure that it is executed in an appropriate order. What we
22179 have is a series of elaboration code sections, potentially one section
22180 for each unit in the program. It is important that these execute
22181 in the correct order. Correctness here means that, taking the above
22182 example of the declaration of @code{Sqrt_Half},
22183 if some other piece of
22184 elaboration code references @code{Sqrt_Half},
22185 then it must run after the
22186 section of elaboration code that contains the declaration of
22189 There would never be any order of elaboration problem if we made a rule
22190 that whenever you @code{with} a unit, you must elaborate both the spec and body
22191 of that unit before elaborating the unit doing the @code{with}'ing:
22193 @smallexample @c ada
22197 package Unit_2 is ...
22203 would require that both the body and spec of @code{Unit_1} be elaborated
22204 before the spec of @code{Unit_2}. However, a rule like that would be far too
22205 restrictive. In particular, it would make it impossible to have routines
22206 in separate packages that were mutually recursive.
22208 You might think that a clever enough compiler could look at the actual
22209 elaboration code and determine an appropriate correct order of elaboration,
22210 but in the general case, this is not possible. Consider the following
22213 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
22215 the variable @code{Sqrt_1}, which is declared in the elaboration code
22216 of the body of @code{Unit_1}:
22218 @smallexample @c ada
22220 Sqrt_1 : Float := Sqrt (0.1);
22225 The elaboration code of the body of @code{Unit_1} also contains:
22227 @smallexample @c ada
22230 if expression_1 = 1 then
22231 Q := Unit_2.Func_2;
22238 @code{Unit_2} is exactly parallel,
22239 it has a procedure @code{Func_2} that references
22240 the variable @code{Sqrt_2}, which is declared in the elaboration code of
22241 the body @code{Unit_2}:
22243 @smallexample @c ada
22245 Sqrt_2 : Float := Sqrt (0.1);
22250 The elaboration code of the body of @code{Unit_2} also contains:
22252 @smallexample @c ada
22255 if expression_2 = 2 then
22256 Q := Unit_1.Func_1;
22263 Now the question is, which of the following orders of elaboration is
22288 If you carefully analyze the flow here, you will see that you cannot tell
22289 at compile time the answer to this question.
22290 If @code{expression_1} is not equal to 1,
22291 and @code{expression_2} is not equal to 2,
22292 then either order is acceptable, because neither of the function calls is
22293 executed. If both tests evaluate to true, then neither order is acceptable
22294 and in fact there is no correct order.
22296 If one of the two expressions is true, and the other is false, then one
22297 of the above orders is correct, and the other is incorrect. For example,
22298 if @code{expression_1} = 1 and @code{expression_2} /= 2,
22299 then the call to @code{Func_2}
22300 will occur, but not the call to @code{Func_1.}
22301 This means that it is essential
22302 to elaborate the body of @code{Unit_1} before
22303 the body of @code{Unit_2}, so the first
22304 order of elaboration is correct and the second is wrong.
22306 By making @code{expression_1} and @code{expression_2}
22307 depend on input data, or perhaps
22308 the time of day, we can make it impossible for the compiler or binder
22309 to figure out which of these expressions will be true, and hence it
22310 is impossible to guarantee a safe order of elaboration at run time.
22312 @node Checking the Elaboration Order in Ada 95
22313 @section Checking the Elaboration Order in Ada 95
22316 In some languages that involve the same kind of elaboration problems,
22317 e.g. Java and C++, the programmer is expected to worry about these
22318 ordering problems himself, and it is common to
22319 write a program in which an incorrect elaboration order gives
22320 surprising results, because it references variables before they
22322 Ada 95 is designed to be a safe language, and a programmer-beware approach is
22323 clearly not sufficient. Consequently, the language provides three lines
22327 @item Standard rules
22328 Some standard rules restrict the possible choice of elaboration
22329 order. In particular, if you @code{with} a unit, then its spec is always
22330 elaborated before the unit doing the @code{with}. Similarly, a parent
22331 spec is always elaborated before the child spec, and finally
22332 a spec is always elaborated before its corresponding body.
22334 @item Dynamic elaboration checks
22335 @cindex Elaboration checks
22336 @cindex Checks, elaboration
22337 Dynamic checks are made at run time, so that if some entity is accessed
22338 before it is elaborated (typically by means of a subprogram call)
22339 then the exception (@code{Program_Error}) is raised.
22341 @item Elaboration control
22342 Facilities are provided for the programmer to specify the desired order
22346 Let's look at these facilities in more detail. First, the rules for
22347 dynamic checking. One possible rule would be simply to say that the
22348 exception is raised if you access a variable which has not yet been
22349 elaborated. The trouble with this approach is that it could require
22350 expensive checks on every variable reference. Instead Ada 95 has two
22351 rules which are a little more restrictive, but easier to check, and
22355 @item Restrictions on calls
22356 A subprogram can only be called at elaboration time if its body
22357 has been elaborated. The rules for elaboration given above guarantee
22358 that the spec of the subprogram has been elaborated before the
22359 call, but not the body. If this rule is violated, then the
22360 exception @code{Program_Error} is raised.
22362 @item Restrictions on instantiations
22363 A generic unit can only be instantiated if the body of the generic
22364 unit has been elaborated. Again, the rules for elaboration given above
22365 guarantee that the spec of the generic unit has been elaborated
22366 before the instantiation, but not the body. If this rule is
22367 violated, then the exception @code{Program_Error} is raised.
22371 The idea is that if the body has been elaborated, then any variables
22372 it references must have been elaborated; by checking for the body being
22373 elaborated we guarantee that none of its references causes any
22374 trouble. As we noted above, this is a little too restrictive, because a
22375 subprogram that has no non-local references in its body may in fact be safe
22376 to call. However, it really would be unsafe to rely on this, because
22377 it would mean that the caller was aware of details of the implementation
22378 in the body. This goes against the basic tenets of Ada.
22380 A plausible implementation can be described as follows.
22381 A Boolean variable is associated with each subprogram
22382 and each generic unit. This variable is initialized to False, and is set to
22383 True at the point body is elaborated. Every call or instantiation checks the
22384 variable, and raises @code{Program_Error} if the variable is False.
22386 Note that one might think that it would be good enough to have one Boolean
22387 variable for each package, but that would not deal with cases of trying
22388 to call a body in the same package as the call
22389 that has not been elaborated yet.
22390 Of course a compiler may be able to do enough analysis to optimize away
22391 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
22392 does such optimizations, but still the easiest conceptual model is to
22393 think of there being one variable per subprogram.
22395 @node Controlling the Elaboration Order in Ada 95
22396 @section Controlling the Elaboration Order in Ada 95
22399 In the previous section we discussed the rules in Ada 95 which ensure
22400 that @code{Program_Error} is raised if an incorrect elaboration order is
22401 chosen. This prevents erroneous executions, but we need mechanisms to
22402 specify a correct execution and avoid the exception altogether.
22403 To achieve this, Ada 95 provides a number of features for controlling
22404 the order of elaboration. We discuss these features in this section.
22406 First, there are several ways of indicating to the compiler that a given
22407 unit has no elaboration problems:
22410 @item packages that do not require a body
22411 In Ada 95, a library package that does not require a body does not permit
22412 a body. This means that if we have a such a package, as in:
22414 @smallexample @c ada
22417 package Definitions is
22419 type m is new integer;
22421 type a is array (1 .. 10) of m;
22422 type b is array (1 .. 20) of m;
22430 A package that @code{with}'s @code{Definitions} may safely instantiate
22431 @code{Definitions.Subp} because the compiler can determine that there
22432 definitely is no package body to worry about in this case
22435 @cindex pragma Pure
22437 Places sufficient restrictions on a unit to guarantee that
22438 no call to any subprogram in the unit can result in an
22439 elaboration problem. This means that the compiler does not need
22440 to worry about the point of elaboration of such units, and in
22441 particular, does not need to check any calls to any subprograms
22444 @item pragma Preelaborate
22445 @findex Preelaborate
22446 @cindex pragma Preelaborate
22447 This pragma places slightly less stringent restrictions on a unit than
22449 but these restrictions are still sufficient to ensure that there
22450 are no elaboration problems with any calls to the unit.
22452 @item pragma Elaborate_Body
22453 @findex Elaborate_Body
22454 @cindex pragma Elaborate_Body
22455 This pragma requires that the body of a unit be elaborated immediately
22456 after its spec. Suppose a unit @code{A} has such a pragma,
22457 and unit @code{B} does
22458 a @code{with} of unit @code{A}. Recall that the standard rules require
22459 the spec of unit @code{A}
22460 to be elaborated before the @code{with}'ing unit; given the pragma in
22461 @code{A}, we also know that the body of @code{A}
22462 will be elaborated before @code{B}, so
22463 that calls to @code{A} are safe and do not need a check.
22468 unlike pragma @code{Pure} and pragma @code{Preelaborate},
22470 @code{Elaborate_Body} does not guarantee that the program is
22471 free of elaboration problems, because it may not be possible
22472 to satisfy the requested elaboration order.
22473 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
22475 marks @code{Unit_1} as @code{Elaborate_Body},
22476 and not @code{Unit_2,} then the order of
22477 elaboration will be:
22489 Now that means that the call to @code{Func_1} in @code{Unit_2}
22490 need not be checked,
22491 it must be safe. But the call to @code{Func_2} in
22492 @code{Unit_1} may still fail if
22493 @code{Expression_1} is equal to 1,
22494 and the programmer must still take
22495 responsibility for this not being the case.
22497 If all units carry a pragma @code{Elaborate_Body}, then all problems are
22498 eliminated, except for calls entirely within a body, which are
22499 in any case fully under programmer control. However, using the pragma
22500 everywhere is not always possible.
22501 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
22502 we marked both of them as having pragma @code{Elaborate_Body}, then
22503 clearly there would be no possible elaboration order.
22505 The above pragmas allow a server to guarantee safe use by clients, and
22506 clearly this is the preferable approach. Consequently a good rule in
22507 Ada 95 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
22508 and if this is not possible,
22509 mark them as @code{Elaborate_Body} if possible.
22510 As we have seen, there are situations where neither of these
22511 three pragmas can be used.
22512 So we also provide methods for clients to control the
22513 order of elaboration of the servers on which they depend:
22516 @item pragma Elaborate (unit)
22518 @cindex pragma Elaborate
22519 This pragma is placed in the context clause, after a @code{with} clause,
22520 and it requires that the body of the named unit be elaborated before
22521 the unit in which the pragma occurs. The idea is to use this pragma
22522 if the current unit calls at elaboration time, directly or indirectly,
22523 some subprogram in the named unit.
22525 @item pragma Elaborate_All (unit)
22526 @findex Elaborate_All
22527 @cindex pragma Elaborate_All
22528 This is a stronger version of the Elaborate pragma. Consider the
22532 Unit A @code{with}'s unit B and calls B.Func in elab code
22533 Unit B @code{with}'s unit C, and B.Func calls C.Func
22537 Now if we put a pragma @code{Elaborate (B)}
22538 in unit @code{A}, this ensures that the
22539 body of @code{B} is elaborated before the call, but not the
22540 body of @code{C}, so
22541 the call to @code{C.Func} could still cause @code{Program_Error} to
22544 The effect of a pragma @code{Elaborate_All} is stronger, it requires
22545 not only that the body of the named unit be elaborated before the
22546 unit doing the @code{with}, but also the bodies of all units that the
22547 named unit uses, following @code{with} links transitively. For example,
22548 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
22550 not only that the body of @code{B} be elaborated before @code{A},
22552 body of @code{C}, because @code{B} @code{with}'s @code{C}.
22556 We are now in a position to give a usage rule in Ada 95 for avoiding
22557 elaboration problems, at least if dynamic dispatching and access to
22558 subprogram values are not used. We will handle these cases separately
22561 The rule is simple. If a unit has elaboration code that can directly or
22562 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
22563 a generic unit in a @code{with}'ed unit,
22564 then if the @code{with}'ed unit does not have
22565 pragma @code{Pure} or @code{Preelaborate}, then the client should have
22566 a pragma @code{Elaborate_All}
22567 for the @code{with}'ed unit. By following this rule a client is
22568 assured that calls can be made without risk of an exception.
22569 If this rule is not followed, then a program may be in one of four
22573 @item No order exists
22574 No order of elaboration exists which follows the rules, taking into
22575 account any @code{Elaborate}, @code{Elaborate_All},
22576 or @code{Elaborate_Body} pragmas. In
22577 this case, an Ada 95 compiler must diagnose the situation at bind
22578 time, and refuse to build an executable program.
22580 @item One or more orders exist, all incorrect
22581 One or more acceptable elaboration orders exists, and all of them
22582 generate an elaboration order problem. In this case, the binder
22583 can build an executable program, but @code{Program_Error} will be raised
22584 when the program is run.
22586 @item Several orders exist, some right, some incorrect
22587 One or more acceptable elaboration orders exists, and some of them
22588 work, and some do not. The programmer has not controlled
22589 the order of elaboration, so the binder may or may not pick one of
22590 the correct orders, and the program may or may not raise an
22591 exception when it is run. This is the worst case, because it means
22592 that the program may fail when moved to another compiler, or even
22593 another version of the same compiler.
22595 @item One or more orders exists, all correct
22596 One ore more acceptable elaboration orders exist, and all of them
22597 work. In this case the program runs successfully. This state of
22598 affairs can be guaranteed by following the rule we gave above, but
22599 may be true even if the rule is not followed.
22603 Note that one additional advantage of following our Elaborate_All rule
22604 is that the program continues to stay in the ideal (all orders OK) state
22605 even if maintenance
22606 changes some bodies of some subprograms. Conversely, if a program that does
22607 not follow this rule happens to be safe at some point, this state of affairs
22608 may deteriorate silently as a result of maintenance changes.
22610 You may have noticed that the above discussion did not mention
22611 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
22612 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
22613 code in the body makes calls to some other unit, so it is still necessary
22614 to use @code{Elaborate_All} on such units.
22616 @node Controlling Elaboration in GNAT - Internal Calls
22617 @section Controlling Elaboration in GNAT - Internal Calls
22620 In the case of internal calls, i.e. calls within a single package, the
22621 programmer has full control over the order of elaboration, and it is up
22622 to the programmer to elaborate declarations in an appropriate order. For
22625 @smallexample @c ada
22628 function One return Float;
22632 function One return Float is
22641 will obviously raise @code{Program_Error} at run time, because function
22642 One will be called before its body is elaborated. In this case GNAT will
22643 generate a warning that the call will raise @code{Program_Error}:
22649 2. function One return Float;
22651 4. Q : Float := One;
22653 >>> warning: cannot call "One" before body is elaborated
22654 >>> warning: Program_Error will be raised at run time
22657 6. function One return Float is
22670 Note that in this particular case, it is likely that the call is safe, because
22671 the function @code{One} does not access any global variables.
22672 Nevertheless in Ada 95, we do not want the validity of the check to depend on
22673 the contents of the body (think about the separate compilation case), so this
22674 is still wrong, as we discussed in the previous sections.
22676 The error is easily corrected by rearranging the declarations so that the
22677 body of One appears before the declaration containing the call
22678 (note that in Ada 95,
22679 declarations can appear in any order, so there is no restriction that
22680 would prevent this reordering, and if we write:
22682 @smallexample @c ada
22685 function One return Float;
22687 function One return Float is
22698 then all is well, no warning is generated, and no
22699 @code{Program_Error} exception
22701 Things are more complicated when a chain of subprograms is executed:
22703 @smallexample @c ada
22706 function A return Integer;
22707 function B return Integer;
22708 function C return Integer;
22710 function B return Integer is begin return A; end;
22711 function C return Integer is begin return B; end;
22715 function A return Integer is begin return 1; end;
22721 Now the call to @code{C}
22722 at elaboration time in the declaration of @code{X} is correct, because
22723 the body of @code{C} is already elaborated,
22724 and the call to @code{B} within the body of
22725 @code{C} is correct, but the call
22726 to @code{A} within the body of @code{B} is incorrect, because the body
22727 of @code{A} has not been elaborated, so @code{Program_Error}
22728 will be raised on the call to @code{A}.
22729 In this case GNAT will generate a
22730 warning that @code{Program_Error} may be
22731 raised at the point of the call. Let's look at the warning:
22737 2. function A return Integer;
22738 3. function B return Integer;
22739 4. function C return Integer;
22741 6. function B return Integer is begin return A; end;
22743 >>> warning: call to "A" before body is elaborated may
22744 raise Program_Error
22745 >>> warning: "B" called at line 7
22746 >>> warning: "C" called at line 9
22748 7. function C return Integer is begin return B; end;
22750 9. X : Integer := C;
22752 11. function A return Integer is begin return 1; end;
22762 Note that the message here says ``may raise'', instead of the direct case,
22763 where the message says ``will be raised''. That's because whether
22765 actually called depends in general on run-time flow of control.
22766 For example, if the body of @code{B} said
22768 @smallexample @c ada
22771 function B return Integer is
22773 if some-condition-depending-on-input-data then
22784 then we could not know until run time whether the incorrect call to A would
22785 actually occur, so @code{Program_Error} might
22786 or might not be raised. It is possible for a compiler to
22787 do a better job of analyzing bodies, to
22788 determine whether or not @code{Program_Error}
22789 might be raised, but it certainly
22790 couldn't do a perfect job (that would require solving the halting problem
22791 and is provably impossible), and because this is a warning anyway, it does
22792 not seem worth the effort to do the analysis. Cases in which it
22793 would be relevant are rare.
22795 In practice, warnings of either of the forms given
22796 above will usually correspond to
22797 real errors, and should be examined carefully and eliminated.
22798 In the rare case where a warning is bogus, it can be suppressed by any of
22799 the following methods:
22803 Compile with the @option{-gnatws} switch set
22806 Suppress @code{Elaboration_Check} for the called subprogram
22809 Use pragma @code{Warnings_Off} to turn warnings off for the call
22813 For the internal elaboration check case,
22814 GNAT by default generates the
22815 necessary run-time checks to ensure
22816 that @code{Program_Error} is raised if any
22817 call fails an elaboration check. Of course this can only happen if a
22818 warning has been issued as described above. The use of pragma
22819 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
22820 some of these checks, meaning that it may be possible (but is not
22821 guaranteed) for a program to be able to call a subprogram whose body
22822 is not yet elaborated, without raising a @code{Program_Error} exception.
22824 @node Controlling Elaboration in GNAT - External Calls
22825 @section Controlling Elaboration in GNAT - External Calls
22828 The previous section discussed the case in which the execution of a
22829 particular thread of elaboration code occurred entirely within a
22830 single unit. This is the easy case to handle, because a programmer
22831 has direct and total control over the order of elaboration, and
22832 furthermore, checks need only be generated in cases which are rare
22833 and which the compiler can easily detect.
22834 The situation is more complex when separate compilation is taken into account.
22835 Consider the following:
22837 @smallexample @c ada
22841 function Sqrt (Arg : Float) return Float;
22844 package body Math is
22845 function Sqrt (Arg : Float) return Float is
22854 X : Float := Math.Sqrt (0.5);
22867 where @code{Main} is the main program. When this program is executed, the
22868 elaboration code must first be executed, and one of the jobs of the
22869 binder is to determine the order in which the units of a program are
22870 to be elaborated. In this case we have four units: the spec and body
22872 the spec of @code{Stuff} and the body of @code{Main}).
22873 In what order should the four separate sections of elaboration code
22876 There are some restrictions in the order of elaboration that the binder
22877 can choose. In particular, if unit U has a @code{with}
22878 for a package @code{X}, then you
22879 are assured that the spec of @code{X}
22880 is elaborated before U , but you are
22881 not assured that the body of @code{X}
22882 is elaborated before U.
22883 This means that in the above case, the binder is allowed to choose the
22894 but that's not good, because now the call to @code{Math.Sqrt}
22895 that happens during
22896 the elaboration of the @code{Stuff}
22897 spec happens before the body of @code{Math.Sqrt} is
22898 elaborated, and hence causes @code{Program_Error} exception to be raised.
22899 At first glance, one might say that the binder is misbehaving, because
22900 obviously you want to elaborate the body of something you @code{with}
22902 that is not a general rule that can be followed in all cases. Consider
22904 @smallexample @c ada
22912 package body Y is ...
22915 package body X is ...
22921 This is a common arrangement, and, apart from the order of elaboration
22922 problems that might arise in connection with elaboration code, this works fine.
22923 A rule that says that you must first elaborate the body of anything you
22924 @code{with} cannot work in this case:
22925 the body of @code{X} @code{with}'s @code{Y},
22926 which means you would have to
22927 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
22929 you have to elaborate the body of @code{X} first, but ... and we have a
22930 loop that cannot be broken.
22932 It is true that the binder can in many cases guess an order of elaboration
22933 that is unlikely to cause a @code{Program_Error}
22934 exception to be raised, and it tries to do so (in the
22935 above example of @code{Math/Stuff/Spec}, the GNAT binder will
22937 elaborate the body of @code{Math} right after its spec, so all will be well).
22939 However, a program that blindly relies on the binder to be helpful can
22940 get into trouble, as we discussed in the previous sections, so
22942 provides a number of facilities for assisting the programmer in
22943 developing programs that are robust with respect to elaboration order.
22945 @node Default Behavior in GNAT - Ensuring Safety
22946 @section Default Behavior in GNAT - Ensuring Safety
22949 The default behavior in GNAT ensures elaboration safety. In its
22950 default mode GNAT implements the
22951 rule we previously described as the right approach. Let's restate it:
22955 @emph{If a unit has elaboration code that can directly or indirectly make a
22956 call to a subprogram in a @code{with}'ed unit, or instantiate a generic unit
22957 in a @code{with}'ed unit, then if the @code{with}'ed unit
22958 does not have pragma @code{Pure} or
22959 @code{Preelaborate}, then the client should have an
22960 @code{Elaborate_All} for the @code{with}'ed unit.}
22964 By following this rule a client is assured that calls and instantiations
22965 can be made without risk of an exception.
22967 In this mode GNAT traces all calls that are potentially made from
22968 elaboration code, and puts in any missing implicit @code{Elaborate_All}
22970 The advantage of this approach is that no elaboration problems
22971 are possible if the binder can find an elaboration order that is
22972 consistent with these implicit @code{Elaborate_All} pragmas. The
22973 disadvantage of this approach is that no such order may exist.
22975 If the binder does not generate any diagnostics, then it means that it
22976 has found an elaboration order that is guaranteed to be safe. However,
22977 the binder may still be relying on implicitly generated
22978 @code{Elaborate_All} pragmas so portability to other compilers than
22979 GNAT is not guaranteed.
22981 If it is important to guarantee portability, then the compilations should
22984 (warn on elaboration problems) switch. This will cause warning messages
22985 to be generated indicating the missing @code{Elaborate_All} pragmas.
22986 Consider the following source program:
22988 @smallexample @c ada
22993 m : integer := k.r;
23000 where it is clear that there
23001 should be a pragma @code{Elaborate_All}
23002 for unit @code{k}. An implicit pragma will be generated, and it is
23003 likely that the binder will be able to honor it. However, if you want
23004 to port this program to some other Ada compiler than GNAT.
23005 it is safer to include the pragma explicitly in the source. If this
23006 unit is compiled with the
23008 switch, then the compiler outputs a warning:
23015 3. m : integer := k.r;
23017 >>> warning: call to "r" may raise Program_Error
23018 >>> warning: missing pragma Elaborate_All for "k"
23026 and these warnings can be used as a guide for supplying manually
23027 the missing pragmas. It is usually a bad idea to use this warning
23028 option during development. That's because it will warn you when
23029 you need to put in a pragma, but cannot warn you when it is time
23030 to take it out. So the use of pragma Elaborate_All may lead to
23031 unnecessary dependencies and even false circularities.
23033 This default mode is more restrictive than the Ada Reference
23034 Manual, and it is possible to construct programs which will compile
23035 using the dynamic model described there, but will run into a
23036 circularity using the safer static model we have described.
23038 Of course any Ada compiler must be able to operate in a mode
23039 consistent with the requirements of the Ada Reference Manual,
23040 and in particular must have the capability of implementing the
23041 standard dynamic model of elaboration with run-time checks.
23043 In GNAT, this standard mode can be achieved either by the use of
23044 the @option{-gnatE} switch on the compiler (@code{gcc} or @code{gnatmake})
23045 command, or by the use of the configuration pragma:
23047 @smallexample @c ada
23048 pragma Elaboration_Checks (RM);
23052 Either approach will cause the unit affected to be compiled using the
23053 standard dynamic run-time elaboration checks described in the Ada
23054 Reference Manual. The static model is generally preferable, since it
23055 is clearly safer to rely on compile and link time checks rather than
23056 run-time checks. However, in the case of legacy code, it may be
23057 difficult to meet the requirements of the static model. This
23058 issue is further discussed in
23059 @ref{What to Do If the Default Elaboration Behavior Fails}.
23061 Note that the static model provides a strict subset of the allowed
23062 behavior and programs of the Ada Reference Manual, so if you do
23063 adhere to the static model and no circularities exist,
23064 then you are assured that your program will
23065 work using the dynamic model, providing that you remove any
23066 pragma Elaborate statements from the source.
23068 @node Treatment of Pragma Elaborate
23069 @section Treatment of Pragma Elaborate
23070 @cindex Pragma Elaborate
23073 The use of @code{pragma Elaborate}
23074 should generally be avoided in Ada 95 programs.
23075 The reason for this is that there is no guarantee that transitive calls
23076 will be properly handled. Indeed at one point, this pragma was placed
23077 in Annex J (Obsolescent Features), on the grounds that it is never useful.
23079 Now that's a bit restrictive. In practice, the case in which
23080 @code{pragma Elaborate} is useful is when the caller knows that there
23081 are no transitive calls, or that the called unit contains all necessary
23082 transitive @code{pragma Elaborate} statements, and legacy code often
23083 contains such uses.
23085 Strictly speaking the static mode in GNAT should ignore such pragmas,
23086 since there is no assurance at compile time that the necessary safety
23087 conditions are met. In practice, this would cause GNAT to be incompatible
23088 with correctly written Ada 83 code that had all necessary
23089 @code{pragma Elaborate} statements in place. Consequently, we made the
23090 decision that GNAT in its default mode will believe that if it encounters
23091 a @code{pragma Elaborate} then the programmer knows what they are doing,
23092 and it will trust that no elaboration errors can occur.
23094 The result of this decision is two-fold. First to be safe using the
23095 static mode, you should remove all @code{pragma Elaborate} statements.
23096 Second, when fixing circularities in existing code, you can selectively
23097 use @code{pragma Elaborate} statements to convince the static mode of
23098 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
23101 When using the static mode with @option{-gnatwl}, any use of
23102 @code{pragma Elaborate} will generate a warning about possible
23105 @node Elaboration Issues for Library Tasks
23106 @section Elaboration Issues for Library Tasks
23107 @cindex Library tasks, elaboration issues
23108 @cindex Elaboration of library tasks
23111 In this section we examine special elaboration issues that arise for
23112 programs that declare library level tasks.
23114 Generally the model of execution of an Ada program is that all units are
23115 elaborated, and then execution of the program starts. However, the
23116 declaration of library tasks definitely does not fit this model. The
23117 reason for this is that library tasks start as soon as they are declared
23118 (more precisely, as soon as the statement part of the enclosing package
23119 body is reached), that is to say before elaboration
23120 of the program is complete. This means that if such a task calls a
23121 subprogram, or an entry in another task, the callee may or may not be
23122 elaborated yet, and in the standard
23123 Reference Manual model of dynamic elaboration checks, you can even
23124 get timing dependent Program_Error exceptions, since there can be
23125 a race between the elaboration code and the task code.
23127 The static model of elaboration in GNAT seeks to avoid all such
23128 dynamic behavior, by being conservative, and the conservative
23129 approach in this particular case is to assume that all the code
23130 in a task body is potentially executed at elaboration time if
23131 a task is declared at the library level.
23133 This can definitely result in unexpected circularities. Consider
23134 the following example
23136 @smallexample @c ada
23142 type My_Int is new Integer;
23144 function Ident (M : My_Int) return My_Int;
23148 package body Decls is
23149 task body Lib_Task is
23155 function Ident (M : My_Int) return My_Int is
23163 procedure Put_Val (Arg : Decls.My_Int);
23167 package body Utils is
23168 procedure Put_Val (Arg : Decls.My_Int) is
23170 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23177 Decls.Lib_Task.Start;
23182 If the above example is compiled in the default static elaboration
23183 mode, then a circularity occurs. The circularity comes from the call
23184 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
23185 this call occurs in elaboration code, we need an implicit pragma
23186 @code{Elaborate_All} for @code{Utils}. This means that not only must
23187 the spec and body of @code{Utils} be elaborated before the body
23188 of @code{Decls}, but also the spec and body of any unit that is
23189 @code{with'ed} by the body of @code{Utils} must also be elaborated before
23190 the body of @code{Decls}. This is the transitive implication of
23191 pragma @code{Elaborate_All} and it makes sense, because in general
23192 the body of @code{Put_Val} might have a call to something in a
23193 @code{with'ed} unit.
23195 In this case, the body of Utils (actually its spec) @code{with's}
23196 @code{Decls}. Unfortunately this means that the body of @code{Decls}
23197 must be elaborated before itself, in case there is a call from the
23198 body of @code{Utils}.
23200 Here is the exact chain of events we are worrying about:
23204 In the body of @code{Decls} a call is made from within the body of a library
23205 task to a subprogram in the package @code{Utils}. Since this call may
23206 occur at elaboration time (given that the task is activated at elaboration
23207 time), we have to assume the worst, i.e. that the
23208 call does happen at elaboration time.
23211 This means that the body and spec of @code{Util} must be elaborated before
23212 the body of @code{Decls} so that this call does not cause an access before
23216 Within the body of @code{Util}, specifically within the body of
23217 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
23221 One such @code{with}'ed package is package @code{Decls}, so there
23222 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
23223 In fact there is such a call in this example, but we would have to
23224 assume that there was such a call even if it were not there, since
23225 we are not supposed to write the body of @code{Decls} knowing what
23226 is in the body of @code{Utils}; certainly in the case of the
23227 static elaboration model, the compiler does not know what is in
23228 other bodies and must assume the worst.
23231 This means that the spec and body of @code{Decls} must also be
23232 elaborated before we elaborate the unit containing the call, but
23233 that unit is @code{Decls}! This means that the body of @code{Decls}
23234 must be elaborated before itself, and that's a circularity.
23238 Indeed, if you add an explicit pragma Elaborate_All for @code{Utils} in
23239 the body of @code{Decls} you will get a true Ada Reference Manual
23240 circularity that makes the program illegal.
23242 In practice, we have found that problems with the static model of
23243 elaboration in existing code often arise from library tasks, so
23244 we must address this particular situation.
23246 Note that if we compile and run the program above, using the dynamic model of
23247 elaboration (that is to say use the @option{-gnatE} switch),
23248 then it compiles, binds,
23249 links, and runs, printing the expected result of 2. Therefore in some sense
23250 the circularity here is only apparent, and we need to capture
23251 the properties of this program that distinguish it from other library-level
23252 tasks that have real elaboration problems.
23254 We have four possible answers to this question:
23259 Use the dynamic model of elaboration.
23261 If we use the @option{-gnatE} switch, then as noted above, the program works.
23262 Why is this? If we examine the task body, it is apparent that the task cannot
23264 @code{accept} statement until after elaboration has been completed, because
23265 the corresponding entry call comes from the main program, not earlier.
23266 This is why the dynamic model works here. But that's really giving
23267 up on a precise analysis, and we prefer to take this approach only if we cannot
23269 problem in any other manner. So let us examine two ways to reorganize
23270 the program to avoid the potential elaboration problem.
23273 Split library tasks into separate packages.
23275 Write separate packages, so that library tasks are isolated from
23276 other declarations as much as possible. Let us look at a variation on
23279 @smallexample @c ada
23287 package body Decls1 is
23288 task body Lib_Task is
23296 type My_Int is new Integer;
23297 function Ident (M : My_Int) return My_Int;
23301 package body Decls2 is
23302 function Ident (M : My_Int) return My_Int is
23310 procedure Put_Val (Arg : Decls2.My_Int);
23314 package body Utils is
23315 procedure Put_Val (Arg : Decls2.My_Int) is
23317 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
23324 Decls1.Lib_Task.Start;
23329 All we have done is to split @code{Decls} into two packages, one
23330 containing the library task, and one containing everything else. Now
23331 there is no cycle, and the program compiles, binds, links and executes
23332 using the default static model of elaboration.
23335 Declare separate task types.
23337 A significant part of the problem arises because of the use of the
23338 single task declaration form. This means that the elaboration of
23339 the task type, and the elaboration of the task itself (i.e. the
23340 creation of the task) happen at the same time. A good rule
23341 of style in Ada 95 is to always create explicit task types. By
23342 following the additional step of placing task objects in separate
23343 packages from the task type declaration, many elaboration problems
23344 are avoided. Here is another modified example of the example program:
23346 @smallexample @c ada
23348 task type Lib_Task_Type is
23352 type My_Int is new Integer;
23354 function Ident (M : My_Int) return My_Int;
23358 package body Decls is
23359 task body Lib_Task_Type is
23365 function Ident (M : My_Int) return My_Int is
23373 procedure Put_Val (Arg : Decls.My_Int);
23377 package body Utils is
23378 procedure Put_Val (Arg : Decls.My_Int) is
23380 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23386 Lib_Task : Decls.Lib_Task_Type;
23392 Declst.Lib_Task.Start;
23397 What we have done here is to replace the @code{task} declaration in
23398 package @code{Decls} with a @code{task type} declaration. Then we
23399 introduce a separate package @code{Declst} to contain the actual
23400 task object. This separates the elaboration issues for
23401 the @code{task type}
23402 declaration, which causes no trouble, from the elaboration issues
23403 of the task object, which is also unproblematic, since it is now independent
23404 of the elaboration of @code{Utils}.
23405 This separation of concerns also corresponds to
23406 a generally sound engineering principle of separating declarations
23407 from instances. This version of the program also compiles, binds, links,
23408 and executes, generating the expected output.
23411 Use No_Entry_Calls_In_Elaboration_Code restriction.
23412 @cindex No_Entry_Calls_In_Elaboration_Code
23414 The previous two approaches described how a program can be restructured
23415 to avoid the special problems caused by library task bodies. in practice,
23416 however, such restructuring may be difficult to apply to existing legacy code,
23417 so we must consider solutions that do not require massive rewriting.
23419 Let us consider more carefully why our original sample program works
23420 under the dynamic model of elaboration. The reason is that the code
23421 in the task body blocks immediately on the @code{accept}
23422 statement. Now of course there is nothing to prohibit elaboration
23423 code from making entry calls (for example from another library level task),
23424 so we cannot tell in isolation that
23425 the task will not execute the accept statement during elaboration.
23427 However, in practice it is very unusual to see elaboration code
23428 make any entry calls, and the pattern of tasks starting
23429 at elaboration time and then immediately blocking on @code{accept} or
23430 @code{select} statements is very common. What this means is that
23431 the compiler is being too pessimistic when it analyzes the
23432 whole package body as though it might be executed at elaboration
23435 If we know that the elaboration code contains no entry calls, (a very safe
23436 assumption most of the time, that could almost be made the default
23437 behavior), then we can compile all units of the program under control
23438 of the following configuration pragma:
23441 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
23445 This pragma can be placed in the @file{gnat.adc} file in the usual
23446 manner. If we take our original unmodified program and compile it
23447 in the presence of a @file{gnat.adc} containing the above pragma,
23448 then once again, we can compile, bind, link, and execute, obtaining
23449 the expected result. In the presence of this pragma, the compiler does
23450 not trace calls in a task body, that appear after the first @code{accept}
23451 or @code{select} statement, and therefore does not report a potential
23452 circularity in the original program.
23454 The compiler will check to the extent it can that the above
23455 restriction is not violated, but it is not always possible to do a
23456 complete check at compile time, so it is important to use this
23457 pragma only if the stated restriction is in fact met, that is to say
23458 no task receives an entry call before elaboration of all units is completed.
23462 @node Mixing Elaboration Models
23463 @section Mixing Elaboration Models
23465 So far, we have assumed that the entire program is either compiled
23466 using the dynamic model or static model, ensuring consistency. It
23467 is possible to mix the two models, but rules have to be followed
23468 if this mixing is done to ensure that elaboration checks are not
23471 The basic rule is that @emph{a unit compiled with the static model cannot
23472 be @code{with'ed} by a unit compiled with the dynamic model}. The
23473 reason for this is that in the static model, a unit assumes that
23474 its clients guarantee to use (the equivalent of) pragma
23475 @code{Elaborate_All} so that no elaboration checks are required
23476 in inner subprograms, and this assumption is violated if the
23477 client is compiled with dynamic checks.
23479 The precise rule is as follows. A unit that is compiled with dynamic
23480 checks can only @code{with} a unit that meets at least one of the
23481 following criteria:
23486 The @code{with'ed} unit is itself compiled with dynamic elaboration
23487 checks (that is with the @option{-gnatE} switch.
23490 The @code{with'ed} unit is an internal GNAT implementation unit from
23491 the System, Interfaces, Ada, or GNAT hierarchies.
23494 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
23497 The @code{with'ing} unit (that is the client) has an explicit pragma
23498 @code{Elaborate_All} for the @code{with'ed} unit.
23503 If this rule is violated, that is if a unit with dynamic elaboration
23504 checks @code{with's} a unit that does not meet one of the above four
23505 criteria, then the binder (@code{gnatbind}) will issue a warning
23506 similar to that in the following example:
23509 warning: "x.ads" has dynamic elaboration checks and with's
23510 warning: "y.ads" which has static elaboration checks
23514 These warnings indicate that the rule has been violated, and that as a result
23515 elaboration checks may be missed in the resulting executable file.
23516 This warning may be suppressed using the @option{-ws} binder switch
23517 in the usual manner.
23519 One useful application of this mixing rule is in the case of a subsystem
23520 which does not itself @code{with} units from the remainder of the
23521 application. In this case, the entire subsystem can be compiled with
23522 dynamic checks to resolve a circularity in the subsystem, while
23523 allowing the main application that uses this subsystem to be compiled
23524 using the more reliable default static model.
23526 @node What to Do If the Default Elaboration Behavior Fails
23527 @section What to Do If the Default Elaboration Behavior Fails
23530 If the binder cannot find an acceptable order, it outputs detailed
23531 diagnostics. For example:
23537 error: elaboration circularity detected
23538 info: "proc (body)" must be elaborated before "pack (body)"
23539 info: reason: Elaborate_All probably needed in unit "pack (body)"
23540 info: recompile "pack (body)" with -gnatwl
23541 info: for full details
23542 info: "proc (body)"
23543 info: is needed by its spec:
23544 info: "proc (spec)"
23545 info: which is withed by:
23546 info: "pack (body)"
23547 info: "pack (body)" must be elaborated before "proc (body)"
23548 info: reason: pragma Elaborate in unit "proc (body)"
23554 In this case we have a cycle that the binder cannot break. On the one
23555 hand, there is an explicit pragma Elaborate in @code{proc} for
23556 @code{pack}. This means that the body of @code{pack} must be elaborated
23557 before the body of @code{proc}. On the other hand, there is elaboration
23558 code in @code{pack} that calls a subprogram in @code{proc}. This means
23559 that for maximum safety, there should really be a pragma
23560 Elaborate_All in @code{pack} for @code{proc} which would require that
23561 the body of @code{proc} be elaborated before the body of
23562 @code{pack}. Clearly both requirements cannot be satisfied.
23563 Faced with a circularity of this kind, you have three different options.
23566 @item Fix the program
23567 The most desirable option from the point of view of long-term maintenance
23568 is to rearrange the program so that the elaboration problems are avoided.
23569 One useful technique is to place the elaboration code into separate
23570 child packages. Another is to move some of the initialization code to
23571 explicitly called subprograms, where the program controls the order
23572 of initialization explicitly. Although this is the most desirable option,
23573 it may be impractical and involve too much modification, especially in
23574 the case of complex legacy code.
23576 @item Perform dynamic checks
23577 If the compilations are done using the
23579 (dynamic elaboration check) switch, then GNAT behaves in
23580 a quite different manner. Dynamic checks are generated for all calls
23581 that could possibly result in raising an exception. With this switch,
23582 the compiler does not generate implicit @code{Elaborate_All} pragmas.
23583 The behavior then is exactly as specified in the Ada 95 Reference Manual.
23584 The binder will generate an executable program that may or may not
23585 raise @code{Program_Error}, and then it is the programmer's job to ensure
23586 that it does not raise an exception. Note that it is important to
23587 compile all units with the switch, it cannot be used selectively.
23589 @item Suppress checks
23590 The drawback of dynamic checks is that they generate a
23591 significant overhead at run time, both in space and time. If you
23592 are absolutely sure that your program cannot raise any elaboration
23593 exceptions, and you still want to use the dynamic elaboration model,
23594 then you can use the configuration pragma
23595 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
23596 example this pragma could be placed in the @file{gnat.adc} file.
23598 @item Suppress checks selectively
23599 When you know that certain calls in elaboration code cannot possibly
23600 lead to an elaboration error, and the binder nevertheless generates warnings
23601 on those calls and inserts Elaborate_All pragmas that lead to elaboration
23602 circularities, it is possible to remove those warnings locally and obtain
23603 a program that will bind. Clearly this can be unsafe, and it is the
23604 responsibility of the programmer to make sure that the resulting program has
23605 no elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can
23606 be used with different granularity to suppress warnings and break
23607 elaboration circularities:
23611 Place the pragma that names the called subprogram in the declarative part
23612 that contains the call.
23615 Place the pragma in the declarative part, without naming an entity. This
23616 disables warnings on all calls in the corresponding declarative region.
23619 Place the pragma in the package spec that declares the called subprogram,
23620 and name the subprogram. This disables warnings on all elaboration calls to
23624 Place the pragma in the package spec that declares the called subprogram,
23625 without naming any entity. This disables warnings on all elaboration calls to
23626 all subprograms declared in this spec.
23628 @item Use Pragma Elaborate
23629 As previously described in section @xref{Treatment of Pragma Elaborate},
23630 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
23631 that no elaboration checks are required on calls to the designated unit.
23632 There may be cases in which the caller knows that no transitive calls
23633 can occur, so that a @code{pragma Elaborate} will be sufficient in a
23634 case where @code{pragma Elaborate_All} would cause a circularity.
23638 These five cases are listed in order of decreasing safety, and therefore
23639 require increasing programmer care in their application. Consider the
23642 @smallexample @c adanocomment
23644 function F1 return Integer;
23649 function F2 return Integer;
23650 function Pure (x : integer) return integer;
23651 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
23652 -- pragma Suppress (Elaboration_Check); -- (4)
23656 package body Pack1 is
23657 function F1 return Integer is
23661 Val : integer := Pack2.Pure (11); -- Elab. call (1)
23664 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
23665 -- pragma Suppress(Elaboration_Check); -- (2)
23667 X1 := Pack2.F2 + 1; -- Elab. call (2)
23672 package body Pack2 is
23673 function F2 return Integer is
23677 function Pure (x : integer) return integer is
23679 return x ** 3 - 3 * x;
23683 with Pack1, Ada.Text_IO;
23686 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
23689 In the absence of any pragmas, an attempt to bind this program produces
23690 the following diagnostics:
23696 error: elaboration circularity detected
23697 info: "pack1 (body)" must be elaborated before "pack1 (body)"
23698 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
23699 info: recompile "pack1 (body)" with -gnatwl for full details
23700 info: "pack1 (body)"
23701 info: must be elaborated along with its spec:
23702 info: "pack1 (spec)"
23703 info: which is withed by:
23704 info: "pack2 (body)"
23705 info: which must be elaborated along with its spec:
23706 info: "pack2 (spec)"
23707 info: which is withed by:
23708 info: "pack1 (body)"
23711 The sources of the circularity are the two calls to @code{Pack2.Pure} and
23712 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
23713 F2 is safe, even though F2 calls F1, because the call appears after the
23714 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
23715 remove the warning on the call. It is also possible to use pragma (2)
23716 because there are no other potentially unsafe calls in the block.
23719 The call to @code{Pure} is safe because this function does not depend on the
23720 state of @code{Pack2}. Therefore any call to this function is safe, and it
23721 is correct to place pragma (3) in the corresponding package spec.
23724 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
23725 warnings on all calls to functions declared therein. Note that this is not
23726 necessarily safe, and requires more detailed examination of the subprogram
23727 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
23728 be already elaborated.
23732 It is hard to generalize on which of these four approaches should be
23733 taken. Obviously if it is possible to fix the program so that the default
23734 treatment works, this is preferable, but this may not always be practical.
23735 It is certainly simple enough to use
23737 but the danger in this case is that, even if the GNAT binder
23738 finds a correct elaboration order, it may not always do so,
23739 and certainly a binder from another Ada compiler might not. A
23740 combination of testing and analysis (for which the warnings generated
23743 switch can be useful) must be used to ensure that the program is free
23744 of errors. One switch that is useful in this testing is the
23745 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
23748 Normally the binder tries to find an order that has the best chance of
23749 of avoiding elaboration problems. With this switch, the binder
23750 plays a devil's advocate role, and tries to choose the order that
23751 has the best chance of failing. If your program works even with this
23752 switch, then it has a better chance of being error free, but this is still
23755 For an example of this approach in action, consider the C-tests (executable
23756 tests) from the ACVC suite. If these are compiled and run with the default
23757 treatment, then all but one of them succeed without generating any error
23758 diagnostics from the binder. However, there is one test that fails, and
23759 this is not surprising, because the whole point of this test is to ensure
23760 that the compiler can handle cases where it is impossible to determine
23761 a correct order statically, and it checks that an exception is indeed
23762 raised at run time.
23764 This one test must be compiled and run using the
23766 switch, and then it passes. Alternatively, the entire suite can
23767 be run using this switch. It is never wrong to run with the dynamic
23768 elaboration switch if your code is correct, and we assume that the
23769 C-tests are indeed correct (it is less efficient, but efficiency is
23770 not a factor in running the ACVC tests.)
23772 @node Elaboration for Access-to-Subprogram Values
23773 @section Elaboration for Access-to-Subprogram Values
23774 @cindex Access-to-subprogram
23777 The introduction of access-to-subprogram types in Ada 95 complicates
23778 the handling of elaboration. The trouble is that it becomes
23779 impossible to tell at compile time which procedure
23780 is being called. This means that it is not possible for the binder
23781 to analyze the elaboration requirements in this case.
23783 If at the point at which the access value is created
23784 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
23785 the body of the subprogram is
23786 known to have been elaborated, then the access value is safe, and its use
23787 does not require a check. This may be achieved by appropriate arrangement
23788 of the order of declarations if the subprogram is in the current unit,
23789 or, if the subprogram is in another unit, by using pragma
23790 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
23791 on the referenced unit.
23793 If the referenced body is not known to have been elaborated at the point
23794 the access value is created, then any use of the access value must do a
23795 dynamic check, and this dynamic check will fail and raise a
23796 @code{Program_Error} exception if the body has not been elaborated yet.
23797 GNAT will generate the necessary checks, and in addition, if the
23799 switch is set, will generate warnings that such checks are required.
23801 The use of dynamic dispatching for tagged types similarly generates
23802 a requirement for dynamic checks, and premature calls to any primitive
23803 operation of a tagged type before the body of the operation has been
23804 elaborated, will result in the raising of @code{Program_Error}.
23806 @node Summary of Procedures for Elaboration Control
23807 @section Summary of Procedures for Elaboration Control
23808 @cindex Elaboration control
23811 First, compile your program with the default options, using none of
23812 the special elaboration control switches. If the binder successfully
23813 binds your program, then you can be confident that, apart from issues
23814 raised by the use of access-to-subprogram types and dynamic dispatching,
23815 the program is free of elaboration errors. If it is important that the
23816 program be portable, then use the
23818 switch to generate warnings about missing @code{Elaborate_All}
23819 pragmas, and supply the missing pragmas.
23821 If the program fails to bind using the default static elaboration
23822 handling, then you can fix the program to eliminate the binder
23823 message, or recompile the entire program with the
23824 @option{-gnatE} switch to generate dynamic elaboration checks,
23825 and, if you are sure there really are no elaboration problems,
23826 use a global pragma @code{Suppress (Elaboration_Check)}.
23828 @node Other Elaboration Order Considerations
23829 @section Other Elaboration Order Considerations
23831 This section has been entirely concerned with the issue of finding a valid
23832 elaboration order, as defined by the Ada Reference Manual. In a case
23833 where several elaboration orders are valid, the task is to find one
23834 of the possible valid elaboration orders (and the static model in GNAT
23835 will ensure that this is achieved).
23837 The purpose of the elaboration rules in the Ada Reference Manual is to
23838 make sure that no entity is accessed before it has been elaborated. For
23839 a subprogram, this means that the spec and body must have been elaborated
23840 before the subprogram is called. For an object, this means that the object
23841 must have been elaborated before its value is read or written. A violation
23842 of either of these two requirements is an access before elaboration order,
23843 and this section has been all about avoiding such errors.
23845 In the case where more than one order of elaboration is possible, in the
23846 sense that access before elaboration errors are avoided, then any one of
23847 the orders is ``correct'' in the sense that it meets the requirements of
23848 the Ada Reference Manual, and no such error occurs.
23850 However, it may be the case for a given program, that there are
23851 constraints on the order of elaboration that come not from consideration
23852 of avoiding elaboration errors, but rather from extra-lingual logic
23853 requirements. Consider this example:
23855 @smallexample @c ada
23856 with Init_Constants;
23857 package Constants is
23862 package Init_Constants is
23863 procedure P; -- require a body
23864 end Init_Constants;
23867 package body Init_Constants is
23868 procedure P is begin null; end;
23872 end Init_Constants;
23876 Z : Integer := Constants.X + Constants.Y;
23880 with Text_IO; use Text_IO;
23883 Put_Line (Calc.Z'Img);
23888 In this example, there is more than one valid order of elaboration. For
23889 example both the following are correct orders:
23892 Init_Constants spec
23895 Init_Constants body
23900 Init_Constants spec
23901 Init_Constants body
23908 There is no language rule to prefer one or the other, both are correct
23909 from an order of elaboration point of view. But the programmatic effects
23910 of the two orders are very different. In the first, the elaboration routine
23911 of @code{Calc} initializes @code{Z} to zero, and then the main program
23912 runs with this value of zero. But in the second order, the elaboration
23913 routine of @code{Calc} runs after the body of Init_Constants has set
23914 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
23917 One could perhaps by applying pretty clever non-artificial intelligence
23918 to the situation guess that it is more likely that the second order of
23919 elaboration is the one desired, but there is no formal linguistic reason
23920 to prefer one over the other. In fact in this particular case, GNAT will
23921 prefer the second order, because of the rule that bodies are elaborated
23922 as soon as possible, but it's just luck that this is what was wanted
23923 (if indeed the second order was preferred).
23925 If the program cares about the order of elaboration routines in a case like
23926 this, it is important to specify the order required. In this particular
23927 case, that could have been achieved by adding to the spec of Calc:
23929 @smallexample @c ada
23930 pragma Elaborate_All (Constants);
23934 which requires that the body (if any) and spec of @code{Constants},
23935 as well as the body and spec of any unit @code{with}'ed by
23936 @code{Constants} be elaborated before @code{Calc} is elaborated.
23938 Clearly no automatic method can always guess which alternative you require,
23939 and if you are working with legacy code that had constraints of this kind
23940 which were not properly specified by adding @code{Elaborate} or
23941 @code{Elaborate_All} pragmas, then indeed it is possible that two different
23942 compilers can choose different orders.
23944 The @code{gnatbind}
23945 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
23946 out problems. This switch causes bodies to be elaborated as late as possible
23947 instead of as early as possible. In the example above, it would have forced
23948 the choice of the first elaboration order. If you get different results
23949 when using this switch, and particularly if one set of results is right,
23950 and one is wrong as far as you are concerned, it shows that you have some
23951 missing @code{Elaborate} pragmas. For the example above, we have the
23955 gnatmake -f -q main
23958 gnatmake -f -q main -bargs -p
23964 It is of course quite unlikely that both these results are correct, so
23965 it is up to you in a case like this to investigate the source of the
23966 difference, by looking at the two elaboration orders that are chosen,
23967 and figuring out which is correct, and then adding the necessary
23968 @code{Elaborate_All} pragmas to ensure the desired order.
23971 @node Inline Assembler
23972 @appendix Inline Assembler
23975 If you need to write low-level software that interacts directly
23976 with the hardware, Ada provides two ways to incorporate assembly
23977 language code into your program. First, you can import and invoke
23978 external routines written in assembly language, an Ada feature fully
23979 supported by GNAT. However, for small sections of code it may be simpler
23980 or more efficient to include assembly language statements directly
23981 in your Ada source program, using the facilities of the implementation-defined
23982 package @code{System.Machine_Code}, which incorporates the gcc
23983 Inline Assembler. The Inline Assembler approach offers a number of advantages,
23984 including the following:
23987 @item No need to use non-Ada tools
23988 @item Consistent interface over different targets
23989 @item Automatic usage of the proper calling conventions
23990 @item Access to Ada constants and variables
23991 @item Definition of intrinsic routines
23992 @item Possibility of inlining a subprogram comprising assembler code
23993 @item Code optimizer can take Inline Assembler code into account
23996 This chapter presents a series of examples to show you how to use
23997 the Inline Assembler. Although it focuses on the Intel x86,
23998 the general approach applies also to other processors.
23999 It is assumed that you are familiar with Ada
24000 and with assembly language programming.
24003 * Basic Assembler Syntax::
24004 * A Simple Example of Inline Assembler::
24005 * Output Variables in Inline Assembler::
24006 * Input Variables in Inline Assembler::
24007 * Inlining Inline Assembler Code::
24008 * Other Asm Functionality::
24009 * A Complete Example::
24012 @c ---------------------------------------------------------------------------
24013 @node Basic Assembler Syntax
24014 @section Basic Assembler Syntax
24017 The assembler used by GNAT and gcc is based not on the Intel assembly
24018 language, but rather on a language that descends from the AT&T Unix
24019 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
24020 The following table summarizes the main features of @emph{as} syntax
24021 and points out the differences from the Intel conventions.
24022 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
24023 pre-processor) documentation for further information.
24026 @item Register names
24027 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
24029 Intel: No extra punctuation; for example @code{eax}
24031 @item Immediate operand
24032 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
24034 Intel: No extra punctuation; for example @code{4}
24037 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
24039 Intel: No extra punctuation; for example @code{loc}
24041 @item Memory contents
24042 gcc / @emph{as}: No extra punctuation; for example @code{loc}
24044 Intel: Square brackets; for example @code{[loc]}
24046 @item Register contents
24047 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
24049 Intel: Square brackets; for example @code{[eax]}
24051 @item Hexadecimal numbers
24052 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
24054 Intel: Trailing ``h''; for example @code{A0h}
24057 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
24060 Intel: Implicit, deduced by assembler; for example @code{mov}
24062 @item Instruction repetition
24063 gcc / @emph{as}: Split into two lines; for example
24069 Intel: Keep on one line; for example @code{rep stosl}
24071 @item Order of operands
24072 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
24074 Intel: Destination first; for example @code{mov eax, 4}
24077 @c ---------------------------------------------------------------------------
24078 @node A Simple Example of Inline Assembler
24079 @section A Simple Example of Inline Assembler
24082 The following example will generate a single assembly language statement,
24083 @code{nop}, which does nothing. Despite its lack of run-time effect,
24084 the example will be useful in illustrating the basics of
24085 the Inline Assembler facility.
24087 @smallexample @c ada
24089 with System.Machine_Code; use System.Machine_Code;
24090 procedure Nothing is
24097 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
24098 here it takes one parameter, a @emph{template string} that must be a static
24099 expression and that will form the generated instruction.
24100 @code{Asm} may be regarded as a compile-time procedure that parses
24101 the template string and additional parameters (none here),
24102 from which it generates a sequence of assembly language instructions.
24104 The examples in this chapter will illustrate several of the forms
24105 for invoking @code{Asm}; a complete specification of the syntax
24106 is found in the @cite{GNAT Reference Manual}.
24108 Under the standard GNAT conventions, the @code{Nothing} procedure
24109 should be in a file named @file{nothing.adb}.
24110 You can build the executable in the usual way:
24114 However, the interesting aspect of this example is not its run-time behavior
24115 but rather the generated assembly code.
24116 To see this output, invoke the compiler as follows:
24118 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
24120 where the options are:
24124 compile only (no bind or link)
24126 generate assembler listing
24127 @item -fomit-frame-pointer
24128 do not set up separate stack frames
24130 do not add runtime checks
24133 This gives a human-readable assembler version of the code. The resulting
24134 file will have the same name as the Ada source file, but with a @code{.s}
24135 extension. In our example, the file @file{nothing.s} has the following
24140 .file "nothing.adb"
24142 ___gnu_compiled_ada:
24145 .globl __ada_nothing
24157 The assembly code you included is clearly indicated by
24158 the compiler, between the @code{#APP} and @code{#NO_APP}
24159 delimiters. The character before the 'APP' and 'NOAPP'
24160 can differ on different targets. For example, GNU/Linux uses '#APP' while
24161 on NT you will see '/APP'.
24163 If you make a mistake in your assembler code (such as using the
24164 wrong size modifier, or using a wrong operand for the instruction) GNAT
24165 will report this error in a temporary file, which will be deleted when
24166 the compilation is finished. Generating an assembler file will help
24167 in such cases, since you can assemble this file separately using the
24168 @emph{as} assembler that comes with gcc.
24170 Assembling the file using the command
24173 as @file{nothing.s}
24176 will give you error messages whose lines correspond to the assembler
24177 input file, so you can easily find and correct any mistakes you made.
24178 If there are no errors, @emph{as} will generate an object file
24179 @file{nothing.out}.
24181 @c ---------------------------------------------------------------------------
24182 @node Output Variables in Inline Assembler
24183 @section Output Variables in Inline Assembler
24186 The examples in this section, showing how to access the processor flags,
24187 illustrate how to specify the destination operands for assembly language
24190 @smallexample @c ada
24192 with Interfaces; use Interfaces;
24193 with Ada.Text_IO; use Ada.Text_IO;
24194 with System.Machine_Code; use System.Machine_Code;
24195 procedure Get_Flags is
24196 Flags : Unsigned_32;
24199 Asm ("pushfl" & LF & HT & -- push flags on stack
24200 "popl %%eax" & LF & HT & -- load eax with flags
24201 "movl %%eax, %0", -- store flags in variable
24202 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24203 Put_Line ("Flags register:" & Flags'Img);
24208 In order to have a nicely aligned assembly listing, we have separated
24209 multiple assembler statements in the Asm template string with linefeed
24210 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
24211 The resulting section of the assembly output file is:
24218 movl %eax, -40(%ebp)
24223 It would have been legal to write the Asm invocation as:
24226 Asm ("pushfl popl %%eax movl %%eax, %0")
24229 but in the generated assembler file, this would come out as:
24233 pushfl popl %eax movl %eax, -40(%ebp)
24237 which is not so convenient for the human reader.
24239 We use Ada comments
24240 at the end of each line to explain what the assembler instructions
24241 actually do. This is a useful convention.
24243 When writing Inline Assembler instructions, you need to precede each register
24244 and variable name with a percent sign. Since the assembler already requires
24245 a percent sign at the beginning of a register name, you need two consecutive
24246 percent signs for such names in the Asm template string, thus @code{%%eax}.
24247 In the generated assembly code, one of the percent signs will be stripped off.
24249 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
24250 variables: operands you later define using @code{Input} or @code{Output}
24251 parameters to @code{Asm}.
24252 An output variable is illustrated in
24253 the third statement in the Asm template string:
24257 The intent is to store the contents of the eax register in a variable that can
24258 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
24259 necessarily work, since the compiler might optimize by using a register
24260 to hold Flags, and the expansion of the @code{movl} instruction would not be
24261 aware of this optimization. The solution is not to store the result directly
24262 but rather to advise the compiler to choose the correct operand form;
24263 that is the purpose of the @code{%0} output variable.
24265 Information about the output variable is supplied in the @code{Outputs}
24266 parameter to @code{Asm}:
24268 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24271 The output is defined by the @code{Asm_Output} attribute of the target type;
24272 the general format is
24274 Type'Asm_Output (constraint_string, variable_name)
24277 The constraint string directs the compiler how
24278 to store/access the associated variable. In the example
24280 Unsigned_32'Asm_Output ("=m", Flags);
24282 the @code{"m"} (memory) constraint tells the compiler that the variable
24283 @code{Flags} should be stored in a memory variable, thus preventing
24284 the optimizer from keeping it in a register. In contrast,
24286 Unsigned_32'Asm_Output ("=r", Flags);
24288 uses the @code{"r"} (register) constraint, telling the compiler to
24289 store the variable in a register.
24291 If the constraint is preceded by the equal character (@strong{=}), it tells
24292 the compiler that the variable will be used to store data into it.
24294 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
24295 allowing the optimizer to choose whatever it deems best.
24297 There are a fairly large number of constraints, but the ones that are
24298 most useful (for the Intel x86 processor) are the following:
24304 global (i.e. can be stored anywhere)
24322 use one of eax, ebx, ecx or edx
24324 use one of eax, ebx, ecx, edx, esi or edi
24327 The full set of constraints is described in the gcc and @emph{as}
24328 documentation; note that it is possible to combine certain constraints
24329 in one constraint string.
24331 You specify the association of an output variable with an assembler operand
24332 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
24334 @smallexample @c ada
24336 Asm ("pushfl" & LF & HT & -- push flags on stack
24337 "popl %%eax" & LF & HT & -- load eax with flags
24338 "movl %%eax, %0", -- store flags in variable
24339 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24343 @code{%0} will be replaced in the expanded code by the appropriate operand,
24345 the compiler decided for the @code{Flags} variable.
24347 In general, you may have any number of output variables:
24350 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
24352 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
24353 of @code{Asm_Output} attributes
24357 @smallexample @c ada
24359 Asm ("movl %%eax, %0" & LF & HT &
24360 "movl %%ebx, %1" & LF & HT &
24362 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
24363 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
24364 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
24368 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
24369 in the Ada program.
24371 As a variation on the @code{Get_Flags} example, we can use the constraints
24372 string to direct the compiler to store the eax register into the @code{Flags}
24373 variable, instead of including the store instruction explicitly in the
24374 @code{Asm} template string:
24376 @smallexample @c ada
24378 with Interfaces; use Interfaces;
24379 with Ada.Text_IO; use Ada.Text_IO;
24380 with System.Machine_Code; use System.Machine_Code;
24381 procedure Get_Flags_2 is
24382 Flags : Unsigned_32;
24385 Asm ("pushfl" & LF & HT & -- push flags on stack
24386 "popl %%eax", -- save flags in eax
24387 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
24388 Put_Line ("Flags register:" & Flags'Img);
24394 The @code{"a"} constraint tells the compiler that the @code{Flags}
24395 variable will come from the eax register. Here is the resulting code:
24403 movl %eax,-40(%ebp)
24408 The compiler generated the store of eax into Flags after
24409 expanding the assembler code.
24411 Actually, there was no need to pop the flags into the eax register;
24412 more simply, we could just pop the flags directly into the program variable:
24414 @smallexample @c ada
24416 with Interfaces; use Interfaces;
24417 with Ada.Text_IO; use Ada.Text_IO;
24418 with System.Machine_Code; use System.Machine_Code;
24419 procedure Get_Flags_3 is
24420 Flags : Unsigned_32;
24423 Asm ("pushfl" & LF & HT & -- push flags on stack
24424 "pop %0", -- save flags in Flags
24425 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24426 Put_Line ("Flags register:" & Flags'Img);
24431 @c ---------------------------------------------------------------------------
24432 @node Input Variables in Inline Assembler
24433 @section Input Variables in Inline Assembler
24436 The example in this section illustrates how to specify the source operands
24437 for assembly language statements.
24438 The program simply increments its input value by 1:
24440 @smallexample @c ada
24442 with Interfaces; use Interfaces;
24443 with Ada.Text_IO; use Ada.Text_IO;
24444 with System.Machine_Code; use System.Machine_Code;
24445 procedure Increment is
24447 function Incr (Value : Unsigned_32) return Unsigned_32 is
24448 Result : Unsigned_32;
24451 Inputs => Unsigned_32'Asm_Input ("a", Value),
24452 Outputs => Unsigned_32'Asm_Output ("=a", Result));
24456 Value : Unsigned_32;
24460 Put_Line ("Value before is" & Value'Img);
24461 Value := Incr (Value);
24462 Put_Line ("Value after is" & Value'Img);
24467 The @code{Outputs} parameter to @code{Asm} specifies
24468 that the result will be in the eax register and that it is to be stored
24469 in the @code{Result} variable.
24471 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
24472 but with an @code{Asm_Input} attribute.
24473 The @code{"="} constraint, indicating an output value, is not present.
24475 You can have multiple input variables, in the same way that you can have more
24476 than one output variable.
24478 The parameter count (%0, %1) etc, now starts at the first input
24479 statement, and continues with the output statements.
24480 When both parameters use the same variable, the
24481 compiler will treat them as the same %n operand, which is the case here.
24483 Just as the @code{Outputs} parameter causes the register to be stored into the
24484 target variable after execution of the assembler statements, so does the
24485 @code{Inputs} parameter cause its variable to be loaded into the register
24486 before execution of the assembler statements.
24488 Thus the effect of the @code{Asm} invocation is:
24490 @item load the 32-bit value of @code{Value} into eax
24491 @item execute the @code{incl %eax} instruction
24492 @item store the contents of eax into the @code{Result} variable
24495 The resulting assembler file (with @option{-O2} optimization) contains:
24498 _increment__incr.1:
24511 @c ---------------------------------------------------------------------------
24512 @node Inlining Inline Assembler Code
24513 @section Inlining Inline Assembler Code
24516 For a short subprogram such as the @code{Incr} function in the previous
24517 section, the overhead of the call and return (creating / deleting the stack
24518 frame) can be significant, compared to the amount of code in the subprogram
24519 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
24520 which directs the compiler to expand invocations of the subprogram at the
24521 point(s) of call, instead of setting up a stack frame for out-of-line calls.
24522 Here is the resulting program:
24524 @smallexample @c ada
24526 with Interfaces; use Interfaces;
24527 with Ada.Text_IO; use Ada.Text_IO;
24528 with System.Machine_Code; use System.Machine_Code;
24529 procedure Increment_2 is
24531 function Incr (Value : Unsigned_32) return Unsigned_32 is
24532 Result : Unsigned_32;
24535 Inputs => Unsigned_32'Asm_Input ("a", Value),
24536 Outputs => Unsigned_32'Asm_Output ("=a", Result));
24539 pragma Inline (Increment);
24541 Value : Unsigned_32;
24545 Put_Line ("Value before is" & Value'Img);
24546 Value := Increment (Value);
24547 Put_Line ("Value after is" & Value'Img);
24552 Compile the program with both optimization (@option{-O2}) and inlining
24553 enabled (@option{-gnatpn} instead of @option{-gnatp}).
24555 The @code{Incr} function is still compiled as usual, but at the
24556 point in @code{Increment} where our function used to be called:
24561 call _increment__incr.1
24566 the code for the function body directly appears:
24579 thus saving the overhead of stack frame setup and an out-of-line call.
24581 @c ---------------------------------------------------------------------------
24582 @node Other Asm Functionality
24583 @section Other @code{Asm} Functionality
24586 This section describes two important parameters to the @code{Asm}
24587 procedure: @code{Clobber}, which identifies register usage;
24588 and @code{Volatile}, which inhibits unwanted optimizations.
24591 * The Clobber Parameter::
24592 * The Volatile Parameter::
24595 @c ---------------------------------------------------------------------------
24596 @node The Clobber Parameter
24597 @subsection The @code{Clobber} Parameter
24600 One of the dangers of intermixing assembly language and a compiled language
24601 such as Ada is that the compiler needs to be aware of which registers are
24602 being used by the assembly code. In some cases, such as the earlier examples,
24603 the constraint string is sufficient to indicate register usage (e.g.,
24605 the eax register). But more generally, the compiler needs an explicit
24606 identification of the registers that are used by the Inline Assembly
24609 Using a register that the compiler doesn't know about
24610 could be a side effect of an instruction (like @code{mull}
24611 storing its result in both eax and edx).
24612 It can also arise from explicit register usage in your
24613 assembly code; for example:
24616 Asm ("movl %0, %%ebx" & LF & HT &
24618 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24619 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
24623 where the compiler (since it does not analyze the @code{Asm} template string)
24624 does not know you are using the ebx register.
24626 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
24627 to identify the registers that will be used by your assembly code:
24631 Asm ("movl %0, %%ebx" & LF & HT &
24633 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24634 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
24639 The Clobber parameter is a static string expression specifying the
24640 register(s) you are using. Note that register names are @emph{not} prefixed
24641 by a percent sign. Also, if more than one register is used then their names
24642 are separated by commas; e.g., @code{"eax, ebx"}
24644 The @code{Clobber} parameter has several additional uses:
24646 @item Use ``register'' name @code{cc} to indicate that flags might have changed
24647 @item Use ``register'' name @code{memory} if you changed a memory location
24650 @c ---------------------------------------------------------------------------
24651 @node The Volatile Parameter
24652 @subsection The @code{Volatile} Parameter
24653 @cindex Volatile parameter
24656 Compiler optimizations in the presence of Inline Assembler may sometimes have
24657 unwanted effects. For example, when an @code{Asm} invocation with an input
24658 variable is inside a loop, the compiler might move the loading of the input
24659 variable outside the loop, regarding it as a one-time initialization.
24661 If this effect is not desired, you can disable such optimizations by setting
24662 the @code{Volatile} parameter to @code{True}; for example:
24664 @smallexample @c ada
24666 Asm ("movl %0, %%ebx" & LF & HT &
24668 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24669 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
24675 By default, @code{Volatile} is set to @code{False} unless there is no
24676 @code{Outputs} parameter.
24678 Although setting @code{Volatile} to @code{True} prevents unwanted
24679 optimizations, it will also disable other optimizations that might be
24680 important for efficiency. In general, you should set @code{Volatile}
24681 to @code{True} only if the compiler's optimizations have created
24684 @c ---------------------------------------------------------------------------
24685 @node A Complete Example
24686 @section A Complete Example
24689 This section contains a complete program illustrating a realistic usage
24690 of GNAT's Inline Assembler capabilities. It comprises a main procedure
24691 @code{Check_CPU} and a package @code{Intel_CPU}.
24692 The package declares a collection of functions that detect the properties
24693 of the 32-bit x86 processor that is running the program.
24694 The main procedure invokes these functions and displays the information.
24696 The Intel_CPU package could be enhanced by adding functions to
24697 detect the type of x386 co-processor, the processor caching options and
24698 special operations such as the SIMD extensions.
24700 Although the Intel_CPU package has been written for 32-bit Intel
24701 compatible CPUs, it is OS neutral. It has been tested on DOS,
24702 Windows/NT and GNU/Linux.
24705 * Check_CPU Procedure::
24706 * Intel_CPU Package Specification::
24707 * Intel_CPU Package Body::
24710 @c ---------------------------------------------------------------------------
24711 @node Check_CPU Procedure
24712 @subsection @code{Check_CPU} Procedure
24713 @cindex Check_CPU procedure
24715 @smallexample @c adanocomment
24716 ---------------------------------------------------------------------
24718 -- Uses the Intel_CPU package to identify the CPU the program is --
24719 -- running on, and some of the features it supports. --
24721 ---------------------------------------------------------------------
24723 with Intel_CPU; -- Intel CPU detection functions
24724 with Ada.Text_IO; -- Standard text I/O
24725 with Ada.Command_Line; -- To set the exit status
24727 procedure Check_CPU is
24729 Type_Found : Boolean := False;
24730 -- Flag to indicate that processor was identified
24732 Features : Intel_CPU.Processor_Features;
24733 -- The processor features
24735 Signature : Intel_CPU.Processor_Signature;
24736 -- The processor type signature
24740 -----------------------------------
24741 -- Display the program banner. --
24742 -----------------------------------
24744 Ada.Text_IO.Put_Line (Ada.Command_Line.Command_Name &
24745 ": check Intel CPU version and features, v1.0");
24746 Ada.Text_IO.Put_Line ("distribute freely, but no warranty whatsoever");
24747 Ada.Text_IO.New_Line;
24749 -----------------------------------------------------------------------
24750 -- We can safely start with the assumption that we are on at least --
24751 -- a x386 processor. If the CPUID instruction is present, then we --
24752 -- have a later processor type. --
24753 -----------------------------------------------------------------------
24755 if Intel_CPU.Has_CPUID = False then
24757 -- No CPUID instruction, so we assume this is indeed a x386
24758 -- processor. We can still check if it has a FP co-processor.
24759 if Intel_CPU.Has_FPU then
24760 Ada.Text_IO.Put_Line
24761 ("x386-type processor with a FP co-processor");
24763 Ada.Text_IO.Put_Line
24764 ("x386-type processor without a FP co-processor");
24765 end if; -- check for FPU
24768 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24771 end if; -- check for CPUID
24773 -----------------------------------------------------------------------
24774 -- If CPUID is supported, check if this is a true Intel processor, --
24775 -- if it is not, display a warning. --
24776 -----------------------------------------------------------------------
24778 if Intel_CPU.Vendor_ID /= Intel_CPU.Intel_Processor then
24779 Ada.Text_IO.Put_Line ("*** This is a Intel compatible processor");
24780 Ada.Text_IO.Put_Line ("*** Some information may be incorrect");
24781 end if; -- check if Intel
24783 ----------------------------------------------------------------------
24784 -- With the CPUID instruction present, we can assume at least a --
24785 -- x486 processor. If the CPUID support level is < 1 then we have --
24786 -- to leave it at that. --
24787 ----------------------------------------------------------------------
24789 if Intel_CPU.CPUID_Level < 1 then
24791 -- Ok, this is a x486 processor. we still can get the Vendor ID
24792 Ada.Text_IO.Put_Line ("x486-type processor");
24793 Ada.Text_IO.Put_Line ("Vendor ID is " & Intel_CPU.Vendor_ID);
24795 -- We can also check if there is a FPU present
24796 if Intel_CPU.Has_FPU then
24797 Ada.Text_IO.Put_Line ("Floating-Point support");
24799 Ada.Text_IO.Put_Line ("No Floating-Point support");
24800 end if; -- check for FPU
24803 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24806 end if; -- check CPUID level
24808 ---------------------------------------------------------------------
24809 -- With a CPUID level of 1 we can use the processor signature to --
24810 -- determine it's exact type. --
24811 ---------------------------------------------------------------------
24813 Signature := Intel_CPU.Signature;
24815 ----------------------------------------------------------------------
24816 -- Ok, now we go into a lot of messy comparisons to get the --
24817 -- processor type. For clarity, no attememt to try to optimize the --
24818 -- comparisons has been made. Note that since Intel_CPU does not --
24819 -- support getting cache info, we cannot distinguish between P5 --
24820 -- and Celeron types yet. --
24821 ----------------------------------------------------------------------
24824 if Signature.Processor_Type = 2#00# and
24825 Signature.Family = 2#0100# and
24826 Signature.Model = 2#0100# then
24827 Type_Found := True;
24828 Ada.Text_IO.Put_Line ("x486SL processor");
24831 -- x486DX2 Write-Back
24832 if Signature.Processor_Type = 2#00# and
24833 Signature.Family = 2#0100# and
24834 Signature.Model = 2#0111# then
24835 Type_Found := True;
24836 Ada.Text_IO.Put_Line ("Write-Back Enhanced x486DX2 processor");
24840 if Signature.Processor_Type = 2#00# and
24841 Signature.Family = 2#0100# and
24842 Signature.Model = 2#1000# then
24843 Type_Found := True;
24844 Ada.Text_IO.Put_Line ("x486DX4 processor");
24847 -- x486DX4 Overdrive
24848 if Signature.Processor_Type = 2#01# and
24849 Signature.Family = 2#0100# and
24850 Signature.Model = 2#1000# then
24851 Type_Found := True;
24852 Ada.Text_IO.Put_Line ("x486DX4 OverDrive processor");
24855 -- Pentium (60, 66)
24856 if Signature.Processor_Type = 2#00# and
24857 Signature.Family = 2#0101# and
24858 Signature.Model = 2#0001# then
24859 Type_Found := True;
24860 Ada.Text_IO.Put_Line ("Pentium processor (60, 66)");
24863 -- Pentium (75, 90, 100, 120, 133, 150, 166, 200)
24864 if Signature.Processor_Type = 2#00# and
24865 Signature.Family = 2#0101# and
24866 Signature.Model = 2#0010# then
24867 Type_Found := True;
24868 Ada.Text_IO.Put_Line
24869 ("Pentium processor (75, 90, 100, 120, 133, 150, 166, 200)");
24872 -- Pentium OverDrive (60, 66)
24873 if Signature.Processor_Type = 2#01# and
24874 Signature.Family = 2#0101# and
24875 Signature.Model = 2#0001# then
24876 Type_Found := True;
24877 Ada.Text_IO.Put_Line ("Pentium OverDrive processor (60, 66)");
24880 -- Pentium OverDrive (75, 90, 100, 120, 133, 150, 166, 200)
24881 if Signature.Processor_Type = 2#01# and
24882 Signature.Family = 2#0101# and
24883 Signature.Model = 2#0010# then
24884 Type_Found := True;
24885 Ada.Text_IO.Put_Line
24886 ("Pentium OverDrive cpu (75, 90, 100, 120, 133, 150, 166, 200)");
24889 -- Pentium OverDrive processor for x486 processor-based systems
24890 if Signature.Processor_Type = 2#01# and
24891 Signature.Family = 2#0101# and
24892 Signature.Model = 2#0011# then
24893 Type_Found := True;
24894 Ada.Text_IO.Put_Line
24895 ("Pentium OverDrive processor for x486 processor-based systems");
24898 -- Pentium processor with MMX technology (166, 200)
24899 if Signature.Processor_Type = 2#00# and
24900 Signature.Family = 2#0101# and
24901 Signature.Model = 2#0100# then
24902 Type_Found := True;
24903 Ada.Text_IO.Put_Line
24904 ("Pentium processor with MMX technology (166, 200)");
24907 -- Pentium OverDrive with MMX for Pentium (75, 90, 100, 120, 133)
24908 if Signature.Processor_Type = 2#01# and
24909 Signature.Family = 2#0101# and
24910 Signature.Model = 2#0100# then
24911 Type_Found := True;
24912 Ada.Text_IO.Put_Line
24913 ("Pentium OverDrive processor with MMX " &
24914 "technology for Pentium processor (75, 90, 100, 120, 133)");
24917 -- Pentium Pro processor
24918 if Signature.Processor_Type = 2#00# and
24919 Signature.Family = 2#0110# and
24920 Signature.Model = 2#0001# then
24921 Type_Found := True;
24922 Ada.Text_IO.Put_Line ("Pentium Pro processor");
24925 -- Pentium II processor, model 3
24926 if Signature.Processor_Type = 2#00# and
24927 Signature.Family = 2#0110# and
24928 Signature.Model = 2#0011# then
24929 Type_Found := True;
24930 Ada.Text_IO.Put_Line ("Pentium II processor, model 3");
24933 -- Pentium II processor, model 5 or Celeron processor
24934 if Signature.Processor_Type = 2#00# and
24935 Signature.Family = 2#0110# and
24936 Signature.Model = 2#0101# then
24937 Type_Found := True;
24938 Ada.Text_IO.Put_Line
24939 ("Pentium II processor, model 5 or Celeron processor");
24942 -- Pentium Pro OverDrive processor
24943 if Signature.Processor_Type = 2#01# and
24944 Signature.Family = 2#0110# and
24945 Signature.Model = 2#0011# then
24946 Type_Found := True;
24947 Ada.Text_IO.Put_Line ("Pentium Pro OverDrive processor");
24950 -- If no type recognized, we have an unknown. Display what
24952 if Type_Found = False then
24953 Ada.Text_IO.Put_Line ("Unknown processor");
24956 -----------------------------------------
24957 -- Display processor stepping level. --
24958 -----------------------------------------
24960 Ada.Text_IO.Put_Line ("Stepping level:" & Signature.Stepping'Img);
24962 ---------------------------------
24963 -- Display vendor ID string. --
24964 ---------------------------------
24966 Ada.Text_IO.Put_Line ("Vendor ID: " & Intel_CPU.Vendor_ID);
24968 ------------------------------------
24969 -- Get the processors features. --
24970 ------------------------------------
24972 Features := Intel_CPU.Features;
24974 -----------------------------
24975 -- Check for a FPU unit. --
24976 -----------------------------
24978 if Features.FPU = True then
24979 Ada.Text_IO.Put_Line ("Floating-Point unit available");
24981 Ada.Text_IO.Put_Line ("no Floating-Point unit");
24982 end if; -- check for FPU
24984 --------------------------------
24985 -- List processor features. --
24986 --------------------------------
24988 Ada.Text_IO.Put_Line ("Supported features: ");
24990 -- Virtual Mode Extension
24991 if Features.VME = True then
24992 Ada.Text_IO.Put_Line (" VME - Virtual Mode Extension");
24995 -- Debugging Extension
24996 if Features.DE = True then
24997 Ada.Text_IO.Put_Line (" DE - Debugging Extension");
25000 -- Page Size Extension
25001 if Features.PSE = True then
25002 Ada.Text_IO.Put_Line (" PSE - Page Size Extension");
25005 -- Time Stamp Counter
25006 if Features.TSC = True then
25007 Ada.Text_IO.Put_Line (" TSC - Time Stamp Counter");
25010 -- Model Specific Registers
25011 if Features.MSR = True then
25012 Ada.Text_IO.Put_Line (" MSR - Model Specific Registers");
25015 -- Physical Address Extension
25016 if Features.PAE = True then
25017 Ada.Text_IO.Put_Line (" PAE - Physical Address Extension");
25020 -- Machine Check Extension
25021 if Features.MCE = True then
25022 Ada.Text_IO.Put_Line (" MCE - Machine Check Extension");
25025 -- CMPXCHG8 instruction supported
25026 if Features.CX8 = True then
25027 Ada.Text_IO.Put_Line (" CX8 - CMPXCHG8 instruction");
25030 -- on-chip APIC hardware support
25031 if Features.APIC = True then
25032 Ada.Text_IO.Put_Line (" APIC - on-chip APIC hardware support");
25035 -- Fast System Call
25036 if Features.SEP = True then
25037 Ada.Text_IO.Put_Line (" SEP - Fast System Call");
25040 -- Memory Type Range Registers
25041 if Features.MTRR = True then
25042 Ada.Text_IO.Put_Line (" MTTR - Memory Type Range Registers");
25045 -- Page Global Enable
25046 if Features.PGE = True then
25047 Ada.Text_IO.Put_Line (" PGE - Page Global Enable");
25050 -- Machine Check Architecture
25051 if Features.MCA = True then
25052 Ada.Text_IO.Put_Line (" MCA - Machine Check Architecture");
25055 -- Conditional Move Instruction Supported
25056 if Features.CMOV = True then
25057 Ada.Text_IO.Put_Line
25058 (" CMOV - Conditional Move Instruction Supported");
25061 -- Page Attribute Table
25062 if Features.PAT = True then
25063 Ada.Text_IO.Put_Line (" PAT - Page Attribute Table");
25066 -- 36-bit Page Size Extension
25067 if Features.PSE_36 = True then
25068 Ada.Text_IO.Put_Line (" PSE_36 - 36-bit Page Size Extension");
25071 -- MMX technology supported
25072 if Features.MMX = True then
25073 Ada.Text_IO.Put_Line (" MMX - MMX technology supported");
25076 -- Fast FP Save and Restore
25077 if Features.FXSR = True then
25078 Ada.Text_IO.Put_Line (" FXSR - Fast FP Save and Restore");
25081 ---------------------
25082 -- Program done. --
25083 ---------------------
25085 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
25090 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Failure);
25096 @c ---------------------------------------------------------------------------
25097 @node Intel_CPU Package Specification
25098 @subsection @code{Intel_CPU} Package Specification
25099 @cindex Intel_CPU package specification
25101 @smallexample @c adanocomment
25102 -------------------------------------------------------------------------
25104 -- file: intel_cpu.ads --
25106 -- ********************************************* --
25107 -- * WARNING: for 32-bit Intel processors only * --
25108 -- ********************************************* --
25110 -- This package contains a number of subprograms that are useful in --
25111 -- determining the Intel x86 CPU (and the features it supports) on --
25112 -- which the program is running. --
25114 -- The package is based upon the information given in the Intel --
25115 -- Application Note AP-485: "Intel Processor Identification and the --
25116 -- CPUID Instruction" as of April 1998. This application note can be --
25117 -- found on www.intel.com. --
25119 -- It currently deals with 32-bit processors only, will not detect --
25120 -- features added after april 1998, and does not guarantee proper --
25121 -- results on Intel-compatible processors. --
25123 -- Cache info and x386 fpu type detection are not supported. --
25125 -- This package does not use any privileged instructions, so should --
25126 -- work on any OS running on a 32-bit Intel processor. --
25128 -------------------------------------------------------------------------
25130 with Interfaces; use Interfaces;
25131 -- for using unsigned types
25133 with System.Machine_Code; use System.Machine_Code;
25134 -- for using inline assembler code
25136 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
25137 -- for inserting control characters
25139 package Intel_CPU is
25141 ----------------------
25142 -- Processor bits --
25143 ----------------------
25145 subtype Num_Bits is Natural range 0 .. 31;
25146 -- the number of processor bits (32)
25148 --------------------------
25149 -- Processor register --
25150 --------------------------
25152 -- define a processor register type for easy access to
25153 -- the individual bits
25155 type Processor_Register is array (Num_Bits) of Boolean;
25156 pragma Pack (Processor_Register);
25157 for Processor_Register'Size use 32;
25159 -------------------------
25160 -- Unsigned register --
25161 -------------------------
25163 -- define a processor register type for easy access to
25164 -- the individual bytes
25166 type Unsigned_Register is
25174 for Unsigned_Register use
25176 L1 at 0 range 0 .. 7;
25177 H1 at 0 range 8 .. 15;
25178 L2 at 0 range 16 .. 23;
25179 H2 at 0 range 24 .. 31;
25182 for Unsigned_Register'Size use 32;
25184 ---------------------------------
25185 -- Intel processor vendor ID --
25186 ---------------------------------
25188 Intel_Processor : constant String (1 .. 12) := "GenuineIntel";
25189 -- indicates an Intel manufactured processor
25191 ------------------------------------
25192 -- Processor signature register --
25193 ------------------------------------
25195 -- a register type to hold the processor signature
25197 type Processor_Signature is
25199 Stepping : Natural range 0 .. 15;
25200 Model : Natural range 0 .. 15;
25201 Family : Natural range 0 .. 15;
25202 Processor_Type : Natural range 0 .. 3;
25203 Reserved : Natural range 0 .. 262143;
25206 for Processor_Signature use
25208 Stepping at 0 range 0 .. 3;
25209 Model at 0 range 4 .. 7;
25210 Family at 0 range 8 .. 11;
25211 Processor_Type at 0 range 12 .. 13;
25212 Reserved at 0 range 14 .. 31;
25215 for Processor_Signature'Size use 32;
25217 -----------------------------------
25218 -- Processor features register --
25219 -----------------------------------
25221 -- a processor register to hold the processor feature flags
25223 type Processor_Features is
25225 FPU : Boolean; -- floating point unit on chip
25226 VME : Boolean; -- virtual mode extension
25227 DE : Boolean; -- debugging extension
25228 PSE : Boolean; -- page size extension
25229 TSC : Boolean; -- time stamp counter
25230 MSR : Boolean; -- model specific registers
25231 PAE : Boolean; -- physical address extension
25232 MCE : Boolean; -- machine check extension
25233 CX8 : Boolean; -- cmpxchg8 instruction
25234 APIC : Boolean; -- on-chip apic hardware
25235 Res_1 : Boolean; -- reserved for extensions
25236 SEP : Boolean; -- fast system call
25237 MTRR : Boolean; -- memory type range registers
25238 PGE : Boolean; -- page global enable
25239 MCA : Boolean; -- machine check architecture
25240 CMOV : Boolean; -- conditional move supported
25241 PAT : Boolean; -- page attribute table
25242 PSE_36 : Boolean; -- 36-bit page size extension
25243 Res_2 : Natural range 0 .. 31; -- reserved for extensions
25244 MMX : Boolean; -- MMX technology supported
25245 FXSR : Boolean; -- fast FP save and restore
25246 Res_3 : Natural range 0 .. 127; -- reserved for extensions
25249 for Processor_Features use
25251 FPU at 0 range 0 .. 0;
25252 VME at 0 range 1 .. 1;
25253 DE at 0 range 2 .. 2;
25254 PSE at 0 range 3 .. 3;
25255 TSC at 0 range 4 .. 4;
25256 MSR at 0 range 5 .. 5;
25257 PAE at 0 range 6 .. 6;
25258 MCE at 0 range 7 .. 7;
25259 CX8 at 0 range 8 .. 8;
25260 APIC at 0 range 9 .. 9;
25261 Res_1 at 0 range 10 .. 10;
25262 SEP at 0 range 11 .. 11;
25263 MTRR at 0 range 12 .. 12;
25264 PGE at 0 range 13 .. 13;
25265 MCA at 0 range 14 .. 14;
25266 CMOV at 0 range 15 .. 15;
25267 PAT at 0 range 16 .. 16;
25268 PSE_36 at 0 range 17 .. 17;
25269 Res_2 at 0 range 18 .. 22;
25270 MMX at 0 range 23 .. 23;
25271 FXSR at 0 range 24 .. 24;
25272 Res_3 at 0 range 25 .. 31;
25275 for Processor_Features'Size use 32;
25277 -------------------
25279 -------------------
25281 function Has_FPU return Boolean;
25282 -- return True if a FPU is found
25283 -- use only if CPUID is not supported
25285 function Has_CPUID return Boolean;
25286 -- return True if the processor supports the CPUID instruction
25288 function CPUID_Level return Natural;
25289 -- return the CPUID support level (0, 1 or 2)
25290 -- can only be called if the CPUID instruction is supported
25292 function Vendor_ID return String;
25293 -- return the processor vendor identification string
25294 -- can only be called if the CPUID instruction is supported
25296 function Signature return Processor_Signature;
25297 -- return the processor signature
25298 -- can only be called if the CPUID instruction is supported
25300 function Features return Processor_Features;
25301 -- return the processors features
25302 -- can only be called if the CPUID instruction is supported
25306 ------------------------
25307 -- EFLAGS bit names --
25308 ------------------------
25310 ID_Flag : constant Num_Bits := 21;
25316 @c ---------------------------------------------------------------------------
25317 @node Intel_CPU Package Body
25318 @subsection @code{Intel_CPU} Package Body
25319 @cindex Intel_CPU package body
25321 @smallexample @c adanocomment
25322 package body Intel_CPU is
25324 ---------------------------
25325 -- Detect FPU presence --
25326 ---------------------------
25328 -- There is a FPU present if we can set values to the FPU Status
25329 -- and Control Words.
25331 function Has_FPU return Boolean is
25333 Register : Unsigned_16;
25334 -- processor register to store a word
25338 -- check if we can change the status word
25341 -- the assembler code
25342 "finit" & LF & HT & -- reset status word
25343 "movw $0x5A5A, %%ax" & LF & HT & -- set value status word
25344 "fnstsw %0" & LF & HT & -- save status word
25345 "movw %%ax, %0", -- store status word
25347 -- output stored in Register
25348 -- register must be a memory location
25349 Outputs => Unsigned_16'Asm_output ("=m", Register),
25351 -- tell compiler that we used eax
25354 -- if the status word is zero, there is no FPU
25355 if Register = 0 then
25356 return False; -- no status word
25357 end if; -- check status word value
25359 -- check if we can get the control word
25362 -- the assembler code
25363 "fnstcw %0", -- save the control word
25365 -- output into Register
25366 -- register must be a memory location
25367 Outputs => Unsigned_16'Asm_output ("=m", Register));
25369 -- check the relevant bits
25370 if (Register and 16#103F#) /= 16#003F# then
25371 return False; -- no control word
25372 end if; -- check control word value
25379 --------------------------------
25380 -- Detect CPUID instruction --
25381 --------------------------------
25383 -- The processor supports the CPUID instruction if it is possible
25384 -- to change the value of ID flag bit in the EFLAGS register.
25386 function Has_CPUID return Boolean is
25388 Original_Flags, Modified_Flags : Processor_Register;
25389 -- EFLAG contents before and after changing the ID flag
25393 -- try flipping the ID flag in the EFLAGS register
25396 -- the assembler code
25397 "pushfl" & LF & HT & -- push EFLAGS on stack
25398 "pop %%eax" & LF & HT & -- pop EFLAGS into eax
25399 "movl %%eax, %0" & LF & HT & -- save EFLAGS content
25400 "xor $0x200000, %%eax" & LF & HT & -- flip ID flag
25401 "push %%eax" & LF & HT & -- push EFLAGS on stack
25402 "popfl" & LF & HT & -- load EFLAGS register
25403 "pushfl" & LF & HT & -- push EFLAGS on stack
25404 "pop %1", -- save EFLAGS content
25406 -- output values, may be anything
25407 -- Original_Flags is %0
25408 -- Modified_Flags is %1
25410 (Processor_Register'Asm_output ("=g", Original_Flags),
25411 Processor_Register'Asm_output ("=g", Modified_Flags)),
25413 -- tell compiler eax is destroyed
25416 -- check if CPUID is supported
25417 if Original_Flags(ID_Flag) /= Modified_Flags(ID_Flag) then
25418 return True; -- ID flag was modified
25420 return False; -- ID flag unchanged
25421 end if; -- check for CPUID
25425 -------------------------------
25426 -- Get CPUID support level --
25427 -------------------------------
25429 function CPUID_Level return Natural is
25431 Level : Unsigned_32;
25432 -- returned support level
25436 -- execute CPUID, storing the results in the Level register
25439 -- the assembler code
25440 "cpuid", -- execute CPUID
25442 -- zero is stored in eax
25443 -- returning the support level in eax
25444 Inputs => Unsigned_32'Asm_input ("a", 0),
25446 -- eax is stored in Level
25447 Outputs => Unsigned_32'Asm_output ("=a", Level),
25449 -- tell compiler ebx, ecx and edx registers are destroyed
25450 Clobber => "ebx, ecx, edx");
25452 -- return the support level
25453 return Natural (Level);
25457 --------------------------------
25458 -- Get CPU Vendor ID String --
25459 --------------------------------
25461 -- The vendor ID string is returned in the ebx, ecx and edx register
25462 -- after executing the CPUID instruction with eax set to zero.
25463 -- In case of a true Intel processor the string returned is
25466 function Vendor_ID return String is
25468 Ebx, Ecx, Edx : Unsigned_Register;
25469 -- registers containing the vendor ID string
25471 Vendor_ID : String (1 .. 12);
25472 -- the vendor ID string
25476 -- execute CPUID, storing the results in the processor registers
25479 -- the assembler code
25480 "cpuid", -- execute CPUID
25482 -- zero stored in eax
25483 -- vendor ID string returned in ebx, ecx and edx
25484 Inputs => Unsigned_32'Asm_input ("a", 0),
25486 -- ebx is stored in Ebx
25487 -- ecx is stored in Ecx
25488 -- edx is stored in Edx
25489 Outputs => (Unsigned_Register'Asm_output ("=b", Ebx),
25490 Unsigned_Register'Asm_output ("=c", Ecx),
25491 Unsigned_Register'Asm_output ("=d", Edx)));
25493 -- now build the vendor ID string
25494 Vendor_ID( 1) := Character'Val (Ebx.L1);
25495 Vendor_ID( 2) := Character'Val (Ebx.H1);
25496 Vendor_ID( 3) := Character'Val (Ebx.L2);
25497 Vendor_ID( 4) := Character'Val (Ebx.H2);
25498 Vendor_ID( 5) := Character'Val (Edx.L1);
25499 Vendor_ID( 6) := Character'Val (Edx.H1);
25500 Vendor_ID( 7) := Character'Val (Edx.L2);
25501 Vendor_ID( 8) := Character'Val (Edx.H2);
25502 Vendor_ID( 9) := Character'Val (Ecx.L1);
25503 Vendor_ID(10) := Character'Val (Ecx.H1);
25504 Vendor_ID(11) := Character'Val (Ecx.L2);
25505 Vendor_ID(12) := Character'Val (Ecx.H2);
25512 -------------------------------
25513 -- Get processor signature --
25514 -------------------------------
25516 function Signature return Processor_Signature is
25518 Result : Processor_Signature;
25519 -- processor signature returned
25523 -- execute CPUID, storing the results in the Result variable
25526 -- the assembler code
25527 "cpuid", -- execute CPUID
25529 -- one is stored in eax
25530 -- processor signature returned in eax
25531 Inputs => Unsigned_32'Asm_input ("a", 1),
25533 -- eax is stored in Result
25534 Outputs => Processor_Signature'Asm_output ("=a", Result),
25536 -- tell compiler that ebx, ecx and edx are also destroyed
25537 Clobber => "ebx, ecx, edx");
25539 -- return processor signature
25544 ------------------------------
25545 -- Get processor features --
25546 ------------------------------
25548 function Features return Processor_Features is
25550 Result : Processor_Features;
25551 -- processor features returned
25555 -- execute CPUID, storing the results in the Result variable
25558 -- the assembler code
25559 "cpuid", -- execute CPUID
25561 -- one stored in eax
25562 -- processor features returned in edx
25563 Inputs => Unsigned_32'Asm_input ("a", 1),
25565 -- edx is stored in Result
25566 Outputs => Processor_Features'Asm_output ("=d", Result),
25568 -- tell compiler that ebx and ecx are also destroyed
25569 Clobber => "ebx, ecx");
25571 -- return processor signature
25578 @c END OF INLINE ASSEMBLER CHAPTER
25579 @c ===============================
25583 @c ***********************************
25584 @c * Compatibility and Porting Guide *
25585 @c ***********************************
25586 @node Compatibility and Porting Guide
25587 @appendix Compatibility and Porting Guide
25590 This chapter describes the compatibility issues that may arise between
25591 GNAT and other Ada 83 and Ada 95 compilation systems, and shows how GNAT
25592 can expedite porting
25593 applications developed in other Ada environments.
25596 * Compatibility with Ada 83::
25597 * Implementation-dependent characteristics::
25598 * Compatibility with DEC Ada 83::
25599 * Compatibility with Other Ada 95 Systems::
25600 * Representation Clauses::
25603 @node Compatibility with Ada 83
25604 @section Compatibility with Ada 83
25605 @cindex Compatibility (between Ada 83 and Ada 95)
25608 Ada 95 is designed to be highly upwards compatible with Ada 83. In
25609 particular, the design intention is that the difficulties associated
25610 with moving from Ada 83 to Ada 95 should be no greater than those
25611 that occur when moving from one Ada 83 system to another.
25613 However, there are a number of points at which there are minor
25614 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
25615 full details of these issues,
25616 and should be consulted for a complete treatment.
25618 following subsections treat the most likely issues to be encountered.
25621 * Legal Ada 83 programs that are illegal in Ada 95::
25622 * More deterministic semantics::
25623 * Changed semantics::
25624 * Other language compatibility issues::
25627 @node Legal Ada 83 programs that are illegal in Ada 95
25628 @subsection Legal Ada 83 programs that are illegal in Ada 95
25631 @item Character literals
25632 Some uses of character literals are ambiguous. Since Ada 95 has introduced
25633 @code{Wide_Character} as a new predefined character type, some uses of
25634 character literals that were legal in Ada 83 are illegal in Ada 95.
25636 @smallexample @c ada
25637 for Char in 'A' .. 'Z' loop ... end loop;
25640 The problem is that @code{'A'} and @code{'Z'} could be from either
25641 @code{Character} or @code{Wide_Character}. The simplest correction
25642 is to make the type explicit; e.g.:
25643 @smallexample @c ada
25644 for Char in Character range 'A' .. 'Z' loop ... end loop;
25647 @item New reserved words
25648 The identifiers @code{abstract}, @code{aliased}, @code{protected},
25649 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
25650 Existing Ada 83 code using any of these identifiers must be edited to
25651 use some alternative name.
25653 @item Freezing rules
25654 The rules in Ada 95 are slightly different with regard to the point at
25655 which entities are frozen, and representation pragmas and clauses are
25656 not permitted past the freeze point. This shows up most typically in
25657 the form of an error message complaining that a representation item
25658 appears too late, and the appropriate corrective action is to move
25659 the item nearer to the declaration of the entity to which it refers.
25661 A particular case is that representation pragmas
25664 extended DEC Ada 83 compatibility pragmas such as @code{Export_Procedure})
25666 cannot be applied to a subprogram body. If necessary, a separate subprogram
25667 declaration must be introduced to which the pragma can be applied.
25669 @item Optional bodies for library packages
25670 In Ada 83, a package that did not require a package body was nevertheless
25671 allowed to have one. This lead to certain surprises in compiling large
25672 systems (situations in which the body could be unexpectedly ignored by the
25673 binder). In Ada 95, if a package does not require a body then it is not
25674 permitted to have a body. To fix this problem, simply remove a redundant
25675 body if it is empty, or, if it is non-empty, introduce a dummy declaration
25676 into the spec that makes the body required. One approach is to add a private
25677 part to the package declaration (if necessary), and define a parameterless
25678 procedure called @code{Requires_Body}, which must then be given a dummy
25679 procedure body in the package body, which then becomes required.
25680 Another approach (assuming that this does not introduce elaboration
25681 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
25682 since one effect of this pragma is to require the presence of a package body.
25684 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
25685 In Ada 95, the exception @code{Numeric_Error} is a renaming of
25686 @code{Constraint_Error}.
25687 This means that it is illegal to have separate exception handlers for
25688 the two exceptions. The fix is simply to remove the handler for the
25689 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
25690 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
25692 @item Indefinite subtypes in generics
25693 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
25694 as the actual for a generic formal private type, but then the instantiation
25695 would be illegal if there were any instances of declarations of variables
25696 of this type in the generic body. In Ada 95, to avoid this clear violation
25697 of the methodological principle known as the ``contract model'',
25698 the generic declaration explicitly indicates whether
25699 or not such instantiations are permitted. If a generic formal parameter
25700 has explicit unknown discriminants, indicated by using @code{(<>)} after the
25701 type name, then it can be instantiated with indefinite types, but no
25702 stand-alone variables can be declared of this type. Any attempt to declare
25703 such a variable will result in an illegality at the time the generic is
25704 declared. If the @code{(<>)} notation is not used, then it is illegal
25705 to instantiate the generic with an indefinite type.
25706 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
25707 It will show up as a compile time error, and
25708 the fix is usually simply to add the @code{(<>)} to the generic declaration.
25711 @node More deterministic semantics
25712 @subsection More deterministic semantics
25716 Conversions from real types to integer types round away from 0. In Ada 83
25717 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
25718 implementation freedom was intended to support unbiased rounding in
25719 statistical applications, but in practice it interfered with portability.
25720 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
25721 is required. Numeric code may be affected by this change in semantics.
25722 Note, though, that this issue is no worse than already existed in Ada 83
25723 when porting code from one vendor to another.
25726 The Real-Time Annex introduces a set of policies that define the behavior of
25727 features that were implementation dependent in Ada 83, such as the order in
25728 which open select branches are executed.
25731 @node Changed semantics
25732 @subsection Changed semantics
25735 The worst kind of incompatibility is one where a program that is legal in
25736 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
25737 possible in Ada 83. Fortunately this is extremely rare, but the one
25738 situation that you should be alert to is the change in the predefined type
25739 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
25742 @item range of @code{Character}
25743 The range of @code{Standard.Character} is now the full 256 characters
25744 of Latin-1, whereas in most Ada 83 implementations it was restricted
25745 to 128 characters. Although some of the effects of
25746 this change will be manifest in compile-time rejection of legal
25747 Ada 83 programs it is possible for a working Ada 83 program to have
25748 a different effect in Ada 95, one that was not permitted in Ada 83.
25749 As an example, the expression
25750 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
25751 delivers @code{255} as its value.
25752 In general, you should look at the logic of any
25753 character-processing Ada 83 program and see whether it needs to be adapted
25754 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
25755 character handling package that may be relevant if code needs to be adapted
25756 to account for the additional Latin-1 elements.
25757 The desirable fix is to
25758 modify the program to accommodate the full character set, but in some cases
25759 it may be convenient to define a subtype or derived type of Character that
25760 covers only the restricted range.
25764 @node Other language compatibility issues
25765 @subsection Other language compatibility issues
25767 @item @option{-gnat83 switch}
25768 All implementations of GNAT provide a switch that causes GNAT to operate
25769 in Ada 83 mode. In this mode, some but not all compatibility problems
25770 of the type described above are handled automatically. For example, the
25771 new Ada 95 reserved words are treated simply as identifiers as in Ada 83.
25773 in practice, it is usually advisable to make the necessary modifications
25774 to the program to remove the need for using this switch.
25775 See @ref{Compiling Ada 83 Programs}.
25777 @item Support for removed Ada 83 pragmas and attributes
25778 A number of pragmas and attributes from Ada 83 have been removed from Ada 95,
25779 generally because they have been replaced by other mechanisms. Ada 95
25780 compilers are allowed, but not required, to implement these missing
25781 elements. In contrast with some other Ada 95 compilers, GNAT implements all
25782 such pragmas and attributes, eliminating this compatibility concern. These
25783 include @code{pragma Interface} and the floating point type attributes
25784 (@code{Emax}, @code{Mantissa}, etc.), among other items.
25788 @node Implementation-dependent characteristics
25789 @section Implementation-dependent characteristics
25791 Although the Ada language defines the semantics of each construct as
25792 precisely as practical, in some situations (for example for reasons of
25793 efficiency, or where the effect is heavily dependent on the host or target
25794 platform) the implementation is allowed some freedom. In porting Ada 83
25795 code to GNAT, you need to be aware of whether / how the existing code
25796 exercised such implementation dependencies. Such characteristics fall into
25797 several categories, and GNAT offers specific support in assisting the
25798 transition from certain Ada 83 compilers.
25801 * Implementation-defined pragmas::
25802 * Implementation-defined attributes::
25804 * Elaboration order::
25805 * Target-specific aspects::
25809 @node Implementation-defined pragmas
25810 @subsection Implementation-defined pragmas
25813 Ada compilers are allowed to supplement the language-defined pragmas, and
25814 these are a potential source of non-portability. All GNAT-defined pragmas
25815 are described in the GNAT Reference Manual, and these include several that
25816 are specifically intended to correspond to other vendors' Ada 83 pragmas.
25817 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
25819 compatibility with DEC Ada 83, GNAT supplies the pragmas
25820 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
25821 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
25822 and @code{Volatile}.
25823 Other relevant pragmas include @code{External} and @code{Link_With}.
25824 Some vendor-specific
25825 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
25827 avoiding compiler rejection of units that contain such pragmas; they are not
25828 relevant in a GNAT context and hence are not otherwise implemented.
25830 @node Implementation-defined attributes
25831 @subsection Implementation-defined attributes
25833 Analogous to pragmas, the set of attributes may be extended by an
25834 implementation. All GNAT-defined attributes are described in the
25835 @cite{GNAT Reference Manual}, and these include several that are specifically
25837 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
25838 the attribute @code{VADS_Size} may be useful. For compatibility with DEC
25839 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
25843 @subsection Libraries
25845 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
25846 code uses vendor-specific libraries then there are several ways to manage
25850 If the source code for the libraries (specifications and bodies) are
25851 available, then the libraries can be migrated in the same way as the
25854 If the source code for the specifications but not the bodies are
25855 available, then you can reimplement the bodies.
25857 Some new Ada 95 features obviate the need for library support. For
25858 example most Ada 83 vendors supplied a package for unsigned integers. The
25859 Ada 95 modular type feature is the preferred way to handle this need, so
25860 instead of migrating or reimplementing the unsigned integer package it may
25861 be preferable to retrofit the application using modular types.
25864 @node Elaboration order
25865 @subsection Elaboration order
25867 The implementation can choose any elaboration order consistent with the unit
25868 dependency relationship. This freedom means that some orders can result in
25869 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
25870 to invoke a subprogram its body has been elaborated, or to instantiate a
25871 generic before the generic body has been elaborated. By default GNAT
25872 attempts to choose a safe order (one that will not encounter access before
25873 elaboration problems) by implicitly inserting Elaborate_All pragmas where
25874 needed. However, this can lead to the creation of elaboration circularities
25875 and a resulting rejection of the program by gnatbind. This issue is
25876 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
25877 In brief, there are several
25878 ways to deal with this situation:
25882 Modify the program to eliminate the circularities, e.g. by moving
25883 elaboration-time code into explicitly-invoked procedures
25885 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
25886 @code{Elaborate} pragmas, and then inhibit the generation of implicit
25887 @code{Elaborate_All}
25888 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
25889 (by selectively suppressing elaboration checks via pragma
25890 @code{Suppress(Elaboration_Check)} when it is safe to do so).
25893 @node Target-specific aspects
25894 @subsection Target-specific aspects
25896 Low-level applications need to deal with machine addresses, data
25897 representations, interfacing with assembler code, and similar issues. If
25898 such an Ada 83 application is being ported to different target hardware (for
25899 example where the byte endianness has changed) then you will need to
25900 carefully examine the program logic; the porting effort will heavily depend
25901 on the robustness of the original design. Moreover, Ada 95 is sometimes
25902 incompatible with typical Ada 83 compiler practices regarding implicit
25903 packing, the meaning of the Size attribute, and the size of access values.
25904 GNAT's approach to these issues is described in @ref{Representation Clauses}.
25907 @node Compatibility with Other Ada 95 Systems
25908 @section Compatibility with Other Ada 95 Systems
25911 Providing that programs avoid the use of implementation dependent and
25912 implementation defined features of Ada 95, as documented in the Ada 95
25913 reference manual, there should be a high degree of portability between
25914 GNAT and other Ada 95 systems. The following are specific items which
25915 have proved troublesome in moving GNAT programs to other Ada 95
25916 compilers, but do not affect porting code to GNAT@.
25919 @item Ada 83 Pragmas and Attributes
25920 Ada 95 compilers are allowed, but not required, to implement the missing
25921 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
25922 GNAT implements all such pragmas and attributes, eliminating this as
25923 a compatibility concern, but some other Ada 95 compilers reject these
25924 pragmas and attributes.
25926 @item Special-needs Annexes
25927 GNAT implements the full set of special needs annexes. At the
25928 current time, it is the only Ada 95 compiler to do so. This means that
25929 programs making use of these features may not be portable to other Ada
25930 95 compilation systems.
25932 @item Representation Clauses
25933 Some other Ada 95 compilers implement only the minimal set of
25934 representation clauses required by the Ada 95 reference manual. GNAT goes
25935 far beyond this minimal set, as described in the next section.
25938 @node Representation Clauses
25939 @section Representation Clauses
25942 The Ada 83 reference manual was quite vague in describing both the minimal
25943 required implementation of representation clauses, and also their precise
25944 effects. The Ada 95 reference manual is much more explicit, but the minimal
25945 set of capabilities required in Ada 95 is quite limited.
25947 GNAT implements the full required set of capabilities described in the
25948 Ada 95 reference manual, but also goes much beyond this, and in particular
25949 an effort has been made to be compatible with existing Ada 83 usage to the
25950 greatest extent possible.
25952 A few cases exist in which Ada 83 compiler behavior is incompatible with
25953 requirements in the Ada 95 reference manual. These are instances of
25954 intentional or accidental dependence on specific implementation dependent
25955 characteristics of these Ada 83 compilers. The following is a list of
25956 the cases most likely to arise in existing legacy Ada 83 code.
25959 @item Implicit Packing
25960 Some Ada 83 compilers allowed a Size specification to cause implicit
25961 packing of an array or record. This could cause expensive implicit
25962 conversions for change of representation in the presence of derived
25963 types, and the Ada design intends to avoid this possibility.
25964 Subsequent AI's were issued to make it clear that such implicit
25965 change of representation in response to a Size clause is inadvisable,
25966 and this recommendation is represented explicitly in the Ada 95 RM
25967 as implementation advice that is followed by GNAT@.
25968 The problem will show up as an error
25969 message rejecting the size clause. The fix is simply to provide
25970 the explicit pragma @code{Pack}, or for more fine tuned control, provide
25971 a Component_Size clause.
25973 @item Meaning of Size Attribute
25974 The Size attribute in Ada 95 for discrete types is defined as being the
25975 minimal number of bits required to hold values of the type. For example,
25976 on a 32-bit machine, the size of Natural will typically be 31 and not
25977 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
25978 some 32 in this situation. This problem will usually show up as a compile
25979 time error, but not always. It is a good idea to check all uses of the
25980 'Size attribute when porting Ada 83 code. The GNAT specific attribute
25981 Object_Size can provide a useful way of duplicating the behavior of
25982 some Ada 83 compiler systems.
25984 @item Size of Access Types
25985 A common assumption in Ada 83 code is that an access type is in fact a pointer,
25986 and that therefore it will be the same size as a System.Address value. This
25987 assumption is true for GNAT in most cases with one exception. For the case of
25988 a pointer to an unconstrained array type (where the bounds may vary from one
25989 value of the access type to another), the default is to use a ``fat pointer'',
25990 which is represented as two separate pointers, one to the bounds, and one to
25991 the array. This representation has a number of advantages, including improved
25992 efficiency. However, it may cause some difficulties in porting existing Ada 83
25993 code which makes the assumption that, for example, pointers fit in 32 bits on
25994 a machine with 32-bit addressing.
25996 To get around this problem, GNAT also permits the use of ``thin pointers'' for
25997 access types in this case (where the designated type is an unconstrained array
25998 type). These thin pointers are indeed the same size as a System.Address value.
25999 To specify a thin pointer, use a size clause for the type, for example:
26001 @smallexample @c ada
26002 type X is access all String;
26003 for X'Size use Standard'Address_Size;
26007 which will cause the type X to be represented using a single pointer.
26008 When using this representation, the bounds are right behind the array.
26009 This representation is slightly less efficient, and does not allow quite
26010 such flexibility in the use of foreign pointers or in using the
26011 Unrestricted_Access attribute to create pointers to non-aliased objects.
26012 But for any standard portable use of the access type it will work in
26013 a functionally correct manner and allow porting of existing code.
26014 Note that another way of forcing a thin pointer representation
26015 is to use a component size clause for the element size in an array,
26016 or a record representation clause for an access field in a record.
26019 @node Compatibility with DEC Ada 83
26020 @section Compatibility with DEC Ada 83
26023 The VMS version of GNAT fully implements all the pragmas and attributes
26024 provided by DEC Ada 83, as well as providing the standard DEC Ada 83
26025 libraries, including Starlet. In addition, data layouts and parameter
26026 passing conventions are highly compatible. This means that porting
26027 existing DEC Ada 83 code to GNAT in VMS systems should be easier than
26028 most other porting efforts. The following are some of the most
26029 significant differences between GNAT and DEC Ada 83.
26032 @item Default floating-point representation
26033 In GNAT, the default floating-point format is IEEE, whereas in DEC Ada 83,
26034 it is VMS format. GNAT does implement the necessary pragmas
26035 (Long_Float, Float_Representation) for changing this default.
26038 The package System in GNAT exactly corresponds to the definition in the
26039 Ada 95 reference manual, which means that it excludes many of the
26040 DEC Ada 83 extensions. However, a separate package Aux_DEC is provided
26041 that contains the additional definitions, and a special pragma,
26042 Extend_System allows this package to be treated transparently as an
26043 extension of package System.
26046 The definitions provided by Aux_DEC are exactly compatible with those
26047 in the DEC Ada 83 version of System, with one exception.
26048 DEC Ada provides the following declarations:
26050 @smallexample @c ada
26051 TO_ADDRESS (INTEGER)
26052 TO_ADDRESS (UNSIGNED_LONGWORD)
26053 TO_ADDRESS (universal_integer)
26057 The version of TO_ADDRESS taking a universal integer argument is in fact
26058 an extension to Ada 83 not strictly compatible with the reference manual.
26059 In GNAT, we are constrained to be exactly compatible with the standard,
26060 and this means we cannot provide this capability. In DEC Ada 83, the
26061 point of this definition is to deal with a call like:
26063 @smallexample @c ada
26064 TO_ADDRESS (16#12777#);
26068 Normally, according to the Ada 83 standard, one would expect this to be
26069 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
26070 of TO_ADDRESS@. However, in DEC Ada 83, there is no ambiguity, since the
26071 definition using universal_integer takes precedence.
26073 In GNAT, since the version with universal_integer cannot be supplied, it is
26074 not possible to be 100% compatible. Since there are many programs using
26075 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
26076 to change the name of the function in the UNSIGNED_LONGWORD case, so the
26077 declarations provided in the GNAT version of AUX_Dec are:
26079 @smallexample @c ada
26080 function To_Address (X : Integer) return Address;
26081 pragma Pure_Function (To_Address);
26083 function To_Address_Long (X : Unsigned_Longword)
26085 pragma Pure_Function (To_Address_Long);
26089 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
26090 change the name to TO_ADDRESS_LONG@.
26092 @item Task_Id values
26093 The Task_Id values assigned will be different in the two systems, and GNAT
26094 does not provide a specified value for the Task_Id of the environment task,
26095 which in GNAT is treated like any other declared task.
26098 For full details on these and other less significant compatibility issues,
26099 see appendix E of the Digital publication entitled @cite{DEC Ada, Technical
26100 Overview and Comparison on DIGITAL Platforms}.
26102 For GNAT running on other than VMS systems, all the DEC Ada 83 pragmas and
26103 attributes are recognized, although only a subset of them can sensibly
26104 be implemented. The description of pragmas in this reference manual
26105 indicates whether or not they are applicable to non-VMS systems.
26110 @node Microsoft Windows Topics
26111 @appendix Microsoft Windows Topics
26117 This chapter describes topics that are specific to the Microsoft Windows
26118 platforms (NT, 2000, and XP Professional).
26121 * Using GNAT on Windows::
26122 * Using a network installation of GNAT::
26123 * CONSOLE and WINDOWS subsystems::
26124 * Temporary Files::
26125 * Mixed-Language Programming on Windows::
26126 * Windows Calling Conventions::
26127 * Introduction to Dynamic Link Libraries (DLLs)::
26128 * Using DLLs with GNAT::
26129 * Building DLLs with GNAT::
26130 * Building DLLs with GNAT Project files::
26131 * Building DLLs with gnatdll::
26132 * GNAT and Windows Resources::
26133 * Debugging a DLL::
26134 * GNAT and COM/DCOM Objects::
26137 @node Using GNAT on Windows
26138 @section Using GNAT on Windows
26141 One of the strengths of the GNAT technology is that its tool set
26142 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
26143 @code{gdb} debugger, etc.) is used in the same way regardless of the
26146 On Windows this tool set is complemented by a number of Microsoft-specific
26147 tools that have been provided to facilitate interoperability with Windows
26148 when this is required. With these tools:
26153 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
26157 You can use any Dynamically Linked Library (DLL) in your Ada code (both
26158 relocatable and non-relocatable DLLs are supported).
26161 You can build Ada DLLs for use in other applications. These applications
26162 can be written in a language other than Ada (e.g., C, C++, etc). Again both
26163 relocatable and non-relocatable Ada DLLs are supported.
26166 You can include Windows resources in your Ada application.
26169 You can use or create COM/DCOM objects.
26173 Immediately below are listed all known general GNAT-for-Windows restrictions.
26174 Other restrictions about specific features like Windows Resources and DLLs
26175 are listed in separate sections below.
26180 It is not possible to use @code{GetLastError} and @code{SetLastError}
26181 when tasking, protected records, or exceptions are used. In these
26182 cases, in order to implement Ada semantics, the GNAT run-time system
26183 calls certain Win32 routines that set the last error variable to 0 upon
26184 success. It should be possible to use @code{GetLastError} and
26185 @code{SetLastError} when tasking, protected record, and exception
26186 features are not used, but it is not guaranteed to work.
26189 It is not possible to link against Microsoft libraries except for
26190 import libraries. The library must be built to be compatible with
26191 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
26192 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
26193 not be compatible with the GNAT runtime. Even if the library is
26194 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
26197 When the compilation environment is located on FAT32 drives, users may
26198 experience recompilations of the source files that have not changed if
26199 Daylight Saving Time (DST) state has changed since the last time files
26200 were compiled. NTFS drives do not have this problem.
26203 No components of the GNAT toolset use any entries in the Windows
26204 registry. The only entries that can be created are file associations and
26205 PATH settings, provided the user has chosen to create them at installation
26206 time, as well as some minimal book-keeping information needed to correctly
26207 uninstall or integrate different GNAT products.
26210 @node Using a network installation of GNAT
26211 @section Using a network installation of GNAT
26214 Make sure the system on which GNAT is installed is accessible from the
26215 current machine, i.e. the install location is shared over the network.
26216 Shared resources are accessed on Windows by means of UNC paths, which
26217 have the format @code{\\server\sharename\path}
26219 In order to use such a network installation, simply add the UNC path of the
26220 @file{bin} directory of your GNAT installation in front of your PATH. For
26221 example, if GNAT is installed in @file{\GNAT} directory of a share location
26222 called @file{c-drive} on a machine @file{LOKI}, the following command will
26225 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
26227 Be aware that every compilation using the network installation results in the
26228 transfer of large amounts of data across the network and will likely cause
26229 serious performance penalty.
26231 @node CONSOLE and WINDOWS subsystems
26232 @section CONSOLE and WINDOWS subsystems
26233 @cindex CONSOLE Subsystem
26234 @cindex WINDOWS Subsystem
26238 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
26239 (which is the default subsystem) will always create a console when
26240 launching the application. This is not something desirable when the
26241 application has a Windows GUI. To get rid of this console the
26242 application must be using the @code{WINDOWS} subsystem. To do so
26243 the @option{-mwindows} linker option must be specified.
26246 $ gnatmake winprog -largs -mwindows
26249 @node Temporary Files
26250 @section Temporary Files
26251 @cindex Temporary files
26254 It is possible to control where temporary files gets created by setting
26255 the TMP environment variable. The file will be created:
26258 @item Under the directory pointed to by the TMP environment variable if
26259 this directory exists.
26261 @item Under c:\temp, if the TMP environment variable is not set (or not
26262 pointing to a directory) and if this directory exists.
26264 @item Under the current working directory otherwise.
26268 This allows you to determine exactly where the temporary
26269 file will be created. This is particularly useful in networked
26270 environments where you may not have write access to some
26273 @node Mixed-Language Programming on Windows
26274 @section Mixed-Language Programming on Windows
26277 Developing pure Ada applications on Windows is no different than on
26278 other GNAT-supported platforms. However, when developing or porting an
26279 application that contains a mix of Ada and C/C++, the choice of your
26280 Windows C/C++ development environment conditions your overall
26281 interoperability strategy.
26283 If you use @code{gcc} to compile the non-Ada part of your application,
26284 there are no Windows-specific restrictions that affect the overall
26285 interoperability with your Ada code. If you plan to use
26286 Microsoft tools (e.g. Microsoft Visual C/C++), you should be aware of
26287 the following limitations:
26291 You cannot link your Ada code with an object or library generated with
26292 Microsoft tools if these use the @code{.tls} section (Thread Local
26293 Storage section) since the GNAT linker does not yet support this section.
26296 You cannot link your Ada code with an object or library generated with
26297 Microsoft tools if these use I/O routines other than those provided in
26298 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
26299 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
26300 libraries can cause a conflict with @code{msvcrt.dll} services. For
26301 instance Visual C++ I/O stream routines conflict with those in
26306 If you do want to use the Microsoft tools for your non-Ada code and hit one
26307 of the above limitations, you have two choices:
26311 Encapsulate your non Ada code in a DLL to be linked with your Ada
26312 application. In this case, use the Microsoft or whatever environment to
26313 build the DLL and use GNAT to build your executable
26314 (@pxref{Using DLLs with GNAT}).
26317 Or you can encapsulate your Ada code in a DLL to be linked with the
26318 other part of your application. In this case, use GNAT to build the DLL
26319 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
26320 environment to build your executable.
26323 @node Windows Calling Conventions
26324 @section Windows Calling Conventions
26329 * C Calling Convention::
26330 * Stdcall Calling Convention::
26331 * DLL Calling Convention::
26335 When a subprogram @code{F} (caller) calls a subprogram @code{G}
26336 (callee), there are several ways to push @code{G}'s parameters on the
26337 stack and there are several possible scenarios to clean up the stack
26338 upon @code{G}'s return. A calling convention is an agreed upon software
26339 protocol whereby the responsibilities between the caller (@code{F}) and
26340 the callee (@code{G}) are clearly defined. Several calling conventions
26341 are available for Windows:
26345 @code{C} (Microsoft defined)
26348 @code{Stdcall} (Microsoft defined)
26351 @code{DLL} (GNAT specific)
26354 @node C Calling Convention
26355 @subsection @code{C} Calling Convention
26358 This is the default calling convention used when interfacing to C/C++
26359 routines compiled with either @code{gcc} or Microsoft Visual C++.
26361 In the @code{C} calling convention subprogram parameters are pushed on the
26362 stack by the caller from right to left. The caller itself is in charge of
26363 cleaning up the stack after the call. In addition, the name of a routine
26364 with @code{C} calling convention is mangled by adding a leading underscore.
26366 The name to use on the Ada side when importing (or exporting) a routine
26367 with @code{C} calling convention is the name of the routine. For
26368 instance the C function:
26371 int get_val (long);
26375 should be imported from Ada as follows:
26377 @smallexample @c ada
26379 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26380 pragma Import (C, Get_Val, External_Name => "get_val");
26385 Note that in this particular case the @code{External_Name} parameter could
26386 have been omitted since, when missing, this parameter is taken to be the
26387 name of the Ada entity in lower case. When the @code{Link_Name} parameter
26388 is missing, as in the above example, this parameter is set to be the
26389 @code{External_Name} with a leading underscore.
26391 When importing a variable defined in C, you should always use the @code{C}
26392 calling convention unless the object containing the variable is part of a
26393 DLL (in which case you should use the @code{DLL} calling convention,
26394 @pxref{DLL Calling Convention}).
26396 @node Stdcall Calling Convention
26397 @subsection @code{Stdcall} Calling Convention
26400 This convention, which was the calling convention used for Pascal
26401 programs, is used by Microsoft for all the routines in the Win32 API for
26402 efficiency reasons. It must be used to import any routine for which this
26403 convention was specified.
26405 In the @code{Stdcall} calling convention subprogram parameters are pushed
26406 on the stack by the caller from right to left. The callee (and not the
26407 caller) is in charge of cleaning the stack on routine exit. In addition,
26408 the name of a routine with @code{Stdcall} calling convention is mangled by
26409 adding a leading underscore (as for the @code{C} calling convention) and a
26410 trailing @code{@@}@code{@i{nn}}, where @i{nn} is the overall size (in
26411 bytes) of the parameters passed to the routine.
26413 The name to use on the Ada side when importing a C routine with a
26414 @code{Stdcall} calling convention is the name of the C routine. The leading
26415 underscore and trailing @code{@@}@code{@i{nn}} are added automatically by
26416 the compiler. For instance the Win32 function:
26419 @b{APIENTRY} int get_val (long);
26423 should be imported from Ada as follows:
26425 @smallexample @c ada
26427 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26428 pragma Import (Stdcall, Get_Val);
26429 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
26434 As for the @code{C} calling convention, when the @code{External_Name}
26435 parameter is missing, it is taken to be the name of the Ada entity in lower
26436 case. If instead of writing the above import pragma you write:
26438 @smallexample @c ada
26440 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26441 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
26446 then the imported routine is @code{_retrieve_val@@4}. However, if instead
26447 of specifying the @code{External_Name} parameter you specify the
26448 @code{Link_Name} as in the following example:
26450 @smallexample @c ada
26452 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26453 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
26458 then the imported routine is @code{retrieve_val@@4}, that is, there is no
26459 trailing underscore but the appropriate @code{@@}@code{@i{nn}} is always
26460 added at the end of the @code{Link_Name} by the compiler.
26463 Note, that in some special cases a DLL's entry point name lacks a trailing
26464 @code{@@}@code{@i{nn}} while the exported name generated for a call has it.
26465 The @code{gnatdll} tool, which creates the import library for the DLL, is able
26466 to handle those cases (see the description of the switches in
26467 @pxref{Using gnatdll} section).
26469 @node DLL Calling Convention
26470 @subsection @code{DLL} Calling Convention
26473 This convention, which is GNAT-specific, must be used when you want to
26474 import in Ada a variables defined in a DLL. For functions and procedures
26475 this convention is equivalent to the @code{Stdcall} convention. As an
26476 example, if a DLL contains a variable defined as:
26483 then, to access this variable from Ada you should write:
26485 @smallexample @c ada
26487 My_Var : Interfaces.C.int;
26488 pragma Import (DLL, My_Var);
26492 The remarks concerning the @code{External_Name} and @code{Link_Name}
26493 parameters given in the previous sections equally apply to the @code{DLL}
26494 calling convention.
26496 @node Introduction to Dynamic Link Libraries (DLLs)
26497 @section Introduction to Dynamic Link Libraries (DLLs)
26501 A Dynamically Linked Library (DLL) is a library that can be shared by
26502 several applications running under Windows. A DLL can contain any number of
26503 routines and variables.
26505 One advantage of DLLs is that you can change and enhance them without
26506 forcing all the applications that depend on them to be relinked or
26507 recompiled. However, you should be aware than all calls to DLL routines are
26508 slower since, as you will understand below, such calls are indirect.
26510 To illustrate the remainder of this section, suppose that an application
26511 wants to use the services of a DLL @file{API.dll}. To use the services
26512 provided by @file{API.dll} you must statically link against the DLL or
26513 an import library which contains a jump table with an entry for each
26514 routine and variable exported by the DLL. In the Microsoft world this
26515 import library is called @file{API.lib}. When using GNAT this import
26516 library is called either @file{libAPI.a} or @file{libapi.a} (names are
26519 After you have linked your application with the DLL or the import library
26520 and you run your application, here is what happens:
26524 Your application is loaded into memory.
26527 The DLL @file{API.dll} is mapped into the address space of your
26528 application. This means that:
26532 The DLL will use the stack of the calling thread.
26535 The DLL will use the virtual address space of the calling process.
26538 The DLL will allocate memory from the virtual address space of the calling
26542 Handles (pointers) can be safely exchanged between routines in the DLL
26543 routines and routines in the application using the DLL.
26547 The entries in the jump table (from the import library @file{libAPI.a}
26548 or @file{API.lib} or automatically created when linking against a DLL)
26549 which is part of your application are initialized with the addresses
26550 of the routines and variables in @file{API.dll}.
26553 If present in @file{API.dll}, routines @code{DllMain} or
26554 @code{DllMainCRTStartup} are invoked. These routines typically contain
26555 the initialization code needed for the well-being of the routines and
26556 variables exported by the DLL.
26560 There is an additional point which is worth mentioning. In the Windows
26561 world there are two kind of DLLs: relocatable and non-relocatable
26562 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
26563 in the target application address space. If the addresses of two
26564 non-relocatable DLLs overlap and these happen to be used by the same
26565 application, a conflict will occur and the application will run
26566 incorrectly. Hence, when possible, it is always preferable to use and
26567 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
26568 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
26569 User's Guide) removes the debugging symbols from the DLL but the DLL can
26570 still be relocated.
26572 As a side note, an interesting difference between Microsoft DLLs and
26573 Unix shared libraries, is the fact that on most Unix systems all public
26574 routines are exported by default in a Unix shared library, while under
26575 Windows it is possible (but not required) to list exported routines in
26576 a definition file (@pxref{The Definition File}).
26578 @node Using DLLs with GNAT
26579 @section Using DLLs with GNAT
26582 * Creating an Ada Spec for the DLL Services::
26583 * Creating an Import Library::
26587 To use the services of a DLL, say @file{API.dll}, in your Ada application
26592 The Ada spec for the routines and/or variables you want to access in
26593 @file{API.dll}. If not available this Ada spec must be built from the C/C++
26594 header files provided with the DLL.
26597 The import library (@file{libAPI.a} or @file{API.lib}). As previously
26598 mentioned an import library is a statically linked library containing the
26599 import table which will be filled at load time to point to the actual
26600 @file{API.dll} routines. Sometimes you don't have an import library for the
26601 DLL you want to use. The following sections will explain how to build
26602 one. Note that this is optional.
26605 The actual DLL, @file{API.dll}.
26609 Once you have all the above, to compile an Ada application that uses the
26610 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
26611 you simply issue the command
26614 $ gnatmake my_ada_app -largs -lAPI
26618 The argument @option{-largs -lAPI} at the end of the @code{gnatmake} command
26619 tells the GNAT linker to look first for a library named @file{API.lib}
26620 (Microsoft-style name) and if not found for a library named @file{libAPI.a}
26621 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
26622 contains the following pragma
26624 @smallexample @c ada
26625 pragma Linker_Options ("-lAPI");
26629 you do not have to add @option{-largs -lAPI} at the end of the @code{gnatmake}
26632 If any one of the items above is missing you will have to create it
26633 yourself. The following sections explain how to do so using as an
26634 example a fictitious DLL called @file{API.dll}.
26636 @node Creating an Ada Spec for the DLL Services
26637 @subsection Creating an Ada Spec for the DLL Services
26640 A DLL typically comes with a C/C++ header file which provides the
26641 definitions of the routines and variables exported by the DLL. The Ada
26642 equivalent of this header file is a package spec that contains definitions
26643 for the imported entities. If the DLL you intend to use does not come with
26644 an Ada spec you have to generate one such spec yourself. For example if
26645 the header file of @file{API.dll} is a file @file{api.h} containing the
26646 following two definitions:
26658 then the equivalent Ada spec could be:
26660 @smallexample @c ada
26663 with Interfaces.C.Strings;
26668 function Get (Str : C.Strings.Chars_Ptr) return C.int;
26671 pragma Import (C, Get);
26672 pragma Import (DLL, Some_Var);
26679 Note that a variable is @strong{always imported with a DLL convention}. A
26680 function can have @code{C}, @code{Stdcall} or @code{DLL} convention. For
26681 subprograms, the @code{DLL} convention is a synonym of @code{Stdcall}
26682 (@pxref{Windows Calling Conventions}).
26684 @node Creating an Import Library
26685 @subsection Creating an Import Library
26686 @cindex Import library
26689 * The Definition File::
26690 * GNAT-Style Import Library::
26691 * Microsoft-Style Import Library::
26695 If a Microsoft-style import library @file{API.lib} or a GNAT-style
26696 import library @file{libAPI.a} is available with @file{API.dll} you
26697 can skip this section. You can also skip this section if
26698 @file{API.dll} is built with GNU tools as in this case it is possible
26699 to link directly against the DLL. Otherwise read on.
26701 @node The Definition File
26702 @subsubsection The Definition File
26703 @cindex Definition file
26707 As previously mentioned, and unlike Unix systems, the list of symbols
26708 that are exported from a DLL must be provided explicitly in Windows.
26709 The main goal of a definition file is precisely that: list the symbols
26710 exported by a DLL. A definition file (usually a file with a @code{.def}
26711 suffix) has the following structure:
26717 [DESCRIPTION @i{string}]
26727 @item LIBRARY @i{name}
26728 This section, which is optional, gives the name of the DLL.
26730 @item DESCRIPTION @i{string}
26731 This section, which is optional, gives a description string that will be
26732 embedded in the import library.
26735 This section gives the list of exported symbols (procedures, functions or
26736 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
26737 section of @file{API.def} looks like:
26751 Note that you must specify the correct suffix (@code{@@}@code{@i{nn}})
26752 (@pxref{Windows Calling Conventions}) for a Stdcall
26753 calling convention function in the exported symbols list.
26756 There can actually be other sections in a definition file, but these
26757 sections are not relevant to the discussion at hand.
26759 @node GNAT-Style Import Library
26760 @subsubsection GNAT-Style Import Library
26763 To create a static import library from @file{API.dll} with the GNAT tools
26764 you should proceed as follows:
26768 Create the definition file @file{API.def} (@pxref{The Definition File}).
26769 For that use the @code{dll2def} tool as follows:
26772 $ dll2def API.dll > API.def
26776 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
26777 to standard output the list of entry points in the DLL. Note that if
26778 some routines in the DLL have the @code{Stdcall} convention
26779 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@i{nn}
26780 suffix then you'll have to edit @file{api.def} to add it, and specify
26781 @code{-k} to @code{gnatdll} when creating the import library.
26784 Here are some hints to find the right @code{@@}@i{nn} suffix.
26788 If you have the Microsoft import library (.lib), it is possible to get
26789 the right symbols by using Microsoft @code{dumpbin} tool (see the
26790 corresponding Microsoft documentation for further details).
26793 $ dumpbin /exports api.lib
26797 If you have a message about a missing symbol at link time the compiler
26798 tells you what symbol is expected. You just have to go back to the
26799 definition file and add the right suffix.
26803 Build the import library @code{libAPI.a}, using @code{gnatdll}
26804 (@pxref{Using gnatdll}) as follows:
26807 $ gnatdll -e API.def -d API.dll
26811 @code{gnatdll} takes as input a definition file @file{API.def} and the
26812 name of the DLL containing the services listed in the definition file
26813 @file{API.dll}. The name of the static import library generated is
26814 computed from the name of the definition file as follows: if the
26815 definition file name is @i{xyz}@code{.def}, the import library name will
26816 be @code{lib}@i{xyz}@code{.a}. Note that in the previous example option
26817 @option{-e} could have been removed because the name of the definition
26818 file (before the ``@code{.def}'' suffix) is the same as the name of the
26819 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
26822 @node Microsoft-Style Import Library
26823 @subsubsection Microsoft-Style Import Library
26826 With GNAT you can either use a GNAT-style or Microsoft-style import
26827 library. A Microsoft import library is needed only if you plan to make an
26828 Ada DLL available to applications developed with Microsoft
26829 tools (@pxref{Mixed-Language Programming on Windows}).
26831 To create a Microsoft-style import library for @file{API.dll} you
26832 should proceed as follows:
26836 Create the definition file @file{API.def} from the DLL. For this use either
26837 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
26838 tool (see the corresponding Microsoft documentation for further details).
26841 Build the actual import library using Microsoft's @code{lib} utility:
26844 $ lib -machine:IX86 -def:API.def -out:API.lib
26848 If you use the above command the definition file @file{API.def} must
26849 contain a line giving the name of the DLL:
26856 See the Microsoft documentation for further details about the usage of
26860 @node Building DLLs with GNAT
26861 @section Building DLLs with GNAT
26862 @cindex DLLs, building
26865 This section explain how to build DLLs using the GNAT built-in DLL
26866 support. With the following procedure it is straight forward to build
26867 and use DLLs with GNAT.
26871 @item building object files
26873 The first step is to build all objects files that are to be included
26874 into the DLL. This is done by using the standard @code{gnatmake} tool.
26876 @item building the DLL
26878 To build the DLL you must use @code{gcc}'s @code{-shared}
26879 option. It is quite simple to use this method:
26882 $ gcc -shared -o api.dll obj1.o obj2.o ...
26885 It is important to note that in this case all symbols found in the
26886 object files are automatically exported. It is possible to restrict
26887 the set of symbols to export by passing to @code{gcc} a definition
26888 file, @pxref{The Definition File}. For example:
26891 $ gcc -shared -o api.dll api.def obj1.o obj2.o ...
26894 If you use a definition file you must export the elaboration procedures
26895 for every package that required one. Elaboration procedures are named
26896 using the package name followed by "_E".
26898 @item preparing DLL to be used
26900 For the DLL to be used by client programs the bodies must be hidden
26901 from it and the .ali set with read-only attribute. This is very important
26902 otherwise GNAT will recompile all packages and will not actually use
26903 the code in the DLL. For example:
26907 $ copy *.ads *.ali api.dll apilib
26908 $ attrib +R apilib\*.ali
26913 At this point it is possible to use the DLL by directly linking
26914 against it. Note that you must use the GNAT shared runtime when using
26915 GNAT shared libraries. This is achieved by using @code{-shared} binder's
26919 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
26922 @node Building DLLs with GNAT Project files
26923 @section Building DLLs with GNAT Project files
26924 @cindex DLLs, building
26927 There is nothing specific to Windows in this area. @pxref{Library Projects}.
26929 @node Building DLLs with gnatdll
26930 @section Building DLLs with gnatdll
26931 @cindex DLLs, building
26934 * Limitations When Using Ada DLLs from Ada::
26935 * Exporting Ada Entities::
26936 * Ada DLLs and Elaboration::
26937 * Ada DLLs and Finalization::
26938 * Creating a Spec for Ada DLLs::
26939 * Creating the Definition File::
26944 Note that it is prefered to use the built-in GNAT DLL support
26945 (@pxref{Building DLLs with GNAT}) or GNAT Project files
26946 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
26948 This section explains how to build DLLs containing Ada code using
26949 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
26950 remainder of this section.
26952 The steps required to build an Ada DLL that is to be used by Ada as well as
26953 non-Ada applications are as follows:
26957 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
26958 @code{Stdcall} calling convention to avoid any Ada name mangling for the
26959 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
26960 skip this step if you plan to use the Ada DLL only from Ada applications.
26963 Your Ada code must export an initialization routine which calls the routine
26964 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
26965 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
26966 routine exported by the Ada DLL must be invoked by the clients of the DLL
26967 to initialize the DLL.
26970 When useful, the DLL should also export a finalization routine which calls
26971 routine @code{adafinal} generated by @code{gnatbind} to perform the
26972 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
26973 The finalization routine exported by the Ada DLL must be invoked by the
26974 clients of the DLL when the DLL services are no further needed.
26977 You must provide a spec for the services exported by the Ada DLL in each
26978 of the programming languages to which you plan to make the DLL available.
26981 You must provide a definition file listing the exported entities
26982 (@pxref{The Definition File}).
26985 Finally you must use @code{gnatdll} to produce the DLL and the import
26986 library (@pxref{Using gnatdll}).
26990 Note that a relocatable DLL stripped using the @code{strip} binutils
26991 tool will not be relocatable anymore. To build a DLL without debug
26992 information pass @code{-largs -s} to @code{gnatdll}.
26994 @node Limitations When Using Ada DLLs from Ada
26995 @subsection Limitations When Using Ada DLLs from Ada
26998 When using Ada DLLs from Ada applications there is a limitation users
26999 should be aware of. Because on Windows the GNAT run time is not in a DLL of
27000 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
27001 each Ada DLL includes the services of the GNAT run time that are necessary
27002 to the Ada code inside the DLL. As a result, when an Ada program uses an
27003 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
27004 one in the main program.
27006 It is therefore not possible to exchange GNAT run-time objects between the
27007 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
27008 handles (e.g. @code{Text_IO.File_Type}), tasks types, protected objects
27011 It is completely safe to exchange plain elementary, array or record types,
27012 Windows object handles, etc.
27014 @node Exporting Ada Entities
27015 @subsection Exporting Ada Entities
27016 @cindex Export table
27019 Building a DLL is a way to encapsulate a set of services usable from any
27020 application. As a result, the Ada entities exported by a DLL should be
27021 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
27022 any Ada name mangling. Please note that the @code{Stdcall} convention
27023 should only be used for subprograms, not for variables. As an example here
27024 is an Ada package @code{API}, spec and body, exporting two procedures, a
27025 function, and a variable:
27027 @smallexample @c ada
27030 with Interfaces.C; use Interfaces;
27032 Count : C.int := 0;
27033 function Factorial (Val : C.int) return C.int;
27035 procedure Initialize_API;
27036 procedure Finalize_API;
27037 -- Initialization & Finalization routines. More in the next section.
27039 pragma Export (C, Initialize_API);
27040 pragma Export (C, Finalize_API);
27041 pragma Export (C, Count);
27042 pragma Export (C, Factorial);
27048 @smallexample @c ada
27051 package body API is
27052 function Factorial (Val : C.int) return C.int is
27055 Count := Count + 1;
27056 for K in 1 .. Val loop
27062 procedure Initialize_API is
27064 pragma Import (C, Adainit);
27067 end Initialize_API;
27069 procedure Finalize_API is
27070 procedure Adafinal;
27071 pragma Import (C, Adafinal);
27081 If the Ada DLL you are building will only be used by Ada applications
27082 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
27083 convention. As an example, the previous package could be written as
27086 @smallexample @c ada
27090 Count : Integer := 0;
27091 function Factorial (Val : Integer) return Integer;
27093 procedure Initialize_API;
27094 procedure Finalize_API;
27095 -- Initialization and Finalization routines.
27101 @smallexample @c ada
27104 package body API is
27105 function Factorial (Val : Integer) return Integer is
27106 Fact : Integer := 1;
27108 Count := Count + 1;
27109 for K in 1 .. Val loop
27116 -- The remainder of this package body is unchanged.
27123 Note that if you do not export the Ada entities with a @code{C} or
27124 @code{Stdcall} convention you will have to provide the mangled Ada names
27125 in the definition file of the Ada DLL
27126 (@pxref{Creating the Definition File}).
27128 @node Ada DLLs and Elaboration
27129 @subsection Ada DLLs and Elaboration
27130 @cindex DLLs and elaboration
27133 The DLL that you are building contains your Ada code as well as all the
27134 routines in the Ada library that are needed by it. The first thing a
27135 user of your DLL must do is elaborate the Ada code
27136 (@pxref{Elaboration Order Handling in GNAT}).
27138 To achieve this you must export an initialization routine
27139 (@code{Initialize_API} in the previous example), which must be invoked
27140 before using any of the DLL services. This elaboration routine must call
27141 the Ada elaboration routine @code{adainit} generated by the GNAT binder
27142 (@pxref{Binding with Non-Ada Main Programs}). See the body of
27143 @code{Initialize_Api} for an example. Note that the GNAT binder is
27144 automatically invoked during the DLL build process by the @code{gnatdll}
27145 tool (@pxref{Using gnatdll}).
27147 When a DLL is loaded, Windows systematically invokes a routine called
27148 @code{DllMain}. It would therefore be possible to call @code{adainit}
27149 directly from @code{DllMain} without having to provide an explicit
27150 initialization routine. Unfortunately, it is not possible to call
27151 @code{adainit} from the @code{DllMain} if your program has library level
27152 tasks because access to the @code{DllMain} entry point is serialized by
27153 the system (that is, only a single thread can execute ``through'' it at a
27154 time), which means that the GNAT run time will deadlock waiting for the
27155 newly created task to complete its initialization.
27157 @node Ada DLLs and Finalization
27158 @subsection Ada DLLs and Finalization
27159 @cindex DLLs and finalization
27162 When the services of an Ada DLL are no longer needed, the client code should
27163 invoke the DLL finalization routine, if available. The DLL finalization
27164 routine is in charge of releasing all resources acquired by the DLL. In the
27165 case of the Ada code contained in the DLL, this is achieved by calling
27166 routine @code{adafinal} generated by the GNAT binder
27167 (@pxref{Binding with Non-Ada Main Programs}).
27168 See the body of @code{Finalize_Api} for an
27169 example. As already pointed out the GNAT binder is automatically invoked
27170 during the DLL build process by the @code{gnatdll} tool
27171 (@pxref{Using gnatdll}).
27173 @node Creating a Spec for Ada DLLs
27174 @subsection Creating a Spec for Ada DLLs
27177 To use the services exported by the Ada DLL from another programming
27178 language (e.g. C), you have to translate the specs of the exported Ada
27179 entities in that language. For instance in the case of @code{API.dll},
27180 the corresponding C header file could look like:
27185 extern int *_imp__count;
27186 #define count (*_imp__count)
27187 int factorial (int);
27193 It is important to understand that when building an Ada DLL to be used by
27194 other Ada applications, you need two different specs for the packages
27195 contained in the DLL: one for building the DLL and the other for using
27196 the DLL. This is because the @code{DLL} calling convention is needed to
27197 use a variable defined in a DLL, but when building the DLL, the variable
27198 must have either the @code{Ada} or @code{C} calling convention. As an
27199 example consider a DLL comprising the following package @code{API}:
27201 @smallexample @c ada
27205 Count : Integer := 0;
27207 -- Remainder of the package omitted.
27214 After producing a DLL containing package @code{API}, the spec that
27215 must be used to import @code{API.Count} from Ada code outside of the
27218 @smallexample @c ada
27223 pragma Import (DLL, Count);
27229 @node Creating the Definition File
27230 @subsection Creating the Definition File
27233 The definition file is the last file needed to build the DLL. It lists
27234 the exported symbols. As an example, the definition file for a DLL
27235 containing only package @code{API} (where all the entities are exported
27236 with a @code{C} calling convention) is:
27251 If the @code{C} calling convention is missing from package @code{API},
27252 then the definition file contains the mangled Ada names of the above
27253 entities, which in this case are:
27262 api__initialize_api
27267 @node Using gnatdll
27268 @subsection Using @code{gnatdll}
27272 * gnatdll Example::
27273 * gnatdll behind the Scenes::
27278 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
27279 and non-Ada sources that make up your DLL have been compiled.
27280 @code{gnatdll} is actually in charge of two distinct tasks: build the
27281 static import library for the DLL and the actual DLL. The form of the
27282 @code{gnatdll} command is
27286 $ gnatdll [@var{switches}] @var{list-of-files} [-largs @var{opts}]
27291 where @i{list-of-files} is a list of ALI and object files. The object
27292 file list must be the exact list of objects corresponding to the non-Ada
27293 sources whose services are to be included in the DLL. The ALI file list
27294 must be the exact list of ALI files for the corresponding Ada sources
27295 whose services are to be included in the DLL. If @i{list-of-files} is
27296 missing, only the static import library is generated.
27299 You may specify any of the following switches to @code{gnatdll}:
27302 @item -a[@var{address}]
27303 @cindex @option{-a} (@code{gnatdll})
27304 Build a non-relocatable DLL at @var{address}. If @var{address} is not
27305 specified the default address @var{0x11000000} will be used. By default,
27306 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
27307 advise the reader to build relocatable DLL.
27309 @item -b @var{address}
27310 @cindex @option{-b} (@code{gnatdll})
27311 Set the relocatable DLL base address. By default the address is
27314 @item -bargs @var{opts}
27315 @cindex @option{-bargs} (@code{gnatdll})
27316 Binder options. Pass @var{opts} to the binder.
27318 @item -d @var{dllfile}
27319 @cindex @option{-d} (@code{gnatdll})
27320 @var{dllfile} is the name of the DLL. This switch must be present for
27321 @code{gnatdll} to do anything. The name of the generated import library is
27322 obtained algorithmically from @var{dllfile} as shown in the following
27323 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
27324 @code{libxyz.a}. The name of the definition file to use (if not specified
27325 by option @option{-e}) is obtained algorithmically from @var{dllfile}
27326 as shown in the following example:
27327 if @var{dllfile} is @code{xyz.dll}, the definition
27328 file used is @code{xyz.def}.
27330 @item -e @var{deffile}
27331 @cindex @option{-e} (@code{gnatdll})
27332 @var{deffile} is the name of the definition file.
27335 @cindex @option{-g} (@code{gnatdll})
27336 Generate debugging information. This information is stored in the object
27337 file and copied from there to the final DLL file by the linker,
27338 where it can be read by the debugger. You must use the
27339 @option{-g} switch if you plan on using the debugger or the symbolic
27343 @cindex @option{-h} (@code{gnatdll})
27344 Help mode. Displays @code{gnatdll} switch usage information.
27347 @cindex @option{-I} (@code{gnatdll})
27348 Direct @code{gnatdll} to search the @var{dir} directory for source and
27349 object files needed to build the DLL.
27350 (@pxref{Search Paths and the Run-Time Library (RTL)}).
27353 @cindex @option{-k} (@code{gnatdll})
27354 Removes the @code{@@}@i{nn} suffix from the import library's exported
27355 names, but keeps them for the link names. You must specify this
27356 option if you want to use a @code{Stdcall} function in a DLL for which
27357 the @code{@@}@i{nn} suffix has been removed. This is the case for most
27358 of the Windows NT DLL for example. This option has no effect when
27359 @option{-n} option is specified.
27361 @item -l @var{file}
27362 @cindex @option{-l} (@code{gnatdll})
27363 The list of ALI and object files used to build the DLL are listed in
27364 @var{file}, instead of being given in the command line. Each line in
27365 @var{file} contains the name of an ALI or object file.
27368 @cindex @option{-n} (@code{gnatdll})
27369 No Import. Do not create the import library.
27372 @cindex @option{-q} (@code{gnatdll})
27373 Quiet mode. Do not display unnecessary messages.
27376 @cindex @option{-v} (@code{gnatdll})
27377 Verbose mode. Display extra information.
27379 @item -largs @var{opts}
27380 @cindex @option{-largs} (@code{gnatdll})
27381 Linker options. Pass @var{opts} to the linker.
27384 @node gnatdll Example
27385 @subsubsection @code{gnatdll} Example
27388 As an example the command to build a relocatable DLL from @file{api.adb}
27389 once @file{api.adb} has been compiled and @file{api.def} created is
27392 $ gnatdll -d api.dll api.ali
27396 The above command creates two files: @file{libapi.a} (the import
27397 library) and @file{api.dll} (the actual DLL). If you want to create
27398 only the DLL, just type:
27401 $ gnatdll -d api.dll -n api.ali
27405 Alternatively if you want to create just the import library, type:
27408 $ gnatdll -d api.dll
27411 @node gnatdll behind the Scenes
27412 @subsubsection @code{gnatdll} behind the Scenes
27415 This section details the steps involved in creating a DLL. @code{gnatdll}
27416 does these steps for you. Unless you are interested in understanding what
27417 goes on behind the scenes, you should skip this section.
27419 We use the previous example of a DLL containing the Ada package @code{API},
27420 to illustrate the steps necessary to build a DLL. The starting point is a
27421 set of objects that will make up the DLL and the corresponding ALI
27422 files. In the case of this example this means that @file{api.o} and
27423 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
27428 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
27429 the information necessary to generate relocation information for the
27435 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
27440 In addition to the base file, the @code{gnatlink} command generates an
27441 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
27442 asks @code{gnatlink} to generate the routines @code{DllMain} and
27443 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
27444 is loaded into memory.
27447 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
27448 export table (@file{api.exp}). The export table contains the relocation
27449 information in a form which can be used during the final link to ensure
27450 that the Windows loader is able to place the DLL anywhere in memory.
27454 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27455 --output-exp api.exp
27460 @code{gnatdll} builds the base file using the new export table. Note that
27461 @code{gnatbind} must be called once again since the binder generated file
27462 has been deleted during the previous call to @code{gnatlink}.
27467 $ gnatlink api -o api.jnk api.exp -mdll
27468 -Wl,--base-file,api.base
27473 @code{gnatdll} builds the new export table using the new base file and
27474 generates the DLL import library @file{libAPI.a}.
27478 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27479 --output-exp api.exp --output-lib libAPI.a
27484 Finally @code{gnatdll} builds the relocatable DLL using the final export
27490 $ gnatlink api api.exp -o api.dll -mdll
27495 @node Using dlltool
27496 @subsubsection Using @code{dlltool}
27499 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
27500 DLLs and static import libraries. This section summarizes the most
27501 common @code{dlltool} switches. The form of the @code{dlltool} command
27505 $ dlltool [@var{switches}]
27509 @code{dlltool} switches include:
27512 @item --base-file @var{basefile}
27513 @cindex @option{--base-file} (@command{dlltool})
27514 Read the base file @var{basefile} generated by the linker. This switch
27515 is used to create a relocatable DLL.
27517 @item --def @var{deffile}
27518 @cindex @option{--def} (@command{dlltool})
27519 Read the definition file.
27521 @item --dllname @var{name}
27522 @cindex @option{--dllname} (@command{dlltool})
27523 Gives the name of the DLL. This switch is used to embed the name of the
27524 DLL in the static import library generated by @code{dlltool} with switch
27525 @option{--output-lib}.
27528 @cindex @option{-k} (@command{dlltool})
27529 Kill @code{@@}@i{nn} from exported names
27530 (@pxref{Windows Calling Conventions}
27531 for a discussion about @code{Stdcall}-style symbols.
27534 @cindex @option{--help} (@command{dlltool})
27535 Prints the @code{dlltool} switches with a concise description.
27537 @item --output-exp @var{exportfile}
27538 @cindex @option{--output-exp} (@command{dlltool})
27539 Generate an export file @var{exportfile}. The export file contains the
27540 export table (list of symbols in the DLL) and is used to create the DLL.
27542 @item --output-lib @i{libfile}
27543 @cindex @option{--output-lib} (@command{dlltool})
27544 Generate a static import library @var{libfile}.
27547 @cindex @option{-v} (@command{dlltool})
27550 @item --as @i{assembler-name}
27551 @cindex @option{--as} (@command{dlltool})
27552 Use @i{assembler-name} as the assembler. The default is @code{as}.
27555 @node GNAT and Windows Resources
27556 @section GNAT and Windows Resources
27557 @cindex Resources, windows
27560 * Building Resources::
27561 * Compiling Resources::
27562 * Using Resources::
27566 Resources are an easy way to add Windows specific objects to your
27567 application. The objects that can be added as resources include:
27596 This section explains how to build, compile and use resources.
27598 @node Building Resources
27599 @subsection Building Resources
27600 @cindex Resources, building
27603 A resource file is an ASCII file. By convention resource files have an
27604 @file{.rc} extension.
27605 The easiest way to build a resource file is to use Microsoft tools
27606 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
27607 @code{dlgedit.exe} to build dialogs.
27608 It is always possible to build an @file{.rc} file yourself by writing a
27611 It is not our objective to explain how to write a resource file. A
27612 complete description of the resource script language can be found in the
27613 Microsoft documentation.
27615 @node Compiling Resources
27616 @subsection Compiling Resources
27619 @cindex Resources, compiling
27622 This section describes how to build a GNAT-compatible (COFF) object file
27623 containing the resources. This is done using the Resource Compiler
27624 @code{windres} as follows:
27627 $ windres -i myres.rc -o myres.o
27631 By default @code{windres} will run @code{gcc} to preprocess the @file{.rc}
27632 file. You can specify an alternate preprocessor (usually named
27633 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
27634 parameter. A list of all possible options may be obtained by entering
27635 the command @code{windres} @option{--help}.
27637 It is also possible to use the Microsoft resource compiler @code{rc.exe}
27638 to produce a @file{.res} file (binary resource file). See the
27639 corresponding Microsoft documentation for further details. In this case
27640 you need to use @code{windres} to translate the @file{.res} file to a
27641 GNAT-compatible object file as follows:
27644 $ windres -i myres.res -o myres.o
27647 @node Using Resources
27648 @subsection Using Resources
27649 @cindex Resources, using
27652 To include the resource file in your program just add the
27653 GNAT-compatible object file for the resource(s) to the linker
27654 arguments. With @code{gnatmake} this is done by using the @option{-largs}
27658 $ gnatmake myprog -largs myres.o
27661 @node Debugging a DLL
27662 @section Debugging a DLL
27663 @cindex DLL debugging
27666 * Program and DLL Both Built with GCC/GNAT::
27667 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
27671 Debugging a DLL is similar to debugging a standard program. But
27672 we have to deal with two different executable parts: the DLL and the
27673 program that uses it. We have the following four possibilities:
27677 The program and the DLL are built with @code{GCC/GNAT}.
27679 The program is built with foreign tools and the DLL is built with
27682 The program is built with @code{GCC/GNAT} and the DLL is built with
27688 In this section we address only cases one and two above.
27689 There is no point in trying to debug
27690 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
27691 information in it. To do so you must use a debugger compatible with the
27692 tools suite used to build the DLL.
27694 @node Program and DLL Both Built with GCC/GNAT
27695 @subsection Program and DLL Both Built with GCC/GNAT
27698 This is the simplest case. Both the DLL and the program have @code{GDB}
27699 compatible debugging information. It is then possible to break anywhere in
27700 the process. Let's suppose here that the main procedure is named
27701 @code{ada_main} and that in the DLL there is an entry point named
27705 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
27706 program must have been built with the debugging information (see GNAT -g
27707 switch). Here are the step-by-step instructions for debugging it:
27710 @item Launch @code{GDB} on the main program.
27716 @item Break on the main procedure and run the program.
27719 (gdb) break ada_main
27724 This step is required to be able to set a breakpoint inside the DLL. As long
27725 as the program is not run, the DLL is not loaded. This has the
27726 consequence that the DLL debugging information is also not loaded, so it is not
27727 possible to set a breakpoint in the DLL.
27729 @item Set a breakpoint inside the DLL
27732 (gdb) break ada_dll
27739 At this stage a breakpoint is set inside the DLL. From there on
27740 you can use the standard approach to debug the whole program
27741 (@pxref{Running and Debugging Ada Programs}).
27743 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
27744 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
27747 * Debugging the DLL Directly::
27748 * Attaching to a Running Process::
27752 In this case things are slightly more complex because it is not possible to
27753 start the main program and then break at the beginning to load the DLL and the
27754 associated DLL debugging information. It is not possible to break at the
27755 beginning of the program because there is no @code{GDB} debugging information,
27756 and therefore there is no direct way of getting initial control. This
27757 section addresses this issue by describing some methods that can be used
27758 to break somewhere in the DLL to debug it.
27761 First suppose that the main procedure is named @code{main} (this is for
27762 example some C code built with Microsoft Visual C) and that there is a
27763 DLL named @code{test.dll} containing an Ada entry point named
27767 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
27768 been built with debugging information (see GNAT -g option).
27770 @node Debugging the DLL Directly
27771 @subsubsection Debugging the DLL Directly
27775 Launch the debugger on the DLL.
27781 @item Set a breakpoint on a DLL subroutine.
27784 (gdb) break ada_dll
27788 Specify the executable file to @code{GDB}.
27791 (gdb) exec-file main.exe
27802 This will run the program until it reaches the breakpoint that has been
27803 set. From that point you can use the standard way to debug a program
27804 as described in (@pxref{Running and Debugging Ada Programs}).
27809 It is also possible to debug the DLL by attaching to a running process.
27811 @node Attaching to a Running Process
27812 @subsubsection Attaching to a Running Process
27813 @cindex DLL debugging, attach to process
27816 With @code{GDB} it is always possible to debug a running process by
27817 attaching to it. It is possible to debug a DLL this way. The limitation
27818 of this approach is that the DLL must run long enough to perform the
27819 attach operation. It may be useful for instance to insert a time wasting
27820 loop in the code of the DLL to meet this criterion.
27824 @item Launch the main program @file{main.exe}.
27830 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
27831 that the process PID for @file{main.exe} is 208.
27839 @item Attach to the running process to be debugged.
27845 @item Load the process debugging information.
27848 (gdb) symbol-file main.exe
27851 @item Break somewhere in the DLL.
27854 (gdb) break ada_dll
27857 @item Continue process execution.
27866 This last step will resume the process execution, and stop at
27867 the breakpoint we have set. From there you can use the standard
27868 approach to debug a program as described in
27869 (@pxref{Running and Debugging Ada Programs}).
27871 @node GNAT and COM/DCOM Objects
27872 @section GNAT and COM/DCOM Objects
27877 This section is temporarily left blank.
27882 @c **********************************
27883 @c * GNU Free Documentation License *
27884 @c **********************************
27886 @c GNU Free Documentation License
27888 @node Index,,GNU Free Documentation License, Top
27894 @c Put table of contents at end, otherwise it precedes the "title page" in
27895 @c the .txt version
27896 @c Edit the pdf file to move the contents to the beginning, after the title