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8 @settitle GNAT User's Guide for Native Platforms
13 @dircategory GNU Ada Tools
15 * gnat_ugn: (gnat_ugn.info). gnat_ugn
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24 GNAT User's Guide for Native Platforms , Sep 14, 2019
28 Copyright @copyright{} 2008-2019, Free Software Foundation
34 @title GNAT User's Guide for Native Platforms
39 @c %** start of user preamble
41 @c %** end of user preamble
45 @top GNAT User's Guide for Native Platforms
50 @anchor{gnat_ugn doc}@anchor{0}
51 @emph{GNAT, The GNU Ada Development Environment}
54 @include gcc-common.texi
55 GCC version @value{version-GCC}@*
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.3 or
60 any later version published by the Free Software Foundation; with no
61 Invariant Sections, with the Front-Cover Texts being
62 "GNAT User's Guide for Native Platforms",
63 and with no Back-Cover Texts. A copy of the license is
64 included in the section entitled @ref{1,,GNU Free Documentation License}.
68 * Getting Started with GNAT::
69 * The GNAT Compilation Model::
70 * Building Executable Programs with GNAT::
71 * GNAT Utility Programs::
72 * GNAT and Program Execution::
73 * Platform-Specific Information::
74 * Example of Binder Output File::
75 * Elaboration Order Handling in GNAT::
77 * GNU Free Documentation License::
81 --- The Detailed Node Listing ---
85 * What This Guide Contains::
86 * What You Should Know before Reading This Guide::
87 * Related Information::
88 * A Note to Readers of Previous Versions of the Manual::
91 Getting Started with GNAT
94 * Running a Simple Ada Program::
95 * Running a Program with Multiple Units::
96 * Using the gnatmake Utility::
98 The GNAT Compilation Model
100 * Source Representation::
101 * Foreign Language Representation::
102 * File Naming Topics and Utilities::
103 * Configuration Pragmas::
104 * Generating Object Files::
105 * Source Dependencies::
106 * The Ada Library Information Files::
107 * Binding an Ada Program::
108 * GNAT and Libraries::
109 * Conditional Compilation::
110 * Mixed Language Programming::
111 * GNAT and Other Compilation Models::
112 * Using GNAT Files with External Tools::
114 Foreign Language Representation
117 * Other 8-Bit Codes::
118 * Wide_Character Encodings::
119 * Wide_Wide_Character Encodings::
121 File Naming Topics and Utilities
123 * File Naming Rules::
124 * Using Other File Names::
125 * Alternative File Naming Schemes::
126 * Handling Arbitrary File Naming Conventions with gnatname::
127 * File Name Krunching with gnatkr::
128 * Renaming Files with gnatchop::
130 Handling Arbitrary File Naming Conventions with gnatname
132 * Arbitrary File Naming Conventions::
134 * Switches for gnatname::
135 * Examples of gnatname Usage::
137 File Name Krunching with gnatkr
142 * Examples of gnatkr Usage::
144 Renaming Files with gnatchop
146 * Handling Files with Multiple Units::
147 * Operating gnatchop in Compilation Mode::
148 * Command Line for gnatchop::
149 * Switches for gnatchop::
150 * Examples of gnatchop Usage::
152 Configuration Pragmas
154 * Handling of Configuration Pragmas::
155 * The Configuration Pragmas Files::
159 * Introduction to Libraries in GNAT::
160 * General Ada Libraries::
161 * Stand-alone Ada Libraries::
162 * Rebuilding the GNAT Run-Time Library::
164 General Ada Libraries
166 * Building a library::
167 * Installing a library::
170 Stand-alone Ada Libraries
172 * Introduction to Stand-alone Libraries::
173 * Building a Stand-alone Library::
174 * Creating a Stand-alone Library to be used in a non-Ada context::
175 * Restrictions in Stand-alone Libraries::
177 Conditional Compilation
179 * Modeling Conditional Compilation in Ada::
180 * Preprocessing with gnatprep::
181 * Integrated Preprocessing::
183 Modeling Conditional Compilation in Ada
185 * Use of Boolean Constants::
186 * Debugging - A Special Case::
187 * Conditionalizing Declarations::
188 * Use of Alternative Implementations::
191 Preprocessing with gnatprep
193 * Preprocessing Symbols::
195 * Switches for gnatprep::
196 * Form of Definitions File::
197 * Form of Input Text for gnatprep::
199 Mixed Language Programming
202 * Calling Conventions::
203 * Building Mixed Ada and C++ Programs::
204 * Generating Ada Bindings for C and C++ headers::
205 * Generating C Headers for Ada Specifications::
207 Building Mixed Ada and C++ Programs
209 * Interfacing to C++::
210 * Linking a Mixed C++ & Ada Program::
212 * Interfacing with C++ constructors::
213 * Interfacing with C++ at the Class Level::
215 Generating Ada Bindings for C and C++ headers
217 * Running the Binding Generator::
218 * Generating Bindings for C++ Headers::
221 Generating C Headers for Ada Specifications
223 * Running the C Header Generator::
225 GNAT and Other Compilation Models
227 * Comparison between GNAT and C/C++ Compilation Models::
228 * Comparison between GNAT and Conventional Ada Library Models::
230 Using GNAT Files with External Tools
232 * Using Other Utility Programs with GNAT::
233 * The External Symbol Naming Scheme of GNAT::
235 Building Executable Programs with GNAT
237 * Building with gnatmake::
238 * Compiling with gcc::
239 * Compiler Switches::
241 * Binding with gnatbind::
242 * Linking with gnatlink::
243 * Using the GNU make Utility::
245 Building with gnatmake
248 * Switches for gnatmake::
249 * Mode Switches for gnatmake::
250 * Notes on the Command Line::
251 * How gnatmake Works::
252 * Examples of gnatmake Usage::
256 * Compiling Programs::
257 * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
258 * Order of Compilation Issues::
263 * Alphabetical List of All Switches::
264 * Output and Error Message Control::
265 * Warning Message Control::
266 * Debugging and Assertion Control::
267 * Validity Checking::
270 * Using gcc for Syntax Checking::
271 * Using gcc for Semantic Checking::
272 * Compiling Different Versions of Ada::
273 * Character Set Control::
274 * File Naming Control::
275 * Subprogram Inlining Control::
276 * Auxiliary Output Control::
277 * Debugging Control::
278 * Exception Handling Control::
279 * Units to Sources Mapping Files::
280 * Code Generation Control::
282 Binding with gnatbind
285 * Switches for gnatbind::
286 * Command-Line Access::
287 * Search Paths for gnatbind::
288 * Examples of gnatbind Usage::
290 Switches for gnatbind
292 * Consistency-Checking Modes::
293 * Binder Error Message Control::
294 * Elaboration Control::
296 * Dynamic Allocation Control::
297 * Binding with Non-Ada Main Programs::
298 * Binding Programs with No Main Subprogram::
300 Linking with gnatlink
303 * Switches for gnatlink::
305 Using the GNU make Utility
307 * Using gnatmake in a Makefile::
308 * Automatically Creating a List of Directories::
309 * Generating the Command Line Switches::
310 * Overcoming Command Line Length Limits::
312 GNAT Utility Programs
314 * The File Cleanup Utility gnatclean::
315 * The GNAT Library Browser gnatls::
316 * The Cross-Referencing Tools gnatxref and gnatfind::
317 * The Ada to HTML Converter gnathtml::
319 The File Cleanup Utility gnatclean
321 * Running gnatclean::
322 * Switches for gnatclean::
324 The GNAT Library Browser gnatls
327 * Switches for gnatls::
328 * Example of gnatls Usage::
330 The Cross-Referencing Tools gnatxref and gnatfind
332 * gnatxref Switches::
333 * gnatfind Switches::
334 * Configuration Files for gnatxref and gnatfind::
335 * Regular Expressions in gnatfind and gnatxref::
336 * Examples of gnatxref Usage::
337 * Examples of gnatfind Usage::
339 Examples of gnatxref Usage
342 * Using gnatxref with vi::
344 The Ada to HTML Converter gnathtml
346 * Invoking gnathtml::
347 * Installing gnathtml::
349 GNAT and Program Execution
351 * Running and Debugging Ada Programs::
353 * Improving Performance::
354 * Overflow Check Handling in GNAT::
355 * Performing Dimensionality Analysis in GNAT::
356 * Stack Related Facilities::
357 * Memory Management Issues::
359 Running and Debugging Ada Programs
361 * The GNAT Debugger GDB::
363 * Introduction to GDB Commands::
364 * Using Ada Expressions::
365 * Calling User-Defined Subprograms::
366 * Using the next Command in a Function::
367 * Stopping When Ada Exceptions Are Raised::
369 * Debugging Generic Units::
370 * Remote Debugging with gdbserver::
371 * GNAT Abnormal Termination or Failure to Terminate::
372 * Naming Conventions for GNAT Source Files::
373 * Getting Internal Debugging Information::
375 * Pretty-Printers for the GNAT runtime::
379 * Non-Symbolic Traceback::
380 * Symbolic Traceback::
384 * Profiling an Ada Program with gprof::
386 Profiling an Ada Program with gprof
388 * Compilation for profiling::
389 * Program execution::
391 * Interpretation of profiling results::
393 Improving Performance
395 * Performance Considerations::
396 * Text_IO Suggestions::
397 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
399 Performance Considerations
401 * Controlling Run-Time Checks::
402 * Use of Restrictions::
403 * Optimization Levels::
404 * Debugging Optimized Code::
405 * Inlining of Subprograms::
406 * Floating_Point_Operations::
407 * Vectorization of loops::
408 * Other Optimization Switches::
409 * Optimization and Strict Aliasing::
410 * Aliased Variables and Optimization::
411 * Atomic Variables and Optimization::
412 * Passive Task Optimization::
414 Reducing Size of Executables with Unused Subprogram/Data Elimination
416 * About unused subprogram/data elimination::
417 * Compilation options::
418 * Example of unused subprogram/data elimination::
420 Overflow Check Handling in GNAT
423 * Management of Overflows in GNAT::
424 * Specifying the Desired Mode::
426 * Implementation Notes::
428 Stack Related Facilities
430 * Stack Overflow Checking::
431 * Static Stack Usage Analysis::
432 * Dynamic Stack Usage Analysis::
434 Memory Management Issues
436 * Some Useful Memory Pools::
437 * The GNAT Debug Pool Facility::
439 Platform-Specific Information
441 * Run-Time Libraries::
442 * Specifying a Run-Time Library::
444 * Microsoft Windows Topics::
449 * Summary of Run-Time Configurations::
451 Specifying a Run-Time Library
453 * Choosing the Scheduling Policy::
457 * Required Packages on GNU/Linux::
459 Microsoft Windows Topics
461 * Using GNAT on Windows::
462 * Using a network installation of GNAT::
463 * CONSOLE and WINDOWS subsystems::
465 * Disabling Command Line Argument Expansion::
466 * Windows Socket Timeouts::
467 * Mixed-Language Programming on Windows::
468 * Windows Specific Add-Ons::
470 Mixed-Language Programming on Windows
472 * Windows Calling Conventions::
473 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
474 * Using DLLs with GNAT::
475 * Building DLLs with GNAT Project files::
476 * Building DLLs with GNAT::
477 * Building DLLs with gnatdll::
478 * Ada DLLs and Finalization::
479 * Creating a Spec for Ada DLLs::
480 * GNAT and Windows Resources::
481 * Using GNAT DLLs from Microsoft Visual Studio Applications::
483 * Setting Stack Size from gnatlink::
484 * Setting Heap Size from gnatlink::
486 Windows Calling Conventions
488 * C Calling Convention::
489 * Stdcall Calling Convention::
490 * Win32 Calling Convention::
491 * DLL Calling Convention::
495 * Creating an Ada Spec for the DLL Services::
496 * Creating an Import Library::
498 Building DLLs with gnatdll
500 * Limitations When Using Ada DLLs from Ada::
501 * Exporting Ada Entities::
502 * Ada DLLs and Elaboration::
504 Creating a Spec for Ada DLLs
506 * Creating the Definition File::
509 GNAT and Windows Resources
511 * Building Resources::
512 * Compiling Resources::
517 * Program and DLL Both Built with GCC/GNAT::
518 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
520 Windows Specific Add-Ons
527 * Codesigning the Debugger::
529 Elaboration Order Handling in GNAT
532 * Elaboration Order::
533 * Checking the Elaboration Order::
534 * Controlling the Elaboration Order in Ada::
535 * Controlling the Elaboration Order in GNAT::
536 * Mixing Elaboration Models::
538 * SPARK Diagnostics::
539 * Elaboration Circularities::
540 * Resolving Elaboration Circularities::
541 * Elaboration-related Compiler Switches::
542 * Summary of Procedures for Elaboration Control::
543 * Inspecting the Chosen Elaboration Order::
547 * Basic Assembler Syntax::
548 * A Simple Example of Inline Assembler::
549 * Output Variables in Inline Assembler::
550 * Input Variables in Inline Assembler::
551 * Inlining Inline Assembler Code::
552 * Other Asm Functionality::
554 Other Asm Functionality
556 * The Clobber Parameter::
557 * The Volatile Parameter::
562 @node About This Guide,Getting Started with GNAT,Top,Top
563 @anchor{gnat_ugn/about_this_guide about-this-guide}@anchor{2}@anchor{gnat_ugn/about_this_guide doc}@anchor{3}@anchor{gnat_ugn/about_this_guide gnat-user-s-guide-for-native-platforms}@anchor{4}@anchor{gnat_ugn/about_this_guide id1}@anchor{5}
564 @chapter About This Guide
568 This guide describes the use of GNAT,
569 a compiler and software development
570 toolset for the full Ada programming language.
571 It documents the features of the compiler and tools, and explains
572 how to use them to build Ada applications.
574 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
575 invoked in Ada 83 compatibility mode.
576 By default, GNAT assumes Ada 2012, but you can override with a
577 compiler switch (@ref{6,,Compiling Different Versions of Ada})
578 to explicitly specify the language version.
579 Throughout this manual, references to 'Ada' without a year suffix
580 apply to all Ada 95/2005/2012 versions of the language.
583 * What This Guide Contains::
584 * What You Should Know before Reading This Guide::
585 * Related Information::
586 * A Note to Readers of Previous Versions of the Manual::
591 @node What This Guide Contains,What You Should Know before Reading This Guide,,About This Guide
592 @anchor{gnat_ugn/about_this_guide what-this-guide-contains}@anchor{7}
593 @section What This Guide Contains
596 This guide contains the following chapters:
602 @ref{8,,Getting Started with GNAT} describes how to get started compiling
603 and running Ada programs with the GNAT Ada programming environment.
606 @ref{9,,The GNAT Compilation Model} describes the compilation model used
610 @ref{a,,Building Executable Programs with GNAT} describes how to use the
611 main GNAT tools to build executable programs, and it also gives examples of
612 using the GNU make utility with GNAT.
615 @ref{b,,GNAT Utility Programs} explains the various utility programs that
616 are included in the GNAT environment
619 @ref{c,,GNAT and Program Execution} covers a number of topics related to
620 running, debugging, and tuning the performace of programs developed
624 Appendices cover several additional topics:
630 @ref{d,,Platform-Specific Information} describes the different run-time
631 library implementations and also presents information on how to use
632 GNAT on several specific platforms
635 @ref{e,,Example of Binder Output File} shows the source code for the binder
636 output file for a sample program.
639 @ref{f,,Elaboration Order Handling in GNAT} describes how GNAT helps
640 you deal with elaboration order issues.
643 @ref{10,,Inline Assembler} shows how to use the inline assembly facility
647 @node What You Should Know before Reading This Guide,Related Information,What This Guide Contains,About This Guide
648 @anchor{gnat_ugn/about_this_guide what-you-should-know-before-reading-this-guide}@anchor{11}
649 @section What You Should Know before Reading This Guide
652 @geindex Ada 95 Language Reference Manual
654 @geindex Ada 2005 Language Reference Manual
656 This guide assumes a basic familiarity with the Ada 95 language, as
657 described in the International Standard ANSI/ISO/IEC-8652:1995, January
659 It does not require knowledge of the features introduced by Ada 2005
661 Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in
662 the GNAT documentation package.
664 @node Related Information,A Note to Readers of Previous Versions of the Manual,What You Should Know before Reading This Guide,About This Guide
665 @anchor{gnat_ugn/about_this_guide related-information}@anchor{12}
666 @section Related Information
669 For further information about Ada and related tools, please refer to the
676 @cite{Ada 95 Reference Manual}, @cite{Ada 2005 Reference Manual}, and
677 @cite{Ada 2012 Reference Manual}, which contain reference
678 material for the several revisions of the Ada language standard.
681 @cite{GNAT Reference_Manual}, which contains all reference material for the GNAT
682 implementation of Ada.
685 @cite{Using the GNAT Programming Studio}, which describes the GPS
686 Integrated Development Environment.
689 @cite{GNAT Programming Studio Tutorial}, which introduces the
690 main GPS features through examples.
693 @cite{Debugging with GDB},
694 for all details on the use of the GNU source-level debugger.
697 @cite{GNU Emacs Manual},
698 for full information on the extensible editor and programming
702 @node A Note to Readers of Previous Versions of the Manual,Conventions,Related Information,About This Guide
703 @anchor{gnat_ugn/about_this_guide a-note-to-readers-of-previous-versions-of-the-manual}@anchor{13}
704 @section A Note to Readers of Previous Versions of the Manual
707 In early 2015 the GNAT manuals were transitioned to the
708 reStructuredText (rst) / Sphinx documentation generator technology.
709 During that process the @cite{GNAT User's Guide} was reorganized
710 so that related topics would be described together in the same chapter
711 or appendix. Here's a summary of the major changes realized in
712 the new document structure.
718 @ref{9,,The GNAT Compilation Model} has been extended so that it now covers
719 the following material:
725 The @code{gnatname}, @code{gnatkr}, and @code{gnatchop} tools
728 @ref{14,,Configuration Pragmas}
731 @ref{15,,GNAT and Libraries}
734 @ref{16,,Conditional Compilation} including @ref{17,,Preprocessing with gnatprep}
735 and @ref{18,,Integrated Preprocessing}
738 @ref{19,,Generating Ada Bindings for C and C++ headers}
741 @ref{1a,,Using GNAT Files with External Tools}
745 @ref{a,,Building Executable Programs with GNAT} is a new chapter consolidating
746 the following content:
752 @ref{1b,,Building with gnatmake}
755 @ref{1c,,Compiling with gcc}
758 @ref{1d,,Binding with gnatbind}
761 @ref{1e,,Linking with gnatlink}
764 @ref{1f,,Using the GNU make Utility}
768 @ref{b,,GNAT Utility Programs} is a new chapter consolidating the information about several
776 @ref{20,,The File Cleanup Utility gnatclean}
779 @ref{21,,The GNAT Library Browser gnatls}
782 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
785 @ref{23,,The Ada to HTML Converter gnathtml}
789 @ref{c,,GNAT and Program Execution} is a new chapter consolidating the following:
795 @ref{24,,Running and Debugging Ada Programs}
801 @ref{26,,Improving Performance}
804 @ref{27,,Overflow Check Handling in GNAT}
807 @ref{28,,Performing Dimensionality Analysis in GNAT}
810 @ref{29,,Stack Related Facilities}
813 @ref{2a,,Memory Management Issues}
817 @ref{d,,Platform-Specific Information} is a new appendix consolidating the following:
823 @ref{2b,,Run-Time Libraries}
826 @ref{2c,,Microsoft Windows Topics}
829 @ref{2d,,Mac OS Topics}
833 The @emph{Compatibility and Porting Guide} appendix has been moved to the
834 @cite{GNAT Reference Manual}. It now includes a section
835 @emph{Writing Portable Fixed-Point Declarations} which was previously
836 a separate chapter in the @cite{GNAT User's Guide}.
839 @node Conventions,,A Note to Readers of Previous Versions of the Manual,About This Guide
840 @anchor{gnat_ugn/about_this_guide conventions}@anchor{2e}
845 @geindex typographical
847 @geindex Typographical conventions
849 Following are examples of the typographical and graphic conventions used
856 @code{Functions}, @code{utility program names}, @code{standard names},
872 [optional information or parameters]
875 Examples are described by text
878 and then shown this way.
882 Commands that are entered by the user are shown as preceded by a prompt string
883 comprising the @code{$} character followed by a space.
886 Full file names are shown with the '/' character
887 as the directory separator; e.g., @code{parent-dir/subdir/myfile.adb}.
888 If you are using GNAT on a Windows platform, please note that
889 the '\' character should be used instead.
892 @node Getting Started with GNAT,The GNAT Compilation Model,About This Guide,Top
893 @anchor{gnat_ugn/getting_started_with_gnat getting-started-with-gnat}@anchor{8}@anchor{gnat_ugn/getting_started_with_gnat doc}@anchor{2f}@anchor{gnat_ugn/getting_started_with_gnat id1}@anchor{30}
894 @chapter Getting Started with GNAT
897 This chapter describes how to use GNAT's command line interface to build
898 executable Ada programs.
899 On most platforms a visually oriented Integrated Development Environment
900 is also available, the GNAT Programming Studio (GPS).
901 GPS offers a graphical "look and feel", support for development in
902 other programming languages, comprehensive browsing features, and
903 many other capabilities.
904 For information on GPS please refer to
905 @cite{Using the GNAT Programming Studio}.
909 * Running a Simple Ada Program::
910 * Running a Program with Multiple Units::
911 * Using the gnatmake Utility::
915 @node Running GNAT,Running a Simple Ada Program,,Getting Started with GNAT
916 @anchor{gnat_ugn/getting_started_with_gnat running-gnat}@anchor{31}@anchor{gnat_ugn/getting_started_with_gnat id2}@anchor{32}
917 @section Running GNAT
920 Three steps are needed to create an executable file from an Ada source
927 The source file(s) must be compiled.
930 The file(s) must be bound using the GNAT binder.
933 All appropriate object files must be linked to produce an executable.
936 All three steps are most commonly handled by using the @code{gnatmake}
937 utility program that, given the name of the main program, automatically
938 performs the necessary compilation, binding and linking steps.
940 @node Running a Simple Ada Program,Running a Program with Multiple Units,Running GNAT,Getting Started with GNAT
941 @anchor{gnat_ugn/getting_started_with_gnat running-a-simple-ada-program}@anchor{33}@anchor{gnat_ugn/getting_started_with_gnat id3}@anchor{34}
942 @section Running a Simple Ada Program
945 Any text editor may be used to prepare an Ada program.
946 (If Emacs is used, the optional Ada mode may be helpful in laying out the
948 The program text is a normal text file. We will assume in our initial
949 example that you have used your editor to prepare the following
950 standard format text file:
953 with Ada.Text_IO; use Ada.Text_IO;
956 Put_Line ("Hello WORLD!");
960 This file should be named @code{hello.adb}.
961 With the normal default file naming conventions, GNAT requires
963 contain a single compilation unit whose file name is the
965 with periods replaced by hyphens; the
966 extension is @code{ads} for a
967 spec and @code{adb} for a body.
968 You can override this default file naming convention by use of the
969 special pragma @code{Source_File_Name} (for further information please
970 see @ref{35,,Using Other File Names}).
971 Alternatively, if you want to rename your files according to this default
972 convention, which is probably more convenient if you will be using GNAT
973 for all your compilations, then the @code{gnatchop} utility
974 can be used to generate correctly-named source files
975 (see @ref{36,,Renaming Files with gnatchop}).
977 You can compile the program using the following command (@code{$} is used
978 as the command prompt in the examples in this document):
984 @code{gcc} is the command used to run the compiler. This compiler is
985 capable of compiling programs in several languages, including Ada and
986 C. It assumes that you have given it an Ada program if the file extension is
987 either @code{.ads} or @code{.adb}, and it will then call
988 the GNAT compiler to compile the specified file.
990 The @code{-c} switch is required. It tells @code{gcc} to only do a
991 compilation. (For C programs, @code{gcc} can also do linking, but this
992 capability is not used directly for Ada programs, so the @code{-c}
993 switch must always be present.)
995 This compile command generates a file
996 @code{hello.o}, which is the object
997 file corresponding to your Ada program. It also generates
998 an 'Ada Library Information' file @code{hello.ali},
999 which contains additional information used to check
1000 that an Ada program is consistent.
1001 To build an executable file,
1002 use @code{gnatbind} to bind the program
1003 and @code{gnatlink} to link it. The
1004 argument to both @code{gnatbind} and @code{gnatlink} is the name of the
1005 @code{ALI} file, but the default extension of @code{.ali} can
1006 be omitted. This means that in the most common case, the argument
1007 is simply the name of the main program:
1014 A simpler method of carrying out these steps is to use @code{gnatmake},
1015 a master program that invokes all the required
1016 compilation, binding and linking tools in the correct order. In particular,
1017 @code{gnatmake} automatically recompiles any sources that have been
1018 modified since they were last compiled, or sources that depend
1019 on such modified sources, so that 'version skew' is avoided.
1021 @geindex Version skew (avoided by `@w{`}gnatmake`@w{`})
1024 $ gnatmake hello.adb
1027 The result is an executable program called @code{hello}, which can be
1034 assuming that the current directory is on the search path
1035 for executable programs.
1037 and, if all has gone well, you will see:
1043 appear in response to this command.
1045 @node Running a Program with Multiple Units,Using the gnatmake Utility,Running a Simple Ada Program,Getting Started with GNAT
1046 @anchor{gnat_ugn/getting_started_with_gnat id4}@anchor{37}@anchor{gnat_ugn/getting_started_with_gnat running-a-program-with-multiple-units}@anchor{38}
1047 @section Running a Program with Multiple Units
1050 Consider a slightly more complicated example that has three files: a
1051 main program, and the spec and body of a package:
1054 package Greetings is
1059 with Ada.Text_IO; use Ada.Text_IO;
1060 package body Greetings is
1063 Put_Line ("Hello WORLD!");
1066 procedure Goodbye is
1068 Put_Line ("Goodbye WORLD!");
1080 Following the one-unit-per-file rule, place this program in the
1081 following three separate files:
1086 @item @emph{greetings.ads}
1088 spec of package @code{Greetings}
1090 @item @emph{greetings.adb}
1092 body of package @code{Greetings}
1094 @item @emph{gmain.adb}
1096 body of main program
1099 To build an executable version of
1100 this program, we could use four separate steps to compile, bind, and link
1101 the program, as follows:
1105 $ gcc -c greetings.adb
1110 Note that there is no required order of compilation when using GNAT.
1111 In particular it is perfectly fine to compile the main program first.
1112 Also, it is not necessary to compile package specs in the case where
1113 there is an accompanying body; you only need to compile the body. If you want
1114 to submit these files to the compiler for semantic checking and not code
1115 generation, then use the @code{-gnatc} switch:
1118 $ gcc -c greetings.ads -gnatc
1121 Although the compilation can be done in separate steps as in the
1122 above example, in practice it is almost always more convenient
1123 to use the @code{gnatmake} tool. All you need to know in this case
1124 is the name of the main program's source file. The effect of the above four
1125 commands can be achieved with a single one:
1128 $ gnatmake gmain.adb
1131 In the next section we discuss the advantages of using @code{gnatmake} in
1134 @node Using the gnatmake Utility,,Running a Program with Multiple Units,Getting Started with GNAT
1135 @anchor{gnat_ugn/getting_started_with_gnat using-the-gnatmake-utility}@anchor{39}@anchor{gnat_ugn/getting_started_with_gnat id5}@anchor{3a}
1136 @section Using the @code{gnatmake} Utility
1139 If you work on a program by compiling single components at a time using
1140 @code{gcc}, you typically keep track of the units you modify. In order to
1141 build a consistent system, you compile not only these units, but also any
1142 units that depend on the units you have modified.
1143 For example, in the preceding case,
1144 if you edit @code{gmain.adb}, you only need to recompile that file. But if
1145 you edit @code{greetings.ads}, you must recompile both
1146 @code{greetings.adb} and @code{gmain.adb}, because both files contain
1147 units that depend on @code{greetings.ads}.
1149 @code{gnatbind} will warn you if you forget one of these compilation
1150 steps, so that it is impossible to generate an inconsistent program as a
1151 result of forgetting to do a compilation. Nevertheless it is tedious and
1152 error-prone to keep track of dependencies among units.
1153 One approach to handle the dependency-bookkeeping is to use a
1154 makefile. However, makefiles present maintenance problems of their own:
1155 if the dependencies change as you change the program, you must make
1156 sure that the makefile is kept up-to-date manually, which is also an
1157 error-prone process.
1159 The @code{gnatmake} utility takes care of these details automatically.
1160 Invoke it using either one of the following forms:
1163 $ gnatmake gmain.adb
1167 The argument is the name of the file containing the main program;
1168 you may omit the extension. @code{gnatmake}
1169 examines the environment, automatically recompiles any files that need
1170 recompiling, and binds and links the resulting set of object files,
1171 generating the executable file, @code{gmain}.
1172 In a large program, it
1173 can be extremely helpful to use @code{gnatmake}, because working out by hand
1174 what needs to be recompiled can be difficult.
1176 Note that @code{gnatmake} takes into account all the Ada rules that
1177 establish dependencies among units. These include dependencies that result
1178 from inlining subprogram bodies, and from
1179 generic instantiation. Unlike some other
1180 Ada make tools, @code{gnatmake} does not rely on the dependencies that were
1181 found by the compiler on a previous compilation, which may possibly
1182 be wrong when sources change. @code{gnatmake} determines the exact set of
1183 dependencies from scratch each time it is run.
1185 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
1187 @node The GNAT Compilation Model,Building Executable Programs with GNAT,Getting Started with GNAT,Top
1188 @anchor{gnat_ugn/the_gnat_compilation_model doc}@anchor{3b}@anchor{gnat_ugn/the_gnat_compilation_model the-gnat-compilation-model}@anchor{9}@anchor{gnat_ugn/the_gnat_compilation_model id1}@anchor{3c}
1189 @chapter The GNAT Compilation Model
1192 @geindex GNAT compilation model
1194 @geindex Compilation model
1196 This chapter describes the compilation model used by GNAT. Although
1197 similar to that used by other languages such as C and C++, this model
1198 is substantially different from the traditional Ada compilation models,
1199 which are based on a centralized program library. The chapter covers
1200 the following material:
1206 Topics related to source file makeup and naming
1212 @ref{3d,,Source Representation}
1215 @ref{3e,,Foreign Language Representation}
1218 @ref{3f,,File Naming Topics and Utilities}
1222 @ref{14,,Configuration Pragmas}
1225 @ref{40,,Generating Object Files}
1228 @ref{41,,Source Dependencies}
1231 @ref{42,,The Ada Library Information Files}
1234 @ref{43,,Binding an Ada Program}
1237 @ref{15,,GNAT and Libraries}
1240 @ref{16,,Conditional Compilation}
1243 @ref{44,,Mixed Language Programming}
1246 @ref{45,,GNAT and Other Compilation Models}
1249 @ref{1a,,Using GNAT Files with External Tools}
1253 * Source Representation::
1254 * Foreign Language Representation::
1255 * File Naming Topics and Utilities::
1256 * Configuration Pragmas::
1257 * Generating Object Files::
1258 * Source Dependencies::
1259 * The Ada Library Information Files::
1260 * Binding an Ada Program::
1261 * GNAT and Libraries::
1262 * Conditional Compilation::
1263 * Mixed Language Programming::
1264 * GNAT and Other Compilation Models::
1265 * Using GNAT Files with External Tools::
1269 @node Source Representation,Foreign Language Representation,,The GNAT Compilation Model
1270 @anchor{gnat_ugn/the_gnat_compilation_model source-representation}@anchor{3d}@anchor{gnat_ugn/the_gnat_compilation_model id2}@anchor{46}
1271 @section Source Representation
1282 Ada source programs are represented in standard text files, using
1283 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1284 7-bit ASCII set, plus additional characters used for
1285 representing foreign languages (see @ref{3e,,Foreign Language Representation}
1286 for support of non-USA character sets). The format effector characters
1287 are represented using their standard ASCII encodings, as follows:
1292 @multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
1369 Source files are in standard text file format. In addition, GNAT will
1370 recognize a wide variety of stream formats, in which the end of
1371 physical lines is marked by any of the following sequences:
1372 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1373 in accommodating files that are imported from other operating systems.
1375 @geindex End of source file; Source file@comma{} end
1377 @geindex SUB (control character)
1379 The end of a source file is normally represented by the physical end of
1380 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1381 recognized as signalling the end of the source file. Again, this is
1382 provided for compatibility with other operating systems where this
1383 code is used to represent the end of file.
1385 @geindex spec (definition)
1386 @geindex compilation (definition)
1388 Each file contains a single Ada compilation unit, including any pragmas
1389 associated with the unit. For example, this means you must place a
1390 package declaration (a package @emph{spec}) and the corresponding body in
1391 separate files. An Ada @emph{compilation} (which is a sequence of
1392 compilation units) is represented using a sequence of files. Similarly,
1393 you will place each subunit or child unit in a separate file.
1395 @node Foreign Language Representation,File Naming Topics and Utilities,Source Representation,The GNAT Compilation Model
1396 @anchor{gnat_ugn/the_gnat_compilation_model foreign-language-representation}@anchor{3e}@anchor{gnat_ugn/the_gnat_compilation_model id3}@anchor{47}
1397 @section Foreign Language Representation
1400 GNAT supports the standard character sets defined in Ada as well as
1401 several other non-standard character sets for use in localized versions
1402 of the compiler (@ref{48,,Character Set Control}).
1406 * Other 8-Bit Codes::
1407 * Wide_Character Encodings::
1408 * Wide_Wide_Character Encodings::
1412 @node Latin-1,Other 8-Bit Codes,,Foreign Language Representation
1413 @anchor{gnat_ugn/the_gnat_compilation_model id4}@anchor{49}@anchor{gnat_ugn/the_gnat_compilation_model latin-1}@anchor{4a}
1419 The basic character set is Latin-1. This character set is defined by ISO
1420 standard 8859, part 1. The lower half (character codes @code{16#00#}
1421 ... @code{16#7F#)} is identical to standard ASCII coding, but the upper
1422 half is used to represent additional characters. These include extended letters
1423 used by European languages, such as French accents, the vowels with umlauts
1424 used in German, and the extra letter A-ring used in Swedish.
1426 @geindex Ada.Characters.Latin_1
1428 For a complete list of Latin-1 codes and their encodings, see the source
1429 file of library unit @code{Ada.Characters.Latin_1} in file
1430 @code{a-chlat1.ads}.
1431 You may use any of these extended characters freely in character or
1432 string literals. In addition, the extended characters that represent
1433 letters can be used in identifiers.
1435 @node Other 8-Bit Codes,Wide_Character Encodings,Latin-1,Foreign Language Representation
1436 @anchor{gnat_ugn/the_gnat_compilation_model other-8-bit-codes}@anchor{4b}@anchor{gnat_ugn/the_gnat_compilation_model id5}@anchor{4c}
1437 @subsection Other 8-Bit Codes
1440 GNAT also supports several other 8-bit coding schemes:
1449 @item @emph{ISO 8859-2 (Latin-2)}
1451 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1462 @item @emph{ISO 8859-3 (Latin-3)}
1464 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1475 @item @emph{ISO 8859-4 (Latin-4)}
1477 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1488 @item @emph{ISO 8859-5 (Cyrillic)}
1490 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1491 lowercase equivalence.
1494 @geindex ISO 8859-15
1501 @item @emph{ISO 8859-15 (Latin-9)}
1503 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1504 lowercase equivalence
1507 @geindex code page 437 (IBM PC)
1512 @item @emph{IBM PC (code page 437)}
1514 This code page is the normal default for PCs in the U.S. It corresponds
1515 to the original IBM PC character set. This set has some, but not all, of
1516 the extended Latin-1 letters, but these letters do not have the same
1517 encoding as Latin-1. In this mode, these letters are allowed in
1518 identifiers with uppercase and lowercase equivalence.
1521 @geindex code page 850 (IBM PC)
1526 @item @emph{IBM PC (code page 850)}
1528 This code page is a modification of 437 extended to include all the
1529 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1530 mode, all these letters are allowed in identifiers with uppercase and
1531 lowercase equivalence.
1533 @item @emph{Full Upper 8-bit}
1535 Any character in the range 80-FF allowed in identifiers, and all are
1536 considered distinct. In other words, there are no uppercase and lowercase
1537 equivalences in this range. This is useful in conjunction with
1538 certain encoding schemes used for some foreign character sets (e.g.,
1539 the typical method of representing Chinese characters on the PC).
1541 @item @emph{No Upper-Half}
1543 No upper-half characters in the range 80-FF are allowed in identifiers.
1544 This gives Ada 83 compatibility for identifier names.
1547 For precise data on the encodings permitted, and the uppercase and lowercase
1548 equivalences that are recognized, see the file @code{csets.adb} in
1549 the GNAT compiler sources. You will need to obtain a full source release
1550 of GNAT to obtain this file.
1552 @node Wide_Character Encodings,Wide_Wide_Character Encodings,Other 8-Bit Codes,Foreign Language Representation
1553 @anchor{gnat_ugn/the_gnat_compilation_model id6}@anchor{4d}@anchor{gnat_ugn/the_gnat_compilation_model wide-character-encodings}@anchor{4e}
1554 @subsection Wide_Character Encodings
1557 GNAT allows wide character codes to appear in character and string
1558 literals, and also optionally in identifiers, by means of the following
1559 possible encoding schemes:
1564 @item @emph{Hex Coding}
1566 In this encoding, a wide character is represented by the following five
1573 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1574 characters (using uppercase letters) of the wide character code. For
1575 example, ESC A345 is used to represent the wide character with code
1577 This scheme is compatible with use of the full Wide_Character set.
1579 @item @emph{Upper-Half Coding}
1581 @geindex Upper-Half Coding
1583 The wide character with encoding @code{16#abcd#} where the upper bit is on
1584 (in other words, 'a' is in the range 8-F) is represented as two bytes,
1585 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1586 character, but is not required to be in the upper half. This method can
1587 be also used for shift-JIS or EUC, where the internal coding matches the
1590 @item @emph{Shift JIS Coding}
1592 @geindex Shift JIS Coding
1594 A wide character is represented by a two-character sequence,
1596 @code{16#cd#}, with the restrictions described for upper-half encoding as
1597 described above. The internal character code is the corresponding JIS
1598 character according to the standard algorithm for Shift-JIS
1599 conversion. Only characters defined in the JIS code set table can be
1600 used with this encoding method.
1602 @item @emph{EUC Coding}
1606 A wide character is represented by a two-character sequence
1608 @code{16#cd#}, with both characters being in the upper half. The internal
1609 character code is the corresponding JIS character according to the EUC
1610 encoding algorithm. Only characters defined in the JIS code set table
1611 can be used with this encoding method.
1613 @item @emph{UTF-8 Coding}
1615 A wide character is represented using
1616 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1617 10646-1/Am.2. Depending on the character value, the representation
1618 is a one, two, or three byte sequence:
1621 16#0000#-16#007f#: 2#0xxxxxxx#
1622 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
1623 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
1626 where the @code{xxx} bits correspond to the left-padded bits of the
1627 16-bit character value. Note that all lower half ASCII characters
1628 are represented as ASCII bytes and all upper half characters and
1629 other wide characters are represented as sequences of upper-half
1630 (The full UTF-8 scheme allows for encoding 31-bit characters as
1631 6-byte sequences, and in the following section on wide wide
1632 characters, the use of these sequences is documented).
1634 @item @emph{Brackets Coding}
1636 In this encoding, a wide character is represented by the following eight
1643 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1644 characters (using uppercase letters) of the wide character code. For
1645 example, ['A345'] is used to represent the wide character with code
1646 @code{16#A345#}. It is also possible (though not required) to use the
1647 Brackets coding for upper half characters. For example, the code
1648 @code{16#A3#} can be represented as @code{['A3']}.
1650 This scheme is compatible with use of the full Wide_Character set,
1651 and is also the method used for wide character encoding in some standard
1652 ACATS (Ada Conformity Assessment Test Suite) test suite distributions.
1657 Some of these coding schemes do not permit the full use of the
1658 Ada character set. For example, neither Shift JIS nor EUC allow the
1659 use of the upper half of the Latin-1 set.
1663 @node Wide_Wide_Character Encodings,,Wide_Character Encodings,Foreign Language Representation
1664 @anchor{gnat_ugn/the_gnat_compilation_model id7}@anchor{4f}@anchor{gnat_ugn/the_gnat_compilation_model wide-wide-character-encodings}@anchor{50}
1665 @subsection Wide_Wide_Character Encodings
1668 GNAT allows wide wide character codes to appear in character and string
1669 literals, and also optionally in identifiers, by means of the following
1670 possible encoding schemes:
1675 @item @emph{UTF-8 Coding}
1677 A wide character is represented using
1678 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1679 10646-1/Am.2. Depending on the character value, the representation
1680 of character codes with values greater than 16#FFFF# is a
1681 is a four, five, or six byte sequence:
1684 16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx
1686 16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx
1688 16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx
1689 10xxxxxx 10xxxxxx 10xxxxxx
1692 where the @code{xxx} bits correspond to the left-padded bits of the
1693 32-bit character value.
1695 @item @emph{Brackets Coding}
1697 In this encoding, a wide wide character is represented by the following ten or
1698 twelve byte character sequence:
1702 [ " a b c d e f g h " ]
1705 where @code{a-h} are the six or eight hexadecimal
1706 characters (using uppercase letters) of the wide wide character code. For
1707 example, ["1F4567"] is used to represent the wide wide character with code
1708 @code{16#001F_4567#}.
1710 This scheme is compatible with use of the full Wide_Wide_Character set,
1711 and is also the method used for wide wide character encoding in some standard
1712 ACATS (Ada Conformity Assessment Test Suite) test suite distributions.
1715 @node File Naming Topics and Utilities,Configuration Pragmas,Foreign Language Representation,The GNAT Compilation Model
1716 @anchor{gnat_ugn/the_gnat_compilation_model id8}@anchor{51}@anchor{gnat_ugn/the_gnat_compilation_model file-naming-topics-and-utilities}@anchor{3f}
1717 @section File Naming Topics and Utilities
1720 GNAT has a default file naming scheme and also provides the user with
1721 a high degree of control over how the names and extensions of the
1722 source files correspond to the Ada compilation units that they contain.
1725 * File Naming Rules::
1726 * Using Other File Names::
1727 * Alternative File Naming Schemes::
1728 * Handling Arbitrary File Naming Conventions with gnatname::
1729 * File Name Krunching with gnatkr::
1730 * Renaming Files with gnatchop::
1734 @node File Naming Rules,Using Other File Names,,File Naming Topics and Utilities
1735 @anchor{gnat_ugn/the_gnat_compilation_model file-naming-rules}@anchor{52}@anchor{gnat_ugn/the_gnat_compilation_model id9}@anchor{53}
1736 @subsection File Naming Rules
1739 The default file name is determined by the name of the unit that the
1740 file contains. The name is formed by taking the full expanded name of
1741 the unit and replacing the separating dots with hyphens and using
1742 lowercase for all letters.
1744 An exception arises if the file name generated by the above rules starts
1745 with one of the characters
1746 @code{a}, @code{g}, @code{i}, or @code{s}, and the second character is a
1747 minus. In this case, the character tilde is used in place
1748 of the minus. The reason for this special rule is to avoid clashes with
1749 the standard names for child units of the packages System, Ada,
1750 Interfaces, and GNAT, which use the prefixes
1751 @code{s-}, @code{a-}, @code{i-}, and @code{g-},
1754 The file extension is @code{.ads} for a spec and
1755 @code{.adb} for a body. The following table shows some
1756 examples of these rules.
1761 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
1768 Ada Compilation Unit
1788 @code{arith_functions.ads}
1792 Arith_Functions (package spec)
1796 @code{arith_functions.adb}
1800 Arith_Functions (package body)
1804 @code{func-spec.ads}
1808 Func.Spec (child package spec)
1812 @code{func-spec.adb}
1816 Func.Spec (child package body)
1824 Sub (subunit of Main)
1832 A.Bad (child package body)
1838 Following these rules can result in excessively long
1839 file names if corresponding
1840 unit names are long (for example, if child units or subunits are
1841 heavily nested). An option is available to shorten such long file names
1842 (called file name 'krunching'). This may be particularly useful when
1843 programs being developed with GNAT are to be used on operating systems
1844 with limited file name lengths. @ref{54,,Using gnatkr}.
1846 Of course, no file shortening algorithm can guarantee uniqueness over
1847 all possible unit names; if file name krunching is used, it is your
1848 responsibility to ensure no name clashes occur. Alternatively you
1849 can specify the exact file names that you want used, as described
1850 in the next section. Finally, if your Ada programs are migrating from a
1851 compiler with a different naming convention, you can use the gnatchop
1852 utility to produce source files that follow the GNAT naming conventions.
1853 (For details see @ref{36,,Renaming Files with gnatchop}.)
1855 Note: in the case of Windows or Mac OS operating systems, case is not
1856 significant. So for example on Windows if the canonical name is
1857 @code{main-sub.adb}, you can use the file name @code{Main-Sub.adb} instead.
1858 However, case is significant for other operating systems, so for example,
1859 if you want to use other than canonically cased file names on a Unix system,
1860 you need to follow the procedures described in the next section.
1862 @node Using Other File Names,Alternative File Naming Schemes,File Naming Rules,File Naming Topics and Utilities
1863 @anchor{gnat_ugn/the_gnat_compilation_model id10}@anchor{55}@anchor{gnat_ugn/the_gnat_compilation_model using-other-file-names}@anchor{35}
1864 @subsection Using Other File Names
1869 In the previous section, we have described the default rules used by
1870 GNAT to determine the file name in which a given unit resides. It is
1871 often convenient to follow these default rules, and if you follow them,
1872 the compiler knows without being explicitly told where to find all
1875 @geindex Source_File_Name pragma
1877 However, in some cases, particularly when a program is imported from
1878 another Ada compiler environment, it may be more convenient for the
1879 programmer to specify which file names contain which units. GNAT allows
1880 arbitrary file names to be used by means of the Source_File_Name pragma.
1881 The form of this pragma is as shown in the following examples:
1884 pragma Source_File_Name (My_Utilities.Stacks,
1885 Spec_File_Name => "myutilst_a.ada");
1886 pragma Source_File_name (My_Utilities.Stacks,
1887 Body_File_Name => "myutilst.ada");
1890 As shown in this example, the first argument for the pragma is the unit
1891 name (in this example a child unit). The second argument has the form
1892 of a named association. The identifier
1893 indicates whether the file name is for a spec or a body;
1894 the file name itself is given by a string literal.
1896 The source file name pragma is a configuration pragma, which means that
1897 normally it will be placed in the @code{gnat.adc}
1898 file used to hold configuration
1899 pragmas that apply to a complete compilation environment.
1900 For more details on how the @code{gnat.adc} file is created and used
1901 see @ref{56,,Handling of Configuration Pragmas}.
1905 GNAT allows completely arbitrary file names to be specified using the
1906 source file name pragma. However, if the file name specified has an
1907 extension other than @code{.ads} or @code{.adb} it is necessary to use
1908 a special syntax when compiling the file. The name in this case must be
1909 preceded by the special sequence @code{-x} followed by a space and the name
1910 of the language, here @code{ada}, as in:
1913 $ gcc -c -x ada peculiar_file_name.sim
1916 @code{gnatmake} handles non-standard file names in the usual manner (the
1917 non-standard file name for the main program is simply used as the
1918 argument to gnatmake). Note that if the extension is also non-standard,
1919 then it must be included in the @code{gnatmake} command, it may not
1922 @node Alternative File Naming Schemes,Handling Arbitrary File Naming Conventions with gnatname,Using Other File Names,File Naming Topics and Utilities
1923 @anchor{gnat_ugn/the_gnat_compilation_model id11}@anchor{57}@anchor{gnat_ugn/the_gnat_compilation_model alternative-file-naming-schemes}@anchor{58}
1924 @subsection Alternative File Naming Schemes
1927 @geindex File naming schemes
1928 @geindex alternative
1932 The previous section described the use of the @code{Source_File_Name}
1933 pragma to allow arbitrary names to be assigned to individual source files.
1934 However, this approach requires one pragma for each file, and especially in
1935 large systems can result in very long @code{gnat.adc} files, and also create
1936 a maintenance problem.
1938 @geindex Source_File_Name pragma
1940 GNAT also provides a facility for specifying systematic file naming schemes
1941 other than the standard default naming scheme previously described. An
1942 alternative scheme for naming is specified by the use of
1943 @code{Source_File_Name} pragmas having the following format:
1946 pragma Source_File_Name (
1947 Spec_File_Name => FILE_NAME_PATTERN
1948 [ , Casing => CASING_SPEC]
1949 [ , Dot_Replacement => STRING_LITERAL ] );
1951 pragma Source_File_Name (
1952 Body_File_Name => FILE_NAME_PATTERN
1953 [ , Casing => CASING_SPEC ]
1954 [ , Dot_Replacement => STRING_LITERAL ] ) ;
1956 pragma Source_File_Name (
1957 Subunit_File_Name => FILE_NAME_PATTERN
1958 [ , Casing => CASING_SPEC ]
1959 [ , Dot_Replacement => STRING_LITERAL ] ) ;
1961 FILE_NAME_PATTERN ::= STRING_LITERAL
1962 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
1965 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
1966 It contains a single asterisk character, and the unit name is substituted
1967 systematically for this asterisk. The optional parameter
1968 @code{Casing} indicates
1969 whether the unit name is to be all upper-case letters, all lower-case letters,
1970 or mixed-case. If no
1971 @code{Casing} parameter is used, then the default is all
1974 The optional @code{Dot_Replacement} string is used to replace any periods
1975 that occur in subunit or child unit names. If no @code{Dot_Replacement}
1976 argument is used then separating dots appear unchanged in the resulting
1978 Although the above syntax indicates that the
1979 @code{Casing} argument must appear
1980 before the @code{Dot_Replacement} argument, but it
1981 is also permissible to write these arguments in the opposite order.
1983 As indicated, it is possible to specify different naming schemes for
1984 bodies, specs, and subunits. Quite often the rule for subunits is the
1985 same as the rule for bodies, in which case, there is no need to give
1986 a separate @code{Subunit_File_Name} rule, and in this case the
1987 @code{Body_File_name} rule is used for subunits as well.
1989 The separate rule for subunits can also be used to implement the rather
1990 unusual case of a compilation environment (e.g., a single directory) which
1991 contains a subunit and a child unit with the same unit name. Although
1992 both units cannot appear in the same partition, the Ada Reference Manual
1993 allows (but does not require) the possibility of the two units coexisting
1994 in the same environment.
1996 The file name translation works in the following steps:
2002 If there is a specific @code{Source_File_Name} pragma for the given unit,
2003 then this is always used, and any general pattern rules are ignored.
2006 If there is a pattern type @code{Source_File_Name} pragma that applies to
2007 the unit, then the resulting file name will be used if the file exists. If
2008 more than one pattern matches, the latest one will be tried first, and the
2009 first attempt resulting in a reference to a file that exists will be used.
2012 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2013 for which the corresponding file exists, then the standard GNAT default
2014 naming rules are used.
2017 As an example of the use of this mechanism, consider a commonly used scheme
2018 in which file names are all lower case, with separating periods copied
2019 unchanged to the resulting file name, and specs end with @code{.1.ada}, and
2020 bodies end with @code{.2.ada}. GNAT will follow this scheme if the following
2024 pragma Source_File_Name
2025 (Spec_File_Name => ".1.ada");
2026 pragma Source_File_Name
2027 (Body_File_Name => ".2.ada");
2030 The default GNAT scheme is actually implemented by providing the following
2031 default pragmas internally:
2034 pragma Source_File_Name
2035 (Spec_File_Name => ".ads", Dot_Replacement => "-");
2036 pragma Source_File_Name
2037 (Body_File_Name => ".adb", Dot_Replacement => "-");
2040 Our final example implements a scheme typically used with one of the
2041 Ada 83 compilers, where the separator character for subunits was '__'
2042 (two underscores), specs were identified by adding @code{_.ADA}, bodies
2043 by adding @code{.ADA}, and subunits by
2044 adding @code{.SEP}. All file names were
2045 upper case. Child units were not present of course since this was an
2046 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2047 the same double underscore separator for child units.
2050 pragma Source_File_Name
2051 (Spec_File_Name => "_.ADA",
2052 Dot_Replacement => "__",
2053 Casing = Uppercase);
2054 pragma Source_File_Name
2055 (Body_File_Name => ".ADA",
2056 Dot_Replacement => "__",
2057 Casing = Uppercase);
2058 pragma Source_File_Name
2059 (Subunit_File_Name => ".SEP",
2060 Dot_Replacement => "__",
2061 Casing = Uppercase);
2066 @node Handling Arbitrary File Naming Conventions with gnatname,File Name Krunching with gnatkr,Alternative File Naming Schemes,File Naming Topics and Utilities
2067 @anchor{gnat_ugn/the_gnat_compilation_model handling-arbitrary-file-naming-conventions-with-gnatname}@anchor{59}@anchor{gnat_ugn/the_gnat_compilation_model id12}@anchor{5a}
2068 @subsection Handling Arbitrary File Naming Conventions with @code{gnatname}
2071 @geindex File Naming Conventions
2074 * Arbitrary File Naming Conventions::
2075 * Running gnatname::
2076 * Switches for gnatname::
2077 * Examples of gnatname Usage::
2081 @node Arbitrary File Naming Conventions,Running gnatname,,Handling Arbitrary File Naming Conventions with gnatname
2082 @anchor{gnat_ugn/the_gnat_compilation_model arbitrary-file-naming-conventions}@anchor{5b}@anchor{gnat_ugn/the_gnat_compilation_model id13}@anchor{5c}
2083 @subsubsection Arbitrary File Naming Conventions
2086 The GNAT compiler must be able to know the source file name of a compilation
2087 unit. When using the standard GNAT default file naming conventions
2088 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
2089 does not need additional information.
2091 When the source file names do not follow the standard GNAT default file naming
2092 conventions, the GNAT compiler must be given additional information through
2093 a configuration pragmas file (@ref{14,,Configuration Pragmas})
2095 When the non-standard file naming conventions are well-defined,
2096 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
2097 (@ref{58,,Alternative File Naming Schemes}) may be sufficient. However,
2098 if the file naming conventions are irregular or arbitrary, a number
2099 of pragma @code{Source_File_Name} for individual compilation units
2101 To help maintain the correspondence between compilation unit names and
2102 source file names within the compiler,
2103 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
2106 @node Running gnatname,Switches for gnatname,Arbitrary File Naming Conventions,Handling Arbitrary File Naming Conventions with gnatname
2107 @anchor{gnat_ugn/the_gnat_compilation_model running-gnatname}@anchor{5d}@anchor{gnat_ugn/the_gnat_compilation_model id14}@anchor{5e}
2108 @subsubsection Running @code{gnatname}
2111 The usual form of the @code{gnatname} command is:
2114 $ gnatname [ switches ] naming_pattern [ naming_patterns ]
2115 [--and [ switches ] naming_pattern [ naming_patterns ]]
2118 All of the arguments are optional. If invoked without any argument,
2119 @code{gnatname} will display its usage.
2121 When used with at least one naming pattern, @code{gnatname} will attempt to
2122 find all the compilation units in files that follow at least one of the
2123 naming patterns. To find these compilation units,
2124 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
2127 One or several Naming Patterns may be given as arguments to @code{gnatname}.
2128 Each Naming Pattern is enclosed between double quotes (or single
2130 A Naming Pattern is a regular expression similar to the wildcard patterns
2131 used in file names by the Unix shells or the DOS prompt.
2133 @code{gnatname} may be called with several sections of directories/patterns.
2134 Sections are separated by the switch @code{--and}. In each section, there must be
2135 at least one pattern. If no directory is specified in a section, the current
2136 directory (or the project directory if @code{-P} is used) is implied.
2137 The options other that the directory switches and the patterns apply globally
2138 even if they are in different sections.
2140 Examples of Naming Patterns are:
2148 For a more complete description of the syntax of Naming Patterns,
2149 see the second kind of regular expressions described in @code{g-regexp.ads}
2150 (the 'Glob' regular expressions).
2152 When invoked without the switch @code{-P}, @code{gnatname} will create a
2153 configuration pragmas file @code{gnat.adc} in the current working directory,
2154 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
2157 @node Switches for gnatname,Examples of gnatname Usage,Running gnatname,Handling Arbitrary File Naming Conventions with gnatname
2158 @anchor{gnat_ugn/the_gnat_compilation_model id15}@anchor{5f}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatname}@anchor{60}
2159 @subsubsection Switches for @code{gnatname}
2162 Switches for @code{gnatname} must precede any specified Naming Pattern.
2164 You may specify any of the following switches to @code{gnatname}:
2166 @geindex --version (gnatname)
2171 @item @code{--version}
2173 Display Copyright and version, then exit disregarding all other options.
2176 @geindex --help (gnatname)
2183 If @code{--version} was not used, display usage, then exit disregarding
2186 @item @code{--subdirs=@emph{dir}}
2188 Real object, library or exec directories are subdirectories <dir> of the
2191 @item @code{--no-backup}
2193 Do not create a backup copy of an existing project file.
2197 Start another section of directories/patterns.
2200 @geindex -c (gnatname)
2205 @item @code{-c@emph{filename}}
2207 Create a configuration pragmas file @code{filename} (instead of the default
2209 There may be zero, one or more space between @code{-c} and
2211 @code{filename} may include directory information. @code{filename} must be
2212 writable. There may be only one switch @code{-c}.
2213 When a switch @code{-c} is
2214 specified, no switch @code{-P} may be specified (see below).
2217 @geindex -d (gnatname)
2222 @item @code{-d@emph{dir}}
2224 Look for source files in directory @code{dir}. There may be zero, one or more
2225 spaces between @code{-d} and @code{dir}.
2226 @code{dir} may end with @code{/**}, that is it may be of the form
2227 @code{root_dir/**}. In this case, the directory @code{root_dir} and all of its
2228 subdirectories, recursively, have to be searched for sources.
2229 When a switch @code{-d}
2230 is specified, the current working directory will not be searched for source
2231 files, unless it is explicitly specified with a @code{-d}
2232 or @code{-D} switch.
2233 Several switches @code{-d} may be specified.
2234 If @code{dir} is a relative path, it is relative to the directory of
2235 the configuration pragmas file specified with switch
2237 or to the directory of the project file specified with switch
2239 if neither switch @code{-c}
2240 nor switch @code{-P} are specified, it is relative to the
2241 current working directory. The directory
2242 specified with switch @code{-d} must exist and be readable.
2245 @geindex -D (gnatname)
2250 @item @code{-D@emph{filename}}
2252 Look for source files in all directories listed in text file @code{filename}.
2253 There may be zero, one or more spaces between @code{-D}
2254 and @code{filename}.
2255 @code{filename} must be an existing, readable text file.
2256 Each nonempty line in @code{filename} must be a directory.
2257 Specifying switch @code{-D} is equivalent to specifying as many
2258 switches @code{-d} as there are nonempty lines in
2263 Follow symbolic links when processing project files.
2265 @geindex -f (gnatname)
2267 @item @code{-f@emph{pattern}}
2269 Foreign patterns. Using this switch, it is possible to add sources of languages
2270 other than Ada to the list of sources of a project file.
2271 It is only useful if a -P switch is used.
2275 gnatname -Pprj -f"*.c" "*.ada"
2278 will look for Ada units in all files with the @code{.ada} extension,
2279 and will add to the list of file for project @code{prj.gpr} the C files
2280 with extension @code{.c}.
2282 @geindex -h (gnatname)
2286 Output usage (help) information. The output is written to @code{stdout}.
2288 @geindex -P (gnatname)
2290 @item @code{-P@emph{proj}}
2292 Create or update project file @code{proj}. There may be zero, one or more space
2293 between @code{-P} and @code{proj}. @code{proj} may include directory
2294 information. @code{proj} must be writable.
2295 There may be only one switch @code{-P}.
2296 When a switch @code{-P} is specified,
2297 no switch @code{-c} may be specified.
2298 On all platforms, except on VMS, when @code{gnatname} is invoked for an
2299 existing project file <proj>.gpr, a backup copy of the project file is created
2300 in the project directory with file name <proj>.gpr.saved_x. 'x' is the first
2301 non negative number that makes this backup copy a new file.
2303 @geindex -v (gnatname)
2307 Verbose mode. Output detailed explanation of behavior to @code{stdout}.
2308 This includes name of the file written, the name of the directories to search
2309 and, for each file in those directories whose name matches at least one of
2310 the Naming Patterns, an indication of whether the file contains a unit,
2311 and if so the name of the unit.
2314 @geindex -v -v (gnatname)
2321 Very Verbose mode. In addition to the output produced in verbose mode,
2322 for each file in the searched directories whose name matches none of
2323 the Naming Patterns, an indication is given that there is no match.
2325 @geindex -x (gnatname)
2327 @item @code{-x@emph{pattern}}
2329 Excluded patterns. Using this switch, it is possible to exclude some files
2330 that would match the name patterns. For example,
2333 gnatname -x "*_nt.ada" "*.ada"
2336 will look for Ada units in all files with the @code{.ada} extension,
2337 except those whose names end with @code{_nt.ada}.
2340 @node Examples of gnatname Usage,,Switches for gnatname,Handling Arbitrary File Naming Conventions with gnatname
2341 @anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatname-usage}@anchor{61}@anchor{gnat_ugn/the_gnat_compilation_model id16}@anchor{62}
2342 @subsubsection Examples of @code{gnatname} Usage
2346 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
2349 In this example, the directory @code{/home/me} must already exist
2350 and be writable. In addition, the directory
2351 @code{/home/me/sources} (specified by
2352 @code{-d sources}) must exist and be readable.
2354 Note the optional spaces after @code{-c} and @code{-d}.
2357 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
2358 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
2361 Note that several switches @code{-d} may be used,
2362 even in conjunction with one or several switches
2363 @code{-D}. Several Naming Patterns and one excluded pattern
2364 are used in this example.
2366 @node File Name Krunching with gnatkr,Renaming Files with gnatchop,Handling Arbitrary File Naming Conventions with gnatname,File Naming Topics and Utilities
2367 @anchor{gnat_ugn/the_gnat_compilation_model file-name-krunching-with-gnatkr}@anchor{63}@anchor{gnat_ugn/the_gnat_compilation_model id17}@anchor{64}
2368 @subsection File Name Krunching with @code{gnatkr}
2373 This section discusses the method used by the compiler to shorten
2374 the default file names chosen for Ada units so that they do not
2375 exceed the maximum length permitted. It also describes the
2376 @code{gnatkr} utility that can be used to determine the result of
2377 applying this shortening.
2382 * Krunching Method::
2383 * Examples of gnatkr Usage::
2387 @node About gnatkr,Using gnatkr,,File Name Krunching with gnatkr
2388 @anchor{gnat_ugn/the_gnat_compilation_model id18}@anchor{65}@anchor{gnat_ugn/the_gnat_compilation_model about-gnatkr}@anchor{66}
2389 @subsubsection About @code{gnatkr}
2392 The default file naming rule in GNAT
2393 is that the file name must be derived from
2394 the unit name. The exact default rule is as follows:
2400 Take the unit name and replace all dots by hyphens.
2403 If such a replacement occurs in the
2404 second character position of a name, and the first character is
2405 @code{a}, @code{g}, @code{s}, or @code{i},
2406 then replace the dot by the character
2410 The reason for this exception is to avoid clashes
2411 with the standard names for children of System, Ada, Interfaces,
2412 and GNAT, which use the prefixes
2413 @code{s-}, @code{a-}, @code{i-}, and @code{g-},
2417 The @code{-gnatk@emph{nn}}
2418 switch of the compiler activates a 'krunching'
2419 circuit that limits file names to nn characters (where nn is a decimal
2422 The @code{gnatkr} utility can be used to determine the krunched name for
2423 a given file, when krunched to a specified maximum length.
2425 @node Using gnatkr,Krunching Method,About gnatkr,File Name Krunching with gnatkr
2426 @anchor{gnat_ugn/the_gnat_compilation_model id19}@anchor{67}@anchor{gnat_ugn/the_gnat_compilation_model using-gnatkr}@anchor{54}
2427 @subsubsection Using @code{gnatkr}
2430 The @code{gnatkr} command has the form:
2433 $ gnatkr name [ length ]
2436 @code{name} is the uncrunched file name, derived from the name of the unit
2437 in the standard manner described in the previous section (i.e., in particular
2438 all dots are replaced by hyphens). The file name may or may not have an
2439 extension (defined as a suffix of the form period followed by arbitrary
2440 characters other than period). If an extension is present then it will
2441 be preserved in the output. For example, when krunching @code{hellofile.ads}
2442 to eight characters, the result will be hellofil.ads.
2444 Note: for compatibility with previous versions of @code{gnatkr} dots may
2445 appear in the name instead of hyphens, but the last dot will always be
2446 taken as the start of an extension. So if @code{gnatkr} is given an argument
2447 such as @code{Hello.World.adb} it will be treated exactly as if the first
2448 period had been a hyphen, and for example krunching to eight characters
2449 gives the result @code{hellworl.adb}.
2451 Note that the result is always all lower case.
2452 Characters of the other case are folded as required.
2454 @code{length} represents the length of the krunched name. The default
2455 when no argument is given is 8 characters. A length of zero stands for
2456 unlimited, in other words do not chop except for system files where the
2457 implied crunching length is always eight characters.
2459 The output is the krunched name. The output has an extension only if the
2460 original argument was a file name with an extension.
2462 @node Krunching Method,Examples of gnatkr Usage,Using gnatkr,File Name Krunching with gnatkr
2463 @anchor{gnat_ugn/the_gnat_compilation_model id20}@anchor{68}@anchor{gnat_ugn/the_gnat_compilation_model krunching-method}@anchor{69}
2464 @subsubsection Krunching Method
2467 The initial file name is determined by the name of the unit that the file
2468 contains. The name is formed by taking the full expanded name of the
2469 unit and replacing the separating dots with hyphens and
2471 for all letters, except that a hyphen in the second character position is
2472 replaced by a tilde if the first character is
2473 @code{a}, @code{i}, @code{g}, or @code{s}.
2474 The extension is @code{.ads} for a
2475 spec and @code{.adb} for a body.
2476 Krunching does not affect the extension, but the file name is shortened to
2477 the specified length by following these rules:
2483 The name is divided into segments separated by hyphens, tildes or
2484 underscores and all hyphens, tildes, and underscores are
2485 eliminated. If this leaves the name short enough, we are done.
2488 If the name is too long, the longest segment is located (left-most
2489 if there are two of equal length), and shortened by dropping
2490 its last character. This is repeated until the name is short enough.
2492 As an example, consider the krunching of @code{our-strings-wide_fixed.adb}
2493 to fit the name into 8 characters as required by some operating systems:
2496 our-strings-wide_fixed 22
2497 our strings wide fixed 19
2498 our string wide fixed 18
2499 our strin wide fixed 17
2500 our stri wide fixed 16
2501 our stri wide fixe 15
2502 our str wide fixe 14
2509 Final file name: oustwifi.adb
2513 The file names for all predefined units are always krunched to eight
2514 characters. The krunching of these predefined units uses the following
2515 special prefix replacements:
2518 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx}
2562 These system files have a hyphen in the second character position. That
2563 is why normal user files replace such a character with a
2564 tilde, to avoid confusion with system file names.
2566 As an example of this special rule, consider
2567 @code{ada-strings-wide_fixed.adb}, which gets krunched as follows:
2570 ada-strings-wide_fixed 22
2571 a- strings wide fixed 18
2572 a- string wide fixed 17
2573 a- strin wide fixed 16
2574 a- stri wide fixed 15
2575 a- stri wide fixe 14
2582 Final file name: a-stwifi.adb
2586 Of course no file shortening algorithm can guarantee uniqueness over all
2587 possible unit names, and if file name krunching is used then it is your
2588 responsibility to ensure that no name clashes occur. The utility
2589 program @code{gnatkr} is supplied for conveniently determining the
2590 krunched name of a file.
2592 @node Examples of gnatkr Usage,,Krunching Method,File Name Krunching with gnatkr
2593 @anchor{gnat_ugn/the_gnat_compilation_model id21}@anchor{6a}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatkr-usage}@anchor{6b}
2594 @subsubsection Examples of @code{gnatkr} Usage
2598 $ gnatkr very_long_unit_name.ads --> velounna.ads
2599 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
2600 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
2601 $ gnatkr grandparent-parent-child --> grparchi
2602 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
2603 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
2606 @node Renaming Files with gnatchop,,File Name Krunching with gnatkr,File Naming Topics and Utilities
2607 @anchor{gnat_ugn/the_gnat_compilation_model id22}@anchor{6c}@anchor{gnat_ugn/the_gnat_compilation_model renaming-files-with-gnatchop}@anchor{36}
2608 @subsection Renaming Files with @code{gnatchop}
2613 This section discusses how to handle files with multiple units by using
2614 the @code{gnatchop} utility. This utility is also useful in renaming
2615 files to meet the standard GNAT default file naming conventions.
2618 * Handling Files with Multiple Units::
2619 * Operating gnatchop in Compilation Mode::
2620 * Command Line for gnatchop::
2621 * Switches for gnatchop::
2622 * Examples of gnatchop Usage::
2626 @node Handling Files with Multiple Units,Operating gnatchop in Compilation Mode,,Renaming Files with gnatchop
2627 @anchor{gnat_ugn/the_gnat_compilation_model id23}@anchor{6d}@anchor{gnat_ugn/the_gnat_compilation_model handling-files-with-multiple-units}@anchor{6e}
2628 @subsubsection Handling Files with Multiple Units
2631 The basic compilation model of GNAT requires that a file submitted to the
2632 compiler have only one unit and there be a strict correspondence
2633 between the file name and the unit name.
2635 The @code{gnatchop} utility allows both of these rules to be relaxed,
2636 allowing GNAT to process files which contain multiple compilation units
2637 and files with arbitrary file names. @code{gnatchop}
2638 reads the specified file and generates one or more output files,
2639 containing one unit per file. The unit and the file name correspond,
2640 as required by GNAT.
2642 If you want to permanently restructure a set of 'foreign' files so that
2643 they match the GNAT rules, and do the remaining development using the
2644 GNAT structure, you can simply use @code{gnatchop} once, generate the
2645 new set of files and work with them from that point on.
2647 Alternatively, if you want to keep your files in the 'foreign' format,
2648 perhaps to maintain compatibility with some other Ada compilation
2649 system, you can set up a procedure where you use @code{gnatchop} each
2650 time you compile, regarding the source files that it writes as temporary
2651 files that you throw away.
2653 Note that if your file containing multiple units starts with a byte order
2654 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
2655 will each start with a copy of this BOM, meaning that they can be compiled
2656 automatically in UTF-8 mode without needing to specify an explicit encoding.
2658 @node Operating gnatchop in Compilation Mode,Command Line for gnatchop,Handling Files with Multiple Units,Renaming Files with gnatchop
2659 @anchor{gnat_ugn/the_gnat_compilation_model operating-gnatchop-in-compilation-mode}@anchor{6f}@anchor{gnat_ugn/the_gnat_compilation_model id24}@anchor{70}
2660 @subsubsection Operating gnatchop in Compilation Mode
2663 The basic function of @code{gnatchop} is to take a file with multiple units
2664 and split it into separate files. The boundary between files is reasonably
2665 clear, except for the issue of comments and pragmas. In default mode, the
2666 rule is that any pragmas between units belong to the previous unit, except
2667 that configuration pragmas always belong to the following unit. Any comments
2668 belong to the following unit. These rules
2669 almost always result in the right choice of
2670 the split point without needing to mark it explicitly and most users will
2671 find this default to be what they want. In this default mode it is incorrect to
2672 submit a file containing only configuration pragmas, or one that ends in
2673 configuration pragmas, to @code{gnatchop}.
2675 However, using a special option to activate 'compilation mode',
2677 can perform another function, which is to provide exactly the semantics
2678 required by the RM for handling of configuration pragmas in a compilation.
2679 In the absence of configuration pragmas (at the main file level), this
2680 option has no effect, but it causes such configuration pragmas to be handled
2681 in a quite different manner.
2683 First, in compilation mode, if @code{gnatchop} is given a file that consists of
2684 only configuration pragmas, then this file is appended to the
2685 @code{gnat.adc} file in the current directory. This behavior provides
2686 the required behavior described in the RM for the actions to be taken
2687 on submitting such a file to the compiler, namely that these pragmas
2688 should apply to all subsequent compilations in the same compilation
2689 environment. Using GNAT, the current directory, possibly containing a
2690 @code{gnat.adc} file is the representation
2691 of a compilation environment. For more information on the
2692 @code{gnat.adc} file, see @ref{56,,Handling of Configuration Pragmas}.
2694 Second, in compilation mode, if @code{gnatchop}
2695 is given a file that starts with
2696 configuration pragmas, and contains one or more units, then these
2697 configuration pragmas are prepended to each of the chopped files. This
2698 behavior provides the required behavior described in the RM for the
2699 actions to be taken on compiling such a file, namely that the pragmas
2700 apply to all units in the compilation, but not to subsequently compiled
2703 Finally, if configuration pragmas appear between units, they are appended
2704 to the previous unit. This results in the previous unit being illegal,
2705 since the compiler does not accept configuration pragmas that follow
2706 a unit. This provides the required RM behavior that forbids configuration
2707 pragmas other than those preceding the first compilation unit of a
2710 For most purposes, @code{gnatchop} will be used in default mode. The
2711 compilation mode described above is used only if you need exactly
2712 accurate behavior with respect to compilations, and you have files
2713 that contain multiple units and configuration pragmas. In this
2714 circumstance the use of @code{gnatchop} with the compilation mode
2715 switch provides the required behavior, and is for example the mode
2716 in which GNAT processes the ACVC tests.
2718 @node Command Line for gnatchop,Switches for gnatchop,Operating gnatchop in Compilation Mode,Renaming Files with gnatchop
2719 @anchor{gnat_ugn/the_gnat_compilation_model id25}@anchor{71}@anchor{gnat_ugn/the_gnat_compilation_model command-line-for-gnatchop}@anchor{72}
2720 @subsubsection Command Line for @code{gnatchop}
2723 The @code{gnatchop} command has the form:
2726 $ gnatchop switches file_name [file_name ...]
2730 The only required argument is the file name of the file to be chopped.
2731 There are no restrictions on the form of this file name. The file itself
2732 contains one or more Ada units, in normal GNAT format, concatenated
2733 together. As shown, more than one file may be presented to be chopped.
2735 When run in default mode, @code{gnatchop} generates one output file in
2736 the current directory for each unit in each of the files.
2738 @code{directory}, if specified, gives the name of the directory to which
2739 the output files will be written. If it is not specified, all files are
2740 written to the current directory.
2742 For example, given a
2743 file called @code{hellofiles} containing
2748 with Ada.Text_IO; use Ada.Text_IO;
2758 $ gnatchop hellofiles
2761 generates two files in the current directory, one called
2762 @code{hello.ads} containing the single line that is the procedure spec,
2763 and the other called @code{hello.adb} containing the remaining text. The
2764 original file is not affected. The generated files can be compiled in
2767 When gnatchop is invoked on a file that is empty or that contains only empty
2768 lines and/or comments, gnatchop will not fail, but will not produce any
2771 For example, given a
2772 file called @code{toto.txt} containing
2784 will not produce any new file and will result in the following warnings:
2787 toto.txt:1:01: warning: empty file, contains no compilation units
2788 no compilation units found
2789 no source files written
2792 @node Switches for gnatchop,Examples of gnatchop Usage,Command Line for gnatchop,Renaming Files with gnatchop
2793 @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatchop}@anchor{73}@anchor{gnat_ugn/the_gnat_compilation_model id26}@anchor{74}
2794 @subsubsection Switches for @code{gnatchop}
2797 @code{gnatchop} recognizes the following switches:
2799 @geindex --version (gnatchop)
2804 @item @code{--version}
2806 Display Copyright and version, then exit disregarding all other options.
2809 @geindex --help (gnatchop)
2816 If @code{--version} was not used, display usage, then exit disregarding
2820 @geindex -c (gnatchop)
2827 Causes @code{gnatchop} to operate in compilation mode, in which
2828 configuration pragmas are handled according to strict RM rules. See
2829 previous section for a full description of this mode.
2831 @item @code{-gnat@emph{xxx}}
2833 This passes the given @code{-gnat@emph{xxx}} switch to @code{gnat} which is
2834 used to parse the given file. Not all @emph{xxx} options make sense,
2835 but for example, the use of @code{-gnati2} allows @code{gnatchop} to
2836 process a source file that uses Latin-2 coding for identifiers.
2840 Causes @code{gnatchop} to generate a brief help summary to the standard
2841 output file showing usage information.
2844 @geindex -k (gnatchop)
2849 @item @code{-k@emph{mm}}
2851 Limit generated file names to the specified number @code{mm}
2853 This is useful if the
2854 resulting set of files is required to be interoperable with systems
2855 which limit the length of file names.
2856 No space is allowed between the @code{-k} and the numeric value. The numeric
2857 value may be omitted in which case a default of @code{-k8},
2859 with DOS-like file systems, is used. If no @code{-k} switch
2861 there is no limit on the length of file names.
2864 @geindex -p (gnatchop)
2871 Causes the file modification time stamp of the input file to be
2872 preserved and used for the time stamp of the output file(s). This may be
2873 useful for preserving coherency of time stamps in an environment where
2874 @code{gnatchop} is used as part of a standard build process.
2877 @geindex -q (gnatchop)
2884 Causes output of informational messages indicating the set of generated
2885 files to be suppressed. Warnings and error messages are unaffected.
2888 @geindex -r (gnatchop)
2890 @geindex Source_Reference pragmas
2897 Generate @code{Source_Reference} pragmas. Use this switch if the output
2898 files are regarded as temporary and development is to be done in terms
2899 of the original unchopped file. This switch causes
2900 @code{Source_Reference} pragmas to be inserted into each of the
2901 generated files to refers back to the original file name and line number.
2902 The result is that all error messages refer back to the original
2904 In addition, the debugging information placed into the object file (when
2905 the @code{-g} switch of @code{gcc} or @code{gnatmake} is
2907 also refers back to this original file so that tools like profilers and
2908 debuggers will give information in terms of the original unchopped file.
2910 If the original file to be chopped itself contains
2911 a @code{Source_Reference}
2912 pragma referencing a third file, then gnatchop respects
2913 this pragma, and the generated @code{Source_Reference} pragmas
2914 in the chopped file refer to the original file, with appropriate
2915 line numbers. This is particularly useful when @code{gnatchop}
2916 is used in conjunction with @code{gnatprep} to compile files that
2917 contain preprocessing statements and multiple units.
2920 @geindex -v (gnatchop)
2927 Causes @code{gnatchop} to operate in verbose mode. The version
2928 number and copyright notice are output, as well as exact copies of
2929 the gnat1 commands spawned to obtain the chop control information.
2932 @geindex -w (gnatchop)
2939 Overwrite existing file names. Normally @code{gnatchop} regards it as a
2940 fatal error if there is already a file with the same name as a
2941 file it would otherwise output, in other words if the files to be
2942 chopped contain duplicated units. This switch bypasses this
2943 check, and causes all but the last instance of such duplicated
2944 units to be skipped.
2947 @geindex --GCC= (gnatchop)
2952 @item @code{--GCC=@emph{xxxx}}
2954 Specify the path of the GNAT parser to be used. When this switch is used,
2955 no attempt is made to add the prefix to the GNAT parser executable.
2958 @node Examples of gnatchop Usage,,Switches for gnatchop,Renaming Files with gnatchop
2959 @anchor{gnat_ugn/the_gnat_compilation_model id27}@anchor{75}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatchop-usage}@anchor{76}
2960 @subsubsection Examples of @code{gnatchop} Usage
2964 $ gnatchop -w hello_s.ada prerelease/files
2967 Chops the source file @code{hello_s.ada}. The output files will be
2968 placed in the directory @code{prerelease/files},
2970 files with matching names in that directory (no files in the current
2971 directory are modified).
2977 Chops the source file @code{archive}
2978 into the current directory. One
2979 useful application of @code{gnatchop} is in sending sets of sources
2980 around, for example in email messages. The required sources are simply
2981 concatenated (for example, using a Unix @code{cat}
2983 @code{gnatchop} is used at the other end to reconstitute the original
2987 $ gnatchop file1 file2 file3 direc
2990 Chops all units in files @code{file1}, @code{file2}, @code{file3}, placing
2991 the resulting files in the directory @code{direc}. Note that if any units
2992 occur more than once anywhere within this set of files, an error message
2993 is generated, and no files are written. To override this check, use the
2995 in which case the last occurrence in the last file will
2996 be the one that is output, and earlier duplicate occurrences for a given
2997 unit will be skipped.
2999 @node Configuration Pragmas,Generating Object Files,File Naming Topics and Utilities,The GNAT Compilation Model
3000 @anchor{gnat_ugn/the_gnat_compilation_model id28}@anchor{77}@anchor{gnat_ugn/the_gnat_compilation_model configuration-pragmas}@anchor{14}
3001 @section Configuration Pragmas
3004 @geindex Configuration pragmas
3007 @geindex configuration
3009 Configuration pragmas include those pragmas described as
3010 such in the Ada Reference Manual, as well as
3011 implementation-dependent pragmas that are configuration pragmas.
3012 See the @code{Implementation_Defined_Pragmas} chapter in the
3013 @cite{GNAT_Reference_Manual} for details on these
3014 additional GNAT-specific configuration pragmas.
3015 Most notably, the pragma @code{Source_File_Name}, which allows
3016 specifying non-default names for source files, is a configuration
3017 pragma. The following is a complete list of configuration pragmas
3027 Allow_Integer_Address
3030 Assume_No_Invalid_Values
3032 Check_Float_Overflow
3036 Compile_Time_Warning
3038 Compiler_Unit_Warning
3040 Convention_Identifier
3043 Default_Scalar_Storage_Order
3044 Default_Storage_Pool
3045 Disable_Atomic_Synchronization
3049 Enable_Atomic_Synchronization
3052 External_Name_Casing
3061 No_Component_Reordering
3062 No_Heap_Finalization
3068 Overriding_Renamings
3069 Partition_Elaboration_Policy
3072 Prefix_Exception_Messages
3073 Priority_Specific_Dispatching
3076 Propagate_Exceptions
3083 Restrictions_Warnings
3085 Short_Circuit_And_Or
3088 Source_File_Name_Project
3092 Suppress_Exception_Locations
3093 Task_Dispatching_Policy
3094 Unevaluated_Use_Of_Old
3101 Wide_Character_Encoding
3105 * Handling of Configuration Pragmas::
3106 * The Configuration Pragmas Files::
3110 @node Handling of Configuration Pragmas,The Configuration Pragmas Files,,Configuration Pragmas
3111 @anchor{gnat_ugn/the_gnat_compilation_model id29}@anchor{78}@anchor{gnat_ugn/the_gnat_compilation_model handling-of-configuration-pragmas}@anchor{56}
3112 @subsection Handling of Configuration Pragmas
3115 Configuration pragmas may either appear at the start of a compilation
3116 unit, or they can appear in a configuration pragma file to apply to
3117 all compilations performed in a given compilation environment.
3119 GNAT also provides the @code{gnatchop} utility to provide an automatic
3120 way to handle configuration pragmas following the semantics for
3121 compilations (that is, files with multiple units), described in the RM.
3122 See @ref{6f,,Operating gnatchop in Compilation Mode} for details.
3123 However, for most purposes, it will be more convenient to edit the
3124 @code{gnat.adc} file that contains configuration pragmas directly,
3125 as described in the following section.
3127 In the case of @code{Restrictions} pragmas appearing as configuration
3128 pragmas in individual compilation units, the exact handling depends on
3129 the type of restriction.
3131 Restrictions that require partition-wide consistency (like
3132 @code{No_Tasking}) are
3133 recognized wherever they appear
3134 and can be freely inherited, e.g. from a @emph{with}ed unit to the @emph{with}ing
3135 unit. This makes sense since the binder will in any case insist on seeing
3136 consistent use, so any unit not conforming to any restrictions that are
3137 anywhere in the partition will be rejected, and you might as well find
3138 that out at compile time rather than at bind time.
3140 For restrictions that do not require partition-wide consistency, e.g.
3141 SPARK or No_Implementation_Attributes, in general the restriction applies
3142 only to the unit in which the pragma appears, and not to any other units.
3144 The exception is No_Elaboration_Code which always applies to the entire
3145 object file from a compilation, i.e. to the body, spec, and all subunits.
3146 This restriction can be specified in a configuration pragma file, or it
3147 can be on the body and/or the spec (in eithe case it applies to all the
3148 relevant units). It can appear on a subunit only if it has previously
3149 appeared in the body of spec.
3151 @node The Configuration Pragmas Files,,Handling of Configuration Pragmas,Configuration Pragmas
3152 @anchor{gnat_ugn/the_gnat_compilation_model the-configuration-pragmas-files}@anchor{79}@anchor{gnat_ugn/the_gnat_compilation_model id30}@anchor{7a}
3153 @subsection The Configuration Pragmas Files
3158 In GNAT a compilation environment is defined by the current
3159 directory at the time that a compile command is given. This current
3160 directory is searched for a file whose name is @code{gnat.adc}. If
3161 this file is present, it is expected to contain one or more
3162 configuration pragmas that will be applied to the current compilation.
3163 However, if the switch @code{-gnatA} is used, @code{gnat.adc} is not
3164 considered. When taken into account, @code{gnat.adc} is added to the
3165 dependencies, so that if @code{gnat.adc} is modified later, an invocation of
3166 @code{gnatmake} will recompile the source.
3168 Configuration pragmas may be entered into the @code{gnat.adc} file
3169 either by running @code{gnatchop} on a source file that consists only of
3170 configuration pragmas, or more conveniently by direct editing of the
3171 @code{gnat.adc} file, which is a standard format source file.
3173 Besides @code{gnat.adc}, additional files containing configuration
3174 pragmas may be applied to the current compilation using the switch
3175 @code{-gnatec=@emph{path}} where @code{path} must designate an existing file that
3176 contains only configuration pragmas. These configuration pragmas are
3177 in addition to those found in @code{gnat.adc} (provided @code{gnat.adc}
3178 is present and switch @code{-gnatA} is not used).
3180 It is allowable to specify several switches @code{-gnatec=}, all of which
3181 will be taken into account.
3183 Files containing configuration pragmas specified with switches
3184 @code{-gnatec=} are added to the dependencies, unless they are
3185 temporary files. A file is considered temporary if its name ends in
3186 @code{.tmp} or @code{.TMP}. Certain tools follow this naming
3187 convention because they pass information to @code{gcc} via
3188 temporary files that are immediately deleted; it doesn't make sense to
3189 depend on a file that no longer exists. Such tools include
3190 @code{gprbuild}, @code{gnatmake}, and @code{gnatcheck}.
3192 If you are using project file, a separate mechanism is provided using
3196 @c See :ref:`Specifying_Configuration_Pragmas` for more details.
3198 @node Generating Object Files,Source Dependencies,Configuration Pragmas,The GNAT Compilation Model
3199 @anchor{gnat_ugn/the_gnat_compilation_model generating-object-files}@anchor{40}@anchor{gnat_ugn/the_gnat_compilation_model id31}@anchor{7b}
3200 @section Generating Object Files
3203 An Ada program consists of a set of source files, and the first step in
3204 compiling the program is to generate the corresponding object files.
3205 These are generated by compiling a subset of these source files.
3206 The files you need to compile are the following:
3212 If a package spec has no body, compile the package spec to produce the
3213 object file for the package.
3216 If a package has both a spec and a body, compile the body to produce the
3217 object file for the package. The source file for the package spec need
3218 not be compiled in this case because there is only one object file, which
3219 contains the code for both the spec and body of the package.
3222 For a subprogram, compile the subprogram body to produce the object file
3223 for the subprogram. The spec, if one is present, is as usual in a
3224 separate file, and need not be compiled.
3233 In the case of subunits, only compile the parent unit. A single object
3234 file is generated for the entire subunit tree, which includes all the
3238 Compile child units independently of their parent units
3239 (though, of course, the spec of all the ancestor unit must be present in order
3240 to compile a child unit).
3245 Compile generic units in the same manner as any other units. The object
3246 files in this case are small dummy files that contain at most the
3247 flag used for elaboration checking. This is because GNAT always handles generic
3248 instantiation by means of macro expansion. However, it is still necessary to
3249 compile generic units, for dependency checking and elaboration purposes.
3252 The preceding rules describe the set of files that must be compiled to
3253 generate the object files for a program. Each object file has the same
3254 name as the corresponding source file, except that the extension is
3257 You may wish to compile other files for the purpose of checking their
3258 syntactic and semantic correctness. For example, in the case where a
3259 package has a separate spec and body, you would not normally compile the
3260 spec. However, it is convenient in practice to compile the spec to make
3261 sure it is error-free before compiling clients of this spec, because such
3262 compilations will fail if there is an error in the spec.
3264 GNAT provides an option for compiling such files purely for the
3265 purposes of checking correctness; such compilations are not required as
3266 part of the process of building a program. To compile a file in this
3267 checking mode, use the @code{-gnatc} switch.
3269 @node Source Dependencies,The Ada Library Information Files,Generating Object Files,The GNAT Compilation Model
3270 @anchor{gnat_ugn/the_gnat_compilation_model id32}@anchor{7c}@anchor{gnat_ugn/the_gnat_compilation_model source-dependencies}@anchor{41}
3271 @section Source Dependencies
3274 A given object file clearly depends on the source file which is compiled
3275 to produce it. Here we are using "depends" in the sense of a typical
3276 @code{make} utility; in other words, an object file depends on a source
3277 file if changes to the source file require the object file to be
3279 In addition to this basic dependency, a given object may depend on
3280 additional source files as follows:
3286 If a file being compiled @emph{with}s a unit @code{X}, the object file
3287 depends on the file containing the spec of unit @code{X}. This includes
3288 files that are @emph{with}ed implicitly either because they are parents
3289 of @emph{with}ed child units or they are run-time units required by the
3290 language constructs used in a particular unit.
3293 If a file being compiled instantiates a library level generic unit, the
3294 object file depends on both the spec and body files for this generic
3298 If a file being compiled instantiates a generic unit defined within a
3299 package, the object file depends on the body file for the package as
3300 well as the spec file.
3305 @geindex -gnatn switch
3311 If a file being compiled contains a call to a subprogram for which
3312 pragma @code{Inline} applies and inlining is activated with the
3313 @code{-gnatn} switch, the object file depends on the file containing the
3314 body of this subprogram as well as on the file containing the spec. Note
3315 that for inlining to actually occur as a result of the use of this switch,
3316 it is necessary to compile in optimizing mode.
3318 @geindex -gnatN switch
3320 The use of @code{-gnatN} activates inlining optimization
3321 that is performed by the front end of the compiler. This inlining does
3322 not require that the code generation be optimized. Like @code{-gnatn},
3323 the use of this switch generates additional dependencies.
3325 When using a gcc-based back end (in practice this means using any version
3326 of GNAT other than for the JVM, .NET or GNAAMP platforms), then the use of
3327 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
3328 Historically front end inlining was more extensive than the gcc back end
3329 inlining, but that is no longer the case.
3332 If an object file @code{O} depends on the proper body of a subunit through
3333 inlining or instantiation, it depends on the parent unit of the subunit.
3334 This means that any modification of the parent unit or one of its subunits
3335 affects the compilation of @code{O}.
3338 The object file for a parent unit depends on all its subunit body files.
3341 The previous two rules meant that for purposes of computing dependencies and
3342 recompilation, a body and all its subunits are treated as an indivisible whole.
3344 These rules are applied transitively: if unit @code{A} @emph{with}s
3345 unit @code{B}, whose elaboration calls an inlined procedure in package
3346 @code{C}, the object file for unit @code{A} will depend on the body of
3347 @code{C}, in file @code{c.adb}.
3349 The set of dependent files described by these rules includes all the
3350 files on which the unit is semantically dependent, as dictated by the
3351 Ada language standard. However, it is a superset of what the
3352 standard describes, because it includes generic, inline, and subunit
3355 An object file must be recreated by recompiling the corresponding source
3356 file if any of the source files on which it depends are modified. For
3357 example, if the @code{make} utility is used to control compilation,
3358 the rule for an Ada object file must mention all the source files on
3359 which the object file depends, according to the above definition.
3360 The determination of the necessary
3361 recompilations is done automatically when one uses @code{gnatmake}.
3364 @node The Ada Library Information Files,Binding an Ada Program,Source Dependencies,The GNAT Compilation Model
3365 @anchor{gnat_ugn/the_gnat_compilation_model id33}@anchor{7d}@anchor{gnat_ugn/the_gnat_compilation_model the-ada-library-information-files}@anchor{42}
3366 @section The Ada Library Information Files
3369 @geindex Ada Library Information files
3373 Each compilation actually generates two output files. The first of these
3374 is the normal object file that has a @code{.o} extension. The second is a
3375 text file containing full dependency information. It has the same
3376 name as the source file, but an @code{.ali} extension.
3377 This file is known as the Ada Library Information (@code{ALI}) file.
3378 The following information is contained in the @code{ALI} file.
3384 Version information (indicates which version of GNAT was used to compile
3385 the unit(s) in question)
3388 Main program information (including priority and time slice settings,
3389 as well as the wide character encoding used during compilation).
3392 List of arguments used in the @code{gcc} command for the compilation
3395 Attributes of the unit, including configuration pragmas used, an indication
3396 of whether the compilation was successful, exception model used etc.
3399 A list of relevant restrictions applying to the unit (used for consistency)
3403 Categorization information (e.g., use of pragma @code{Pure}).
3406 Information on all @emph{with}ed units, including presence of
3407 @code{Elaborate} or @code{Elaborate_All} pragmas.
3410 Information from any @code{Linker_Options} pragmas used in the unit
3413 Information on the use of @code{Body_Version} or @code{Version}
3414 attributes in the unit.
3417 Dependency information. This is a list of files, together with
3418 time stamp and checksum information. These are files on which
3419 the unit depends in the sense that recompilation is required
3420 if any of these units are modified.
3423 Cross-reference data. Contains information on all entities referenced
3424 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
3425 provide cross-reference information.
3428 For a full detailed description of the format of the @code{ALI} file,
3429 see the source of the body of unit @code{Lib.Writ}, contained in file
3430 @code{lib-writ.adb} in the GNAT compiler sources.
3432 @node Binding an Ada Program,GNAT and Libraries,The Ada Library Information Files,The GNAT Compilation Model
3433 @anchor{gnat_ugn/the_gnat_compilation_model id34}@anchor{7e}@anchor{gnat_ugn/the_gnat_compilation_model binding-an-ada-program}@anchor{43}
3434 @section Binding an Ada Program
3437 When using languages such as C and C++, once the source files have been
3438 compiled the only remaining step in building an executable program
3439 is linking the object modules together. This means that it is possible to
3440 link an inconsistent version of a program, in which two units have
3441 included different versions of the same header.
3443 The rules of Ada do not permit such an inconsistent program to be built.
3444 For example, if two clients have different versions of the same package,
3445 it is illegal to build a program containing these two clients.
3446 These rules are enforced by the GNAT binder, which also determines an
3447 elaboration order consistent with the Ada rules.
3449 The GNAT binder is run after all the object files for a program have
3450 been created. It is given the name of the main program unit, and from
3451 this it determines the set of units required by the program, by reading the
3452 corresponding ALI files. It generates error messages if the program is
3453 inconsistent or if no valid order of elaboration exists.
3455 If no errors are detected, the binder produces a main program, in Ada by
3456 default, that contains calls to the elaboration procedures of those
3457 compilation unit that require them, followed by
3458 a call to the main program. This Ada program is compiled to generate the
3459 object file for the main program. The name of
3460 the Ada file is @code{b~xxx}.adb` (with the corresponding spec
3461 @code{b~xxx}.ads`) where @code{xxx} is the name of the
3464 Finally, the linker is used to build the resulting executable program,
3465 using the object from the main program from the bind step as well as the
3466 object files for the Ada units of the program.
3468 @node GNAT and Libraries,Conditional Compilation,Binding an Ada Program,The GNAT Compilation Model
3469 @anchor{gnat_ugn/the_gnat_compilation_model gnat-and-libraries}@anchor{15}@anchor{gnat_ugn/the_gnat_compilation_model id35}@anchor{7f}
3470 @section GNAT and Libraries
3473 @geindex Library building and using
3475 This section describes how to build and use libraries with GNAT, and also shows
3476 how to recompile the GNAT run-time library. You should be familiar with the
3477 Project Manager facility (see the @emph{GNAT_Project_Manager} chapter of the
3478 @emph{GPRbuild User's Guide}) before reading this chapter.
3481 * Introduction to Libraries in GNAT::
3482 * General Ada Libraries::
3483 * Stand-alone Ada Libraries::
3484 * Rebuilding the GNAT Run-Time Library::
3488 @node Introduction to Libraries in GNAT,General Ada Libraries,,GNAT and Libraries
3489 @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-libraries-in-gnat}@anchor{80}@anchor{gnat_ugn/the_gnat_compilation_model id36}@anchor{81}
3490 @subsection Introduction to Libraries in GNAT
3493 A library is, conceptually, a collection of objects which does not have its
3494 own main thread of execution, but rather provides certain services to the
3495 applications that use it. A library can be either statically linked with the
3496 application, in which case its code is directly included in the application,
3497 or, on platforms that support it, be dynamically linked, in which case
3498 its code is shared by all applications making use of this library.
3500 GNAT supports both types of libraries.
3501 In the static case, the compiled code can be provided in different ways. The
3502 simplest approach is to provide directly the set of objects resulting from
3503 compilation of the library source files. Alternatively, you can group the
3504 objects into an archive using whatever commands are provided by the operating
3505 system. For the latter case, the objects are grouped into a shared library.
3507 In the GNAT environment, a library has three types of components:
3516 @code{ALI} files (see @ref{42,,The Ada Library Information Files}), and
3519 Object files, an archive or a shared library.
3522 A GNAT library may expose all its source files, which is useful for
3523 documentation purposes. Alternatively, it may expose only the units needed by
3524 an external user to make use of the library. That is to say, the specs
3525 reflecting the library services along with all the units needed to compile
3526 those specs, which can include generic bodies or any body implementing an
3527 inlined routine. In the case of @emph{stand-alone libraries} those exposed
3528 units are called @emph{interface units} (@ref{82,,Stand-alone Ada Libraries}).
3530 All compilation units comprising an application, including those in a library,
3531 need to be elaborated in an order partially defined by Ada's semantics. GNAT
3532 computes the elaboration order from the @code{ALI} files and this is why they
3533 constitute a mandatory part of GNAT libraries.
3534 @emph{Stand-alone libraries} are the exception to this rule because a specific
3535 library elaboration routine is produced independently of the application(s)
3538 @node General Ada Libraries,Stand-alone Ada Libraries,Introduction to Libraries in GNAT,GNAT and Libraries
3539 @anchor{gnat_ugn/the_gnat_compilation_model general-ada-libraries}@anchor{83}@anchor{gnat_ugn/the_gnat_compilation_model id37}@anchor{84}
3540 @subsection General Ada Libraries
3544 * Building a library::
3545 * Installing a library::
3550 @node Building a library,Installing a library,,General Ada Libraries
3551 @anchor{gnat_ugn/the_gnat_compilation_model building-a-library}@anchor{85}@anchor{gnat_ugn/the_gnat_compilation_model id38}@anchor{86}
3552 @subsubsection Building a library
3555 The easiest way to build a library is to use the Project Manager,
3556 which supports a special type of project called a @emph{Library Project}
3557 (see the @emph{Library Projects} section in the @emph{GNAT Project Manager}
3558 chapter of the @emph{GPRbuild User's Guide}).
3560 A project is considered a library project, when two project-level attributes
3561 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
3562 control different aspects of library configuration, additional optional
3563 project-level attributes can be specified:
3572 @item @code{Library_Kind}
3574 This attribute controls whether the library is to be static or dynamic
3581 @item @code{Library_Version}
3583 This attribute specifies the library version; this value is used
3584 during dynamic linking of shared libraries to determine if the currently
3585 installed versions of the binaries are compatible.
3589 @code{Library_Options}
3595 @item @code{Library_GCC}
3597 These attributes specify additional low-level options to be used during
3598 library generation, and redefine the actual application used to generate
3603 The GNAT Project Manager takes full care of the library maintenance task,
3604 including recompilation of the source files for which objects do not exist
3605 or are not up to date, assembly of the library archive, and installation of
3606 the library (i.e., copying associated source, object and @code{ALI} files
3607 to the specified location).
3609 Here is a simple library project file:
3613 for Source_Dirs use ("src1", "src2");
3614 for Object_Dir use "obj";
3615 for Library_Name use "mylib";
3616 for Library_Dir use "lib";
3617 for Library_Kind use "dynamic";
3621 and the compilation command to build and install the library:
3627 It is not entirely trivial to perform manually all the steps required to
3628 produce a library. We recommend that you use the GNAT Project Manager
3629 for this task. In special cases where this is not desired, the necessary
3630 steps are discussed below.
3632 There are various possibilities for compiling the units that make up the
3633 library: for example with a Makefile (@ref{1f,,Using the GNU make Utility}) or
3634 with a conventional script. For simple libraries, it is also possible to create
3635 a dummy main program which depends upon all the packages that comprise the
3636 interface of the library. This dummy main program can then be given to
3637 @code{gnatmake}, which will ensure that all necessary objects are built.
3639 After this task is accomplished, you should follow the standard procedure
3640 of the underlying operating system to produce the static or shared library.
3642 Here is an example of such a dummy program:
3645 with My_Lib.Service1;
3646 with My_Lib.Service2;
3647 with My_Lib.Service3;
3648 procedure My_Lib_Dummy is
3654 Here are the generic commands that will build an archive or a shared library.
3657 # compiling the library
3658 $ gnatmake -c my_lib_dummy.adb
3660 # we don't need the dummy object itself
3661 $ rm my_lib_dummy.o my_lib_dummy.ali
3663 # create an archive with the remaining objects
3664 $ ar rc libmy_lib.a *.o
3665 # some systems may require "ranlib" to be run as well
3667 # or create a shared library
3668 $ gcc -shared -o libmy_lib.so *.o
3669 # some systems may require the code to have been compiled with -fPIC
3671 # remove the object files that are now in the library
3674 # Make the ALI files read-only so that gnatmake will not try to
3675 # regenerate the objects that are in the library
3679 Please note that the library must have a name of the form @code{lib@emph{xxx}.a}
3680 or @code{lib@emph{xxx}.so} (or @code{lib@emph{xxx}.dll} on Windows) in order to
3681 be accessed by the directive @code{-l@emph{xxx}} at link time.
3683 @node Installing a library,Using a library,Building a library,General Ada Libraries
3684 @anchor{gnat_ugn/the_gnat_compilation_model installing-a-library}@anchor{87}@anchor{gnat_ugn/the_gnat_compilation_model id39}@anchor{88}
3685 @subsubsection Installing a library
3688 @geindex ADA_PROJECT_PATH
3690 @geindex GPR_PROJECT_PATH
3692 If you use project files, library installation is part of the library build
3693 process (see the @emph{Installing a Library with Project Files} section of the
3694 @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}).
3696 When project files are not an option, it is also possible, but not recommended,
3697 to install the library so that the sources needed to use the library are on the
3698 Ada source path and the ALI files & libraries be on the Ada Object path (see
3699 @ref{89,,Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
3700 administrator can place general-purpose libraries in the default compiler
3701 paths, by specifying the libraries' location in the configuration files
3702 @code{ada_source_path} and @code{ada_object_path}. These configuration files
3703 must be located in the GNAT installation tree at the same place as the gcc spec
3704 file. The location of the gcc spec file can be determined as follows:
3710 The configuration files mentioned above have a simple format: each line
3711 must contain one unique directory name.
3712 Those names are added to the corresponding path
3713 in their order of appearance in the file. The names can be either absolute
3714 or relative; in the latter case, they are relative to where theses files
3717 The files @code{ada_source_path} and @code{ada_object_path} might not be
3719 GNAT installation, in which case, GNAT will look for its run-time library in
3720 the directories @code{adainclude} (for the sources) and @code{adalib} (for the
3721 objects and @code{ALI} files). When the files exist, the compiler does not
3722 look in @code{adainclude} and @code{adalib}, and thus the
3723 @code{ada_source_path} file
3724 must contain the location for the GNAT run-time sources (which can simply
3725 be @code{adainclude}). In the same way, the @code{ada_object_path} file must
3726 contain the location for the GNAT run-time objects (which can simply
3729 You can also specify a new default path to the run-time library at compilation
3730 time with the switch @code{--RTS=rts-path}. You can thus choose / change
3731 the run-time library you want your program to be compiled with. This switch is
3732 recognized by @code{gcc}, @code{gnatmake}, @code{gnatbind},
3733 @code{gnatls}, @code{gnatfind} and @code{gnatxref}.
3735 It is possible to install a library before or after the standard GNAT
3736 library, by reordering the lines in the configuration files. In general, a
3737 library must be installed before the GNAT library if it redefines
3740 @node Using a library,,Installing a library,General Ada Libraries
3741 @anchor{gnat_ugn/the_gnat_compilation_model using-a-library}@anchor{8a}@anchor{gnat_ugn/the_gnat_compilation_model id40}@anchor{8b}
3742 @subsubsection Using a library
3745 Once again, the project facility greatly simplifies the use of
3746 libraries. In this context, using a library is just a matter of adding a
3747 @emph{with} clause in the user project. For instance, to make use of the
3748 library @code{My_Lib} shown in examples in earlier sections, you can
3758 Even if you have a third-party, non-Ada library, you can still use GNAT's
3759 Project Manager facility to provide a wrapper for it. For example, the
3760 following project, when @emph{with}ed by your main project, will link with the
3761 third-party library @code{liba.a}:
3765 for Externally_Built use "true";
3766 for Source_Files use ();
3767 for Library_Dir use "lib";
3768 for Library_Name use "a";
3769 for Library_Kind use "static";
3773 This is an alternative to the use of @code{pragma Linker_Options}. It is
3774 especially interesting in the context of systems with several interdependent
3775 static libraries where finding a proper linker order is not easy and best be
3776 left to the tools having visibility over project dependence information.
3778 In order to use an Ada library manually, you need to make sure that this
3779 library is on both your source and object path
3780 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}
3781 and @ref{8c,,Search Paths for gnatbind}). Furthermore, when the objects are grouped
3782 in an archive or a shared library, you need to specify the desired
3783 library at link time.
3785 For example, you can use the library @code{mylib} installed in
3786 @code{/dir/my_lib_src} and @code{/dir/my_lib_obj} with the following commands:
3789 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\
3793 This can be expressed more simply:
3799 when the following conditions are met:
3805 @code{/dir/my_lib_src} has been added by the user to the environment
3807 @geindex ADA_INCLUDE_PATH
3808 @geindex environment variable; ADA_INCLUDE_PATH
3809 @code{ADA_INCLUDE_PATH}, or by the administrator to the file
3810 @code{ada_source_path}
3813 @code{/dir/my_lib_obj} has been added by the user to the environment
3815 @geindex ADA_OBJECTS_PATH
3816 @geindex environment variable; ADA_OBJECTS_PATH
3817 @code{ADA_OBJECTS_PATH}, or by the administrator to the file
3818 @code{ada_object_path}
3821 a pragma @code{Linker_Options} has been added to one of the sources.
3825 pragma Linker_Options ("-lmy_lib");
3829 Note that you may also load a library dynamically at
3830 run time given its filename, as illustrated in the GNAT @code{plugins} example
3831 in the directory @code{share/examples/gnat/plugins} within the GNAT
3834 @node Stand-alone Ada Libraries,Rebuilding the GNAT Run-Time Library,General Ada Libraries,GNAT and Libraries
3835 @anchor{gnat_ugn/the_gnat_compilation_model stand-alone-ada-libraries}@anchor{82}@anchor{gnat_ugn/the_gnat_compilation_model id41}@anchor{8d}
3836 @subsection Stand-alone Ada Libraries
3839 @geindex Stand-alone libraries
3842 * Introduction to Stand-alone Libraries::
3843 * Building a Stand-alone Library::
3844 * Creating a Stand-alone Library to be used in a non-Ada context::
3845 * Restrictions in Stand-alone Libraries::
3849 @node Introduction to Stand-alone Libraries,Building a Stand-alone Library,,Stand-alone Ada Libraries
3850 @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-stand-alone-libraries}@anchor{8e}@anchor{gnat_ugn/the_gnat_compilation_model id42}@anchor{8f}
3851 @subsubsection Introduction to Stand-alone Libraries
3854 A Stand-alone Library (abbreviated 'SAL') is a library that contains the
3856 elaborate the Ada units that are included in the library. In contrast with
3857 an ordinary library, which consists of all sources, objects and @code{ALI}
3859 library, a SAL may specify a restricted subset of compilation units
3860 to serve as a library interface. In this case, the fully
3861 self-sufficient set of files will normally consist of an objects
3862 archive, the sources of interface units' specs, and the @code{ALI}
3863 files of interface units.
3864 If an interface spec contains a generic unit or an inlined subprogram,
3866 source must also be provided; if the units that must be provided in the source
3867 form depend on other units, the source and @code{ALI} files of those must
3870 The main purpose of a SAL is to minimize the recompilation overhead of client
3871 applications when a new version of the library is installed. Specifically,
3872 if the interface sources have not changed, client applications do not need to
3873 be recompiled. If, furthermore, a SAL is provided in the shared form and its
3874 version, controlled by @code{Library_Version} attribute, is not changed,
3875 then the clients do not need to be relinked.
3877 SALs also allow the library providers to minimize the amount of library source
3878 text exposed to the clients. Such 'information hiding' might be useful or
3879 necessary for various reasons.
3881 Stand-alone libraries are also well suited to be used in an executable whose
3882 main routine is not written in Ada.
3884 @node Building a Stand-alone Library,Creating a Stand-alone Library to be used in a non-Ada context,Introduction to Stand-alone Libraries,Stand-alone Ada Libraries
3885 @anchor{gnat_ugn/the_gnat_compilation_model id43}@anchor{90}@anchor{gnat_ugn/the_gnat_compilation_model building-a-stand-alone-library}@anchor{91}
3886 @subsubsection Building a Stand-alone Library
3889 GNAT's Project facility provides a simple way of building and installing
3890 stand-alone libraries; see the @emph{Stand-alone Library Projects} section
3891 in the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}.
3892 To be a Stand-alone Library Project, in addition to the two attributes
3893 that make a project a Library Project (@code{Library_Name} and
3894 @code{Library_Dir}; see the @emph{Library Projects} section in the
3895 @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}),
3896 the attribute @code{Library_Interface} must be defined. For example:
3899 for Library_Dir use "lib_dir";
3900 for Library_Name use "dummy";
3901 for Library_Interface use ("int1", "int1.child");
3904 Attribute @code{Library_Interface} has a non-empty string list value,
3905 each string in the list designating a unit contained in an immediate source
3906 of the project file.
3908 When a Stand-alone Library is built, first the binder is invoked to build
3909 a package whose name depends on the library name
3910 (@code{b~dummy.ads/b} in the example above).
3911 This binder-generated package includes initialization and
3912 finalization procedures whose
3913 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
3915 above). The object corresponding to this package is included in the library.
3917 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
3918 calling of these procedures if a static SAL is built, or if a shared SAL
3920 with the project-level attribute @code{Library_Auto_Init} set to
3923 For a Stand-Alone Library, only the @code{ALI} files of the Interface Units
3924 (those that are listed in attribute @code{Library_Interface}) are copied to
3925 the Library Directory. As a consequence, only the Interface Units may be
3926 imported from Ada units outside of the library. If other units are imported,
3927 the binding phase will fail.
3929 It is also possible to build an encapsulated library where not only
3930 the code to elaborate and finalize the library is embedded but also
3931 ensuring that the library is linked only against static
3932 libraries. So an encapsulated library only depends on system
3933 libraries, all other code, including the GNAT runtime, is embedded. To
3934 build an encapsulated library the attribute
3935 @code{Library_Standalone} must be set to @code{encapsulated}:
3938 for Library_Dir use "lib_dir";
3939 for Library_Name use "dummy";
3940 for Library_Kind use "dynamic";
3941 for Library_Interface use ("int1", "int1.child");
3942 for Library_Standalone use "encapsulated";
3945 The default value for this attribute is @code{standard} in which case
3946 a stand-alone library is built.
3948 The attribute @code{Library_Src_Dir} may be specified for a
3949 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
3950 single string value. Its value must be the path (absolute or relative to the
3951 project directory) of an existing directory. This directory cannot be the
3952 object directory or one of the source directories, but it can be the same as
3953 the library directory. The sources of the Interface
3954 Units of the library that are needed by an Ada client of the library will be
3955 copied to the designated directory, called the Interface Copy directory.
3956 These sources include the specs of the Interface Units, but they may also
3957 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
3958 are used, or when there is a generic unit in the spec. Before the sources
3959 are copied to the Interface Copy directory, an attempt is made to delete all
3960 files in the Interface Copy directory.
3962 Building stand-alone libraries by hand is somewhat tedious, but for those
3963 occasions when it is necessary here are the steps that you need to perform:
3969 Compile all library sources.
3972 Invoke the binder with the switch @code{-n} (No Ada main program),
3973 with all the @code{ALI} files of the interfaces, and
3974 with the switch @code{-L} to give specific names to the @code{init}
3975 and @code{final} procedures. For example:
3978 $ gnatbind -n int1.ali int2.ali -Lsal1
3982 Compile the binder generated file:
3989 Link the dynamic library with all the necessary object files,
3990 indicating to the linker the names of the @code{init} (and possibly
3991 @code{final}) procedures for automatic initialization (and finalization).
3992 The built library should be placed in a directory different from
3993 the object directory.
3996 Copy the @code{ALI} files of the interface to the library directory,
3997 add in this copy an indication that it is an interface to a SAL
3998 (i.e., add a word @code{SL} on the line in the @code{ALI} file that starts
3999 with letter 'P') and make the modified copy of the @code{ALI} file
4003 Using SALs is not different from using other libraries
4004 (see @ref{8a,,Using a library}).
4006 @node Creating a Stand-alone Library to be used in a non-Ada context,Restrictions in Stand-alone Libraries,Building a Stand-alone Library,Stand-alone Ada Libraries
4007 @anchor{gnat_ugn/the_gnat_compilation_model creating-a-stand-alone-library-to-be-used-in-a-non-ada-context}@anchor{92}@anchor{gnat_ugn/the_gnat_compilation_model id44}@anchor{93}
4008 @subsubsection Creating a Stand-alone Library to be used in a non-Ada context
4011 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
4014 The only extra step required is to ensure that library interface subprograms
4015 are compatible with the main program, by means of @code{pragma Export}
4016 or @code{pragma Convention}.
4018 Here is an example of simple library interface for use with C main program:
4021 package My_Package is
4023 procedure Do_Something;
4024 pragma Export (C, Do_Something, "do_something");
4026 procedure Do_Something_Else;
4027 pragma Export (C, Do_Something_Else, "do_something_else");
4032 On the foreign language side, you must provide a 'foreign' view of the
4033 library interface; remember that it should contain elaboration routines in
4034 addition to interface subprograms.
4036 The example below shows the content of @code{mylib_interface.h} (note
4037 that there is no rule for the naming of this file, any name can be used)
4040 /* the library elaboration procedure */
4041 extern void mylibinit (void);
4043 /* the library finalization procedure */
4044 extern void mylibfinal (void);
4046 /* the interface exported by the library */
4047 extern void do_something (void);
4048 extern void do_something_else (void);
4051 Libraries built as explained above can be used from any program, provided
4052 that the elaboration procedures (named @code{mylibinit} in the previous
4053 example) are called before the library services are used. Any number of
4054 libraries can be used simultaneously, as long as the elaboration
4055 procedure of each library is called.
4057 Below is an example of a C program that uses the @code{mylib} library.
4060 #include "mylib_interface.h"
4065 /* First, elaborate the library before using it */
4068 /* Main program, using the library exported entities */
4070 do_something_else ();
4072 /* Library finalization at the end of the program */
4078 Note that invoking any library finalization procedure generated by
4079 @code{gnatbind} shuts down the Ada run-time environment.
4081 finalization of all Ada libraries must be performed at the end of the program.
4082 No call to these libraries or to the Ada run-time library should be made
4083 after the finalization phase.
4085 Note also that special care must be taken with multi-tasks
4086 applications. The initialization and finalization routines are not
4087 protected against concurrent access. If such requirement is needed it
4088 must be ensured at the application level using a specific operating
4089 system services like a mutex or a critical-section.
4091 @node Restrictions in Stand-alone Libraries,,Creating a Stand-alone Library to be used in a non-Ada context,Stand-alone Ada Libraries
4092 @anchor{gnat_ugn/the_gnat_compilation_model id45}@anchor{94}@anchor{gnat_ugn/the_gnat_compilation_model restrictions-in-stand-alone-libraries}@anchor{95}
4093 @subsubsection Restrictions in Stand-alone Libraries
4096 The pragmas listed below should be used with caution inside libraries,
4097 as they can create incompatibilities with other Ada libraries:
4103 pragma @code{Locking_Policy}
4106 pragma @code{Partition_Elaboration_Policy}
4109 pragma @code{Queuing_Policy}
4112 pragma @code{Task_Dispatching_Policy}
4115 pragma @code{Unreserve_All_Interrupts}
4118 When using a library that contains such pragmas, the user must make sure
4119 that all libraries use the same pragmas with the same values. Otherwise,
4120 @code{Program_Error} will
4121 be raised during the elaboration of the conflicting
4122 libraries. The usage of these pragmas and its consequences for the user
4123 should therefore be well documented.
4125 Similarly, the traceback in the exception occurrence mechanism should be
4126 enabled or disabled in a consistent manner across all libraries.
4127 Otherwise, Program_Error will be raised during the elaboration of the
4128 conflicting libraries.
4130 If the @code{Version} or @code{Body_Version}
4131 attributes are used inside a library, then you need to
4132 perform a @code{gnatbind} step that specifies all @code{ALI} files in all
4133 libraries, so that version identifiers can be properly computed.
4134 In practice these attributes are rarely used, so this is unlikely
4135 to be a consideration.
4137 @node Rebuilding the GNAT Run-Time Library,,Stand-alone Ada Libraries,GNAT and Libraries
4138 @anchor{gnat_ugn/the_gnat_compilation_model id46}@anchor{96}@anchor{gnat_ugn/the_gnat_compilation_model rebuilding-the-gnat-run-time-library}@anchor{97}
4139 @subsection Rebuilding the GNAT Run-Time Library
4142 @geindex GNAT Run-Time Library
4145 @geindex Building the GNAT Run-Time Library
4147 @geindex Rebuilding the GNAT Run-Time Library
4149 @geindex Run-Time Library
4152 It may be useful to recompile the GNAT library in various contexts, the
4153 most important one being the use of partition-wide configuration pragmas
4154 such as @code{Normalize_Scalars}. A special Makefile called
4155 @code{Makefile.adalib} is provided to that effect and can be found in
4156 the directory containing the GNAT library. The location of this
4157 directory depends on the way the GNAT environment has been installed and can
4158 be determined by means of the command:
4164 The last entry in the object search path usually contains the
4165 gnat library. This Makefile contains its own documentation and in
4166 particular the set of instructions needed to rebuild a new library and
4169 @geindex Conditional compilation
4171 @node Conditional Compilation,Mixed Language Programming,GNAT and Libraries,The GNAT Compilation Model
4172 @anchor{gnat_ugn/the_gnat_compilation_model id47}@anchor{98}@anchor{gnat_ugn/the_gnat_compilation_model conditional-compilation}@anchor{16}
4173 @section Conditional Compilation
4176 This section presents some guidelines for modeling conditional compilation in Ada and describes the
4177 gnatprep preprocessor utility.
4179 @geindex Conditional compilation
4182 * Modeling Conditional Compilation in Ada::
4183 * Preprocessing with gnatprep::
4184 * Integrated Preprocessing::
4188 @node Modeling Conditional Compilation in Ada,Preprocessing with gnatprep,,Conditional Compilation
4189 @anchor{gnat_ugn/the_gnat_compilation_model modeling-conditional-compilation-in-ada}@anchor{99}@anchor{gnat_ugn/the_gnat_compilation_model id48}@anchor{9a}
4190 @subsection Modeling Conditional Compilation in Ada
4193 It is often necessary to arrange for a single source program
4194 to serve multiple purposes, where it is compiled in different
4195 ways to achieve these different goals. Some examples of the
4196 need for this feature are
4202 Adapting a program to a different hardware environment
4205 Adapting a program to a different target architecture
4208 Turning debugging features on and off
4211 Arranging for a program to compile with different compilers
4214 In C, or C++, the typical approach would be to use the preprocessor
4215 that is defined as part of the language. The Ada language does not
4216 contain such a feature. This is not an oversight, but rather a very
4217 deliberate design decision, based on the experience that overuse of
4218 the preprocessing features in C and C++ can result in programs that
4219 are extremely difficult to maintain. For example, if we have ten
4220 switches that can be on or off, this means that there are a thousand
4221 separate programs, any one of which might not even be syntactically
4222 correct, and even if syntactically correct, the resulting program
4223 might not work correctly. Testing all combinations can quickly become
4226 Nevertheless, the need to tailor programs certainly exists, and in
4227 this section we will discuss how this can
4228 be achieved using Ada in general, and GNAT in particular.
4231 * Use of Boolean Constants::
4232 * Debugging - A Special Case::
4233 * Conditionalizing Declarations::
4234 * Use of Alternative Implementations::
4239 @node Use of Boolean Constants,Debugging - A Special Case,,Modeling Conditional Compilation in Ada
4240 @anchor{gnat_ugn/the_gnat_compilation_model id49}@anchor{9b}@anchor{gnat_ugn/the_gnat_compilation_model use-of-boolean-constants}@anchor{9c}
4241 @subsubsection Use of Boolean Constants
4244 In the case where the difference is simply which code
4245 sequence is executed, the cleanest solution is to use Boolean
4246 constants to control which code is executed.
4249 FP_Initialize_Required : constant Boolean := True;
4251 if FP_Initialize_Required then
4256 Not only will the code inside the @code{if} statement not be executed if
4257 the constant Boolean is @code{False}, but it will also be completely
4258 deleted from the program.
4259 However, the code is only deleted after the @code{if} statement
4260 has been checked for syntactic and semantic correctness.
4261 (In contrast, with preprocessors the code is deleted before the
4262 compiler ever gets to see it, so it is not checked until the switch
4265 @geindex Preprocessors (contrasted with conditional compilation)
4267 Typically the Boolean constants will be in a separate package,
4272 FP_Initialize_Required : constant Boolean := True;
4273 Reset_Available : constant Boolean := False;
4278 The @code{Config} package exists in multiple forms for the various targets,
4279 with an appropriate script selecting the version of @code{Config} needed.
4280 Then any other unit requiring conditional compilation can do a @emph{with}
4281 of @code{Config} to make the constants visible.
4283 @node Debugging - A Special Case,Conditionalizing Declarations,Use of Boolean Constants,Modeling Conditional Compilation in Ada
4284 @anchor{gnat_ugn/the_gnat_compilation_model debugging-a-special-case}@anchor{9d}@anchor{gnat_ugn/the_gnat_compilation_model id50}@anchor{9e}
4285 @subsubsection Debugging - A Special Case
4288 A common use of conditional code is to execute statements (for example
4289 dynamic checks, or output of intermediate results) under control of a
4290 debug switch, so that the debugging behavior can be turned on and off.
4291 This can be done using a Boolean constant to control whether the code
4296 Put_Line ("got to the first stage!");
4303 if Debugging and then Temperature > 999.0 then
4304 raise Temperature_Crazy;
4308 @geindex pragma Assert
4310 Since this is a common case, there are special features to deal with
4311 this in a convenient manner. For the case of tests, Ada 2005 has added
4312 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
4313 on the @code{Assert} pragma that has always been available in GNAT, so this
4314 feature may be used with GNAT even if you are not using Ada 2005 features.
4315 The use of pragma @code{Assert} is described in the
4316 @cite{GNAT_Reference_Manual}, but as an
4317 example, the last test could be written:
4320 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
4326 pragma Assert (Temperature <= 999.0);
4329 In both cases, if assertions are active and the temperature is excessive,
4330 the exception @code{Assert_Failure} will be raised, with the given string in
4331 the first case or a string indicating the location of the pragma in the second
4332 case used as the exception message.
4334 @geindex pragma Assertion_Policy
4336 You can turn assertions on and off by using the @code{Assertion_Policy}
4339 @geindex -gnata switch
4341 This is an Ada 2005 pragma which is implemented in all modes by
4342 GNAT. Alternatively, you can use the @code{-gnata} switch
4343 to enable assertions from the command line, which applies to
4344 all versions of Ada.
4346 @geindex pragma Debug
4348 For the example above with the @code{Put_Line}, the GNAT-specific pragma
4349 @code{Debug} can be used:
4352 pragma Debug (Put_Line ("got to the first stage!"));
4355 If debug pragmas are enabled, the argument, which must be of the form of
4356 a procedure call, is executed (in this case, @code{Put_Line} will be called).
4357 Only one call can be present, but of course a special debugging procedure
4358 containing any code you like can be included in the program and then
4359 called in a pragma @code{Debug} argument as needed.
4361 One advantage of pragma @code{Debug} over the @code{if Debugging then}
4362 construct is that pragma @code{Debug} can appear in declarative contexts,
4363 such as at the very beginning of a procedure, before local declarations have
4366 @geindex pragma Debug_Policy
4368 Debug pragmas are enabled using either the @code{-gnata} switch that also
4369 controls assertions, or with a separate Debug_Policy pragma.
4371 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
4372 in Ada 95 and Ada 83 programs as well), and is analogous to
4373 pragma @code{Assertion_Policy} to control assertions.
4375 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
4376 and thus they can appear in @code{gnat.adc} if you are not using a
4377 project file, or in the file designated to contain configuration pragmas
4379 They then apply to all subsequent compilations. In practice the use of
4380 the @code{-gnata} switch is often the most convenient method of controlling
4381 the status of these pragmas.
4383 Note that a pragma is not a statement, so in contexts where a statement
4384 sequence is required, you can't just write a pragma on its own. You have
4385 to add a @code{null} statement.
4389 ... -- some statements
4391 pragma Assert (Num_Cases < 10);
4396 @node Conditionalizing Declarations,Use of Alternative Implementations,Debugging - A Special Case,Modeling Conditional Compilation in Ada
4397 @anchor{gnat_ugn/the_gnat_compilation_model conditionalizing-declarations}@anchor{9f}@anchor{gnat_ugn/the_gnat_compilation_model id51}@anchor{a0}
4398 @subsubsection Conditionalizing Declarations
4401 In some cases it may be necessary to conditionalize declarations to meet
4402 different requirements. For example we might want a bit string whose length
4403 is set to meet some hardware message requirement.
4405 This may be possible using declare blocks controlled
4406 by conditional constants:
4409 if Small_Machine then
4411 X : Bit_String (1 .. 10);
4417 X : Large_Bit_String (1 .. 1000);
4424 Note that in this approach, both declarations are analyzed by the
4425 compiler so this can only be used where both declarations are legal,
4426 even though one of them will not be used.
4428 Another approach is to define integer constants, e.g., @code{Bits_Per_Word},
4429 or Boolean constants, e.g., @code{Little_Endian}, and then write declarations
4430 that are parameterized by these constants. For example
4434 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
4438 If @code{Bits_Per_Word} is set to 32, this generates either
4442 Field1 at 0 range 0 .. 32;
4446 for the big endian case, or
4450 Field1 at 0 range 10 .. 32;
4454 for the little endian case. Since a powerful subset of Ada expression
4455 notation is usable for creating static constants, clever use of this
4456 feature can often solve quite difficult problems in conditionalizing
4457 compilation (note incidentally that in Ada 95, the little endian
4458 constant was introduced as @code{System.Default_Bit_Order}, so you do not
4459 need to define this one yourself).
4461 @node Use of Alternative Implementations,Preprocessing,Conditionalizing Declarations,Modeling Conditional Compilation in Ada
4462 @anchor{gnat_ugn/the_gnat_compilation_model use-of-alternative-implementations}@anchor{a1}@anchor{gnat_ugn/the_gnat_compilation_model id52}@anchor{a2}
4463 @subsubsection Use of Alternative Implementations
4466 In some cases, none of the approaches described above are adequate. This
4467 can occur for example if the set of declarations required is radically
4468 different for two different configurations.
4470 In this situation, the official Ada way of dealing with conditionalizing
4471 such code is to write separate units for the different cases. As long as
4472 this does not result in excessive duplication of code, this can be done
4473 without creating maintenance problems. The approach is to share common
4474 code as far as possible, and then isolate the code and declarations
4475 that are different. Subunits are often a convenient method for breaking
4476 out a piece of a unit that is to be conditionalized, with separate files
4477 for different versions of the subunit for different targets, where the
4478 build script selects the right one to give to the compiler.
4480 @geindex Subunits (and conditional compilation)
4482 As an example, consider a situation where a new feature in Ada 2005
4483 allows something to be done in a really nice way. But your code must be able
4484 to compile with an Ada 95 compiler. Conceptually you want to say:
4488 ... neat Ada 2005 code
4490 ... not quite as neat Ada 95 code
4494 where @code{Ada_2005} is a Boolean constant.
4496 But this won't work when @code{Ada_2005} is set to @code{False},
4497 since the @code{then} clause will be illegal for an Ada 95 compiler.
4498 (Recall that although such unreachable code would eventually be deleted
4499 by the compiler, it still needs to be legal. If it uses features
4500 introduced in Ada 2005, it will be illegal in Ada 95.)
4505 procedure Insert is separate;
4508 Then we have two files for the subunit @code{Insert}, with the two sets of
4510 If the package containing this is called @code{File_Queries}, then we might
4517 @code{file_queries-insert-2005.adb}
4520 @code{file_queries-insert-95.adb}
4523 and the build script renames the appropriate file to @code{file_queries-insert.adb} and then carries out the compilation.
4525 This can also be done with project files' naming schemes. For example:
4528 for body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
4531 Note also that with project files it is desirable to use a different extension
4532 than @code{ads} / @code{adb} for alternative versions. Otherwise a naming
4533 conflict may arise through another commonly used feature: to declare as part
4534 of the project a set of directories containing all the sources obeying the
4535 default naming scheme.
4537 The use of alternative units is certainly feasible in all situations,
4538 and for example the Ada part of the GNAT run-time is conditionalized
4539 based on the target architecture using this approach. As a specific example,
4540 consider the implementation of the AST feature in VMS. There is one
4541 spec: @code{s-asthan.ads} which is the same for all architectures, and three
4551 @item @code{s-asthan.adb}
4553 used for all non-VMS operating systems
4560 @item @code{s-asthan-vms-alpha.adb}
4562 used for VMS on the Alpha
4569 @item @code{s-asthan-vms-ia64.adb}
4571 used for VMS on the ia64
4575 The dummy version @code{s-asthan.adb} simply raises exceptions noting that
4576 this operating system feature is not available, and the two remaining
4577 versions interface with the corresponding versions of VMS to provide
4578 VMS-compatible AST handling. The GNAT build script knows the architecture
4579 and operating system, and automatically selects the right version,
4580 renaming it if necessary to @code{s-asthan.adb} before the run-time build.
4582 Another style for arranging alternative implementations is through Ada's
4583 access-to-subprogram facility.
4584 In case some functionality is to be conditionally included,
4585 you can declare an access-to-procedure variable @code{Ref} that is initialized
4586 to designate a 'do nothing' procedure, and then invoke @code{Ref.all}
4588 In some library package, set @code{Ref} to @code{Proc'Access} for some
4589 procedure @code{Proc} that performs the relevant processing.
4590 The initialization only occurs if the library package is included in the
4592 The same idea can also be implemented using tagged types and dispatching
4595 @node Preprocessing,,Use of Alternative Implementations,Modeling Conditional Compilation in Ada
4596 @anchor{gnat_ugn/the_gnat_compilation_model preprocessing}@anchor{a3}@anchor{gnat_ugn/the_gnat_compilation_model id53}@anchor{a4}
4597 @subsubsection Preprocessing
4600 @geindex Preprocessing
4602 Although it is quite possible to conditionalize code without the use of
4603 C-style preprocessing, as described earlier in this section, it is
4604 nevertheless convenient in some cases to use the C approach. Moreover,
4605 older Ada compilers have often provided some preprocessing capability,
4606 so legacy code may depend on this approach, even though it is not
4609 To accommodate such use, GNAT provides a preprocessor (modeled to a large
4610 extent on the various preprocessors that have been used
4611 with legacy code on other compilers, to enable easier transition).
4615 The preprocessor may be used in two separate modes. It can be used quite
4616 separately from the compiler, to generate a separate output source file
4617 that is then fed to the compiler as a separate step. This is the
4618 @code{gnatprep} utility, whose use is fully described in
4619 @ref{17,,Preprocessing with gnatprep}.
4621 The preprocessing language allows such constructs as
4624 #if DEBUG or else (PRIORITY > 4) then
4625 sequence of declarations
4627 completely different sequence of declarations
4631 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
4632 defined either on the command line or in a separate file.
4634 The other way of running the preprocessor is even closer to the C style and
4635 often more convenient. In this approach the preprocessing is integrated into
4636 the compilation process. The compiler is given the preprocessor input which
4637 includes @code{#if} lines etc, and then the compiler carries out the
4638 preprocessing internally and processes the resulting output.
4639 For more details on this approach, see @ref{18,,Integrated Preprocessing}.
4641 @node Preprocessing with gnatprep,Integrated Preprocessing,Modeling Conditional Compilation in Ada,Conditional Compilation
4642 @anchor{gnat_ugn/the_gnat_compilation_model id54}@anchor{a5}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-with-gnatprep}@anchor{17}
4643 @subsection Preprocessing with @code{gnatprep}
4648 @geindex Preprocessing (gnatprep)
4650 This section discusses how to use GNAT's @code{gnatprep} utility for simple
4652 Although designed for use with GNAT, @code{gnatprep} does not depend on any
4653 special GNAT features.
4654 For further discussion of conditional compilation in general, see
4655 @ref{16,,Conditional Compilation}.
4658 * Preprocessing Symbols::
4660 * Switches for gnatprep::
4661 * Form of Definitions File::
4662 * Form of Input Text for gnatprep::
4666 @node Preprocessing Symbols,Using gnatprep,,Preprocessing with gnatprep
4667 @anchor{gnat_ugn/the_gnat_compilation_model id55}@anchor{a6}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-symbols}@anchor{a7}
4668 @subsubsection Preprocessing Symbols
4671 Preprocessing symbols are defined in @emph{definition files} and referenced in the
4672 sources to be preprocessed. A preprocessing symbol is an identifier, following
4673 normal Ada (case-insensitive) rules for its syntax, with the restriction that
4674 all characters need to be in the ASCII set (no accented letters).
4676 @node Using gnatprep,Switches for gnatprep,Preprocessing Symbols,Preprocessing with gnatprep
4677 @anchor{gnat_ugn/the_gnat_compilation_model using-gnatprep}@anchor{a8}@anchor{gnat_ugn/the_gnat_compilation_model id56}@anchor{a9}
4678 @subsubsection Using @code{gnatprep}
4681 To call @code{gnatprep} use:
4684 $ gnatprep [ switches ] infile outfile [ deffile ]
4696 @item @emph{switches}
4698 is an optional sequence of switches as described in the next section.
4707 is the full name of the input file, which is an Ada source
4708 file containing preprocessor directives.
4715 @item @emph{outfile}
4717 is the full name of the output file, which is an Ada source
4718 in standard Ada form. When used with GNAT, this file name will
4719 normally have an @code{ads} or @code{adb} suffix.
4726 @item @code{deffile}
4728 is the full name of a text file containing definitions of
4729 preprocessing symbols to be referenced by the preprocessor. This argument is
4730 optional, and can be replaced by the use of the @code{-D} switch.
4734 @node Switches for gnatprep,Form of Definitions File,Using gnatprep,Preprocessing with gnatprep
4735 @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatprep}@anchor{aa}@anchor{gnat_ugn/the_gnat_compilation_model id57}@anchor{ab}
4736 @subsubsection Switches for @code{gnatprep}
4739 @geindex --version (gnatprep)
4744 @item @code{--version}
4746 Display Copyright and version, then exit disregarding all other options.
4749 @geindex --help (gnatprep)
4756 If @code{--version} was not used, display usage and then exit disregarding
4760 @geindex -b (gnatprep)
4767 Causes both preprocessor lines and the lines deleted by
4768 preprocessing to be replaced by blank lines in the output source file,
4769 preserving line numbers in the output file.
4772 @geindex -c (gnatprep)
4779 Causes both preprocessor lines and the lines deleted
4780 by preprocessing to be retained in the output source as comments marked
4781 with the special string @code{"--! "}. This option will result in line numbers
4782 being preserved in the output file.
4785 @geindex -C (gnatprep)
4792 Causes comments to be scanned. Normally comments are ignored by gnatprep.
4793 If this option is specified, then comments are scanned and any $symbol
4794 substitutions performed as in program text. This is particularly useful
4795 when structured comments are used (e.g., for programs written in a
4796 pre-2014 version of the SPARK Ada subset). Note that this switch is not
4797 available when doing integrated preprocessing (it would be useless in
4798 this context since comments are ignored by the compiler in any case).
4801 @geindex -D (gnatprep)
4806 @item @code{-D@emph{symbol}[=@emph{value}]}
4808 Defines a new preprocessing symbol with the specified value. If no value is given
4809 on the command line, then symbol is considered to be @code{True}. This switch
4810 can be used in place of a definition file.
4813 @geindex -r (gnatprep)
4820 Causes a @code{Source_Reference} pragma to be generated that
4821 references the original input file, so that error messages will use
4822 the file name of this original file. The use of this switch implies
4823 that preprocessor lines are not to be removed from the file, so its
4824 use will force @code{-b} mode if @code{-c}
4825 has not been specified explicitly.
4827 Note that if the file to be preprocessed contains multiple units, then
4828 it will be necessary to @code{gnatchop} the output file from
4829 @code{gnatprep}. If a @code{Source_Reference} pragma is present
4830 in the preprocessed file, it will be respected by
4832 so that the final chopped files will correctly refer to the original
4833 input source file for @code{gnatprep}.
4836 @geindex -s (gnatprep)
4843 Causes a sorted list of symbol names and values to be
4844 listed on the standard output file.
4847 @geindex -T (gnatprep)
4854 Use LF as line terminators when writing files. By default the line terminator
4855 of the host (LF under unix, CR/LF under Windows) is used.
4858 @geindex -u (gnatprep)
4865 Causes undefined symbols to be treated as having the value FALSE in the context
4866 of a preprocessor test. In the absence of this option, an undefined symbol in
4867 a @code{#if} or @code{#elsif} test will be treated as an error.
4870 @geindex -v (gnatprep)
4877 Verbose mode: generates more output about work done.
4880 Note: if neither @code{-b} nor @code{-c} is present,
4881 then preprocessor lines and
4882 deleted lines are completely removed from the output, unless -r is
4883 specified, in which case -b is assumed.
4885 @node Form of Definitions File,Form of Input Text for gnatprep,Switches for gnatprep,Preprocessing with gnatprep
4886 @anchor{gnat_ugn/the_gnat_compilation_model form-of-definitions-file}@anchor{ac}@anchor{gnat_ugn/the_gnat_compilation_model id58}@anchor{ad}
4887 @subsubsection Form of Definitions File
4890 The definitions file contains lines of the form:
4896 where @code{symbol} is a preprocessing symbol, and @code{value} is one of the following:
4902 Empty, corresponding to a null substitution,
4905 A string literal using normal Ada syntax, or
4908 Any sequence of characters from the set @{letters, digits, period, underline@}.
4911 Comment lines may also appear in the definitions file, starting with
4912 the usual @code{--},
4913 and comments may be added to the definitions lines.
4915 @node Form of Input Text for gnatprep,,Form of Definitions File,Preprocessing with gnatprep
4916 @anchor{gnat_ugn/the_gnat_compilation_model id59}@anchor{ae}@anchor{gnat_ugn/the_gnat_compilation_model form-of-input-text-for-gnatprep}@anchor{af}
4917 @subsubsection Form of Input Text for @code{gnatprep}
4920 The input text may contain preprocessor conditional inclusion lines,
4921 as well as general symbol substitution sequences.
4923 The preprocessor conditional inclusion commands have the form:
4926 #if <expression> [then]
4928 #elsif <expression> [then]
4930 #elsif <expression> [then]
4938 In this example, <expression> is defined by the following grammar:
4941 <expression> ::= <symbol>
4942 <expression> ::= <symbol> = "<value>"
4943 <expression> ::= <symbol> = <symbol>
4944 <expression> ::= <symbol> = <integer>
4945 <expression> ::= <symbol> > <integer>
4946 <expression> ::= <symbol> >= <integer>
4947 <expression> ::= <symbol> < <integer>
4948 <expression> ::= <symbol> <= <integer>
4949 <expression> ::= <symbol> 'Defined
4950 <expression> ::= not <expression>
4951 <expression> ::= <expression> and <expression>
4952 <expression> ::= <expression> or <expression>
4953 <expression> ::= <expression> and then <expression>
4954 <expression> ::= <expression> or else <expression>
4955 <expression> ::= ( <expression> )
4958 Note the following restriction: it is not allowed to have "and" or "or"
4959 following "not" in the same expression without parentheses. For example, this
4966 This can be expressed instead as one of the following forms:
4973 For the first test (<expression> ::= <symbol>) the symbol must have
4974 either the value true or false, that is to say the right-hand of the
4975 symbol definition must be one of the (case-insensitive) literals
4976 @code{True} or @code{False}. If the value is true, then the
4977 corresponding lines are included, and if the value is false, they are
4980 When comparing a symbol to an integer, the integer is any non negative
4981 literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or
4982 2#11#. The symbol value must also be a non negative integer. Integer values
4983 in the range 0 .. 2**31-1 are supported.
4985 The test (<expression> ::= <symbol>'Defined) is true only if
4986 the symbol has been defined in the definition file or by a @code{-D}
4987 switch on the command line. Otherwise, the test is false.
4989 The equality tests are case insensitive, as are all the preprocessor lines.
4991 If the symbol referenced is not defined in the symbol definitions file,
4992 then the effect depends on whether or not switch @code{-u}
4993 is specified. If so, then the symbol is treated as if it had the value
4994 false and the test fails. If this switch is not specified, then
4995 it is an error to reference an undefined symbol. It is also an error to
4996 reference a symbol that is defined with a value other than @code{True}
4999 The use of the @code{not} operator inverts the sense of this logical test.
5000 The @code{not} operator cannot be combined with the @code{or} or @code{and}
5001 operators, without parentheses. For example, "if not X or Y then" is not
5002 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
5004 The @code{then} keyword is optional as shown
5006 The @code{#} must be the first non-blank character on a line, but
5007 otherwise the format is free form. Spaces or tabs may appear between
5008 the @code{#} and the keyword. The keywords and the symbols are case
5009 insensitive as in normal Ada code. Comments may be used on a
5010 preprocessor line, but other than that, no other tokens may appear on a
5011 preprocessor line. Any number of @code{elsif} clauses can be present,
5012 including none at all. The @code{else} is optional, as in Ada.
5014 The @code{#} marking the start of a preprocessor line must be the first
5015 non-blank character on the line, i.e., it must be preceded only by
5016 spaces or horizontal tabs.
5018 Symbol substitution outside of preprocessor lines is obtained by using
5025 anywhere within a source line, except in a comment or within a
5026 string literal. The identifier
5027 following the @code{$} must match one of the symbols defined in the symbol
5028 definition file, and the result is to substitute the value of the
5029 symbol in place of @code{$symbol} in the output file.
5031 Note that although the substitution of strings within a string literal
5032 is not possible, it is possible to have a symbol whose defined value is
5033 a string literal. So instead of setting XYZ to @code{hello} and writing:
5036 Header : String := "$XYZ";
5039 you should set XYZ to @code{"hello"} and write:
5042 Header : String := $XYZ;
5045 and then the substitution will occur as desired.
5047 @node Integrated Preprocessing,,Preprocessing with gnatprep,Conditional Compilation
5048 @anchor{gnat_ugn/the_gnat_compilation_model id60}@anchor{b0}@anchor{gnat_ugn/the_gnat_compilation_model integrated-preprocessing}@anchor{18}
5049 @subsection Integrated Preprocessing
5052 As noted above, a file to be preprocessed consists of Ada source code
5053 in which preprocessing lines have been inserted. However,
5054 instead of using @code{gnatprep} to explicitly preprocess a file as a separate
5055 step before compilation, you can carry out the preprocessing implicitly
5056 as part of compilation. Such @emph{integrated preprocessing}, which is the common
5057 style with C, is performed when either or both of the following switches
5058 are passed to the compiler:
5066 @code{-gnatep}, which specifies the @emph{preprocessor data file}.
5067 This file dictates how the source files will be preprocessed (e.g., which
5068 symbol definition files apply to which sources).
5071 @code{-gnateD}, which defines values for preprocessing symbols.
5075 Integrated preprocessing applies only to Ada source files, it is
5076 not available for configuration pragma files.
5078 With integrated preprocessing, the output from the preprocessor is not,
5079 by default, written to any external file. Instead it is passed
5080 internally to the compiler. To preserve the result of
5081 preprocessing in a file, either run @code{gnatprep}
5082 in standalone mode or else supply the @code{-gnateG} switch
5083 (described below) to the compiler.
5085 When using project files:
5093 the builder switch @code{-x} should be used if any Ada source is
5094 compiled with @code{gnatep=}, so that the compiler finds the
5095 @emph{preprocessor data file}.
5098 the preprocessing data file and the symbol definition files should be
5099 located in the source directories of the project.
5103 Note that the @code{gnatmake} switch @code{-m} will almost
5104 always trigger recompilation for sources that are preprocessed,
5105 because @code{gnatmake} cannot compute the checksum of the source after
5108 The actual preprocessing function is described in detail in
5109 @ref{17,,Preprocessing with gnatprep}. This section explains the switches
5110 that relate to integrated preprocessing.
5112 @geindex -gnatep (gcc)
5117 @item @code{-gnatep=@emph{preprocessor_data_file}}
5119 This switch specifies the file name (without directory
5120 information) of the preprocessor data file. Either place this file
5121 in one of the source directories, or, when using project
5122 files, reference the project file's directory via the
5123 @code{project_name'Project_Dir} project attribute; e.g:
5130 for Switches ("Ada") use
5131 ("-gnatep=" & Prj'Project_Dir & "prep.def");
5137 A preprocessor data file is a text file that contains @emph{preprocessor
5138 control lines}. A preprocessor control line directs the preprocessing of
5139 either a particular source file, or, analogous to @code{others} in Ada,
5140 all sources not specified elsewhere in the preprocessor data file.
5141 A preprocessor control line
5142 can optionally identify a @emph{definition file} that assigns values to
5143 preprocessor symbols, as well as a list of switches that relate to
5145 Empty lines and comments (using Ada syntax) are also permitted, with no
5148 Here's an example of a preprocessor data file:
5153 "toto.adb" "prep.def" -u
5154 -- Preprocess toto.adb, using definition file prep.def
5155 -- Undefined symbols are treated as False
5158 -- Preprocess all other sources without using a definition file
5159 -- Suppressed lined are commented
5160 -- Symbol VERSION has the value V101
5162 "tata.adb" "prep2.def" -s
5163 -- Preprocess tata.adb, using definition file prep2.def
5164 -- List all symbols with their values
5168 A preprocessor control line has the following syntax:
5173 <preprocessor_control_line> ::=
5174 <preprocessor_input> [ <definition_file_name> ] @{ <switch> @}
5176 <preprocessor_input> ::= <source_file_name> | '*'
5178 <definition_file_name> ::= <string_literal>
5180 <source_file_name> := <string_literal>
5182 <switch> := (See below for list)
5186 Thus each preprocessor control line starts with either a literal string or
5193 A literal string is the file name (without directory information) of the source
5194 file that will be input to the preprocessor.
5197 The character '*' is a wild-card indicator; the additional parameters on the line
5198 indicate the preprocessing for all the sources
5199 that are not specified explicitly on other lines (the order of the lines is not
5203 It is an error to have two lines with the same file name or two
5204 lines starting with the character '*'.
5206 After the file name or '*', an optional literal string specifies the name of
5207 the definition file to be used for preprocessing
5208 (@ref{ac,,Form of Definitions File}). The definition files are found by the
5209 compiler in one of the source directories. In some cases, when compiling
5210 a source in a directory other than the current directory, if the definition
5211 file is in the current directory, it may be necessary to add the current
5212 directory as a source directory through the @code{-I} switch; otherwise
5213 the compiler would not find the definition file.
5215 Finally, switches similar to those of @code{gnatprep} may optionally appear:
5222 Causes both preprocessor lines and the lines deleted by
5223 preprocessing to be replaced by blank lines, preserving the line number.
5224 This switch is always implied; however, if specified after @code{-c}
5225 it cancels the effect of @code{-c}.
5229 Causes both preprocessor lines and the lines deleted
5230 by preprocessing to be retained as comments marked
5231 with the special string '@cite{--!}'.
5233 @item @code{-D@emph{symbol}=@emph{new_value}}
5235 Define or redefine @code{symbol} to have @code{new_value} as its value.
5236 The permitted form for @code{symbol} is either an Ada identifier, or any Ada reserved word
5237 aside from @code{if},
5238 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
5239 The permitted form for @code{new_value} is a literal string, an Ada identifier or any Ada reserved
5240 word. A symbol declared with this switch replaces a symbol with the
5241 same name defined in a definition file.
5245 Causes a sorted list of symbol names and values to be
5246 listed on the standard output file.
5250 Causes undefined symbols to be treated as having the value @code{FALSE}
5252 of a preprocessor test. In the absence of this option, an undefined symbol in
5253 a @code{#if} or @code{#elsif} test will be treated as an error.
5257 @geindex -gnateD (gcc)
5262 @item @code{-gnateD@emph{symbol}[=@emph{new_value}]}
5264 Define or redefine @code{symbol} to have @code{new_value} as its value. If no value
5265 is supplied, then the value of @code{symbol} is @code{True}.
5266 The form of @code{symbol} is an identifier, following normal Ada (case-insensitive)
5267 rules for its syntax, and @code{new_value} is either an arbitrary string between double
5268 quotes or any sequence (including an empty sequence) of characters from the
5269 set (letters, digits, period, underline).
5270 Ada reserved words may be used as symbols, with the exceptions of @code{if},
5271 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
5280 -gnateDFoo=\"Foo-Bar\"
5284 A symbol declared with this switch on the command line replaces a
5285 symbol with the same name either in a definition file or specified with a
5286 switch @code{-D} in the preprocessor data file.
5288 This switch is similar to switch @code{-D} of @code{gnatprep}.
5290 @item @code{-gnateG}
5292 When integrated preprocessing is performed on source file @code{filename.extension},
5293 create or overwrite @code{filename.extension.prep} to contain
5294 the result of the preprocessing.
5295 For example if the source file is @code{foo.adb} then
5296 the output file will be @code{foo.adb.prep}.
5299 @node Mixed Language Programming,GNAT and Other Compilation Models,Conditional Compilation,The GNAT Compilation Model
5300 @anchor{gnat_ugn/the_gnat_compilation_model mixed-language-programming}@anchor{44}@anchor{gnat_ugn/the_gnat_compilation_model id61}@anchor{b1}
5301 @section Mixed Language Programming
5304 @geindex Mixed Language Programming
5306 This section describes how to develop a mixed-language program,
5307 with a focus on combining Ada with C or C++.
5310 * Interfacing to C::
5311 * Calling Conventions::
5312 * Building Mixed Ada and C++ Programs::
5313 * Generating Ada Bindings for C and C++ headers::
5314 * Generating C Headers for Ada Specifications::
5318 @node Interfacing to C,Calling Conventions,,Mixed Language Programming
5319 @anchor{gnat_ugn/the_gnat_compilation_model interfacing-to-c}@anchor{b2}@anchor{gnat_ugn/the_gnat_compilation_model id62}@anchor{b3}
5320 @subsection Interfacing to C
5323 Interfacing Ada with a foreign language such as C involves using
5324 compiler directives to import and/or export entity definitions in each
5325 language -- using @code{extern} statements in C, for instance, and the
5326 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
5327 A full treatment of these topics is provided in Appendix B, section 1
5328 of the Ada Reference Manual.
5330 There are two ways to build a program using GNAT that contains some Ada
5331 sources and some foreign language sources, depending on whether or not
5332 the main subprogram is written in Ada. Here is a source example with
5333 the main subprogram in Ada:
5339 void print_num (int num)
5341 printf ("num is %d.\\n", num);
5349 /* num_from_Ada is declared in my_main.adb */
5350 extern int num_from_Ada;
5354 return num_from_Ada;
5360 procedure My_Main is
5362 -- Declare then export an Integer entity called num_from_Ada
5363 My_Num : Integer := 10;
5364 pragma Export (C, My_Num, "num_from_Ada");
5366 -- Declare an Ada function spec for Get_Num, then use
5367 -- C function get_num for the implementation.
5368 function Get_Num return Integer;
5369 pragma Import (C, Get_Num, "get_num");
5371 -- Declare an Ada procedure spec for Print_Num, then use
5372 -- C function print_num for the implementation.
5373 procedure Print_Num (Num : Integer);
5374 pragma Import (C, Print_Num, "print_num");
5377 Print_Num (Get_Num);
5381 To build this example:
5387 First compile the foreign language files to
5388 generate object files:
5396 Then, compile the Ada units to produce a set of object files and ALI
5400 $ gnatmake -c my_main.adb
5404 Run the Ada binder on the Ada main program:
5407 $ gnatbind my_main.ali
5411 Link the Ada main program, the Ada objects and the other language
5415 $ gnatlink my_main.ali file1.o file2.o
5419 The last three steps can be grouped in a single command:
5422 $ gnatmake my_main.adb -largs file1.o file2.o
5425 @geindex Binder output file
5427 If the main program is in a language other than Ada, then you may have
5428 more than one entry point into the Ada subsystem. You must use a special
5429 binder option to generate callable routines that initialize and
5430 finalize the Ada units (@ref{b4,,Binding with Non-Ada Main Programs}).
5431 Calls to the initialization and finalization routines must be inserted
5432 in the main program, or some other appropriate point in the code. The
5433 call to initialize the Ada units must occur before the first Ada
5434 subprogram is called, and the call to finalize the Ada units must occur
5435 after the last Ada subprogram returns. The binder will place the
5436 initialization and finalization subprograms into the
5437 @code{b~xxx.adb} file where they can be accessed by your C
5438 sources. To illustrate, we have the following example:
5442 extern void adainit (void);
5443 extern void adafinal (void);
5444 extern int add (int, int);
5445 extern int sub (int, int);
5447 int main (int argc, char *argv[])
5453 /* Should print "21 + 7 = 28" */
5454 printf ("%d + %d = %d\\n", a, b, add (a, b));
5456 /* Should print "21 - 7 = 14" */
5457 printf ("%d - %d = %d\\n", a, b, sub (a, b));
5466 function Add (A, B : Integer) return Integer;
5467 pragma Export (C, Add, "add");
5473 package body Unit1 is
5474 function Add (A, B : Integer) return Integer is
5484 function Sub (A, B : Integer) return Integer;
5485 pragma Export (C, Sub, "sub");
5491 package body Unit2 is
5492 function Sub (A, B : Integer) return Integer is
5499 The build procedure for this application is similar to the last
5506 First, compile the foreign language files to generate object files:
5513 Next, compile the Ada units to produce a set of object files and ALI
5517 $ gnatmake -c unit1.adb
5518 $ gnatmake -c unit2.adb
5522 Run the Ada binder on every generated ALI file. Make sure to use the
5523 @code{-n} option to specify a foreign main program:
5526 $ gnatbind -n unit1.ali unit2.ali
5530 Link the Ada main program, the Ada objects and the foreign language
5531 objects. You need only list the last ALI file here:
5534 $ gnatlink unit2.ali main.o -o exec_file
5537 This procedure yields a binary executable called @code{exec_file}.
5540 Depending on the circumstances (for example when your non-Ada main object
5541 does not provide symbol @code{main}), you may also need to instruct the
5542 GNAT linker not to include the standard startup objects by passing the
5543 @code{-nostartfiles} switch to @code{gnatlink}.
5545 @node Calling Conventions,Building Mixed Ada and C++ Programs,Interfacing to C,Mixed Language Programming
5546 @anchor{gnat_ugn/the_gnat_compilation_model calling-conventions}@anchor{b5}@anchor{gnat_ugn/the_gnat_compilation_model id63}@anchor{b6}
5547 @subsection Calling Conventions
5550 @geindex Foreign Languages
5552 @geindex Calling Conventions
5554 GNAT follows standard calling sequence conventions and will thus interface
5555 to any other language that also follows these conventions. The following
5556 Convention identifiers are recognized by GNAT:
5558 @geindex Interfacing to Ada
5560 @geindex Other Ada compilers
5562 @geindex Convention Ada
5569 This indicates that the standard Ada calling sequence will be
5570 used and all Ada data items may be passed without any limitations in the
5571 case where GNAT is used to generate both the caller and callee. It is also
5572 possible to mix GNAT generated code and code generated by another Ada
5573 compiler. In this case, the data types should be restricted to simple
5574 cases, including primitive types. Whether complex data types can be passed
5575 depends on the situation. Probably it is safe to pass simple arrays, such
5576 as arrays of integers or floats. Records may or may not work, depending
5577 on whether both compilers lay them out identically. Complex structures
5578 involving variant records, access parameters, tasks, or protected types,
5579 are unlikely to be able to be passed.
5581 Note that in the case of GNAT running
5582 on a platform that supports HP Ada 83, a higher degree of compatibility
5583 can be guaranteed, and in particular records are laid out in an identical
5584 manner in the two compilers. Note also that if output from two different
5585 compilers is mixed, the program is responsible for dealing with elaboration
5586 issues. Probably the safest approach is to write the main program in the
5587 version of Ada other than GNAT, so that it takes care of its own elaboration
5588 requirements, and then call the GNAT-generated adainit procedure to ensure
5589 elaboration of the GNAT components. Consult the documentation of the other
5590 Ada compiler for further details on elaboration.
5592 However, it is not possible to mix the tasking run time of GNAT and
5593 HP Ada 83, All the tasking operations must either be entirely within
5594 GNAT compiled sections of the program, or entirely within HP Ada 83
5595 compiled sections of the program.
5598 @geindex Interfacing to Assembly
5600 @geindex Convention Assembler
5605 @item @code{Assembler}
5607 Specifies assembler as the convention. In practice this has the
5608 same effect as convention Ada (but is not equivalent in the sense of being
5609 considered the same convention).
5612 @geindex Convention Asm
5621 Equivalent to Assembler.
5623 @geindex Interfacing to COBOL
5625 @geindex Convention COBOL
5635 Data will be passed according to the conventions described
5636 in section B.4 of the Ada Reference Manual.
5641 @geindex Interfacing to C
5643 @geindex Convention C
5650 Data will be passed according to the conventions described
5651 in section B.3 of the Ada Reference Manual.
5653 A note on interfacing to a C 'varargs' function:
5657 @geindex C varargs function
5659 @geindex Interfacing to C varargs function
5661 @geindex varargs function interfaces
5663 In C, @code{varargs} allows a function to take a variable number of
5664 arguments. There is no direct equivalent in this to Ada. One
5665 approach that can be used is to create a C wrapper for each
5666 different profile and then interface to this C wrapper. For
5667 example, to print an @code{int} value using @code{printf},
5668 create a C function @code{printfi} that takes two arguments, a
5669 pointer to a string and an int, and calls @code{printf}.
5670 Then in the Ada program, use pragma @code{Import} to
5671 interface to @code{printfi}.
5673 It may work on some platforms to directly interface to
5674 a @code{varargs} function by providing a specific Ada profile
5675 for a particular call. However, this does not work on
5676 all platforms, since there is no guarantee that the
5677 calling sequence for a two argument normal C function
5678 is the same as for calling a @code{varargs} C function with
5679 the same two arguments.
5683 @geindex Convention Default
5690 @item @code{Default}
5695 @geindex Convention External
5702 @item @code{External}
5709 @geindex Interfacing to C++
5711 @geindex Convention C++
5716 @item @code{C_Plus_Plus} (or @code{CPP})
5718 This stands for C++. For most purposes this is identical to C.
5719 See the separate description of the specialized GNAT pragmas relating to
5720 C++ interfacing for further details.
5725 @geindex Interfacing to Fortran
5727 @geindex Convention Fortran
5732 @item @code{Fortran}
5734 Data will be passed according to the conventions described
5735 in section B.5 of the Ada Reference Manual.
5737 @item @code{Intrinsic}
5739 This applies to an intrinsic operation, as defined in the Ada
5740 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
5741 this means that the body of the subprogram is provided by the compiler itself,
5742 usually by means of an efficient code sequence, and that the user does not
5743 supply an explicit body for it. In an application program, the pragma may
5744 be applied to the following sets of names:
5750 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_Arithmetic.
5751 The corresponding subprogram declaration must have
5752 two formal parameters. The
5753 first one must be a signed integer type or a modular type with a binary
5754 modulus, and the second parameter must be of type Natural.
5755 The return type must be the same as the type of the first argument. The size
5756 of this type can only be 8, 16, 32, or 64.
5759 Binary arithmetic operators: '+', '-', '*', '/'.
5760 The corresponding operator declaration must have parameters and result type
5761 that have the same root numeric type (for example, all three are long_float
5762 types). This simplifies the definition of operations that use type checking
5763 to perform dimensional checks:
5767 type Distance is new Long_Float;
5768 type Time is new Long_Float;
5769 type Velocity is new Long_Float;
5770 function "/" (D : Distance; T : Time)
5772 pragma Import (Intrinsic, "/");
5774 This common idiom is often programmed with a generic definition and an
5775 explicit body. The pragma makes it simpler to introduce such declarations.
5776 It incurs no overhead in compilation time or code size, because it is
5777 implemented as a single machine instruction.
5784 General subprogram entities. This is used to bind an Ada subprogram
5786 a compiler builtin by name with back-ends where such interfaces are
5787 available. A typical example is the set of @code{__builtin} functions
5788 exposed by the GCC back-end, as in the following example:
5791 function builtin_sqrt (F : Float) return Float;
5792 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
5795 Most of the GCC builtins are accessible this way, and as for other
5796 import conventions (e.g. C), it is the user's responsibility to ensure
5797 that the Ada subprogram profile matches the underlying builtin
5804 @geindex Convention Stdcall
5809 @item @code{Stdcall}
5811 This is relevant only to Windows implementations of GNAT,
5812 and specifies that the @code{Stdcall} calling sequence will be used,
5813 as defined by the NT API. Nevertheless, to ease building
5814 cross-platform bindings this convention will be handled as a @code{C} calling
5815 convention on non-Windows platforms.
5820 @geindex Convention DLL
5827 This is equivalent to @code{Stdcall}.
5832 @geindex Convention Win32
5839 This is equivalent to @code{Stdcall}.
5844 @geindex Convention Stubbed
5849 @item @code{Stubbed}
5851 This is a special convention that indicates that the compiler
5852 should provide a stub body that raises @code{Program_Error}.
5855 GNAT additionally provides a useful pragma @code{Convention_Identifier}
5856 that can be used to parameterize conventions and allow additional synonyms
5857 to be specified. For example if you have legacy code in which the convention
5858 identifier Fortran77 was used for Fortran, you can use the configuration
5862 pragma Convention_Identifier (Fortran77, Fortran);
5865 And from now on the identifier Fortran77 may be used as a convention
5866 identifier (for example in an @code{Import} pragma) with the same
5869 @node Building Mixed Ada and C++ Programs,Generating Ada Bindings for C and C++ headers,Calling Conventions,Mixed Language Programming
5870 @anchor{gnat_ugn/the_gnat_compilation_model id64}@anchor{b7}@anchor{gnat_ugn/the_gnat_compilation_model building-mixed-ada-and-c-programs}@anchor{b8}
5871 @subsection Building Mixed Ada and C++ Programs
5874 A programmer inexperienced with mixed-language development may find that
5875 building an application containing both Ada and C++ code can be a
5876 challenge. This section gives a few hints that should make this task easier.
5879 * Interfacing to C++::
5880 * Linking a Mixed C++ & Ada Program::
5881 * A Simple Example::
5882 * Interfacing with C++ constructors::
5883 * Interfacing with C++ at the Class Level::
5887 @node Interfacing to C++,Linking a Mixed C++ & Ada Program,,Building Mixed Ada and C++ Programs
5888 @anchor{gnat_ugn/the_gnat_compilation_model id65}@anchor{b9}@anchor{gnat_ugn/the_gnat_compilation_model id66}@anchor{ba}
5889 @subsubsection Interfacing to C++
5892 GNAT supports interfacing with the G++ compiler (or any C++ compiler
5893 generating code that is compatible with the G++ Application Binary
5894 Interface ---see @indicateurl{http://www.codesourcery.com/archives/cxx-abi}).
5896 Interfacing can be done at 3 levels: simple data, subprograms, and
5897 classes. In the first two cases, GNAT offers a specific @code{Convention C_Plus_Plus}
5898 (or @code{CPP}) that behaves exactly like @code{Convention C}.
5899 Usually, C++ mangles the names of subprograms. To generate proper mangled
5900 names automatically, see @ref{19,,Generating Ada Bindings for C and C++ headers}).
5901 This problem can also be addressed manually in two ways:
5907 by modifying the C++ code in order to force a C convention using
5908 the @code{extern "C"} syntax.
5911 by figuring out the mangled name (using e.g. @code{nm}) and using it as the
5912 Link_Name argument of the pragma import.
5915 Interfacing at the class level can be achieved by using the GNAT specific
5916 pragmas such as @code{CPP_Constructor}. See the @cite{GNAT_Reference_Manual} for additional information.
5918 @node Linking a Mixed C++ & Ada Program,A Simple Example,Interfacing to C++,Building Mixed Ada and C++ Programs
5919 @anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-ada-program}@anchor{bb}@anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-and-ada-program}@anchor{bc}
5920 @subsubsection Linking a Mixed C++ & Ada Program
5923 Usually the linker of the C++ development system must be used to link
5924 mixed applications because most C++ systems will resolve elaboration
5925 issues (such as calling constructors on global class instances)
5926 transparently during the link phase. GNAT has been adapted to ease the
5927 use of a foreign linker for the last phase. Three cases can be
5934 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
5935 The C++ linker can simply be called by using the C++ specific driver
5938 Note that if the C++ code uses inline functions, you will need to
5939 compile your C++ code with the @code{-fkeep-inline-functions} switch in
5940 order to provide an existing function implementation that the Ada code can
5944 $ g++ -c -fkeep-inline-functions file1.C
5945 $ g++ -c -fkeep-inline-functions file2.C
5946 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
5950 Using GNAT and G++ from two different GCC installations: If both
5951 compilers are on the :envvar`PATH`, the previous method may be used. It is
5952 important to note that environment variables such as
5953 @geindex C_INCLUDE_PATH
5954 @geindex environment variable; C_INCLUDE_PATH
5955 @code{C_INCLUDE_PATH},
5956 @geindex GCC_EXEC_PREFIX
5957 @geindex environment variable; GCC_EXEC_PREFIX
5958 @code{GCC_EXEC_PREFIX},
5959 @geindex BINUTILS_ROOT
5960 @geindex environment variable; BINUTILS_ROOT
5961 @code{BINUTILS_ROOT}, and
5963 @geindex environment variable; GCC_ROOT
5964 @code{GCC_ROOT} will affect both compilers
5965 at the same time and may make one of the two compilers operate
5966 improperly if set during invocation of the wrong compiler. It is also
5967 very important that the linker uses the proper @code{libgcc.a} GCC
5968 library -- that is, the one from the C++ compiler installation. The
5969 implicit link command as suggested in the @code{gnatmake} command
5970 from the former example can be replaced by an explicit link command with
5971 the full-verbosity option in order to verify which library is used:
5975 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
5978 If there is a problem due to interfering environment variables, it can
5979 be worked around by using an intermediate script. The following example
5980 shows the proper script to use when GNAT has not been installed at its
5981 default location and g++ has been installed at its default location:
5989 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
5993 Using a non-GNU C++ compiler: The commands previously described can be
5994 used to insure that the C++ linker is used. Nonetheless, you need to add
5995 a few more parameters to the link command line, depending on the exception
5998 If the @code{setjmp} / @code{longjmp} exception mechanism is used, only the paths
5999 to the @code{libgcc} libraries are required:
6004 CC $* gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a
6005 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
6008 where CC is the name of the non-GNU C++ compiler.
6010 If the "zero cost" exception mechanism is used, and the platform
6011 supports automatic registration of exception tables (e.g., Solaris),
6012 paths to more objects are required:
6017 CC gcc -print-file-name=crtbegin.o $* \\
6018 gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a \\
6019 gcc -print-file-name=crtend.o
6020 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
6023 If the "zero cost exception" mechanism is used, and the platform
6024 doesn't support automatic registration of exception tables (e.g., HP-UX
6025 or AIX), the simple approach described above will not work and
6026 a pre-linking phase using GNAT will be necessary.
6029 Another alternative is to use the @code{gprbuild} multi-language builder
6030 which has a large knowledge base and knows how to link Ada and C++ code
6031 together automatically in most cases.
6033 @node A Simple Example,Interfacing with C++ constructors,Linking a Mixed C++ & Ada Program,Building Mixed Ada and C++ Programs
6034 @anchor{gnat_ugn/the_gnat_compilation_model id67}@anchor{bd}@anchor{gnat_ugn/the_gnat_compilation_model a-simple-example}@anchor{be}
6035 @subsubsection A Simple Example
6038 The following example, provided as part of the GNAT examples, shows how
6039 to achieve procedural interfacing between Ada and C++ in both
6040 directions. The C++ class A has two methods. The first method is exported
6041 to Ada by the means of an extern C wrapper function. The second method
6042 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
6043 a limited record with a layout comparable to the C++ class. The Ada
6044 subprogram, in turn, calls the C++ method. So, starting from the C++
6045 main program, the process passes back and forth between the two
6048 Here are the compilation commands:
6051 $ gnatmake -c simple_cpp_interface
6054 $ gnatbind -n simple_cpp_interface
6055 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o
6058 Here are the corresponding sources:
6066 void adainit (void);
6067 void adafinal (void);
6068 void method1 (A *t);
6092 class A : public Origin @{
6094 void method1 (void);
6095 void method2 (int v);
6107 extern "C" @{ void ada_method2 (A *t, int v);@}
6109 void A::method1 (void)
6112 printf ("in A::method1, a_value = %d \\n",a_value);
6115 void A::method2 (int v)
6117 ada_method2 (this, v);
6118 printf ("in A::method2, a_value = %d \\n",a_value);
6124 printf ("in A::A, a_value = %d \\n",a_value);
6129 -- simple_cpp_interface.ads
6131 package Simple_Cpp_Interface is
6134 Vptr : System.Address;
6138 pragma Convention (C, A);
6140 procedure Method1 (This : in out A);
6141 pragma Import (C, Method1);
6143 procedure Ada_Method2 (This : in out A; V : Integer);
6144 pragma Export (C, Ada_Method2);
6146 end Simple_Cpp_Interface;
6150 -- simple_cpp_interface.adb
6151 package body Simple_Cpp_Interface is
6153 procedure Ada_Method2 (This : in out A; V : Integer) is
6159 end Simple_Cpp_Interface;
6162 @node Interfacing with C++ constructors,Interfacing with C++ at the Class Level,A Simple Example,Building Mixed Ada and C++ Programs
6163 @anchor{gnat_ugn/the_gnat_compilation_model id68}@anchor{bf}@anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-constructors}@anchor{c0}
6164 @subsubsection Interfacing with C++ constructors
6167 In order to interface with C++ constructors GNAT provides the
6168 @code{pragma CPP_Constructor} (see the @cite{GNAT_Reference_Manual}
6169 for additional information).
6170 In this section we present some common uses of C++ constructors
6171 in mixed-languages programs in GNAT.
6173 Let us assume that we need to interface with the following
6181 virtual int Get_Value ();
6182 Root(); // Default constructor
6183 Root(int v); // 1st non-default constructor
6184 Root(int v, int w); // 2nd non-default constructor
6188 For this purpose we can write the following package spec (further
6189 information on how to build this spec is available in
6190 @ref{c1,,Interfacing with C++ at the Class Level} and
6191 @ref{19,,Generating Ada Bindings for C and C++ headers}).
6194 with Interfaces.C; use Interfaces.C;
6196 type Root is tagged limited record
6200 pragma Import (CPP, Root);
6202 function Get_Value (Obj : Root) return int;
6203 pragma Import (CPP, Get_Value);
6205 function Constructor return Root;
6206 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
6208 function Constructor (v : Integer) return Root;
6209 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
6211 function Constructor (v, w : Integer) return Root;
6212 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
6216 On the Ada side the constructor is represented by a function (whose
6217 name is arbitrary) that returns the classwide type corresponding to
6218 the imported C++ class. Although the constructor is described as a
6219 function, it is typically a procedure with an extra implicit argument
6220 (the object being initialized) at the implementation level. GNAT
6221 issues the appropriate call, whatever it is, to get the object
6222 properly initialized.
6224 Constructors can only appear in the following contexts:
6230 On the right side of an initialization of an object of type @code{T}.
6233 On the right side of an initialization of a record component of type @code{T}.
6236 In an Ada 2005 limited aggregate.
6239 In an Ada 2005 nested limited aggregate.
6242 In an Ada 2005 limited aggregate that initializes an object built in
6243 place by an extended return statement.
6246 In a declaration of an object whose type is a class imported from C++,
6247 either the default C++ constructor is implicitly called by GNAT, or
6248 else the required C++ constructor must be explicitly called in the
6249 expression that initializes the object. For example:
6253 Obj2 : Root := Constructor;
6254 Obj3 : Root := Constructor (v => 10);
6255 Obj4 : Root := Constructor (30, 40);
6258 The first two declarations are equivalent: in both cases the default C++
6259 constructor is invoked (in the former case the call to the constructor is
6260 implicit, and in the latter case the call is explicit in the object
6261 declaration). @code{Obj3} is initialized by the C++ non-default constructor
6262 that takes an integer argument, and @code{Obj4} is initialized by the
6263 non-default C++ constructor that takes two integers.
6265 Let us derive the imported C++ class in the Ada side. For example:
6268 type DT is new Root with record
6269 C_Value : Natural := 2009;
6273 In this case the components DT inherited from the C++ side must be
6274 initialized by a C++ constructor, and the additional Ada components
6275 of type DT are initialized by GNAT. The initialization of such an
6276 object is done either by default, or by means of a function returning
6277 an aggregate of type DT, or by means of an extension aggregate.
6281 Obj6 : DT := Function_Returning_DT (50);
6282 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
6285 The declaration of @code{Obj5} invokes the default constructors: the
6286 C++ default constructor of the parent type takes care of the initialization
6287 of the components inherited from Root, and GNAT takes care of the default
6288 initialization of the additional Ada components of type DT (that is,
6289 @code{C_Value} is initialized to value 2009). The order of invocation of
6290 the constructors is consistent with the order of elaboration required by
6291 Ada and C++. That is, the constructor of the parent type is always called
6292 before the constructor of the derived type.
6294 Let us now consider a record that has components whose type is imported
6295 from C++. For example:
6298 type Rec1 is limited record
6299 Data1 : Root := Constructor (10);
6300 Value : Natural := 1000;
6303 type Rec2 (D : Integer := 20) is limited record
6305 Data2 : Root := Constructor (D, 30);
6309 The initialization of an object of type @code{Rec2} will call the
6310 non-default C++ constructors specified for the imported components.
6317 Using Ada 2005 we can use limited aggregates to initialize an object
6318 invoking C++ constructors that differ from those specified in the type
6319 declarations. For example:
6322 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
6327 The above declaration uses an Ada 2005 limited aggregate to
6328 initialize @code{Obj9}, and the C++ constructor that has two integer
6329 arguments is invoked to initialize the @code{Data1} component instead
6330 of the constructor specified in the declaration of type @code{Rec1}. In
6331 Ada 2005 the box in the aggregate indicates that unspecified components
6332 are initialized using the expression (if any) available in the component
6333 declaration. That is, in this case discriminant @code{D} is initialized
6334 to value @code{20}, @code{Value} is initialized to value 1000, and the
6335 non-default C++ constructor that handles two integers takes care of
6336 initializing component @code{Data2} with values @code{20,30}.
6338 In Ada 2005 we can use the extended return statement to build the Ada
6339 equivalent to C++ non-default constructors. For example:
6342 function Constructor (V : Integer) return Rec2 is
6344 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
6347 -- Further actions required for construction of
6348 -- objects of type Rec2
6354 In this example the extended return statement construct is used to
6355 build in place the returned object whose components are initialized
6356 by means of a limited aggregate. Any further action associated with
6357 the constructor can be placed inside the construct.
6359 @node Interfacing with C++ at the Class Level,,Interfacing with C++ constructors,Building Mixed Ada and C++ Programs
6360 @anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-at-the-class-level}@anchor{c1}@anchor{gnat_ugn/the_gnat_compilation_model id69}@anchor{c2}
6361 @subsubsection Interfacing with C++ at the Class Level
6364 In this section we demonstrate the GNAT features for interfacing with
6365 C++ by means of an example making use of Ada 2005 abstract interface
6366 types. This example consists of a classification of animals; classes
6367 have been used to model our main classification of animals, and
6368 interfaces provide support for the management of secondary
6369 classifications. We first demonstrate a case in which the types and
6370 constructors are defined on the C++ side and imported from the Ada
6371 side, and latter the reverse case.
6373 The root of our derivation will be the @code{Animal} class, with a
6374 single private attribute (the @code{Age} of the animal), a constructor,
6375 and two public primitives to set and get the value of this attribute.
6380 virtual void Set_Age (int New_Age);
6382 Animal() @{Age_Count = 0;@};
6388 Abstract interface types are defined in C++ by means of classes with pure
6389 virtual functions and no data members. In our example we will use two
6390 interfaces that provide support for the common management of @code{Carnivore}
6391 and @code{Domestic} animals:
6396 virtual int Number_Of_Teeth () = 0;
6401 virtual void Set_Owner (char* Name) = 0;
6405 Using these declarations, we can now say that a @code{Dog} is an animal that is
6406 both Carnivore and Domestic, that is:
6409 class Dog : Animal, Carnivore, Domestic @{
6411 virtual int Number_Of_Teeth ();
6412 virtual void Set_Owner (char* Name);
6414 Dog(); // Constructor
6421 In the following examples we will assume that the previous declarations are
6422 located in a file named @code{animals.h}. The following package demonstrates
6423 how to import these C++ declarations from the Ada side:
6426 with Interfaces.C.Strings; use Interfaces.C.Strings;
6428 type Carnivore is limited interface;
6429 pragma Convention (C_Plus_Plus, Carnivore);
6430 function Number_Of_Teeth (X : Carnivore)
6431 return Natural is abstract;
6433 type Domestic is limited interface;
6434 pragma Convention (C_Plus_Plus, Domestic);
6436 (X : in out Domestic;
6437 Name : Chars_Ptr) is abstract;
6439 type Animal is tagged limited record
6442 pragma Import (C_Plus_Plus, Animal);
6444 procedure Set_Age (X : in out Animal; Age : Integer);
6445 pragma Import (C_Plus_Plus, Set_Age);
6447 function Age (X : Animal) return Integer;
6448 pragma Import (C_Plus_Plus, Age);
6450 function New_Animal return Animal;
6451 pragma CPP_Constructor (New_Animal);
6452 pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev");
6454 type Dog is new Animal and Carnivore and Domestic with record
6455 Tooth_Count : Natural;
6458 pragma Import (C_Plus_Plus, Dog);
6460 function Number_Of_Teeth (A : Dog) return Natural;
6461 pragma Import (C_Plus_Plus, Number_Of_Teeth);
6463 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
6464 pragma Import (C_Plus_Plus, Set_Owner);
6466 function New_Dog return Dog;
6467 pragma CPP_Constructor (New_Dog);
6468 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
6472 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
6473 interfacing with these C++ classes is easy. The only requirement is that all
6474 the primitives and components must be declared exactly in the same order in
6477 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
6478 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
6479 the arguments to the called primitives will be the same as for C++. For the
6480 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
6481 to indicate that they have been defined on the C++ side; this is required
6482 because the dispatch table associated with these tagged types will be built
6483 in the C++ side and therefore will not contain the predefined Ada primitives
6484 which Ada would otherwise expect.
6486 As the reader can see there is no need to indicate the C++ mangled names
6487 associated with each subprogram because it is assumed that all the calls to
6488 these primitives will be dispatching calls. The only exception is the
6489 constructor, which must be registered with the compiler by means of
6490 @code{pragma CPP_Constructor} and needs to provide its associated C++
6491 mangled name because the Ada compiler generates direct calls to it.
6493 With the above packages we can now declare objects of type Dog on the Ada side
6494 and dispatch calls to the corresponding subprograms on the C++ side. We can
6495 also extend the tagged type Dog with further fields and primitives, and
6496 override some of its C++ primitives on the Ada side. For example, here we have
6497 a type derivation defined on the Ada side that inherits all the dispatching
6498 primitives of the ancestor from the C++ side.
6501 with Animals; use Animals;
6502 package Vaccinated_Animals is
6503 type Vaccinated_Dog is new Dog with null record;
6504 function Vaccination_Expired (A : Vaccinated_Dog) return Boolean;
6505 end Vaccinated_Animals;
6508 It is important to note that, because of the ABI compatibility, the programmer
6509 does not need to add any further information to indicate either the object
6510 layout or the dispatch table entry associated with each dispatching operation.
6512 Now let us define all the types and constructors on the Ada side and export
6513 them to C++, using the same hierarchy of our previous example:
6516 with Interfaces.C.Strings;
6517 use Interfaces.C.Strings;
6519 type Carnivore is limited interface;
6520 pragma Convention (C_Plus_Plus, Carnivore);
6521 function Number_Of_Teeth (X : Carnivore)
6522 return Natural is abstract;
6524 type Domestic is limited interface;
6525 pragma Convention (C_Plus_Plus, Domestic);
6527 (X : in out Domestic;
6528 Name : Chars_Ptr) is abstract;
6530 type Animal is tagged record
6533 pragma Convention (C_Plus_Plus, Animal);
6535 procedure Set_Age (X : in out Animal; Age : Integer);
6536 pragma Export (C_Plus_Plus, Set_Age);
6538 function Age (X : Animal) return Integer;
6539 pragma Export (C_Plus_Plus, Age);
6541 function New_Animal return Animal'Class;
6542 pragma Export (C_Plus_Plus, New_Animal);
6544 type Dog is new Animal and Carnivore and Domestic with record
6545 Tooth_Count : Natural;
6546 Owner : String (1 .. 30);
6548 pragma Convention (C_Plus_Plus, Dog);
6550 function Number_Of_Teeth (A : Dog) return Natural;
6551 pragma Export (C_Plus_Plus, Number_Of_Teeth);
6553 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
6554 pragma Export (C_Plus_Plus, Set_Owner);
6556 function New_Dog return Dog'Class;
6557 pragma Export (C_Plus_Plus, New_Dog);
6561 Compared with our previous example the only differences are the use of
6562 @code{pragma Convention} (instead of @code{pragma Import}), and the use of
6563 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
6564 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
6565 nothing else to be done; as explained above, the only requirement is that all
6566 the primitives and components are declared in exactly the same order.
6568 For completeness, let us see a brief C++ main program that uses the
6569 declarations available in @code{animals.h} (presented in our first example) to
6570 import and use the declarations from the Ada side, properly initializing and
6571 finalizing the Ada run-time system along the way:
6574 #include "animals.h"
6576 using namespace std;
6578 void Check_Carnivore (Carnivore *obj) @{...@}
6579 void Check_Domestic (Domestic *obj) @{...@}
6580 void Check_Animal (Animal *obj) @{...@}
6581 void Check_Dog (Dog *obj) @{...@}
6584 void adainit (void);
6585 void adafinal (void);
6591 Dog *obj = new_dog(); // Ada constructor
6592 Check_Carnivore (obj); // Check secondary DT
6593 Check_Domestic (obj); // Check secondary DT
6594 Check_Animal (obj); // Check primary DT
6595 Check_Dog (obj); // Check primary DT
6600 adainit (); test(); adafinal ();
6605 @node Generating Ada Bindings for C and C++ headers,Generating C Headers for Ada Specifications,Building Mixed Ada and C++ Programs,Mixed Language Programming
6606 @anchor{gnat_ugn/the_gnat_compilation_model id70}@anchor{c3}@anchor{gnat_ugn/the_gnat_compilation_model generating-ada-bindings-for-c-and-c-headers}@anchor{19}
6607 @subsection Generating Ada Bindings for C and C++ headers
6610 @geindex Binding generation (for C and C++ headers)
6612 @geindex C headers (binding generation)
6614 @geindex C++ headers (binding generation)
6616 GNAT includes a binding generator for C and C++ headers which is
6617 intended to do 95% of the tedious work of generating Ada specs from C
6618 or C++ header files.
6620 Note that this capability is not intended to generate 100% correct Ada specs,
6621 and will is some cases require manual adjustments, although it can often
6622 be used out of the box in practice.
6624 Some of the known limitations include:
6630 only very simple character constant macros are translated into Ada
6631 constants. Function macros (macros with arguments) are partially translated
6632 as comments, to be completed manually if needed.
6635 some extensions (e.g. vector types) are not supported
6638 pointers to pointers or complex structures are mapped to System.Address
6641 identifiers with identical name (except casing) will generate compilation
6642 errors (e.g. @code{shm_get} vs @code{SHM_GET}).
6645 The code is generated using Ada 2012 syntax, which makes it easier to interface
6646 with other languages. In most cases you can still use the generated binding
6647 even if your code is compiled using earlier versions of Ada (e.g. @code{-gnat95}).
6650 * Running the Binding Generator::
6651 * Generating Bindings for C++ Headers::
6656 @node Running the Binding Generator,Generating Bindings for C++ Headers,,Generating Ada Bindings for C and C++ headers
6657 @anchor{gnat_ugn/the_gnat_compilation_model id71}@anchor{c4}@anchor{gnat_ugn/the_gnat_compilation_model running-the-binding-generator}@anchor{c5}
6658 @subsubsection Running the Binding Generator
6661 The binding generator is part of the @code{gcc} compiler and can be
6662 invoked via the @code{-fdump-ada-spec} switch, which will generate Ada
6663 spec files for the header files specified on the command line, and all
6664 header files needed by these files transitively. For example:
6667 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
6671 will generate, under GNU/Linux, the following files: @code{time_h.ads},
6672 @code{bits_time_h.ads}, @code{stddef_h.ads}, @code{bits_types_h.ads} which
6673 correspond to the files @code{/usr/include/time.h},
6674 @code{/usr/include/bits/time.h}, etc..., and will then compile these Ada specs
6677 The @code{-C} switch tells @code{gcc} to extract comments from headers,
6678 and will attempt to generate corresponding Ada comments.
6680 If you want to generate a single Ada file and not the transitive closure, you
6681 can use instead the @code{-fdump-ada-spec-slim} switch.
6683 You can optionally specify a parent unit, of which all generated units will
6684 be children, using @code{-fada-spec-parent=@emph{unit}}.
6686 Note that we recommend when possible to use the @emph{g++} driver to
6687 generate bindings, even for most C headers, since this will in general
6688 generate better Ada specs. For generating bindings for C++ headers, it is
6689 mandatory to use the @emph{g++} command, or @emph{gcc -x c++} which
6690 is equivalent in this case. If @emph{g++} cannot work on your C headers
6691 because of incompatibilities between C and C++, then you can fallback to
6694 For an example of better bindings generated from the C++ front-end,
6695 the name of the parameters (when available) are actually ignored by the C
6696 front-end. Consider the following C header:
6699 extern void foo (int variable);
6702 with the C front-end, @code{variable} is ignored, and the above is handled as:
6705 extern void foo (int);
6708 generating a generic:
6711 procedure foo (param1 : int);
6714 with the C++ front-end, the name is available, and we generate:
6717 procedure foo (variable : int);
6720 In some cases, the generated bindings will be more complete or more meaningful
6721 when defining some macros, which you can do via the @code{-D} switch. This
6722 is for example the case with @code{Xlib.h} under GNU/Linux:
6725 $ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
6728 The above will generate more complete bindings than a straight call without
6729 the @code{-DXLIB_ILLEGAL_ACCESS} switch.
6731 In other cases, it is not possible to parse a header file in a stand-alone
6732 manner, because other include files need to be included first. In this
6733 case, the solution is to create a small header file including the needed
6734 @code{#include} and possible @code{#define} directives. For example, to
6735 generate Ada bindings for @code{readline/readline.h}, you need to first
6736 include @code{stdio.h}, so you can create a file with the following two
6737 lines in e.g. @code{readline1.h}:
6741 #include <readline/readline.h>
6744 and then generate Ada bindings from this file:
6747 $ g++ -c -fdump-ada-spec readline1.h
6750 @node Generating Bindings for C++ Headers,Switches,Running the Binding Generator,Generating Ada Bindings for C and C++ headers
6751 @anchor{gnat_ugn/the_gnat_compilation_model id72}@anchor{c6}@anchor{gnat_ugn/the_gnat_compilation_model generating-bindings-for-c-headers}@anchor{c7}
6752 @subsubsection Generating Bindings for C++ Headers
6755 Generating bindings for C++ headers is done using the same options, always
6756 with the @emph{g++} compiler. Note that generating Ada spec from C++ headers is a
6757 much more complex job and support for C++ headers is much more limited that
6758 support for C headers. As a result, you will need to modify the resulting
6759 bindings by hand more extensively when using C++ headers.
6761 In this mode, C++ classes will be mapped to Ada tagged types, constructors
6762 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
6763 multiple inheritance of abstract classes will be mapped to Ada interfaces
6764 (see the @emph{Interfacing to C++} section in the @cite{GNAT Reference Manual}
6765 for additional information on interfacing to C++).
6767 For example, given the following C++ header file:
6772 virtual int Number_Of_Teeth () = 0;
6777 virtual void Set_Owner (char* Name) = 0;
6783 virtual void Set_Age (int New_Age);
6786 class Dog : Animal, Carnivore, Domestic @{
6791 virtual int Number_Of_Teeth ();
6792 virtual void Set_Owner (char* Name);
6798 The corresponding Ada code is generated:
6801 package Class_Carnivore is
6802 type Carnivore is limited interface;
6803 pragma Import (CPP, Carnivore);
6805 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
6807 use Class_Carnivore;
6809 package Class_Domestic is
6810 type Domestic is limited interface;
6811 pragma Import (CPP, Domestic);
6814 (this : access Domestic;
6815 Name : Interfaces.C.Strings.chars_ptr) is abstract;
6819 package Class_Animal is
6820 type Animal is tagged limited record
6821 Age_Count : aliased int;
6823 pragma Import (CPP, Animal);
6825 procedure Set_Age (this : access Animal; New_Age : int);
6826 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
6830 package Class_Dog is
6831 type Dog is new Animal and Carnivore and Domestic with record
6832 Tooth_Count : aliased int;
6833 Owner : Interfaces.C.Strings.chars_ptr;
6835 pragma Import (CPP, Dog);
6837 function Number_Of_Teeth (this : access Dog) return int;
6838 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
6841 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
6842 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
6844 function New_Dog return Dog;
6845 pragma CPP_Constructor (New_Dog);
6846 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
6851 @node Switches,,Generating Bindings for C++ Headers,Generating Ada Bindings for C and C++ headers
6852 @anchor{gnat_ugn/the_gnat_compilation_model switches}@anchor{c8}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-ada-binding-generation}@anchor{c9}
6853 @subsubsection Switches
6856 @geindex -fdump-ada-spec (gcc)
6861 @item @code{-fdump-ada-spec}
6863 Generate Ada spec files for the given header files transitively (including
6864 all header files that these headers depend upon).
6867 @geindex -fdump-ada-spec-slim (gcc)
6872 @item @code{-fdump-ada-spec-slim}
6874 Generate Ada spec files for the header files specified on the command line
6878 @geindex -fada-spec-parent (gcc)
6883 @item @code{-fada-spec-parent=@emph{unit}}
6885 Specifies that all files generated by @code{-fdump-ada-spec} are
6886 to be child units of the specified parent unit.
6896 Extract comments from headers and generate Ada comments in the Ada spec files.
6899 @node Generating C Headers for Ada Specifications,,Generating Ada Bindings for C and C++ headers,Mixed Language Programming
6900 @anchor{gnat_ugn/the_gnat_compilation_model generating-c-headers-for-ada-specifications}@anchor{ca}@anchor{gnat_ugn/the_gnat_compilation_model id73}@anchor{cb}
6901 @subsection Generating C Headers for Ada Specifications
6904 @geindex Binding generation (for Ada specs)
6906 @geindex C headers (binding generation)
6908 GNAT includes a C header generator for Ada specifications which supports
6909 Ada types that have a direct mapping to C types. This includes in particular
6925 Composition of the above types
6928 Constant declarations
6934 Subprogram declarations
6938 * Running the C Header Generator::
6942 @node Running the C Header Generator,,,Generating C Headers for Ada Specifications
6943 @anchor{gnat_ugn/the_gnat_compilation_model running-the-c-header-generator}@anchor{cc}
6944 @subsubsection Running the C Header Generator
6947 The C header generator is part of the GNAT compiler and can be invoked via
6948 the @code{-gnatceg} combination of switches, which will generate a @code{.h}
6949 file corresponding to the given input file (Ada spec or body). Note that
6950 only spec files are processed in any case, so giving a spec or a body file
6951 as input is equivalent. For example:
6954 $ gcc -c -gnatceg pack1.ads
6957 will generate a self-contained file called @code{pack1.h} including
6958 common definitions from the Ada Standard package, followed by the
6959 definitions included in @code{pack1.ads}, as well as all the other units
6960 withed by this file.
6962 For instance, given the following Ada files:
6966 type Int is range 1 .. 10;
6975 Field1, Field2 : Pack2.Int;
6978 Global : Rec := (1, 2);
6980 procedure Proc1 (R : Rec);
6981 procedure Proc2 (R : in out Rec);
6985 The above @code{gcc} command will generate the following @code{pack1.h} file:
6988 /* Standard definitions skipped */
6991 typedef short_short_integer pack2__TintB;
6992 typedef pack2__TintB pack2__int;
6993 #endif /* PACK2_ADS */
6997 typedef struct _pack1__rec @{
7001 extern pack1__rec pack1__global;
7002 extern void pack1__proc1(const pack1__rec r);
7003 extern void pack1__proc2(pack1__rec *r);
7004 #endif /* PACK1_ADS */
7007 You can then @code{include} @code{pack1.h} from a C source file and use the types,
7008 call subprograms, reference objects, and constants.
7010 @node GNAT and Other Compilation Models,Using GNAT Files with External Tools,Mixed Language Programming,The GNAT Compilation Model
7011 @anchor{gnat_ugn/the_gnat_compilation_model id74}@anchor{cd}@anchor{gnat_ugn/the_gnat_compilation_model gnat-and-other-compilation-models}@anchor{45}
7012 @section GNAT and Other Compilation Models
7015 This section compares the GNAT model with the approaches taken in
7016 other environents, first the C/C++ model and then the mechanism that
7017 has been used in other Ada systems, in particular those traditionally
7021 * Comparison between GNAT and C/C++ Compilation Models::
7022 * Comparison between GNAT and Conventional Ada Library Models::
7026 @node Comparison between GNAT and C/C++ Compilation Models,Comparison between GNAT and Conventional Ada Library Models,,GNAT and Other Compilation Models
7027 @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-c-c-compilation-models}@anchor{ce}@anchor{gnat_ugn/the_gnat_compilation_model id75}@anchor{cf}
7028 @subsection Comparison between GNAT and C/C++ Compilation Models
7031 The GNAT model of compilation is close to the C and C++ models. You can
7032 think of Ada specs as corresponding to header files in C. As in C, you
7033 don't need to compile specs; they are compiled when they are used. The
7034 Ada @emph{with} is similar in effect to the @code{#include} of a C
7037 One notable difference is that, in Ada, you may compile specs separately
7038 to check them for semantic and syntactic accuracy. This is not always
7039 possible with C headers because they are fragments of programs that have
7040 less specific syntactic or semantic rules.
7042 The other major difference is the requirement for running the binder,
7043 which performs two important functions. First, it checks for
7044 consistency. In C or C++, the only defense against assembling
7045 inconsistent programs lies outside the compiler, in a makefile, for
7046 example. The binder satisfies the Ada requirement that it be impossible
7047 to construct an inconsistent program when the compiler is used in normal
7050 @geindex Elaboration order control
7052 The other important function of the binder is to deal with elaboration
7053 issues. There are also elaboration issues in C++ that are handled
7054 automatically. This automatic handling has the advantage of being
7055 simpler to use, but the C++ programmer has no control over elaboration.
7056 Where @code{gnatbind} might complain there was no valid order of
7057 elaboration, a C++ compiler would simply construct a program that
7058 malfunctioned at run time.
7060 @node Comparison between GNAT and Conventional Ada Library Models,,Comparison between GNAT and C/C++ Compilation Models,GNAT and Other Compilation Models
7061 @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-conventional-ada-library-models}@anchor{d0}@anchor{gnat_ugn/the_gnat_compilation_model id76}@anchor{d1}
7062 @subsection Comparison between GNAT and Conventional Ada Library Models
7065 This section is intended for Ada programmers who have
7066 used an Ada compiler implementing the traditional Ada library
7067 model, as described in the Ada Reference Manual.
7069 @geindex GNAT library
7071 In GNAT, there is no 'library' in the normal sense. Instead, the set of
7072 source files themselves acts as the library. Compiling Ada programs does
7073 not generate any centralized information, but rather an object file and
7074 a ALI file, which are of interest only to the binder and linker.
7075 In a traditional system, the compiler reads information not only from
7076 the source file being compiled, but also from the centralized library.
7077 This means that the effect of a compilation depends on what has been
7078 previously compiled. In particular:
7084 When a unit is @emph{with}ed, the unit seen by the compiler corresponds
7085 to the version of the unit most recently compiled into the library.
7088 Inlining is effective only if the necessary body has already been
7089 compiled into the library.
7092 Compiling a unit may obsolete other units in the library.
7095 In GNAT, compiling one unit never affects the compilation of any other
7096 units because the compiler reads only source files. Only changes to source
7097 files can affect the results of a compilation. In particular:
7103 When a unit is @emph{with}ed, the unit seen by the compiler corresponds
7104 to the source version of the unit that is currently accessible to the
7110 Inlining requires the appropriate source files for the package or
7111 subprogram bodies to be available to the compiler. Inlining is always
7112 effective, independent of the order in which units are compiled.
7115 Compiling a unit never affects any other compilations. The editing of
7116 sources may cause previous compilations to be out of date if they
7117 depended on the source file being modified.
7120 The most important result of these differences is that order of compilation
7121 is never significant in GNAT. There is no situation in which one is
7122 required to do one compilation before another. What shows up as order of
7123 compilation requirements in the traditional Ada library becomes, in
7124 GNAT, simple source dependencies; in other words, there is only a set
7125 of rules saying what source files must be present when a file is
7128 @node Using GNAT Files with External Tools,,GNAT and Other Compilation Models,The GNAT Compilation Model
7129 @anchor{gnat_ugn/the_gnat_compilation_model using-gnat-files-with-external-tools}@anchor{1a}@anchor{gnat_ugn/the_gnat_compilation_model id77}@anchor{d2}
7130 @section Using GNAT Files with External Tools
7133 This section explains how files that are produced by GNAT may be
7134 used with tools designed for other languages.
7137 * Using Other Utility Programs with GNAT::
7138 * The External Symbol Naming Scheme of GNAT::
7142 @node Using Other Utility Programs with GNAT,The External Symbol Naming Scheme of GNAT,,Using GNAT Files with External Tools
7143 @anchor{gnat_ugn/the_gnat_compilation_model using-other-utility-programs-with-gnat}@anchor{d3}@anchor{gnat_ugn/the_gnat_compilation_model id78}@anchor{d4}
7144 @subsection Using Other Utility Programs with GNAT
7147 The object files generated by GNAT are in standard system format and in
7148 particular the debugging information uses this format. This means
7149 programs generated by GNAT can be used with existing utilities that
7150 depend on these formats.
7152 In general, any utility program that works with C will also often work with
7153 Ada programs generated by GNAT. This includes software utilities such as
7154 gprof (a profiling program), gdb (the FSF debugger), and utilities such
7157 @node The External Symbol Naming Scheme of GNAT,,Using Other Utility Programs with GNAT,Using GNAT Files with External Tools
7158 @anchor{gnat_ugn/the_gnat_compilation_model the-external-symbol-naming-scheme-of-gnat}@anchor{d5}@anchor{gnat_ugn/the_gnat_compilation_model id79}@anchor{d6}
7159 @subsection The External Symbol Naming Scheme of GNAT
7162 In order to interpret the output from GNAT, when using tools that are
7163 originally intended for use with other languages, it is useful to
7164 understand the conventions used to generate link names from the Ada
7167 All link names are in all lowercase letters. With the exception of library
7168 procedure names, the mechanism used is simply to use the full expanded
7169 Ada name with dots replaced by double underscores. For example, suppose
7170 we have the following package spec:
7178 @geindex pragma Export
7180 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
7181 the corresponding link name is @code{qrs__mn}.
7182 Of course if a @code{pragma Export} is used this may be overridden:
7187 pragma Export (Var1, C, External_Name => "var1_name");
7189 pragma Export (Var2, C, Link_Name => "var2_link_name");
7193 In this case, the link name for @code{Var1} is whatever link name the
7194 C compiler would assign for the C function @code{var1_name}. This typically
7195 would be either @code{var1_name} or @code{_var1_name}, depending on operating
7196 system conventions, but other possibilities exist. The link name for
7197 @code{Var2} is @code{var2_link_name}, and this is not operating system
7200 One exception occurs for library level procedures. A potential ambiguity
7201 arises between the required name @code{_main} for the C main program,
7202 and the name we would otherwise assign to an Ada library level procedure
7203 called @code{Main} (which might well not be the main program).
7205 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
7206 names. So if we have a library level procedure such as:
7209 procedure Hello (S : String);
7212 the external name of this procedure will be @code{_ada_hello}.
7214 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
7216 @node Building Executable Programs with GNAT,GNAT Utility Programs,The GNAT Compilation Model,Top
7217 @anchor{gnat_ugn/building_executable_programs_with_gnat building-executable-programs-with-gnat}@anchor{a}@anchor{gnat_ugn/building_executable_programs_with_gnat doc}@anchor{d7}@anchor{gnat_ugn/building_executable_programs_with_gnat id1}@anchor{d8}
7218 @chapter Building Executable Programs with GNAT
7221 This chapter describes first the gnatmake tool
7222 (@ref{1b,,Building with gnatmake}),
7223 which automatically determines the set of sources
7224 needed by an Ada compilation unit and executes the necessary
7225 (re)compilations, binding and linking.
7226 It also explains how to use each tool individually: the
7227 compiler (gcc, see @ref{1c,,Compiling with gcc}),
7228 binder (gnatbind, see @ref{1d,,Binding with gnatbind}),
7229 and linker (gnatlink, see @ref{1e,,Linking with gnatlink})
7230 to build executable programs.
7231 Finally, this chapter provides examples of
7232 how to make use of the general GNU make mechanism
7233 in a GNAT context (see @ref{1f,,Using the GNU make Utility}).
7237 * Building with gnatmake::
7238 * Compiling with gcc::
7239 * Compiler Switches::
7241 * Binding with gnatbind::
7242 * Linking with gnatlink::
7243 * Using the GNU make Utility::
7247 @node Building with gnatmake,Compiling with gcc,,Building Executable Programs with GNAT
7248 @anchor{gnat_ugn/building_executable_programs_with_gnat the-gnat-make-program-gnatmake}@anchor{1b}@anchor{gnat_ugn/building_executable_programs_with_gnat building-with-gnatmake}@anchor{d9}
7249 @section Building with @code{gnatmake}
7254 A typical development cycle when working on an Ada program consists of
7255 the following steps:
7261 Edit some sources to fix bugs;
7267 Compile all sources affected;
7270 Rebind and relink; and
7276 @geindex Dependency rules (compilation)
7278 The third step in particular can be tricky, because not only do the modified
7279 files have to be compiled, but any files depending on these files must also be
7280 recompiled. The dependency rules in Ada can be quite complex, especially
7281 in the presence of overloading, @code{use} clauses, generics and inlined
7284 @code{gnatmake} automatically takes care of the third and fourth steps
7285 of this process. It determines which sources need to be compiled,
7286 compiles them, and binds and links the resulting object files.
7288 Unlike some other Ada make programs, the dependencies are always
7289 accurately recomputed from the new sources. The source based approach of
7290 the GNAT compilation model makes this possible. This means that if
7291 changes to the source program cause corresponding changes in
7292 dependencies, they will always be tracked exactly correctly by
7295 Note that for advanced forms of project structure, we recommend creating
7296 a project file as explained in the @emph{GNAT_Project_Manager} chapter in the
7297 @emph{GPRbuild User's Guide}, and using the
7298 @code{gprbuild} tool which supports building with project files and works similarly
7302 * Running gnatmake::
7303 * Switches for gnatmake::
7304 * Mode Switches for gnatmake::
7305 * Notes on the Command Line::
7306 * How gnatmake Works::
7307 * Examples of gnatmake Usage::
7311 @node Running gnatmake,Switches for gnatmake,,Building with gnatmake
7312 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatmake}@anchor{da}@anchor{gnat_ugn/building_executable_programs_with_gnat id2}@anchor{db}
7313 @subsection Running @code{gnatmake}
7316 The usual form of the @code{gnatmake} command is
7319 $ gnatmake [<switches>] <file_name> [<file_names>] [<mode_switches>]
7322 The only required argument is one @code{file_name}, which specifies
7323 a compilation unit that is a main program. Several @code{file_names} can be
7324 specified: this will result in several executables being built.
7325 If @code{switches} are present, they can be placed before the first
7326 @code{file_name}, between @code{file_names} or after the last @code{file_name}.
7327 If @code{mode_switches} are present, they must always be placed after
7328 the last @code{file_name} and all @code{switches}.
7330 If you are using standard file extensions (@code{.adb} and
7331 @code{.ads}), then the
7332 extension may be omitted from the @code{file_name} arguments. However, if
7333 you are using non-standard extensions, then it is required that the
7334 extension be given. A relative or absolute directory path can be
7335 specified in a @code{file_name}, in which case, the input source file will
7336 be searched for in the specified directory only. Otherwise, the input
7337 source file will first be searched in the directory where
7338 @code{gnatmake} was invoked and if it is not found, it will be search on
7339 the source path of the compiler as described in
7340 @ref{89,,Search Paths and the Run-Time Library (RTL)}.
7342 All @code{gnatmake} output (except when you specify @code{-M}) is sent to
7343 @code{stderr}. The output produced by the
7344 @code{-M} switch is sent to @code{stdout}.
7346 @node Switches for gnatmake,Mode Switches for gnatmake,Running gnatmake,Building with gnatmake
7347 @anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatmake}@anchor{dc}@anchor{gnat_ugn/building_executable_programs_with_gnat id3}@anchor{dd}
7348 @subsection Switches for @code{gnatmake}
7351 You may specify any of the following switches to @code{gnatmake}:
7353 @geindex --version (gnatmake)
7358 @item @code{--version}
7360 Display Copyright and version, then exit disregarding all other options.
7363 @geindex --help (gnatmake)
7370 If @code{--version} was not used, display usage, then exit disregarding
7374 @geindex --GCC=compiler_name (gnatmake)
7379 @item @code{--GCC=@emph{compiler_name}}
7381 Program used for compiling. The default is @code{gcc}. You need to use
7382 quotes around @code{compiler_name} if @code{compiler_name} contains
7383 spaces or other separator characters.
7384 As an example @code{--GCC="foo -x -y"}
7385 will instruct @code{gnatmake} to use @code{foo -x -y} as your
7386 compiler. A limitation of this syntax is that the name and path name of
7387 the executable itself must not include any embedded spaces. Note that
7388 switch @code{-c} is always inserted after your command name. Thus in the
7389 above example the compiler command that will be used by @code{gnatmake}
7390 will be @code{foo -c -x -y}. If several @code{--GCC=compiler_name} are
7391 used, only the last @code{compiler_name} is taken into account. However,
7392 all the additional switches are also taken into account. Thus,
7393 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
7394 @code{--GCC="bar -x -y -z -t"}.
7397 @geindex --GNATBIND=binder_name (gnatmake)
7402 @item @code{--GNATBIND=@emph{binder_name}}
7404 Program used for binding. The default is @code{gnatbind}. You need to
7405 use quotes around @code{binder_name} if @code{binder_name} contains spaces
7406 or other separator characters.
7407 As an example @code{--GNATBIND="bar -x -y"}
7408 will instruct @code{gnatmake} to use @code{bar -x -y} as your
7409 binder. Binder switches that are normally appended by @code{gnatmake}
7410 to @code{gnatbind} are now appended to the end of @code{bar -x -y}.
7411 A limitation of this syntax is that the name and path name of the executable
7412 itself must not include any embedded spaces.
7415 @geindex --GNATLINK=linker_name (gnatmake)
7420 @item @code{--GNATLINK=@emph{linker_name}}
7422 Program used for linking. The default is @code{gnatlink}. You need to
7423 use quotes around @code{linker_name} if @code{linker_name} contains spaces
7424 or other separator characters.
7425 As an example @code{--GNATLINK="lan -x -y"}
7426 will instruct @code{gnatmake} to use @code{lan -x -y} as your
7427 linker. Linker switches that are normally appended by @code{gnatmake} to
7428 @code{gnatlink} are now appended to the end of @code{lan -x -y}.
7429 A limitation of this syntax is that the name and path name of the executable
7430 itself must not include any embedded spaces.
7432 @item @code{--create-map-file}
7434 When linking an executable, create a map file. The name of the map file
7435 has the same name as the executable with extension ".map".
7437 @item @code{--create-map-file=@emph{mapfile}}
7439 When linking an executable, create a map file with the specified name.
7442 @geindex --create-missing-dirs (gnatmake)
7447 @item @code{--create-missing-dirs}
7449 When using project files (@code{-P@emph{project}}), automatically create
7450 missing object directories, library directories and exec
7453 @item @code{--single-compile-per-obj-dir}
7455 Disallow simultaneous compilations in the same object directory when
7456 project files are used.
7458 @item @code{--subdirs=@emph{subdir}}
7460 Actual object directory of each project file is the subdirectory subdir of the
7461 object directory specified or defaulted in the project file.
7463 @item @code{--unchecked-shared-lib-imports}
7465 By default, shared library projects are not allowed to import static library
7466 projects. When this switch is used on the command line, this restriction is
7469 @item @code{--source-info=@emph{source info file}}
7471 Specify a source info file. This switch is active only when project files
7472 are used. If the source info file is specified as a relative path, then it is
7473 relative to the object directory of the main project. If the source info file
7474 does not exist, then after the Project Manager has successfully parsed and
7475 processed the project files and found the sources, it creates the source info
7476 file. If the source info file already exists and can be read successfully,
7477 then the Project Manager will get all the needed information about the sources
7478 from the source info file and will not look for them. This reduces the time
7479 to process the project files, especially when looking for sources that take a
7480 long time. If the source info file exists but cannot be parsed successfully,
7481 the Project Manager will attempt to recreate it. If the Project Manager fails
7482 to create the source info file, a message is issued, but gnatmake does not
7483 fail. @code{gnatmake} "trusts" the source info file. This means that
7484 if the source files have changed (addition, deletion, moving to a different
7485 source directory), then the source info file need to be deleted and recreated.
7488 @geindex -a (gnatmake)
7495 Consider all files in the make process, even the GNAT internal system
7496 files (for example, the predefined Ada library files), as well as any
7497 locked files. Locked files are files whose ALI file is write-protected.
7499 @code{gnatmake} does not check these files,
7500 because the assumption is that the GNAT internal files are properly up
7501 to date, and also that any write protected ALI files have been properly
7502 installed. Note that if there is an installation problem, such that one
7503 of these files is not up to date, it will be properly caught by the
7505 You may have to specify this switch if you are working on GNAT
7506 itself. The switch @code{-a} is also useful
7507 in conjunction with @code{-f}
7508 if you need to recompile an entire application,
7509 including run-time files, using special configuration pragmas,
7510 such as a @code{Normalize_Scalars} pragma.
7513 @code{gnatmake -a} compiles all GNAT
7515 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
7518 @geindex -b (gnatmake)
7525 Bind only. Can be combined with @code{-c} to do
7526 compilation and binding, but no link.
7527 Can be combined with @code{-l}
7528 to do binding and linking. When not combined with
7530 all the units in the closure of the main program must have been previously
7531 compiled and must be up to date. The root unit specified by @code{file_name}
7532 may be given without extension, with the source extension or, if no GNAT
7533 Project File is specified, with the ALI file extension.
7536 @geindex -c (gnatmake)
7543 Compile only. Do not perform binding, except when @code{-b}
7544 is also specified. Do not perform linking, except if both
7546 @code{-l} are also specified.
7547 If the root unit specified by @code{file_name} is not a main unit, this is the
7548 default. Otherwise @code{gnatmake} will attempt binding and linking
7549 unless all objects are up to date and the executable is more recent than
7553 @geindex -C (gnatmake)
7560 Use a temporary mapping file. A mapping file is a way to communicate
7561 to the compiler two mappings: from unit names to file names (without
7562 any directory information) and from file names to path names (with
7563 full directory information). A mapping file can make the compiler's
7564 file searches faster, especially if there are many source directories,
7565 or the sources are read over a slow network connection. If
7566 @code{-P} is used, a mapping file is always used, so
7567 @code{-C} is unnecessary; in this case the mapping file
7568 is initially populated based on the project file. If
7569 @code{-C} is used without
7571 the mapping file is initially empty. Each invocation of the compiler
7572 will add any newly accessed sources to the mapping file.
7575 @geindex -C= (gnatmake)
7580 @item @code{-C=@emph{file}}
7582 Use a specific mapping file. The file, specified as a path name (absolute or
7583 relative) by this switch, should already exist, otherwise the switch is
7584 ineffective. The specified mapping file will be communicated to the compiler.
7585 This switch is not compatible with a project file
7586 (-P`file`) or with multiple compiling processes
7587 (-jnnn, when nnn is greater than 1).
7590 @geindex -d (gnatmake)
7597 Display progress for each source, up to date or not, as a single line:
7600 completed x out of y (zz%)
7603 If the file needs to be compiled this is displayed after the invocation of
7604 the compiler. These lines are displayed even in quiet output mode.
7607 @geindex -D (gnatmake)
7612 @item @code{-D @emph{dir}}
7614 Put all object files and ALI file in directory @code{dir}.
7615 If the @code{-D} switch is not used, all object files
7616 and ALI files go in the current working directory.
7618 This switch cannot be used when using a project file.
7621 @geindex -eI (gnatmake)
7626 @item @code{-eI@emph{nnn}}
7628 Indicates that the main source is a multi-unit source and the rank of the unit
7629 in the source file is nnn. nnn needs to be a positive number and a valid
7630 index in the source. This switch cannot be used when @code{gnatmake} is
7631 invoked for several mains.
7634 @geindex -eL (gnatmake)
7636 @geindex symbolic links
7643 Follow all symbolic links when processing project files.
7644 This should be used if your project uses symbolic links for files or
7645 directories, but is not needed in other cases.
7647 @geindex naming scheme
7649 This also assumes that no directory matches the naming scheme for files (for
7650 instance that you do not have a directory called "sources.ads" when using the
7651 default GNAT naming scheme).
7653 When you do not have to use this switch (i.e., by default), gnatmake is able to
7654 save a lot of system calls (several per source file and object file), which
7655 can result in a significant speed up to load and manipulate a project file,
7656 especially when using source files from a remote system.
7659 @geindex -eS (gnatmake)
7666 Output the commands for the compiler, the binder and the linker
7668 instead of standard error.
7671 @geindex -f (gnatmake)
7678 Force recompilations. Recompile all sources, even though some object
7679 files may be up to date, but don't recompile predefined or GNAT internal
7680 files or locked files (files with a write-protected ALI file),
7681 unless the @code{-a} switch is also specified.
7684 @geindex -F (gnatmake)
7691 When using project files, if some errors or warnings are detected during
7692 parsing and verbose mode is not in effect (no use of switch
7693 -v), then error lines start with the full path name of the project
7694 file, rather than its simple file name.
7697 @geindex -g (gnatmake)
7704 Enable debugging. This switch is simply passed to the compiler and to the
7708 @geindex -i (gnatmake)
7715 In normal mode, @code{gnatmake} compiles all object files and ALI files
7716 into the current directory. If the @code{-i} switch is used,
7717 then instead object files and ALI files that already exist are overwritten
7718 in place. This means that once a large project is organized into separate
7719 directories in the desired manner, then @code{gnatmake} will automatically
7720 maintain and update this organization. If no ALI files are found on the
7721 Ada object path (see @ref{89,,Search Paths and the Run-Time Library (RTL)}),
7722 the new object and ALI files are created in the
7723 directory containing the source being compiled. If another organization
7724 is desired, where objects and sources are kept in different directories,
7725 a useful technique is to create dummy ALI files in the desired directories.
7726 When detecting such a dummy file, @code{gnatmake} will be forced to
7727 recompile the corresponding source file, and it will be put the resulting
7728 object and ALI files in the directory where it found the dummy file.
7731 @geindex -j (gnatmake)
7733 @geindex Parallel make
7738 @item @code{-j@emph{n}}
7740 Use @code{n} processes to carry out the (re)compilations. On a multiprocessor
7741 machine compilations will occur in parallel. If @code{n} is 0, then the
7742 maximum number of parallel compilations is the number of core processors
7743 on the platform. In the event of compilation errors, messages from various
7744 compilations might get interspersed (but @code{gnatmake} will give you the
7745 full ordered list of failing compiles at the end). If this is problematic,
7746 rerun the make process with n set to 1 to get a clean list of messages.
7749 @geindex -k (gnatmake)
7756 Keep going. Continue as much as possible after a compilation error. To
7757 ease the programmer's task in case of compilation errors, the list of
7758 sources for which the compile fails is given when @code{gnatmake}
7761 If @code{gnatmake} is invoked with several @code{file_names} and with this
7762 switch, if there are compilation errors when building an executable,
7763 @code{gnatmake} will not attempt to build the following executables.
7766 @geindex -l (gnatmake)
7773 Link only. Can be combined with @code{-b} to binding
7774 and linking. Linking will not be performed if combined with
7776 but not with @code{-b}.
7777 When not combined with @code{-b}
7778 all the units in the closure of the main program must have been previously
7779 compiled and must be up to date, and the main program needs to have been bound.
7780 The root unit specified by @code{file_name}
7781 may be given without extension, with the source extension or, if no GNAT
7782 Project File is specified, with the ALI file extension.
7785 @geindex -m (gnatmake)
7792 Specify that the minimum necessary amount of recompilations
7793 be performed. In this mode @code{gnatmake} ignores time
7794 stamp differences when the only
7795 modifications to a source file consist in adding/removing comments,
7796 empty lines, spaces or tabs. This means that if you have changed the
7797 comments in a source file or have simply reformatted it, using this
7798 switch will tell @code{gnatmake} not to recompile files that depend on it
7799 (provided other sources on which these files depend have undergone no
7800 semantic modifications). Note that the debugging information may be
7801 out of date with respect to the sources if the @code{-m} switch causes
7802 a compilation to be switched, so the use of this switch represents a
7803 trade-off between compilation time and accurate debugging information.
7806 @geindex Dependencies
7807 @geindex producing list
7809 @geindex -M (gnatmake)
7816 Check if all objects are up to date. If they are, output the object
7817 dependences to @code{stdout} in a form that can be directly exploited in
7818 a @code{Makefile}. By default, each source file is prefixed with its
7819 (relative or absolute) directory name. This name is whatever you
7820 specified in the various @code{-aI}
7821 and @code{-I} switches. If you use
7822 @code{gnatmake -M} @code{-q}
7823 (see below), only the source file names,
7824 without relative paths, are output. If you just specify the @code{-M}
7825 switch, dependencies of the GNAT internal system files are omitted. This
7826 is typically what you want. If you also specify
7827 the @code{-a} switch,
7828 dependencies of the GNAT internal files are also listed. Note that
7829 dependencies of the objects in external Ada libraries (see
7830 switch @code{-aL@emph{dir}} in the following list)
7834 @geindex -n (gnatmake)
7841 Don't compile, bind, or link. Checks if all objects are up to date.
7842 If they are not, the full name of the first file that needs to be
7843 recompiled is printed.
7844 Repeated use of this option, followed by compiling the indicated source
7845 file, will eventually result in recompiling all required units.
7848 @geindex -o (gnatmake)
7853 @item @code{-o @emph{exec_name}}
7855 Output executable name. The name of the final executable program will be
7856 @code{exec_name}. If the @code{-o} switch is omitted the default
7857 name for the executable will be the name of the input file in appropriate form
7858 for an executable file on the host system.
7860 This switch cannot be used when invoking @code{gnatmake} with several
7864 @geindex -p (gnatmake)
7871 Same as @code{--create-missing-dirs}
7874 @geindex -P (gnatmake)
7879 @item @code{-P@emph{project}}
7881 Use project file @code{project}. Only one such switch can be used.
7885 @c :ref:`gnatmake_and_Project_Files`.
7887 @geindex -q (gnatmake)
7894 Quiet. When this flag is not set, the commands carried out by
7895 @code{gnatmake} are displayed.
7898 @geindex -s (gnatmake)
7905 Recompile if compiler switches have changed since last compilation.
7906 All compiler switches but -I and -o are taken into account in the
7908 orders between different 'first letter' switches are ignored, but
7909 orders between same switches are taken into account. For example,
7910 @code{-O -O2} is different than @code{-O2 -O}, but @code{-g -O}
7911 is equivalent to @code{-O -g}.
7913 This switch is recommended when Integrated Preprocessing is used.
7916 @geindex -u (gnatmake)
7923 Unique. Recompile at most the main files. It implies -c. Combined with
7924 -f, it is equivalent to calling the compiler directly. Note that using
7925 -u with a project file and no main has a special meaning.
7929 @c (See :ref:`Project_Files_and_Main_Subprograms`.)
7931 @geindex -U (gnatmake)
7938 When used without a project file or with one or several mains on the command
7939 line, is equivalent to -u. When used with a project file and no main
7940 on the command line, all sources of all project files are checked and compiled
7941 if not up to date, and libraries are rebuilt, if necessary.
7944 @geindex -v (gnatmake)
7951 Verbose. Display the reason for all recompilations @code{gnatmake}
7952 decides are necessary, with the highest verbosity level.
7955 @geindex -vl (gnatmake)
7962 Verbosity level Low. Display fewer lines than in verbosity Medium.
7965 @geindex -vm (gnatmake)
7972 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
7975 @geindex -vm (gnatmake)
7982 Verbosity level High. Equivalent to -v.
7984 @item @code{-vP@emph{x}}
7986 Indicate the verbosity of the parsing of GNAT project files.
7987 See @ref{de,,Switches Related to Project Files}.
7990 @geindex -x (gnatmake)
7997 Indicate that sources that are not part of any Project File may be compiled.
7998 Normally, when using Project Files, only sources that are part of a Project
7999 File may be compile. When this switch is used, a source outside of all Project
8000 Files may be compiled. The ALI file and the object file will be put in the
8001 object directory of the main Project. The compilation switches used will only
8002 be those specified on the command line. Even when
8003 @code{-x} is used, mains specified on the
8004 command line need to be sources of a project file.
8006 @item @code{-X@emph{name}=@emph{value}}
8008 Indicate that external variable @code{name} has the value @code{value}.
8009 The Project Manager will use this value for occurrences of
8010 @code{external(name)} when parsing the project file.
8011 @ref{de,,Switches Related to Project Files}.
8014 @geindex -z (gnatmake)
8021 No main subprogram. Bind and link the program even if the unit name
8022 given on the command line is a package name. The resulting executable
8023 will execute the elaboration routines of the package and its closure,
8024 then the finalization routines.
8027 @subsubheading GCC switches
8030 Any uppercase or multi-character switch that is not a @code{gnatmake} switch
8031 is passed to @code{gcc} (e.g., @code{-O}, @code{-gnato,} etc.)
8033 @subsubheading Source and library search path switches
8036 @geindex -aI (gnatmake)
8041 @item @code{-aI@emph{dir}}
8043 When looking for source files also look in directory @code{dir}.
8044 The order in which source files search is undertaken is
8045 described in @ref{89,,Search Paths and the Run-Time Library (RTL)}.
8048 @geindex -aL (gnatmake)
8053 @item @code{-aL@emph{dir}}
8055 Consider @code{dir} as being an externally provided Ada library.
8056 Instructs @code{gnatmake} to skip compilation units whose @code{.ALI}
8057 files have been located in directory @code{dir}. This allows you to have
8058 missing bodies for the units in @code{dir} and to ignore out of date bodies
8059 for the same units. You still need to specify
8060 the location of the specs for these units by using the switches
8061 @code{-aI@emph{dir}} or @code{-I@emph{dir}}.
8062 Note: this switch is provided for compatibility with previous versions
8063 of @code{gnatmake}. The easier method of causing standard libraries
8064 to be excluded from consideration is to write-protect the corresponding
8068 @geindex -aO (gnatmake)
8073 @item @code{-aO@emph{dir}}
8075 When searching for library and object files, look in directory
8076 @code{dir}. The order in which library files are searched is described in
8077 @ref{8c,,Search Paths for gnatbind}.
8080 @geindex Search paths
8081 @geindex for gnatmake
8083 @geindex -A (gnatmake)
8088 @item @code{-A@emph{dir}}
8090 Equivalent to @code{-aL@emph{dir}} @code{-aI@emph{dir}}.
8092 @geindex -I (gnatmake)
8094 @item @code{-I@emph{dir}}
8096 Equivalent to @code{-aO@emph{dir} -aI@emph{dir}}.
8099 @geindex -I- (gnatmake)
8101 @geindex Source files
8102 @geindex suppressing search
8109 Do not look for source files in the directory containing the source
8110 file named in the command line.
8111 Do not look for ALI or object files in the directory
8112 where @code{gnatmake} was invoked.
8115 @geindex -L (gnatmake)
8117 @geindex Linker libraries
8122 @item @code{-L@emph{dir}}
8124 Add directory @code{dir} to the list of directories in which the linker
8125 will search for libraries. This is equivalent to
8126 @code{-largs} @code{-L@emph{dir}}.
8127 Furthermore, under Windows, the sources pointed to by the libraries path
8128 set in the registry are not searched for.
8131 @geindex -nostdinc (gnatmake)
8136 @item @code{-nostdinc}
8138 Do not look for source files in the system default directory.
8141 @geindex -nostdlib (gnatmake)
8146 @item @code{-nostdlib}
8148 Do not look for library files in the system default directory.
8151 @geindex --RTS (gnatmake)
8156 @item @code{--RTS=@emph{rts-path}}
8158 Specifies the default location of the run-time library. GNAT looks for the
8160 in the following directories, and stops as soon as a valid run-time is found
8161 (@code{adainclude} or @code{ada_source_path}, and @code{adalib} or
8162 @code{ada_object_path} present):
8168 @emph{<current directory>/$rts_path}
8171 @emph{<default-search-dir>/$rts_path}
8174 @emph{<default-search-dir>/rts-$rts_path}
8177 The selected path is handled like a normal RTS path.
8181 @node Mode Switches for gnatmake,Notes on the Command Line,Switches for gnatmake,Building with gnatmake
8182 @anchor{gnat_ugn/building_executable_programs_with_gnat id4}@anchor{df}@anchor{gnat_ugn/building_executable_programs_with_gnat mode-switches-for-gnatmake}@anchor{e0}
8183 @subsection Mode Switches for @code{gnatmake}
8186 The mode switches (referred to as @code{mode_switches}) allow the
8187 inclusion of switches that are to be passed to the compiler itself, the
8188 binder or the linker. The effect of a mode switch is to cause all
8189 subsequent switches up to the end of the switch list, or up to the next
8190 mode switch, to be interpreted as switches to be passed on to the
8191 designated component of GNAT.
8193 @geindex -cargs (gnatmake)
8198 @item @code{-cargs @emph{switches}}
8200 Compiler switches. Here @code{switches} is a list of switches
8201 that are valid switches for @code{gcc}. They will be passed on to
8202 all compile steps performed by @code{gnatmake}.
8205 @geindex -bargs (gnatmake)
8210 @item @code{-bargs @emph{switches}}
8212 Binder switches. Here @code{switches} is a list of switches
8213 that are valid switches for @code{gnatbind}. They will be passed on to
8214 all bind steps performed by @code{gnatmake}.
8217 @geindex -largs (gnatmake)
8222 @item @code{-largs @emph{switches}}
8224 Linker switches. Here @code{switches} is a list of switches
8225 that are valid switches for @code{gnatlink}. They will be passed on to
8226 all link steps performed by @code{gnatmake}.
8229 @geindex -margs (gnatmake)
8234 @item @code{-margs @emph{switches}}
8236 Make switches. The switches are directly interpreted by @code{gnatmake},
8237 regardless of any previous occurrence of @code{-cargs}, @code{-bargs}
8241 @node Notes on the Command Line,How gnatmake Works,Mode Switches for gnatmake,Building with gnatmake
8242 @anchor{gnat_ugn/building_executable_programs_with_gnat id5}@anchor{e1}@anchor{gnat_ugn/building_executable_programs_with_gnat notes-on-the-command-line}@anchor{e2}
8243 @subsection Notes on the Command Line
8246 This section contains some additional useful notes on the operation
8247 of the @code{gnatmake} command.
8249 @geindex Recompilation (by gnatmake)
8255 If @code{gnatmake} finds no ALI files, it recompiles the main program
8256 and all other units required by the main program.
8257 This means that @code{gnatmake}
8258 can be used for the initial compile, as well as during subsequent steps of
8259 the development cycle.
8262 If you enter @code{gnatmake foo.adb}, where @code{foo}
8263 is a subunit or body of a generic unit, @code{gnatmake} recompiles
8264 @code{foo.adb} (because it finds no ALI) and stops, issuing a
8268 In @code{gnatmake} the switch @code{-I}
8269 is used to specify both source and
8270 library file paths. Use @code{-aI}
8271 instead if you just want to specify
8272 source paths only and @code{-aO}
8273 if you want to specify library paths
8277 @code{gnatmake} will ignore any files whose ALI file is write-protected.
8278 This may conveniently be used to exclude standard libraries from
8279 consideration and in particular it means that the use of the
8280 @code{-f} switch will not recompile these files
8281 unless @code{-a} is also specified.
8284 @code{gnatmake} has been designed to make the use of Ada libraries
8285 particularly convenient. Assume you have an Ada library organized
8286 as follows: @emph{obj-dir} contains the objects and ALI files for
8287 of your Ada compilation units,
8288 whereas @emph{include-dir} contains the
8289 specs of these units, but no bodies. Then to compile a unit
8290 stored in @code{main.adb}, which uses this Ada library you would just type:
8293 $ gnatmake -aI`include-dir` -aL`obj-dir` main
8297 Using @code{gnatmake} along with the @code{-m (minimal recompilation)}
8298 switch provides a mechanism for avoiding unnecessary recompilations. Using
8300 you can update the comments/format of your
8301 source files without having to recompile everything. Note, however, that
8302 adding or deleting lines in a source files may render its debugging
8303 info obsolete. If the file in question is a spec, the impact is rather
8304 limited, as that debugging info will only be useful during the
8305 elaboration phase of your program. For bodies the impact can be more
8306 significant. In all events, your debugger will warn you if a source file
8307 is more recent than the corresponding object, and alert you to the fact
8308 that the debugging information may be out of date.
8311 @node How gnatmake Works,Examples of gnatmake Usage,Notes on the Command Line,Building with gnatmake
8312 @anchor{gnat_ugn/building_executable_programs_with_gnat id6}@anchor{e3}@anchor{gnat_ugn/building_executable_programs_with_gnat how-gnatmake-works}@anchor{e4}
8313 @subsection How @code{gnatmake} Works
8316 Generally @code{gnatmake} automatically performs all necessary
8317 recompilations and you don't need to worry about how it works. However,
8318 it may be useful to have some basic understanding of the @code{gnatmake}
8319 approach and in particular to understand how it uses the results of
8320 previous compilations without incorrectly depending on them.
8322 First a definition: an object file is considered @emph{up to date} if the
8323 corresponding ALI file exists and if all the source files listed in the
8324 dependency section of this ALI file have time stamps matching those in
8325 the ALI file. This means that neither the source file itself nor any
8326 files that it depends on have been modified, and hence there is no need
8327 to recompile this file.
8329 @code{gnatmake} works by first checking if the specified main unit is up
8330 to date. If so, no compilations are required for the main unit. If not,
8331 @code{gnatmake} compiles the main program to build a new ALI file that
8332 reflects the latest sources. Then the ALI file of the main unit is
8333 examined to find all the source files on which the main program depends,
8334 and @code{gnatmake} recursively applies the above procedure on all these
8337 This process ensures that @code{gnatmake} only trusts the dependencies
8338 in an existing ALI file if they are known to be correct. Otherwise it
8339 always recompiles to determine a new, guaranteed accurate set of
8340 dependencies. As a result the program is compiled 'upside down' from what may
8341 be more familiar as the required order of compilation in some other Ada
8342 systems. In particular, clients are compiled before the units on which
8343 they depend. The ability of GNAT to compile in any order is critical in
8344 allowing an order of compilation to be chosen that guarantees that
8345 @code{gnatmake} will recompute a correct set of new dependencies if
8348 When invoking @code{gnatmake} with several @code{file_names}, if a unit is
8349 imported by several of the executables, it will be recompiled at most once.
8351 Note: when using non-standard naming conventions
8352 (@ref{35,,Using Other File Names}), changing through a configuration pragmas
8353 file the version of a source and invoking @code{gnatmake} to recompile may
8354 have no effect, if the previous version of the source is still accessible
8355 by @code{gnatmake}. It may be necessary to use the switch
8358 @node Examples of gnatmake Usage,,How gnatmake Works,Building with gnatmake
8359 @anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatmake-usage}@anchor{e5}@anchor{gnat_ugn/building_executable_programs_with_gnat id7}@anchor{e6}
8360 @subsection Examples of @code{gnatmake} Usage
8366 @item @emph{gnatmake hello.adb}
8368 Compile all files necessary to bind and link the main program
8369 @code{hello.adb} (containing unit @code{Hello}) and bind and link the
8370 resulting object files to generate an executable file @code{hello}.
8372 @item @emph{gnatmake main1 main2 main3}
8374 Compile all files necessary to bind and link the main programs
8375 @code{main1.adb} (containing unit @code{Main1}), @code{main2.adb}
8376 (containing unit @code{Main2}) and @code{main3.adb}
8377 (containing unit @code{Main3}) and bind and link the resulting object files
8378 to generate three executable files @code{main1},
8379 @code{main2} and @code{main3}.
8381 @item @emph{gnatmake -q Main_Unit -cargs -O2 -bargs -l}
8383 Compile all files necessary to bind and link the main program unit
8384 @code{Main_Unit} (from file @code{main_unit.adb}). All compilations will
8385 be done with optimization level 2 and the order of elaboration will be
8386 listed by the binder. @code{gnatmake} will operate in quiet mode, not
8387 displaying commands it is executing.
8390 @node Compiling with gcc,Compiler Switches,Building with gnatmake,Building Executable Programs with GNAT
8391 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-with-gcc}@anchor{1c}@anchor{gnat_ugn/building_executable_programs_with_gnat id8}@anchor{e7}
8392 @section Compiling with @code{gcc}
8395 This section discusses how to compile Ada programs using the @code{gcc}
8396 command. It also describes the set of switches
8397 that can be used to control the behavior of the compiler.
8400 * Compiling Programs::
8401 * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
8402 * Order of Compilation Issues::
8407 @node Compiling Programs,Search Paths and the Run-Time Library RTL,,Compiling with gcc
8408 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-programs}@anchor{e8}@anchor{gnat_ugn/building_executable_programs_with_gnat id9}@anchor{e9}
8409 @subsection Compiling Programs
8412 The first step in creating an executable program is to compile the units
8413 of the program using the @code{gcc} command. You must compile the
8420 the body file (@code{.adb}) for a library level subprogram or generic
8424 the spec file (@code{.ads}) for a library level package or generic
8425 package that has no body
8428 the body file (@code{.adb}) for a library level package
8429 or generic package that has a body
8432 You need @emph{not} compile the following files
8438 the spec of a library unit which has a body
8444 because they are compiled as part of compiling related units. GNAT
8446 when the corresponding body is compiled, and subunits when the parent is
8449 @geindex cannot generate code
8451 If you attempt to compile any of these files, you will get one of the
8452 following error messages (where @code{fff} is the name of the file you
8458 cannot generate code for file `@w{`}fff`@w{`} (package spec)
8459 to check package spec, use -gnatc
8461 cannot generate code for file `@w{`}fff`@w{`} (missing subunits)
8462 to check parent unit, use -gnatc
8464 cannot generate code for file `@w{`}fff`@w{`} (subprogram spec)
8465 to check subprogram spec, use -gnatc
8467 cannot generate code for file `@w{`}fff`@w{`} (subunit)
8468 to check subunit, use -gnatc
8472 As indicated by the above error messages, if you want to submit
8473 one of these files to the compiler to check for correct semantics
8474 without generating code, then use the @code{-gnatc} switch.
8476 The basic command for compiling a file containing an Ada unit is:
8479 $ gcc -c [switches] <file name>
8482 where @code{file name} is the name of the Ada file (usually
8483 having an extension @code{.ads} for a spec or @code{.adb} for a body).
8485 @code{-c} switch to tell @code{gcc} to compile, but not link, the file.
8486 The result of a successful compilation is an object file, which has the
8487 same name as the source file but an extension of @code{.o} and an Ada
8488 Library Information (ALI) file, which also has the same name as the
8489 source file, but with @code{.ali} as the extension. GNAT creates these
8490 two output files in the current directory, but you may specify a source
8491 file in any directory using an absolute or relative path specification
8492 containing the directory information.
8494 TESTING: the @code{--foobar@emph{NN}} switch
8498 @code{gcc} is actually a driver program that looks at the extensions of
8499 the file arguments and loads the appropriate compiler. For example, the
8500 GNU C compiler is @code{cc1}, and the Ada compiler is @code{gnat1}.
8501 These programs are in directories known to the driver program (in some
8502 configurations via environment variables you set), but need not be in
8503 your path. The @code{gcc} driver also calls the assembler and any other
8504 utilities needed to complete the generation of the required object
8507 It is possible to supply several file names on the same @code{gcc}
8508 command. This causes @code{gcc} to call the appropriate compiler for
8509 each file. For example, the following command lists two separate
8510 files to be compiled:
8513 $ gcc -c x.adb y.adb
8516 calls @code{gnat1} (the Ada compiler) twice to compile @code{x.adb} and
8518 The compiler generates two object files @code{x.o} and @code{y.o}
8519 and the two ALI files @code{x.ali} and @code{y.ali}.
8521 Any switches apply to all the files listed, see @ref{ea,,Compiler Switches} for a
8522 list of available @code{gcc} switches.
8524 @node Search Paths and the Run-Time Library RTL,Order of Compilation Issues,Compiling Programs,Compiling with gcc
8525 @anchor{gnat_ugn/building_executable_programs_with_gnat id10}@anchor{eb}@anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-and-the-run-time-library-rtl}@anchor{89}
8526 @subsection Search Paths and the Run-Time Library (RTL)
8529 With the GNAT source-based library system, the compiler must be able to
8530 find source files for units that are needed by the unit being compiled.
8531 Search paths are used to guide this process.
8533 The compiler compiles one source file whose name must be given
8534 explicitly on the command line. In other words, no searching is done
8535 for this file. To find all other source files that are needed (the most
8536 common being the specs of units), the compiler examines the following
8537 directories, in the following order:
8543 The directory containing the source file of the main unit being compiled
8544 (the file name on the command line).
8547 Each directory named by an @code{-I} switch given on the @code{gcc}
8548 command line, in the order given.
8550 @geindex ADA_PRJ_INCLUDE_FILE
8553 Each of the directories listed in the text file whose name is given
8555 @geindex ADA_PRJ_INCLUDE_FILE
8556 @geindex environment variable; ADA_PRJ_INCLUDE_FILE
8557 @code{ADA_PRJ_INCLUDE_FILE} environment variable.
8558 @geindex ADA_PRJ_INCLUDE_FILE
8559 @geindex environment variable; ADA_PRJ_INCLUDE_FILE
8560 @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the gnat
8561 driver when project files are used. It should not normally be set
8564 @geindex ADA_INCLUDE_PATH
8567 Each of the directories listed in the value of the
8568 @geindex ADA_INCLUDE_PATH
8569 @geindex environment variable; ADA_INCLUDE_PATH
8570 @code{ADA_INCLUDE_PATH} environment variable.
8571 Construct this value
8574 @geindex environment variable; PATH
8575 @code{PATH} environment variable: a list of directory
8576 names separated by colons (semicolons when working with the NT version).
8579 The content of the @code{ada_source_path} file which is part of the GNAT
8580 installation tree and is used to store standard libraries such as the
8581 GNAT Run Time Library (RTL) source files.
8582 @ref{87,,Installing a library}
8585 Specifying the switch @code{-I-}
8586 inhibits the use of the directory
8587 containing the source file named in the command line. You can still
8588 have this directory on your search path, but in this case it must be
8589 explicitly requested with a @code{-I} switch.
8591 Specifying the switch @code{-nostdinc}
8592 inhibits the search of the default location for the GNAT Run Time
8593 Library (RTL) source files.
8595 The compiler outputs its object files and ALI files in the current
8597 Caution: The object file can be redirected with the @code{-o} switch;
8598 however, @code{gcc} and @code{gnat1} have not been coordinated on this
8599 so the @code{ALI} file will not go to the right place. Therefore, you should
8600 avoid using the @code{-o} switch.
8604 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8605 children make up the GNAT RTL, together with the simple @code{System.IO}
8606 package used in the @code{"Hello World"} example. The sources for these units
8607 are needed by the compiler and are kept together in one directory. Not
8608 all of the bodies are needed, but all of the sources are kept together
8609 anyway. In a normal installation, you need not specify these directory
8610 names when compiling or binding. Either the environment variables or
8611 the built-in defaults cause these files to be found.
8613 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
8614 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
8615 consisting of child units of @code{GNAT}. This is a collection of generally
8616 useful types, subprograms, etc. See the @cite{GNAT_Reference_Manual}
8617 for further details.
8619 Besides simplifying access to the RTL, a major use of search paths is
8620 in compiling sources from multiple directories. This can make
8621 development environments much more flexible.
8623 @node Order of Compilation Issues,Examples,Search Paths and the Run-Time Library RTL,Compiling with gcc
8624 @anchor{gnat_ugn/building_executable_programs_with_gnat id11}@anchor{ec}@anchor{gnat_ugn/building_executable_programs_with_gnat order-of-compilation-issues}@anchor{ed}
8625 @subsection Order of Compilation Issues
8628 If, in our earlier example, there was a spec for the @code{hello}
8629 procedure, it would be contained in the file @code{hello.ads}; yet this
8630 file would not have to be explicitly compiled. This is the result of the
8631 model we chose to implement library management. Some of the consequences
8632 of this model are as follows:
8638 There is no point in compiling specs (except for package
8639 specs with no bodies) because these are compiled as needed by clients. If
8640 you attempt a useless compilation, you will receive an error message.
8641 It is also useless to compile subunits because they are compiled as needed
8645 There are no order of compilation requirements: performing a
8646 compilation never obsoletes anything. The only way you can obsolete
8647 something and require recompilations is to modify one of the
8648 source files on which it depends.
8651 There is no library as such, apart from the ALI files
8652 (@ref{42,,The Ada Library Information Files}, for information on the format
8653 of these files). For now we find it convenient to create separate ALI files,
8654 but eventually the information therein may be incorporated into the object
8658 When you compile a unit, the source files for the specs of all units
8659 that it @emph{with}s, all its subunits, and the bodies of any generics it
8660 instantiates must be available (reachable by the search-paths mechanism
8661 described above), or you will receive a fatal error message.
8664 @node Examples,,Order of Compilation Issues,Compiling with gcc
8665 @anchor{gnat_ugn/building_executable_programs_with_gnat id12}@anchor{ee}@anchor{gnat_ugn/building_executable_programs_with_gnat examples}@anchor{ef}
8666 @subsection Examples
8669 The following are some typical Ada compilation command line examples:
8675 Compile body in file @code{xyz.adb} with all default options.
8678 $ gcc -c -O2 -gnata xyz-def.adb
8681 Compile the child unit package in file @code{xyz-def.adb} with extensive
8682 optimizations, and pragma @code{Assert}/@cite{Debug} statements
8686 $ gcc -c -gnatc abc-def.adb
8689 Compile the subunit in file @code{abc-def.adb} in semantic-checking-only
8692 @node Compiler Switches,Linker Switches,Compiling with gcc,Building Executable Programs with GNAT
8693 @anchor{gnat_ugn/building_executable_programs_with_gnat compiler-switches}@anchor{f0}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gcc}@anchor{ea}
8694 @section Compiler Switches
8697 The @code{gcc} command accepts switches that control the
8698 compilation process. These switches are fully described in this section:
8699 first an alphabetical listing of all switches with a brief description,
8700 and then functionally grouped sets of switches with more detailed
8703 More switches exist for GCC than those documented here, especially
8704 for specific targets. However, their use is not recommended as
8705 they may change code generation in ways that are incompatible with
8706 the Ada run-time library, or can cause inconsistencies between
8710 * Alphabetical List of All Switches::
8711 * Output and Error Message Control::
8712 * Warning Message Control::
8713 * Debugging and Assertion Control::
8714 * Validity Checking::
8717 * Using gcc for Syntax Checking::
8718 * Using gcc for Semantic Checking::
8719 * Compiling Different Versions of Ada::
8720 * Character Set Control::
8721 * File Naming Control::
8722 * Subprogram Inlining Control::
8723 * Auxiliary Output Control::
8724 * Debugging Control::
8725 * Exception Handling Control::
8726 * Units to Sources Mapping Files::
8727 * Code Generation Control::
8731 @node Alphabetical List of All Switches,Output and Error Message Control,,Compiler Switches
8732 @anchor{gnat_ugn/building_executable_programs_with_gnat id13}@anchor{f1}@anchor{gnat_ugn/building_executable_programs_with_gnat alphabetical-list-of-all-switches}@anchor{f2}
8733 @subsection Alphabetical List of All Switches
8741 @item @code{-b @emph{target}}
8743 Compile your program to run on @code{target}, which is the name of a
8744 system configuration. You must have a GNAT cross-compiler built if
8745 @code{target} is not the same as your host system.
8753 @item @code{-B@emph{dir}}
8755 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8756 from @code{dir} instead of the default location. Only use this switch
8757 when multiple versions of the GNAT compiler are available.
8758 See the "Options for Directory Search" section in the
8759 @cite{Using the GNU Compiler Collection (GCC)} manual for further details.
8760 You would normally use the @code{-b} or @code{-V} switch instead.
8770 Compile. Always use this switch when compiling Ada programs.
8772 Note: for some other languages when using @code{gcc}, notably in
8773 the case of C and C++, it is possible to use
8774 use @code{gcc} without a @code{-c} switch to
8775 compile and link in one step. In the case of GNAT, you
8776 cannot use this approach, because the binder must be run
8777 and @code{gcc} cannot be used to run the GNAT binder.
8780 @geindex -fcallgraph-info (gcc)
8785 @item @code{-fcallgraph-info[=su,da]}
8787 Makes the compiler output callgraph information for the program, on a
8788 per-file basis. The information is generated in the VCG format. It can
8789 be decorated with additional, per-node and/or per-edge information, if a
8790 list of comma-separated markers is additionally specified. When the
8791 @code{su} marker is specified, the callgraph is decorated with stack usage
8792 information; it is equivalent to @code{-fstack-usage}. When the @code{da}
8793 marker is specified, the callgraph is decorated with information about
8794 dynamically allocated objects.
8797 @geindex -fdump-scos (gcc)
8802 @item @code{-fdump-scos}
8804 Generates SCO (Source Coverage Obligation) information in the ALI file.
8805 This information is used by advanced coverage tools. See unit @code{SCOs}
8806 in the compiler sources for details in files @code{scos.ads} and
8810 @geindex -fgnat-encodings (gcc)
8815 @item @code{-fgnat-encodings=[all|gdb|minimal]}
8817 This switch controls the balance between GNAT encodings and standard DWARF
8818 emitted in the debug information.
8821 @geindex -flto (gcc)
8826 @item @code{-flto[=@emph{n}]}
8828 Enables Link Time Optimization. This switch must be used in conjunction
8829 with the @code{-Ox} switches (but not with the @code{-gnatn} switch
8830 since it is a full replacement for the latter) and instructs the compiler
8831 to defer most optimizations until the link stage. The advantage of this
8832 approach is that the compiler can do a whole-program analysis and choose
8833 the best interprocedural optimization strategy based on a complete view
8834 of the program, instead of a fragmentary view with the usual approach.
8835 This can also speed up the compilation of big programs and reduce the
8836 size of the executable, compared with a traditional per-unit compilation
8837 with inlining across units enabled by the @code{-gnatn} switch.
8838 The drawback of this approach is that it may require more memory and that
8839 the debugging information generated by -g with it might be hardly usable.
8840 The switch, as well as the accompanying @code{-Ox} switches, must be
8841 specified both for the compilation and the link phases.
8842 If the @code{n} parameter is specified, the optimization and final code
8843 generation at link time are executed using @code{n} parallel jobs by
8844 means of an installed @code{make} program.
8847 @geindex -fno-inline (gcc)
8852 @item @code{-fno-inline}
8854 Suppresses all inlining, unless requested with pragma @code{Inline_Always}. The
8855 effect is enforced regardless of other optimization or inlining switches.
8856 Note that inlining can also be suppressed on a finer-grained basis with
8857 pragma @code{No_Inline}.
8860 @geindex -fno-inline-functions (gcc)
8865 @item @code{-fno-inline-functions}
8867 Suppresses automatic inlining of subprograms, which is enabled
8868 if @code{-O3} is used.
8871 @geindex -fno-inline-small-functions (gcc)
8876 @item @code{-fno-inline-small-functions}
8878 Suppresses automatic inlining of small subprograms, which is enabled
8879 if @code{-O2} is used.
8882 @geindex -fno-inline-functions-called-once (gcc)
8887 @item @code{-fno-inline-functions-called-once}
8889 Suppresses inlining of subprograms local to the unit and called once
8890 from within it, which is enabled if @code{-O1} is used.
8893 @geindex -fno-ivopts (gcc)
8898 @item @code{-fno-ivopts}
8900 Suppresses high-level loop induction variable optimizations, which are
8901 enabled if @code{-O1} is used. These optimizations are generally
8902 profitable but, for some specific cases of loops with numerous uses
8903 of the iteration variable that follow a common pattern, they may end
8904 up destroying the regularity that could be exploited at a lower level
8905 and thus producing inferior code.
8908 @geindex -fno-strict-aliasing (gcc)
8913 @item @code{-fno-strict-aliasing}
8915 Causes the compiler to avoid assumptions regarding non-aliasing
8916 of objects of different types. See
8917 @ref{f3,,Optimization and Strict Aliasing} for details.
8920 @geindex -fno-strict-overflow (gcc)
8925 @item @code{-fno-strict-overflow}
8927 Causes the compiler to avoid assumptions regarding the rules of signed
8928 integer overflow. These rules specify that signed integer overflow will
8929 result in a Constraint_Error exception at run time and are enforced in
8930 default mode by the compiler, so this switch should not be necessary in
8931 normal operating mode. It might be useful in conjunction with @code{-gnato0}
8932 for very peculiar cases of low-level programming.
8935 @geindex -fstack-check (gcc)
8940 @item @code{-fstack-check}
8942 Activates stack checking.
8943 See @ref{f4,,Stack Overflow Checking} for details.
8946 @geindex -fstack-usage (gcc)
8951 @item @code{-fstack-usage}
8953 Makes the compiler output stack usage information for the program, on a
8954 per-subprogram basis. See @ref{f5,,Static Stack Usage Analysis} for details.
8964 Generate debugging information. This information is stored in the object
8965 file and copied from there to the final executable file by the linker,
8966 where it can be read by the debugger. You must use the
8967 @code{-g} switch if you plan on using the debugger.
8970 @geindex -gnat05 (gcc)
8975 @item @code{-gnat05}
8977 Allow full Ada 2005 features.
8980 @geindex -gnat12 (gcc)
8985 @item @code{-gnat12}
8987 Allow full Ada 2012 features.
8990 @geindex -gnat83 (gcc)
8992 @geindex -gnat2005 (gcc)
8997 @item @code{-gnat2005}
8999 Allow full Ada 2005 features (same as @code{-gnat05})
9002 @geindex -gnat2012 (gcc)
9007 @item @code{-gnat2012}
9009 Allow full Ada 2012 features (same as @code{-gnat12})
9011 @item @code{-gnat83}
9013 Enforce Ada 83 restrictions.
9016 @geindex -gnat95 (gcc)
9021 @item @code{-gnat95}
9023 Enforce Ada 95 restrictions.
9025 Note: for compatibility with some Ada 95 compilers which support only
9026 the @code{overriding} keyword of Ada 2005, the @code{-gnatd.D} switch can
9027 be used along with @code{-gnat95} to achieve a similar effect with GNAT.
9029 @code{-gnatd.D} instructs GNAT to consider @code{overriding} as a keyword
9030 and handle its associated semantic checks, even in Ada 95 mode.
9033 @geindex -gnata (gcc)
9040 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
9041 activated. Note that these pragmas can also be controlled using the
9042 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
9043 It also activates pragmas @code{Check}, @code{Precondition}, and
9044 @code{Postcondition}. Note that these pragmas can also be controlled
9045 using the configuration pragma @code{Check_Policy}. In Ada 2012, it
9046 also activates all assertions defined in the RM as aspects: preconditions,
9047 postconditions, type invariants and (sub)type predicates. In all Ada modes,
9048 corresponding pragmas for type invariants and (sub)type predicates are
9049 also activated. The default is that all these assertions are disabled,
9050 and have no effect, other than being checked for syntactic validity, and
9051 in the case of subtype predicates, constructions such as membership tests
9052 still test predicates even if assertions are turned off.
9055 @geindex -gnatA (gcc)
9062 Avoid processing @code{gnat.adc}. If a @code{gnat.adc} file is present,
9066 @geindex -gnatb (gcc)
9073 Generate brief messages to @code{stderr} even if verbose mode set.
9076 @geindex -gnatB (gcc)
9083 Assume no invalid (bad) values except for 'Valid attribute use
9084 (@ref{f6,,Validity Checking}).
9087 @geindex -gnatc (gcc)
9094 Check syntax and semantics only (no code generation attempted). When the
9095 compiler is invoked by @code{gnatmake}, if the switch @code{-gnatc} is
9096 only given to the compiler (after @code{-cargs} or in package Compiler of
9097 the project file, @code{gnatmake} will fail because it will not find the
9098 object file after compilation. If @code{gnatmake} is called with
9099 @code{-gnatc} as a builder switch (before @code{-cargs} or in package
9100 Builder of the project file) then @code{gnatmake} will not fail because
9101 it will not look for the object files after compilation, and it will not try
9105 @geindex -gnatC (gcc)
9112 Generate CodePeer intermediate format (no code generation attempted).
9113 This switch will generate an intermediate representation suitable for
9114 use by CodePeer (@code{.scil} files). This switch is not compatible with
9115 code generation (it will, among other things, disable some switches such
9116 as -gnatn, and enable others such as -gnata).
9119 @geindex -gnatd (gcc)
9126 Specify debug options for the compiler. The string of characters after
9127 the @code{-gnatd} specify the specific debug options. The possible
9128 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
9129 compiler source file @code{debug.adb} for details of the implemented
9130 debug options. Certain debug options are relevant to applications
9131 programmers, and these are documented at appropriate points in this
9135 @geindex -gnatD[nn] (gcc)
9142 Create expanded source files for source level debugging. This switch
9143 also suppresses generation of cross-reference information
9144 (see @code{-gnatx}). Note that this switch is not allowed if a previous
9145 -gnatR switch has been given, since these two switches are not compatible.
9148 @geindex -gnateA (gcc)
9153 @item @code{-gnateA}
9155 Check that the actual parameters of a subprogram call are not aliases of one
9156 another. To qualify as aliasing, the actuals must denote objects of a composite
9157 type, their memory locations must be identical or overlapping, and at least one
9158 of the corresponding formal parameters must be of mode OUT or IN OUT.
9161 type Rec_Typ is record
9162 Data : Integer := 0;
9165 function Self (Val : Rec_Typ) return Rec_Typ is
9170 procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is
9173 end Detect_Aliasing;
9177 Detect_Aliasing (Obj, Obj);
9178 Detect_Aliasing (Obj, Self (Obj));
9181 In the example above, the first call to @code{Detect_Aliasing} fails with a
9182 @code{Program_Error} at run time because the actuals for @code{Val_1} and
9183 @code{Val_2} denote the same object. The second call executes without raising
9184 an exception because @code{Self(Obj)} produces an anonymous object which does
9185 not share the memory location of @code{Obj}.
9188 @geindex -gnatec (gcc)
9193 @item @code{-gnatec=@emph{path}}
9195 Specify a configuration pragma file
9196 (the equal sign is optional)
9197 (@ref{79,,The Configuration Pragmas Files}).
9200 @geindex -gnateC (gcc)
9205 @item @code{-gnateC}
9207 Generate CodePeer messages in a compiler-like format. This switch is only
9208 effective if @code{-gnatcC} is also specified and requires an installation
9212 @geindex -gnated (gcc)
9217 @item @code{-gnated}
9219 Disable atomic synchronization
9222 @geindex -gnateD (gcc)
9227 @item @code{-gnateDsymbol[=@emph{value}]}
9229 Defines a symbol, associated with @code{value}, for preprocessing.
9230 (@ref{18,,Integrated Preprocessing}).
9233 @geindex -gnateE (gcc)
9238 @item @code{-gnateE}
9240 Generate extra information in exception messages. In particular, display
9241 extra column information and the value and range associated with index and
9242 range check failures, and extra column information for access checks.
9243 In cases where the compiler is able to determine at compile time that
9244 a check will fail, it gives a warning, and the extra information is not
9245 produced at run time.
9248 @geindex -gnatef (gcc)
9253 @item @code{-gnatef}
9255 Display full source path name in brief error messages.
9258 @geindex -gnateF (gcc)
9263 @item @code{-gnateF}
9265 Check for overflow on all floating-point operations, including those
9266 for unconstrained predefined types. See description of pragma
9267 @code{Check_Float_Overflow} in GNAT RM.
9270 @geindex -gnateg (gcc)
9277 The @code{-gnatc} switch must always be specified before this switch, e.g.
9278 @code{-gnatceg}. Generate a C header from the Ada input file. See
9279 @ref{ca,,Generating C Headers for Ada Specifications} for more
9283 @geindex -gnateG (gcc)
9288 @item @code{-gnateG}
9290 Save result of preprocessing in a text file.
9293 @geindex -gnatei (gcc)
9298 @item @code{-gnatei@emph{nnn}}
9300 Set maximum number of instantiations during compilation of a single unit to
9301 @code{nnn}. This may be useful in increasing the default maximum of 8000 for
9302 the rare case when a single unit legitimately exceeds this limit.
9305 @geindex -gnateI (gcc)
9310 @item @code{-gnateI@emph{nnn}}
9312 Indicates that the source is a multi-unit source and that the index of the
9313 unit to compile is @code{nnn}. @code{nnn} needs to be a positive number and need
9314 to be a valid index in the multi-unit source.
9317 @geindex -gnatel (gcc)
9322 @item @code{-gnatel}
9324 This switch can be used with the static elaboration model to issue info
9326 where implicit @code{pragma Elaborate} and @code{pragma Elaborate_All}
9327 are generated. This is useful in diagnosing elaboration circularities
9328 caused by these implicit pragmas when using the static elaboration
9329 model. See See the section in this guide on elaboration checking for
9330 further details. These messages are not generated by default, and are
9331 intended only for temporary use when debugging circularity problems.
9334 @geindex -gnatel (gcc)
9339 @item @code{-gnateL}
9341 This switch turns off the info messages about implicit elaboration pragmas.
9344 @geindex -gnatem (gcc)
9349 @item @code{-gnatem=@emph{path}}
9351 Specify a mapping file
9352 (the equal sign is optional)
9353 (@ref{f7,,Units to Sources Mapping Files}).
9356 @geindex -gnatep (gcc)
9361 @item @code{-gnatep=@emph{file}}
9363 Specify a preprocessing data file
9364 (the equal sign is optional)
9365 (@ref{18,,Integrated Preprocessing}).
9368 @geindex -gnateP (gcc)
9373 @item @code{-gnateP}
9375 Turn categorization dependency errors into warnings.
9376 Ada requires that units that WITH one another have compatible categories, for
9377 example a Pure unit cannot WITH a Preelaborate unit. If this switch is used,
9378 these errors become warnings (which can be ignored, or suppressed in the usual
9379 manner). This can be useful in some specialized circumstances such as the
9380 temporary use of special test software.
9383 @geindex -gnateS (gcc)
9388 @item @code{-gnateS}
9390 Synonym of @code{-fdump-scos}, kept for backwards compatibility.
9393 @geindex -gnatet=file (gcc)
9398 @item @code{-gnatet=@emph{path}}
9400 Generate target dependent information. The format of the output file is
9401 described in the section about switch @code{-gnateT}.
9404 @geindex -gnateT (gcc)
9409 @item @code{-gnateT=@emph{path}}
9411 Read target dependent information, such as endianness or sizes and alignments
9412 of base type. If this switch is passed, the default target dependent
9413 information of the compiler is replaced by the one read from the input file.
9414 This is used by tools other than the compiler, e.g. to do
9415 semantic analysis of programs that will run on some other target than
9416 the machine on which the tool is run.
9418 The following target dependent values should be defined,
9419 where @code{Nat} denotes a natural integer value, @code{Pos} denotes a
9420 positive integer value, and fields marked with a question mark are
9421 boolean fields, where a value of 0 is False, and a value of 1 is True:
9424 Bits_BE : Nat; -- Bits stored big-endian?
9425 Bits_Per_Unit : Pos; -- Bits in a storage unit
9426 Bits_Per_Word : Pos; -- Bits in a word
9427 Bytes_BE : Nat; -- Bytes stored big-endian?
9428 Char_Size : Pos; -- Standard.Character'Size
9429 Double_Float_Alignment : Nat; -- Alignment of double float
9430 Double_Scalar_Alignment : Nat; -- Alignment of double length scalar
9431 Double_Size : Pos; -- Standard.Long_Float'Size
9432 Float_Size : Pos; -- Standard.Float'Size
9433 Float_Words_BE : Nat; -- Float words stored big-endian?
9434 Int_Size : Pos; -- Standard.Integer'Size
9435 Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size
9436 Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size
9437 Long_Size : Pos; -- Standard.Long_Integer'Size
9438 Maximum_Alignment : Pos; -- Maximum permitted alignment
9439 Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field
9440 Pointer_Size : Pos; -- System.Address'Size
9441 Short_Enums : Nat; -- Foreign enums use short size?
9442 Short_Size : Pos; -- Standard.Short_Integer'Size
9443 Strict_Alignment : Nat; -- Strict alignment?
9444 System_Allocator_Alignment : Nat; -- Alignment for malloc calls
9445 Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size
9446 Words_BE : Nat; -- Words stored big-endian?
9449 @code{Bits_Per_Unit} is the number of bits in a storage unit, the equivalent of
9450 GCC macro @code{BITS_PER_UNIT} documented as follows: @cite{Define this macro to be the number of bits in an addressable storage unit (byte); normally 8.}
9452 @code{Bits_Per_Word} is the number of bits in a machine word, the equivalent of
9453 GCC macro @code{BITS_PER_WORD} documented as follows: @cite{Number of bits in a word; normally 32.}
9455 @code{Double_Float_Alignment}, if not zero, is the maximum alignment that the
9456 compiler can choose by default for a 64-bit floating-point type or object.
9458 @code{Double_Scalar_Alignment}, if not zero, is the maximum alignment that the
9459 compiler can choose by default for a 64-bit or larger scalar type or object.
9461 @code{Maximum_Alignment} is the maximum alignment that the compiler can choose
9462 by default for a type or object, which is also the maximum alignment that can
9463 be specified in GNAT. It is computed for GCC backends as @code{BIGGEST_ALIGNMENT
9464 / BITS_PER_UNIT} where GCC macro @code{BIGGEST_ALIGNMENT} is documented as
9465 follows: @cite{Biggest alignment that any data type can require on this machine@comma{} in bits.}
9467 @code{Max_Unaligned_Field} is the maximum size for unaligned bit field, which is
9468 64 for the majority of GCC targets (but can be different on some targets like
9471 @code{Strict_Alignment} is the equivalent of GCC macro @code{STRICT_ALIGNMENT}
9472 documented as follows: @cite{Define this macro to be the value 1 if instructions will fail to work if given data not on the nominal alignment. If instructions will merely go slower in that case@comma{} define this macro as 0.}
9474 @code{System_Allocator_Alignment} is the guaranteed alignment of data returned
9475 by calls to @code{malloc}.
9477 The format of the input file is as follows. First come the values of
9478 the variables defined above, with one line per value:
9484 where @code{name} is the name of the parameter, spelled out in full,
9485 and cased as in the above list, and @code{value} is an unsigned decimal
9486 integer. Two or more blanks separates the name from the value.
9488 All the variables must be present, in alphabetical order (i.e. the
9489 same order as the list above).
9491 Then there is a blank line to separate the two parts of the file. Then
9492 come the lines showing the floating-point types to be registered, with
9493 one line per registered mode:
9496 name digs float_rep size alignment
9499 where @code{name} is the string name of the type (which can have
9500 single spaces embedded in the name (e.g. long double), @code{digs} is
9501 the number of digits for the floating-point type, @code{float_rep} is
9502 the float representation (I/V/A for IEEE-754-Binary, Vax_Native,
9503 AAMP), @code{size} is the size in bits, @code{alignment} is the
9504 alignment in bits. The name is followed by at least two blanks, fields
9505 are separated by at least one blank, and a LF character immediately
9506 follows the alignment field.
9508 Here is an example of a target parameterization file:
9516 Double_Float_Alignment 0
9517 Double_Scalar_Alignment 0
9522 Long_Double_Size 128
9525 Maximum_Alignment 16
9526 Max_Unaligned_Field 64
9530 System_Allocator_Alignment 16
9536 long double 18 I 80 128
9541 @geindex -gnateu (gcc)
9546 @item @code{-gnateu}
9548 Ignore unrecognized validity, warning, and style switches that
9549 appear after this switch is given. This may be useful when
9550 compiling sources developed on a later version of the compiler
9551 with an earlier version. Of course the earlier version must
9552 support this switch.
9555 @geindex -gnateV (gcc)
9560 @item @code{-gnateV}
9562 Check that all actual parameters of a subprogram call are valid according to
9563 the rules of validity checking (@ref{f6,,Validity Checking}).
9566 @geindex -gnateY (gcc)
9571 @item @code{-gnateY}
9573 Ignore all STYLE_CHECKS pragmas. Full legality checks
9574 are still carried out, but the pragmas have no effect
9575 on what style checks are active. This allows all style
9576 checking options to be controlled from the command line.
9579 @geindex -gnatE (gcc)
9586 Dynamic elaboration checking mode enabled. For further details see
9587 @ref{f,,Elaboration Order Handling in GNAT}.
9590 @geindex -gnatf (gcc)
9597 Full errors. Multiple errors per line, all undefined references, do not
9598 attempt to suppress cascaded errors.
9601 @geindex -gnatF (gcc)
9608 Externals names are folded to all uppercase.
9611 @geindex -gnatg (gcc)
9618 Internal GNAT implementation mode. This should not be used for applications
9619 programs, it is intended only for use by the compiler and its run-time
9620 library. For documentation, see the GNAT sources. Note that @code{-gnatg}
9621 implies @code{-gnatw.ge} and @code{-gnatyg} so that all standard
9622 warnings and all standard style options are turned on. All warnings and style
9623 messages are treated as errors.
9626 @geindex -gnatG[nn] (gcc)
9631 @item @code{-gnatG=nn}
9633 List generated expanded code in source form.
9636 @geindex -gnath (gcc)
9643 Output usage information. The output is written to @code{stdout}.
9646 @geindex -gnatH (gcc)
9653 Legacy elaboration-checking mode enabled. When this switch is in effect,
9654 the pre-18.x access-before-elaboration model becomes the de facto model.
9655 For further details see @ref{f,,Elaboration Order Handling in GNAT}.
9658 @geindex -gnati (gcc)
9663 @item @code{-gnati@emph{c}}
9665 Identifier character set (@code{c} = 1/2/3/4/8/9/p/f/n/w).
9666 For details of the possible selections for @code{c},
9667 see @ref{48,,Character Set Control}.
9670 @geindex -gnatI (gcc)
9677 Ignore representation clauses. When this switch is used,
9678 representation clauses are treated as comments. This is useful
9679 when initially porting code where you want to ignore rep clause
9680 problems, and also for compiling foreign code (particularly
9681 for use with ASIS). The representation clauses that are ignored
9682 are: enumeration_representation_clause, record_representation_clause,
9683 and attribute_definition_clause for the following attributes:
9684 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
9685 Object_Size, Scalar_Storage_Order, Size, Small, Stream_Size,
9686 and Value_Size. Pragma Default_Scalar_Storage_Order is also ignored.
9687 Note that this option should be used only for compiling -- the
9688 code is likely to malfunction at run time.
9690 Note that when @code{-gnatct} is used to generate trees for input
9691 into ASIS tools, these representation clauses are removed
9692 from the tree and ignored. This means that the tool will not see them.
9695 @geindex -gnatjnn (gcc)
9700 @item @code{-gnatj@emph{nn}}
9702 Reformat error messages to fit on @code{nn} character lines
9705 @geindex -gnatJ (gcc)
9712 Permissive elaboration-checking mode enabled. When this switch is in effect,
9713 the post-18.x access-before-elaboration model ignores potential issues with:
9722 Activations of tasks defined in instances
9728 Calls from within an instance to its enclosing context
9731 Calls through generic formal parameters
9734 Calls to subprograms defined in instances
9740 Indirect calls using 'Access
9749 Synchronous task suspension
9752 and does not emit compile-time diagnostics or run-time checks. For further
9753 details see @ref{f,,Elaboration Order Handling in GNAT}.
9756 @geindex -gnatk (gcc)
9761 @item @code{-gnatk=@emph{n}}
9763 Limit file names to @code{n} (1-999) characters (@code{k} = krunch).
9766 @geindex -gnatl (gcc)
9773 Output full source listing with embedded error messages.
9776 @geindex -gnatL (gcc)
9783 Used in conjunction with -gnatG or -gnatD to intersperse original
9784 source lines (as comment lines with line numbers) in the expanded
9788 @geindex -gnatm (gcc)
9793 @item @code{-gnatm=@emph{n}}
9795 Limit number of detected error or warning messages to @code{n}
9796 where @code{n} is in the range 1..999999. The default setting if
9797 no switch is given is 9999. If the number of warnings reaches this
9798 limit, then a message is output and further warnings are suppressed,
9799 but the compilation is continued. If the number of error messages
9800 reaches this limit, then a message is output and the compilation
9801 is abandoned. The equal sign here is optional. A value of zero
9802 means that no limit applies.
9805 @geindex -gnatn (gcc)
9810 @item @code{-gnatn[12]}
9812 Activate inlining across units for subprograms for which pragma @code{Inline}
9813 is specified. This inlining is performed by the GCC back-end. An optional
9814 digit sets the inlining level: 1 for moderate inlining across units
9815 or 2 for full inlining across units. If no inlining level is specified,
9816 the compiler will pick it based on the optimization level.
9819 @geindex -gnatN (gcc)
9826 Activate front end inlining for subprograms for which
9827 pragma @code{Inline} is specified. This inlining is performed
9828 by the front end and will be visible in the
9829 @code{-gnatG} output.
9831 When using a gcc-based back end (in practice this means using any version
9832 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
9833 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
9834 Historically front end inlining was more extensive than the gcc back end
9835 inlining, but that is no longer the case.
9838 @geindex -gnato0 (gcc)
9843 @item @code{-gnato0}
9845 Suppresses overflow checking. This causes the behavior of the compiler to
9846 match the default for older versions where overflow checking was suppressed
9847 by default. This is equivalent to having
9848 @code{pragma Suppress (Overflow_Check)} in a configuration pragma file.
9851 @geindex -gnato?? (gcc)
9856 @item @code{-gnato??}
9858 Set default mode for handling generation of code to avoid intermediate
9859 arithmetic overflow. Here @code{??} is two digits, a
9860 single digit, or nothing. Each digit is one of the digits @code{1}
9864 @multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
9879 All intermediate overflows checked against base type (@code{STRICT})
9887 Minimize intermediate overflows (@code{MINIMIZED})
9895 Eliminate intermediate overflows (@code{ELIMINATED})
9900 If only one digit appears, then it applies to all
9901 cases; if two digits are given, then the first applies outside
9902 assertions, pre/postconditions, and type invariants, and the second
9903 applies within assertions, pre/postconditions, and type invariants.
9905 If no digits follow the @code{-gnato}, then it is equivalent to
9907 causing all intermediate overflows to be handled in strict
9910 This switch also causes arithmetic overflow checking to be performed
9911 (as though @code{pragma Unsuppress (Overflow_Check)} had been specified).
9913 The default if no option @code{-gnato} is given is that overflow handling
9914 is in @code{STRICT} mode (computations done using the base type), and that
9915 overflow checking is enabled.
9917 Note that division by zero is a separate check that is not
9918 controlled by this switch (divide-by-zero checking is on by default).
9920 See also @ref{f8,,Specifying the Desired Mode}.
9923 @geindex -gnatp (gcc)
9930 Suppress all checks. See @ref{f9,,Run-Time Checks} for details. This switch
9931 has no effect if cancelled by a subsequent @code{-gnat-p} switch.
9934 @geindex -gnat-p (gcc)
9939 @item @code{-gnat-p}
9941 Cancel effect of previous @code{-gnatp} switch.
9944 @geindex -gnatP (gcc)
9951 Enable polling. This is required on some systems (notably Windows NT) to
9952 obtain asynchronous abort and asynchronous transfer of control capability.
9953 See @code{Pragma_Polling} in the @cite{GNAT_Reference_Manual} for full
9957 @geindex -gnatq (gcc)
9964 Don't quit. Try semantics, even if parse errors.
9967 @geindex -gnatQ (gcc)
9974 Don't quit. Generate @code{ALI} and tree files even if illegalities.
9975 Note that code generation is still suppressed in the presence of any
9976 errors, so even with @code{-gnatQ} no object file is generated.
9979 @geindex -gnatr (gcc)
9986 Treat pragma Restrictions as Restriction_Warnings.
9989 @geindex -gnatR (gcc)
9994 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
9996 Output representation information for declared types, objects and
9997 subprograms. Note that this switch is not allowed if a previous
9998 @code{-gnatD} switch has been given, since these two switches
10002 @geindex -gnats (gcc)
10007 @item @code{-gnats}
10012 @geindex -gnatS (gcc)
10017 @item @code{-gnatS}
10019 Print package Standard.
10022 @geindex -gnatt (gcc)
10027 @item @code{-gnatt}
10029 Generate tree output file.
10032 @geindex -gnatT (gcc)
10037 @item @code{-gnatT@emph{nnn}}
10039 All compiler tables start at @code{nnn} times usual starting size.
10042 @geindex -gnatu (gcc)
10047 @item @code{-gnatu}
10049 List units for this compilation.
10052 @geindex -gnatU (gcc)
10057 @item @code{-gnatU}
10059 Tag all error messages with the unique string 'error:'
10062 @geindex -gnatv (gcc)
10067 @item @code{-gnatv}
10069 Verbose mode. Full error output with source lines to @code{stdout}.
10072 @geindex -gnatV (gcc)
10077 @item @code{-gnatV}
10079 Control level of validity checking (@ref{f6,,Validity Checking}).
10082 @geindex -gnatw (gcc)
10087 @item @code{-gnatw@emph{xxx}}
10090 @code{xxx} is a string of option letters that denotes
10091 the exact warnings that
10092 are enabled or disabled (@ref{fa,,Warning Message Control}).
10095 @geindex -gnatW (gcc)
10100 @item @code{-gnatW@emph{e}}
10102 Wide character encoding method
10103 (@code{e}=n/h/u/s/e/8).
10106 @geindex -gnatx (gcc)
10111 @item @code{-gnatx}
10113 Suppress generation of cross-reference information.
10116 @geindex -gnatX (gcc)
10121 @item @code{-gnatX}
10123 Enable GNAT implementation extensions and latest Ada version.
10126 @geindex -gnaty (gcc)
10131 @item @code{-gnaty}
10133 Enable built-in style checks (@ref{fb,,Style Checking}).
10136 @geindex -gnatz (gcc)
10141 @item @code{-gnatz@emph{m}}
10143 Distribution stub generation and compilation
10144 (@code{m}=r/c for receiver/caller stubs).
10152 @item @code{-I@emph{dir}}
10156 Direct GNAT to search the @code{dir} directory for source files needed by
10157 the current compilation
10158 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10170 Except for the source file named in the command line, do not look for source
10171 files in the directory containing the source file named in the command line
10172 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10180 @item @code{-o @emph{file}}
10182 This switch is used in @code{gcc} to redirect the generated object file
10183 and its associated ALI file. Beware of this switch with GNAT, because it may
10184 cause the object file and ALI file to have different names which in turn
10185 may confuse the binder and the linker.
10188 @geindex -nostdinc (gcc)
10193 @item @code{-nostdinc}
10195 Inhibit the search of the default location for the GNAT Run Time
10196 Library (RTL) source files.
10199 @geindex -nostdlib (gcc)
10204 @item @code{-nostdlib}
10206 Inhibit the search of the default location for the GNAT Run Time
10207 Library (RTL) ALI files.
10215 @item @code{-O[@emph{n}]}
10217 @code{n} controls the optimization level:
10220 @multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
10235 No optimization, the default setting if no @code{-O} appears
10243 Normal optimization, the default if you specify @code{-O} without an
10244 operand. A good compromise between code quality and compilation
10253 Extensive optimization, may improve execution time, possibly at
10254 the cost of substantially increased compilation time.
10262 Same as @code{-O2}, and also includes inline expansion for small
10263 subprograms in the same unit.
10271 Optimize space usage
10276 See also @ref{fc,,Optimization Levels}.
10279 @geindex -pass-exit-codes (gcc)
10284 @item @code{-pass-exit-codes}
10286 Catch exit codes from the compiler and use the most meaningful as
10290 @geindex --RTS (gcc)
10295 @item @code{--RTS=@emph{rts-path}}
10297 Specifies the default location of the run-time library. Same meaning as the
10298 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
10308 Used in place of @code{-c} to
10309 cause the assembler source file to be
10310 generated, using @code{.s} as the extension,
10311 instead of the object file.
10312 This may be useful if you need to examine the generated assembly code.
10315 @geindex -fverbose-asm (gcc)
10320 @item @code{-fverbose-asm}
10322 Used in conjunction with @code{-S}
10323 to cause the generated assembly code file to be annotated with variable
10324 names, making it significantly easier to follow.
10334 Show commands generated by the @code{gcc} driver. Normally used only for
10335 debugging purposes or if you need to be sure what version of the
10336 compiler you are executing.
10344 @item @code{-V @emph{ver}}
10346 Execute @code{ver} version of the compiler. This is the @code{gcc}
10347 version, not the GNAT version.
10357 Turn off warnings generated by the back end of the compiler. Use of
10358 this switch also causes the default for front end warnings to be set
10359 to suppress (as though @code{-gnatws} had appeared at the start of
10363 @geindex Combining GNAT switches
10365 You may combine a sequence of GNAT switches into a single switch. For
10366 example, the combined switch
10375 is equivalent to specifying the following sequence of switches:
10380 -gnato -gnatf -gnati3
10384 The following restrictions apply to the combination of switches
10391 The switch @code{-gnatc} if combined with other switches must come
10392 first in the string.
10395 The switch @code{-gnats} if combined with other switches must come
10396 first in the string.
10400 @code{-gnatzc} and @code{-gnatzr} may not be combined with any other
10401 switches, and only one of them may appear in the command line.
10404 The switch @code{-gnat-p} may not be combined with any other switch.
10407 Once a 'y' appears in the string (that is a use of the @code{-gnaty}
10408 switch), then all further characters in the switch are interpreted
10409 as style modifiers (see description of @code{-gnaty}).
10412 Once a 'd' appears in the string (that is a use of the @code{-gnatd}
10413 switch), then all further characters in the switch are interpreted
10414 as debug flags (see description of @code{-gnatd}).
10417 Once a 'w' appears in the string (that is a use of the @code{-gnatw}
10418 switch), then all further characters in the switch are interpreted
10419 as warning mode modifiers (see description of @code{-gnatw}).
10422 Once a 'V' appears in the string (that is a use of the @code{-gnatV}
10423 switch), then all further characters in the switch are interpreted
10424 as validity checking options (@ref{f6,,Validity Checking}).
10427 Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in
10428 a combined list of options.
10431 @node Output and Error Message Control,Warning Message Control,Alphabetical List of All Switches,Compiler Switches
10432 @anchor{gnat_ugn/building_executable_programs_with_gnat id14}@anchor{fd}@anchor{gnat_ugn/building_executable_programs_with_gnat output-and-error-message-control}@anchor{fe}
10433 @subsection Output and Error Message Control
10438 The standard default format for error messages is called 'brief format'.
10439 Brief format messages are written to @code{stderr} (the standard error
10440 file) and have the following form:
10443 e.adb:3:04: Incorrect spelling of keyword "function"
10444 e.adb:4:20: ";" should be "is"
10447 The first integer after the file name is the line number in the file,
10448 and the second integer is the column number within the line.
10449 @code{GPS} can parse the error messages
10450 and point to the referenced character.
10451 The following switches provide control over the error message
10454 @geindex -gnatv (gcc)
10459 @item @code{-gnatv}
10461 The @code{v} stands for verbose.
10462 The effect of this setting is to write long-format error
10463 messages to @code{stdout} (the standard output file.
10464 The same program compiled with the
10465 @code{-gnatv} switch would generate:
10468 3. funcion X (Q : Integer)
10470 >>> Incorrect spelling of keyword "function"
10473 >>> ";" should be "is"
10476 The vertical bar indicates the location of the error, and the @code{>>>}
10477 prefix can be used to search for error messages. When this switch is
10478 used the only source lines output are those with errors.
10481 @geindex -gnatl (gcc)
10486 @item @code{-gnatl}
10488 The @code{l} stands for list.
10489 This switch causes a full listing of
10490 the file to be generated. In the case where a body is
10491 compiled, the corresponding spec is also listed, along
10492 with any subunits. Typical output from compiling a package
10493 body @code{p.adb} might look like:
10498 1. package body p is
10500 3. procedure a is separate;
10511 2. pragma Elaborate_Body
10532 When you specify the @code{-gnatv} or @code{-gnatl} switches and
10533 standard output is redirected, a brief summary is written to
10534 @code{stderr} (standard error) giving the number of error messages and
10535 warning messages generated.
10538 @geindex -gnatl=fname (gcc)
10543 @item @code{-gnatl=@emph{fname}}
10545 This has the same effect as @code{-gnatl} except that the output is
10546 written to a file instead of to standard output. If the given name
10547 @code{fname} does not start with a period, then it is the full name
10548 of the file to be written. If @code{fname} is an extension, it is
10549 appended to the name of the file being compiled. For example, if
10550 file @code{xyz.adb} is compiled with @code{-gnatl=.lst},
10551 then the output is written to file xyz.adb.lst.
10554 @geindex -gnatU (gcc)
10559 @item @code{-gnatU}
10561 This switch forces all error messages to be preceded by the unique
10562 string 'error:'. This means that error messages take a few more
10563 characters in space, but allows easy searching for and identification
10567 @geindex -gnatb (gcc)
10572 @item @code{-gnatb}
10574 The @code{b} stands for brief.
10575 This switch causes GNAT to generate the
10576 brief format error messages to @code{stderr} (the standard error
10577 file) as well as the verbose
10578 format message or full listing (which as usual is written to
10579 @code{stdout} (the standard output file).
10582 @geindex -gnatm (gcc)
10587 @item @code{-gnatm=@emph{n}}
10589 The @code{m} stands for maximum.
10590 @code{n} is a decimal integer in the
10591 range of 1 to 999999 and limits the number of error or warning
10592 messages to be generated. For example, using
10593 @code{-gnatm2} might yield
10596 e.adb:3:04: Incorrect spelling of keyword "function"
10597 e.adb:5:35: missing ".."
10598 fatal error: maximum number of errors detected
10599 compilation abandoned
10602 The default setting if
10603 no switch is given is 9999. If the number of warnings reaches this
10604 limit, then a message is output and further warnings are suppressed,
10605 but the compilation is continued. If the number of error messages
10606 reaches this limit, then a message is output and the compilation
10607 is abandoned. A value of zero means that no limit applies.
10609 Note that the equal sign is optional, so the switches
10610 @code{-gnatm2} and @code{-gnatm=2} are equivalent.
10613 @geindex -gnatf (gcc)
10618 @item @code{-gnatf}
10620 @geindex Error messages
10621 @geindex suppressing
10623 The @code{f} stands for full.
10624 Normally, the compiler suppresses error messages that are likely to be
10625 redundant. This switch causes all error
10626 messages to be generated. In particular, in the case of
10627 references to undefined variables. If a given variable is referenced
10628 several times, the normal format of messages is
10631 e.adb:7:07: "V" is undefined (more references follow)
10634 where the parenthetical comment warns that there are additional
10635 references to the variable @code{V}. Compiling the same program with the
10636 @code{-gnatf} switch yields
10639 e.adb:7:07: "V" is undefined
10640 e.adb:8:07: "V" is undefined
10641 e.adb:8:12: "V" is undefined
10642 e.adb:8:16: "V" is undefined
10643 e.adb:9:07: "V" is undefined
10644 e.adb:9:12: "V" is undefined
10647 The @code{-gnatf} switch also generates additional information for
10648 some error messages. Some examples are:
10654 Details on possibly non-portable unchecked conversion
10657 List possible interpretations for ambiguous calls
10660 Additional details on incorrect parameters
10664 @geindex -gnatjnn (gcc)
10669 @item @code{-gnatjnn}
10671 In normal operation mode (or if @code{-gnatj0} is used), then error messages
10672 with continuation lines are treated as though the continuation lines were
10673 separate messages (and so a warning with two continuation lines counts as
10674 three warnings, and is listed as three separate messages).
10676 If the @code{-gnatjnn} switch is used with a positive value for nn, then
10677 messages are output in a different manner. A message and all its continuation
10678 lines are treated as a unit, and count as only one warning or message in the
10679 statistics totals. Furthermore, the message is reformatted so that no line
10680 is longer than nn characters.
10683 @geindex -gnatq (gcc)
10688 @item @code{-gnatq}
10690 The @code{q} stands for quit (really 'don't quit').
10691 In normal operation mode, the compiler first parses the program and
10692 determines if there are any syntax errors. If there are, appropriate
10693 error messages are generated and compilation is immediately terminated.
10695 GNAT to continue with semantic analysis even if syntax errors have been
10696 found. This may enable the detection of more errors in a single run. On
10697 the other hand, the semantic analyzer is more likely to encounter some
10698 internal fatal error when given a syntactically invalid tree.
10701 @geindex -gnatQ (gcc)
10706 @item @code{-gnatQ}
10708 In normal operation mode, the @code{ALI} file is not generated if any
10709 illegalities are detected in the program. The use of @code{-gnatQ} forces
10710 generation of the @code{ALI} file. This file is marked as being in
10711 error, so it cannot be used for binding purposes, but it does contain
10712 reasonably complete cross-reference information, and thus may be useful
10713 for use by tools (e.g., semantic browsing tools or integrated development
10714 environments) that are driven from the @code{ALI} file. This switch
10715 implies @code{-gnatq}, since the semantic phase must be run to get a
10716 meaningful ALI file.
10718 In addition, if @code{-gnatt} is also specified, then the tree file is
10719 generated even if there are illegalities. It may be useful in this case
10720 to also specify @code{-gnatq} to ensure that full semantic processing
10721 occurs. The resulting tree file can be processed by ASIS, for the purpose
10722 of providing partial information about illegal units, but if the error
10723 causes the tree to be badly malformed, then ASIS may crash during the
10726 When @code{-gnatQ} is used and the generated @code{ALI} file is marked as
10727 being in error, @code{gnatmake} will attempt to recompile the source when it
10728 finds such an @code{ALI} file, including with switch @code{-gnatc}.
10730 Note that @code{-gnatQ} has no effect if @code{-gnats} is specified,
10731 since ALI files are never generated if @code{-gnats} is set.
10734 @node Warning Message Control,Debugging and Assertion Control,Output and Error Message Control,Compiler Switches
10735 @anchor{gnat_ugn/building_executable_programs_with_gnat warning-message-control}@anchor{fa}@anchor{gnat_ugn/building_executable_programs_with_gnat id15}@anchor{ff}
10736 @subsection Warning Message Control
10739 @geindex Warning messages
10741 In addition to error messages, which correspond to illegalities as defined
10742 in the Ada Reference Manual, the compiler detects two kinds of warning
10745 First, the compiler considers some constructs suspicious and generates a
10746 warning message to alert you to a possible error. Second, if the
10747 compiler detects a situation that is sure to raise an exception at
10748 run time, it generates a warning message. The following shows an example
10749 of warning messages:
10752 e.adb:4:24: warning: creation of object may raise Storage_Error
10753 e.adb:10:17: warning: static value out of range
10754 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
10757 GNAT considers a large number of situations as appropriate
10758 for the generation of warning messages. As always, warnings are not
10759 definite indications of errors. For example, if you do an out-of-range
10760 assignment with the deliberate intention of raising a
10761 @code{Constraint_Error} exception, then the warning that may be
10762 issued does not indicate an error. Some of the situations for which GNAT
10763 issues warnings (at least some of the time) are given in the following
10764 list. This list is not complete, and new warnings are often added to
10765 subsequent versions of GNAT. The list is intended to give a general idea
10766 of the kinds of warnings that are generated.
10772 Possible infinitely recursive calls
10775 Out-of-range values being assigned
10778 Possible order of elaboration problems
10781 Size not a multiple of alignment for a record type
10784 Assertions (pragma Assert) that are sure to fail
10790 Address clauses with possibly unaligned values, or where an attempt is
10791 made to overlay a smaller variable with a larger one.
10794 Fixed-point type declarations with a null range
10797 Direct_IO or Sequential_IO instantiated with a type that has access values
10800 Variables that are never assigned a value
10803 Variables that are referenced before being initialized
10806 Task entries with no corresponding @code{accept} statement
10809 Duplicate accepts for the same task entry in a @code{select}
10812 Objects that take too much storage
10815 Unchecked conversion between types of differing sizes
10818 Missing @code{return} statement along some execution path in a function
10821 Incorrect (unrecognized) pragmas
10824 Incorrect external names
10827 Allocation from empty storage pool
10830 Potentially blocking operation in protected type
10833 Suspicious parenthesization of expressions
10836 Mismatching bounds in an aggregate
10839 Attempt to return local value by reference
10842 Premature instantiation of a generic body
10845 Attempt to pack aliased components
10848 Out of bounds array subscripts
10851 Wrong length on string assignment
10854 Violations of style rules if style checking is enabled
10857 Unused @emph{with} clauses
10860 @code{Bit_Order} usage that does not have any effect
10863 @code{Standard.Duration} used to resolve universal fixed expression
10866 Dereference of possibly null value
10869 Declaration that is likely to cause storage error
10872 Internal GNAT unit @emph{with}ed by application unit
10875 Values known to be out of range at compile time
10878 Unreferenced or unmodified variables. Note that a special
10879 exemption applies to variables which contain any of the substrings
10880 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED}, in any casing. Such variables
10881 are considered likely to be intentionally used in a situation where
10882 otherwise a warning would be given, so warnings of this kind are
10883 always suppressed for such variables.
10886 Address overlays that could clobber memory
10889 Unexpected initialization when address clause present
10892 Bad alignment for address clause
10895 Useless type conversions
10898 Redundant assignment statements and other redundant constructs
10901 Useless exception handlers
10904 Accidental hiding of name by child unit
10907 Access before elaboration detected at compile time
10910 A range in a @code{for} loop that is known to be null or might be null
10913 The following section lists compiler switches that are available
10914 to control the handling of warning messages. It is also possible
10915 to exercise much finer control over what warnings are issued and
10916 suppressed using the GNAT pragma Warnings (see the description
10917 of the pragma in the @cite{GNAT_Reference_manual}).
10919 @geindex -gnatwa (gcc)
10924 @item @code{-gnatwa}
10926 @emph{Activate most optional warnings.}
10928 This switch activates most optional warning messages. See the remaining list
10929 in this section for details on optional warning messages that can be
10930 individually controlled. The warnings that are not turned on by this
10937 @code{-gnatwd} (implicit dereferencing)
10940 @code{-gnatw.d} (tag warnings with -gnatw switch)
10943 @code{-gnatwh} (hiding)
10946 @code{-gnatw.h} (holes in record layouts)
10949 @code{-gnatw.j} (late primitives of tagged types)
10952 @code{-gnatw.k} (redefinition of names in standard)
10955 @code{-gnatwl} (elaboration warnings)
10958 @code{-gnatw.l} (inherited aspects)
10961 @code{-gnatw.n} (atomic synchronization)
10964 @code{-gnatwo} (address clause overlay)
10967 @code{-gnatw.o} (values set by out parameters ignored)
10970 @code{-gnatw.q} (questionable layout of record types)
10973 @code{-gnatw_r} (out-of-order record representation clauses)
10976 @code{-gnatw.s} (overridden size clause)
10979 @code{-gnatwt} (tracking of deleted conditional code)
10982 @code{-gnatw.u} (unordered enumeration)
10985 @code{-gnatw.w} (use of Warnings Off)
10988 @code{-gnatw.y} (reasons for package needing body)
10991 All other optional warnings are turned on.
10994 @geindex -gnatwA (gcc)
10999 @item @code{-gnatwA}
11001 @emph{Suppress all optional errors.}
11003 This switch suppresses all optional warning messages, see remaining list
11004 in this section for details on optional warning messages that can be
11005 individually controlled. Note that unlike switch @code{-gnatws}, the
11006 use of switch @code{-gnatwA} does not suppress warnings that are
11007 normally given unconditionally and cannot be individually controlled
11008 (for example, the warning about a missing exit path in a function).
11009 Also, again unlike switch @code{-gnatws}, warnings suppressed by
11010 the use of switch @code{-gnatwA} can be individually turned back
11011 on. For example the use of switch @code{-gnatwA} followed by
11012 switch @code{-gnatwd} will suppress all optional warnings except
11013 the warnings for implicit dereferencing.
11016 @geindex -gnatw.a (gcc)
11021 @item @code{-gnatw.a}
11023 @emph{Activate warnings on failing assertions.}
11025 @geindex Assert failures
11027 This switch activates warnings for assertions where the compiler can tell at
11028 compile time that the assertion will fail. Note that this warning is given
11029 even if assertions are disabled. The default is that such warnings are
11033 @geindex -gnatw.A (gcc)
11038 @item @code{-gnatw.A}
11040 @emph{Suppress warnings on failing assertions.}
11042 @geindex Assert failures
11044 This switch suppresses warnings for assertions where the compiler can tell at
11045 compile time that the assertion will fail.
11053 @item @code{-gnatw_a}
11055 @emph{Activate warnings on anonymous allocators.}
11057 @geindex Anonymous allocators
11059 This switch activates warnings for allocators of anonymous access types,
11060 which can involve run-time accessibility checks and lead to unexpected
11061 accessibility violations. For more details on the rules involved, see
11070 @item @code{-gnatw_A}
11072 @emph{Supress warnings on anonymous allocators.}
11074 @geindex Anonymous allocators
11076 This switch suppresses warnings for anonymous access type allocators.
11079 @geindex -gnatwb (gcc)
11084 @item @code{-gnatwb}
11086 @emph{Activate warnings on bad fixed values.}
11088 @geindex Bad fixed values
11090 @geindex Fixed-point Small value
11092 @geindex Small value
11094 This switch activates warnings for static fixed-point expressions whose
11095 value is not an exact multiple of Small. Such values are implementation
11096 dependent, since an implementation is free to choose either of the multiples
11097 that surround the value. GNAT always chooses the closer one, but this is not
11098 required behavior, and it is better to specify a value that is an exact
11099 multiple, ensuring predictable execution. The default is that such warnings
11103 @geindex -gnatwB (gcc)
11108 @item @code{-gnatwB}
11110 @emph{Suppress warnings on bad fixed values.}
11112 This switch suppresses warnings for static fixed-point expressions whose
11113 value is not an exact multiple of Small.
11116 @geindex -gnatw.b (gcc)
11121 @item @code{-gnatw.b}
11123 @emph{Activate warnings on biased representation.}
11125 @geindex Biased representation
11127 This switch activates warnings when a size clause, value size clause, component
11128 clause, or component size clause forces the use of biased representation for an
11129 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
11130 to represent 10/11). The default is that such warnings are generated.
11133 @geindex -gnatwB (gcc)
11138 @item @code{-gnatw.B}
11140 @emph{Suppress warnings on biased representation.}
11142 This switch suppresses warnings for representation clauses that force the use
11143 of biased representation.
11146 @geindex -gnatwc (gcc)
11151 @item @code{-gnatwc}
11153 @emph{Activate warnings on conditionals.}
11155 @geindex Conditionals
11158 This switch activates warnings for conditional expressions used in
11159 tests that are known to be True or False at compile time. The default
11160 is that such warnings are not generated.
11161 Note that this warning does
11162 not get issued for the use of boolean variables or constants whose
11163 values are known at compile time, since this is a standard technique
11164 for conditional compilation in Ada, and this would generate too many
11165 false positive warnings.
11167 This warning option also activates a special test for comparisons using
11168 the operators '>=' and' <='.
11169 If the compiler can tell that only the equality condition is possible,
11170 then it will warn that the '>' or '<' part of the test
11171 is useless and that the operator could be replaced by '='.
11172 An example would be comparing a @code{Natural} variable <= 0.
11174 This warning option also generates warnings if
11175 one or both tests is optimized away in a membership test for integer
11176 values if the result can be determined at compile time. Range tests on
11177 enumeration types are not included, since it is common for such tests
11178 to include an end point.
11180 This warning can also be turned on using @code{-gnatwa}.
11183 @geindex -gnatwC (gcc)
11188 @item @code{-gnatwC}
11190 @emph{Suppress warnings on conditionals.}
11192 This switch suppresses warnings for conditional expressions used in
11193 tests that are known to be True or False at compile time.
11196 @geindex -gnatw.c (gcc)
11201 @item @code{-gnatw.c}
11203 @emph{Activate warnings on missing component clauses.}
11205 @geindex Component clause
11208 This switch activates warnings for record components where a record
11209 representation clause is present and has component clauses for the
11210 majority, but not all, of the components. A warning is given for each
11211 component for which no component clause is present.
11214 @geindex -gnatw.C (gcc)
11219 @item @code{-gnatw.C}
11221 @emph{Suppress warnings on missing component clauses.}
11223 This switch suppresses warnings for record components that are
11224 missing a component clause in the situation described above.
11227 @geindex -gnatw_c (gcc)
11232 @item @code{-gnatw_c}
11234 @emph{Activate warnings on unknown condition in Compile_Time_Warning.}
11236 @geindex Compile_Time_Warning
11238 @geindex Compile_Time_Error
11240 This switch activates warnings on a pragma Compile_Time_Warning
11241 or Compile_Time_Error whose condition has a value that is not
11242 known at compile time.
11243 The default is that such warnings are generated.
11246 @geindex -gnatw_C (gcc)
11251 @item @code{-gnatw_C}
11253 @emph{Suppress warnings on missing component clauses.}
11255 This switch supresses warnings on a pragma Compile_Time_Warning
11256 or Compile_Time_Error whose condition has a value that is not
11257 known at compile time.
11260 @geindex -gnatwd (gcc)
11265 @item @code{-gnatwd}
11267 @emph{Activate warnings on implicit dereferencing.}
11269 If this switch is set, then the use of a prefix of an access type
11270 in an indexed component, slice, or selected component without an
11271 explicit @code{.all} will generate a warning. With this warning
11272 enabled, access checks occur only at points where an explicit
11273 @code{.all} appears in the source code (assuming no warnings are
11274 generated as a result of this switch). The default is that such
11275 warnings are not generated.
11278 @geindex -gnatwD (gcc)
11283 @item @code{-gnatwD}
11285 @emph{Suppress warnings on implicit dereferencing.}
11287 @geindex Implicit dereferencing
11289 @geindex Dereferencing
11292 This switch suppresses warnings for implicit dereferences in
11293 indexed components, slices, and selected components.
11296 @geindex -gnatw.d (gcc)
11301 @item @code{-gnatw.d}
11303 @emph{Activate tagging of warning and info messages.}
11305 If this switch is set, then warning messages are tagged, with one of the
11315 Used to tag warnings controlled by the switch @code{-gnatwx} where x
11320 Used to tag warnings controlled by the switch @code{-gnatw.x} where x
11325 Used to tag elaboration information (info) messages generated when the
11326 static model of elaboration is used and the @code{-gnatel} switch is set.
11329 @emph{[restriction warning]}
11330 Used to tag warning messages for restriction violations, activated by use
11331 of the pragma @code{Restriction_Warnings}.
11334 @emph{[warning-as-error]}
11335 Used to tag warning messages that have been converted to error messages by
11336 use of the pragma Warning_As_Error. Note that such warnings are prefixed by
11337 the string "error: " rather than "warning: ".
11340 @emph{[enabled by default]}
11341 Used to tag all other warnings that are always given by default, unless
11342 warnings are completely suppressed using pragma @emph{Warnings(Off)} or
11343 the switch @code{-gnatws}.
11348 @geindex -gnatw.d (gcc)
11353 @item @code{-gnatw.D}
11355 @emph{Deactivate tagging of warning and info messages messages.}
11357 If this switch is set, then warning messages return to the default
11358 mode in which warnings and info messages are not tagged as described above for
11362 @geindex -gnatwe (gcc)
11365 @geindex treat as error
11370 @item @code{-gnatwe}
11372 @emph{Treat warnings and style checks as errors.}
11374 This switch causes warning messages and style check messages to be
11376 The warning string still appears, but the warning messages are counted
11377 as errors, and prevent the generation of an object file. Note that this
11378 is the only -gnatw switch that affects the handling of style check messages.
11379 Note also that this switch has no effect on info (information) messages, which
11380 are not treated as errors if this switch is present.
11383 @geindex -gnatw.e (gcc)
11388 @item @code{-gnatw.e}
11390 @emph{Activate every optional warning.}
11393 @geindex activate every optional warning
11395 This switch activates all optional warnings, including those which
11396 are not activated by @code{-gnatwa}. The use of this switch is not
11397 recommended for normal use. If you turn this switch on, it is almost
11398 certain that you will get large numbers of useless warnings. The
11399 warnings that are excluded from @code{-gnatwa} are typically highly
11400 specialized warnings that are suitable for use only in code that has
11401 been specifically designed according to specialized coding rules.
11404 @geindex -gnatwE (gcc)
11407 @geindex treat as error
11412 @item @code{-gnatwE}
11414 @emph{Treat all run-time exception warnings as errors.}
11416 This switch causes warning messages regarding errors that will be raised
11417 during run-time execution to be treated as errors.
11420 @geindex -gnatwf (gcc)
11425 @item @code{-gnatwf}
11427 @emph{Activate warnings on unreferenced formals.}
11430 @geindex unreferenced
11432 This switch causes a warning to be generated if a formal parameter
11433 is not referenced in the body of the subprogram. This warning can
11434 also be turned on using @code{-gnatwu}. The
11435 default is that these warnings are not generated.
11438 @geindex -gnatwF (gcc)
11443 @item @code{-gnatwF}
11445 @emph{Suppress warnings on unreferenced formals.}
11447 This switch suppresses warnings for unreferenced formal
11448 parameters. Note that the
11449 combination @code{-gnatwu} followed by @code{-gnatwF} has the
11450 effect of warning on unreferenced entities other than subprogram
11454 @geindex -gnatwg (gcc)
11459 @item @code{-gnatwg}
11461 @emph{Activate warnings on unrecognized pragmas.}
11464 @geindex unrecognized
11466 This switch causes a warning to be generated if an unrecognized
11467 pragma is encountered. Apart from issuing this warning, the
11468 pragma is ignored and has no effect. The default
11469 is that such warnings are issued (satisfying the Ada Reference
11470 Manual requirement that such warnings appear).
11473 @geindex -gnatwG (gcc)
11478 @item @code{-gnatwG}
11480 @emph{Suppress warnings on unrecognized pragmas.}
11482 This switch suppresses warnings for unrecognized pragmas.
11485 @geindex -gnatw.g (gcc)
11490 @item @code{-gnatw.g}
11492 @emph{Warnings used for GNAT sources.}
11494 This switch sets the warning categories that are used by the standard
11495 GNAT style. Currently this is equivalent to
11496 @code{-gnatwAao.q.s.CI.V.X.Z}
11497 but more warnings may be added in the future without advanced notice.
11500 @geindex -gnatwh (gcc)
11505 @item @code{-gnatwh}
11507 @emph{Activate warnings on hiding.}
11509 @geindex Hiding of Declarations
11511 This switch activates warnings on hiding declarations that are considered
11512 potentially confusing. Not all cases of hiding cause warnings; for example an
11513 overriding declaration hides an implicit declaration, which is just normal
11514 code. The default is that warnings on hiding are not generated.
11517 @geindex -gnatwH (gcc)
11522 @item @code{-gnatwH}
11524 @emph{Suppress warnings on hiding.}
11526 This switch suppresses warnings on hiding declarations.
11529 @geindex -gnatw.h (gcc)
11534 @item @code{-gnatw.h}
11536 @emph{Activate warnings on holes/gaps in records.}
11538 @geindex Record Representation (gaps)
11540 This switch activates warnings on component clauses in record
11541 representation clauses that leave holes (gaps) in the record layout.
11542 If this warning option is active, then record representation clauses
11543 should specify a contiguous layout, adding unused fill fields if needed.
11546 @geindex -gnatw.H (gcc)
11551 @item @code{-gnatw.H}
11553 @emph{Suppress warnings on holes/gaps in records.}
11555 This switch suppresses warnings on component clauses in record
11556 representation clauses that leave holes (haps) in the record layout.
11559 @geindex -gnatwi (gcc)
11564 @item @code{-gnatwi}
11566 @emph{Activate warnings on implementation units.}
11568 This switch activates warnings for a @emph{with} of an internal GNAT
11569 implementation unit, defined as any unit from the @code{Ada},
11570 @code{Interfaces}, @code{GNAT},
11572 hierarchies that is not
11573 documented in either the Ada Reference Manual or the GNAT
11574 Programmer's Reference Manual. Such units are intended only
11575 for internal implementation purposes and should not be @emph{with}ed
11576 by user programs. The default is that such warnings are generated
11579 @geindex -gnatwI (gcc)
11584 @item @code{-gnatwI}
11586 @emph{Disable warnings on implementation units.}
11588 This switch disables warnings for a @emph{with} of an internal GNAT
11589 implementation unit.
11592 @geindex -gnatw.i (gcc)
11597 @item @code{-gnatw.i}
11599 @emph{Activate warnings on overlapping actuals.}
11601 This switch enables a warning on statically detectable overlapping actuals in
11602 a subprogram call, when one of the actuals is an in-out parameter, and the
11603 types of the actuals are not by-copy types. This warning is off by default.
11606 @geindex -gnatw.I (gcc)
11611 @item @code{-gnatw.I}
11613 @emph{Disable warnings on overlapping actuals.}
11615 This switch disables warnings on overlapping actuals in a call..
11618 @geindex -gnatwj (gcc)
11623 @item @code{-gnatwj}
11625 @emph{Activate warnings on obsolescent features (Annex J).}
11628 @geindex obsolescent
11630 @geindex Obsolescent features
11632 If this warning option is activated, then warnings are generated for
11633 calls to subprograms marked with @code{pragma Obsolescent} and
11634 for use of features in Annex J of the Ada Reference Manual. In the
11635 case of Annex J, not all features are flagged. In particular use
11636 of the renamed packages (like @code{Text_IO}) and use of package
11637 @code{ASCII} are not flagged, since these are very common and
11638 would generate many annoying positive warnings. The default is that
11639 such warnings are not generated.
11641 In addition to the above cases, warnings are also generated for
11642 GNAT features that have been provided in past versions but which
11643 have been superseded (typically by features in the new Ada standard).
11644 For example, @code{pragma Ravenscar} will be flagged since its
11645 function is replaced by @code{pragma Profile(Ravenscar)}, and
11646 @code{pragma Interface_Name} will be flagged since its function
11647 is replaced by @code{pragma Import}.
11649 Note that this warning option functions differently from the
11650 restriction @code{No_Obsolescent_Features} in two respects.
11651 First, the restriction applies only to annex J features.
11652 Second, the restriction does flag uses of package @code{ASCII}.
11655 @geindex -gnatwJ (gcc)
11660 @item @code{-gnatwJ}
11662 @emph{Suppress warnings on obsolescent features (Annex J).}
11664 This switch disables warnings on use of obsolescent features.
11667 @geindex -gnatw.j (gcc)
11672 @item @code{-gnatw.j}
11674 @emph{Activate warnings on late declarations of tagged type primitives.}
11676 This switch activates warnings on visible primitives added to a
11677 tagged type after deriving a private extension from it.
11680 @geindex -gnatw.J (gcc)
11685 @item @code{-gnatw.J}
11687 @emph{Suppress warnings on late declarations of tagged type primitives.}
11689 This switch suppresses warnings on visible primitives added to a
11690 tagged type after deriving a private extension from it.
11693 @geindex -gnatwk (gcc)
11698 @item @code{-gnatwk}
11700 @emph{Activate warnings on variables that could be constants.}
11702 This switch activates warnings for variables that are initialized but
11703 never modified, and then could be declared constants. The default is that
11704 such warnings are not given.
11707 @geindex -gnatwK (gcc)
11712 @item @code{-gnatwK}
11714 @emph{Suppress warnings on variables that could be constants.}
11716 This switch disables warnings on variables that could be declared constants.
11719 @geindex -gnatw.k (gcc)
11724 @item @code{-gnatw.k}
11726 @emph{Activate warnings on redefinition of names in standard.}
11728 This switch activates warnings for declarations that declare a name that
11729 is defined in package Standard. Such declarations can be confusing,
11730 especially since the names in package Standard continue to be directly
11731 visible, meaning that use visibiliy on such redeclared names does not
11732 work as expected. Names of discriminants and components in records are
11733 not included in this check.
11736 @geindex -gnatwK (gcc)
11741 @item @code{-gnatw.K}
11743 @emph{Suppress warnings on redefinition of names in standard.}
11745 This switch activates warnings for declarations that declare a name that
11746 is defined in package Standard.
11749 @geindex -gnatwl (gcc)
11754 @item @code{-gnatwl}
11756 @emph{Activate warnings for elaboration pragmas.}
11758 @geindex Elaboration
11761 This switch activates warnings for possible elaboration problems,
11762 including suspicious use
11763 of @code{Elaborate} pragmas, when using the static elaboration model, and
11764 possible situations that may raise @code{Program_Error} when using the
11765 dynamic elaboration model.
11766 See the section in this guide on elaboration checking for further details.
11767 The default is that such warnings
11771 @geindex -gnatwL (gcc)
11776 @item @code{-gnatwL}
11778 @emph{Suppress warnings for elaboration pragmas.}
11780 This switch suppresses warnings for possible elaboration problems.
11783 @geindex -gnatw.l (gcc)
11788 @item @code{-gnatw.l}
11790 @emph{List inherited aspects.}
11792 This switch causes the compiler to list inherited invariants,
11793 preconditions, and postconditions from Type_Invariant'Class, Invariant'Class,
11794 Pre'Class, and Post'Class aspects. Also list inherited subtype predicates.
11797 @geindex -gnatw.L (gcc)
11802 @item @code{-gnatw.L}
11804 @emph{Suppress listing of inherited aspects.}
11806 This switch suppresses listing of inherited aspects.
11809 @geindex -gnatwm (gcc)
11814 @item @code{-gnatwm}
11816 @emph{Activate warnings on modified but unreferenced variables.}
11818 This switch activates warnings for variables that are assigned (using
11819 an initialization value or with one or more assignment statements) but
11820 whose value is never read. The warning is suppressed for volatile
11821 variables and also for variables that are renamings of other variables
11822 or for which an address clause is given.
11823 The default is that these warnings are not given.
11826 @geindex -gnatwM (gcc)
11831 @item @code{-gnatwM}
11833 @emph{Disable warnings on modified but unreferenced variables.}
11835 This switch disables warnings for variables that are assigned or
11836 initialized, but never read.
11839 @geindex -gnatw.m (gcc)
11844 @item @code{-gnatw.m}
11846 @emph{Activate warnings on suspicious modulus values.}
11848 This switch activates warnings for modulus values that seem suspicious.
11849 The cases caught are where the size is the same as the modulus (e.g.
11850 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
11851 with no size clause. The guess in both cases is that 2**x was intended
11852 rather than x. In addition expressions of the form 2*x for small x
11853 generate a warning (the almost certainly accurate guess being that
11854 2**x was intended). The default is that these warnings are given.
11857 @geindex -gnatw.M (gcc)
11862 @item @code{-gnatw.M}
11864 @emph{Disable warnings on suspicious modulus values.}
11866 This switch disables warnings for suspicious modulus values.
11869 @geindex -gnatwn (gcc)
11874 @item @code{-gnatwn}
11876 @emph{Set normal warnings mode.}
11878 This switch sets normal warning mode, in which enabled warnings are
11879 issued and treated as warnings rather than errors. This is the default
11880 mode. the switch @code{-gnatwn} can be used to cancel the effect of
11881 an explicit @code{-gnatws} or
11882 @code{-gnatwe}. It also cancels the effect of the
11883 implicit @code{-gnatwe} that is activated by the
11884 use of @code{-gnatg}.
11887 @geindex -gnatw.n (gcc)
11889 @geindex Atomic Synchronization
11895 @item @code{-gnatw.n}
11897 @emph{Activate warnings on atomic synchronization.}
11899 This switch actives warnings when an access to an atomic variable
11900 requires the generation of atomic synchronization code. These
11901 warnings are off by default.
11904 @geindex -gnatw.N (gcc)
11909 @item @code{-gnatw.N}
11911 @emph{Suppress warnings on atomic synchronization.}
11913 @geindex Atomic Synchronization
11916 This switch suppresses warnings when an access to an atomic variable
11917 requires the generation of atomic synchronization code.
11920 @geindex -gnatwo (gcc)
11922 @geindex Address Clauses
11928 @item @code{-gnatwo}
11930 @emph{Activate warnings on address clause overlays.}
11932 This switch activates warnings for possibly unintended initialization
11933 effects of defining address clauses that cause one variable to overlap
11934 another. The default is that such warnings are generated.
11937 @geindex -gnatwO (gcc)
11942 @item @code{-gnatwO}
11944 @emph{Suppress warnings on address clause overlays.}
11946 This switch suppresses warnings on possibly unintended initialization
11947 effects of defining address clauses that cause one variable to overlap
11951 @geindex -gnatw.o (gcc)
11956 @item @code{-gnatw.o}
11958 @emph{Activate warnings on modified but unreferenced out parameters.}
11960 This switch activates warnings for variables that are modified by using
11961 them as actuals for a call to a procedure with an out mode formal, where
11962 the resulting assigned value is never read. It is applicable in the case
11963 where there is more than one out mode formal. If there is only one out
11964 mode formal, the warning is issued by default (controlled by -gnatwu).
11965 The warning is suppressed for volatile
11966 variables and also for variables that are renamings of other variables
11967 or for which an address clause is given.
11968 The default is that these warnings are not given.
11971 @geindex -gnatw.O (gcc)
11976 @item @code{-gnatw.O}
11978 @emph{Disable warnings on modified but unreferenced out parameters.}
11980 This switch suppresses warnings for variables that are modified by using
11981 them as actuals for a call to a procedure with an out mode formal, where
11982 the resulting assigned value is never read.
11985 @geindex -gnatwp (gcc)
11993 @item @code{-gnatwp}
11995 @emph{Activate warnings on ineffective pragma Inlines.}
11997 This switch activates warnings for failure of front end inlining
11998 (activated by @code{-gnatN}) to inline a particular call. There are
11999 many reasons for not being able to inline a call, including most
12000 commonly that the call is too complex to inline. The default is
12001 that such warnings are not given.
12002 Warnings on ineffective inlining by the gcc back-end can be activated
12003 separately, using the gcc switch -Winline.
12006 @geindex -gnatwP (gcc)
12011 @item @code{-gnatwP}
12013 @emph{Suppress warnings on ineffective pragma Inlines.}
12015 This switch suppresses warnings on ineffective pragma Inlines. If the
12016 inlining mechanism cannot inline a call, it will simply ignore the
12020 @geindex -gnatw.p (gcc)
12022 @geindex Parameter order
12028 @item @code{-gnatw.p}
12030 @emph{Activate warnings on parameter ordering.}
12032 This switch activates warnings for cases of suspicious parameter
12033 ordering when the list of arguments are all simple identifiers that
12034 match the names of the formals, but are in a different order. The
12035 warning is suppressed if any use of named parameter notation is used,
12036 so this is the appropriate way to suppress a false positive (and
12037 serves to emphasize that the "misordering" is deliberate). The
12038 default is that such warnings are not given.
12041 @geindex -gnatw.P (gcc)
12046 @item @code{-gnatw.P}
12048 @emph{Suppress warnings on parameter ordering.}
12050 This switch suppresses warnings on cases of suspicious parameter
12054 @geindex -gnatwq (gcc)
12056 @geindex Parentheses
12062 @item @code{-gnatwq}
12064 @emph{Activate warnings on questionable missing parentheses.}
12066 This switch activates warnings for cases where parentheses are not used and
12067 the result is potential ambiguity from a readers point of view. For example
12068 (not a > b) when a and b are modular means ((not a) > b) and very likely the
12069 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
12070 quite likely ((-x) mod 5) was intended. In such situations it seems best to
12071 follow the rule of always parenthesizing to make the association clear, and
12072 this warning switch warns if such parentheses are not present. The default
12073 is that these warnings are given.
12076 @geindex -gnatwQ (gcc)
12081 @item @code{-gnatwQ}
12083 @emph{Suppress warnings on questionable missing parentheses.}
12085 This switch suppresses warnings for cases where the association is not
12086 clear and the use of parentheses is preferred.
12089 @geindex -gnatw.q (gcc)
12097 @item @code{-gnatw.q}
12099 @emph{Activate warnings on questionable layout of record types.}
12101 This switch activates warnings for cases where the default layout of
12102 a record type, that is to say the layout of its components in textual
12103 order of the source code, would very likely cause inefficiencies in
12104 the code generated by the compiler, both in terms of space and speed
12105 during execution. One warning is issued for each problematic component
12106 without representation clause in the nonvariant part and then in each
12107 variant recursively, if any.
12109 The purpose of these warnings is neither to prescribe an optimal layout
12110 nor to force the use of representation clauses, but rather to get rid of
12111 the most blatant inefficiencies in the layout. Therefore, the default
12112 layout is matched against the following synthetic ordered layout and
12113 the deviations are flagged on a component-by-component basis:
12119 first all components or groups of components whose length is fixed
12120 and a multiple of the storage unit,
12123 then the remaining components whose length is fixed and not a multiple
12124 of the storage unit,
12127 then the remaining components whose length doesn't depend on discriminants
12128 (that is to say, with variable but uniform length for all objects),
12131 then all components whose length depends on discriminants,
12134 finally the variant part (if any),
12137 for the nonvariant part and for each variant recursively, if any.
12139 The exact wording of the warning depends on whether the compiler is allowed
12140 to reorder the components in the record type or precluded from doing it by
12141 means of pragma @code{No_Component_Reordering}.
12143 The default is that these warnings are not given.
12146 @geindex -gnatw.Q (gcc)
12151 @item @code{-gnatw.Q}
12153 @emph{Suppress warnings on questionable layout of record types.}
12155 This switch suppresses warnings for cases where the default layout of
12156 a record type would very likely cause inefficiencies.
12159 @geindex -gnatwr (gcc)
12164 @item @code{-gnatwr}
12166 @emph{Activate warnings on redundant constructs.}
12168 This switch activates warnings for redundant constructs. The following
12169 is the current list of constructs regarded as redundant:
12175 Assignment of an item to itself.
12178 Type conversion that converts an expression to its own type.
12181 Use of the attribute @code{Base} where @code{typ'Base} is the same
12185 Use of pragma @code{Pack} when all components are placed by a record
12186 representation clause.
12189 Exception handler containing only a reraise statement (raise with no
12190 operand) which has no effect.
12193 Use of the operator abs on an operand that is known at compile time
12197 Comparison of an object or (unary or binary) operation of boolean type to
12198 an explicit True value.
12201 The default is that warnings for redundant constructs are not given.
12204 @geindex -gnatwR (gcc)
12209 @item @code{-gnatwR}
12211 @emph{Suppress warnings on redundant constructs.}
12213 This switch suppresses warnings for redundant constructs.
12216 @geindex -gnatw.r (gcc)
12221 @item @code{-gnatw.r}
12223 @emph{Activate warnings for object renaming function.}
12225 This switch activates warnings for an object renaming that renames a
12226 function call, which is equivalent to a constant declaration (as
12227 opposed to renaming the function itself). The default is that these
12228 warnings are given.
12231 @geindex -gnatw.R (gcc)
12236 @item @code{-gnatw.R}
12238 @emph{Suppress warnings for object renaming function.}
12240 This switch suppresses warnings for object renaming function.
12243 @geindex -gnatw_r (gcc)
12248 @item @code{-gnatw_r}
12250 @emph{Activate warnings for out-of-order record representation clauses.}
12252 This switch activates warnings for record representation clauses,
12253 if the order of component declarations, component clauses,
12254 and bit-level layout do not all agree.
12255 The default is that these warnings are not given.
12258 @geindex -gnatw_R (gcc)
12263 @item @code{-gnatw_R}
12265 @emph{Suppress warnings for out-of-order record representation clauses.}
12268 @geindex -gnatws (gcc)
12273 @item @code{-gnatws}
12275 @emph{Suppress all warnings.}
12277 This switch completely suppresses the
12278 output of all warning messages from the GNAT front end, including
12279 both warnings that can be controlled by switches described in this
12280 section, and those that are normally given unconditionally. The
12281 effect of this suppress action can only be cancelled by a subsequent
12282 use of the switch @code{-gnatwn}.
12284 Note that switch @code{-gnatws} does not suppress
12285 warnings from the @code{gcc} back end.
12286 To suppress these back end warnings as well, use the switch @code{-w}
12287 in addition to @code{-gnatws}. Also this switch has no effect on the
12288 handling of style check messages.
12291 @geindex -gnatw.s (gcc)
12293 @geindex Record Representation (component sizes)
12298 @item @code{-gnatw.s}
12300 @emph{Activate warnings on overridden size clauses.}
12302 This switch activates warnings on component clauses in record
12303 representation clauses where the length given overrides that
12304 specified by an explicit size clause for the component type. A
12305 warning is similarly given in the array case if a specified
12306 component size overrides an explicit size clause for the array
12310 @geindex -gnatw.S (gcc)
12315 @item @code{-gnatw.S}
12317 @emph{Suppress warnings on overridden size clauses.}
12319 This switch suppresses warnings on component clauses in record
12320 representation clauses that override size clauses, and similar
12321 warnings when an array component size overrides a size clause.
12324 @geindex -gnatwt (gcc)
12326 @geindex Deactivated code
12329 @geindex Deleted code
12335 @item @code{-gnatwt}
12337 @emph{Activate warnings for tracking of deleted conditional code.}
12339 This switch activates warnings for tracking of code in conditionals (IF and
12340 CASE statements) that is detected to be dead code which cannot be executed, and
12341 which is removed by the front end. This warning is off by default. This may be
12342 useful for detecting deactivated code in certified applications.
12345 @geindex -gnatwT (gcc)
12350 @item @code{-gnatwT}
12352 @emph{Suppress warnings for tracking of deleted conditional code.}
12354 This switch suppresses warnings for tracking of deleted conditional code.
12357 @geindex -gnatw.t (gcc)
12362 @item @code{-gnatw.t}
12364 @emph{Activate warnings on suspicious contracts.}
12366 This switch activates warnings on suspicious contracts. This includes
12367 warnings on suspicious postconditions (whether a pragma @code{Postcondition} or a
12368 @code{Post} aspect in Ada 2012) and suspicious contract cases (pragma or aspect
12369 @code{Contract_Cases}). A function postcondition or contract case is suspicious
12370 when no postcondition or contract case for this function mentions the result
12371 of the function. A procedure postcondition or contract case is suspicious
12372 when it only refers to the pre-state of the procedure, because in that case
12373 it should rather be expressed as a precondition. This switch also controls
12374 warnings on suspicious cases of expressions typically found in contracts like
12375 quantified expressions and uses of Update attribute. The default is that such
12376 warnings are generated.
12379 @geindex -gnatw.T (gcc)
12384 @item @code{-gnatw.T}
12386 @emph{Suppress warnings on suspicious contracts.}
12388 This switch suppresses warnings on suspicious contracts.
12391 @geindex -gnatwu (gcc)
12396 @item @code{-gnatwu}
12398 @emph{Activate warnings on unused entities.}
12400 This switch activates warnings to be generated for entities that
12401 are declared but not referenced, and for units that are @emph{with}ed
12403 referenced. In the case of packages, a warning is also generated if
12404 no entities in the package are referenced. This means that if a with'ed
12405 package is referenced but the only references are in @code{use}
12406 clauses or @code{renames}
12407 declarations, a warning is still generated. A warning is also generated
12408 for a generic package that is @emph{with}ed but never instantiated.
12409 In the case where a package or subprogram body is compiled, and there
12410 is a @emph{with} on the corresponding spec
12411 that is only referenced in the body,
12412 a warning is also generated, noting that the
12413 @emph{with} can be moved to the body. The default is that
12414 such warnings are not generated.
12415 This switch also activates warnings on unreferenced formals
12416 (it includes the effect of @code{-gnatwf}).
12419 @geindex -gnatwU (gcc)
12424 @item @code{-gnatwU}
12426 @emph{Suppress warnings on unused entities.}
12428 This switch suppresses warnings for unused entities and packages.
12429 It also turns off warnings on unreferenced formals (and thus includes
12430 the effect of @code{-gnatwF}).
12433 @geindex -gnatw.u (gcc)
12438 @item @code{-gnatw.u}
12440 @emph{Activate warnings on unordered enumeration types.}
12442 This switch causes enumeration types to be considered as conceptually
12443 unordered, unless an explicit pragma @code{Ordered} is given for the type.
12444 The effect is to generate warnings in clients that use explicit comparisons
12445 or subranges, since these constructs both treat objects of the type as
12446 ordered. (A @emph{client} is defined as a unit that is other than the unit in
12447 which the type is declared, or its body or subunits.) Please refer to
12448 the description of pragma @code{Ordered} in the
12449 @cite{GNAT Reference Manual} for further details.
12450 The default is that such warnings are not generated.
12453 @geindex -gnatw.U (gcc)
12458 @item @code{-gnatw.U}
12460 @emph{Deactivate warnings on unordered enumeration types.}
12462 This switch causes all enumeration types to be considered as ordered, so
12463 that no warnings are given for comparisons or subranges for any type.
12466 @geindex -gnatwv (gcc)
12468 @geindex Unassigned variable warnings
12473 @item @code{-gnatwv}
12475 @emph{Activate warnings on unassigned variables.}
12477 This switch activates warnings for access to variables which
12478 may not be properly initialized. The default is that
12479 such warnings are generated.
12482 @geindex -gnatwV (gcc)
12487 @item @code{-gnatwV}
12489 @emph{Suppress warnings on unassigned variables.}
12491 This switch suppresses warnings for access to variables which
12492 may not be properly initialized.
12493 For variables of a composite type, the warning can also be suppressed in
12494 Ada 2005 by using a default initialization with a box. For example, if
12495 Table is an array of records whose components are only partially uninitialized,
12496 then the following code:
12499 Tab : Table := (others => <>);
12502 will suppress warnings on subsequent statements that access components
12506 @geindex -gnatw.v (gcc)
12508 @geindex bit order warnings
12513 @item @code{-gnatw.v}
12515 @emph{Activate info messages for non-default bit order.}
12517 This switch activates messages (labeled "info", they are not warnings,
12518 just informational messages) about the effects of non-default bit-order
12519 on records to which a component clause is applied. The effect of specifying
12520 non-default bit ordering is a bit subtle (and changed with Ada 2005), so
12521 these messages, which are given by default, are useful in understanding the
12522 exact consequences of using this feature.
12525 @geindex -gnatw.V (gcc)
12530 @item @code{-gnatw.V}
12532 @emph{Suppress info messages for non-default bit order.}
12534 This switch suppresses information messages for the effects of specifying
12535 non-default bit order on record components with component clauses.
12538 @geindex -gnatww (gcc)
12540 @geindex String indexing warnings
12545 @item @code{-gnatww}
12547 @emph{Activate warnings on wrong low bound assumption.}
12549 This switch activates warnings for indexing an unconstrained string parameter
12550 with a literal or S'Length. This is a case where the code is assuming that the
12551 low bound is one, which is in general not true (for example when a slice is
12552 passed). The default is that such warnings are generated.
12555 @geindex -gnatwW (gcc)
12560 @item @code{-gnatwW}
12562 @emph{Suppress warnings on wrong low bound assumption.}
12564 This switch suppresses warnings for indexing an unconstrained string parameter
12565 with a literal or S'Length. Note that this warning can also be suppressed
12566 in a particular case by adding an assertion that the lower bound is 1,
12567 as shown in the following example:
12570 procedure K (S : String) is
12571 pragma Assert (S'First = 1);
12576 @geindex -gnatw.w (gcc)
12578 @geindex Warnings Off control
12583 @item @code{-gnatw.w}
12585 @emph{Activate warnings on Warnings Off pragmas.}
12587 This switch activates warnings for use of @code{pragma Warnings (Off, entity)}
12588 where either the pragma is entirely useless (because it suppresses no
12589 warnings), or it could be replaced by @code{pragma Unreferenced} or
12590 @code{pragma Unmodified}.
12591 Also activates warnings for the case of
12592 Warnings (Off, String), where either there is no matching
12593 Warnings (On, String), or the Warnings (Off) did not suppress any warning.
12594 The default is that these warnings are not given.
12597 @geindex -gnatw.W (gcc)
12602 @item @code{-gnatw.W}
12604 @emph{Suppress warnings on unnecessary Warnings Off pragmas.}
12606 This switch suppresses warnings for use of @code{pragma Warnings (Off, ...)}.
12609 @geindex -gnatwx (gcc)
12611 @geindex Export/Import pragma warnings
12616 @item @code{-gnatwx}
12618 @emph{Activate warnings on Export/Import pragmas.}
12620 This switch activates warnings on Export/Import pragmas when
12621 the compiler detects a possible conflict between the Ada and
12622 foreign language calling sequences. For example, the use of
12623 default parameters in a convention C procedure is dubious
12624 because the C compiler cannot supply the proper default, so
12625 a warning is issued. The default is that such warnings are
12629 @geindex -gnatwX (gcc)
12634 @item @code{-gnatwX}
12636 @emph{Suppress warnings on Export/Import pragmas.}
12638 This switch suppresses warnings on Export/Import pragmas.
12639 The sense of this is that you are telling the compiler that
12640 you know what you are doing in writing the pragma, and it
12641 should not complain at you.
12644 @geindex -gnatwm (gcc)
12649 @item @code{-gnatw.x}
12651 @emph{Activate warnings for No_Exception_Propagation mode.}
12653 This switch activates warnings for exception usage when pragma Restrictions
12654 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
12655 explicit exception raises which are not covered by a local handler, and for
12656 exception handlers which do not cover a local raise. The default is that
12657 these warnings are given for units that contain exception handlers.
12659 @item @code{-gnatw.X}
12661 @emph{Disable warnings for No_Exception_Propagation mode.}
12663 This switch disables warnings for exception usage when pragma Restrictions
12664 (No_Exception_Propagation) is in effect.
12667 @geindex -gnatwy (gcc)
12669 @geindex Ada compatibility issues warnings
12674 @item @code{-gnatwy}
12676 @emph{Activate warnings for Ada compatibility issues.}
12678 For the most part, newer versions of Ada are upwards compatible
12679 with older versions. For example, Ada 2005 programs will almost
12680 always work when compiled as Ada 2012.
12681 However there are some exceptions (for example the fact that
12682 @code{some} is now a reserved word in Ada 2012). This
12683 switch activates several warnings to help in identifying
12684 and correcting such incompatibilities. The default is that
12685 these warnings are generated. Note that at one point Ada 2005
12686 was called Ada 0Y, hence the choice of character.
12689 @geindex -gnatwY (gcc)
12691 @geindex Ada compatibility issues warnings
12696 @item @code{-gnatwY}
12698 @emph{Disable warnings for Ada compatibility issues.}
12700 This switch suppresses the warnings intended to help in identifying
12701 incompatibilities between Ada language versions.
12704 @geindex -gnatw.y (gcc)
12706 @geindex Package spec needing body
12711 @item @code{-gnatw.y}
12713 @emph{Activate information messages for why package spec needs body.}
12715 There are a number of cases in which a package spec needs a body.
12716 For example, the use of pragma Elaborate_Body, or the declaration
12717 of a procedure specification requiring a completion. This switch
12718 causes information messages to be output showing why a package
12719 specification requires a body. This can be useful in the case of
12720 a large package specification which is unexpectedly requiring a
12721 body. The default is that such information messages are not output.
12724 @geindex -gnatw.Y (gcc)
12726 @geindex No information messages for why package spec needs body
12731 @item @code{-gnatw.Y}
12733 @emph{Disable information messages for why package spec needs body.}
12735 This switch suppresses the output of information messages showing why
12736 a package specification needs a body.
12739 @geindex -gnatwz (gcc)
12741 @geindex Unchecked_Conversion warnings
12746 @item @code{-gnatwz}
12748 @emph{Activate warnings on unchecked conversions.}
12750 This switch activates warnings for unchecked conversions
12751 where the types are known at compile time to have different
12752 sizes. The default is that such warnings are generated. Warnings are also
12753 generated for subprogram pointers with different conventions.
12756 @geindex -gnatwZ (gcc)
12761 @item @code{-gnatwZ}
12763 @emph{Suppress warnings on unchecked conversions.}
12765 This switch suppresses warnings for unchecked conversions
12766 where the types are known at compile time to have different
12767 sizes or conventions.
12770 @geindex -gnatw.z (gcc)
12772 @geindex Size/Alignment warnings
12777 @item @code{-gnatw.z}
12779 @emph{Activate warnings for size not a multiple of alignment.}
12781 This switch activates warnings for cases of array and record types
12782 with specified @code{Size} and @code{Alignment} attributes where the
12783 size is not a multiple of the alignment, resulting in an object
12784 size that is greater than the specified size. The default
12785 is that such warnings are generated.
12788 @geindex -gnatw.Z (gcc)
12790 @geindex Size/Alignment warnings
12795 @item @code{-gnatw.Z}
12797 @emph{Suppress warnings for size not a multiple of alignment.}
12799 This switch suppresses warnings for cases of array and record types
12800 with specified @code{Size} and @code{Alignment} attributes where the
12801 size is not a multiple of the alignment, resulting in an object
12802 size that is greater than the specified size. The warning can also
12803 be suppressed by giving an explicit @code{Object_Size} value.
12806 @geindex -Wunused (gcc)
12811 @item @code{-Wunused}
12813 The warnings controlled by the @code{-gnatw} switch are generated by
12814 the front end of the compiler. The GCC back end can provide
12815 additional warnings and they are controlled by the @code{-W} switch.
12816 For example, @code{-Wunused} activates back end
12817 warnings for entities that are declared but not referenced.
12820 @geindex -Wuninitialized (gcc)
12825 @item @code{-Wuninitialized}
12827 Similarly, @code{-Wuninitialized} activates
12828 the back end warning for uninitialized variables. This switch must be
12829 used in conjunction with an optimization level greater than zero.
12832 @geindex -Wstack-usage (gcc)
12837 @item @code{-Wstack-usage=@emph{len}}
12839 Warn if the stack usage of a subprogram might be larger than @code{len} bytes.
12840 See @ref{f5,,Static Stack Usage Analysis} for details.
12843 @geindex -Wall (gcc)
12850 This switch enables most warnings from the GCC back end.
12851 The code generator detects a number of warning situations that are missed
12852 by the GNAT front end, and this switch can be used to activate them.
12853 The use of this switch also sets the default front end warning mode to
12854 @code{-gnatwa}, that is, most front end warnings activated as well.
12864 Conversely, this switch suppresses warnings from the GCC back end.
12865 The use of this switch also sets the default front end warning mode to
12866 @code{-gnatws}, that is, front end warnings suppressed as well.
12869 @geindex -Werror (gcc)
12874 @item @code{-Werror}
12876 This switch causes warnings from the GCC back end to be treated as
12877 errors. The warning string still appears, but the warning messages are
12878 counted as errors, and prevent the generation of an object file.
12881 A string of warning parameters can be used in the same parameter. For example:
12887 will turn on all optional warnings except for unrecognized pragma warnings,
12888 and also specify that warnings should be treated as errors.
12890 When no switch @code{-gnatw} is used, this is equivalent to:
13037 @node Debugging and Assertion Control,Validity Checking,Warning Message Control,Compiler Switches
13038 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-and-assertion-control}@anchor{100}@anchor{gnat_ugn/building_executable_programs_with_gnat id16}@anchor{101}
13039 @subsection Debugging and Assertion Control
13042 @geindex -gnata (gcc)
13047 @item @code{-gnata}
13053 @geindex Assertions
13055 @geindex Precondition
13057 @geindex Postcondition
13059 @geindex Type invariants
13061 @geindex Subtype predicates
13063 The @code{-gnata} option is equivalent to the following @code{Assertion_Policy} pragma:
13066 pragma Assertion_Policy (Check);
13069 Which is a shorthand for:
13072 pragma Assertion_Policy
13074 Static_Predicate => Check,
13075 Dynamic_Predicate => Check,
13077 Pre'Class => Check,
13079 Post'Class => Check,
13080 Type_Invariant => Check,
13081 Type_Invariant'Class => Check);
13084 The pragmas @code{Assert} and @code{Debug} normally have no effect and
13085 are ignored. This switch, where @code{a} stands for 'assert', causes
13086 pragmas @code{Assert} and @code{Debug} to be activated. This switch also
13087 causes preconditions, postconditions, subtype predicates, and
13088 type invariants to be activated.
13090 The pragmas have the form:
13093 pragma Assert (<Boolean-expression> [, <static-string-expression>])
13094 pragma Debug (<procedure call>)
13095 pragma Type_Invariant (<type-local-name>, <Boolean-expression>)
13096 pragma Predicate (<type-local-name>, <Boolean-expression>)
13097 pragma Precondition (<Boolean-expression>, <string-expression>)
13098 pragma Postcondition (<Boolean-expression>, <string-expression>)
13101 The aspects have the form:
13104 with [Pre|Post|Type_Invariant|Dynamic_Predicate|Static_Predicate]
13105 => <Boolean-expression>;
13108 The @code{Assert} pragma causes @code{Boolean-expression} to be tested.
13109 If the result is @code{True}, the pragma has no effect (other than
13110 possible side effects from evaluating the expression). If the result is
13111 @code{False}, the exception @code{Assert_Failure} declared in the package
13112 @code{System.Assertions} is raised (passing @code{static-string-expression}, if
13113 present, as the message associated with the exception). If no string
13114 expression is given, the default is a string containing the file name and
13115 line number of the pragma.
13117 The @code{Debug} pragma causes @code{procedure} to be called. Note that
13118 @code{pragma Debug} may appear within a declaration sequence, allowing
13119 debugging procedures to be called between declarations.
13121 For the aspect specification, the @code{Boolean-expression} is evaluated.
13122 If the result is @code{True}, the aspect has no effect. If the result
13123 is @code{False}, the exception @code{Assert_Failure} is raised.
13126 @node Validity Checking,Style Checking,Debugging and Assertion Control,Compiler Switches
13127 @anchor{gnat_ugn/building_executable_programs_with_gnat validity-checking}@anchor{f6}@anchor{gnat_ugn/building_executable_programs_with_gnat id17}@anchor{102}
13128 @subsection Validity Checking
13131 @geindex Validity Checking
13133 The Ada Reference Manual defines the concept of invalid values (see
13134 RM 13.9.1). The primary source of invalid values is uninitialized
13135 variables. A scalar variable that is left uninitialized may contain
13136 an invalid value; the concept of invalid does not apply to access or
13139 It is an error to read an invalid value, but the RM does not require
13140 run-time checks to detect such errors, except for some minimal
13141 checking to prevent erroneous execution (i.e. unpredictable
13142 behavior). This corresponds to the @code{-gnatVd} switch below,
13143 which is the default. For example, by default, if the expression of a
13144 case statement is invalid, it will raise Constraint_Error rather than
13145 causing a wild jump, and if an array index on the left-hand side of an
13146 assignment is invalid, it will raise Constraint_Error rather than
13147 overwriting an arbitrary memory location.
13149 The @code{-gnatVa} may be used to enable additional validity checks,
13150 which are not required by the RM. These checks are often very
13151 expensive (which is why the RM does not require them). These checks
13152 are useful in tracking down uninitialized variables, but they are
13153 not usually recommended for production builds, and in particular
13154 we do not recommend using these extra validity checking options in
13155 combination with optimization, since this can confuse the optimizer.
13156 If performance is a consideration, leading to the need to optimize,
13157 then the validity checking options should not be used.
13159 The other @code{-gnatV@emph{x}} switches below allow finer-grained
13160 control; you can enable whichever validity checks you desire. However,
13161 for most debugging purposes, @code{-gnatVa} is sufficient, and the
13162 default @code{-gnatVd} (i.e. standard Ada behavior) is usually
13163 sufficient for non-debugging use.
13165 The @code{-gnatB} switch tells the compiler to assume that all
13166 values are valid (that is, within their declared subtype range)
13167 except in the context of a use of the Valid attribute. This means
13168 the compiler can generate more efficient code, since the range
13169 of values is better known at compile time. However, an uninitialized
13170 variable can cause wild jumps and memory corruption in this mode.
13172 The @code{-gnatV@emph{x}} switch allows control over the validity
13173 checking mode as described below.
13174 The @code{x} argument is a string of letters that
13175 indicate validity checks that are performed or not performed in addition
13176 to the default checks required by Ada as described above.
13178 @geindex -gnatVa (gcc)
13183 @item @code{-gnatVa}
13185 @emph{All validity checks.}
13187 All validity checks are turned on.
13188 That is, @code{-gnatVa} is
13189 equivalent to @code{gnatVcdfimorst}.
13192 @geindex -gnatVc (gcc)
13197 @item @code{-gnatVc}
13199 @emph{Validity checks for copies.}
13201 The right hand side of assignments, and the initializing values of
13202 object declarations are validity checked.
13205 @geindex -gnatVd (gcc)
13210 @item @code{-gnatVd}
13212 @emph{Default (RM) validity checks.}
13214 Some validity checks are done by default following normal Ada semantics
13215 (RM 13.9.1 (9-11)).
13216 A check is done in case statements that the expression is within the range
13217 of the subtype. If it is not, Constraint_Error is raised.
13218 For assignments to array components, a check is done that the expression used
13219 as index is within the range. If it is not, Constraint_Error is raised.
13220 Both these validity checks may be turned off using switch @code{-gnatVD}.
13221 They are turned on by default. If @code{-gnatVD} is specified, a subsequent
13222 switch @code{-gnatVd} will leave the checks turned on.
13223 Switch @code{-gnatVD} should be used only if you are sure that all such
13224 expressions have valid values. If you use this switch and invalid values
13225 are present, then the program is erroneous, and wild jumps or memory
13226 overwriting may occur.
13229 @geindex -gnatVe (gcc)
13234 @item @code{-gnatVe}
13236 @emph{Validity checks for elementary components.}
13238 In the absence of this switch, assignments to record or array components are
13239 not validity checked, even if validity checks for assignments generally
13240 (@code{-gnatVc}) are turned on. In Ada, assignment of composite values do not
13241 require valid data, but assignment of individual components does. So for
13242 example, there is a difference between copying the elements of an array with a
13243 slice assignment, compared to assigning element by element in a loop. This
13244 switch allows you to turn off validity checking for components, even when they
13245 are assigned component by component.
13248 @geindex -gnatVf (gcc)
13253 @item @code{-gnatVf}
13255 @emph{Validity checks for floating-point values.}
13257 In the absence of this switch, validity checking occurs only for discrete
13258 values. If @code{-gnatVf} is specified, then validity checking also applies
13259 for floating-point values, and NaNs and infinities are considered invalid,
13260 as well as out of range values for constrained types. Note that this means
13261 that standard IEEE infinity mode is not allowed. The exact contexts
13262 in which floating-point values are checked depends on the setting of other
13263 options. For example, @code{-gnatVif} or @code{-gnatVfi}
13264 (the order does not matter) specifies that floating-point parameters of mode
13265 @code{in} should be validity checked.
13268 @geindex -gnatVi (gcc)
13273 @item @code{-gnatVi}
13275 @emph{Validity checks for `@w{`}in`@w{`} mode parameters.}
13277 Arguments for parameters of mode @code{in} are validity checked in function
13278 and procedure calls at the point of call.
13281 @geindex -gnatVm (gcc)
13286 @item @code{-gnatVm}
13288 @emph{Validity checks for `@w{`}in out`@w{`} mode parameters.}
13290 Arguments for parameters of mode @code{in out} are validity checked in
13291 procedure calls at the point of call. The @code{'m'} here stands for
13292 modify, since this concerns parameters that can be modified by the call.
13293 Note that there is no specific option to test @code{out} parameters,
13294 but any reference within the subprogram will be tested in the usual
13295 manner, and if an invalid value is copied back, any reference to it
13296 will be subject to validity checking.
13299 @geindex -gnatVn (gcc)
13304 @item @code{-gnatVn}
13306 @emph{No validity checks.}
13308 This switch turns off all validity checking, including the default checking
13309 for case statements and left hand side subscripts. Note that the use of
13310 the switch @code{-gnatp} suppresses all run-time checks, including
13311 validity checks, and thus implies @code{-gnatVn}. When this switch
13312 is used, it cancels any other @code{-gnatV} previously issued.
13315 @geindex -gnatVo (gcc)
13320 @item @code{-gnatVo}
13322 @emph{Validity checks for operator and attribute operands.}
13324 Arguments for predefined operators and attributes are validity checked.
13325 This includes all operators in package @code{Standard},
13326 the shift operators defined as intrinsic in package @code{Interfaces}
13327 and operands for attributes such as @code{Pos}. Checks are also made
13328 on individual component values for composite comparisons, and on the
13329 expressions in type conversions and qualified expressions. Checks are
13330 also made on explicit ranges using @code{..} (e.g., slices, loops etc).
13333 @geindex -gnatVp (gcc)
13338 @item @code{-gnatVp}
13340 @emph{Validity checks for parameters.}
13342 This controls the treatment of parameters within a subprogram (as opposed
13343 to @code{-gnatVi} and @code{-gnatVm} which control validity testing
13344 of parameters on a call. If either of these call options is used, then
13345 normally an assumption is made within a subprogram that the input arguments
13346 have been validity checking at the point of call, and do not need checking
13347 again within a subprogram). If @code{-gnatVp} is set, then this assumption
13348 is not made, and parameters are not assumed to be valid, so their validity
13349 will be checked (or rechecked) within the subprogram.
13352 @geindex -gnatVr (gcc)
13357 @item @code{-gnatVr}
13359 @emph{Validity checks for function returns.}
13361 The expression in @code{return} statements in functions is validity
13365 @geindex -gnatVs (gcc)
13370 @item @code{-gnatVs}
13372 @emph{Validity checks for subscripts.}
13374 All subscripts expressions are checked for validity, whether they appear
13375 on the right side or left side (in default mode only left side subscripts
13376 are validity checked).
13379 @geindex -gnatVt (gcc)
13384 @item @code{-gnatVt}
13386 @emph{Validity checks for tests.}
13388 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
13389 statements are checked, as well as guard expressions in entry calls.
13392 The @code{-gnatV} switch may be followed by a string of letters
13393 to turn on a series of validity checking options.
13394 For example, @code{-gnatVcr}
13395 specifies that in addition to the default validity checking, copies and
13396 function return expressions are to be validity checked.
13397 In order to make it easier to specify the desired combination of effects,
13398 the upper case letters @code{CDFIMORST} may
13399 be used to turn off the corresponding lower case option.
13400 Thus @code{-gnatVaM} turns on all validity checking options except for
13401 checking of @code{in out} parameters.
13403 The specification of additional validity checking generates extra code (and
13404 in the case of @code{-gnatVa} the code expansion can be substantial).
13405 However, these additional checks can be very useful in detecting
13406 uninitialized variables, incorrect use of unchecked conversion, and other
13407 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
13408 is useful in conjunction with the extra validity checking, since this
13409 ensures that wherever possible uninitialized variables have invalid values.
13411 See also the pragma @code{Validity_Checks} which allows modification of
13412 the validity checking mode at the program source level, and also allows for
13413 temporary disabling of validity checks.
13415 @node Style Checking,Run-Time Checks,Validity Checking,Compiler Switches
13416 @anchor{gnat_ugn/building_executable_programs_with_gnat id18}@anchor{103}@anchor{gnat_ugn/building_executable_programs_with_gnat style-checking}@anchor{fb}
13417 @subsection Style Checking
13420 @geindex Style checking
13422 @geindex -gnaty (gcc)
13424 The @code{-gnatyx} switch causes the compiler to
13425 enforce specified style rules. A limited set of style rules has been used
13426 in writing the GNAT sources themselves. This switch allows user programs
13427 to activate all or some of these checks. If the source program fails a
13428 specified style check, an appropriate message is given, preceded by
13429 the character sequence '(style)'. This message does not prevent
13430 successful compilation (unless the @code{-gnatwe} switch is used).
13432 Note that this is by no means intended to be a general facility for
13433 checking arbitrary coding standards. It is simply an embedding of the
13434 style rules we have chosen for the GNAT sources. If you are starting
13435 a project which does not have established style standards, you may
13436 find it useful to adopt the entire set of GNAT coding standards, or
13437 some subset of them.
13440 The string @code{x} is a sequence of letters or digits
13441 indicating the particular style
13442 checks to be performed. The following checks are defined:
13444 @geindex -gnaty[0-9] (gcc)
13449 @item @code{-gnaty0}
13451 @emph{Specify indentation level.}
13453 If a digit from 1-9 appears
13454 in the string after @code{-gnaty}
13455 then proper indentation is checked, with the digit indicating the
13456 indentation level required. A value of zero turns off this style check.
13457 The general style of required indentation is as specified by
13458 the examples in the Ada Reference Manual. Full line comments must be
13459 aligned with the @code{--} starting on a column that is a multiple of
13460 the alignment level, or they may be aligned the same way as the following
13461 non-blank line (this is useful when full line comments appear in the middle
13462 of a statement, or they may be aligned with the source line on the previous
13466 @geindex -gnatya (gcc)
13471 @item @code{-gnatya}
13473 @emph{Check attribute casing.}
13475 Attribute names, including the case of keywords such as @code{digits}
13476 used as attributes names, must be written in mixed case, that is, the
13477 initial letter and any letter following an underscore must be uppercase.
13478 All other letters must be lowercase.
13481 @geindex -gnatyA (gcc)
13486 @item @code{-gnatyA}
13488 @emph{Use of array index numbers in array attributes.}
13490 When using the array attributes First, Last, Range,
13491 or Length, the index number must be omitted for one-dimensional arrays
13492 and is required for multi-dimensional arrays.
13495 @geindex -gnatyb (gcc)
13500 @item @code{-gnatyb}
13502 @emph{Blanks not allowed at statement end.}
13504 Trailing blanks are not allowed at the end of statements. The purpose of this
13505 rule, together with h (no horizontal tabs), is to enforce a canonical format
13506 for the use of blanks to separate source tokens.
13509 @geindex -gnatyB (gcc)
13514 @item @code{-gnatyB}
13516 @emph{Check Boolean operators.}
13518 The use of AND/OR operators is not permitted except in the cases of modular
13519 operands, array operands, and simple stand-alone boolean variables or
13520 boolean constants. In all other cases @code{and then}/@cite{or else} are
13524 @geindex -gnatyc (gcc)
13529 @item @code{-gnatyc}
13531 @emph{Check comments, double space.}
13533 Comments must meet the following set of rules:
13539 The @code{--} that starts the column must either start in column one,
13540 or else at least one blank must precede this sequence.
13543 Comments that follow other tokens on a line must have at least one blank
13544 following the @code{--} at the start of the comment.
13547 Full line comments must have at least two blanks following the
13548 @code{--} that starts the comment, with the following exceptions.
13551 A line consisting only of the @code{--} characters, possibly preceded
13552 by blanks is permitted.
13555 A comment starting with @code{--x} where @code{x} is a special character
13557 This allows proper processing of the output from specialized tools
13558 such as @code{gnatprep} (where @code{--!} is used) and in earlier versions of the SPARK
13560 language (where @code{--#} is used). For the purposes of this rule, a
13561 special character is defined as being in one of the ASCII ranges
13562 @code{16#21#...16#2F#} or @code{16#3A#...16#3F#}.
13563 Note that this usage is not permitted
13564 in GNAT implementation units (i.e., when @code{-gnatg} is used).
13567 A line consisting entirely of minus signs, possibly preceded by blanks, is
13568 permitted. This allows the construction of box comments where lines of minus
13569 signs are used to form the top and bottom of the box.
13572 A comment that starts and ends with @code{--} is permitted as long as at
13573 least one blank follows the initial @code{--}. Together with the preceding
13574 rule, this allows the construction of box comments, as shown in the following
13578 ---------------------------
13579 -- This is a box comment --
13580 -- with two text lines. --
13581 ---------------------------
13586 @geindex -gnatyC (gcc)
13591 @item @code{-gnatyC}
13593 @emph{Check comments, single space.}
13595 This is identical to @code{c} except that only one space
13596 is required following the @code{--} of a comment instead of two.
13599 @geindex -gnatyd (gcc)
13604 @item @code{-gnatyd}
13606 @emph{Check no DOS line terminators present.}
13608 All lines must be terminated by a single ASCII.LF
13609 character (in particular the DOS line terminator sequence CR/LF is not
13613 @geindex -gnatyD (gcc)
13618 @item @code{-gnatyD}
13620 @emph{Check declared identifiers in mixed case.}
13622 Declared identifiers must be in mixed case, as in
13623 This_Is_An_Identifier. Use -gnatyr in addition to ensure
13624 that references match declarations.
13627 @geindex -gnatye (gcc)
13632 @item @code{-gnatye}
13634 @emph{Check end/exit labels.}
13636 Optional labels on @code{end} statements ending subprograms and on
13637 @code{exit} statements exiting named loops, are required to be present.
13640 @geindex -gnatyf (gcc)
13645 @item @code{-gnatyf}
13647 @emph{No form feeds or vertical tabs.}
13649 Neither form feeds nor vertical tab characters are permitted
13650 in the source text.
13653 @geindex -gnatyg (gcc)
13658 @item @code{-gnatyg}
13660 @emph{GNAT style mode.}
13662 The set of style check switches is set to match that used by the GNAT sources.
13663 This may be useful when developing code that is eventually intended to be
13664 incorporated into GNAT. Currently this is equivalent to @code{-gnatyydISux})
13665 but additional style switches may be added to this set in the future without
13669 @geindex -gnatyh (gcc)
13674 @item @code{-gnatyh}
13676 @emph{No horizontal tabs.}
13678 Horizontal tab characters are not permitted in the source text.
13679 Together with the b (no blanks at end of line) check, this
13680 enforces a canonical form for the use of blanks to separate
13684 @geindex -gnatyi (gcc)
13689 @item @code{-gnatyi}
13691 @emph{Check if-then layout.}
13693 The keyword @code{then} must appear either on the same
13694 line as corresponding @code{if}, or on a line on its own, lined
13695 up under the @code{if}.
13698 @geindex -gnatyI (gcc)
13703 @item @code{-gnatyI}
13705 @emph{check mode IN keywords.}
13707 Mode @code{in} (the default mode) is not
13708 allowed to be given explicitly. @code{in out} is fine,
13709 but not @code{in} on its own.
13712 @geindex -gnatyk (gcc)
13717 @item @code{-gnatyk}
13719 @emph{Check keyword casing.}
13721 All keywords must be in lower case (with the exception of keywords
13722 such as @code{digits} used as attribute names to which this check
13726 @geindex -gnatyl (gcc)
13731 @item @code{-gnatyl}
13733 @emph{Check layout.}
13735 Layout of statement and declaration constructs must follow the
13736 recommendations in the Ada Reference Manual, as indicated by the
13737 form of the syntax rules. For example an @code{else} keyword must
13738 be lined up with the corresponding @code{if} keyword.
13740 There are two respects in which the style rule enforced by this check
13741 option are more liberal than those in the Ada Reference Manual. First
13742 in the case of record declarations, it is permissible to put the
13743 @code{record} keyword on the same line as the @code{type} keyword, and
13744 then the @code{end} in @code{end record} must line up under @code{type}.
13745 This is also permitted when the type declaration is split on two lines.
13746 For example, any of the following three layouts is acceptable:
13767 Second, in the case of a block statement, a permitted alternative
13768 is to put the block label on the same line as the @code{declare} or
13769 @code{begin} keyword, and then line the @code{end} keyword up under
13770 the block label. For example both the following are permitted:
13787 The same alternative format is allowed for loops. For example, both of
13788 the following are permitted:
13791 Clear : while J < 10 loop
13802 @geindex -gnatyLnnn (gcc)
13807 @item @code{-gnatyL}
13809 @emph{Set maximum nesting level.}
13811 The maximum level of nesting of constructs (including subprograms, loops,
13812 blocks, packages, and conditionals) may not exceed the given value
13813 @emph{nnn}. A value of zero disconnects this style check.
13816 @geindex -gnatym (gcc)
13821 @item @code{-gnatym}
13823 @emph{Check maximum line length.}
13825 The length of source lines must not exceed 79 characters, including
13826 any trailing blanks. The value of 79 allows convenient display on an
13827 80 character wide device or window, allowing for possible special
13828 treatment of 80 character lines. Note that this count is of
13829 characters in the source text. This means that a tab character counts
13830 as one character in this count and a wide character sequence counts as
13831 a single character (however many bytes are needed in the encoding).
13834 @geindex -gnatyMnnn (gcc)
13839 @item @code{-gnatyM}
13841 @emph{Set maximum line length.}
13843 The length of lines must not exceed the
13844 given value @emph{nnn}. The maximum value that can be specified is 32767.
13845 If neither style option for setting the line length is used, then the
13846 default is 255. This also controls the maximum length of lexical elements,
13847 where the only restriction is that they must fit on a single line.
13850 @geindex -gnatyn (gcc)
13855 @item @code{-gnatyn}
13857 @emph{Check casing of entities in Standard.}
13859 Any identifier from Standard must be cased
13860 to match the presentation in the Ada Reference Manual (for example,
13861 @code{Integer} and @code{ASCII.NUL}).
13864 @geindex -gnatyN (gcc)
13869 @item @code{-gnatyN}
13871 @emph{Turn off all style checks.}
13873 All style check options are turned off.
13876 @geindex -gnatyo (gcc)
13881 @item @code{-gnatyo}
13883 @emph{Check order of subprogram bodies.}
13885 All subprogram bodies in a given scope
13886 (e.g., a package body) must be in alphabetical order. The ordering
13887 rule uses normal Ada rules for comparing strings, ignoring casing
13888 of letters, except that if there is a trailing numeric suffix, then
13889 the value of this suffix is used in the ordering (e.g., Junk2 comes
13893 @geindex -gnatyO (gcc)
13898 @item @code{-gnatyO}
13900 @emph{Check that overriding subprograms are explicitly marked as such.}
13902 This applies to all subprograms of a derived type that override a primitive
13903 operation of the type, for both tagged and untagged types. In particular,
13904 the declaration of a primitive operation of a type extension that overrides
13905 an inherited operation must carry an overriding indicator. Another case is
13906 the declaration of a function that overrides a predefined operator (such
13907 as an equality operator).
13910 @geindex -gnatyp (gcc)
13915 @item @code{-gnatyp}
13917 @emph{Check pragma casing.}
13919 Pragma names must be written in mixed case, that is, the
13920 initial letter and any letter following an underscore must be uppercase.
13921 All other letters must be lowercase. An exception is that SPARK_Mode is
13922 allowed as an alternative for Spark_Mode.
13925 @geindex -gnatyr (gcc)
13930 @item @code{-gnatyr}
13932 @emph{Check references.}
13934 All identifier references must be cased in the same way as the
13935 corresponding declaration. No specific casing style is imposed on
13936 identifiers. The only requirement is for consistency of references
13940 @geindex -gnatys (gcc)
13945 @item @code{-gnatys}
13947 @emph{Check separate specs.}
13949 Separate declarations ('specs') are required for subprograms (a
13950 body is not allowed to serve as its own declaration). The only
13951 exception is that parameterless library level procedures are
13952 not required to have a separate declaration. This exception covers
13953 the most frequent form of main program procedures.
13956 @geindex -gnatyS (gcc)
13961 @item @code{-gnatyS}
13963 @emph{Check no statements after then/else.}
13965 No statements are allowed
13966 on the same line as a @code{then} or @code{else} keyword following the
13967 keyword in an @code{if} statement. @code{or else} and @code{and then} are not
13968 affected, and a special exception allows a pragma to appear after @code{else}.
13971 @geindex -gnatyt (gcc)
13976 @item @code{-gnatyt}
13978 @emph{Check token spacing.}
13980 The following token spacing rules are enforced:
13986 The keywords @code{abs} and @code{not} must be followed by a space.
13989 The token @code{=>} must be surrounded by spaces.
13992 The token @code{<>} must be preceded by a space or a left parenthesis.
13995 Binary operators other than @code{**} must be surrounded by spaces.
13996 There is no restriction on the layout of the @code{**} binary operator.
13999 Colon must be surrounded by spaces.
14002 Colon-equal (assignment, initialization) must be surrounded by spaces.
14005 Comma must be the first non-blank character on the line, or be
14006 immediately preceded by a non-blank character, and must be followed
14010 If the token preceding a left parenthesis ends with a letter or digit, then
14011 a space must separate the two tokens.
14014 If the token following a right parenthesis starts with a letter or digit, then
14015 a space must separate the two tokens.
14018 A right parenthesis must either be the first non-blank character on
14019 a line, or it must be preceded by a non-blank character.
14022 A semicolon must not be preceded by a space, and must not be followed by
14023 a non-blank character.
14026 A unary plus or minus may not be followed by a space.
14029 A vertical bar must be surrounded by spaces.
14032 Exactly one blank (and no other white space) must appear between
14033 a @code{not} token and a following @code{in} token.
14036 @geindex -gnatyu (gcc)
14041 @item @code{-gnatyu}
14043 @emph{Check unnecessary blank lines.}
14045 Unnecessary blank lines are not allowed. A blank line is considered
14046 unnecessary if it appears at the end of the file, or if more than
14047 one blank line occurs in sequence.
14050 @geindex -gnatyx (gcc)
14055 @item @code{-gnatyx}
14057 @emph{Check extra parentheses.}
14059 Unnecessary extra level of parentheses (C-style) are not allowed
14060 around conditions in @code{if} statements, @code{while} statements and
14061 @code{exit} statements.
14064 @geindex -gnatyy (gcc)
14069 @item @code{-gnatyy}
14071 @emph{Set all standard style check options.}
14073 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
14074 options enabled with the exception of @code{-gnatyB}, @code{-gnatyd},
14075 @code{-gnatyI}, @code{-gnatyLnnn}, @code{-gnatyo}, @code{-gnatyO},
14076 @code{-gnatyS}, @code{-gnatyu}, and @code{-gnatyx}.
14079 @geindex -gnaty- (gcc)
14084 @item @code{-gnaty-}
14086 @emph{Remove style check options.}
14088 This causes any subsequent options in the string to act as canceling the
14089 corresponding style check option. To cancel maximum nesting level control,
14090 use the @code{L} parameter without any integer value after that, because any
14091 digit following @emph{-} in the parameter string of the @code{-gnaty}
14092 option will be treated as canceling the indentation check. The same is true
14093 for the @code{M} parameter. @code{y} and @code{N} parameters are not
14094 allowed after @emph{-}.
14097 @geindex -gnaty+ (gcc)
14102 @item @code{-gnaty+}
14104 @emph{Enable style check options.}
14106 This causes any subsequent options in the string to enable the corresponding
14107 style check option. That is, it cancels the effect of a previous -,
14111 @c end of switch description (leave this comment to ease automatic parsing for
14115 In the above rules, appearing in column one is always permitted, that is,
14116 counts as meeting either a requirement for a required preceding space,
14117 or as meeting a requirement for no preceding space.
14119 Appearing at the end of a line is also always permitted, that is, counts
14120 as meeting either a requirement for a following space, or as meeting
14121 a requirement for no following space.
14123 If any of these style rules is violated, a message is generated giving
14124 details on the violation. The initial characters of such messages are
14125 always '@cite{(style)}'. Note that these messages are treated as warning
14126 messages, so they normally do not prevent the generation of an object
14127 file. The @code{-gnatwe} switch can be used to treat warning messages,
14128 including style messages, as fatal errors.
14130 The switch @code{-gnaty} on its own (that is not
14131 followed by any letters or digits) is equivalent
14132 to the use of @code{-gnatyy} as described above, that is all
14133 built-in standard style check options are enabled.
14135 The switch @code{-gnatyN} clears any previously set style checks.
14137 @node Run-Time Checks,Using gcc for Syntax Checking,Style Checking,Compiler Switches
14138 @anchor{gnat_ugn/building_executable_programs_with_gnat run-time-checks}@anchor{f9}@anchor{gnat_ugn/building_executable_programs_with_gnat id19}@anchor{104}
14139 @subsection Run-Time Checks
14142 @geindex Division by zero
14144 @geindex Access before elaboration
14147 @geindex division by zero
14150 @geindex access before elaboration
14153 @geindex stack overflow checking
14155 By default, the following checks are suppressed: stack overflow
14156 checks, and checks for access before elaboration on subprogram
14157 calls. All other checks, including overflow checks, range checks and
14158 array bounds checks, are turned on by default. The following @code{gcc}
14159 switches refine this default behavior.
14161 @geindex -gnatp (gcc)
14166 @item @code{-gnatp}
14168 @geindex Suppressing checks
14171 @geindex suppressing
14173 This switch causes the unit to be compiled
14174 as though @code{pragma Suppress (All_checks)}
14175 had been present in the source. Validity checks are also eliminated (in
14176 other words @code{-gnatp} also implies @code{-gnatVn}.
14177 Use this switch to improve the performance
14178 of the code at the expense of safety in the presence of invalid data or
14181 Note that when checks are suppressed, the compiler is allowed, but not
14182 required, to omit the checking code. If the run-time cost of the
14183 checking code is zero or near-zero, the compiler will generate it even
14184 if checks are suppressed. In particular, if the compiler can prove
14185 that a certain check will necessarily fail, it will generate code to
14186 do an unconditional 'raise', even if checks are suppressed. The
14187 compiler warns in this case. Another case in which checks may not be
14188 eliminated is when they are embedded in certain run-time routines such
14189 as math library routines.
14191 Of course, run-time checks are omitted whenever the compiler can prove
14192 that they will not fail, whether or not checks are suppressed.
14194 Note that if you suppress a check that would have failed, program
14195 execution is erroneous, which means the behavior is totally
14196 unpredictable. The program might crash, or print wrong answers, or
14197 do anything else. It might even do exactly what you wanted it to do
14198 (and then it might start failing mysteriously next week or next
14199 year). The compiler will generate code based on the assumption that
14200 the condition being checked is true, which can result in erroneous
14201 execution if that assumption is wrong.
14203 The checks subject to suppression include all the checks defined by the Ada
14204 standard, the additional implementation defined checks @code{Alignment_Check},
14205 @code{Duplicated_Tag_Check}, @code{Predicate_Check}, @code{Container_Checks}, @code{Tampering_Check},
14206 and @code{Validity_Check}, as well as any checks introduced using @code{pragma Check_Name}.
14207 Note that @code{Atomic_Synchronization} is not automatically suppressed by use of this option.
14209 If the code depends on certain checks being active, you can use
14210 pragma @code{Unsuppress} either as a configuration pragma or as
14211 a local pragma to make sure that a specified check is performed
14212 even if @code{gnatp} is specified.
14214 The @code{-gnatp} switch has no effect if a subsequent
14215 @code{-gnat-p} switch appears.
14218 @geindex -gnat-p (gcc)
14220 @geindex Suppressing checks
14223 @geindex suppressing
14230 @item @code{-gnat-p}
14232 This switch cancels the effect of a previous @code{gnatp} switch.
14235 @geindex -gnato?? (gcc)
14237 @geindex Overflow checks
14239 @geindex Overflow mode
14247 @item @code{-gnato??}
14249 This switch controls the mode used for computing intermediate
14250 arithmetic integer operations, and also enables overflow checking.
14251 For a full description of overflow mode and checking control, see
14252 the 'Overflow Check Handling in GNAT' appendix in this
14255 Overflow checks are always enabled by this switch. The argument
14256 controls the mode, using the codes
14261 @item @emph{1 = STRICT}
14263 In STRICT mode, intermediate operations are always done using the
14264 base type, and overflow checking ensures that the result is within
14265 the base type range.
14267 @item @emph{2 = MINIMIZED}
14269 In MINIMIZED mode, overflows in intermediate operations are avoided
14270 where possible by using a larger integer type for the computation
14271 (typically @code{Long_Long_Integer}). Overflow checking ensures that
14272 the result fits in this larger integer type.
14274 @item @emph{3 = ELIMINATED}
14276 In ELIMINATED mode, overflows in intermediate operations are avoided
14277 by using multi-precision arithmetic. In this case, overflow checking
14278 has no effect on intermediate operations (since overflow is impossible).
14281 If two digits are present after @code{-gnato} then the first digit
14282 sets the mode for expressions outside assertions, and the second digit
14283 sets the mode for expressions within assertions. Here assertions is used
14284 in the technical sense (which includes for example precondition and
14285 postcondition expressions).
14287 If one digit is present, the corresponding mode is applicable to both
14288 expressions within and outside assertion expressions.
14290 If no digits are present, the default is to enable overflow checks
14291 and set STRICT mode for both kinds of expressions. This is compatible
14292 with the use of @code{-gnato} in previous versions of GNAT.
14294 @geindex Machine_Overflows
14296 Note that the @code{-gnato??} switch does not affect the code generated
14297 for any floating-point operations; it applies only to integer semantics.
14298 For floating-point, GNAT has the @code{Machine_Overflows}
14299 attribute set to @code{False} and the normal mode of operation is to
14300 generate IEEE NaN and infinite values on overflow or invalid operations
14301 (such as dividing 0.0 by 0.0).
14303 The reason that we distinguish overflow checking from other kinds of
14304 range constraint checking is that a failure of an overflow check, unlike
14305 for example the failure of a range check, can result in an incorrect
14306 value, but cannot cause random memory destruction (like an out of range
14307 subscript), or a wild jump (from an out of range case value). Overflow
14308 checking is also quite expensive in time and space, since in general it
14309 requires the use of double length arithmetic.
14311 Note again that the default is @code{-gnato11} (equivalent to @code{-gnato1}),
14312 so overflow checking is performed in STRICT mode by default.
14315 @geindex -gnatE (gcc)
14317 @geindex Elaboration checks
14320 @geindex elaboration
14325 @item @code{-gnatE}
14327 Enables dynamic checks for access-before-elaboration
14328 on subprogram calls and generic instantiations.
14329 Note that @code{-gnatE} is not necessary for safety, because in the
14330 default mode, GNAT ensures statically that the checks would not fail.
14331 For full details of the effect and use of this switch,
14332 @ref{1c,,Compiling with gcc}.
14335 @geindex -fstack-check (gcc)
14337 @geindex Stack Overflow Checking
14340 @geindex stack overflow checking
14345 @item @code{-fstack-check}
14347 Activates stack overflow checking. For full details of the effect and use of
14348 this switch see @ref{f4,,Stack Overflow Checking}.
14351 @geindex Unsuppress
14353 The setting of these switches only controls the default setting of the
14354 checks. You may modify them using either @code{Suppress} (to remove
14355 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
14356 the program source.
14358 @node Using gcc for Syntax Checking,Using gcc for Semantic Checking,Run-Time Checks,Compiler Switches
14359 @anchor{gnat_ugn/building_executable_programs_with_gnat id20}@anchor{105}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-syntax-checking}@anchor{106}
14360 @subsection Using @code{gcc} for Syntax Checking
14363 @geindex -gnats (gcc)
14368 @item @code{-gnats}
14370 The @code{s} stands for 'syntax'.
14372 Run GNAT in syntax checking only mode. For
14373 example, the command
14376 $ gcc -c -gnats x.adb
14379 compiles file @code{x.adb} in syntax-check-only mode. You can check a
14380 series of files in a single command
14381 , and can use wildcards to specify such a group of files.
14382 Note that you must specify the @code{-c} (compile
14383 only) flag in addition to the @code{-gnats} flag.
14385 You may use other switches in conjunction with @code{-gnats}. In
14386 particular, @code{-gnatl} and @code{-gnatv} are useful to control the
14387 format of any generated error messages.
14389 When the source file is empty or contains only empty lines and/or comments,
14390 the output is a warning:
14393 $ gcc -c -gnats -x ada toto.txt
14394 toto.txt:1:01: warning: empty file, contains no compilation units
14398 Otherwise, the output is simply the error messages, if any. No object file or
14399 ALI file is generated by a syntax-only compilation. Also, no units other
14400 than the one specified are accessed. For example, if a unit @code{X}
14401 @emph{with}s a unit @code{Y}, compiling unit @code{X} in syntax
14402 check only mode does not access the source file containing unit
14405 @geindex Multiple units
14406 @geindex syntax checking
14408 Normally, GNAT allows only a single unit in a source file. However, this
14409 restriction does not apply in syntax-check-only mode, and it is possible
14410 to check a file containing multiple compilation units concatenated
14411 together. This is primarily used by the @code{gnatchop} utility
14412 (@ref{36,,Renaming Files with gnatchop}).
14415 @node Using gcc for Semantic Checking,Compiling Different Versions of Ada,Using gcc for Syntax Checking,Compiler Switches
14416 @anchor{gnat_ugn/building_executable_programs_with_gnat id21}@anchor{107}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-semantic-checking}@anchor{108}
14417 @subsection Using @code{gcc} for Semantic Checking
14420 @geindex -gnatc (gcc)
14425 @item @code{-gnatc}
14427 The @code{c} stands for 'check'.
14428 Causes the compiler to operate in semantic check mode,
14429 with full checking for all illegalities specified in the
14430 Ada Reference Manual, but without generation of any object code
14431 (no object file is generated).
14433 Because dependent files must be accessed, you must follow the GNAT
14434 semantic restrictions on file structuring to operate in this mode:
14440 The needed source files must be accessible
14441 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
14444 Each file must contain only one compilation unit.
14447 The file name and unit name must match (@ref{52,,File Naming Rules}).
14450 The output consists of error messages as appropriate. No object file is
14451 generated. An @code{ALI} file is generated for use in the context of
14452 cross-reference tools, but this file is marked as not being suitable
14453 for binding (since no object file is generated).
14454 The checking corresponds exactly to the notion of
14455 legality in the Ada Reference Manual.
14457 Any unit can be compiled in semantics-checking-only mode, including
14458 units that would not normally be compiled (subunits,
14459 and specifications where a separate body is present).
14462 @node Compiling Different Versions of Ada,Character Set Control,Using gcc for Semantic Checking,Compiler Switches
14463 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-different-versions-of-ada}@anchor{6}@anchor{gnat_ugn/building_executable_programs_with_gnat id22}@anchor{109}
14464 @subsection Compiling Different Versions of Ada
14467 The switches described in this section allow you to explicitly specify
14468 the version of the Ada language that your programs are written in.
14469 The default mode is Ada 2012,
14470 but you can also specify Ada 95, Ada 2005 mode, or
14471 indicate Ada 83 compatibility mode.
14473 @geindex Compatibility with Ada 83
14475 @geindex -gnat83 (gcc)
14478 @geindex Ada 83 tests
14480 @geindex Ada 83 mode
14485 @item @code{-gnat83} (Ada 83 Compatibility Mode)
14487 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
14488 specifies that the program is to be compiled in Ada 83 mode. With
14489 @code{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
14490 semantics where this can be done easily.
14491 It is not possible to guarantee this switch does a perfect
14492 job; some subtle tests, such as are
14493 found in earlier ACVC tests (and that have been removed from the ACATS suite
14494 for Ada 95), might not compile correctly.
14495 Nevertheless, this switch may be useful in some circumstances, for example
14496 where, due to contractual reasons, existing code needs to be maintained
14497 using only Ada 83 features.
14499 With few exceptions (most notably the need to use @code{<>} on
14501 @geindex Generic formal parameters
14502 generic formal parameters,
14503 the use of the new Ada 95 / Ada 2005
14504 reserved words, and the use of packages
14505 with optional bodies), it is not necessary to specify the
14506 @code{-gnat83} switch when compiling Ada 83 programs, because, with rare
14507 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
14508 a correct Ada 83 program is usually also a correct program
14509 in these later versions of the language standard. For further information
14510 please refer to the @emph{Compatibility and Porting Guide} chapter in the
14511 @cite{GNAT Reference Manual}.
14514 @geindex -gnat95 (gcc)
14516 @geindex Ada 95 mode
14521 @item @code{-gnat95} (Ada 95 mode)
14523 This switch directs the compiler to implement the Ada 95 version of the
14525 Since Ada 95 is almost completely upwards
14526 compatible with Ada 83, Ada 83 programs may generally be compiled using
14527 this switch (see the description of the @code{-gnat83} switch for further
14528 information about Ada 83 mode).
14529 If an Ada 2005 program is compiled in Ada 95 mode,
14530 uses of the new Ada 2005 features will cause error
14531 messages or warnings.
14533 This switch also can be used to cancel the effect of a previous
14534 @code{-gnat83}, @code{-gnat05/2005}, or @code{-gnat12/2012}
14535 switch earlier in the command line.
14538 @geindex -gnat05 (gcc)
14540 @geindex -gnat2005 (gcc)
14542 @geindex Ada 2005 mode
14547 @item @code{-gnat05} or @code{-gnat2005} (Ada 2005 mode)
14549 This switch directs the compiler to implement the Ada 2005 version of the
14550 language, as documented in the official Ada standards document.
14551 Since Ada 2005 is almost completely upwards
14552 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
14553 may generally be compiled using this switch (see the description of the
14554 @code{-gnat83} and @code{-gnat95} switches for further
14558 @geindex -gnat12 (gcc)
14560 @geindex -gnat2012 (gcc)
14562 @geindex Ada 2012 mode
14567 @item @code{-gnat12} or @code{-gnat2012} (Ada 2012 mode)
14569 This switch directs the compiler to implement the Ada 2012 version of the
14570 language (also the default).
14571 Since Ada 2012 is almost completely upwards
14572 compatible with Ada 2005 (and thus also with Ada 83, and Ada 95),
14573 Ada 83 and Ada 95 programs
14574 may generally be compiled using this switch (see the description of the
14575 @code{-gnat83}, @code{-gnat95}, and @code{-gnat05/2005} switches
14576 for further information).
14579 @geindex -gnatX (gcc)
14581 @geindex Ada language extensions
14583 @geindex GNAT extensions
14588 @item @code{-gnatX} (Enable GNAT Extensions)
14590 This switch directs the compiler to implement the latest version of the
14591 language (currently Ada 2012) and also to enable certain GNAT implementation
14592 extensions that are not part of any Ada standard. For a full list of these
14593 extensions, see the GNAT reference manual.
14596 @node Character Set Control,File Naming Control,Compiling Different Versions of Ada,Compiler Switches
14597 @anchor{gnat_ugn/building_executable_programs_with_gnat id23}@anchor{10a}@anchor{gnat_ugn/building_executable_programs_with_gnat character-set-control}@anchor{48}
14598 @subsection Character Set Control
14601 @geindex -gnati (gcc)
14606 @item @code{-gnati@emph{c}}
14608 Normally GNAT recognizes the Latin-1 character set in source program
14609 identifiers, as described in the Ada Reference Manual.
14611 GNAT to recognize alternate character sets in identifiers. @code{c} is a
14612 single character indicating the character set, as follows:
14615 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14622 ISO 8859-1 (Latin-1) identifiers
14630 ISO 8859-2 (Latin-2) letters allowed in identifiers
14638 ISO 8859-3 (Latin-3) letters allowed in identifiers
14646 ISO 8859-4 (Latin-4) letters allowed in identifiers
14654 ISO 8859-5 (Cyrillic) letters allowed in identifiers
14662 ISO 8859-15 (Latin-9) letters allowed in identifiers
14670 IBM PC letters (code page 437) allowed in identifiers
14678 IBM PC letters (code page 850) allowed in identifiers
14686 Full upper-half codes allowed in identifiers
14694 No upper-half codes allowed in identifiers
14702 Wide-character codes (that is, codes greater than 255)
14703 allowed in identifiers
14708 See @ref{3e,,Foreign Language Representation} for full details on the
14709 implementation of these character sets.
14712 @geindex -gnatW (gcc)
14717 @item @code{-gnatW@emph{e}}
14719 Specify the method of encoding for wide characters.
14720 @code{e} is one of the following:
14723 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14730 Hex encoding (brackets coding also recognized)
14738 Upper half encoding (brackets encoding also recognized)
14746 Shift/JIS encoding (brackets encoding also recognized)
14754 EUC encoding (brackets encoding also recognized)
14762 UTF-8 encoding (brackets encoding also recognized)
14770 Brackets encoding only (default value)
14775 For full details on these encoding
14776 methods see @ref{4e,,Wide_Character Encodings}.
14777 Note that brackets coding is always accepted, even if one of the other
14778 options is specified, so for example @code{-gnatW8} specifies that both
14779 brackets and UTF-8 encodings will be recognized. The units that are
14780 with'ed directly or indirectly will be scanned using the specified
14781 representation scheme, and so if one of the non-brackets scheme is
14782 used, it must be used consistently throughout the program. However,
14783 since brackets encoding is always recognized, it may be conveniently
14784 used in standard libraries, allowing these libraries to be used with
14785 any of the available coding schemes.
14787 Note that brackets encoding only applies to program text. Within comments,
14788 brackets are considered to be normal graphic characters, and bracket sequences
14789 are never recognized as wide characters.
14791 If no @code{-gnatW?} parameter is present, then the default
14792 representation is normally Brackets encoding only. However, if the
14793 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
14794 byte order mark or BOM for UTF-8), then these three characters are
14795 skipped and the default representation for the file is set to UTF-8.
14797 Note that the wide character representation that is specified (explicitly
14798 or by default) for the main program also acts as the default encoding used
14799 for Wide_Text_IO files if not specifically overridden by a WCEM form
14803 When no @code{-gnatW?} is specified, then characters (other than wide
14804 characters represented using brackets notation) are treated as 8-bit
14805 Latin-1 codes. The codes recognized are the Latin-1 graphic characters,
14806 and ASCII format effectors (CR, LF, HT, VT). Other lower half control
14807 characters in the range 16#00#..16#1F# are not accepted in program text
14808 or in comments. Upper half control characters (16#80#..16#9F#) are rejected
14809 in program text, but allowed and ignored in comments. Note in particular
14810 that the Next Line (NEL) character whose encoding is 16#85# is not recognized
14811 as an end of line in this default mode. If your source program contains
14812 instances of the NEL character used as a line terminator,
14813 you must use UTF-8 encoding for the whole
14814 source program. In default mode, all lines must be ended by a standard
14815 end of line sequence (CR, CR/LF, or LF).
14817 Note that the convention of simply accepting all upper half characters in
14818 comments means that programs that use standard ASCII for program text, but
14819 UTF-8 encoding for comments are accepted in default mode, providing that the
14820 comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator.
14821 This is a common mode for many programs with foreign language comments.
14823 @node File Naming Control,Subprogram Inlining Control,Character Set Control,Compiler Switches
14824 @anchor{gnat_ugn/building_executable_programs_with_gnat file-naming-control}@anchor{10b}@anchor{gnat_ugn/building_executable_programs_with_gnat id24}@anchor{10c}
14825 @subsection File Naming Control
14828 @geindex -gnatk (gcc)
14833 @item @code{-gnatk@emph{n}}
14835 Activates file name 'krunching'. @code{n}, a decimal integer in the range
14836 1-999, indicates the maximum allowable length of a file name (not
14837 including the @code{.ads} or @code{.adb} extension). The default is not
14838 to enable file name krunching.
14840 For the source file naming rules, @ref{52,,File Naming Rules}.
14843 @node Subprogram Inlining Control,Auxiliary Output Control,File Naming Control,Compiler Switches
14844 @anchor{gnat_ugn/building_executable_programs_with_gnat subprogram-inlining-control}@anchor{10d}@anchor{gnat_ugn/building_executable_programs_with_gnat id25}@anchor{10e}
14845 @subsection Subprogram Inlining Control
14848 @geindex -gnatn (gcc)
14853 @item @code{-gnatn[12]}
14855 The @code{n} here is intended to suggest the first syllable of the word 'inline'.
14856 GNAT recognizes and processes @code{Inline} pragmas. However, for inlining to
14857 actually occur, optimization must be enabled and, by default, inlining of
14858 subprograms across units is not performed. If you want to additionally
14859 enable inlining of subprograms specified by pragma @code{Inline} across units,
14860 you must also specify this switch.
14862 In the absence of this switch, GNAT does not attempt inlining across units
14863 and does not access the bodies of subprograms for which @code{pragma Inline} is
14864 specified if they are not in the current unit.
14866 You can optionally specify the inlining level: 1 for moderate inlining across
14867 units, which is a good compromise between compilation times and performances
14868 at run time, or 2 for full inlining across units, which may bring about
14869 longer compilation times. If no inlining level is specified, the compiler will
14870 pick it based on the optimization level: 1 for @code{-O1}, @code{-O2} or
14871 @code{-Os} and 2 for @code{-O3}.
14873 If you specify this switch the compiler will access these bodies,
14874 creating an extra source dependency for the resulting object file, and
14875 where possible, the call will be inlined.
14876 For further details on when inlining is possible
14877 see @ref{10f,,Inlining of Subprograms}.
14880 @geindex -gnatN (gcc)
14885 @item @code{-gnatN}
14887 This switch activates front-end inlining which also
14888 generates additional dependencies.
14890 When using a gcc-based back end (in practice this means using any version
14891 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
14892 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
14893 Historically front end inlining was more extensive than the gcc back end
14894 inlining, but that is no longer the case.
14897 @node Auxiliary Output Control,Debugging Control,Subprogram Inlining Control,Compiler Switches
14898 @anchor{gnat_ugn/building_executable_programs_with_gnat auxiliary-output-control}@anchor{110}@anchor{gnat_ugn/building_executable_programs_with_gnat id26}@anchor{111}
14899 @subsection Auxiliary Output Control
14902 @geindex -gnatt (gcc)
14904 @geindex Writing internal trees
14906 @geindex Internal trees
14907 @geindex writing to file
14912 @item @code{-gnatt}
14914 Causes GNAT to write the internal tree for a unit to a file (with the
14915 extension @code{.adt}.
14916 This not normally required, but is used by separate analysis tools.
14918 these tools do the necessary compilations automatically, so you should
14919 not have to specify this switch in normal operation.
14920 Note that the combination of switches @code{-gnatct}
14921 generates a tree in the form required by ASIS applications.
14924 @geindex -gnatu (gcc)
14929 @item @code{-gnatu}
14931 Print a list of units required by this compilation on @code{stdout}.
14932 The listing includes all units on which the unit being compiled depends
14933 either directly or indirectly.
14936 @geindex -pass-exit-codes (gcc)
14941 @item @code{-pass-exit-codes}
14943 If this switch is not used, the exit code returned by @code{gcc} when
14944 compiling multiple files indicates whether all source files have
14945 been successfully used to generate object files or not.
14947 When @code{-pass-exit-codes} is used, @code{gcc} exits with an extended
14948 exit status and allows an integrated development environment to better
14949 react to a compilation failure. Those exit status are:
14952 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14959 There was an error in at least one source file.
14967 At least one source file did not generate an object file.
14975 The compiler died unexpectedly (internal error for example).
14983 An object file has been generated for every source file.
14989 @node Debugging Control,Exception Handling Control,Auxiliary Output Control,Compiler Switches
14990 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-control}@anchor{112}@anchor{gnat_ugn/building_executable_programs_with_gnat id27}@anchor{113}
14991 @subsection Debugging Control
14996 @geindex Debugging options
14999 @geindex -gnatd (gcc)
15004 @item @code{-gnatd@emph{x}}
15006 Activate internal debugging switches. @code{x} is a letter or digit, or
15007 string of letters or digits, which specifies the type of debugging
15008 outputs desired. Normally these are used only for internal development
15009 or system debugging purposes. You can find full documentation for these
15010 switches in the body of the @code{Debug} unit in the compiler source
15011 file @code{debug.adb}.
15014 @geindex -gnatG (gcc)
15019 @item @code{-gnatG[=@emph{nn}]}
15021 This switch causes the compiler to generate auxiliary output containing
15022 a pseudo-source listing of the generated expanded code. Like most Ada
15023 compilers, GNAT works by first transforming the high level Ada code into
15024 lower level constructs. For example, tasking operations are transformed
15025 into calls to the tasking run-time routines. A unique capability of GNAT
15026 is to list this expanded code in a form very close to normal Ada source.
15027 This is very useful in understanding the implications of various Ada
15028 usage on the efficiency of the generated code. There are many cases in
15029 Ada (e.g., the use of controlled types), where simple Ada statements can
15030 generate a lot of run-time code. By using @code{-gnatG} you can identify
15031 these cases, and consider whether it may be desirable to modify the coding
15032 approach to improve efficiency.
15034 The optional parameter @code{nn} if present after -gnatG specifies an
15035 alternative maximum line length that overrides the normal default of 72.
15036 This value is in the range 40-999999, values less than 40 being silently
15037 reset to 40. The equal sign is optional.
15039 The format of the output is very similar to standard Ada source, and is
15040 easily understood by an Ada programmer. The following special syntactic
15041 additions correspond to low level features used in the generated code that
15042 do not have any exact analogies in pure Ada source form. The following
15043 is a partial list of these special constructions. See the spec
15044 of package @code{Sprint} in file @code{sprint.ads} for a full list.
15046 @geindex -gnatL (gcc)
15048 If the switch @code{-gnatL} is used in conjunction with
15049 @code{-gnatG}, then the original source lines are interspersed
15050 in the expanded source (as comment lines with the original line number).
15055 @item @code{new @emph{xxx} [storage_pool = @emph{yyy}]}
15057 Shows the storage pool being used for an allocator.
15059 @item @code{at end @emph{procedure-name};}
15061 Shows the finalization (cleanup) procedure for a scope.
15063 @item @code{(if @emph{expr} then @emph{expr} else @emph{expr})}
15065 Conditional expression equivalent to the @code{x?y:z} construction in C.
15067 @item @code{@emph{target}^(@emph{source})}
15069 A conversion with floating-point truncation instead of rounding.
15071 @item @code{@emph{target}?(@emph{source})}
15073 A conversion that bypasses normal Ada semantic checking. In particular
15074 enumeration types and fixed-point types are treated simply as integers.
15076 @item @code{@emph{target}?^(@emph{source})}
15078 Combines the above two cases.
15081 @code{@emph{x} #/ @emph{y}}
15083 @code{@emph{x} #mod @emph{y}}
15085 @code{@emph{x} # @emph{y}}
15090 @item @code{@emph{x} #rem @emph{y}}
15092 A division or multiplication of fixed-point values which are treated as
15093 integers without any kind of scaling.
15095 @item @code{free @emph{expr} [storage_pool = @emph{xxx}]}
15097 Shows the storage pool associated with a @code{free} statement.
15099 @item @code{[subtype or type declaration]}
15101 Used to list an equivalent declaration for an internally generated
15102 type that is referenced elsewhere in the listing.
15104 @item @code{freeze @emph{type-name} [@emph{actions}]}
15106 Shows the point at which @code{type-name} is frozen, with possible
15107 associated actions to be performed at the freeze point.
15109 @item @code{reference @emph{itype}}
15111 Reference (and hence definition) to internal type @code{itype}.
15113 @item @code{@emph{function-name}! (@emph{arg}, @emph{arg}, @emph{arg})}
15115 Intrinsic function call.
15117 @item @code{@emph{label-name} : label}
15119 Declaration of label @code{labelname}.
15121 @item @code{#$ @emph{subprogram-name}}
15123 An implicit call to a run-time support routine
15124 (to meet the requirement of H.3.1(9) in a
15125 convenient manner).
15127 @item @code{@emph{expr} && @emph{expr} && @emph{expr} ... && @emph{expr}}
15129 A multiple concatenation (same effect as @code{expr} & @code{expr} &
15130 @code{expr}, but handled more efficiently).
15132 @item @code{[constraint_error]}
15134 Raise the @code{Constraint_Error} exception.
15136 @item @code{@emph{expression}'reference}
15138 A pointer to the result of evaluating @{expression@}.
15140 @item @code{@emph{target-type}!(@emph{source-expression})}
15142 An unchecked conversion of @code{source-expression} to @code{target-type}.
15144 @item @code{[@emph{numerator}/@emph{denominator}]}
15146 Used to represent internal real literals (that) have no exact
15147 representation in base 2-16 (for example, the result of compile time
15148 evaluation of the expression 1.0/27.0).
15152 @geindex -gnatD (gcc)
15157 @item @code{-gnatD[=nn]}
15159 When used in conjunction with @code{-gnatG}, this switch causes
15160 the expanded source, as described above for
15161 @code{-gnatG} to be written to files with names
15162 @code{xxx.dg}, where @code{xxx} is the normal file name,
15163 instead of to the standard output file. For
15164 example, if the source file name is @code{hello.adb}, then a file
15165 @code{hello.adb.dg} will be written. The debugging
15166 information generated by the @code{gcc} @code{-g} switch
15167 will refer to the generated @code{xxx.dg} file. This allows
15168 you to do source level debugging using the generated code which is
15169 sometimes useful for complex code, for example to find out exactly
15170 which part of a complex construction raised an exception. This switch
15171 also suppresses generation of cross-reference information (see
15172 @code{-gnatx}) since otherwise the cross-reference information
15173 would refer to the @code{.dg} file, which would cause
15174 confusion since this is not the original source file.
15176 Note that @code{-gnatD} actually implies @code{-gnatG}
15177 automatically, so it is not necessary to give both options.
15178 In other words @code{-gnatD} is equivalent to @code{-gnatDG}).
15180 @geindex -gnatL (gcc)
15182 If the switch @code{-gnatL} is used in conjunction with
15183 @code{-gnatDG}, then the original source lines are interspersed
15184 in the expanded source (as comment lines with the original line number).
15186 The optional parameter @code{nn} if present after -gnatD specifies an
15187 alternative maximum line length that overrides the normal default of 72.
15188 This value is in the range 40-999999, values less than 40 being silently
15189 reset to 40. The equal sign is optional.
15192 @geindex -gnatr (gcc)
15194 @geindex pragma Restrictions
15199 @item @code{-gnatr}
15201 This switch causes pragma Restrictions to be treated as Restriction_Warnings
15202 so that violation of restrictions causes warnings rather than illegalities.
15203 This is useful during the development process when new restrictions are added
15204 or investigated. The switch also causes pragma Profile to be treated as
15205 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
15206 restriction warnings rather than restrictions.
15209 @geindex -gnatR (gcc)
15214 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
15216 This switch controls output from the compiler of a listing showing
15217 representation information for declared types, objects and subprograms.
15218 For @code{-gnatR0}, no information is output (equivalent to omitting
15219 the @code{-gnatR} switch). For @code{-gnatR1} (which is the default,
15220 so @code{-gnatR} with no parameter has the same effect), size and
15221 alignment information is listed for declared array and record types.
15223 For @code{-gnatR2}, size and alignment information is listed for all
15224 declared types and objects. The @code{Linker_Section} is also listed for any
15225 entity for which the @code{Linker_Section} is set explicitly or implicitly (the
15226 latter case occurs for objects of a type for which a @code{Linker_Section}
15229 For @code{-gnatR3}, symbolic expressions for values that are computed
15230 at run time for records are included. These symbolic expressions have
15231 a mostly obvious format with #n being used to represent the value of the
15232 n'th discriminant. See source files @code{repinfo.ads/adb} in the
15233 GNAT sources for full details on the format of @code{-gnatR3} output.
15235 For @code{-gnatR4}, information for relevant compiler-generated types
15236 is also listed, i.e. when they are structurally part of other declared
15239 If the switch is followed by an @code{e} (e.g. @code{-gnatR2e}), then
15240 extended representation information for record sub-components of records
15243 If the switch is followed by an @code{m} (e.g. @code{-gnatRm}), then
15244 subprogram conventions and parameter passing mechanisms for all the
15245 subprograms are included.
15247 If the switch is followed by a @code{j} (e.g., @code{-gnatRj}), then
15248 the output is in the JSON data interchange format specified by the
15249 ECMA-404 standard. The semantic description of this JSON output is
15250 available in the specification of the Repinfo unit present in the
15253 If the switch is followed by an @code{s} (e.g., @code{-gnatR3s}), then
15254 the output is to a file with the name @code{file.rep} where @code{file} is
15255 the name of the corresponding source file, except if @code{j} is also
15256 specified, in which case the file name is @code{file.json}.
15258 Note that it is possible for record components to have zero size. In
15259 this case, the component clause uses an obvious extension of permitted
15260 Ada syntax, for example @code{at 0 range 0 .. -1}.
15263 @geindex -gnatS (gcc)
15268 @item @code{-gnatS}
15270 The use of the switch @code{-gnatS} for an
15271 Ada compilation will cause the compiler to output a
15272 representation of package Standard in a form very
15273 close to standard Ada. It is not quite possible to
15274 do this entirely in standard Ada (since new
15275 numeric base types cannot be created in standard
15276 Ada), but the output is easily
15277 readable to any Ada programmer, and is useful to
15278 determine the characteristics of target dependent
15279 types in package Standard.
15282 @geindex -gnatx (gcc)
15287 @item @code{-gnatx}
15289 Normally the compiler generates full cross-referencing information in
15290 the @code{ALI} file. This information is used by a number of tools,
15291 including @code{gnatfind} and @code{gnatxref}. The @code{-gnatx} switch
15292 suppresses this information. This saves some space and may slightly
15293 speed up compilation, but means that these tools cannot be used.
15296 @geindex -fgnat-encodings (gcc)
15301 @item @code{-fgnat-encodings=[all|gdb|minimal]}
15303 This switch controls the balance between GNAT encodings and standard DWARF
15304 emitted in the debug information.
15306 Historically, old debug formats like stabs were not powerful enough to
15307 express some Ada types (for instance, variant records or fixed-point types).
15308 To work around this, GNAT introduced proprietary encodings that embed the
15309 missing information ("GNAT encodings").
15311 Recent versions of the DWARF debug information format are now able to
15312 correctly describe most of these Ada constructs ("standard DWARF"). As
15313 third-party tools started to use this format, GNAT has been enhanced to
15314 generate it. However, most tools (including GDB) are still relying on GNAT
15317 To support all tools, GNAT needs to be versatile about the balance between
15318 generation of GNAT encodings and standard DWARF. This is what
15319 @code{-fgnat-encodings} is about.
15325 @code{=all}: Emit all GNAT encodings, and then emit as much standard DWARF as
15326 possible so it does not conflict with GNAT encodings.
15329 @code{=gdb}: Emit as much standard DWARF as possible as long as the current
15330 GDB handles it. Emit GNAT encodings for the rest.
15333 @code{=minimal}: Emit as much standard DWARF as possible and emit GNAT
15334 encodings for the rest.
15338 @node Exception Handling Control,Units to Sources Mapping Files,Debugging Control,Compiler Switches
15339 @anchor{gnat_ugn/building_executable_programs_with_gnat id28}@anchor{114}@anchor{gnat_ugn/building_executable_programs_with_gnat exception-handling-control}@anchor{115}
15340 @subsection Exception Handling Control
15343 GNAT uses two methods for handling exceptions at run time. The
15344 @code{setjmp/longjmp} method saves the context when entering
15345 a frame with an exception handler. Then when an exception is
15346 raised, the context can be restored immediately, without the
15347 need for tracing stack frames. This method provides very fast
15348 exception propagation, but introduces significant overhead for
15349 the use of exception handlers, even if no exception is raised.
15351 The other approach is called 'zero cost' exception handling.
15352 With this method, the compiler builds static tables to describe
15353 the exception ranges. No dynamic code is required when entering
15354 a frame containing an exception handler. When an exception is
15355 raised, the tables are used to control a back trace of the
15356 subprogram invocation stack to locate the required exception
15357 handler. This method has considerably poorer performance for
15358 the propagation of exceptions, but there is no overhead for
15359 exception handlers if no exception is raised. Note that in this
15360 mode and in the context of mixed Ada and C/C++ programming,
15361 to propagate an exception through a C/C++ code, the C/C++ code
15362 must be compiled with the @code{-funwind-tables} GCC's
15365 The following switches may be used to control which of the
15366 two exception handling methods is used.
15368 @geindex --RTS=sjlj (gnatmake)
15373 @item @code{--RTS=sjlj}
15375 This switch causes the setjmp/longjmp run-time (when available) to be used
15376 for exception handling. If the default
15377 mechanism for the target is zero cost exceptions, then
15378 this switch can be used to modify this default, and must be
15379 used for all units in the partition.
15380 This option is rarely used. One case in which it may be
15381 advantageous is if you have an application where exception
15382 raising is common and the overall performance of the
15383 application is improved by favoring exception propagation.
15386 @geindex --RTS=zcx (gnatmake)
15388 @geindex Zero Cost Exceptions
15393 @item @code{--RTS=zcx}
15395 This switch causes the zero cost approach to be used
15396 for exception handling. If this is the default mechanism for the
15397 target (see below), then this switch is unneeded. If the default
15398 mechanism for the target is setjmp/longjmp exceptions, then
15399 this switch can be used to modify this default, and must be
15400 used for all units in the partition.
15401 This option can only be used if the zero cost approach
15402 is available for the target in use, otherwise it will generate an error.
15405 The same option @code{--RTS} must be used both for @code{gcc}
15406 and @code{gnatbind}. Passing this option to @code{gnatmake}
15407 (@ref{dc,,Switches for gnatmake}) will ensure the required consistency
15408 through the compilation and binding steps.
15410 @node Units to Sources Mapping Files,Code Generation Control,Exception Handling Control,Compiler Switches
15411 @anchor{gnat_ugn/building_executable_programs_with_gnat id29}@anchor{116}@anchor{gnat_ugn/building_executable_programs_with_gnat units-to-sources-mapping-files}@anchor{f7}
15412 @subsection Units to Sources Mapping Files
15415 @geindex -gnatem (gcc)
15420 @item @code{-gnatem=@emph{path}}
15422 A mapping file is a way to communicate to the compiler two mappings:
15423 from unit names to file names (without any directory information) and from
15424 file names to path names (with full directory information). These mappings
15425 are used by the compiler to short-circuit the path search.
15427 The use of mapping files is not required for correct operation of the
15428 compiler, but mapping files can improve efficiency, particularly when
15429 sources are read over a slow network connection. In normal operation,
15430 you need not be concerned with the format or use of mapping files,
15431 and the @code{-gnatem} switch is not a switch that you would use
15432 explicitly. It is intended primarily for use by automatic tools such as
15433 @code{gnatmake} running under the project file facility. The
15434 description here of the format of mapping files is provided
15435 for completeness and for possible use by other tools.
15437 A mapping file is a sequence of sets of three lines. In each set, the
15438 first line is the unit name, in lower case, with @code{%s} appended
15439 for specs and @code{%b} appended for bodies; the second line is the
15440 file name; and the third line is the path name.
15447 /gnat/project1/sources/main.2.ada
15450 When the switch @code{-gnatem} is specified, the compiler will
15451 create in memory the two mappings from the specified file. If there is
15452 any problem (nonexistent file, truncated file or duplicate entries),
15453 no mapping will be created.
15455 Several @code{-gnatem} switches may be specified; however, only the
15456 last one on the command line will be taken into account.
15458 When using a project file, @code{gnatmake} creates a temporary
15459 mapping file and communicates it to the compiler using this switch.
15462 @node Code Generation Control,,Units to Sources Mapping Files,Compiler Switches
15463 @anchor{gnat_ugn/building_executable_programs_with_gnat code-generation-control}@anchor{117}@anchor{gnat_ugn/building_executable_programs_with_gnat id30}@anchor{118}
15464 @subsection Code Generation Control
15467 The GCC technology provides a wide range of target dependent
15468 @code{-m} switches for controlling
15469 details of code generation with respect to different versions of
15470 architectures. This includes variations in instruction sets (e.g.,
15471 different members of the power pc family), and different requirements
15472 for optimal arrangement of instructions (e.g., different members of
15473 the x86 family). The list of available @code{-m} switches may be
15474 found in the GCC documentation.
15476 Use of these @code{-m} switches may in some cases result in improved
15479 The GNAT technology is tested and qualified without any
15480 @code{-m} switches,
15481 so generally the most reliable approach is to avoid the use of these
15482 switches. However, we generally expect most of these switches to work
15483 successfully with GNAT, and many customers have reported successful
15484 use of these options.
15486 Our general advice is to avoid the use of @code{-m} switches unless
15487 special needs lead to requirements in this area. In particular,
15488 there is no point in using @code{-m} switches to improve performance
15489 unless you actually see a performance improvement.
15491 @node Linker Switches,Binding with gnatbind,Compiler Switches,Building Executable Programs with GNAT
15492 @anchor{gnat_ugn/building_executable_programs_with_gnat linker-switches}@anchor{119}@anchor{gnat_ugn/building_executable_programs_with_gnat id31}@anchor{11a}
15493 @section Linker Switches
15496 Linker switches can be specified after @code{-largs} builder switch.
15498 @geindex -fuse-ld=name
15503 @item @code{-fuse-ld=@emph{name}}
15505 Linker to be used. The default is @code{bfd} for @code{ld.bfd},
15506 the alternative being @code{gold} for @code{ld.gold}. The later is
15507 a more recent and faster linker, but only available on GNU/Linux
15511 @node Binding with gnatbind,Linking with gnatlink,Linker Switches,Building Executable Programs with GNAT
15512 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-gnatbind}@anchor{1d}@anchor{gnat_ugn/building_executable_programs_with_gnat id32}@anchor{11b}
15513 @section Binding with @code{gnatbind}
15518 This chapter describes the GNAT binder, @code{gnatbind}, which is used
15519 to bind compiled GNAT objects.
15521 The @code{gnatbind} program performs four separate functions:
15527 Checks that a program is consistent, in accordance with the rules in
15528 Chapter 10 of the Ada Reference Manual. In particular, error
15529 messages are generated if a program uses inconsistent versions of a
15533 Checks that an acceptable order of elaboration exists for the program
15534 and issues an error message if it cannot find an order of elaboration
15535 that satisfies the rules in Chapter 10 of the Ada Language Manual.
15538 Generates a main program incorporating the given elaboration order.
15539 This program is a small Ada package (body and spec) that
15540 must be subsequently compiled
15541 using the GNAT compiler. The necessary compilation step is usually
15542 performed automatically by @code{gnatlink}. The two most important
15543 functions of this program
15544 are to call the elaboration routines of units in an appropriate order
15545 and to call the main program.
15548 Determines the set of object files required by the given main program.
15549 This information is output in the forms of comments in the generated program,
15550 to be read by the @code{gnatlink} utility used to link the Ada application.
15554 * Running gnatbind::
15555 * Switches for gnatbind::
15556 * Command-Line Access::
15557 * Search Paths for gnatbind::
15558 * Examples of gnatbind Usage::
15562 @node Running gnatbind,Switches for gnatbind,,Binding with gnatbind
15563 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatbind}@anchor{11c}@anchor{gnat_ugn/building_executable_programs_with_gnat id33}@anchor{11d}
15564 @subsection Running @code{gnatbind}
15567 The form of the @code{gnatbind} command is
15570 $ gnatbind [ switches ] mainprog[.ali] [ switches ]
15573 where @code{mainprog.adb} is the Ada file containing the main program
15574 unit body. @code{gnatbind} constructs an Ada
15575 package in two files whose names are
15576 @code{b~mainprog.ads}, and @code{b~mainprog.adb}.
15577 For example, if given the
15578 parameter @code{hello.ali}, for a main program contained in file
15579 @code{hello.adb}, the binder output files would be @code{b~hello.ads}
15580 and @code{b~hello.adb}.
15582 When doing consistency checking, the binder takes into consideration
15583 any source files it can locate. For example, if the binder determines
15584 that the given main program requires the package @code{Pack}, whose
15586 file is @code{pack.ali} and whose corresponding source spec file is
15587 @code{pack.ads}, it attempts to locate the source file @code{pack.ads}
15588 (using the same search path conventions as previously described for the
15589 @code{gcc} command). If it can locate this source file, it checks that
15591 or source checksums of the source and its references to in @code{ALI} files
15592 match. In other words, any @code{ALI} files that mentions this spec must have
15593 resulted from compiling this version of the source file (or in the case
15594 where the source checksums match, a version close enough that the
15595 difference does not matter).
15597 @geindex Source files
15598 @geindex use by binder
15600 The effect of this consistency checking, which includes source files, is
15601 that the binder ensures that the program is consistent with the latest
15602 version of the source files that can be located at bind time. Editing a
15603 source file without compiling files that depend on the source file cause
15604 error messages to be generated by the binder.
15606 For example, suppose you have a main program @code{hello.adb} and a
15607 package @code{P}, from file @code{p.ads} and you perform the following
15614 Enter @code{gcc -c hello.adb} to compile the main program.
15617 Enter @code{gcc -c p.ads} to compile package @code{P}.
15620 Edit file @code{p.ads}.
15623 Enter @code{gnatbind hello}.
15626 At this point, the file @code{p.ali} contains an out-of-date time stamp
15627 because the file @code{p.ads} has been edited. The attempt at binding
15628 fails, and the binder generates the following error messages:
15631 error: "hello.adb" must be recompiled ("p.ads" has been modified)
15632 error: "p.ads" has been modified and must be recompiled
15635 Now both files must be recompiled as indicated, and then the bind can
15636 succeed, generating a main program. You need not normally be concerned
15637 with the contents of this file, but for reference purposes a sample
15638 binder output file is given in @ref{e,,Example of Binder Output File}.
15640 In most normal usage, the default mode of @code{gnatbind} which is to
15641 generate the main package in Ada, as described in the previous section.
15642 In particular, this means that any Ada programmer can read and understand
15643 the generated main program. It can also be debugged just like any other
15644 Ada code provided the @code{-g} switch is used for
15645 @code{gnatbind} and @code{gnatlink}.
15647 @node Switches for gnatbind,Command-Line Access,Running gnatbind,Binding with gnatbind
15648 @anchor{gnat_ugn/building_executable_programs_with_gnat id34}@anchor{11e}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatbind}@anchor{11f}
15649 @subsection Switches for @code{gnatbind}
15652 The following switches are available with @code{gnatbind}; details will
15653 be presented in subsequent sections.
15655 @geindex --version (gnatbind)
15660 @item @code{--version}
15662 Display Copyright and version, then exit disregarding all other options.
15665 @geindex --help (gnatbind)
15670 @item @code{--help}
15672 If @code{--version} was not used, display usage, then exit disregarding
15676 @geindex -a (gnatbind)
15683 Indicates that, if supported by the platform, the adainit procedure should
15684 be treated as an initialisation routine by the linker (a constructor). This
15685 is intended to be used by the Project Manager to automatically initialize
15686 shared Stand-Alone Libraries.
15689 @geindex -aO (gnatbind)
15696 Specify directory to be searched for ALI files.
15699 @geindex -aI (gnatbind)
15706 Specify directory to be searched for source file.
15709 @geindex -A (gnatbind)
15714 @item @code{-A[=@emph{filename}]}
15716 Output ALI list (to standard output or to the named file).
15719 @geindex -b (gnatbind)
15726 Generate brief messages to @code{stderr} even if verbose mode set.
15729 @geindex -c (gnatbind)
15736 Check only, no generation of binder output file.
15739 @geindex -dnn[k|m] (gnatbind)
15744 @item @code{-d@emph{nn}[k|m]}
15746 This switch can be used to change the default task stack size value
15747 to a specified size @code{nn}, which is expressed in bytes by default, or
15748 in kilobytes when suffixed with @code{k} or in megabytes when suffixed
15750 In the absence of a @code{[k|m]} suffix, this switch is equivalent,
15751 in effect, to completing all task specs with
15754 pragma Storage_Size (nn);
15757 When they do not already have such a pragma.
15760 @geindex -D (gnatbind)
15765 @item @code{-D@emph{nn}[k|m]}
15767 Set the default secondary stack size to @code{nn}. The suffix indicates whether
15768 the size is in bytes (no suffix), kilobytes (@code{k} suffix) or megabytes
15771 The secondary stack holds objects of unconstrained types that are returned by
15772 functions, for example unconstrained Strings. The size of the secondary stack
15773 can be dynamic or fixed depending on the target.
15775 For most targets, the secondary stack grows on demand and is implemented as
15776 a chain of blocks in the heap. In this case, the default secondary stack size
15777 determines the initial size of the secondary stack for each task and the
15778 smallest amount the secondary stack can grow by.
15780 For Ravenscar, ZFP, and Cert run-times the size of the secondary stack is
15781 fixed. This switch can be used to change the default size of these stacks.
15782 The default secondary stack size can be overridden on a per-task basis if
15783 individual tasks have different secondary stack requirements. This is
15784 achieved through the Secondary_Stack_Size aspect that takes the size of the
15785 secondary stack in bytes.
15788 @geindex -e (gnatbind)
15795 Output complete list of elaboration-order dependencies.
15798 @geindex -Ea (gnatbind)
15805 Store tracebacks in exception occurrences when the target supports it.
15806 The "a" is for "address"; tracebacks will contain hexadecimal addresses,
15807 unless symbolic tracebacks are enabled.
15809 See also the packages @code{GNAT.Traceback} and
15810 @code{GNAT.Traceback.Symbolic} for more information.
15811 Note that on x86 ports, you must not use @code{-fomit-frame-pointer}
15815 @geindex -Es (gnatbind)
15822 Store tracebacks in exception occurrences when the target supports it.
15823 The "s" is for "symbolic"; symbolic tracebacks are enabled.
15826 @geindex -E (gnatbind)
15833 Currently the same as @code{-Ea}.
15836 @geindex -f (gnatbind)
15841 @item @code{-f@emph{elab-order}}
15843 Force elaboration order. For further details see @ref{120,,Elaboration Control}
15844 and @ref{f,,Elaboration Order Handling in GNAT}.
15847 @geindex -F (gnatbind)
15854 Force the checks of elaboration flags. @code{gnatbind} does not normally
15855 generate checks of elaboration flags for the main executable, except when
15856 a Stand-Alone Library is used. However, there are cases when this cannot be
15857 detected by gnatbind. An example is importing an interface of a Stand-Alone
15858 Library through a pragma Import and only specifying through a linker switch
15859 this Stand-Alone Library. This switch is used to guarantee that elaboration
15860 flag checks are generated.
15863 @geindex -h (gnatbind)
15870 Output usage (help) information.
15873 @geindex -H (gnatbind)
15880 Legacy elaboration order model enabled. For further details see
15881 @ref{f,,Elaboration Order Handling in GNAT}.
15884 @geindex -H32 (gnatbind)
15891 Use 32-bit allocations for @code{__gnat_malloc} (and thus for access types).
15892 For further details see @ref{121,,Dynamic Allocation Control}.
15895 @geindex -H64 (gnatbind)
15897 @geindex __gnat_malloc
15904 Use 64-bit allocations for @code{__gnat_malloc} (and thus for access types).
15905 For further details see @ref{121,,Dynamic Allocation Control}.
15907 @geindex -I (gnatbind)
15911 Specify directory to be searched for source and ALI files.
15913 @geindex -I- (gnatbind)
15917 Do not look for sources in the current directory where @code{gnatbind} was
15918 invoked, and do not look for ALI files in the directory containing the
15919 ALI file named in the @code{gnatbind} command line.
15921 @geindex -l (gnatbind)
15925 Output chosen elaboration order.
15927 @geindex -L (gnatbind)
15929 @item @code{-L@emph{xxx}}
15931 Bind the units for library building. In this case the @code{adainit} and
15932 @code{adafinal} procedures (@ref{b4,,Binding with Non-Ada Main Programs})
15933 are renamed to @code{@emph{xxx}init} and
15934 @code{@emph{xxx}final}.
15936 (@ref{15,,GNAT and Libraries}, for more details.)
15938 @geindex -M (gnatbind)
15940 @item @code{-M@emph{xyz}}
15942 Rename generated main program from main to xyz. This option is
15943 supported on cross environments only.
15945 @geindex -m (gnatbind)
15947 @item @code{-m@emph{n}}
15949 Limit number of detected errors or warnings to @code{n}, where @code{n} is
15950 in the range 1..999999. The default value if no switch is
15951 given is 9999. If the number of warnings reaches this limit, then a
15952 message is output and further warnings are suppressed, the bind
15953 continues in this case. If the number of errors reaches this
15954 limit, then a message is output and the bind is abandoned.
15955 A value of zero means that no limit is enforced. The equal
15958 @geindex -minimal (gnatbind)
15960 @item @code{-minimal}
15962 Generate a binder file suitable for space-constrained applications. When
15963 active, binder-generated objects not required for program operation are no
15964 longer generated. @strong{Warning:} this option comes with the following
15971 Debugging will not work;
15974 Programs using GNAT.Compiler_Version will not link.
15977 @geindex -n (gnatbind)
15983 @geindex -nostdinc (gnatbind)
15985 @item @code{-nostdinc}
15987 Do not look for sources in the system default directory.
15989 @geindex -nostdlib (gnatbind)
15991 @item @code{-nostdlib}
15993 Do not look for library files in the system default directory.
15995 @geindex --RTS (gnatbind)
15997 @item @code{--RTS=@emph{rts-path}}
15999 Specifies the default location of the run-time library. Same meaning as the
16000 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
16002 @geindex -o (gnatbind)
16004 @item @code{-o @emph{file}}
16006 Name the output file @code{file} (default is @code{b~`xxx}.adb`).
16007 Note that if this option is used, then linking must be done manually,
16008 gnatlink cannot be used.
16010 @geindex -O (gnatbind)
16012 @item @code{-O[=@emph{filename}]}
16014 Output object list (to standard output or to the named file).
16016 @geindex -p (gnatbind)
16020 Pessimistic (worst-case) elaboration order.
16022 @geindex -P (gnatbind)
16026 Generate binder file suitable for CodePeer.
16028 @geindex -R (gnatbind)
16032 Output closure source list, which includes all non-run-time units that are
16033 included in the bind.
16035 @geindex -Ra (gnatbind)
16039 Like @code{-R} but the list includes run-time units.
16041 @geindex -s (gnatbind)
16045 Require all source files to be present.
16047 @geindex -S (gnatbind)
16049 @item @code{-S@emph{xxx}}
16051 Specifies the value to be used when detecting uninitialized scalar
16052 objects with pragma Initialize_Scalars.
16053 The @code{xxx} string specified with the switch is one of:
16059 @code{in} for an invalid value.
16061 If zero is invalid for the discrete type in question,
16062 then the scalar value is set to all zero bits.
16063 For signed discrete types, the largest possible negative value of
16064 the underlying scalar is set (i.e. a one bit followed by all zero bits).
16065 For unsigned discrete types, the underlying scalar value is set to all
16066 one bits. For floating-point types, a NaN value is set
16067 (see body of package System.Scalar_Values for exact values).
16070 @code{lo} for low value.
16072 If zero is invalid for the discrete type in question,
16073 then the scalar value is set to all zero bits.
16074 For signed discrete types, the largest possible negative value of
16075 the underlying scalar is set (i.e. a one bit followed by all zero bits).
16076 For unsigned discrete types, the underlying scalar value is set to all
16077 zero bits. For floating-point, a small value is set
16078 (see body of package System.Scalar_Values for exact values).
16081 @code{hi} for high value.
16083 If zero is invalid for the discrete type in question,
16084 then the scalar value is set to all one bits.
16085 For signed discrete types, the largest possible positive value of
16086 the underlying scalar is set (i.e. a zero bit followed by all one bits).
16087 For unsigned discrete types, the underlying scalar value is set to all
16088 one bits. For floating-point, a large value is set
16089 (see body of package System.Scalar_Values for exact values).
16092 @code{xx} for hex value (two hex digits).
16094 The underlying scalar is set to a value consisting of repeated bytes, whose
16095 value corresponds to the given value. For example if @code{BF} is given,
16096 then a 32-bit scalar value will be set to the bit patterm @code{16#BFBFBFBF#}.
16099 @geindex GNAT_INIT_SCALARS
16101 In addition, you can specify @code{-Sev} to indicate that the value is
16102 to be set at run time. In this case, the program will look for an environment
16103 variable of the form @code{GNAT_INIT_SCALARS=@emph{yy}}, where @code{yy} is one
16104 of @code{in/lo/hi/@emph{xx}} with the same meanings as above.
16105 If no environment variable is found, or if it does not have a valid value,
16106 then the default is @code{in} (invalid values).
16109 @geindex -static (gnatbind)
16114 @item @code{-static}
16116 Link against a static GNAT run-time.
16118 @geindex -shared (gnatbind)
16120 @item @code{-shared}
16122 Link against a shared GNAT run-time when available.
16124 @geindex -t (gnatbind)
16128 Tolerate time stamp and other consistency errors.
16130 @geindex -T (gnatbind)
16132 @item @code{-T@emph{n}}
16134 Set the time slice value to @code{n} milliseconds. If the system supports
16135 the specification of a specific time slice value, then the indicated value
16136 is used. If the system does not support specific time slice values, but
16137 does support some general notion of round-robin scheduling, then any
16138 nonzero value will activate round-robin scheduling.
16140 A value of zero is treated specially. It turns off time
16141 slicing, and in addition, indicates to the tasking run-time that the
16142 semantics should match as closely as possible the Annex D
16143 requirements of the Ada RM, and in particular sets the default
16144 scheduling policy to @code{FIFO_Within_Priorities}.
16146 @geindex -u (gnatbind)
16148 @item @code{-u@emph{n}}
16150 Enable dynamic stack usage, with @code{n} results stored and displayed
16151 at program termination. A result is generated when a task
16152 terminates. Results that can't be stored are displayed on the fly, at
16153 task termination. This option is currently not supported on Itanium
16154 platforms. (See @ref{122,,Dynamic Stack Usage Analysis} for details.)
16156 @geindex -v (gnatbind)
16160 Verbose mode. Write error messages, header, summary output to
16163 @geindex -V (gnatbind)
16165 @item @code{-V@emph{key}=@emph{value}}
16167 Store the given association of @code{key} to @code{value} in the bind environment.
16168 Values stored this way can be retrieved at run time using
16169 @code{GNAT.Bind_Environment}.
16171 @geindex -w (gnatbind)
16173 @item @code{-w@emph{x}}
16175 Warning mode; @code{x} = s/e for suppress/treat as error.
16177 @geindex -Wx (gnatbind)
16179 @item @code{-Wx@emph{e}}
16181 Override default wide character encoding for standard Text_IO files.
16183 @geindex -x (gnatbind)
16187 Exclude source files (check object consistency only).
16189 @geindex -Xnnn (gnatbind)
16191 @item @code{-X@emph{nnn}}
16193 Set default exit status value, normally 0 for POSIX compliance.
16195 @geindex -y (gnatbind)
16199 Enable leap seconds support in @code{Ada.Calendar} and its children.
16201 @geindex -z (gnatbind)
16205 No main subprogram.
16208 You may obtain this listing of switches by running @code{gnatbind} with
16212 * Consistency-Checking Modes::
16213 * Binder Error Message Control::
16214 * Elaboration Control::
16216 * Dynamic Allocation Control::
16217 * Binding with Non-Ada Main Programs::
16218 * Binding Programs with No Main Subprogram::
16222 @node Consistency-Checking Modes,Binder Error Message Control,,Switches for gnatbind
16223 @anchor{gnat_ugn/building_executable_programs_with_gnat consistency-checking-modes}@anchor{123}@anchor{gnat_ugn/building_executable_programs_with_gnat id35}@anchor{124}
16224 @subsubsection Consistency-Checking Modes
16227 As described earlier, by default @code{gnatbind} checks
16228 that object files are consistent with one another and are consistent
16229 with any source files it can locate. The following switches control binder
16234 @geindex -s (gnatbind)
16242 Require source files to be present. In this mode, the binder must be
16243 able to locate all source files that are referenced, in order to check
16244 their consistency. In normal mode, if a source file cannot be located it
16245 is simply ignored. If you specify this switch, a missing source
16248 @geindex -Wx (gnatbind)
16250 @item @code{-Wx@emph{e}}
16252 Override default wide character encoding for standard Text_IO files.
16253 Normally the default wide character encoding method used for standard
16254 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
16255 the main source input (see description of switch
16256 @code{-gnatWx} for the compiler). The
16257 use of this switch for the binder (which has the same set of
16258 possible arguments) overrides this default as specified.
16260 @geindex -x (gnatbind)
16264 Exclude source files. In this mode, the binder only checks that ALI
16265 files are consistent with one another. Source files are not accessed.
16266 The binder runs faster in this mode, and there is still a guarantee that
16267 the resulting program is self-consistent.
16268 If a source file has been edited since it was last compiled, and you
16269 specify this switch, the binder will not detect that the object
16270 file is out of date with respect to the source file. Note that this is the
16271 mode that is automatically used by @code{gnatmake} because in this
16272 case the checking against sources has already been performed by
16273 @code{gnatmake} in the course of compilation (i.e., before binding).
16276 @node Binder Error Message Control,Elaboration Control,Consistency-Checking Modes,Switches for gnatbind
16277 @anchor{gnat_ugn/building_executable_programs_with_gnat id36}@anchor{125}@anchor{gnat_ugn/building_executable_programs_with_gnat binder-error-message-control}@anchor{126}
16278 @subsubsection Binder Error Message Control
16281 The following switches provide control over the generation of error
16282 messages from the binder:
16286 @geindex -v (gnatbind)
16294 Verbose mode. In the normal mode, brief error messages are generated to
16295 @code{stderr}. If this switch is present, a header is written
16296 to @code{stdout} and any error messages are directed to @code{stdout}.
16297 All that is written to @code{stderr} is a brief summary message.
16299 @geindex -b (gnatbind)
16303 Generate brief error messages to @code{stderr} even if verbose mode is
16304 specified. This is relevant only when used with the
16307 @geindex -m (gnatbind)
16309 @item @code{-m@emph{n}}
16311 Limits the number of error messages to @code{n}, a decimal integer in the
16312 range 1-999. The binder terminates immediately if this limit is reached.
16314 @geindex -M (gnatbind)
16316 @item @code{-M@emph{xxx}}
16318 Renames the generated main program from @code{main} to @code{xxx}.
16319 This is useful in the case of some cross-building environments, where
16320 the actual main program is separate from the one generated
16321 by @code{gnatbind}.
16323 @geindex -ws (gnatbind)
16329 Suppress all warning messages.
16331 @geindex -we (gnatbind)
16335 Treat any warning messages as fatal errors.
16337 @geindex -t (gnatbind)
16339 @geindex Time stamp checks
16342 @geindex Binder consistency checks
16344 @geindex Consistency checks
16349 The binder performs a number of consistency checks including:
16355 Check that time stamps of a given source unit are consistent
16358 Check that checksums of a given source unit are consistent
16361 Check that consistent versions of @code{GNAT} were used for compilation
16364 Check consistency of configuration pragmas as required
16367 Normally failure of such checks, in accordance with the consistency
16368 requirements of the Ada Reference Manual, causes error messages to be
16369 generated which abort the binder and prevent the output of a binder
16370 file and subsequent link to obtain an executable.
16372 The @code{-t} switch converts these error messages
16373 into warnings, so that
16374 binding and linking can continue to completion even in the presence of such
16375 errors. The result may be a failed link (due to missing symbols), or a
16376 non-functional executable which has undefined semantics.
16380 This means that @code{-t} should be used only in unusual situations,
16386 @node Elaboration Control,Output Control,Binder Error Message Control,Switches for gnatbind
16387 @anchor{gnat_ugn/building_executable_programs_with_gnat id37}@anchor{127}@anchor{gnat_ugn/building_executable_programs_with_gnat elaboration-control}@anchor{120}
16388 @subsubsection Elaboration Control
16391 The following switches provide additional control over the elaboration
16392 order. For further details see @ref{f,,Elaboration Order Handling in GNAT}.
16394 @geindex -f (gnatbind)
16399 @item @code{-f@emph{elab-order}}
16401 Force elaboration order.
16403 @code{elab-order} should be the name of a "forced elaboration order file", that
16404 is, a text file containing library item names, one per line. A name of the
16405 form "some.unit%s" or "some.unit (spec)" denotes the spec of Some.Unit. A
16406 name of the form "some.unit%b" or "some.unit (body)" denotes the body of
16407 Some.Unit. Each pair of lines is taken to mean that there is an elaboration
16408 dependence of the second line on the first. For example, if the file
16418 then the spec of This will be elaborated before the body of This, and the
16419 body of This will be elaborated before the spec of That, and the spec of That
16420 will be elaborated before the body of That. The first and last of these three
16421 dependences are already required by Ada rules, so this file is really just
16422 forcing the body of This to be elaborated before the spec of That.
16424 The given order must be consistent with Ada rules, or else @code{gnatbind} will
16425 give elaboration cycle errors. For example, if you say x (body) should be
16426 elaborated before x (spec), there will be a cycle, because Ada rules require
16427 x (spec) to be elaborated before x (body); you can't have the spec and body
16428 both elaborated before each other.
16430 If you later add "with That;" to the body of This, there will be a cycle, in
16431 which case you should erase either "this (body)" or "that (spec)" from the
16432 above forced elaboration order file.
16434 Blank lines and Ada-style comments are ignored. Unit names that do not exist
16435 in the program are ignored. Units in the GNAT predefined library are also
16439 @geindex -p (gnatbind)
16446 Pessimistic elaboration order
16448 This switch is only applicable to the pre-20.x legacy elaboration models.
16449 The post-20.x elaboration model uses a more informed approach of ordering
16452 Normally the binder attempts to choose an elaboration order that is likely to
16453 minimize the likelihood of an elaboration order error resulting in raising a
16454 @code{Program_Error} exception. This switch reverses the action of the binder,
16455 and requests that it deliberately choose an order that is likely to maximize
16456 the likelihood of an elaboration error. This is useful in ensuring
16457 portability and avoiding dependence on accidental fortuitous elaboration
16460 Normally it only makes sense to use the @code{-p} switch if dynamic
16461 elaboration checking is used (@code{-gnatE} switch used for compilation).
16462 This is because in the default static elaboration mode, all necessary
16463 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
16464 These implicit pragmas are still respected by the binder in @code{-p}
16465 mode, so a safe elaboration order is assured.
16467 Note that @code{-p} is not intended for production use; it is more for
16468 debugging/experimental use.
16471 @node Output Control,Dynamic Allocation Control,Elaboration Control,Switches for gnatbind
16472 @anchor{gnat_ugn/building_executable_programs_with_gnat output-control}@anchor{128}@anchor{gnat_ugn/building_executable_programs_with_gnat id38}@anchor{129}
16473 @subsubsection Output Control
16476 The following switches allow additional control over the output
16477 generated by the binder.
16481 @geindex -c (gnatbind)
16489 Check only. Do not generate the binder output file. In this mode the
16490 binder performs all error checks but does not generate an output file.
16492 @geindex -e (gnatbind)
16496 Output complete list of elaboration-order dependencies, showing the
16497 reason for each dependency. This output can be rather extensive but may
16498 be useful in diagnosing problems with elaboration order. The output is
16499 written to @code{stdout}.
16501 @geindex -h (gnatbind)
16505 Output usage information. The output is written to @code{stdout}.
16507 @geindex -K (gnatbind)
16511 Output linker options to @code{stdout}. Includes library search paths,
16512 contents of pragmas Ident and Linker_Options, and libraries added
16513 by @code{gnatbind}.
16515 @geindex -l (gnatbind)
16519 Output chosen elaboration order. The output is written to @code{stdout}.
16521 @geindex -O (gnatbind)
16525 Output full names of all the object files that must be linked to provide
16526 the Ada component of the program. The output is written to @code{stdout}.
16527 This list includes the files explicitly supplied and referenced by the user
16528 as well as implicitly referenced run-time unit files. The latter are
16529 omitted if the corresponding units reside in shared libraries. The
16530 directory names for the run-time units depend on the system configuration.
16532 @geindex -o (gnatbind)
16534 @item @code{-o @emph{file}}
16536 Set name of output file to @code{file} instead of the normal
16537 @code{b~`mainprog}.adb` default. Note that @code{file} denote the Ada
16538 binder generated body filename.
16539 Note that if this option is used, then linking must be done manually.
16540 It is not possible to use gnatlink in this case, since it cannot locate
16543 @geindex -r (gnatbind)
16547 Generate list of @code{pragma Restrictions} that could be applied to
16548 the current unit. This is useful for code audit purposes, and also may
16549 be used to improve code generation in some cases.
16552 @node Dynamic Allocation Control,Binding with Non-Ada Main Programs,Output Control,Switches for gnatbind
16553 @anchor{gnat_ugn/building_executable_programs_with_gnat dynamic-allocation-control}@anchor{121}@anchor{gnat_ugn/building_executable_programs_with_gnat id39}@anchor{12a}
16554 @subsubsection Dynamic Allocation Control
16557 The heap control switches -- @code{-H32} and @code{-H64} --
16558 determine whether dynamic allocation uses 32-bit or 64-bit memory.
16559 They only affect compiler-generated allocations via @code{__gnat_malloc};
16560 explicit calls to @code{malloc} and related functions from the C
16561 run-time library are unaffected.
16568 Allocate memory on 32-bit heap
16572 Allocate memory on 64-bit heap. This is the default
16573 unless explicitly overridden by a @code{'Size} clause on the access type.
16576 These switches are only effective on VMS platforms.
16578 @node Binding with Non-Ada Main Programs,Binding Programs with No Main Subprogram,Dynamic Allocation Control,Switches for gnatbind
16579 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-non-ada-main-programs}@anchor{b4}@anchor{gnat_ugn/building_executable_programs_with_gnat id40}@anchor{12b}
16580 @subsubsection Binding with Non-Ada Main Programs
16583 The description so far has assumed that the main
16584 program is in Ada, and that the task of the binder is to generate a
16585 corresponding function @code{main} that invokes this Ada main
16586 program. GNAT also supports the building of executable programs where
16587 the main program is not in Ada, but some of the called routines are
16588 written in Ada and compiled using GNAT (@ref{44,,Mixed Language Programming}).
16589 The following switch is used in this situation:
16593 @geindex -n (gnatbind)
16601 No main program. The main program is not in Ada.
16604 In this case, most of the functions of the binder are still required,
16605 but instead of generating a main program, the binder generates a file
16606 containing the following callable routines:
16615 @item @code{adainit}
16617 You must call this routine to initialize the Ada part of the program by
16618 calling the necessary elaboration routines. A call to @code{adainit} is
16619 required before the first call to an Ada subprogram.
16621 Note that it is assumed that the basic execution environment must be setup
16622 to be appropriate for Ada execution at the point where the first Ada
16623 subprogram is called. In particular, if the Ada code will do any
16624 floating-point operations, then the FPU must be setup in an appropriate
16625 manner. For the case of the x86, for example, full precision mode is
16626 required. The procedure GNAT.Float_Control.Reset may be used to ensure
16627 that the FPU is in the right state.
16635 @item @code{adafinal}
16637 You must call this routine to perform any library-level finalization
16638 required by the Ada subprograms. A call to @code{adafinal} is required
16639 after the last call to an Ada subprogram, and before the program
16644 @geindex -n (gnatbind)
16647 @geindex multiple input files
16649 If the @code{-n} switch
16650 is given, more than one ALI file may appear on
16651 the command line for @code{gnatbind}. The normal @code{closure}
16652 calculation is performed for each of the specified units. Calculating
16653 the closure means finding out the set of units involved by tracing
16654 @emph{with} references. The reason it is necessary to be able to
16655 specify more than one ALI file is that a given program may invoke two or
16656 more quite separate groups of Ada units.
16658 The binder takes the name of its output file from the last specified ALI
16659 file, unless overridden by the use of the @code{-o file}.
16661 @geindex -o (gnatbind)
16663 The output is an Ada unit in source form that can be compiled with GNAT.
16664 This compilation occurs automatically as part of the @code{gnatlink}
16667 Currently the GNAT run-time requires a FPU using 80 bits mode
16668 precision. Under targets where this is not the default it is required to
16669 call GNAT.Float_Control.Reset before using floating point numbers (this
16670 include float computation, float input and output) in the Ada code. A
16671 side effect is that this could be the wrong mode for the foreign code
16672 where floating point computation could be broken after this call.
16674 @node Binding Programs with No Main Subprogram,,Binding with Non-Ada Main Programs,Switches for gnatbind
16675 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-programs-with-no-main-subprogram}@anchor{12c}@anchor{gnat_ugn/building_executable_programs_with_gnat id41}@anchor{12d}
16676 @subsubsection Binding Programs with No Main Subprogram
16679 It is possible to have an Ada program which does not have a main
16680 subprogram. This program will call the elaboration routines of all the
16681 packages, then the finalization routines.
16683 The following switch is used to bind programs organized in this manner:
16687 @geindex -z (gnatbind)
16695 Normally the binder checks that the unit name given on the command line
16696 corresponds to a suitable main subprogram. When this switch is used,
16697 a list of ALI files can be given, and the execution of the program
16698 consists of elaboration of these units in an appropriate order. Note
16699 that the default wide character encoding method for standard Text_IO
16700 files is always set to Brackets if this switch is set (you can use
16702 @code{-Wx} to override this default).
16705 @node Command-Line Access,Search Paths for gnatbind,Switches for gnatbind,Binding with gnatbind
16706 @anchor{gnat_ugn/building_executable_programs_with_gnat id42}@anchor{12e}@anchor{gnat_ugn/building_executable_programs_with_gnat command-line-access}@anchor{12f}
16707 @subsection Command-Line Access
16710 The package @code{Ada.Command_Line} provides access to the command-line
16711 arguments and program name. In order for this interface to operate
16712 correctly, the two variables
16723 are declared in one of the GNAT library routines. These variables must
16724 be set from the actual @code{argc} and @code{argv} values passed to the
16725 main program. With no @emph{n} present, @code{gnatbind}
16726 generates the C main program to automatically set these variables.
16727 If the @emph{n} switch is used, there is no automatic way to
16728 set these variables. If they are not set, the procedures in
16729 @code{Ada.Command_Line} will not be available, and any attempt to use
16730 them will raise @code{Constraint_Error}. If command line access is
16731 required, your main program must set @code{gnat_argc} and
16732 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
16735 @node Search Paths for gnatbind,Examples of gnatbind Usage,Command-Line Access,Binding with gnatbind
16736 @anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-for-gnatbind}@anchor{8c}@anchor{gnat_ugn/building_executable_programs_with_gnat id43}@anchor{130}
16737 @subsection Search Paths for @code{gnatbind}
16740 The binder takes the name of an ALI file as its argument and needs to
16741 locate source files as well as other ALI files to verify object consistency.
16743 For source files, it follows exactly the same search rules as @code{gcc}
16744 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}). For ALI files the
16745 directories searched are:
16751 The directory containing the ALI file named in the command line, unless
16752 the switch @code{-I-} is specified.
16755 All directories specified by @code{-I}
16756 switches on the @code{gnatbind}
16757 command line, in the order given.
16759 @geindex ADA_PRJ_OBJECTS_FILE
16762 Each of the directories listed in the text file whose name is given
16764 @geindex ADA_PRJ_OBJECTS_FILE
16765 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16766 @code{ADA_PRJ_OBJECTS_FILE} environment variable.
16768 @geindex ADA_PRJ_OBJECTS_FILE
16769 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16770 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the gnat
16771 driver when project files are used. It should not normally be set
16774 @geindex ADA_OBJECTS_PATH
16777 Each of the directories listed in the value of the
16778 @geindex ADA_OBJECTS_PATH
16779 @geindex environment variable; ADA_OBJECTS_PATH
16780 @code{ADA_OBJECTS_PATH} environment variable.
16781 Construct this value
16784 @geindex environment variable; PATH
16785 @code{PATH} environment variable: a list of directory
16786 names separated by colons (semicolons when working with the NT version
16790 The content of the @code{ada_object_path} file which is part of the GNAT
16791 installation tree and is used to store standard libraries such as the
16792 GNAT Run-Time Library (RTL) unless the switch @code{-nostdlib} is
16793 specified. See @ref{87,,Installing a library}
16796 @geindex -I (gnatbind)
16798 @geindex -aI (gnatbind)
16800 @geindex -aO (gnatbind)
16802 In the binder the switch @code{-I}
16803 is used to specify both source and
16804 library file paths. Use @code{-aI}
16805 instead if you want to specify
16806 source paths only, and @code{-aO}
16807 if you want to specify library paths
16808 only. This means that for the binder
16809 @code{-I@emph{dir}} is equivalent to
16810 @code{-aI@emph{dir}}
16811 @code{-aO`@emph{dir}}.
16812 The binder generates the bind file (a C language source file) in the
16813 current working directory.
16819 @geindex Interfaces
16823 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
16824 children make up the GNAT Run-Time Library, together with the package
16825 GNAT and its children, which contain a set of useful additional
16826 library functions provided by GNAT. The sources for these units are
16827 needed by the compiler and are kept together in one directory. The ALI
16828 files and object files generated by compiling the RTL are needed by the
16829 binder and the linker and are kept together in one directory, typically
16830 different from the directory containing the sources. In a normal
16831 installation, you need not specify these directory names when compiling
16832 or binding. Either the environment variables or the built-in defaults
16833 cause these files to be found.
16835 Besides simplifying access to the RTL, a major use of search paths is
16836 in compiling sources from multiple directories. This can make
16837 development environments much more flexible.
16839 @node Examples of gnatbind Usage,,Search Paths for gnatbind,Binding with gnatbind
16840 @anchor{gnat_ugn/building_executable_programs_with_gnat id44}@anchor{131}@anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatbind-usage}@anchor{132}
16841 @subsection Examples of @code{gnatbind} Usage
16844 Here are some examples of @code{gnatbind} invovations:
16852 The main program @code{Hello} (source program in @code{hello.adb}) is
16853 bound using the standard switch settings. The generated main program is
16854 @code{b~hello.adb}. This is the normal, default use of the binder.
16857 gnatbind hello -o mainprog.adb
16860 The main program @code{Hello} (source program in @code{hello.adb}) is
16861 bound using the standard switch settings. The generated main program is
16862 @code{mainprog.adb} with the associated spec in
16863 @code{mainprog.ads}. Note that you must specify the body here not the
16864 spec. Note that if this option is used, then linking must be done manually,
16865 since gnatlink will not be able to find the generated file.
16868 @node Linking with gnatlink,Using the GNU make Utility,Binding with gnatbind,Building Executable Programs with GNAT
16869 @anchor{gnat_ugn/building_executable_programs_with_gnat id45}@anchor{133}@anchor{gnat_ugn/building_executable_programs_with_gnat linking-with-gnatlink}@anchor{1e}
16870 @section Linking with @code{gnatlink}
16875 This chapter discusses @code{gnatlink}, a tool that links
16876 an Ada program and builds an executable file. This utility
16877 invokes the system linker (via the @code{gcc} command)
16878 with a correct list of object files and library references.
16879 @code{gnatlink} automatically determines the list of files and
16880 references for the Ada part of a program. It uses the binder file
16881 generated by the @code{gnatbind} to determine this list.
16884 * Running gnatlink::
16885 * Switches for gnatlink::
16889 @node Running gnatlink,Switches for gnatlink,,Linking with gnatlink
16890 @anchor{gnat_ugn/building_executable_programs_with_gnat id46}@anchor{134}@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatlink}@anchor{135}
16891 @subsection Running @code{gnatlink}
16894 The form of the @code{gnatlink} command is
16897 $ gnatlink [ switches ] mainprog [.ali]
16898 [ non-Ada objects ] [ linker options ]
16901 The arguments of @code{gnatlink} (switches, main @code{ALI} file,
16903 or linker options) may be in any order, provided that no non-Ada object may
16904 be mistaken for a main @code{ALI} file.
16905 Any file name @code{F} without the @code{.ali}
16906 extension will be taken as the main @code{ALI} file if a file exists
16907 whose name is the concatenation of @code{F} and @code{.ali}.
16909 @code{mainprog.ali} references the ALI file of the main program.
16910 The @code{.ali} extension of this file can be omitted. From this
16911 reference, @code{gnatlink} locates the corresponding binder file
16912 @code{b~mainprog.adb} and, using the information in this file along
16913 with the list of non-Ada objects and linker options, constructs a
16914 linker command file to create the executable.
16916 The arguments other than the @code{gnatlink} switches and the main
16917 @code{ALI} file are passed to the linker uninterpreted.
16918 They typically include the names of
16919 object files for units written in other languages than Ada and any library
16920 references required to resolve references in any of these foreign language
16921 units, or in @code{Import} pragmas in any Ada units.
16923 @code{linker options} is an optional list of linker specific
16925 The default linker called by gnatlink is @code{gcc} which in
16926 turn calls the appropriate system linker.
16928 One useful option for the linker is @code{-s}: it reduces the size of the
16929 executable by removing all symbol table and relocation information from the
16932 Standard options for the linker such as @code{-lmy_lib} or
16933 @code{-Ldir} can be added as is.
16934 For options that are not recognized by
16935 @code{gcc} as linker options, use the @code{gcc} switches
16936 @code{-Xlinker} or @code{-Wl,}.
16938 Refer to the GCC documentation for
16941 Here is an example showing how to generate a linker map:
16944 $ gnatlink my_prog -Wl,-Map,MAPFILE
16947 Using @code{linker options} it is possible to set the program stack and
16949 See @ref{136,,Setting Stack Size from gnatlink} and
16950 @ref{137,,Setting Heap Size from gnatlink}.
16952 @code{gnatlink} determines the list of objects required by the Ada
16953 program and prepends them to the list of objects passed to the linker.
16954 @code{gnatlink} also gathers any arguments set by the use of
16955 @code{pragma Linker_Options} and adds them to the list of arguments
16956 presented to the linker.
16958 @node Switches for gnatlink,,Running gnatlink,Linking with gnatlink
16959 @anchor{gnat_ugn/building_executable_programs_with_gnat id47}@anchor{138}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatlink}@anchor{139}
16960 @subsection Switches for @code{gnatlink}
16963 The following switches are available with the @code{gnatlink} utility:
16965 @geindex --version (gnatlink)
16970 @item @code{--version}
16972 Display Copyright and version, then exit disregarding all other options.
16975 @geindex --help (gnatlink)
16980 @item @code{--help}
16982 If @code{--version} was not used, display usage, then exit disregarding
16986 @geindex Command line length
16988 @geindex -f (gnatlink)
16995 On some targets, the command line length is limited, and @code{gnatlink}
16996 will generate a separate file for the linker if the list of object files
16998 The @code{-f} switch forces this file
16999 to be generated even if
17000 the limit is not exceeded. This is useful in some cases to deal with
17001 special situations where the command line length is exceeded.
17004 @geindex Debugging information
17007 @geindex -g (gnatlink)
17014 The option to include debugging information causes the Ada bind file (in
17015 other words, @code{b~mainprog.adb}) to be compiled with @code{-g}.
17016 In addition, the binder does not delete the @code{b~mainprog.adb},
17017 @code{b~mainprog.o} and @code{b~mainprog.ali} files.
17018 Without @code{-g}, the binder removes these files by default.
17021 @geindex -n (gnatlink)
17028 Do not compile the file generated by the binder. This may be used when
17029 a link is rerun with different options, but there is no need to recompile
17033 @geindex -v (gnatlink)
17040 Verbose mode. Causes additional information to be output, including a full
17041 list of the included object files.
17042 This switch option is most useful when you want
17043 to see what set of object files are being used in the link step.
17046 @geindex -v -v (gnatlink)
17053 Very verbose mode. Requests that the compiler operate in verbose mode when
17054 it compiles the binder file, and that the system linker run in verbose mode.
17057 @geindex -o (gnatlink)
17062 @item @code{-o @emph{exec-name}}
17064 @code{exec-name} specifies an alternate name for the generated
17065 executable program. If this switch is omitted, the executable has the same
17066 name as the main unit. For example, @code{gnatlink try.ali} creates
17067 an executable called @code{try}.
17070 @geindex -B (gnatlink)
17075 @item @code{-B@emph{dir}}
17077 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
17078 from @code{dir} instead of the default location. Only use this switch
17079 when multiple versions of the GNAT compiler are available.
17080 See the @code{Directory Options} section in @cite{The_GNU_Compiler_Collection}
17081 for further details. You would normally use the @code{-b} or
17082 @code{-V} switch instead.
17085 @geindex -M (gnatlink)
17092 When linking an executable, create a map file. The name of the map file
17093 has the same name as the executable with extension ".map".
17096 @geindex -M= (gnatlink)
17101 @item @code{-M=@emph{mapfile}}
17103 When linking an executable, create a map file. The name of the map file is
17107 @geindex --GCC=compiler_name (gnatlink)
17112 @item @code{--GCC=@emph{compiler_name}}
17114 Program used for compiling the binder file. The default is
17115 @code{gcc}. You need to use quotes around @code{compiler_name} if
17116 @code{compiler_name} contains spaces or other separator characters.
17117 As an example @code{--GCC="foo -x -y"} will instruct @code{gnatlink} to
17118 use @code{foo -x -y} as your compiler. Note that switch @code{-c} is always
17119 inserted after your command name. Thus in the above example the compiler
17120 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
17121 A limitation of this syntax is that the name and path name of the executable
17122 itself must not include any embedded spaces. If the compiler executable is
17123 different from the default one (gcc or <prefix>-gcc), then the back-end
17124 switches in the ALI file are not used to compile the binder generated source.
17125 For example, this is the case with @code{--GCC="foo -x -y"}. But the back end
17126 switches will be used for @code{--GCC="gcc -gnatv"}. If several
17127 @code{--GCC=compiler_name} are used, only the last @code{compiler_name}
17128 is taken into account. However, all the additional switches are also taken
17129 into account. Thus,
17130 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
17131 @code{--GCC="bar -x -y -z -t"}.
17134 @geindex --LINK= (gnatlink)
17139 @item @code{--LINK=@emph{name}}
17141 @code{name} is the name of the linker to be invoked. This is especially
17142 useful in mixed language programs since languages such as C++ require
17143 their own linker to be used. When this switch is omitted, the default
17144 name for the linker is @code{gcc}. When this switch is used, the
17145 specified linker is called instead of @code{gcc} with exactly the same
17146 parameters that would have been passed to @code{gcc} so if the desired
17147 linker requires different parameters it is necessary to use a wrapper
17148 script that massages the parameters before invoking the real linker. It
17149 may be useful to control the exact invocation by using the verbose
17153 @node Using the GNU make Utility,,Linking with gnatlink,Building Executable Programs with GNAT
17154 @anchor{gnat_ugn/building_executable_programs_with_gnat using-the-gnu-make-utility}@anchor{1f}@anchor{gnat_ugn/building_executable_programs_with_gnat id48}@anchor{13a}
17155 @section Using the GNU @code{make} Utility
17158 @geindex make (GNU)
17161 This chapter offers some examples of makefiles that solve specific
17162 problems. It does not explain how to write a makefile, nor does it try to replace the
17163 @code{gnatmake} utility (@ref{1b,,Building with gnatmake}).
17165 All the examples in this section are specific to the GNU version of
17166 make. Although @code{make} is a standard utility, and the basic language
17167 is the same, these examples use some advanced features found only in
17171 * Using gnatmake in a Makefile::
17172 * Automatically Creating a List of Directories::
17173 * Generating the Command Line Switches::
17174 * Overcoming Command Line Length Limits::
17178 @node Using gnatmake in a Makefile,Automatically Creating a List of Directories,,Using the GNU make Utility
17179 @anchor{gnat_ugn/building_executable_programs_with_gnat using-gnatmake-in-a-makefile}@anchor{13b}@anchor{gnat_ugn/building_executable_programs_with_gnat id49}@anchor{13c}
17180 @subsection Using gnatmake in a Makefile
17183 @c index makefile (GNU make)
17185 Complex project organizations can be handled in a very powerful way by
17186 using GNU make combined with gnatmake. For instance, here is a Makefile
17187 which allows you to build each subsystem of a big project into a separate
17188 shared library. Such a makefile allows you to significantly reduce the link
17189 time of very big applications while maintaining full coherence at
17190 each step of the build process.
17192 The list of dependencies are handled automatically by
17193 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
17194 the appropriate directories.
17196 Note that you should also read the example on how to automatically
17197 create the list of directories
17198 (@ref{13d,,Automatically Creating a List of Directories})
17199 which might help you in case your project has a lot of subdirectories.
17202 ## This Makefile is intended to be used with the following directory
17204 ## - The sources are split into a series of csc (computer software components)
17205 ## Each of these csc is put in its own directory.
17206 ## Their name are referenced by the directory names.
17207 ## They will be compiled into shared library (although this would also work
17208 ## with static libraries
17209 ## - The main program (and possibly other packages that do not belong to any
17210 ## csc is put in the top level directory (where the Makefile is).
17211 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
17212 ## \\_ second_csc (sources) __ lib (will contain the library)
17214 ## Although this Makefile is build for shared library, it is easy to modify
17215 ## to build partial link objects instead (modify the lines with -shared and
17218 ## With this makefile, you can change any file in the system or add any new
17219 ## file, and everything will be recompiled correctly (only the relevant shared
17220 ## objects will be recompiled, and the main program will be re-linked).
17222 # The list of computer software component for your project. This might be
17223 # generated automatically.
17226 # Name of the main program (no extension)
17229 # If we need to build objects with -fPIC, uncomment the following line
17232 # The following variable should give the directory containing libgnat.so
17233 # You can get this directory through 'gnatls -v'. This is usually the last
17234 # directory in the Object_Path.
17237 # The directories for the libraries
17238 # (This macro expands the list of CSC to the list of shared libraries, you
17239 # could simply use the expanded form:
17240 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
17241 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
17243 $@{MAIN@}: objects $@{LIB_DIR@}
17244 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
17245 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
17248 # recompile the sources
17249 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
17251 # Note: In a future version of GNAT, the following commands will be simplified
17252 # by a new tool, gnatmlib
17254 mkdir -p $@{dir $@@ @}
17255 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
17256 cd $@{dir $@@ @} && cp -f ../*.ali .
17258 # The dependencies for the modules
17259 # Note that we have to force the expansion of *.o, since in some cases
17260 # make won't be able to do it itself.
17261 aa/lib/libaa.so: $@{wildcard aa/*.o@}
17262 bb/lib/libbb.so: $@{wildcard bb/*.o@}
17263 cc/lib/libcc.so: $@{wildcard cc/*.o@}
17265 # Make sure all of the shared libraries are in the path before starting the
17268 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
17271 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
17272 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
17273 $@{RM@} $@{CSC_LIST:%=%/*.o@}
17274 $@{RM@} *.o *.ali $@{MAIN@}
17277 @node Automatically Creating a List of Directories,Generating the Command Line Switches,Using gnatmake in a Makefile,Using the GNU make Utility
17278 @anchor{gnat_ugn/building_executable_programs_with_gnat id50}@anchor{13e}@anchor{gnat_ugn/building_executable_programs_with_gnat automatically-creating-a-list-of-directories}@anchor{13d}
17279 @subsection Automatically Creating a List of Directories
17282 In most makefiles, you will have to specify a list of directories, and
17283 store it in a variable. For small projects, it is often easier to
17284 specify each of them by hand, since you then have full control over what
17285 is the proper order for these directories, which ones should be
17288 However, in larger projects, which might involve hundreds of
17289 subdirectories, it might be more convenient to generate this list
17292 The example below presents two methods. The first one, although less
17293 general, gives you more control over the list. It involves wildcard
17294 characters, that are automatically expanded by @code{make}. Its
17295 shortcoming is that you need to explicitly specify some of the
17296 organization of your project, such as for instance the directory tree
17297 depth, whether some directories are found in a separate tree, etc.
17299 The second method is the most general one. It requires an external
17300 program, called @code{find}, which is standard on all Unix systems. All
17301 the directories found under a given root directory will be added to the
17305 # The examples below are based on the following directory hierarchy:
17306 # All the directories can contain any number of files
17307 # ROOT_DIRECTORY -> a -> aa -> aaa
17310 # -> b -> ba -> baa
17313 # This Makefile creates a variable called DIRS, that can be reused any time
17314 # you need this list (see the other examples in this section)
17316 # The root of your project's directory hierarchy
17320 # First method: specify explicitly the list of directories
17321 # This allows you to specify any subset of all the directories you need.
17324 DIRS := a/aa/ a/ab/ b/ba/
17327 # Second method: use wildcards
17328 # Note that the argument(s) to wildcard below should end with a '/'.
17329 # Since wildcards also return file names, we have to filter them out
17330 # to avoid duplicate directory names.
17331 # We thus use make's `@w{`}dir`@w{`} and `@w{`}sort`@w{`} functions.
17332 # It sets DIRs to the following value (note that the directories aaa and baa
17333 # are not given, unless you change the arguments to wildcard).
17334 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
17337 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
17338 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
17341 # Third method: use an external program
17342 # This command is much faster if run on local disks, avoiding NFS slowdowns.
17343 # This is the most complete command: it sets DIRs to the following value:
17344 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
17347 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
17350 @node Generating the Command Line Switches,Overcoming Command Line Length Limits,Automatically Creating a List of Directories,Using the GNU make Utility
17351 @anchor{gnat_ugn/building_executable_programs_with_gnat id51}@anchor{13f}@anchor{gnat_ugn/building_executable_programs_with_gnat generating-the-command-line-switches}@anchor{140}
17352 @subsection Generating the Command Line Switches
17355 Once you have created the list of directories as explained in the
17356 previous section (@ref{13d,,Automatically Creating a List of Directories}),
17357 you can easily generate the command line arguments to pass to gnatmake.
17359 For the sake of completeness, this example assumes that the source path
17360 is not the same as the object path, and that you have two separate lists
17364 # see "Automatically creating a list of directories" to create
17369 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
17370 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
17373 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
17376 @node Overcoming Command Line Length Limits,,Generating the Command Line Switches,Using the GNU make Utility
17377 @anchor{gnat_ugn/building_executable_programs_with_gnat overcoming-command-line-length-limits}@anchor{141}@anchor{gnat_ugn/building_executable_programs_with_gnat id52}@anchor{142}
17378 @subsection Overcoming Command Line Length Limits
17381 One problem that might be encountered on big projects is that many
17382 operating systems limit the length of the command line. It is thus hard to give
17383 gnatmake the list of source and object directories.
17385 This example shows how you can set up environment variables, which will
17386 make @code{gnatmake} behave exactly as if the directories had been
17387 specified on the command line, but have a much higher length limit (or
17388 even none on most systems).
17390 It assumes that you have created a list of directories in your Makefile,
17391 using one of the methods presented in
17392 @ref{13d,,Automatically Creating a List of Directories}.
17393 For the sake of completeness, we assume that the object
17394 path (where the ALI files are found) is different from the sources patch.
17396 Note a small trick in the Makefile below: for efficiency reasons, we
17397 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
17398 expanded immediately by @code{make}. This way we overcome the standard
17399 make behavior which is to expand the variables only when they are
17402 On Windows, if you are using the standard Windows command shell, you must
17403 replace colons with semicolons in the assignments to these variables.
17406 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH.
17407 # This is the same thing as putting the -I arguments on the command line.
17408 # (the equivalent of using -aI on the command line would be to define
17409 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH).
17410 # You can of course have different values for these variables.
17412 # Note also that we need to keep the previous values of these variables, since
17413 # they might have been set before running 'make' to specify where the GNAT
17414 # library is installed.
17416 # see "Automatically creating a list of directories" to create these
17422 space:=$@{empty@} $@{empty@}
17423 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
17424 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
17425 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
17426 ADA_OBJECTS_PATH += $@{OBJECT_LIST@}
17427 export ADA_INCLUDE_PATH
17428 export ADA_OBJECTS_PATH
17434 @node GNAT Utility Programs,GNAT and Program Execution,Building Executable Programs with GNAT,Top
17435 @anchor{gnat_ugn/gnat_utility_programs doc}@anchor{143}@anchor{gnat_ugn/gnat_utility_programs gnat-utility-programs}@anchor{b}@anchor{gnat_ugn/gnat_utility_programs id1}@anchor{144}
17436 @chapter GNAT Utility Programs
17439 This chapter describes a number of utility programs:
17446 @ref{20,,The File Cleanup Utility gnatclean}
17449 @ref{21,,The GNAT Library Browser gnatls}
17452 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
17455 @ref{23,,The Ada to HTML Converter gnathtml}
17458 Other GNAT utilities are described elsewhere in this manual:
17464 @ref{59,,Handling Arbitrary File Naming Conventions with gnatname}
17467 @ref{63,,File Name Krunching with gnatkr}
17470 @ref{36,,Renaming Files with gnatchop}
17473 @ref{17,,Preprocessing with gnatprep}
17477 * The File Cleanup Utility gnatclean::
17478 * The GNAT Library Browser gnatls::
17479 * The Cross-Referencing Tools gnatxref and gnatfind::
17480 * The Ada to HTML Converter gnathtml::
17484 @node The File Cleanup Utility gnatclean,The GNAT Library Browser gnatls,,GNAT Utility Programs
17485 @anchor{gnat_ugn/gnat_utility_programs id2}@anchor{145}@anchor{gnat_ugn/gnat_utility_programs the-file-cleanup-utility-gnatclean}@anchor{20}
17486 @section The File Cleanup Utility @code{gnatclean}
17489 @geindex File cleanup tool
17493 @code{gnatclean} is a tool that allows the deletion of files produced by the
17494 compiler, binder and linker, including ALI files, object files, tree files,
17495 expanded source files, library files, interface copy source files, binder
17496 generated files and executable files.
17499 * Running gnatclean::
17500 * Switches for gnatclean::
17504 @node Running gnatclean,Switches for gnatclean,,The File Cleanup Utility gnatclean
17505 @anchor{gnat_ugn/gnat_utility_programs running-gnatclean}@anchor{146}@anchor{gnat_ugn/gnat_utility_programs id3}@anchor{147}
17506 @subsection Running @code{gnatclean}
17509 The @code{gnatclean} command has the form:
17514 $ gnatclean switches names
17518 where @code{names} is a list of source file names. Suffixes @code{.ads} and
17519 @code{adb} may be omitted. If a project file is specified using switch
17520 @code{-P}, then @code{names} may be completely omitted.
17522 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
17523 if switch @code{-c} is not specified, by the binder and
17524 the linker. In informative-only mode, specified by switch
17525 @code{-n}, the list of files that would have been deleted in
17526 normal mode is listed, but no file is actually deleted.
17528 @node Switches for gnatclean,,Running gnatclean,The File Cleanup Utility gnatclean
17529 @anchor{gnat_ugn/gnat_utility_programs id4}@anchor{148}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatclean}@anchor{149}
17530 @subsection Switches for @code{gnatclean}
17533 @code{gnatclean} recognizes the following switches:
17535 @geindex --version (gnatclean)
17540 @item @code{--version}
17542 Display copyright and version, then exit disregarding all other options.
17545 @geindex --help (gnatclean)
17550 @item @code{--help}
17552 If @code{--version} was not used, display usage, then exit disregarding
17555 @item @code{--subdirs=@emph{subdir}}
17557 Actual object directory of each project file is the subdirectory subdir of the
17558 object directory specified or defaulted in the project file.
17560 @item @code{--unchecked-shared-lib-imports}
17562 By default, shared library projects are not allowed to import static library
17563 projects. When this switch is used on the command line, this restriction is
17567 @geindex -c (gnatclean)
17574 Only attempt to delete the files produced by the compiler, not those produced
17575 by the binder or the linker. The files that are not to be deleted are library
17576 files, interface copy files, binder generated files and executable files.
17579 @geindex -D (gnatclean)
17584 @item @code{-D @emph{dir}}
17586 Indicate that ALI and object files should normally be found in directory @code{dir}.
17589 @geindex -F (gnatclean)
17596 When using project files, if some errors or warnings are detected during
17597 parsing and verbose mode is not in effect (no use of switch
17598 -v), then error lines start with the full path name of the project
17599 file, rather than its simple file name.
17602 @geindex -h (gnatclean)
17609 Output a message explaining the usage of @code{gnatclean}.
17612 @geindex -n (gnatclean)
17619 Informative-only mode. Do not delete any files. Output the list of the files
17620 that would have been deleted if this switch was not specified.
17623 @geindex -P (gnatclean)
17628 @item @code{-P@emph{project}}
17630 Use project file @code{project}. Only one such switch can be used.
17631 When cleaning a project file, the files produced by the compilation of the
17632 immediate sources or inherited sources of the project files are to be
17633 deleted. This is not depending on the presence or not of executable names
17634 on the command line.
17637 @geindex -q (gnatclean)
17644 Quiet output. If there are no errors, do not output anything, except in
17645 verbose mode (switch -v) or in informative-only mode
17649 @geindex -r (gnatclean)
17656 When a project file is specified (using switch -P),
17657 clean all imported and extended project files, recursively. If this switch
17658 is not specified, only the files related to the main project file are to be
17659 deleted. This switch has no effect if no project file is specified.
17662 @geindex -v (gnatclean)
17672 @geindex -vP (gnatclean)
17677 @item @code{-vP@emph{x}}
17679 Indicates the verbosity of the parsing of GNAT project files.
17680 @ref{de,,Switches Related to Project Files}.
17683 @geindex -X (gnatclean)
17688 @item @code{-X@emph{name}=@emph{value}}
17690 Indicates that external variable @code{name} has the value @code{value}.
17691 The Project Manager will use this value for occurrences of
17692 @code{external(name)} when parsing the project file.
17693 See @ref{de,,Switches Related to Project Files}.
17696 @geindex -aO (gnatclean)
17701 @item @code{-aO@emph{dir}}
17703 When searching for ALI and object files, look in directory @code{dir}.
17706 @geindex -I (gnatclean)
17711 @item @code{-I@emph{dir}}
17713 Equivalent to @code{-aO@emph{dir}}.
17716 @geindex -I- (gnatclean)
17718 @geindex Source files
17719 @geindex suppressing search
17726 Do not look for ALI or object files in the directory
17727 where @code{gnatclean} was invoked.
17730 @node The GNAT Library Browser gnatls,The Cross-Referencing Tools gnatxref and gnatfind,The File Cleanup Utility gnatclean,GNAT Utility Programs
17731 @anchor{gnat_ugn/gnat_utility_programs the-gnat-library-browser-gnatls}@anchor{21}@anchor{gnat_ugn/gnat_utility_programs id5}@anchor{14a}
17732 @section The GNAT Library Browser @code{gnatls}
17735 @geindex Library browser
17739 @code{gnatls} is a tool that outputs information about compiled
17740 units. It gives the relationship between objects, unit names and source
17741 files. It can also be used to check the source dependencies of a unit
17742 as well as various characteristics.
17746 * Switches for gnatls::
17747 * Example of gnatls Usage::
17751 @node Running gnatls,Switches for gnatls,,The GNAT Library Browser gnatls
17752 @anchor{gnat_ugn/gnat_utility_programs id6}@anchor{14b}@anchor{gnat_ugn/gnat_utility_programs running-gnatls}@anchor{14c}
17753 @subsection Running @code{gnatls}
17756 The @code{gnatls} command has the form
17761 $ gnatls switches object_or_ali_file
17765 The main argument is the list of object or @code{ali} files
17766 (see @ref{42,,The Ada Library Information Files})
17767 for which information is requested.
17769 In normal mode, without additional option, @code{gnatls} produces a
17770 four-column listing. Each line represents information for a specific
17771 object. The first column gives the full path of the object, the second
17772 column gives the name of the principal unit in this object, the third
17773 column gives the status of the source and the fourth column gives the
17774 full path of the source representing this unit.
17775 Here is a simple example of use:
17781 ./demo1.o demo1 DIF demo1.adb
17782 ./demo2.o demo2 OK demo2.adb
17783 ./hello.o h1 OK hello.adb
17784 ./instr-child.o instr.child MOK instr-child.adb
17785 ./instr.o instr OK instr.adb
17786 ./tef.o tef DIF tef.adb
17787 ./text_io_example.o text_io_example OK text_io_example.adb
17788 ./tgef.o tgef DIF tgef.adb
17792 The first line can be interpreted as follows: the main unit which is
17794 object file @code{demo1.o} is demo1, whose main source is in
17795 @code{demo1.adb}. Furthermore, the version of the source used for the
17796 compilation of demo1 has been modified (DIF). Each source file has a status
17797 qualifier which can be:
17802 @item @emph{OK (unchanged)}
17804 The version of the source file used for the compilation of the
17805 specified unit corresponds exactly to the actual source file.
17807 @item @emph{MOK (slightly modified)}
17809 The version of the source file used for the compilation of the
17810 specified unit differs from the actual source file but not enough to
17811 require recompilation. If you use gnatmake with the option
17812 @code{-m} (minimal recompilation), a file marked
17813 MOK will not be recompiled.
17815 @item @emph{DIF (modified)}
17817 No version of the source found on the path corresponds to the source
17818 used to build this object.
17820 @item @emph{??? (file not found)}
17822 No source file was found for this unit.
17824 @item @emph{HID (hidden, unchanged version not first on PATH)}
17826 The version of the source that corresponds exactly to the source used
17827 for compilation has been found on the path but it is hidden by another
17828 version of the same source that has been modified.
17831 @node Switches for gnatls,Example of gnatls Usage,Running gnatls,The GNAT Library Browser gnatls
17832 @anchor{gnat_ugn/gnat_utility_programs id7}@anchor{14d}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatls}@anchor{14e}
17833 @subsection Switches for @code{gnatls}
17836 @code{gnatls} recognizes the following switches:
17838 @geindex --version (gnatls)
17843 @item @code{--version}
17845 Display copyright and version, then exit disregarding all other options.
17848 @geindex --help (gnatls)
17853 @item @code{--help}
17855 If @code{--version} was not used, display usage, then exit disregarding
17859 @geindex -a (gnatls)
17866 Consider all units, including those of the predefined Ada library.
17867 Especially useful with @code{-d}.
17870 @geindex -d (gnatls)
17877 List sources from which specified units depend on.
17880 @geindex -h (gnatls)
17887 Output the list of options.
17890 @geindex -o (gnatls)
17897 Only output information about object files.
17900 @geindex -s (gnatls)
17907 Only output information about source files.
17910 @geindex -u (gnatls)
17917 Only output information about compilation units.
17920 @geindex -files (gnatls)
17925 @item @code{-files=@emph{file}}
17927 Take as arguments the files listed in text file @code{file}.
17928 Text file @code{file} may contain empty lines that are ignored.
17929 Each nonempty line should contain the name of an existing file.
17930 Several such switches may be specified simultaneously.
17933 @geindex -aO (gnatls)
17935 @geindex -aI (gnatls)
17937 @geindex -I (gnatls)
17939 @geindex -I- (gnatls)
17944 @item @code{-aO@emph{dir}}, @code{-aI@emph{dir}}, @code{-I@emph{dir}}, @code{-I-}, @code{-nostdinc}
17946 Source path manipulation. Same meaning as the equivalent @code{gnatmake}
17947 flags (@ref{dc,,Switches for gnatmake}).
17950 @geindex -aP (gnatls)
17955 @item @code{-aP@emph{dir}}
17957 Add @code{dir} at the beginning of the project search dir.
17960 @geindex --RTS (gnatls)
17965 @item @code{--RTS=@emph{rts-path}}
17967 Specifies the default location of the runtime library. Same meaning as the
17968 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
17971 @geindex -v (gnatls)
17978 Verbose mode. Output the complete source, object and project paths. Do not use
17979 the default column layout but instead use long format giving as much as
17980 information possible on each requested units, including special
17981 characteristics such as:
17987 @emph{Preelaborable}: The unit is preelaborable in the Ada sense.
17990 @emph{No_Elab_Code}: No elaboration code has been produced by the compiler for this unit.
17993 @emph{Pure}: The unit is pure in the Ada sense.
17996 @emph{Elaborate_Body}: The unit contains a pragma Elaborate_Body.
17999 @emph{Remote_Types}: The unit contains a pragma Remote_Types.
18002 @emph{Shared_Passive}: The unit contains a pragma Shared_Passive.
18005 @emph{Predefined}: This unit is part of the predefined environment and cannot be modified
18009 @emph{Remote_Call_Interface}: The unit contains a pragma Remote_Call_Interface.
18013 @node Example of gnatls Usage,,Switches for gnatls,The GNAT Library Browser gnatls
18014 @anchor{gnat_ugn/gnat_utility_programs id8}@anchor{14f}@anchor{gnat_ugn/gnat_utility_programs example-of-gnatls-usage}@anchor{150}
18015 @subsection Example of @code{gnatls} Usage
18018 Example of using the verbose switch. Note how the source and
18019 object paths are affected by the -I switch.
18024 $ gnatls -v -I.. demo1.o
18026 GNATLS 5.03w (20041123-34)
18027 Copyright 1997-2004 Free Software Foundation, Inc.
18029 Source Search Path:
18030 <Current_Directory>
18032 /home/comar/local/adainclude/
18034 Object Search Path:
18035 <Current_Directory>
18037 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18039 Project Search Path:
18040 <Current_Directory>
18041 /home/comar/local/lib/gnat/
18046 Kind => subprogram body
18047 Flags => No_Elab_Code
18048 Source => demo1.adb modified
18052 The following is an example of use of the dependency list.
18053 Note the use of the -s switch
18054 which gives a straight list of source files. This can be useful for
18055 building specialized scripts.
18060 $ gnatls -d demo2.o
18061 ./demo2.o demo2 OK demo2.adb
18067 $ gnatls -d -s -a demo1.o
18069 /home/comar/local/adainclude/ada.ads
18070 /home/comar/local/adainclude/a-finali.ads
18071 /home/comar/local/adainclude/a-filico.ads
18072 /home/comar/local/adainclude/a-stream.ads
18073 /home/comar/local/adainclude/a-tags.ads
18076 /home/comar/local/adainclude/gnat.ads
18077 /home/comar/local/adainclude/g-io.ads
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18093 @node The Cross-Referencing Tools gnatxref and gnatfind,The Ada to HTML Converter gnathtml,The GNAT Library Browser gnatls,GNAT Utility Programs
18094 @anchor{gnat_ugn/gnat_utility_programs the-cross-referencing-tools-gnatxref-and-gnatfind}@anchor{22}@anchor{gnat_ugn/gnat_utility_programs id9}@anchor{151}
18095 @section The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
18102 The compiler generates cross-referencing information (unless
18103 you set the @code{-gnatx} switch), which are saved in the @code{.ali} files.
18104 This information indicates where in the source each entity is declared and
18105 referenced. Note that entities in package Standard are not included, but
18106 entities in all other predefined units are included in the output.
18108 Before using any of these two tools, you need to compile successfully your
18109 application, so that GNAT gets a chance to generate the cross-referencing
18112 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
18113 information to provide the user with the capability to easily locate the
18114 declaration and references to an entity. These tools are quite similar,
18115 the difference being that @code{gnatfind} is intended for locating
18116 definitions and/or references to a specified entity or entities, whereas
18117 @code{gnatxref} is oriented to generating a full report of all
18120 To use these tools, you must not compile your application using the
18121 @code{-gnatx} switch on the @code{gnatmake} command line
18122 (see @ref{1b,,Building with gnatmake}). Otherwise, cross-referencing
18123 information will not be generated.
18126 * gnatxref Switches::
18127 * gnatfind Switches::
18128 * Configuration Files for gnatxref and gnatfind::
18129 * Regular Expressions in gnatfind and gnatxref::
18130 * Examples of gnatxref Usage::
18131 * Examples of gnatfind Usage::
18135 @node gnatxref Switches,gnatfind Switches,,The Cross-Referencing Tools gnatxref and gnatfind
18136 @anchor{gnat_ugn/gnat_utility_programs id10}@anchor{152}@anchor{gnat_ugn/gnat_utility_programs gnatxref-switches}@anchor{153}
18137 @subsection @code{gnatxref} Switches
18140 The command invocation for @code{gnatxref} is:
18145 $ gnatxref [ switches ] sourcefile1 [ sourcefile2 ... ]
18154 @item @code{sourcefile1} [, @code{sourcefile2} ...]
18156 identify the source files for which a report is to be generated. The
18157 @code{with}ed units will be processed too. You must provide at least one file.
18159 These file names are considered to be regular expressions, so for instance
18160 specifying @code{source*.adb} is the same as giving every file in the current
18161 directory whose name starts with @code{source} and whose extension is
18164 You shouldn't specify any directory name, just base names. @code{gnatxref}
18165 and @code{gnatfind} will be able to locate these files by themselves using
18166 the source path. If you specify directories, no result is produced.
18169 The following switches are available for @code{gnatxref}:
18171 @geindex --version (gnatxref)
18176 @item @code{--version}
18178 Display copyright and version, then exit disregarding all other options.
18181 @geindex --help (gnatxref)
18186 @item @code{--help}
18188 If @code{--version} was not used, display usage, then exit disregarding
18192 @geindex -a (gnatxref)
18199 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18200 the read-only files found in the library search path. Otherwise, these files
18201 will be ignored. This option can be used to protect Gnat sources or your own
18202 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18203 much faster, and their output much smaller. Read-only here refers to access
18204 or permissions status in the file system for the current user.
18207 @geindex -aIDIR (gnatxref)
18212 @item @code{-aI@emph{DIR}}
18214 When looking for source files also look in directory DIR. The order in which
18215 source file search is undertaken is the same as for @code{gnatmake}.
18218 @geindex -aODIR (gnatxref)
18223 @item @code{aO@emph{DIR}}
18225 When -searching for library and object files, look in directory
18226 DIR. The order in which library files are searched is the same as for
18230 @geindex -nostdinc (gnatxref)
18235 @item @code{-nostdinc}
18237 Do not look for sources in the system default directory.
18240 @geindex -nostdlib (gnatxref)
18245 @item @code{-nostdlib}
18247 Do not look for library files in the system default directory.
18250 @geindex --ext (gnatxref)
18255 @item @code{--ext=@emph{extension}}
18257 Specify an alternate ali file extension. The default is @code{ali} and other
18258 extensions (e.g. @code{gli} for C/C++ sources) may be specified via this switch.
18259 Note that if this switch overrides the default, only the new extension will
18263 @geindex --RTS (gnatxref)
18268 @item @code{--RTS=@emph{rts-path}}
18270 Specifies the default location of the runtime library. Same meaning as the
18271 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18274 @geindex -d (gnatxref)
18281 If this switch is set @code{gnatxref} will output the parent type
18282 reference for each matching derived types.
18285 @geindex -f (gnatxref)
18292 If this switch is set, the output file names will be preceded by their
18293 directory (if the file was found in the search path). If this switch is
18294 not set, the directory will not be printed.
18297 @geindex -g (gnatxref)
18304 If this switch is set, information is output only for library-level
18305 entities, ignoring local entities. The use of this switch may accelerate
18306 @code{gnatfind} and @code{gnatxref}.
18309 @geindex -IDIR (gnatxref)
18314 @item @code{-I@emph{DIR}}
18316 Equivalent to @code{-aODIR -aIDIR}.
18319 @geindex -pFILE (gnatxref)
18324 @item @code{-p@emph{FILE}}
18326 Specify a configuration file to use to list the source and object directories.
18328 If a file is specified, then the content of the source directory and object
18329 directory lines are added as if they had been specified respectively
18330 by @code{-aI} and @code{-aO}.
18332 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18333 of this configuration file.
18337 Output only unused symbols. This may be really useful if you give your
18338 main compilation unit on the command line, as @code{gnatxref} will then
18339 display every unused entity and 'with'ed package.
18343 Instead of producing the default output, @code{gnatxref} will generate a
18344 @code{tags} file that can be used by vi. For examples how to use this
18345 feature, see @ref{155,,Examples of gnatxref Usage}. The tags file is output
18346 to the standard output, thus you will have to redirect it to a file.
18349 All these switches may be in any order on the command line, and may even
18350 appear after the file names. They need not be separated by spaces, thus
18351 you can say @code{gnatxref -ag} instead of @code{gnatxref -a -g}.
18353 @node gnatfind Switches,Configuration Files for gnatxref and gnatfind,gnatxref Switches,The Cross-Referencing Tools gnatxref and gnatfind
18354 @anchor{gnat_ugn/gnat_utility_programs id11}@anchor{156}@anchor{gnat_ugn/gnat_utility_programs gnatfind-switches}@anchor{157}
18355 @subsection @code{gnatfind} Switches
18358 The command invocation for @code{gnatfind} is:
18363 $ gnatfind [ switches ] pattern[:sourcefile[:line[:column]]]
18368 with the following iterpretation of the command arguments:
18373 @item @emph{pattern}
18375 An entity will be output only if it matches the regular expression found
18376 in @emph{pattern}, see @ref{158,,Regular Expressions in gnatfind and gnatxref}.
18378 Omitting the pattern is equivalent to specifying @code{*}, which
18379 will match any entity. Note that if you do not provide a pattern, you
18380 have to provide both a sourcefile and a line.
18382 Entity names are given in Latin-1, with uppercase/lowercase equivalence
18383 for matching purposes. At the current time there is no support for
18384 8-bit codes other than Latin-1, or for wide characters in identifiers.
18386 @item @emph{sourcefile}
18388 @code{gnatfind} will look for references, bodies or declarations
18389 of symbols referenced in @code{sourcefile}, at line @code{line}
18390 and column @code{column}. See @ref{159,,Examples of gnatfind Usage}
18391 for syntax examples.
18395 A decimal integer identifying the line number containing
18396 the reference to the entity (or entities) to be located.
18398 @item @emph{column}
18400 A decimal integer identifying the exact location on the
18401 line of the first character of the identifier for the
18402 entity reference. Columns are numbered from 1.
18404 @item @emph{file1 file2 ...}
18406 The search will be restricted to these source files. If none are given, then
18407 the search will be conducted for every library file in the search path.
18408 These files must appear only after the pattern or sourcefile.
18410 These file names are considered to be regular expressions, so for instance
18411 specifying @code{source*.adb} is the same as giving every file in the current
18412 directory whose name starts with @code{source} and whose extension is
18415 The location of the spec of the entity will always be displayed, even if it
18416 isn't in one of @code{file1}, @code{file2}, ... The
18417 occurrences of the entity in the separate units of the ones given on the
18418 command line will also be displayed.
18420 Note that if you specify at least one file in this part, @code{gnatfind} may
18421 sometimes not be able to find the body of the subprograms.
18424 At least one of 'sourcefile' or 'pattern' has to be present on
18427 The following switches are available:
18429 @geindex --version (gnatfind)
18434 @item @code{--version}
18436 Display copyright and version, then exit disregarding all other options.
18439 @geindex --help (gnatfind)
18444 @item @code{--help}
18446 If @code{--version} was not used, display usage, then exit disregarding
18450 @geindex -a (gnatfind)
18457 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18458 the read-only files found in the library search path. Otherwise, these files
18459 will be ignored. This option can be used to protect Gnat sources or your own
18460 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18461 much faster, and their output much smaller. Read-only here refers to access
18462 or permission status in the file system for the current user.
18465 @geindex -aIDIR (gnatfind)
18470 @item @code{-aI@emph{DIR}}
18472 When looking for source files also look in directory DIR. The order in which
18473 source file search is undertaken is the same as for @code{gnatmake}.
18476 @geindex -aODIR (gnatfind)
18481 @item @code{-aO@emph{DIR}}
18483 When searching for library and object files, look in directory
18484 DIR. The order in which library files are searched is the same as for
18488 @geindex -nostdinc (gnatfind)
18493 @item @code{-nostdinc}
18495 Do not look for sources in the system default directory.
18498 @geindex -nostdlib (gnatfind)
18503 @item @code{-nostdlib}
18505 Do not look for library files in the system default directory.
18508 @geindex --ext (gnatfind)
18513 @item @code{--ext=@emph{extension}}
18515 Specify an alternate ali file extension. The default is @code{ali} and other
18516 extensions may be specified via this switch. Note that if this switch
18517 overrides the default, only the new extension will be considered.
18520 @geindex --RTS (gnatfind)
18525 @item @code{--RTS=@emph{rts-path}}
18527 Specifies the default location of the runtime library. Same meaning as the
18528 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18531 @geindex -d (gnatfind)
18538 If this switch is set, then @code{gnatfind} will output the parent type
18539 reference for each matching derived types.
18542 @geindex -e (gnatfind)
18549 By default, @code{gnatfind} accept the simple regular expression set for
18550 @code{pattern}. If this switch is set, then the pattern will be
18551 considered as full Unix-style regular expression.
18554 @geindex -f (gnatfind)
18561 If this switch is set, the output file names will be preceded by their
18562 directory (if the file was found in the search path). If this switch is
18563 not set, the directory will not be printed.
18566 @geindex -g (gnatfind)
18573 If this switch is set, information is output only for library-level
18574 entities, ignoring local entities. The use of this switch may accelerate
18575 @code{gnatfind} and @code{gnatxref}.
18578 @geindex -IDIR (gnatfind)
18583 @item @code{-I@emph{DIR}}
18585 Equivalent to @code{-aODIR -aIDIR}.
18588 @geindex -pFILE (gnatfind)
18593 @item @code{-p@emph{FILE}}
18595 Specify a configuration file to use to list the source and object directories.
18597 If a file is specified, then the content of the source directory and object
18598 directory lines are added as if they had been specified respectively
18599 by @code{-aI} and @code{-aO}.
18601 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18602 of this configuration file.
18605 @geindex -r (gnatfind)
18612 By default, @code{gnatfind} will output only the information about the
18613 declaration, body or type completion of the entities. If this switch is
18614 set, the @code{gnatfind} will locate every reference to the entities in
18615 the files specified on the command line (or in every file in the search
18616 path if no file is given on the command line).
18619 @geindex -s (gnatfind)
18626 If this switch is set, then @code{gnatfind} will output the content
18627 of the Ada source file lines were the entity was found.
18630 @geindex -t (gnatfind)
18637 If this switch is set, then @code{gnatfind} will output the type hierarchy for
18638 the specified type. It act like -d option but recursively from parent
18639 type to parent type. When this switch is set it is not possible to
18640 specify more than one file.
18643 All these switches may be in any order on the command line, and may even
18644 appear after the file names. They need not be separated by spaces, thus
18645 you can say @code{gnatxref -ag} instead of
18646 @code{gnatxref -a -g}.
18648 As stated previously, @code{gnatfind} will search in every directory in the
18649 search path. You can force it to look only in the current directory if
18650 you specify @code{*} at the end of the command line.
18652 @node Configuration Files for gnatxref and gnatfind,Regular Expressions in gnatfind and gnatxref,gnatfind Switches,The Cross-Referencing Tools gnatxref and gnatfind
18653 @anchor{gnat_ugn/gnat_utility_programs configuration-files-for-gnatxref-and-gnatfind}@anchor{154}@anchor{gnat_ugn/gnat_utility_programs id12}@anchor{15a}
18654 @subsection Configuration Files for @code{gnatxref} and @code{gnatfind}
18657 Configuration files are used by @code{gnatxref} and @code{gnatfind} to specify
18658 the list of source and object directories to consider. They can be
18659 specified via the @code{-p} switch.
18661 The following lines can be included, in any order in the file:
18670 @item @emph{src_dir=DIR}
18672 [default: @code{"./"}].
18673 Specifies a directory where to look for source files. Multiple @code{src_dir}
18674 lines can be specified and they will be searched in the order they
18682 @item @emph{obj_dir=DIR}
18684 [default: @code{"./"}].
18685 Specifies a directory where to look for object and library files. Multiple
18686 @code{obj_dir} lines can be specified, and they will be searched in the order
18691 Any other line will be silently ignored.
18693 @node Regular Expressions in gnatfind and gnatxref,Examples of gnatxref Usage,Configuration Files for gnatxref and gnatfind,The Cross-Referencing Tools gnatxref and gnatfind
18694 @anchor{gnat_ugn/gnat_utility_programs id13}@anchor{15b}@anchor{gnat_ugn/gnat_utility_programs regular-expressions-in-gnatfind-and-gnatxref}@anchor{158}
18695 @subsection Regular Expressions in @code{gnatfind} and @code{gnatxref}
18698 As specified in the section about @code{gnatfind}, the pattern can be a
18699 regular expression. Two kinds of regular expressions
18709 @item @emph{Globbing pattern}
18711 These are the most common regular expression. They are the same as are
18712 generally used in a Unix shell command line, or in a DOS session.
18714 Here is a more formal grammar:
18718 term ::= elmt -- matches elmt
18719 term ::= elmt elmt -- concatenation (elmt then elmt)
18720 term ::= * -- any string of 0 or more characters
18721 term ::= ? -- matches any character
18722 term ::= [char @{char@}] -- matches any character listed
18723 term ::= [char - char] -- matches any character in range
18731 @item @emph{Full regular expression}
18733 The second set of regular expressions is much more powerful. This is the
18734 type of regular expressions recognized by utilities such as @code{grep}.
18736 The following is the form of a regular expression, expressed in same BNF
18737 style as is found in the Ada Reference Manual:
18740 regexp ::= term @{| term@} -- alternation (term or term ...)
18742 term ::= item @{item@} -- concatenation (item then item)
18744 item ::= elmt -- match elmt
18745 item ::= elmt * -- zero or more elmt's
18746 item ::= elmt + -- one or more elmt's
18747 item ::= elmt ? -- matches elmt or nothing
18749 elmt ::= nschar -- matches given character
18750 elmt ::= [nschar @{nschar@}] -- matches any character listed
18751 elmt ::= [^ nschar @{nschar@}] -- matches any character not listed
18752 elmt ::= [char - char] -- matches chars in given range
18753 elmt ::= \\ char -- matches given character
18754 elmt ::= . -- matches any single character
18755 elmt ::= ( regexp ) -- parens used for grouping
18757 char ::= any character, including special characters
18758 nschar ::= any character except ()[].*+?^
18761 Here are a few examples:
18768 @item @code{abcde|fghi}
18770 will match any of the two strings @code{abcde} and @code{fghi},
18774 will match any string like @code{abd}, @code{abcd}, @code{abccd},
18775 @code{abcccd}, and so on,
18777 @item @code{[a-z]+}
18779 will match any string which has only lowercase characters in it (and at
18780 least one character.
18786 @node Examples of gnatxref Usage,Examples of gnatfind Usage,Regular Expressions in gnatfind and gnatxref,The Cross-Referencing Tools gnatxref and gnatfind
18787 @anchor{gnat_ugn/gnat_utility_programs examples-of-gnatxref-usage}@anchor{155}@anchor{gnat_ugn/gnat_utility_programs id14}@anchor{15c}
18788 @subsection Examples of @code{gnatxref} Usage
18793 * Using gnatxref with vi::
18797 @node General Usage,Using gnatxref with vi,,Examples of gnatxref Usage
18798 @anchor{gnat_ugn/gnat_utility_programs general-usage}@anchor{15d}
18799 @subsubsection General Usage
18802 For the following examples, we will consider the following units:
18810 3: procedure Foo (B : in Integer);
18817 1: package body Main is
18818 2: procedure Foo (B : in Integer) is
18829 2: procedure Print (B : Integer);
18834 The first thing to do is to recompile your application (for instance, in
18835 that case just by doing a @code{gnatmake main}, so that GNAT generates
18836 the cross-referencing information.
18837 You can then issue any of the following commands:
18845 @code{gnatxref main.adb}
18846 @code{gnatxref} generates cross-reference information for main.adb
18847 and every unit 'with'ed by main.adb.
18849 The output would be:
18857 Decl: main.ads 3:20
18858 Body: main.adb 2:20
18859 Ref: main.adb 4:13 5:13 6:19
18862 Ref: main.adb 6:8 7:8
18872 Decl: main.ads 3:15
18873 Body: main.adb 2:15
18876 Body: main.adb 1:14
18879 Ref: main.adb 6:12 7:12
18883 This shows that the entity @code{Main} is declared in main.ads, line 2, column 9,
18884 its body is in main.adb, line 1, column 14 and is not referenced any where.
18886 The entity @code{Print} is declared in @code{bar.ads}, line 2, column 15 and it
18887 is referenced in @code{main.adb}, line 6 column 12 and line 7 column 12.
18890 @code{gnatxref package1.adb package2.ads}
18891 @code{gnatxref} will generates cross-reference information for
18892 @code{package1.adb}, @code{package2.ads} and any other package @code{with}ed by any
18897 @node Using gnatxref with vi,,General Usage,Examples of gnatxref Usage
18898 @anchor{gnat_ugn/gnat_utility_programs using-gnatxref-with-vi}@anchor{15e}
18899 @subsubsection Using @code{gnatxref} with @code{vi}
18902 @code{gnatxref} can generate a tags file output, which can be used
18903 directly from @code{vi}. Note that the standard version of @code{vi}
18904 will not work properly with overloaded symbols. Consider using another
18905 free implementation of @code{vi}, such as @code{vim}.
18910 $ gnatxref -v gnatfind.adb > tags
18914 The following command will generate the tags file for @code{gnatfind} itself
18915 (if the sources are in the search path!):
18920 $ gnatxref -v gnatfind.adb > tags
18924 From @code{vi}, you can then use the command @code{:tag @emph{entity}}
18925 (replacing @code{entity} by whatever you are looking for), and vi will
18926 display a new file with the corresponding declaration of entity.
18928 @node Examples of gnatfind Usage,,Examples of gnatxref Usage,The Cross-Referencing Tools gnatxref and gnatfind
18929 @anchor{gnat_ugn/gnat_utility_programs id15}@anchor{15f}@anchor{gnat_ugn/gnat_utility_programs examples-of-gnatfind-usage}@anchor{159}
18930 @subsection Examples of @code{gnatfind} Usage
18937 @code{gnatfind -f xyz:main.adb}
18938 Find declarations for all entities xyz referenced at least once in
18939 main.adb. The references are search in every library file in the search
18942 The directories will be printed as well (as the @code{-f}
18945 The output will look like:
18950 directory/main.ads:106:14: xyz <= declaration
18951 directory/main.adb:24:10: xyz <= body
18952 directory/foo.ads:45:23: xyz <= declaration
18956 I.e., one of the entities xyz found in main.adb is declared at
18957 line 12 of main.ads (and its body is in main.adb), and another one is
18958 declared at line 45 of foo.ads
18961 @code{gnatfind -fs xyz:main.adb}
18962 This is the same command as the previous one, but @code{gnatfind} will
18963 display the content of the Ada source file lines.
18965 The output will look like:
18968 directory/main.ads:106:14: xyz <= declaration
18970 directory/main.adb:24:10: xyz <= body
18972 directory/foo.ads:45:23: xyz <= declaration
18976 This can make it easier to find exactly the location your are looking
18980 @code{gnatfind -r "*x*":main.ads:123 foo.adb}
18981 Find references to all entities containing an x that are
18982 referenced on line 123 of main.ads.
18983 The references will be searched only in main.ads and foo.adb.
18986 @code{gnatfind main.ads:123}
18987 Find declarations and bodies for all entities that are referenced on
18988 line 123 of main.ads.
18990 This is the same as @code{gnatfind "*":main.adb:123`}
18993 @code{gnatfind mydir/main.adb:123:45}
18994 Find the declaration for the entity referenced at column 45 in
18995 line 123 of file main.adb in directory mydir. Note that it
18996 is usual to omit the identifier name when the column is given,
18997 since the column position identifies a unique reference.
18999 The column has to be the beginning of the identifier, and should not
19000 point to any character in the middle of the identifier.
19003 @node The Ada to HTML Converter gnathtml,,The Cross-Referencing Tools gnatxref and gnatfind,GNAT Utility Programs
19004 @anchor{gnat_ugn/gnat_utility_programs the-ada-to-html-converter-gnathtml}@anchor{23}@anchor{gnat_ugn/gnat_utility_programs id16}@anchor{160}
19005 @section The Ada to HTML Converter @code{gnathtml}
19010 @code{gnathtml} is a Perl script that allows Ada source files to be browsed using
19011 standard Web browsers. For installation information, see @ref{161,,Installing gnathtml}.
19013 Ada reserved keywords are highlighted in a bold font and Ada comments in
19014 a blue font. Unless your program was compiled with the gcc @code{-gnatx}
19015 switch to suppress the generation of cross-referencing information, user
19016 defined variables and types will appear in a different color; you will
19017 be able to click on any identifier and go to its declaration.
19020 * Invoking gnathtml::
19021 * Installing gnathtml::
19025 @node Invoking gnathtml,Installing gnathtml,,The Ada to HTML Converter gnathtml
19026 @anchor{gnat_ugn/gnat_utility_programs invoking-gnathtml}@anchor{162}@anchor{gnat_ugn/gnat_utility_programs id17}@anchor{163}
19027 @subsection Invoking @code{gnathtml}
19030 The command line is as follows:
19035 $ perl gnathtml.pl [ switches ] ada-files
19039 You can specify as many Ada files as you want. @code{gnathtml} will generate
19040 an html file for every ada file, and a global file called @code{index.htm}.
19041 This file is an index of every identifier defined in the files.
19043 The following switches are available:
19045 @geindex -83 (gnathtml)
19052 Only the Ada 83 subset of keywords will be highlighted.
19055 @geindex -cc (gnathtml)
19060 @item @code{cc @emph{color}}
19062 This option allows you to change the color used for comments. The default
19063 value is green. The color argument can be any name accepted by html.
19066 @geindex -d (gnathtml)
19073 If the Ada files depend on some other files (for instance through
19074 @code{with} clauses, the latter files will also be converted to html.
19075 Only the files in the user project will be converted to html, not the files
19076 in the run-time library itself.
19079 @geindex -D (gnathtml)
19086 This command is the same as @code{-d} above, but @code{gnathtml} will
19087 also look for files in the run-time library, and generate html files for them.
19090 @geindex -ext (gnathtml)
19095 @item @code{ext @emph{extension}}
19097 This option allows you to change the extension of the generated HTML files.
19098 If you do not specify an extension, it will default to @code{htm}.
19101 @geindex -f (gnathtml)
19108 By default, gnathtml will generate html links only for global entities
19109 ('with'ed units, global variables and types,...). If you specify
19110 @code{-f} on the command line, then links will be generated for local
19114 @geindex -l (gnathtml)
19119 @item @code{l @emph{number}}
19121 If this switch is provided and @code{number} is not 0, then
19122 @code{gnathtml} will number the html files every @code{number} line.
19125 @geindex -I (gnathtml)
19130 @item @code{I @emph{dir}}
19132 Specify a directory to search for library files (@code{.ALI} files) and
19133 source files. You can provide several -I switches on the command line,
19134 and the directories will be parsed in the order of the command line.
19137 @geindex -o (gnathtml)
19142 @item @code{o @emph{dir}}
19144 Specify the output directory for html files. By default, gnathtml will
19145 saved the generated html files in a subdirectory named @code{html/}.
19148 @geindex -p (gnathtml)
19153 @item @code{p @emph{file}}
19155 If you are using Emacs and the most recent Emacs Ada mode, which provides
19156 a full Integrated Development Environment for compiling, checking,
19157 running and debugging applications, you may use @code{.gpr} files
19158 to give the directories where Emacs can find sources and object files.
19160 Using this switch, you can tell gnathtml to use these files.
19161 This allows you to get an html version of your application, even if it
19162 is spread over multiple directories.
19165 @geindex -sc (gnathtml)
19170 @item @code{sc @emph{color}}
19172 This switch allows you to change the color used for symbol
19174 The default value is red. The color argument can be any name accepted by html.
19177 @geindex -t (gnathtml)
19182 @item @code{t @emph{file}}
19184 This switch provides the name of a file. This file contains a list of
19185 file names to be converted, and the effect is exactly as though they had
19186 appeared explicitly on the command line. This
19187 is the recommended way to work around the command line length limit on some
19191 @node Installing gnathtml,,Invoking gnathtml,The Ada to HTML Converter gnathtml
19192 @anchor{gnat_ugn/gnat_utility_programs installing-gnathtml}@anchor{161}@anchor{gnat_ugn/gnat_utility_programs id18}@anchor{164}
19193 @subsection Installing @code{gnathtml}
19196 @code{Perl} needs to be installed on your machine to run this script.
19197 @code{Perl} is freely available for almost every architecture and
19198 operating system via the Internet.
19200 On Unix systems, you may want to modify the first line of the script
19201 @code{gnathtml}, to explicitly specify where Perl
19202 is located. The syntax of this line is:
19207 #!full_path_name_to_perl
19211 Alternatively, you may run the script using the following command line:
19216 $ perl gnathtml.pl [ switches ] files
19220 @c -- +---------------------------------------------------------------------+
19222 @c -- | The following sections are present only in the PRO and GPL editions |
19224 @c -- +---------------------------------------------------------------------+
19234 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
19236 @node GNAT and Program Execution,Platform-Specific Information,GNAT Utility Programs,Top
19237 @anchor{gnat_ugn/gnat_and_program_execution gnat-and-program-execution}@anchor{c}@anchor{gnat_ugn/gnat_and_program_execution doc}@anchor{165}@anchor{gnat_ugn/gnat_and_program_execution id1}@anchor{166}
19238 @chapter GNAT and Program Execution
19241 This chapter covers several topics:
19247 @ref{167,,Running and Debugging Ada Programs}
19250 @ref{25,,Profiling}
19253 @ref{168,,Improving Performance}
19256 @ref{169,,Overflow Check Handling in GNAT}
19259 @ref{16a,,Performing Dimensionality Analysis in GNAT}
19262 @ref{16b,,Stack Related Facilities}
19265 @ref{16c,,Memory Management Issues}
19269 * Running and Debugging Ada Programs::
19271 * Improving Performance::
19272 * Overflow Check Handling in GNAT::
19273 * Performing Dimensionality Analysis in GNAT::
19274 * Stack Related Facilities::
19275 * Memory Management Issues::
19279 @node Running and Debugging Ada Programs,Profiling,,GNAT and Program Execution
19280 @anchor{gnat_ugn/gnat_and_program_execution id2}@anchor{167}@anchor{gnat_ugn/gnat_and_program_execution running-and-debugging-ada-programs}@anchor{24}
19281 @section Running and Debugging Ada Programs
19286 This section discusses how to debug Ada programs.
19288 An incorrect Ada program may be handled in three ways by the GNAT compiler:
19294 The illegality may be a violation of the static semantics of Ada. In
19295 that case GNAT diagnoses the constructs in the program that are illegal.
19296 It is then a straightforward matter for the user to modify those parts of
19300 The illegality may be a violation of the dynamic semantics of Ada. In
19301 that case the program compiles and executes, but may generate incorrect
19302 results, or may terminate abnormally with some exception.
19305 When presented with a program that contains convoluted errors, GNAT
19306 itself may terminate abnormally without providing full diagnostics on
19307 the incorrect user program.
19315 * The GNAT Debugger GDB::
19317 * Introduction to GDB Commands::
19318 * Using Ada Expressions::
19319 * Calling User-Defined Subprograms::
19320 * Using the next Command in a Function::
19321 * Stopping When Ada Exceptions Are Raised::
19323 * Debugging Generic Units::
19324 * Remote Debugging with gdbserver::
19325 * GNAT Abnormal Termination or Failure to Terminate::
19326 * Naming Conventions for GNAT Source Files::
19327 * Getting Internal Debugging Information::
19328 * Stack Traceback::
19329 * Pretty-Printers for the GNAT runtime::
19333 @node The GNAT Debugger GDB,Running GDB,,Running and Debugging Ada Programs
19334 @anchor{gnat_ugn/gnat_and_program_execution the-gnat-debugger-gdb}@anchor{16d}@anchor{gnat_ugn/gnat_and_program_execution id3}@anchor{16e}
19335 @subsection The GNAT Debugger GDB
19338 @code{GDB} is a general purpose, platform-independent debugger that
19339 can be used to debug mixed-language programs compiled with @code{gcc},
19340 and in particular is capable of debugging Ada programs compiled with
19341 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
19342 complex Ada data structures.
19344 See @cite{Debugging with GDB},
19345 for full details on the usage of @code{GDB}, including a section on
19346 its usage on programs. This manual should be consulted for full
19347 details. The section that follows is a brief introduction to the
19348 philosophy and use of @code{GDB}.
19350 When GNAT programs are compiled, the compiler optionally writes debugging
19351 information into the generated object file, including information on
19352 line numbers, and on declared types and variables. This information is
19353 separate from the generated code. It makes the object files considerably
19354 larger, but it does not add to the size of the actual executable that
19355 will be loaded into memory, and has no impact on run-time performance. The
19356 generation of debug information is triggered by the use of the
19357 @code{-g} switch in the @code{gcc} or @code{gnatmake} command
19358 used to carry out the compilations. It is important to emphasize that
19359 the use of these options does not change the generated code.
19361 The debugging information is written in standard system formats that
19362 are used by many tools, including debuggers and profilers. The format
19363 of the information is typically designed to describe C types and
19364 semantics, but GNAT implements a translation scheme which allows full
19365 details about Ada types and variables to be encoded into these
19366 standard C formats. Details of this encoding scheme may be found in
19367 the file exp_dbug.ads in the GNAT source distribution. However, the
19368 details of this encoding are, in general, of no interest to a user,
19369 since @code{GDB} automatically performs the necessary decoding.
19371 When a program is bound and linked, the debugging information is
19372 collected from the object files, and stored in the executable image of
19373 the program. Again, this process significantly increases the size of
19374 the generated executable file, but it does not increase the size of
19375 the executable program itself. Furthermore, if this program is run in
19376 the normal manner, it runs exactly as if the debug information were
19377 not present, and takes no more actual memory.
19379 However, if the program is run under control of @code{GDB}, the
19380 debugger is activated. The image of the program is loaded, at which
19381 point it is ready to run. If a run command is given, then the program
19382 will run exactly as it would have if @code{GDB} were not present. This
19383 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
19384 entirely non-intrusive until a breakpoint is encountered. If no
19385 breakpoint is ever hit, the program will run exactly as it would if no
19386 debugger were present. When a breakpoint is hit, @code{GDB} accesses
19387 the debugging information and can respond to user commands to inspect
19388 variables, and more generally to report on the state of execution.
19390 @node Running GDB,Introduction to GDB Commands,The GNAT Debugger GDB,Running and Debugging Ada Programs
19391 @anchor{gnat_ugn/gnat_and_program_execution id4}@anchor{16f}@anchor{gnat_ugn/gnat_and_program_execution running-gdb}@anchor{170}
19392 @subsection Running GDB
19395 This section describes how to initiate the debugger.
19397 The debugger can be launched from a @code{GPS} menu or
19398 directly from the command line. The description below covers the latter use.
19399 All the commands shown can be used in the @code{GPS} debug console window,
19400 but there are usually more GUI-based ways to achieve the same effect.
19402 The command to run @code{GDB} is
19411 where @code{program} is the name of the executable file. This
19412 activates the debugger and results in a prompt for debugger commands.
19413 The simplest command is simply @code{run}, which causes the program to run
19414 exactly as if the debugger were not present. The following section
19415 describes some of the additional commands that can be given to @code{GDB}.
19417 @node Introduction to GDB Commands,Using Ada Expressions,Running GDB,Running and Debugging Ada Programs
19418 @anchor{gnat_ugn/gnat_and_program_execution introduction-to-gdb-commands}@anchor{171}@anchor{gnat_ugn/gnat_and_program_execution id5}@anchor{172}
19419 @subsection Introduction to GDB Commands
19422 @code{GDB} contains a large repertoire of commands.
19423 See @cite{Debugging with GDB} for extensive documentation on the use
19424 of these commands, together with examples of their use. Furthermore,
19425 the command @emph{help} invoked from within GDB activates a simple help
19426 facility which summarizes the available commands and their options.
19427 In this section we summarize a few of the most commonly
19428 used commands to give an idea of what @code{GDB} is about. You should create
19429 a simple program with debugging information and experiment with the use of
19430 these @code{GDB} commands on the program as you read through the
19440 @item @code{set args @emph{arguments}}
19442 The @emph{arguments} list above is a list of arguments to be passed to
19443 the program on a subsequent run command, just as though the arguments
19444 had been entered on a normal invocation of the program. The @code{set args}
19445 command is not needed if the program does not require arguments.
19454 The @code{run} command causes execution of the program to start from
19455 the beginning. If the program is already running, that is to say if
19456 you are currently positioned at a breakpoint, then a prompt will ask
19457 for confirmation that you want to abandon the current execution and
19465 @item @code{breakpoint @emph{location}}
19467 The breakpoint command sets a breakpoint, that is to say a point at which
19468 execution will halt and @code{GDB} will await further
19469 commands. @emph{location} is
19470 either a line number within a file, given in the format @code{file:linenumber},
19471 or it is the name of a subprogram. If you request that a breakpoint be set on
19472 a subprogram that is overloaded, a prompt will ask you to specify on which of
19473 those subprograms you want to breakpoint. You can also
19474 specify that all of them should be breakpointed. If the program is run
19475 and execution encounters the breakpoint, then the program
19476 stops and @code{GDB} signals that the breakpoint was encountered by
19477 printing the line of code before which the program is halted.
19484 @item @code{catch exception @emph{name}}
19486 This command causes the program execution to stop whenever exception
19487 @code{name} is raised. If @code{name} is omitted, then the execution is
19488 suspended when any exception is raised.
19495 @item @code{print @emph{expression}}
19497 This will print the value of the given expression. Most simple
19498 Ada expression formats are properly handled by @code{GDB}, so the expression
19499 can contain function calls, variables, operators, and attribute references.
19506 @item @code{continue}
19508 Continues execution following a breakpoint, until the next breakpoint or the
19509 termination of the program.
19518 Executes a single line after a breakpoint. If the next statement
19519 is a subprogram call, execution continues into (the first statement of)
19520 the called subprogram.
19529 Executes a single line. If this line is a subprogram call, executes and
19530 returns from the call.
19539 Lists a few lines around the current source location. In practice, it
19540 is usually more convenient to have a separate edit window open with the
19541 relevant source file displayed. Successive applications of this command
19542 print subsequent lines. The command can be given an argument which is a
19543 line number, in which case it displays a few lines around the specified one.
19550 @item @code{backtrace}
19552 Displays a backtrace of the call chain. This command is typically
19553 used after a breakpoint has occurred, to examine the sequence of calls that
19554 leads to the current breakpoint. The display includes one line for each
19555 activation record (frame) corresponding to an active subprogram.
19564 At a breakpoint, @code{GDB} can display the values of variables local
19565 to the current frame. The command @code{up} can be used to
19566 examine the contents of other active frames, by moving the focus up
19567 the stack, that is to say from callee to caller, one frame at a time.
19576 Moves the focus of @code{GDB} down from the frame currently being
19577 examined to the frame of its callee (the reverse of the previous command),
19584 @item @code{frame @emph{n}}
19586 Inspect the frame with the given number. The value 0 denotes the frame
19587 of the current breakpoint, that is to say the top of the call stack.
19596 Kills the child process in which the program is running under GDB.
19597 This may be useful for several purposes:
19603 It allows you to recompile and relink your program, since on many systems
19604 you cannot regenerate an executable file while it is running in a process.
19607 You can run your program outside the debugger, on systems that do not
19608 permit executing a program outside GDB while breakpoints are set
19612 It allows you to debug a core dump rather than a running process.
19617 The above list is a very short introduction to the commands that
19618 @code{GDB} provides. Important additional capabilities, including conditional
19619 breakpoints, the ability to execute command sequences on a breakpoint,
19620 the ability to debug at the machine instruction level and many other
19621 features are described in detail in @cite{Debugging with GDB}.
19622 Note that most commands can be abbreviated
19623 (for example, c for continue, bt for backtrace).
19625 @node Using Ada Expressions,Calling User-Defined Subprograms,Introduction to GDB Commands,Running and Debugging Ada Programs
19626 @anchor{gnat_ugn/gnat_and_program_execution id6}@anchor{173}@anchor{gnat_ugn/gnat_and_program_execution using-ada-expressions}@anchor{174}
19627 @subsection Using Ada Expressions
19630 @geindex Ada expressions (in gdb)
19632 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
19633 extensions. The philosophy behind the design of this subset is
19641 That @code{GDB} should provide basic literals and access to operations for
19642 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
19643 leaving more sophisticated computations to subprograms written into the
19644 program (which therefore may be called from @code{GDB}).
19647 That type safety and strict adherence to Ada language restrictions
19648 are not particularly relevant in a debugging context.
19651 That brevity is important to the @code{GDB} user.
19655 Thus, for brevity, the debugger acts as if there were
19656 implicit @code{with} and @code{use} clauses in effect for all user-written
19657 packages, thus making it unnecessary to fully qualify most names with
19658 their packages, regardless of context. Where this causes ambiguity,
19659 @code{GDB} asks the user's intent.
19661 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
19663 @node Calling User-Defined Subprograms,Using the next Command in a Function,Using Ada Expressions,Running and Debugging Ada Programs
19664 @anchor{gnat_ugn/gnat_and_program_execution id7}@anchor{175}@anchor{gnat_ugn/gnat_and_program_execution calling-user-defined-subprograms}@anchor{176}
19665 @subsection Calling User-Defined Subprograms
19668 An important capability of @code{GDB} is the ability to call user-defined
19669 subprograms while debugging. This is achieved simply by entering
19670 a subprogram call statement in the form:
19675 call subprogram-name (parameters)
19679 The keyword @code{call} can be omitted in the normal case where the
19680 @code{subprogram-name} does not coincide with any of the predefined
19681 @code{GDB} commands.
19683 The effect is to invoke the given subprogram, passing it the
19684 list of parameters that is supplied. The parameters can be expressions and
19685 can include variables from the program being debugged. The
19686 subprogram must be defined
19687 at the library level within your program, and @code{GDB} will call the
19688 subprogram within the environment of your program execution (which
19689 means that the subprogram is free to access or even modify variables
19690 within your program).
19692 The most important use of this facility is in allowing the inclusion of
19693 debugging routines that are tailored to particular data structures
19694 in your program. Such debugging routines can be written to provide a suitably
19695 high-level description of an abstract type, rather than a low-level dump
19696 of its physical layout. After all, the standard
19697 @code{GDB print} command only knows the physical layout of your
19698 types, not their abstract meaning. Debugging routines can provide information
19699 at the desired semantic level and are thus enormously useful.
19701 For example, when debugging GNAT itself, it is crucial to have access to
19702 the contents of the tree nodes used to represent the program internally.
19703 But tree nodes are represented simply by an integer value (which in turn
19704 is an index into a table of nodes).
19705 Using the @code{print} command on a tree node would simply print this integer
19706 value, which is not very useful. But the PN routine (defined in file
19707 treepr.adb in the GNAT sources) takes a tree node as input, and displays
19708 a useful high level representation of the tree node, which includes the
19709 syntactic category of the node, its position in the source, the integers
19710 that denote descendant nodes and parent node, as well as varied
19711 semantic information. To study this example in more detail, you might want to
19712 look at the body of the PN procedure in the stated file.
19714 Another useful application of this capability is to deal with situations of
19715 complex data which are not handled suitably by GDB. For example, if you specify
19716 Convention Fortran for a multi-dimensional array, GDB does not know that
19717 the ordering of array elements has been switched and will not properly
19718 address the array elements. In such a case, instead of trying to print the
19719 elements directly from GDB, you can write a callable procedure that prints
19720 the elements in the desired format.
19722 @node Using the next Command in a Function,Stopping When Ada Exceptions Are Raised,Calling User-Defined Subprograms,Running and Debugging Ada Programs
19723 @anchor{gnat_ugn/gnat_and_program_execution using-the-next-command-in-a-function}@anchor{177}@anchor{gnat_ugn/gnat_and_program_execution id8}@anchor{178}
19724 @subsection Using the @emph{next} Command in a Function
19727 When you use the @code{next} command in a function, the current source
19728 location will advance to the next statement as usual. A special case
19729 arises in the case of a @code{return} statement.
19731 Part of the code for a return statement is the 'epilogue' of the function.
19732 This is the code that returns to the caller. There is only one copy of
19733 this epilogue code, and it is typically associated with the last return
19734 statement in the function if there is more than one return. In some
19735 implementations, this epilogue is associated with the first statement
19738 The result is that if you use the @code{next} command from a return
19739 statement that is not the last return statement of the function you
19740 may see a strange apparent jump to the last return statement or to
19741 the start of the function. You should simply ignore this odd jump.
19742 The value returned is always that from the first return statement
19743 that was stepped through.
19745 @node Stopping When Ada Exceptions Are Raised,Ada Tasks,Using the next Command in a Function,Running and Debugging Ada Programs
19746 @anchor{gnat_ugn/gnat_and_program_execution stopping-when-ada-exceptions-are-raised}@anchor{179}@anchor{gnat_ugn/gnat_and_program_execution id9}@anchor{17a}
19747 @subsection Stopping When Ada Exceptions Are Raised
19750 @geindex Exceptions (in gdb)
19752 You can set catchpoints that stop the program execution when your program
19753 raises selected exceptions.
19762 @item @code{catch exception}
19764 Set a catchpoint that stops execution whenever (any task in the) program
19765 raises any exception.
19772 @item @code{catch exception @emph{name}}
19774 Set a catchpoint that stops execution whenever (any task in the) program
19775 raises the exception @emph{name}.
19782 @item @code{catch exception unhandled}
19784 Set a catchpoint that stops executing whenever (any task in the) program
19785 raises an exception for which there is no handler.
19792 @item @code{info exceptions}, @code{info exceptions @emph{regexp}}
19794 The @code{info exceptions} command permits the user to examine all defined
19795 exceptions within Ada programs. With a regular expression, @emph{regexp}, as
19796 argument, prints out only those exceptions whose name matches @emph{regexp}.
19800 @geindex Tasks (in gdb)
19802 @node Ada Tasks,Debugging Generic Units,Stopping When Ada Exceptions Are Raised,Running and Debugging Ada Programs
19803 @anchor{gnat_ugn/gnat_and_program_execution ada-tasks}@anchor{17b}@anchor{gnat_ugn/gnat_and_program_execution id10}@anchor{17c}
19804 @subsection Ada Tasks
19807 @code{GDB} allows the following task-related commands:
19816 @item @code{info tasks}
19818 This command shows a list of current Ada tasks, as in the following example:
19822 ID TID P-ID Thread Pri State Name
19823 1 8088000 0 807e000 15 Child Activation Wait main_task
19824 2 80a4000 1 80ae000 15 Accept/Select Wait b
19825 3 809a800 1 80a4800 15 Child Activation Wait a
19826 * 4 80ae800 3 80b8000 15 Running c
19829 In this listing, the asterisk before the first task indicates it to be the
19830 currently running task. The first column lists the task ID that is used
19831 to refer to tasks in the following commands.
19835 @geindex Breakpoints and tasks
19841 @code{break`@w{`}*linespec* `@w{`}task} @emph{taskid}, @code{break} @emph{linespec} @code{task} @emph{taskid} @code{if} ...
19845 These commands are like the @code{break ... thread ...}.
19846 @emph{linespec} specifies source lines.
19848 Use the qualifier @code{task @emph{taskid}} with a breakpoint command
19849 to specify that you only want @code{GDB} to stop the program when a
19850 particular Ada task reaches this breakpoint. @emph{taskid} is one of the
19851 numeric task identifiers assigned by @code{GDB}, shown in the first
19852 column of the @code{info tasks} display.
19854 If you do not specify @code{task @emph{taskid}} when you set a
19855 breakpoint, the breakpoint applies to @emph{all} tasks of your
19858 You can use the @code{task} qualifier on conditional breakpoints as
19859 well; in this case, place @code{task @emph{taskid}} before the
19860 breakpoint condition (before the @code{if}).
19864 @geindex Task switching (in gdb)
19870 @code{task @emph{taskno}}
19874 This command allows switching to the task referred by @emph{taskno}. In
19875 particular, this allows browsing of the backtrace of the specified
19876 task. It is advisable to switch back to the original task before
19877 continuing execution otherwise the scheduling of the program may be
19882 For more detailed information on the tasking support,
19883 see @cite{Debugging with GDB}.
19885 @geindex Debugging Generic Units
19889 @node Debugging Generic Units,Remote Debugging with gdbserver,Ada Tasks,Running and Debugging Ada Programs
19890 @anchor{gnat_ugn/gnat_and_program_execution debugging-generic-units}@anchor{17d}@anchor{gnat_ugn/gnat_and_program_execution id11}@anchor{17e}
19891 @subsection Debugging Generic Units
19894 GNAT always uses code expansion for generic instantiation. This means that
19895 each time an instantiation occurs, a complete copy of the original code is
19896 made, with appropriate substitutions of formals by actuals.
19898 It is not possible to refer to the original generic entities in
19899 @code{GDB}, but it is always possible to debug a particular instance of
19900 a generic, by using the appropriate expanded names. For example, if we have
19907 generic package k is
19908 procedure kp (v1 : in out integer);
19912 procedure kp (v1 : in out integer) is
19918 package k1 is new k;
19919 package k2 is new k;
19921 var : integer := 1;
19932 Then to break on a call to procedure kp in the k2 instance, simply
19938 (gdb) break g.k2.kp
19942 When the breakpoint occurs, you can step through the code of the
19943 instance in the normal manner and examine the values of local variables, as for
19946 @geindex Remote Debugging with gdbserver
19948 @node Remote Debugging with gdbserver,GNAT Abnormal Termination or Failure to Terminate,Debugging Generic Units,Running and Debugging Ada Programs
19949 @anchor{gnat_ugn/gnat_and_program_execution remote-debugging-with-gdbserver}@anchor{17f}@anchor{gnat_ugn/gnat_and_program_execution id12}@anchor{180}
19950 @subsection Remote Debugging with gdbserver
19953 On platforms where gdbserver is supported, it is possible to use this tool
19954 to debug your application remotely. This can be useful in situations
19955 where the program needs to be run on a target host that is different
19956 from the host used for development, particularly when the target has
19957 a limited amount of resources (either CPU and/or memory).
19959 To do so, start your program using gdbserver on the target machine.
19960 gdbserver then automatically suspends the execution of your program
19961 at its entry point, waiting for a debugger to connect to it. The
19962 following commands starts an application and tells gdbserver to
19963 wait for a connection with the debugger on localhost port 4444.
19968 $ gdbserver localhost:4444 program
19969 Process program created; pid = 5685
19970 Listening on port 4444
19974 Once gdbserver has started listening, we can tell the debugger to establish
19975 a connection with this gdbserver, and then start the same debugging session
19976 as if the program was being debugged on the same host, directly under
19977 the control of GDB.
19983 (gdb) target remote targethost:4444
19984 Remote debugging using targethost:4444
19985 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
19987 Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
19991 Breakpoint 1, foo () at foo.adb:4
19996 It is also possible to use gdbserver to attach to an already running
19997 program, in which case the execution of that program is simply suspended
19998 until the connection between the debugger and gdbserver is established.
20000 For more information on how to use gdbserver, see the @emph{Using the gdbserver Program}
20001 section in @cite{Debugging with GDB}.
20002 GNAT provides support for gdbserver on x86-linux, x86-windows and x86_64-linux.
20004 @geindex Abnormal Termination or Failure to Terminate
20006 @node GNAT Abnormal Termination or Failure to Terminate,Naming Conventions for GNAT Source Files,Remote Debugging with gdbserver,Running and Debugging Ada Programs
20007 @anchor{gnat_ugn/gnat_and_program_execution gnat-abnormal-termination-or-failure-to-terminate}@anchor{181}@anchor{gnat_ugn/gnat_and_program_execution id13}@anchor{182}
20008 @subsection GNAT Abnormal Termination or Failure to Terminate
20011 When presented with programs that contain serious errors in syntax
20013 GNAT may on rare occasions experience problems in operation, such
20015 segmentation fault or illegal memory access, raising an internal
20016 exception, terminating abnormally, or failing to terminate at all.
20017 In such cases, you can activate
20018 various features of GNAT that can help you pinpoint the construct in your
20019 program that is the likely source of the problem.
20021 The following strategies are presented in increasing order of
20022 difficulty, corresponding to your experience in using GNAT and your
20023 familiarity with compiler internals.
20029 Run @code{gcc} with the @code{-gnatf}. This first
20030 switch causes all errors on a given line to be reported. In its absence,
20031 only the first error on a line is displayed.
20033 The @code{-gnatdO} switch causes errors to be displayed as soon as they
20034 are encountered, rather than after compilation is terminated. If GNAT
20035 terminates prematurely or goes into an infinite loop, the last error
20036 message displayed may help to pinpoint the culprit.
20039 Run @code{gcc} with the @code{-v} (verbose) switch. In this
20040 mode, @code{gcc} produces ongoing information about the progress of the
20041 compilation and provides the name of each procedure as code is
20042 generated. This switch allows you to find which Ada procedure was being
20043 compiled when it encountered a code generation problem.
20046 @geindex -gnatdc switch
20052 Run @code{gcc} with the @code{-gnatdc} switch. This is a GNAT specific
20053 switch that does for the front-end what @code{-v} does
20054 for the back end. The system prints the name of each unit,
20055 either a compilation unit or nested unit, as it is being analyzed.
20058 Finally, you can start
20059 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
20060 front-end of GNAT, and can be run independently (normally it is just
20061 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
20062 would on a C program (but @ref{16d,,The GNAT Debugger GDB} for caveats). The
20063 @code{where} command is the first line of attack; the variable
20064 @code{lineno} (seen by @code{print lineno}), used by the second phase of
20065 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
20066 which the execution stopped, and @code{input_file name} indicates the name of
20070 @node Naming Conventions for GNAT Source Files,Getting Internal Debugging Information,GNAT Abnormal Termination or Failure to Terminate,Running and Debugging Ada Programs
20071 @anchor{gnat_ugn/gnat_and_program_execution naming-conventions-for-gnat-source-files}@anchor{183}@anchor{gnat_ugn/gnat_and_program_execution id14}@anchor{184}
20072 @subsection Naming Conventions for GNAT Source Files
20075 In order to examine the workings of the GNAT system, the following
20076 brief description of its organization may be helpful:
20082 Files with prefix @code{sc} contain the lexical scanner.
20085 All files prefixed with @code{par} are components of the parser. The
20086 numbers correspond to chapters of the Ada Reference Manual. For example,
20087 parsing of select statements can be found in @code{par-ch9.adb}.
20090 All files prefixed with @code{sem} perform semantic analysis. The
20091 numbers correspond to chapters of the Ada standard. For example, all
20092 issues involving context clauses can be found in @code{sem_ch10.adb}. In
20093 addition, some features of the language require sufficient special processing
20094 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
20095 dynamic dispatching, etc.
20098 All files prefixed with @code{exp} perform normalization and
20099 expansion of the intermediate representation (abstract syntax tree, or AST).
20100 these files use the same numbering scheme as the parser and semantics files.
20101 For example, the construction of record initialization procedures is done in
20102 @code{exp_ch3.adb}.
20105 The files prefixed with @code{bind} implement the binder, which
20106 verifies the consistency of the compilation, determines an order of
20107 elaboration, and generates the bind file.
20110 The files @code{atree.ads} and @code{atree.adb} detail the low-level
20111 data structures used by the front-end.
20114 The files @code{sinfo.ads} and @code{sinfo.adb} detail the structure of
20115 the abstract syntax tree as produced by the parser.
20118 The files @code{einfo.ads} and @code{einfo.adb} detail the attributes of
20119 all entities, computed during semantic analysis.
20122 Library management issues are dealt with in files with prefix
20125 @geindex Annex A (in Ada Reference Manual)
20128 Ada files with the prefix @code{a-} are children of @code{Ada}, as
20129 defined in Annex A.
20131 @geindex Annex B (in Ada reference Manual)
20134 Files with prefix @code{i-} are children of @code{Interfaces}, as
20135 defined in Annex B.
20137 @geindex System (package in Ada Reference Manual)
20140 Files with prefix @code{s-} are children of @code{System}. This includes
20141 both language-defined children and GNAT run-time routines.
20143 @geindex GNAT (package)
20146 Files with prefix @code{g-} are children of @code{GNAT}. These are useful
20147 general-purpose packages, fully documented in their specs. All
20148 the other @code{.c} files are modifications of common @code{gcc} files.
20151 @node Getting Internal Debugging Information,Stack Traceback,Naming Conventions for GNAT Source Files,Running and Debugging Ada Programs
20152 @anchor{gnat_ugn/gnat_and_program_execution id15}@anchor{185}@anchor{gnat_ugn/gnat_and_program_execution getting-internal-debugging-information}@anchor{186}
20153 @subsection Getting Internal Debugging Information
20156 Most compilers have internal debugging switches and modes. GNAT
20157 does also, except GNAT internal debugging switches and modes are not
20158 secret. A summary and full description of all the compiler and binder
20159 debug flags are in the file @code{debug.adb}. You must obtain the
20160 sources of the compiler to see the full detailed effects of these flags.
20162 The switches that print the source of the program (reconstructed from
20163 the internal tree) are of general interest for user programs, as are the
20165 the full internal tree, and the entity table (the symbol table
20166 information). The reconstructed source provides a readable version of the
20167 program after the front-end has completed analysis and expansion,
20168 and is useful when studying the performance of specific constructs.
20169 For example, constraint checks are indicated, complex aggregates
20170 are replaced with loops and assignments, and tasking primitives
20171 are replaced with run-time calls.
20175 @geindex stack traceback
20177 @geindex stack unwinding
20179 @node Stack Traceback,Pretty-Printers for the GNAT runtime,Getting Internal Debugging Information,Running and Debugging Ada Programs
20180 @anchor{gnat_ugn/gnat_and_program_execution stack-traceback}@anchor{187}@anchor{gnat_ugn/gnat_and_program_execution id16}@anchor{188}
20181 @subsection Stack Traceback
20184 Traceback is a mechanism to display the sequence of subprogram calls that
20185 leads to a specified execution point in a program. Often (but not always)
20186 the execution point is an instruction at which an exception has been raised.
20187 This mechanism is also known as @emph{stack unwinding} because it obtains
20188 its information by scanning the run-time stack and recovering the activation
20189 records of all active subprograms. Stack unwinding is one of the most
20190 important tools for program debugging.
20192 The first entry stored in traceback corresponds to the deepest calling level,
20193 that is to say the subprogram currently executing the instruction
20194 from which we want to obtain the traceback.
20196 Note that there is no runtime performance penalty when stack traceback
20197 is enabled, and no exception is raised during program execution.
20200 @geindex non-symbolic
20203 * Non-Symbolic Traceback::
20204 * Symbolic Traceback::
20208 @node Non-Symbolic Traceback,Symbolic Traceback,,Stack Traceback
20209 @anchor{gnat_ugn/gnat_and_program_execution non-symbolic-traceback}@anchor{189}@anchor{gnat_ugn/gnat_and_program_execution id17}@anchor{18a}
20210 @subsubsection Non-Symbolic Traceback
20213 Note: this feature is not supported on all platforms. See
20214 @code{GNAT.Traceback} spec in @code{g-traceb.ads}
20215 for a complete list of supported platforms.
20217 @subsubheading Tracebacks From an Unhandled Exception
20220 A runtime non-symbolic traceback is a list of addresses of call instructions.
20221 To enable this feature you must use the @code{-E}
20222 @code{gnatbind} option. With this option a stack traceback is stored as part
20223 of exception information. You can retrieve this information using the
20224 @code{addr2line} tool.
20226 Here is a simple example:
20235 raise Constraint_Error;
20249 $ gnatmake stb -bargs -E
20252 Execution terminated by unhandled exception
20253 Exception name: CONSTRAINT_ERROR
20255 Call stack traceback locations:
20256 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20260 As we see the traceback lists a sequence of addresses for the unhandled
20261 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
20262 guess that this exception come from procedure P1. To translate these
20263 addresses into the source lines where the calls appear, the
20264 @code{addr2line} tool, described below, is invaluable. The use of this tool
20265 requires the program to be compiled with debug information.
20270 $ gnatmake -g stb -bargs -E
20273 Execution terminated by unhandled exception
20274 Exception name: CONSTRAINT_ERROR
20276 Call stack traceback locations:
20277 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20279 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
20280 0x4011f1 0x77e892a4
20282 00401373 at d:/stb/stb.adb:5
20283 0040138B at d:/stb/stb.adb:10
20284 0040139C at d:/stb/stb.adb:14
20285 00401335 at d:/stb/b~stb.adb:104
20286 004011C4 at /build/.../crt1.c:200
20287 004011F1 at /build/.../crt1.c:222
20288 77E892A4 in ?? at ??:0
20292 The @code{addr2line} tool has several other useful options:
20297 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
20304 to get the function name corresponding to any location
20308 @code{--demangle=gnat}
20312 to use the gnat decoding mode for the function names.
20313 Note that for binutils version 2.9.x the option is
20314 simply @code{--demangle}.
20320 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
20321 0x40139c 0x401335 0x4011c4 0x4011f1
20323 00401373 in stb.p1 at d:/stb/stb.adb:5
20324 0040138B in stb.p2 at d:/stb/stb.adb:10
20325 0040139C in stb at d:/stb/stb.adb:14
20326 00401335 in main at d:/stb/b~stb.adb:104
20327 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
20328 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
20332 From this traceback we can see that the exception was raised in
20333 @code{stb.adb} at line 5, which was reached from a procedure call in
20334 @code{stb.adb} at line 10, and so on. The @code{b~std.adb} is the binder file,
20335 which contains the call to the main program.
20336 @ref{11c,,Running gnatbind}. The remaining entries are assorted runtime routines,
20337 and the output will vary from platform to platform.
20339 It is also possible to use @code{GDB} with these traceback addresses to debug
20340 the program. For example, we can break at a given code location, as reported
20341 in the stack traceback:
20350 Furthermore, this feature is not implemented inside Windows DLL. Only
20351 the non-symbolic traceback is reported in this case.
20356 (gdb) break *0x401373
20357 Breakpoint 1 at 0x401373: file stb.adb, line 5.
20361 It is important to note that the stack traceback addresses
20362 do not change when debug information is included. This is particularly useful
20363 because it makes it possible to release software without debug information (to
20364 minimize object size), get a field report that includes a stack traceback
20365 whenever an internal bug occurs, and then be able to retrieve the sequence
20366 of calls with the same program compiled with debug information.
20368 @subsubheading Tracebacks From Exception Occurrences
20371 Non-symbolic tracebacks are obtained by using the @code{-E} binder argument.
20372 The stack traceback is attached to the exception information string, and can
20373 be retrieved in an exception handler within the Ada program, by means of the
20374 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
20380 with Ada.Exceptions;
20385 use Ada.Exceptions;
20393 Text_IO.Put_Line (Exception_Information (E));
20407 This program will output:
20414 Exception name: CONSTRAINT_ERROR
20415 Message: stb.adb:12
20416 Call stack traceback locations:
20417 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
20421 @subsubheading Tracebacks From Anywhere in a Program
20424 It is also possible to retrieve a stack traceback from anywhere in a
20425 program. For this you need to
20426 use the @code{GNAT.Traceback} API. This package includes a procedure called
20427 @code{Call_Chain} that computes a complete stack traceback, as well as useful
20428 display procedures described below. It is not necessary to use the
20429 @code{-E} @code{gnatbind} option in this case, because the stack traceback mechanism
20430 is invoked explicitly.
20432 In the following example we compute a traceback at a specific location in
20433 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
20434 convert addresses to strings:
20440 with GNAT.Traceback;
20441 with GNAT.Debug_Utilities;
20447 use GNAT.Traceback;
20450 TB : Tracebacks_Array (1 .. 10);
20451 -- We are asking for a maximum of 10 stack frames.
20453 -- Len will receive the actual number of stack frames returned.
20455 Call_Chain (TB, Len);
20457 Text_IO.Put ("In STB.P1 : ");
20459 for K in 1 .. Len loop
20460 Text_IO.Put (Debug_Utilities.Image (TB (K)));
20481 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
20482 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
20486 You can then get further information by invoking the @code{addr2line}
20487 tool as described earlier (note that the hexadecimal addresses
20488 need to be specified in C format, with a leading '0x').
20493 @node Symbolic Traceback,,Non-Symbolic Traceback,Stack Traceback
20494 @anchor{gnat_ugn/gnat_and_program_execution id18}@anchor{18b}@anchor{gnat_ugn/gnat_and_program_execution symbolic-traceback}@anchor{18c}
20495 @subsubsection Symbolic Traceback
20498 A symbolic traceback is a stack traceback in which procedure names are
20499 associated with each code location.
20501 Note that this feature is not supported on all platforms. See
20502 @code{GNAT.Traceback.Symbolic} spec in @code{g-trasym.ads} for a complete
20503 list of currently supported platforms.
20505 Note that the symbolic traceback requires that the program be compiled
20506 with debug information. If it is not compiled with debug information
20507 only the non-symbolic information will be valid.
20509 @subsubheading Tracebacks From Exception Occurrences
20512 Here is an example:
20518 with GNAT.Traceback.Symbolic;
20524 raise Constraint_Error;
20541 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
20546 $ gnatmake -g .\stb -bargs -E
20549 0040149F in stb.p1 at stb.adb:8
20550 004014B7 in stb.p2 at stb.adb:13
20551 004014CF in stb.p3 at stb.adb:18
20552 004015DD in ada.stb at stb.adb:22
20553 00401461 in main at b~stb.adb:168
20554 004011C4 in __mingw_CRTStartup at crt1.c:200
20555 004011F1 in mainCRTStartup at crt1.c:222
20556 77E892A4 in ?? at ??:0
20560 In the above example the @code{.\} syntax in the @code{gnatmake} command
20561 is currently required by @code{addr2line} for files that are in
20562 the current working directory.
20563 Moreover, the exact sequence of linker options may vary from platform
20565 The above @code{-largs} section is for Windows platforms. By contrast,
20566 under Unix there is no need for the @code{-largs} section.
20567 Differences across platforms are due to details of linker implementation.
20569 @subsubheading Tracebacks From Anywhere in a Program
20572 It is possible to get a symbolic stack traceback
20573 from anywhere in a program, just as for non-symbolic tracebacks.
20574 The first step is to obtain a non-symbolic
20575 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
20576 information. Here is an example:
20582 with GNAT.Traceback;
20583 with GNAT.Traceback.Symbolic;
20588 use GNAT.Traceback;
20589 use GNAT.Traceback.Symbolic;
20592 TB : Tracebacks_Array (1 .. 10);
20593 -- We are asking for a maximum of 10 stack frames.
20595 -- Len will receive the actual number of stack frames returned.
20597 Call_Chain (TB, Len);
20598 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
20612 @subsubheading Automatic Symbolic Tracebacks
20615 Symbolic tracebacks may also be enabled by using the -Es switch to gnatbind (as
20616 in @code{gprbuild -g ... -bargs -Es}).
20617 This will cause the Exception_Information to contain a symbolic traceback,
20618 which will also be printed if an unhandled exception terminates the
20621 @node Pretty-Printers for the GNAT runtime,,Stack Traceback,Running and Debugging Ada Programs
20622 @anchor{gnat_ugn/gnat_and_program_execution id19}@anchor{18d}@anchor{gnat_ugn/gnat_and_program_execution pretty-printers-for-the-gnat-runtime}@anchor{18e}
20623 @subsection Pretty-Printers for the GNAT runtime
20626 As discussed in @cite{Calling User-Defined Subprograms}, GDB's
20627 @code{print} command only knows about the physical layout of program data
20628 structures and therefore normally displays only low-level dumps, which
20629 are often hard to understand.
20631 An example of this is when trying to display the contents of an Ada
20632 standard container, such as @code{Ada.Containers.Ordered_Maps.Map}:
20637 with Ada.Containers.Ordered_Maps;
20640 package Int_To_Nat is
20641 new Ada.Containers.Ordered_Maps (Integer, Natural);
20643 Map : Int_To_Nat.Map;
20645 Map.Insert (1, 10);
20646 Map.Insert (2, 20);
20647 Map.Insert (3, 30);
20649 Map.Clear; -- BREAK HERE
20654 When this program is built with debugging information and run under
20655 GDB up to the @code{Map.Clear} statement, trying to print @code{Map} will
20656 yield information that is only relevant to the developers of our standard
20678 Fortunately, GDB has a feature called pretty-printers@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Introduction},
20679 which allows customizing how GDB displays data structures. The GDB
20680 shipped with GNAT embeds such pretty-printers for the most common
20681 containers in the standard library. To enable them, either run the
20682 following command manually under GDB or add it to your @code{.gdbinit} file:
20687 python import gnatdbg; gnatdbg.setup()
20691 Once this is done, GDB's @code{print} command will automatically use
20692 these pretty-printers when appropriate. Using the previous example:
20698 $1 = pp.int_to_nat.map of length 3 = @{
20706 Pretty-printers are invoked each time GDB tries to display a value,
20707 including when displaying the arguments of a called subprogram (in
20708 GDB's @code{backtrace} command) or when printing the value returned by a
20709 function (in GDB's @code{finish} command).
20711 To display a value without involving pretty-printers, @code{print} can be
20712 invoked with its @code{/r} option:
20723 Finer control of pretty-printers is also possible: see GDB's online documentation@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Commands}
20724 for more information.
20728 @node Profiling,Improving Performance,Running and Debugging Ada Programs,GNAT and Program Execution
20729 @anchor{gnat_ugn/gnat_and_program_execution profiling}@anchor{25}@anchor{gnat_ugn/gnat_and_program_execution id20}@anchor{18f}
20733 This section describes how to use the the @code{gprof} profiler tool on Ada
20741 * Profiling an Ada Program with gprof::
20745 @node Profiling an Ada Program with gprof,,,Profiling
20746 @anchor{gnat_ugn/gnat_and_program_execution id21}@anchor{190}@anchor{gnat_ugn/gnat_and_program_execution profiling-an-ada-program-with-gprof}@anchor{191}
20747 @subsection Profiling an Ada Program with gprof
20750 This section is not meant to be an exhaustive documentation of @code{gprof}.
20751 Full documentation for it can be found in the @cite{GNU Profiler User's Guide}
20752 documentation that is part of this GNAT distribution.
20754 Profiling a program helps determine the parts of a program that are executed
20755 most often, and are therefore the most time-consuming.
20757 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
20758 better handle Ada programs and multitasking.
20759 It is currently supported on the following platforms
20771 In order to profile a program using @code{gprof}, several steps are needed:
20777 Instrument the code, which requires a full recompilation of the project with the
20781 Execute the program under the analysis conditions, i.e. with the desired
20785 Analyze the results using the @code{gprof} tool.
20788 The following sections detail the different steps, and indicate how
20789 to interpret the results.
20792 * Compilation for profiling::
20793 * Program execution::
20795 * Interpretation of profiling results::
20799 @node Compilation for profiling,Program execution,,Profiling an Ada Program with gprof
20800 @anchor{gnat_ugn/gnat_and_program_execution id22}@anchor{192}@anchor{gnat_ugn/gnat_and_program_execution compilation-for-profiling}@anchor{193}
20801 @subsubsection Compilation for profiling
20805 @geindex for profiling
20807 @geindex -pg (gnatlink)
20808 @geindex for profiling
20810 In order to profile a program the first step is to tell the compiler
20811 to generate the necessary profiling information. The compiler switch to be used
20812 is @code{-pg}, which must be added to other compilation switches. This
20813 switch needs to be specified both during compilation and link stages, and can
20814 be specified once when using gnatmake:
20819 $ gnatmake -f -pg -P my_project
20823 Note that only the objects that were compiled with the @code{-pg} switch will
20824 be profiled; if you need to profile your whole project, use the @code{-f}
20825 gnatmake switch to force full recompilation.
20827 @node Program execution,Running gprof,Compilation for profiling,Profiling an Ada Program with gprof
20828 @anchor{gnat_ugn/gnat_and_program_execution program-execution}@anchor{194}@anchor{gnat_ugn/gnat_and_program_execution id23}@anchor{195}
20829 @subsubsection Program execution
20832 Once the program has been compiled for profiling, you can run it as usual.
20834 The only constraint imposed by profiling is that the program must terminate
20835 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
20838 Once the program completes execution, a data file called @code{gmon.out} is
20839 generated in the directory where the program was launched from. If this file
20840 already exists, it will be overwritten.
20842 @node Running gprof,Interpretation of profiling results,Program execution,Profiling an Ada Program with gprof
20843 @anchor{gnat_ugn/gnat_and_program_execution running-gprof}@anchor{196}@anchor{gnat_ugn/gnat_and_program_execution id24}@anchor{197}
20844 @subsubsection Running gprof
20847 The @code{gprof} tool is called as follow:
20852 $ gprof my_prog gmon.out
20865 The complete form of the gprof command line is the following:
20870 $ gprof [switches] [executable [data-file]]
20874 @code{gprof} supports numerous switches. The order of these
20875 switch does not matter. The full list of options can be found in
20876 the GNU Profiler User's Guide documentation that comes with this documentation.
20878 The following is the subset of those switches that is most relevant:
20880 @geindex --demangle (gprof)
20885 @item @code{--demangle[=@emph{style}]}, @code{--no-demangle}
20887 These options control whether symbol names should be demangled when
20888 printing output. The default is to demangle C++ symbols. The
20889 @code{--no-demangle} option may be used to turn off demangling. Different
20890 compilers have different mangling styles. The optional demangling style
20891 argument can be used to choose an appropriate demangling style for your
20892 compiler, in particular Ada symbols generated by GNAT can be demangled using
20893 @code{--demangle=gnat}.
20896 @geindex -e (gprof)
20901 @item @code{-e @emph{function_name}}
20903 The @code{-e @emph{function}} option tells @code{gprof} not to print
20904 information about the function @code{function_name} (and its
20905 children...) in the call graph. The function will still be listed
20906 as a child of any functions that call it, but its index number will be
20907 shown as @code{[not printed]}. More than one @code{-e} option may be
20908 given; only one @code{function_name} may be indicated with each @code{-e}
20912 @geindex -E (gprof)
20917 @item @code{-E @emph{function_name}}
20919 The @code{-E @emph{function}} option works like the @code{-e} option, but
20920 execution time spent in the function (and children who were not called from
20921 anywhere else), will not be used to compute the percentages-of-time for
20922 the call graph. More than one @code{-E} option may be given; only one
20923 @code{function_name} may be indicated with each @code{-E`} option.
20926 @geindex -f (gprof)
20931 @item @code{-f @emph{function_name}}
20933 The @code{-f @emph{function}} option causes @code{gprof} to limit the
20934 call graph to the function @code{function_name} and its children (and
20935 their children...). More than one @code{-f} option may be given;
20936 only one @code{function_name} may be indicated with each @code{-f}
20940 @geindex -F (gprof)
20945 @item @code{-F @emph{function_name}}
20947 The @code{-F @emph{function}} option works like the @code{-f} option, but
20948 only time spent in the function and its children (and their
20949 children...) will be used to determine total-time and
20950 percentages-of-time for the call graph. More than one @code{-F} option
20951 may be given; only one @code{function_name} may be indicated with each
20952 @code{-F} option. The @code{-F} option overrides the @code{-E} option.
20955 @node Interpretation of profiling results,,Running gprof,Profiling an Ada Program with gprof
20956 @anchor{gnat_ugn/gnat_and_program_execution id25}@anchor{198}@anchor{gnat_ugn/gnat_and_program_execution interpretation-of-profiling-results}@anchor{199}
20957 @subsubsection Interpretation of profiling results
20960 The results of the profiling analysis are represented by two arrays: the
20961 'flat profile' and the 'call graph'. Full documentation of those outputs
20962 can be found in the GNU Profiler User's Guide.
20964 The flat profile shows the time spent in each function of the program, and how
20965 many time it has been called. This allows you to locate easily the most
20966 time-consuming functions.
20968 The call graph shows, for each subprogram, the subprograms that call it,
20969 and the subprograms that it calls. It also provides an estimate of the time
20970 spent in each of those callers/called subprograms.
20972 @node Improving Performance,Overflow Check Handling in GNAT,Profiling,GNAT and Program Execution
20973 @anchor{gnat_ugn/gnat_and_program_execution improving-performance}@anchor{26}@anchor{gnat_ugn/gnat_and_program_execution id26}@anchor{168}
20974 @section Improving Performance
20977 @geindex Improving performance
20979 This section presents several topics related to program performance.
20980 It first describes some of the tradeoffs that need to be considered
20981 and some of the techniques for making your program run faster.
20983 It then documents the unused subprogram/data elimination feature,
20984 which can reduce the size of program executables.
20987 * Performance Considerations::
20988 * Text_IO Suggestions::
20989 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
20993 @node Performance Considerations,Text_IO Suggestions,,Improving Performance
20994 @anchor{gnat_ugn/gnat_and_program_execution performance-considerations}@anchor{19a}@anchor{gnat_ugn/gnat_and_program_execution id27}@anchor{19b}
20995 @subsection Performance Considerations
20998 The GNAT system provides a number of options that allow a trade-off
21005 performance of the generated code
21008 speed of compilation
21011 minimization of dependences and recompilation
21014 the degree of run-time checking.
21017 The defaults (if no options are selected) aim at improving the speed
21018 of compilation and minimizing dependences, at the expense of performance
21019 of the generated code:
21028 no inlining of subprogram calls
21031 all run-time checks enabled except overflow and elaboration checks
21034 These options are suitable for most program development purposes. This
21035 section describes how you can modify these choices, and also provides
21036 some guidelines on debugging optimized code.
21039 * Controlling Run-Time Checks::
21040 * Use of Restrictions::
21041 * Optimization Levels::
21042 * Debugging Optimized Code::
21043 * Inlining of Subprograms::
21044 * Floating_Point_Operations::
21045 * Vectorization of loops::
21046 * Other Optimization Switches::
21047 * Optimization and Strict Aliasing::
21048 * Aliased Variables and Optimization::
21049 * Atomic Variables and Optimization::
21050 * Passive Task Optimization::
21054 @node Controlling Run-Time Checks,Use of Restrictions,,Performance Considerations
21055 @anchor{gnat_ugn/gnat_and_program_execution id28}@anchor{19c}@anchor{gnat_ugn/gnat_and_program_execution controlling-run-time-checks}@anchor{19d}
21056 @subsubsection Controlling Run-Time Checks
21059 By default, GNAT generates all run-time checks, except stack overflow
21060 checks, and checks for access before elaboration on subprogram
21061 calls. The latter are not required in default mode, because all
21062 necessary checking is done at compile time.
21064 @geindex -gnatp (gcc)
21066 @geindex -gnato (gcc)
21068 The gnat switch, @code{-gnatp} allows this default to be modified. See
21069 @ref{f9,,Run-Time Checks}.
21071 Our experience is that the default is suitable for most development
21074 Elaboration checks are off by default, and also not needed by default, since
21075 GNAT uses a static elaboration analysis approach that avoids the need for
21076 run-time checking. This manual contains a full chapter discussing the issue
21077 of elaboration checks, and if the default is not satisfactory for your use,
21078 you should read this chapter.
21080 For validity checks, the minimal checks required by the Ada Reference
21081 Manual (for case statements and assignments to array elements) are on
21082 by default. These can be suppressed by use of the @code{-gnatVn} switch.
21083 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
21084 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
21085 it may be reasonable to routinely use @code{-gnatVn}. Validity checks
21086 are also suppressed entirely if @code{-gnatp} is used.
21088 @geindex Overflow checks
21095 @geindex Unsuppress
21097 @geindex pragma Suppress
21099 @geindex pragma Unsuppress
21101 Note that the setting of the switches controls the default setting of
21102 the checks. They may be modified using either @code{pragma Suppress} (to
21103 remove checks) or @code{pragma Unsuppress} (to add back suppressed
21104 checks) in the program source.
21106 @node Use of Restrictions,Optimization Levels,Controlling Run-Time Checks,Performance Considerations
21107 @anchor{gnat_ugn/gnat_and_program_execution id29}@anchor{19e}@anchor{gnat_ugn/gnat_and_program_execution use-of-restrictions}@anchor{19f}
21108 @subsubsection Use of Restrictions
21111 The use of pragma Restrictions allows you to control which features are
21112 permitted in your program. Apart from the obvious point that if you avoid
21113 relatively expensive features like finalization (enforceable by the use
21114 of pragma Restrictions (No_Finalization), the use of this pragma does not
21115 affect the generated code in most cases.
21117 One notable exception to this rule is that the possibility of task abort
21118 results in some distributed overhead, particularly if finalization or
21119 exception handlers are used. The reason is that certain sections of code
21120 have to be marked as non-abortable.
21122 If you use neither the @code{abort} statement, nor asynchronous transfer
21123 of control (@code{select ... then abort}), then this distributed overhead
21124 is removed, which may have a general positive effect in improving
21125 overall performance. Especially code involving frequent use of tasking
21126 constructs and controlled types will show much improved performance.
21127 The relevant restrictions pragmas are
21132 pragma Restrictions (No_Abort_Statements);
21133 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
21137 It is recommended that these restriction pragmas be used if possible. Note
21138 that this also means that you can write code without worrying about the
21139 possibility of an immediate abort at any point.
21141 @node Optimization Levels,Debugging Optimized Code,Use of Restrictions,Performance Considerations
21142 @anchor{gnat_ugn/gnat_and_program_execution id30}@anchor{1a0}@anchor{gnat_ugn/gnat_and_program_execution optimization-levels}@anchor{fc}
21143 @subsubsection Optimization Levels
21148 Without any optimization option,
21149 the compiler's goal is to reduce the cost of
21150 compilation and to make debugging produce the expected results.
21151 Statements are independent: if you stop the program with a breakpoint between
21152 statements, you can then assign a new value to any variable or change
21153 the program counter to any other statement in the subprogram and get exactly
21154 the results you would expect from the source code.
21156 Turning on optimization makes the compiler attempt to improve the
21157 performance and/or code size at the expense of compilation time and
21158 possibly the ability to debug the program.
21160 If you use multiple
21161 -O options, with or without level numbers,
21162 the last such option is the one that is effective.
21164 The default is optimization off. This results in the fastest compile
21165 times, but GNAT makes absolutely no attempt to optimize, and the
21166 generated programs are considerably larger and slower than when
21167 optimization is enabled. You can use the
21168 @code{-O} switch (the permitted forms are @code{-O0}, @code{-O1}
21169 @code{-O2}, @code{-O3}, and @code{-Os})
21170 to @code{gcc} to control the optimization level:
21181 No optimization (the default);
21182 generates unoptimized code but has
21183 the fastest compilation time.
21185 Note that many other compilers do substantial optimization even
21186 if 'no optimization' is specified. With gcc, it is very unusual
21187 to use @code{-O0} for production if execution time is of any concern,
21188 since @code{-O0} means (almost) no optimization. This difference
21189 between gcc and other compilers should be kept in mind when
21190 doing performance comparisons.
21199 Moderate optimization;
21200 optimizes reasonably well but does not
21201 degrade compilation time significantly.
21211 generates highly optimized code and has
21212 the slowest compilation time.
21221 Full optimization as in @code{-O2};
21222 also uses more aggressive automatic inlining of subprograms within a unit
21223 (@ref{10f,,Inlining of Subprograms}) and attempts to vectorize loops.
21232 Optimize space usage (code and data) of resulting program.
21236 Higher optimization levels perform more global transformations on the
21237 program and apply more expensive analysis algorithms in order to generate
21238 faster and more compact code. The price in compilation time, and the
21239 resulting improvement in execution time,
21240 both depend on the particular application and the hardware environment.
21241 You should experiment to find the best level for your application.
21243 Since the precise set of optimizations done at each level will vary from
21244 release to release (and sometime from target to target), it is best to think
21245 of the optimization settings in general terms.
21246 See the @emph{Options That Control Optimization} section in
21247 @cite{Using the GNU Compiler Collection (GCC)}
21249 the @code{-O} settings and a number of @code{-f} options that
21250 individually enable or disable specific optimizations.
21252 Unlike some other compilation systems, @code{gcc} has
21253 been tested extensively at all optimization levels. There are some bugs
21254 which appear only with optimization turned on, but there have also been
21255 bugs which show up only in @emph{unoptimized} code. Selecting a lower
21256 level of optimization does not improve the reliability of the code
21257 generator, which in practice is highly reliable at all optimization
21260 Note regarding the use of @code{-O3}: The use of this optimization level
21261 ought not to be automatically preferred over that of level @code{-O2},
21262 since it often results in larger executables which may run more slowly.
21263 See further discussion of this point in @ref{10f,,Inlining of Subprograms}.
21265 @node Debugging Optimized Code,Inlining of Subprograms,Optimization Levels,Performance Considerations
21266 @anchor{gnat_ugn/gnat_and_program_execution debugging-optimized-code}@anchor{1a1}@anchor{gnat_ugn/gnat_and_program_execution id31}@anchor{1a2}
21267 @subsubsection Debugging Optimized Code
21270 @geindex Debugging optimized code
21272 @geindex Optimization and debugging
21274 Although it is possible to do a reasonable amount of debugging at
21275 nonzero optimization levels,
21276 the higher the level the more likely that
21277 source-level constructs will have been eliminated by optimization.
21278 For example, if a loop is strength-reduced, the loop
21279 control variable may be completely eliminated and thus cannot be
21280 displayed in the debugger.
21281 This can only happen at @code{-O2} or @code{-O3}.
21282 Explicit temporary variables that you code might be eliminated at
21283 level @code{-O1} or higher.
21287 The use of the @code{-g} switch,
21288 which is needed for source-level debugging,
21289 affects the size of the program executable on disk,
21290 and indeed the debugging information can be quite large.
21291 However, it has no effect on the generated code (and thus does not
21292 degrade performance)
21294 Since the compiler generates debugging tables for a compilation unit before
21295 it performs optimizations, the optimizing transformations may invalidate some
21296 of the debugging data. You therefore need to anticipate certain
21297 anomalous situations that may arise while debugging optimized code.
21298 These are the most common cases:
21304 @emph{The 'hopping Program Counter':} Repeated @code{step} or @code{next}
21306 the PC bouncing back and forth in the code. This may result from any of
21307 the following optimizations:
21313 @emph{Common subexpression elimination:} using a single instance of code for a
21314 quantity that the source computes several times. As a result you
21315 may not be able to stop on what looks like a statement.
21318 @emph{Invariant code motion:} moving an expression that does not change within a
21319 loop, to the beginning of the loop.
21322 @emph{Instruction scheduling:} moving instructions so as to
21323 overlap loads and stores (typically) with other code, or in
21324 general to move computations of values closer to their uses. Often
21325 this causes you to pass an assignment statement without the assignment
21326 happening and then later bounce back to the statement when the
21327 value is actually needed. Placing a breakpoint on a line of code
21328 and then stepping over it may, therefore, not always cause all the
21329 expected side-effects.
21333 @emph{The 'big leap':} More commonly known as @emph{cross-jumping}, in which
21334 two identical pieces of code are merged and the program counter suddenly
21335 jumps to a statement that is not supposed to be executed, simply because
21336 it (and the code following) translates to the same thing as the code
21337 that @emph{was} supposed to be executed. This effect is typically seen in
21338 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
21339 a @code{break} in a C @code{switch} statement.
21342 @emph{The 'roving variable':} The symptom is an unexpected value in a variable.
21343 There are various reasons for this effect:
21349 In a subprogram prologue, a parameter may not yet have been moved to its
21353 A variable may be dead, and its register re-used. This is
21354 probably the most common cause.
21357 As mentioned above, the assignment of a value to a variable may
21361 A variable may be eliminated entirely by value propagation or
21362 other means. In this case, GCC may incorrectly generate debugging
21363 information for the variable
21366 In general, when an unexpected value appears for a local variable or parameter
21367 you should first ascertain if that value was actually computed by
21368 your program, as opposed to being incorrectly reported by the debugger.
21370 array elements in an object designated by an access value
21371 are generally less of a problem, once you have ascertained that the access
21373 Typically, this means checking variables in the preceding code and in the
21374 calling subprogram to verify that the value observed is explainable from other
21375 values (one must apply the procedure recursively to those
21376 other values); or re-running the code and stopping a little earlier
21377 (perhaps before the call) and stepping to better see how the variable obtained
21378 the value in question; or continuing to step @emph{from} the point of the
21379 strange value to see if code motion had simply moved the variable's
21383 In light of such anomalies, a recommended technique is to use @code{-O0}
21384 early in the software development cycle, when extensive debugging capabilities
21385 are most needed, and then move to @code{-O1} and later @code{-O2} as
21386 the debugger becomes less critical.
21387 Whether to use the @code{-g} switch in the release version is
21388 a release management issue.
21389 Note that if you use @code{-g} you can then use the @code{strip} program
21390 on the resulting executable,
21391 which removes both debugging information and global symbols.
21393 @node Inlining of Subprograms,Floating_Point_Operations,Debugging Optimized Code,Performance Considerations
21394 @anchor{gnat_ugn/gnat_and_program_execution id32}@anchor{1a3}@anchor{gnat_ugn/gnat_and_program_execution inlining-of-subprograms}@anchor{10f}
21395 @subsubsection Inlining of Subprograms
21398 A call to a subprogram in the current unit is inlined if all the
21399 following conditions are met:
21405 The optimization level is at least @code{-O1}.
21408 The called subprogram is suitable for inlining: It must be small enough
21409 and not contain something that @code{gcc} cannot support in inlined
21412 @geindex pragma Inline
21417 Any one of the following applies: @code{pragma Inline} is applied to the
21418 subprogram; the subprogram is local to the unit and called once from
21419 within it; the subprogram is small and optimization level @code{-O2} is
21420 specified; optimization level @code{-O3} is specified.
21423 Calls to subprograms in @emph{with}ed units are normally not inlined.
21424 To achieve actual inlining (that is, replacement of the call by the code
21425 in the body of the subprogram), the following conditions must all be true:
21431 The optimization level is at least @code{-O1}.
21434 The called subprogram is suitable for inlining: It must be small enough
21435 and not contain something that @code{gcc} cannot support in inlined
21439 There is a @code{pragma Inline} for the subprogram.
21442 The @code{-gnatn} switch is used on the command line.
21445 Even if all these conditions are met, it may not be possible for
21446 the compiler to inline the call, due to the length of the body,
21447 or features in the body that make it impossible for the compiler
21448 to do the inlining.
21450 Note that specifying the @code{-gnatn} switch causes additional
21451 compilation dependencies. Consider the following:
21473 With the default behavior (no @code{-gnatn} switch specified), the
21474 compilation of the @code{Main} procedure depends only on its own source,
21475 @code{main.adb}, and the spec of the package in file @code{r.ads}. This
21476 means that editing the body of @code{R} does not require recompiling
21479 On the other hand, the call @code{R.Q} is not inlined under these
21480 circumstances. If the @code{-gnatn} switch is present when @code{Main}
21481 is compiled, the call will be inlined if the body of @code{Q} is small
21482 enough, but now @code{Main} depends on the body of @code{R} in
21483 @code{r.adb} as well as on the spec. This means that if this body is edited,
21484 the main program must be recompiled. Note that this extra dependency
21485 occurs whether or not the call is in fact inlined by @code{gcc}.
21487 The use of front end inlining with @code{-gnatN} generates similar
21488 additional dependencies.
21490 @geindex -fno-inline (gcc)
21492 Note: The @code{-fno-inline} switch overrides all other conditions and ensures that
21493 no inlining occurs, unless requested with pragma Inline_Always for @code{gcc}
21494 back-ends. The extra dependences resulting from @code{-gnatn} will still be active,
21495 even if this switch is used to suppress the resulting inlining actions.
21497 @geindex -fno-inline-functions (gcc)
21499 Note: The @code{-fno-inline-functions} switch can be used to prevent
21500 automatic inlining of subprograms if @code{-O3} is used.
21502 @geindex -fno-inline-small-functions (gcc)
21504 Note: The @code{-fno-inline-small-functions} switch can be used to prevent
21505 automatic inlining of small subprograms if @code{-O2} is used.
21507 @geindex -fno-inline-functions-called-once (gcc)
21509 Note: The @code{-fno-inline-functions-called-once} switch
21510 can be used to prevent inlining of subprograms local to the unit
21511 and called once from within it if @code{-O1} is used.
21513 Note regarding the use of @code{-O3}: @code{-gnatn} is made up of two
21514 sub-switches @code{-gnatn1} and @code{-gnatn2} that can be directly
21515 specified in lieu of it, @code{-gnatn} being translated into one of them
21516 based on the optimization level. With @code{-O2} or below, @code{-gnatn}
21517 is equivalent to @code{-gnatn1} which activates pragma @code{Inline} with
21518 moderate inlining across modules. With @code{-O3}, @code{-gnatn} is
21519 equivalent to @code{-gnatn2} which activates pragma @code{Inline} with
21520 full inlining across modules. If you have used pragma @code{Inline} in
21521 appropriate cases, then it is usually much better to use @code{-O2}
21522 and @code{-gnatn} and avoid the use of @code{-O3} which has the additional
21523 effect of inlining subprograms you did not think should be inlined. We have
21524 found that the use of @code{-O3} may slow down the compilation and increase
21525 the code size by performing excessive inlining, leading to increased
21526 instruction cache pressure from the increased code size and thus minor
21527 performance improvements. So the bottom line here is that you should not
21528 automatically assume that @code{-O3} is better than @code{-O2}, and
21529 indeed you should use @code{-O3} only if tests show that it actually
21530 improves performance for your program.
21532 @node Floating_Point_Operations,Vectorization of loops,Inlining of Subprograms,Performance Considerations
21533 @anchor{gnat_ugn/gnat_and_program_execution floating-point-operations}@anchor{1a4}@anchor{gnat_ugn/gnat_and_program_execution id33}@anchor{1a5}
21534 @subsubsection Floating_Point_Operations
21537 @geindex Floating-Point Operations
21539 On almost all targets, GNAT maps Float and Long_Float to the 32-bit and
21540 64-bit standard IEEE floating-point representations, and operations will
21541 use standard IEEE arithmetic as provided by the processor. On most, but
21542 not all, architectures, the attribute Machine_Overflows is False for these
21543 types, meaning that the semantics of overflow is implementation-defined.
21544 In the case of GNAT, these semantics correspond to the normal IEEE
21545 treatment of infinities and NaN (not a number) values. For example,
21546 1.0 / 0.0 yields plus infinitiy and 0.0 / 0.0 yields a NaN. By
21547 avoiding explicit overflow checks, the performance is greatly improved
21548 on many targets. However, if required, floating-point overflow can be
21549 enabled by the use of the pragma Check_Float_Overflow.
21551 Another consideration that applies specifically to x86 32-bit
21552 architectures is which form of floating-point arithmetic is used.
21553 By default the operations use the old style x86 floating-point,
21554 which implements an 80-bit extended precision form (on these
21555 architectures the type Long_Long_Float corresponds to that form).
21556 In addition, generation of efficient code in this mode means that
21557 the extended precision form will be used for intermediate results.
21558 This may be helpful in improving the final precision of a complex
21559 expression. However it means that the results obtained on the x86
21560 will be different from those on other architectures, and for some
21561 algorithms, the extra intermediate precision can be detrimental.
21563 In addition to this old-style floating-point, all modern x86 chips
21564 implement an alternative floating-point operation model referred
21565 to as SSE2. In this model there is no extended form, and furthermore
21566 execution performance is significantly enhanced. To force GNAT to use
21567 this more modern form, use both of the switches:
21571 -msse2 -mfpmath=sse
21574 A unit compiled with these switches will automatically use the more
21575 efficient SSE2 instruction set for Float and Long_Float operations.
21576 Note that the ABI has the same form for both floating-point models,
21577 so it is permissible to mix units compiled with and without these
21580 @node Vectorization of loops,Other Optimization Switches,Floating_Point_Operations,Performance Considerations
21581 @anchor{gnat_ugn/gnat_and_program_execution id34}@anchor{1a6}@anchor{gnat_ugn/gnat_and_program_execution vectorization-of-loops}@anchor{1a7}
21582 @subsubsection Vectorization of loops
21585 @geindex Optimization Switches
21587 You can take advantage of the auto-vectorizer present in the @code{gcc}
21588 back end to vectorize loops with GNAT. The corresponding command line switch
21589 is @code{-ftree-vectorize} but, as it is enabled by default at @code{-O3}
21590 and other aggressive optimizations helpful for vectorization also are enabled
21591 by default at this level, using @code{-O3} directly is recommended.
21593 You also need to make sure that the target architecture features a supported
21594 SIMD instruction set. For example, for the x86 architecture, you should at
21595 least specify @code{-msse2} to get significant vectorization (but you don't
21596 need to specify it for x86-64 as it is part of the base 64-bit architecture).
21597 Similarly, for the PowerPC architecture, you should specify @code{-maltivec}.
21599 The preferred loop form for vectorization is the @code{for} iteration scheme.
21600 Loops with a @code{while} iteration scheme can also be vectorized if they are
21601 very simple, but the vectorizer will quickly give up otherwise. With either
21602 iteration scheme, the flow of control must be straight, in particular no
21603 @code{exit} statement may appear in the loop body. The loop may however
21604 contain a single nested loop, if it can be vectorized when considered alone:
21609 A : array (1..4, 1..4) of Long_Float;
21610 S : array (1..4) of Long_Float;
21614 for I in A'Range(1) loop
21615 for J in A'Range(2) loop
21616 S (I) := S (I) + A (I, J);
21623 The vectorizable operations depend on the targeted SIMD instruction set, but
21624 the adding and some of the multiplying operators are generally supported, as
21625 well as the logical operators for modular types. Note that compiling
21626 with @code{-gnatp} might well reveal cases where some checks do thwart
21629 Type conversions may also prevent vectorization if they involve semantics that
21630 are not directly supported by the code generator or the SIMD instruction set.
21631 A typical example is direct conversion from floating-point to integer types.
21632 The solution in this case is to use the following idiom:
21637 Integer (S'Truncation (F))
21641 if @code{S} is the subtype of floating-point object @code{F}.
21643 In most cases, the vectorizable loops are loops that iterate over arrays.
21644 All kinds of array types are supported, i.e. constrained array types with
21650 type Array_Type is array (1 .. 4) of Long_Float;
21654 constrained array types with dynamic bounds:
21659 type Array_Type is array (1 .. Q.N) of Long_Float;
21661 type Array_Type is array (Q.K .. 4) of Long_Float;
21663 type Array_Type is array (Q.K .. Q.N) of Long_Float;
21667 or unconstrained array types:
21672 type Array_Type is array (Positive range <>) of Long_Float;
21676 The quality of the generated code decreases when the dynamic aspect of the
21677 array type increases, the worst code being generated for unconstrained array
21678 types. This is so because, the less information the compiler has about the
21679 bounds of the array, the more fallback code it needs to generate in order to
21680 fix things up at run time.
21682 It is possible to specify that a given loop should be subject to vectorization
21683 preferably to other optimizations by means of pragma @code{Loop_Optimize}:
21688 pragma Loop_Optimize (Vector);
21692 placed immediately within the loop will convey the appropriate hint to the
21693 compiler for this loop.
21695 It is also possible to help the compiler generate better vectorized code
21696 for a given loop by asserting that there are no loop-carried dependencies
21697 in the loop. Consider for example the procedure:
21702 type Arr is array (1 .. 4) of Long_Float;
21704 procedure Add (X, Y : not null access Arr; R : not null access Arr) is
21706 for I in Arr'Range loop
21707 R(I) := X(I) + Y(I);
21713 By default, the compiler cannot unconditionally vectorize the loop because
21714 assigning to a component of the array designated by R in one iteration could
21715 change the value read from the components of the array designated by X or Y
21716 in a later iteration. As a result, the compiler will generate two versions
21717 of the loop in the object code, one vectorized and the other not vectorized,
21718 as well as a test to select the appropriate version at run time. This can
21719 be overcome by another hint:
21724 pragma Loop_Optimize (Ivdep);
21728 placed immediately within the loop will tell the compiler that it can safely
21729 omit the non-vectorized version of the loop as well as the run-time test.
21731 @node Other Optimization Switches,Optimization and Strict Aliasing,Vectorization of loops,Performance Considerations
21732 @anchor{gnat_ugn/gnat_and_program_execution other-optimization-switches}@anchor{1a8}@anchor{gnat_ugn/gnat_and_program_execution id35}@anchor{1a9}
21733 @subsubsection Other Optimization Switches
21736 @geindex Optimization Switches
21738 Since GNAT uses the @code{gcc} back end, all the specialized
21739 @code{gcc} optimization switches are potentially usable. These switches
21740 have not been extensively tested with GNAT but can generally be expected
21741 to work. Examples of switches in this category are @code{-funroll-loops}
21742 and the various target-specific @code{-m} options (in particular, it has
21743 been observed that @code{-march=xxx} can significantly improve performance
21744 on appropriate machines). For full details of these switches, see
21745 the @emph{Submodel Options} section in the @emph{Hardware Models and Configurations}
21746 chapter of @cite{Using the GNU Compiler Collection (GCC)}.
21748 @node Optimization and Strict Aliasing,Aliased Variables and Optimization,Other Optimization Switches,Performance Considerations
21749 @anchor{gnat_ugn/gnat_and_program_execution optimization-and-strict-aliasing}@anchor{f3}@anchor{gnat_ugn/gnat_and_program_execution id36}@anchor{1aa}
21750 @subsubsection Optimization and Strict Aliasing
21755 @geindex Strict Aliasing
21757 @geindex No_Strict_Aliasing
21759 The strong typing capabilities of Ada allow an optimizer to generate
21760 efficient code in situations where other languages would be forced to
21761 make worst case assumptions preventing such optimizations. Consider
21762 the following example:
21768 type Int1 is new Integer;
21769 type Int2 is new Integer;
21770 type Int1A is access Int1;
21771 type Int2A is access Int2;
21778 for J in Data'Range loop
21779 if Data (J) = Int1V.all then
21780 Int2V.all := Int2V.all + 1;
21788 In this example, since the variable @code{Int1V} can only access objects
21789 of type @code{Int1}, and @code{Int2V} can only access objects of type
21790 @code{Int2}, there is no possibility that the assignment to
21791 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
21792 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
21793 for all iterations of the loop and avoid the extra memory reference
21794 required to dereference it each time through the loop.
21796 This kind of optimization, called strict aliasing analysis, is
21797 triggered by specifying an optimization level of @code{-O2} or
21798 higher or @code{-Os} and allows GNAT to generate more efficient code
21799 when access values are involved.
21801 However, although this optimization is always correct in terms of
21802 the formal semantics of the Ada Reference Manual, difficulties can
21803 arise if features like @code{Unchecked_Conversion} are used to break
21804 the typing system. Consider the following complete program example:
21810 type int1 is new integer;
21811 type int2 is new integer;
21812 type a1 is access int1;
21813 type a2 is access int2;
21818 function to_a2 (Input : a1) return a2;
21821 with Unchecked_Conversion;
21823 function to_a2 (Input : a1) return a2 is
21825 new Unchecked_Conversion (a1, a2);
21827 return to_a2u (Input);
21833 with Text_IO; use Text_IO;
21835 v1 : a1 := new int1;
21836 v2 : a2 := to_a2 (v1);
21840 put_line (int1'image (v1.all));
21845 This program prints out 0 in @code{-O0} or @code{-O1}
21846 mode, but it prints out 1 in @code{-O2} mode. That's
21847 because in strict aliasing mode, the compiler can and
21848 does assume that the assignment to @code{v2.all} could not
21849 affect the value of @code{v1.all}, since different types
21852 This behavior is not a case of non-conformance with the standard, since
21853 the Ada RM specifies that an unchecked conversion where the resulting
21854 bit pattern is not a correct value of the target type can result in an
21855 abnormal value and attempting to reference an abnormal value makes the
21856 execution of a program erroneous. That's the case here since the result
21857 does not point to an object of type @code{int2}. This means that the
21858 effect is entirely unpredictable.
21860 However, although that explanation may satisfy a language
21861 lawyer, in practice an applications programmer expects an
21862 unchecked conversion involving pointers to create true
21863 aliases and the behavior of printing 1 seems plain wrong.
21864 In this case, the strict aliasing optimization is unwelcome.
21866 Indeed the compiler recognizes this possibility, and the
21867 unchecked conversion generates a warning:
21872 p2.adb:5:07: warning: possible aliasing problem with type "a2"
21873 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
21874 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
21878 Unfortunately the problem is recognized when compiling the body of
21879 package @code{p2}, but the actual "bad" code is generated while
21880 compiling the body of @code{m} and this latter compilation does not see
21881 the suspicious @code{Unchecked_Conversion}.
21883 As implied by the warning message, there are approaches you can use to
21884 avoid the unwanted strict aliasing optimization in a case like this.
21886 One possibility is to simply avoid the use of @code{-O2}, but
21887 that is a bit drastic, since it throws away a number of useful
21888 optimizations that do not involve strict aliasing assumptions.
21890 A less drastic approach is to compile the program using the
21891 option @code{-fno-strict-aliasing}. Actually it is only the
21892 unit containing the dereferencing of the suspicious pointer
21893 that needs to be compiled. So in this case, if we compile
21894 unit @code{m} with this switch, then we get the expected
21895 value of zero printed. Analyzing which units might need
21896 the switch can be painful, so a more reasonable approach
21897 is to compile the entire program with options @code{-O2}
21898 and @code{-fno-strict-aliasing}. If the performance is
21899 satisfactory with this combination of options, then the
21900 advantage is that the entire issue of possible "wrong"
21901 optimization due to strict aliasing is avoided.
21903 To avoid the use of compiler switches, the configuration
21904 pragma @code{No_Strict_Aliasing} with no parameters may be
21905 used to specify that for all access types, the strict
21906 aliasing optimization should be suppressed.
21908 However, these approaches are still overkill, in that they causes
21909 all manipulations of all access values to be deoptimized. A more
21910 refined approach is to concentrate attention on the specific
21911 access type identified as problematic.
21913 First, if a careful analysis of uses of the pointer shows
21914 that there are no possible problematic references, then
21915 the warning can be suppressed by bracketing the
21916 instantiation of @code{Unchecked_Conversion} to turn
21922 pragma Warnings (Off);
21924 new Unchecked_Conversion (a1, a2);
21925 pragma Warnings (On);
21929 Of course that approach is not appropriate for this particular
21930 example, since indeed there is a problematic reference. In this
21931 case we can take one of two other approaches.
21933 The first possibility is to move the instantiation of unchecked
21934 conversion to the unit in which the type is declared. In
21935 this example, we would move the instantiation of
21936 @code{Unchecked_Conversion} from the body of package
21937 @code{p2} to the spec of package @code{p1}. Now the
21938 warning disappears. That's because any use of the
21939 access type knows there is a suspicious unchecked
21940 conversion, and the strict aliasing optimization
21941 is automatically suppressed for the type.
21943 If it is not practical to move the unchecked conversion to the same unit
21944 in which the destination access type is declared (perhaps because the
21945 source type is not visible in that unit), you may use pragma
21946 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
21947 same declarative sequence as the declaration of the access type:
21952 type a2 is access int2;
21953 pragma No_Strict_Aliasing (a2);
21957 Here again, the compiler now knows that the strict aliasing optimization
21958 should be suppressed for any reference to type @code{a2} and the
21959 expected behavior is obtained.
21961 Finally, note that although the compiler can generate warnings for
21962 simple cases of unchecked conversions, there are tricker and more
21963 indirect ways of creating type incorrect aliases which the compiler
21964 cannot detect. Examples are the use of address overlays and unchecked
21965 conversions involving composite types containing access types as
21966 components. In such cases, no warnings are generated, but there can
21967 still be aliasing problems. One safe coding practice is to forbid the
21968 use of address clauses for type overlaying, and to allow unchecked
21969 conversion only for primitive types. This is not really a significant
21970 restriction since any possible desired effect can be achieved by
21971 unchecked conversion of access values.
21973 The aliasing analysis done in strict aliasing mode can certainly
21974 have significant benefits. We have seen cases of large scale
21975 application code where the time is increased by up to 5% by turning
21976 this optimization off. If you have code that includes significant
21977 usage of unchecked conversion, you might want to just stick with
21978 @code{-O1} and avoid the entire issue. If you get adequate
21979 performance at this level of optimization level, that's probably
21980 the safest approach. If tests show that you really need higher
21981 levels of optimization, then you can experiment with @code{-O2}
21982 and @code{-O2 -fno-strict-aliasing} to see how much effect this
21983 has on size and speed of the code. If you really need to use
21984 @code{-O2} with strict aliasing in effect, then you should
21985 review any uses of unchecked conversion of access types,
21986 particularly if you are getting the warnings described above.
21988 @node Aliased Variables and Optimization,Atomic Variables and Optimization,Optimization and Strict Aliasing,Performance Considerations
21989 @anchor{gnat_ugn/gnat_and_program_execution id37}@anchor{1ab}@anchor{gnat_ugn/gnat_and_program_execution aliased-variables-and-optimization}@anchor{1ac}
21990 @subsubsection Aliased Variables and Optimization
21995 There are scenarios in which programs may
21996 use low level techniques to modify variables
21997 that otherwise might be considered to be unassigned. For example,
21998 a variable can be passed to a procedure by reference, which takes
21999 the address of the parameter and uses the address to modify the
22000 variable's value, even though it is passed as an IN parameter.
22001 Consider the following example:
22007 Max_Length : constant Natural := 16;
22008 type Char_Ptr is access all Character;
22010 procedure Get_String(Buffer: Char_Ptr; Size : Integer);
22011 pragma Import (C, Get_String, "get_string");
22013 Name : aliased String (1 .. Max_Length) := (others => ' ');
22016 function Addr (S : String) return Char_Ptr is
22017 function To_Char_Ptr is
22018 new Ada.Unchecked_Conversion (System.Address, Char_Ptr);
22020 return To_Char_Ptr (S (S'First)'Address);
22024 Temp := Addr (Name);
22025 Get_String (Temp, Max_Length);
22030 where Get_String is a C function that uses the address in Temp to
22031 modify the variable @code{Name}. This code is dubious, and arguably
22032 erroneous, and the compiler would be entitled to assume that
22033 @code{Name} is never modified, and generate code accordingly.
22035 However, in practice, this would cause some existing code that
22036 seems to work with no optimization to start failing at high
22037 levels of optimzization.
22039 What the compiler does for such cases is to assume that marking
22040 a variable as aliased indicates that some "funny business" may
22041 be going on. The optimizer recognizes the aliased keyword and
22042 inhibits optimizations that assume the value cannot be assigned.
22043 This means that the above example will in fact "work" reliably,
22044 that is, it will produce the expected results.
22046 @node Atomic Variables and Optimization,Passive Task Optimization,Aliased Variables and Optimization,Performance Considerations
22047 @anchor{gnat_ugn/gnat_and_program_execution atomic-variables-and-optimization}@anchor{1ad}@anchor{gnat_ugn/gnat_and_program_execution id38}@anchor{1ae}
22048 @subsubsection Atomic Variables and Optimization
22053 There are two considerations with regard to performance when
22054 atomic variables are used.
22056 First, the RM only guarantees that access to atomic variables
22057 be atomic, it has nothing to say about how this is achieved,
22058 though there is a strong implication that this should not be
22059 achieved by explicit locking code. Indeed GNAT will never
22060 generate any locking code for atomic variable access (it will
22061 simply reject any attempt to make a variable or type atomic
22062 if the atomic access cannot be achieved without such locking code).
22064 That being said, it is important to understand that you cannot
22065 assume that the entire variable will always be accessed. Consider
22072 A,B,C,D : Character;
22075 for R'Alignment use 4;
22078 pragma Atomic (RV);
22085 You cannot assume that the reference to @code{RV.B}
22086 will read the entire 32-bit
22087 variable with a single load instruction. It is perfectly legitimate if
22088 the hardware allows it to do a byte read of just the B field. This read
22089 is still atomic, which is all the RM requires. GNAT can and does take
22090 advantage of this, depending on the architecture and optimization level.
22091 Any assumption to the contrary is non-portable and risky. Even if you
22092 examine the assembly language and see a full 32-bit load, this might
22093 change in a future version of the compiler.
22095 If your application requires that all accesses to @code{RV} in this
22096 example be full 32-bit loads, you need to make a copy for the access
22103 RV_Copy : constant R := RV;
22110 Now the reference to RV must read the whole variable.
22111 Actually one can imagine some compiler which figures
22112 out that the whole copy is not required (because only
22113 the B field is actually accessed), but GNAT
22114 certainly won't do that, and we don't know of any
22115 compiler that would not handle this right, and the
22116 above code will in practice work portably across
22117 all architectures (that permit the Atomic declaration).
22119 The second issue with atomic variables has to do with
22120 the possible requirement of generating synchronization
22121 code. For more details on this, consult the sections on
22122 the pragmas Enable/Disable_Atomic_Synchronization in the
22123 GNAT Reference Manual. If performance is critical, and
22124 such synchronization code is not required, it may be
22125 useful to disable it.
22127 @node Passive Task Optimization,,Atomic Variables and Optimization,Performance Considerations
22128 @anchor{gnat_ugn/gnat_and_program_execution passive-task-optimization}@anchor{1af}@anchor{gnat_ugn/gnat_and_program_execution id39}@anchor{1b0}
22129 @subsubsection Passive Task Optimization
22132 @geindex Passive Task
22134 A passive task is one which is sufficiently simple that
22135 in theory a compiler could recognize it an implement it
22136 efficiently without creating a new thread. The original design
22137 of Ada 83 had in mind this kind of passive task optimization, but
22138 only a few Ada 83 compilers attempted it. The problem was that
22139 it was difficult to determine the exact conditions under which
22140 the optimization was possible. The result is a very fragile
22141 optimization where a very minor change in the program can
22142 suddenly silently make a task non-optimizable.
22144 With the revisiting of this issue in Ada 95, there was general
22145 agreement that this approach was fundamentally flawed, and the
22146 notion of protected types was introduced. When using protected
22147 types, the restrictions are well defined, and you KNOW that the
22148 operations will be optimized, and furthermore this optimized
22149 performance is fully portable.
22151 Although it would theoretically be possible for GNAT to attempt to
22152 do this optimization, but it really doesn't make sense in the
22153 context of Ada 95, and none of the Ada 95 compilers implement
22154 this optimization as far as we know. In particular GNAT never
22155 attempts to perform this optimization.
22157 In any new Ada 95 code that is written, you should always
22158 use protected types in place of tasks that might be able to
22159 be optimized in this manner.
22160 Of course this does not help if you have legacy Ada 83 code
22161 that depends on this optimization, but it is unusual to encounter
22162 a case where the performance gains from this optimization
22165 Your program should work correctly without this optimization. If
22166 you have performance problems, then the most practical
22167 approach is to figure out exactly where these performance problems
22168 arise, and update those particular tasks to be protected types. Note
22169 that typically clients of the tasks who call entries, will not have
22170 to be modified, only the task definition itself.
22172 @node Text_IO Suggestions,Reducing Size of Executables with Unused Subprogram/Data Elimination,Performance Considerations,Improving Performance
22173 @anchor{gnat_ugn/gnat_and_program_execution text-io-suggestions}@anchor{1b1}@anchor{gnat_ugn/gnat_and_program_execution id40}@anchor{1b2}
22174 @subsection @code{Text_IO} Suggestions
22177 @geindex Text_IO and performance
22179 The @code{Ada.Text_IO} package has fairly high overheads due in part to
22180 the requirement of maintaining page and line counts. If performance
22181 is critical, a recommendation is to use @code{Stream_IO} instead of
22182 @code{Text_IO} for volume output, since this package has less overhead.
22184 If @code{Text_IO} must be used, note that by default output to the standard
22185 output and standard error files is unbuffered (this provides better
22186 behavior when output statements are used for debugging, or if the
22187 progress of a program is observed by tracking the output, e.g. by
22188 using the Unix @emph{tail -f} command to watch redirected output.
22190 If you are generating large volumes of output with @code{Text_IO} and
22191 performance is an important factor, use a designated file instead
22192 of the standard output file, or change the standard output file to
22193 be buffered using @code{Interfaces.C_Streams.setvbuf}.
22195 @node Reducing Size of Executables with Unused Subprogram/Data Elimination,,Text_IO Suggestions,Improving Performance
22196 @anchor{gnat_ugn/gnat_and_program_execution id41}@anchor{1b3}@anchor{gnat_ugn/gnat_and_program_execution reducing-size-of-executables-with-unused-subprogram-data-elimination}@anchor{1b4}
22197 @subsection Reducing Size of Executables with Unused Subprogram/Data Elimination
22200 @geindex Uunused subprogram/data elimination
22202 This section describes how you can eliminate unused subprograms and data from
22203 your executable just by setting options at compilation time.
22206 * About unused subprogram/data elimination::
22207 * Compilation options::
22208 * Example of unused subprogram/data elimination::
22212 @node About unused subprogram/data elimination,Compilation options,,Reducing Size of Executables with Unused Subprogram/Data Elimination
22213 @anchor{gnat_ugn/gnat_and_program_execution id42}@anchor{1b5}@anchor{gnat_ugn/gnat_and_program_execution about-unused-subprogram-data-elimination}@anchor{1b6}
22214 @subsubsection About unused subprogram/data elimination
22217 By default, an executable contains all code and data of its composing objects
22218 (directly linked or coming from statically linked libraries), even data or code
22219 never used by this executable.
22221 This feature will allow you to eliminate such unused code from your
22222 executable, making it smaller (in disk and in memory).
22224 This functionality is available on all Linux platforms except for the IA-64
22225 architecture and on all cross platforms using the ELF binary file format.
22226 In both cases GNU binutils version 2.16 or later are required to enable it.
22228 @node Compilation options,Example of unused subprogram/data elimination,About unused subprogram/data elimination,Reducing Size of Executables with Unused Subprogram/Data Elimination
22229 @anchor{gnat_ugn/gnat_and_program_execution id43}@anchor{1b7}@anchor{gnat_ugn/gnat_and_program_execution compilation-options}@anchor{1b8}
22230 @subsubsection Compilation options
22233 The operation of eliminating the unused code and data from the final executable
22234 is directly performed by the linker.
22236 @geindex -ffunction-sections (gcc)
22238 @geindex -fdata-sections (gcc)
22240 In order to do this, it has to work with objects compiled with the
22242 @code{-ffunction-sections} @code{-fdata-sections}.
22244 These options are usable with C and Ada files.
22245 They will place respectively each
22246 function or data in a separate section in the resulting object file.
22248 Once the objects and static libraries are created with these options, the
22249 linker can perform the dead code elimination. You can do this by setting
22250 the @code{-Wl,--gc-sections} option to gcc command or in the
22251 @code{-largs} section of @code{gnatmake}. This will perform a
22252 garbage collection of code and data never referenced.
22254 If the linker performs a partial link (@code{-r} linker option), then you
22255 will need to provide the entry point using the @code{-e} / @code{--entry}
22258 Note that objects compiled without the @code{-ffunction-sections} and
22259 @code{-fdata-sections} options can still be linked with the executable.
22260 However, no dead code elimination will be performed on those objects (they will
22263 The GNAT static library is now compiled with -ffunction-sections and
22264 -fdata-sections on some platforms. This allows you to eliminate the unused code
22265 and data of the GNAT library from your executable.
22267 @node Example of unused subprogram/data elimination,,Compilation options,Reducing Size of Executables with Unused Subprogram/Data Elimination
22268 @anchor{gnat_ugn/gnat_and_program_execution example-of-unused-subprogram-data-elimination}@anchor{1b9}@anchor{gnat_ugn/gnat_and_program_execution id44}@anchor{1ba}
22269 @subsubsection Example of unused subprogram/data elimination
22272 Here is a simple example:
22285 Used_Data : Integer;
22286 Unused_Data : Integer;
22288 procedure Used (Data : Integer);
22289 procedure Unused (Data : Integer);
22292 package body Aux is
22293 procedure Used (Data : Integer) is
22298 procedure Unused (Data : Integer) is
22300 Unused_Data := Data;
22306 @code{Unused} and @code{Unused_Data} are never referenced in this code
22307 excerpt, and hence they may be safely removed from the final executable.
22314 $ nm test | grep used
22315 020015f0 T aux__unused
22316 02005d88 B aux__unused_data
22317 020015cc T aux__used
22318 02005d84 B aux__used_data
22320 $ gnatmake test -cargs -fdata-sections -ffunction-sections \\
22321 -largs -Wl,--gc-sections
22323 $ nm test | grep used
22324 02005350 T aux__used
22325 0201ffe0 B aux__used_data
22329 It can be observed that the procedure @code{Unused} and the object
22330 @code{Unused_Data} are removed by the linker when using the
22331 appropriate options.
22333 @geindex Overflow checks
22335 @geindex Checks (overflow)
22337 @node Overflow Check Handling in GNAT,Performing Dimensionality Analysis in GNAT,Improving Performance,GNAT and Program Execution
22338 @anchor{gnat_ugn/gnat_and_program_execution id45}@anchor{169}@anchor{gnat_ugn/gnat_and_program_execution overflow-check-handling-in-gnat}@anchor{27}
22339 @section Overflow Check Handling in GNAT
22342 This section explains how to control the handling of overflow checks.
22346 * Management of Overflows in GNAT::
22347 * Specifying the Desired Mode::
22348 * Default Settings::
22349 * Implementation Notes::
22353 @node Background,Management of Overflows in GNAT,,Overflow Check Handling in GNAT
22354 @anchor{gnat_ugn/gnat_and_program_execution id46}@anchor{1bb}@anchor{gnat_ugn/gnat_and_program_execution background}@anchor{1bc}
22355 @subsection Background
22358 Overflow checks are checks that the compiler may make to ensure
22359 that intermediate results are not out of range. For example:
22370 If @code{A} has the value @code{Integer'Last}, then the addition may cause
22371 overflow since the result is out of range of the type @code{Integer}.
22372 In this case @code{Constraint_Error} will be raised if checks are
22375 A trickier situation arises in examples like the following:
22386 where @code{A} is @code{Integer'Last} and @code{C} is @code{-1}.
22387 Now the final result of the expression on the right hand side is
22388 @code{Integer'Last} which is in range, but the question arises whether the
22389 intermediate addition of @code{(A + 1)} raises an overflow error.
22391 The (perhaps surprising) answer is that the Ada language
22392 definition does not answer this question. Instead it leaves
22393 it up to the implementation to do one of two things if overflow
22394 checks are enabled.
22400 raise an exception (@code{Constraint_Error}), or
22403 yield the correct mathematical result which is then used in
22404 subsequent operations.
22407 If the compiler chooses the first approach, then the assignment of this
22408 example will indeed raise @code{Constraint_Error} if overflow checking is
22409 enabled, or result in erroneous execution if overflow checks are suppressed.
22411 But if the compiler
22412 chooses the second approach, then it can perform both additions yielding
22413 the correct mathematical result, which is in range, so no exception
22414 will be raised, and the right result is obtained, regardless of whether
22415 overflow checks are suppressed.
22417 Note that in the first example an
22418 exception will be raised in either case, since if the compiler
22419 gives the correct mathematical result for the addition, it will
22420 be out of range of the target type of the assignment, and thus
22421 fails the range check.
22423 This lack of specified behavior in the handling of overflow for
22424 intermediate results is a source of non-portability, and can thus
22425 be problematic when programs are ported. Most typically this arises
22426 in a situation where the original compiler did not raise an exception,
22427 and then the application is moved to a compiler where the check is
22428 performed on the intermediate result and an unexpected exception is
22431 Furthermore, when using Ada 2012's preconditions and other
22432 assertion forms, another issue arises. Consider:
22437 procedure P (A, B : Integer) with
22438 Pre => A + B <= Integer'Last;
22442 One often wants to regard arithmetic in a context like this from
22443 a mathematical point of view. So for example, if the two actual parameters
22444 for a call to @code{P} are both @code{Integer'Last}, then
22445 the precondition should be regarded as False. If we are executing
22446 in a mode with run-time checks enabled for preconditions, then we would
22447 like this precondition to fail, rather than raising an exception
22448 because of the intermediate overflow.
22450 However, the language definition leaves the specification of
22451 whether the above condition fails (raising @code{Assert_Error}) or
22452 causes an intermediate overflow (raising @code{Constraint_Error})
22453 up to the implementation.
22455 The situation is worse in a case such as the following:
22460 procedure Q (A, B, C : Integer) with
22461 Pre => A + B + C <= Integer'Last;
22470 Q (A => Integer'Last, B => 1, C => -1);
22474 From a mathematical point of view the precondition
22475 is True, but at run time we may (but are not guaranteed to) get an
22476 exception raised because of the intermediate overflow (and we really
22477 would prefer this precondition to be considered True at run time).
22479 @node Management of Overflows in GNAT,Specifying the Desired Mode,Background,Overflow Check Handling in GNAT
22480 @anchor{gnat_ugn/gnat_and_program_execution id47}@anchor{1bd}@anchor{gnat_ugn/gnat_and_program_execution management-of-overflows-in-gnat}@anchor{1be}
22481 @subsection Management of Overflows in GNAT
22484 To deal with the portability issue, and with the problem of
22485 mathematical versus run-time interpretation of the expressions in
22486 assertions, GNAT provides comprehensive control over the handling
22487 of intermediate overflow. GNAT can operate in three modes, and
22488 furthemore, permits separate selection of operating modes for
22489 the expressions within assertions (here the term 'assertions'
22490 is used in the technical sense, which includes preconditions and so forth)
22491 and for expressions appearing outside assertions.
22493 The three modes are:
22499 @emph{Use base type for intermediate operations} (@code{STRICT})
22501 In this mode, all intermediate results for predefined arithmetic
22502 operators are computed using the base type, and the result must
22503 be in range of the base type. If this is not the
22504 case then either an exception is raised (if overflow checks are
22505 enabled) or the execution is erroneous (if overflow checks are suppressed).
22506 This is the normal default mode.
22509 @emph{Most intermediate overflows avoided} (@code{MINIMIZED})
22511 In this mode, the compiler attempts to avoid intermediate overflows by
22512 using a larger integer type, typically @code{Long_Long_Integer},
22513 as the type in which arithmetic is
22514 performed for predefined arithmetic operators. This may be slightly more
22516 run time (compared to suppressing intermediate overflow checks), though
22517 the cost is negligible on modern 64-bit machines. For the examples given
22518 earlier, no intermediate overflows would have resulted in exceptions,
22519 since the intermediate results are all in the range of
22520 @code{Long_Long_Integer} (typically 64-bits on nearly all implementations
22521 of GNAT). In addition, if checks are enabled, this reduces the number of
22522 checks that must be made, so this choice may actually result in an
22523 improvement in space and time behavior.
22525 However, there are cases where @code{Long_Long_Integer} is not large
22526 enough, consider the following example:
22531 procedure R (A, B, C, D : Integer) with
22532 Pre => (A**2 * B**2) / (C**2 * D**2) <= 10;
22536 where @code{A} = @code{B} = @code{C} = @code{D} = @code{Integer'Last}.
22537 Now the intermediate results are
22538 out of the range of @code{Long_Long_Integer} even though the final result
22539 is in range and the precondition is True (from a mathematical point
22540 of view). In such a case, operating in this mode, an overflow occurs
22541 for the intermediate computation (which is why this mode
22542 says @emph{most} intermediate overflows are avoided). In this case,
22543 an exception is raised if overflow checks are enabled, and the
22544 execution is erroneous if overflow checks are suppressed.
22547 @emph{All intermediate overflows avoided} (@code{ELIMINATED})
22549 In this mode, the compiler avoids all intermediate overflows
22550 by using arbitrary precision arithmetic as required. In this
22551 mode, the above example with @code{A**2 * B**2} would
22552 not cause intermediate overflow, because the intermediate result
22553 would be evaluated using sufficient precision, and the result
22554 of evaluating the precondition would be True.
22556 This mode has the advantage of avoiding any intermediate
22557 overflows, but at the expense of significant run-time overhead,
22558 including the use of a library (included automatically in this
22559 mode) for multiple-precision arithmetic.
22561 This mode provides cleaner semantics for assertions, since now
22562 the run-time behavior emulates true arithmetic behavior for the
22563 predefined arithmetic operators, meaning that there is never a
22564 conflict between the mathematical view of the assertion, and its
22567 Note that in this mode, the behavior is unaffected by whether or
22568 not overflow checks are suppressed, since overflow does not occur.
22569 It is possible for gigantic intermediate expressions to raise
22570 @code{Storage_Error} as a result of attempting to compute the
22571 results of such expressions (e.g. @code{Integer'Last ** Integer'Last})
22572 but overflow is impossible.
22575 Note that these modes apply only to the evaluation of predefined
22576 arithmetic, membership, and comparison operators for signed integer
22579 For fixed-point arithmetic, checks can be suppressed. But if checks
22581 then fixed-point values are always checked for overflow against the
22582 base type for intermediate expressions (that is such checks always
22583 operate in the equivalent of @code{STRICT} mode).
22585 For floating-point, on nearly all architectures, @code{Machine_Overflows}
22586 is False, and IEEE infinities are generated, so overflow exceptions
22587 are never raised. If you want to avoid infinities, and check that
22588 final results of expressions are in range, then you can declare a
22589 constrained floating-point type, and range checks will be carried
22590 out in the normal manner (with infinite values always failing all
22593 @node Specifying the Desired Mode,Default Settings,Management of Overflows in GNAT,Overflow Check Handling in GNAT
22594 @anchor{gnat_ugn/gnat_and_program_execution specifying-the-desired-mode}@anchor{f8}@anchor{gnat_ugn/gnat_and_program_execution id48}@anchor{1bf}
22595 @subsection Specifying the Desired Mode
22598 @geindex pragma Overflow_Mode
22600 The desired mode of for handling intermediate overflow can be specified using
22601 either the @code{Overflow_Mode} pragma or an equivalent compiler switch.
22602 The pragma has the form
22607 pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]);
22611 where @code{MODE} is one of
22617 @code{STRICT}: intermediate overflows checked (using base type)
22620 @code{MINIMIZED}: minimize intermediate overflows
22623 @code{ELIMINATED}: eliminate intermediate overflows
22626 The case is ignored, so @code{MINIMIZED}, @code{Minimized} and
22627 @code{minimized} all have the same effect.
22629 If only the @code{General} parameter is present, then the given @code{MODE} applies
22630 to expressions both within and outside assertions. If both arguments
22631 are present, then @code{General} applies to expressions outside assertions,
22632 and @code{Assertions} applies to expressions within assertions. For example:
22637 pragma Overflow_Mode
22638 (General => Minimized, Assertions => Eliminated);
22642 specifies that general expressions outside assertions be evaluated
22643 in 'minimize intermediate overflows' mode, and expressions within
22644 assertions be evaluated in 'eliminate intermediate overflows' mode.
22645 This is often a reasonable choice, avoiding excessive overhead
22646 outside assertions, but assuring a high degree of portability
22647 when importing code from another compiler, while incurring
22648 the extra overhead for assertion expressions to ensure that
22649 the behavior at run time matches the expected mathematical
22652 The @code{Overflow_Mode} pragma has the same scoping and placement
22653 rules as pragma @code{Suppress}, so it can occur either as a
22654 configuration pragma, specifying a default for the whole
22655 program, or in a declarative scope, where it applies to the
22656 remaining declarations and statements in that scope.
22658 Note that pragma @code{Overflow_Mode} does not affect whether
22659 overflow checks are enabled or suppressed. It only controls the
22660 method used to compute intermediate values. To control whether
22661 overflow checking is enabled or suppressed, use pragma @code{Suppress}
22662 or @code{Unsuppress} in the usual manner.
22664 @geindex -gnato? (gcc)
22666 @geindex -gnato?? (gcc)
22668 Additionally, a compiler switch @code{-gnato?} or @code{-gnato??}
22669 can be used to control the checking mode default (which can be subsequently
22670 overridden using pragmas).
22672 Here @code{?} is one of the digits @code{1} through @code{3}:
22677 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
22684 use base type for intermediate operations (@code{STRICT})
22692 minimize intermediate overflows (@code{MINIMIZED})
22700 eliminate intermediate overflows (@code{ELIMINATED})
22706 As with the pragma, if only one digit appears then it applies to all
22707 cases; if two digits are given, then the first applies outside
22708 assertions, and the second within assertions. Thus the equivalent
22709 of the example pragma above would be
22712 If no digits follow the @code{-gnato}, then it is equivalent to
22714 causing all intermediate operations to be computed using the base
22715 type (@code{STRICT} mode).
22717 @node Default Settings,Implementation Notes,Specifying the Desired Mode,Overflow Check Handling in GNAT
22718 @anchor{gnat_ugn/gnat_and_program_execution id49}@anchor{1c0}@anchor{gnat_ugn/gnat_and_program_execution default-settings}@anchor{1c1}
22719 @subsection Default Settings
22722 The default mode for overflow checks is
22731 which causes all computations both inside and outside assertions to use
22734 This retains compatibility with previous versions of
22735 GNAT which suppressed overflow checks by default and always
22736 used the base type for computation of intermediate results.
22738 @c Sphinx allows no emphasis within :index: role. As a workaround we
22739 @c point the index to "switch" and use emphasis for "-gnato".
22742 @geindex -gnato (gcc)
22743 switch @code{-gnato} (with no digits following)
22753 which causes overflow checking of all intermediate overflows
22754 both inside and outside assertions against the base type.
22756 The pragma @code{Suppress (Overflow_Check)} disables overflow
22757 checking, but it has no effect on the method used for computing
22758 intermediate results.
22760 The pragma @code{Unsuppress (Overflow_Check)} enables overflow
22761 checking, but it has no effect on the method used for computing
22762 intermediate results.
22764 @node Implementation Notes,,Default Settings,Overflow Check Handling in GNAT
22765 @anchor{gnat_ugn/gnat_and_program_execution implementation-notes}@anchor{1c2}@anchor{gnat_ugn/gnat_and_program_execution id50}@anchor{1c3}
22766 @subsection Implementation Notes
22769 In practice on typical 64-bit machines, the @code{MINIMIZED} mode is
22770 reasonably efficient, and can be generally used. It also helps
22771 to ensure compatibility with code imported from some other
22774 Setting all intermediate overflows checking (@code{CHECKED} mode)
22775 makes sense if you want to
22776 make sure that your code is compatible with any other possible
22777 Ada implementation. This may be useful in ensuring portability
22778 for code that is to be exported to some other compiler than GNAT.
22780 The Ada standard allows the reassociation of expressions at
22781 the same precedence level if no parentheses are present. For
22782 example, @code{A+B+C} parses as though it were @code{(A+B)+C}, but
22783 the compiler can reintepret this as @code{A+(B+C)}, possibly
22784 introducing or eliminating an overflow exception. The GNAT
22785 compiler never takes advantage of this freedom, and the
22786 expression @code{A+B+C} will be evaluated as @code{(A+B)+C}.
22787 If you need the other order, you can write the parentheses
22788 explicitly @code{A+(B+C)} and GNAT will respect this order.
22790 The use of @code{ELIMINATED} mode will cause the compiler to
22791 automatically include an appropriate arbitrary precision
22792 integer arithmetic package. The compiler will make calls
22793 to this package, though only in cases where it cannot be
22794 sure that @code{Long_Long_Integer} is sufficient to guard against
22795 intermediate overflows. This package does not use dynamic
22796 alllocation, but it does use the secondary stack, so an
22797 appropriate secondary stack package must be present (this
22798 is always true for standard full Ada, but may require
22799 specific steps for restricted run times such as ZFP).
22801 Although @code{ELIMINATED} mode causes expressions to use arbitrary
22802 precision arithmetic, avoiding overflow, the final result
22803 must be in an appropriate range. This is true even if the
22804 final result is of type @code{[Long_[Long_]]Integer'Base}, which
22805 still has the same bounds as its associated constrained
22808 Currently, the @code{ELIMINATED} mode is only available on target
22809 platforms for which @code{Long_Long_Integer} is 64-bits (nearly all GNAT
22812 @node Performing Dimensionality Analysis in GNAT,Stack Related Facilities,Overflow Check Handling in GNAT,GNAT and Program Execution
22813 @anchor{gnat_ugn/gnat_and_program_execution performing-dimensionality-analysis-in-gnat}@anchor{28}@anchor{gnat_ugn/gnat_and_program_execution id51}@anchor{16a}
22814 @section Performing Dimensionality Analysis in GNAT
22817 @geindex Dimensionality analysis
22819 The GNAT compiler supports dimensionality checking. The user can
22820 specify physical units for objects, and the compiler will verify that uses
22821 of these objects are compatible with their dimensions, in a fashion that is
22822 familiar to engineering practice. The dimensions of algebraic expressions
22823 (including powers with static exponents) are computed from their constituents.
22825 @geindex Dimension_System aspect
22827 @geindex Dimension aspect
22829 This feature depends on Ada 2012 aspect specifications, and is available from
22830 version 7.0.1 of GNAT onwards.
22831 The GNAT-specific aspect @code{Dimension_System}
22832 allows you to define a system of units; the aspect @code{Dimension}
22833 then allows the user to declare dimensioned quantities within a given system.
22834 (These aspects are described in the @emph{Implementation Defined Aspects}
22835 chapter of the @emph{GNAT Reference Manual}).
22837 The major advantage of this model is that it does not require the declaration of
22838 multiple operators for all possible combinations of types: it is only necessary
22839 to use the proper subtypes in object declarations.
22841 @geindex System.Dim.Mks package (GNAT library)
22843 @geindex MKS_Type type
22845 The simplest way to impose dimensionality checking on a computation is to make
22846 use of one of the instantiations of the package @code{System.Dim.Generic_Mks}, which
22847 are part of the GNAT library. This generic package defines a floating-point
22848 type @code{MKS_Type}, for which a sequence of dimension names are specified,
22849 together with their conventional abbreviations. The following should be read
22850 together with the full specification of the package, in file
22851 @code{s-digemk.ads}.
22855 @geindex s-digemk.ads file
22858 type Mks_Type is new Float_Type
22860 Dimension_System => (
22861 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
22862 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
22863 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
22864 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
22865 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"),
22866 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
22867 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
22871 The package then defines a series of subtypes that correspond to these
22872 conventional units. For example:
22877 subtype Length is Mks_Type
22879 Dimension => (Symbol => 'm', Meter => 1, others => 0);
22883 and similarly for @code{Mass}, @code{Time}, @code{Electric_Current},
22884 @code{Thermodynamic_Temperature}, @code{Amount_Of_Substance}, and
22885 @code{Luminous_Intensity} (the standard set of units of the SI system).
22887 The package also defines conventional names for values of each unit, for
22893 m : constant Length := 1.0;
22894 kg : constant Mass := 1.0;
22895 s : constant Time := 1.0;
22896 A : constant Electric_Current := 1.0;
22900 as well as useful multiples of these units:
22905 cm : constant Length := 1.0E-02;
22906 g : constant Mass := 1.0E-03;
22907 min : constant Time := 60.0;
22908 day : constant Time := 60.0 * 24.0 * min;
22913 There are three instantiations of @code{System.Dim.Generic_Mks} defined in the
22920 @code{System.Dim.Float_Mks} based on @code{Float} defined in @code{s-diflmk.ads}.
22923 @code{System.Dim.Long_Mks} based on @code{Long_Float} defined in @code{s-dilomk.ads}.
22926 @code{System.Dim.Mks} based on @code{Long_Long_Float} defined in @code{s-dimmks.ads}.
22929 Using one of these packages, you can then define a derived unit by providing
22930 the aspect that specifies its dimensions within the MKS system, as well as the
22931 string to be used for output of a value of that unit:
22936 subtype Acceleration is Mks_Type
22937 with Dimension => ("m/sec^2",
22944 Here is a complete example of use:
22949 with System.Dim.MKS; use System.Dim.Mks;
22950 with System.Dim.Mks_IO; use System.Dim.Mks_IO;
22951 with Text_IO; use Text_IO;
22952 procedure Free_Fall is
22953 subtype Acceleration is Mks_Type
22954 with Dimension => ("m/sec^2", 1, 0, -2, others => 0);
22955 G : constant acceleration := 9.81 * m / (s ** 2);
22956 T : Time := 10.0*s;
22960 Put ("Gravitational constant: ");
22961 Put (G, Aft => 2, Exp => 0); Put_Line ("");
22962 Distance := 0.5 * G * T ** 2;
22963 Put ("distance travelled in 10 seconds of free fall ");
22964 Put (Distance, Aft => 2, Exp => 0);
22970 Execution of this program yields:
22975 Gravitational constant: 9.81 m/sec^2
22976 distance travelled in 10 seconds of free fall 490.50 m
22980 However, incorrect assignments such as:
22986 Distance := 5.0 * kg;
22990 are rejected with the following diagnoses:
22996 >>> dimensions mismatch in assignment
22997 >>> left-hand side has dimension [L]
22998 >>> right-hand side is dimensionless
23000 Distance := 5.0 * kg:
23001 >>> dimensions mismatch in assignment
23002 >>> left-hand side has dimension [L]
23003 >>> right-hand side has dimension [M]
23007 The dimensions of an expression are properly displayed, even if there is
23008 no explicit subtype for it. If we add to the program:
23013 Put ("Final velocity: ");
23014 Put (G * T, Aft =>2, Exp =>0);
23019 then the output includes:
23024 Final velocity: 98.10 m.s**(-1)
23027 @geindex Dimensionable type
23029 @geindex Dimensioned subtype
23032 The type @code{Mks_Type} is said to be a @emph{dimensionable type} since it has a
23033 @code{Dimension_System} aspect, and the subtypes @code{Length}, @code{Mass}, etc.,
23034 are said to be @emph{dimensioned subtypes} since each one has a @code{Dimension}
23039 @geindex Dimension Vector (for a dimensioned subtype)
23041 @geindex Dimension aspect
23043 @geindex Dimension_System aspect
23046 The @code{Dimension} aspect of a dimensioned subtype @code{S} defines a mapping
23047 from the base type's Unit_Names to integer (or, more generally, rational)
23048 values. This mapping is the @emph{dimension vector} (also referred to as the
23049 @emph{dimensionality}) for that subtype, denoted by @code{DV(S)}, and thus for each
23050 object of that subtype. Intuitively, the value specified for each
23051 @code{Unit_Name} is the exponent associated with that unit; a zero value
23052 means that the unit is not used. For example:
23058 Acc : Acceleration;
23066 Here @code{DV(Acc)} = @code{DV(Acceleration)} =
23067 @code{(Meter=>1, Kilogram=>0, Second=>-2, Ampere=>0, Kelvin=>0, Mole=>0, Candela=>0)}.
23068 Symbolically, we can express this as @code{Meter / Second**2}.
23070 The dimension vector of an arithmetic expression is synthesized from the
23071 dimension vectors of its components, with compile-time dimensionality checks
23072 that help prevent mismatches such as using an @code{Acceleration} where a
23073 @code{Length} is required.
23075 The dimension vector of the result of an arithmetic expression @emph{expr}, or
23076 @code{DV(@emph{expr})}, is defined as follows, assuming conventional
23077 mathematical definitions for the vector operations that are used:
23083 If @emph{expr} is of the type @emph{universal_real}, or is not of a dimensioned subtype,
23084 then @emph{expr} is dimensionless; @code{DV(@emph{expr})} is the empty vector.
23087 @code{DV(@emph{op expr})}, where @emph{op} is a unary operator, is @code{DV(@emph{expr})}
23090 @code{DV(@emph{expr1 op expr2})} where @emph{op} is "+" or "-" is @code{DV(@emph{expr1})}
23091 provided that @code{DV(@emph{expr1})} = @code{DV(@emph{expr2})}.
23092 If this condition is not met then the construct is illegal.
23095 @code{DV(@emph{expr1} * @emph{expr2})} is @code{DV(@emph{expr1})} + @code{DV(@emph{expr2})},
23096 and @code{DV(@emph{expr1} / @emph{expr2})} = @code{DV(@emph{expr1})} - @code{DV(@emph{expr2})}.
23097 In this context if one of the @emph{expr}s is dimensionless then its empty
23098 dimension vector is treated as @code{(others => 0)}.
23101 @code{DV(@emph{expr} ** @emph{power})} is @emph{power} * @code{DV(@emph{expr})},
23102 provided that @emph{power} is a static rational value. If this condition is not
23103 met then the construct is illegal.
23106 Note that, by the above rules, it is illegal to use binary "+" or "-" to
23107 combine a dimensioned and dimensionless value. Thus an expression such as
23108 @code{acc-10.0} is illegal, where @code{acc} is an object of subtype
23109 @code{Acceleration}.
23111 The dimensionality checks for relationals use the same rules as
23112 for "+" and "-", except when comparing to a literal; thus
23130 and is thus illegal, but
23139 is accepted with a warning. Analogously a conditional expression requires the
23140 same dimension vector for each branch (with no exception for literals).
23142 The dimension vector of a type conversion @code{T(@emph{expr})} is defined
23143 as follows, based on the nature of @code{T}:
23149 If @code{T} is a dimensioned subtype then @code{DV(T(@emph{expr}))} is @code{DV(T)}
23150 provided that either @emph{expr} is dimensionless or
23151 @code{DV(T)} = @code{DV(@emph{expr})}. The conversion is illegal
23152 if @emph{expr} is dimensioned and @code{DV(@emph{expr})} /= @code{DV(T)}.
23153 Note that vector equality does not require that the corresponding
23154 Unit_Names be the same.
23156 As a consequence of the above rule, it is possible to convert between
23157 different dimension systems that follow the same international system
23158 of units, with the seven physical components given in the standard order
23159 (length, mass, time, etc.). Thus a length in meters can be converted to
23160 a length in inches (with a suitable conversion factor) but cannot be
23161 converted, for example, to a mass in pounds.
23164 If @code{T} is the base type for @emph{expr} (and the dimensionless root type of
23165 the dimension system), then @code{DV(T(@emph{expr}))} is @code{DV(expr)}.
23166 Thus, if @emph{expr} is of a dimensioned subtype of @code{T}, the conversion may
23167 be regarded as a "view conversion" that preserves dimensionality.
23169 This rule makes it possible to write generic code that can be instantiated
23170 with compatible dimensioned subtypes. The generic unit will contain
23171 conversions that will consequently be present in instantiations, but
23172 conversions to the base type will preserve dimensionality and make it
23173 possible to write generic code that is correct with respect to
23177 Otherwise (i.e., @code{T} is neither a dimensioned subtype nor a dimensionable
23178 base type), @code{DV(T(@emph{expr}))} is the empty vector. Thus a dimensioned
23179 value can be explicitly converted to a non-dimensioned subtype, which
23180 of course then escapes dimensionality analysis.
23183 The dimension vector for a type qualification @code{T'(@emph{expr})} is the same
23184 as for the type conversion @code{T(@emph{expr})}.
23186 An assignment statement
23195 requires @code{DV(Source)} = @code{DV(Target)}, and analogously for parameter
23196 passing (the dimension vector for the actual parameter must be equal to the
23197 dimension vector for the formal parameter).
23199 @node Stack Related Facilities,Memory Management Issues,Performing Dimensionality Analysis in GNAT,GNAT and Program Execution
23200 @anchor{gnat_ugn/gnat_and_program_execution stack-related-facilities}@anchor{29}@anchor{gnat_ugn/gnat_and_program_execution id52}@anchor{16b}
23201 @section Stack Related Facilities
23204 This section describes some useful tools associated with stack
23205 checking and analysis. In
23206 particular, it deals with dynamic and static stack usage measurements.
23209 * Stack Overflow Checking::
23210 * Static Stack Usage Analysis::
23211 * Dynamic Stack Usage Analysis::
23215 @node Stack Overflow Checking,Static Stack Usage Analysis,,Stack Related Facilities
23216 @anchor{gnat_ugn/gnat_and_program_execution id53}@anchor{1c4}@anchor{gnat_ugn/gnat_and_program_execution stack-overflow-checking}@anchor{f4}
23217 @subsection Stack Overflow Checking
23220 @geindex Stack Overflow Checking
23222 @geindex -fstack-check (gcc)
23224 For most operating systems, @code{gcc} does not perform stack overflow
23225 checking by default. This means that if the main environment task or
23226 some other task exceeds the available stack space, then unpredictable
23227 behavior will occur. Most native systems offer some level of protection by
23228 adding a guard page at the end of each task stack. This mechanism is usually
23229 not enough for dealing properly with stack overflow situations because
23230 a large local variable could "jump" above the guard page.
23231 Furthermore, when the
23232 guard page is hit, there may not be any space left on the stack for executing
23233 the exception propagation code. Enabling stack checking avoids
23236 To activate stack checking, compile all units with the @code{gcc} option
23237 @code{-fstack-check}. For example:
23242 $ gcc -c -fstack-check package1.adb
23246 Units compiled with this option will generate extra instructions to check
23247 that any use of the stack (for procedure calls or for declaring local
23248 variables in declare blocks) does not exceed the available stack space.
23249 If the space is exceeded, then a @code{Storage_Error} exception is raised.
23251 For declared tasks, the default stack size is defined by the GNAT runtime,
23252 whose size may be modified at bind time through the @code{-d} bind switch
23253 (@ref{11f,,Switches for gnatbind}). Task specific stack sizes may be set using the
23254 @code{Storage_Size} pragma.
23256 For the environment task, the stack size is determined by the operating system.
23257 Consequently, to modify the size of the environment task please refer to your
23258 operating system documentation.
23260 @node Static Stack Usage Analysis,Dynamic Stack Usage Analysis,Stack Overflow Checking,Stack Related Facilities
23261 @anchor{gnat_ugn/gnat_and_program_execution id54}@anchor{1c5}@anchor{gnat_ugn/gnat_and_program_execution static-stack-usage-analysis}@anchor{f5}
23262 @subsection Static Stack Usage Analysis
23265 @geindex Static Stack Usage Analysis
23267 @geindex -fstack-usage
23269 A unit compiled with @code{-fstack-usage} will generate an extra file
23271 the maximum amount of stack used, on a per-function basis.
23272 The file has the same
23273 basename as the target object file with a @code{.su} extension.
23274 Each line of this file is made up of three fields:
23280 The name of the function.
23286 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
23289 The second field corresponds to the size of the known part of the function
23292 The qualifier @code{static} means that the function frame size
23294 It usually means that all local variables have a static size.
23295 In this case, the second field is a reliable measure of the function stack
23298 The qualifier @code{dynamic} means that the function frame size is not static.
23299 It happens mainly when some local variables have a dynamic size. When this
23300 qualifier appears alone, the second field is not a reliable measure
23301 of the function stack analysis. When it is qualified with @code{bounded}, it
23302 means that the second field is a reliable maximum of the function stack
23305 A unit compiled with @code{-Wstack-usage} will issue a warning for each
23306 subprogram whose stack usage might be larger than the specified amount of
23307 bytes. The wording is in keeping with the qualifier documented above.
23309 @node Dynamic Stack Usage Analysis,,Static Stack Usage Analysis,Stack Related Facilities
23310 @anchor{gnat_ugn/gnat_and_program_execution id55}@anchor{1c6}@anchor{gnat_ugn/gnat_and_program_execution dynamic-stack-usage-analysis}@anchor{122}
23311 @subsection Dynamic Stack Usage Analysis
23314 It is possible to measure the maximum amount of stack used by a task, by
23315 adding a switch to @code{gnatbind}, as:
23320 $ gnatbind -u0 file
23324 With this option, at each task termination, its stack usage is output on
23326 Note that this switch is not compatible with tools like
23327 Valgrind and DrMemory; they will report errors.
23329 It is not always convenient to output the stack usage when the program
23330 is still running. Hence, it is possible to delay this output until program
23331 termination. for a given number of tasks specified as the argument of the
23332 @code{-u} option. For instance:
23337 $ gnatbind -u100 file
23341 will buffer the stack usage information of the first 100 tasks to terminate and
23342 output this info at program termination. Results are displayed in four
23348 Index | Task Name | Stack Size | Stack Usage
23358 @emph{Index} is a number associated with each task.
23361 @emph{Task Name} is the name of the task analyzed.
23364 @emph{Stack Size} is the maximum size for the stack.
23367 @emph{Stack Usage} is the measure done by the stack analyzer.
23368 In order to prevent overflow, the stack
23369 is not entirely analyzed, and it's not possible to know exactly how
23370 much has actually been used.
23373 By default the environment task stack, the stack that contains the main unit,
23374 is not processed. To enable processing of the environment task stack, the
23375 environment variable GNAT_STACK_LIMIT needs to be set to the maximum size of
23376 the environment task stack. This amount is given in kilobytes. For example:
23381 $ set GNAT_STACK_LIMIT 1600
23385 would specify to the analyzer that the environment task stack has a limit
23386 of 1.6 megabytes. Any stack usage beyond this will be ignored by the analysis.
23388 The package @code{GNAT.Task_Stack_Usage} provides facilities to get
23389 stack-usage reports at run time. See its body for the details.
23391 @node Memory Management Issues,,Stack Related Facilities,GNAT and Program Execution
23392 @anchor{gnat_ugn/gnat_and_program_execution id56}@anchor{16c}@anchor{gnat_ugn/gnat_and_program_execution memory-management-issues}@anchor{2a}
23393 @section Memory Management Issues
23396 This section describes some useful memory pools provided in the GNAT library
23397 and in particular the GNAT Debug Pool facility, which can be used to detect
23398 incorrect uses of access values (including 'dangling references').
23402 * Some Useful Memory Pools::
23403 * The GNAT Debug Pool Facility::
23407 @node Some Useful Memory Pools,The GNAT Debug Pool Facility,,Memory Management Issues
23408 @anchor{gnat_ugn/gnat_and_program_execution id57}@anchor{1c7}@anchor{gnat_ugn/gnat_and_program_execution some-useful-memory-pools}@anchor{1c8}
23409 @subsection Some Useful Memory Pools
23412 @geindex Memory Pool
23417 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
23418 storage pool. Allocations use the standard system call @code{malloc} while
23419 deallocations use the standard system call @code{free}. No reclamation is
23420 performed when the pool goes out of scope. For performance reasons, the
23421 standard default Ada allocators/deallocators do not use any explicit storage
23422 pools but if they did, they could use this storage pool without any change in
23423 behavior. That is why this storage pool is used when the user
23424 manages to make the default implicit allocator explicit as in this example:
23429 type T1 is access Something;
23430 -- no Storage pool is defined for T2
23432 type T2 is access Something_Else;
23433 for T2'Storage_Pool use T1'Storage_Pool;
23434 -- the above is equivalent to
23435 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
23439 The @code{System.Pool_Local} package offers the @code{Unbounded_Reclaim_Pool} storage
23440 pool. The allocation strategy is similar to @code{Pool_Local}
23441 except that the all
23442 storage allocated with this pool is reclaimed when the pool object goes out of
23443 scope. This pool provides a explicit mechanism similar to the implicit one
23444 provided by several Ada 83 compilers for allocations performed through a local
23445 access type and whose purpose was to reclaim memory when exiting the
23446 scope of a given local access. As an example, the following program does not
23447 leak memory even though it does not perform explicit deallocation:
23452 with System.Pool_Local;
23453 procedure Pooloc1 is
23454 procedure Internal is
23455 type A is access Integer;
23456 X : System.Pool_Local.Unbounded_Reclaim_Pool;
23457 for A'Storage_Pool use X;
23460 for I in 1 .. 50 loop
23465 for I in 1 .. 100 loop
23472 The @code{System.Pool_Size} package implements the @code{Stack_Bounded_Pool} used when
23473 @code{Storage_Size} is specified for an access type.
23474 The whole storage for the pool is
23475 allocated at once, usually on the stack at the point where the access type is
23476 elaborated. It is automatically reclaimed when exiting the scope where the
23477 access type is defined. This package is not intended to be used directly by the
23478 user and it is implicitly used for each such declaration:
23483 type T1 is access Something;
23484 for T1'Storage_Size use 10_000;
23488 @node The GNAT Debug Pool Facility,,Some Useful Memory Pools,Memory Management Issues
23489 @anchor{gnat_ugn/gnat_and_program_execution id58}@anchor{1c9}@anchor{gnat_ugn/gnat_and_program_execution the-gnat-debug-pool-facility}@anchor{1ca}
23490 @subsection The GNAT Debug Pool Facility
23493 @geindex Debug Pool
23497 @geindex memory corruption
23499 The use of unchecked deallocation and unchecked conversion can easily
23500 lead to incorrect memory references. The problems generated by such
23501 references are usually difficult to tackle because the symptoms can be
23502 very remote from the origin of the problem. In such cases, it is
23503 very helpful to detect the problem as early as possible. This is the
23504 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
23506 In order to use the GNAT specific debugging pool, the user must
23507 associate a debug pool object with each of the access types that may be
23508 related to suspected memory problems. See Ada Reference Manual 13.11.
23513 type Ptr is access Some_Type;
23514 Pool : GNAT.Debug_Pools.Debug_Pool;
23515 for Ptr'Storage_Pool use Pool;
23519 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
23520 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
23521 allow the user to redefine allocation and deallocation strategies. They
23522 also provide a checkpoint for each dereference, through the use of
23523 the primitive operation @code{Dereference} which is implicitly called at
23524 each dereference of an access value.
23526 Once an access type has been associated with a debug pool, operations on
23527 values of the type may raise four distinct exceptions,
23528 which correspond to four potential kinds of memory corruption:
23534 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
23537 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
23540 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
23543 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage}
23546 For types associated with a Debug_Pool, dynamic allocation is performed using
23547 the standard GNAT allocation routine. References to all allocated chunks of
23548 memory are kept in an internal dictionary. Several deallocation strategies are
23549 provided, whereupon the user can choose to release the memory to the system,
23550 keep it allocated for further invalid access checks, or fill it with an easily
23551 recognizable pattern for debug sessions. The memory pattern is the old IBM
23552 hexadecimal convention: @code{16#DEADBEEF#}.
23554 See the documentation in the file g-debpoo.ads for more information on the
23555 various strategies.
23557 Upon each dereference, a check is made that the access value denotes a
23558 properly allocated memory location. Here is a complete example of use of
23559 @code{Debug_Pools}, that includes typical instances of memory corruption:
23564 with Gnat.Io; use Gnat.Io;
23565 with Unchecked_Deallocation;
23566 with Unchecked_Conversion;
23567 with GNAT.Debug_Pools;
23568 with System.Storage_Elements;
23569 with Ada.Exceptions; use Ada.Exceptions;
23570 procedure Debug_Pool_Test is
23572 type T is access Integer;
23573 type U is access all T;
23575 P : GNAT.Debug_Pools.Debug_Pool;
23576 for T'Storage_Pool use P;
23578 procedure Free is new Unchecked_Deallocation (Integer, T);
23579 function UC is new Unchecked_Conversion (U, T);
23582 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
23592 Put_Line (Integer'Image(B.all));
23594 when E : others => Put_Line ("raised: " & Exception_Name (E));
23599 when E : others => Put_Line ("raised: " & Exception_Name (E));
23603 Put_Line (Integer'Image(B.all));
23605 when E : others => Put_Line ("raised: " & Exception_Name (E));
23610 when E : others => Put_Line ("raised: " & Exception_Name (E));
23613 end Debug_Pool_Test;
23617 The debug pool mechanism provides the following precise diagnostics on the
23618 execution of this erroneous program:
23624 Total allocated bytes : 0
23625 Total deallocated bytes : 0
23626 Current Water Mark: 0
23630 Total allocated bytes : 8
23631 Total deallocated bytes : 0
23632 Current Water Mark: 8
23635 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
23636 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
23637 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
23638 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
23640 Total allocated bytes : 8
23641 Total deallocated bytes : 4
23642 Current Water Mark: 4
23648 @c -- Non-breaking space in running text
23649 @c -- E.g. Ada |nbsp| 95
23651 @node Platform-Specific Information,Example of Binder Output File,GNAT and Program Execution,Top
23652 @anchor{gnat_ugn/platform_specific_information platform-specific-information}@anchor{d}@anchor{gnat_ugn/platform_specific_information doc}@anchor{1cb}@anchor{gnat_ugn/platform_specific_information id1}@anchor{1cc}
23653 @chapter Platform-Specific Information
23656 This appendix contains information relating to the implementation
23657 of run-time libraries on various platforms and also covers
23658 topics related to the GNAT implementation on Windows and Mac OS.
23661 * Run-Time Libraries::
23662 * Specifying a Run-Time Library::
23663 * GNU/Linux Topics::
23664 * Microsoft Windows Topics::
23669 @node Run-Time Libraries,Specifying a Run-Time Library,,Platform-Specific Information
23670 @anchor{gnat_ugn/platform_specific_information id2}@anchor{1cd}@anchor{gnat_ugn/platform_specific_information run-time-libraries}@anchor{2b}
23671 @section Run-Time Libraries
23674 @geindex Tasking and threads libraries
23676 @geindex Threads libraries and tasking
23678 @geindex Run-time libraries (platform-specific information)
23680 The GNAT run-time implementation may vary with respect to both the
23681 underlying threads library and the exception-handling scheme.
23682 For threads support, the default run-time will bind to the thread
23683 package of the underlying operating system.
23685 For exception handling, either or both of two models are supplied:
23689 @geindex Zero-Cost Exceptions
23691 @geindex ZCX (Zero-Cost Exceptions)
23698 @strong{Zero-Cost Exceptions} ("ZCX"),
23699 which uses binder-generated tables that
23700 are interrogated at run time to locate a handler.
23702 @geindex setjmp/longjmp Exception Model
23704 @geindex SJLJ (setjmp/longjmp Exception Model)
23707 @strong{setjmp / longjmp} ('SJLJ'),
23708 which uses dynamically-set data to establish
23709 the set of handlers
23712 Most programs should experience a substantial speed improvement by
23713 being compiled with a ZCX run-time.
23714 This is especially true for
23715 tasking applications or applications with many exception handlers.
23716 Note however that the ZCX run-time does not support asynchronous abort
23717 of tasks (@code{abort} and @code{select-then-abort} constructs) and will instead
23718 implement abort by polling points in the runtime. You can also add additional
23719 polling points explicitly if needed in your application via @code{pragma
23722 This section summarizes which combinations of threads and exception support
23723 are supplied on various GNAT platforms.
23726 * Summary of Run-Time Configurations::
23730 @node Summary of Run-Time Configurations,,,Run-Time Libraries
23731 @anchor{gnat_ugn/platform_specific_information summary-of-run-time-configurations}@anchor{1ce}@anchor{gnat_ugn/platform_specific_information id3}@anchor{1cf}
23732 @subsection Summary of Run-Time Configurations
23736 @multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx}
23793 native Win32 threads
23805 native Win32 threads
23830 @node Specifying a Run-Time Library,GNU/Linux Topics,Run-Time Libraries,Platform-Specific Information
23831 @anchor{gnat_ugn/platform_specific_information specifying-a-run-time-library}@anchor{1d0}@anchor{gnat_ugn/platform_specific_information id4}@anchor{1d1}
23832 @section Specifying a Run-Time Library
23835 The @code{adainclude} subdirectory containing the sources of the GNAT
23836 run-time library, and the @code{adalib} subdirectory containing the
23837 @code{ALI} files and the static and/or shared GNAT library, are located
23838 in the gcc target-dependent area:
23843 target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/
23847 As indicated above, on some platforms several run-time libraries are supplied.
23848 These libraries are installed in the target dependent area and
23849 contain a complete source and binary subdirectory. The detailed description
23850 below explains the differences between the different libraries in terms of
23851 their thread support.
23853 The default run-time library (when GNAT is installed) is @emph{rts-native}.
23854 This default run-time is selected by the means of soft links.
23855 For example on x86-linux:
23858 @c -- $(target-dir)
23860 @c -- +--- adainclude----------+
23862 @c -- +--- adalib-----------+ |
23864 @c -- +--- rts-native | |
23866 @c -- | +--- adainclude <---+
23868 @c -- | +--- adalib <----+
23870 @c -- +--- rts-sjlj
23872 @c -- +--- adainclude
23880 _______/ / \ \_________________
23883 ADAINCLUDE ADALIB rts-native rts-sjlj
23888 +-------------> adainclude adalib adainclude adalib
23891 +---------------------+
23893 Run-Time Library Directory Structure
23894 (Upper-case names and dotted/dashed arrows represent soft links)
23897 If the @emph{rts-sjlj} library is to be selected on a permanent basis,
23898 these soft links can be modified with the following commands:
23904 $ rm -f adainclude adalib
23905 $ ln -s rts-sjlj/adainclude adainclude
23906 $ ln -s rts-sjlj/adalib adalib
23910 Alternatively, you can specify @code{rts-sjlj/adainclude} in the file
23911 @code{$target/ada_source_path} and @code{rts-sjlj/adalib} in
23912 @code{$target/ada_object_path}.
23914 @geindex --RTS option
23916 Selecting another run-time library temporarily can be
23917 achieved by using the @code{--RTS} switch, e.g., @code{--RTS=sjlj}
23918 @anchor{gnat_ugn/platform_specific_information choosing-the-scheduling-policy}@anchor{1d2}
23919 @geindex SCHED_FIFO scheduling policy
23921 @geindex SCHED_RR scheduling policy
23923 @geindex SCHED_OTHER scheduling policy
23926 * Choosing the Scheduling Policy::
23930 @node Choosing the Scheduling Policy,,,Specifying a Run-Time Library
23931 @anchor{gnat_ugn/platform_specific_information id5}@anchor{1d3}
23932 @subsection Choosing the Scheduling Policy
23935 When using a POSIX threads implementation, you have a choice of several
23936 scheduling policies: @code{SCHED_FIFO}, @code{SCHED_RR} and @code{SCHED_OTHER}.
23938 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
23939 or @code{SCHED_RR} requires special (e.g., root) privileges.
23941 @geindex pragma Time_Slice
23943 @geindex -T0 option
23945 @geindex pragma Task_Dispatching_Policy
23947 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
23949 you can use one of the following:
23955 @code{pragma Time_Slice (0.0)}
23958 the corresponding binder option @code{-T0}
23961 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
23964 To specify @code{SCHED_RR},
23965 you should use @code{pragma Time_Slice} with a
23966 value greater than 0.0, or else use the corresponding @code{-T}
23969 To make sure a program is running as root, you can put something like
23970 this in a library package body in your application:
23975 function geteuid return Integer;
23976 pragma Import (C, geteuid, "geteuid");
23977 Ignore : constant Boolean :=
23978 (if geteuid = 0 then True else raise Program_Error with "must be root");
23982 It gets the effective user id, and if it's not 0 (i.e. root), it raises
23989 @node GNU/Linux Topics,Microsoft Windows Topics,Specifying a Run-Time Library,Platform-Specific Information
23990 @anchor{gnat_ugn/platform_specific_information id6}@anchor{1d4}@anchor{gnat_ugn/platform_specific_information gnu-linux-topics}@anchor{1d5}
23991 @section GNU/Linux Topics
23994 This section describes topics that are specific to GNU/Linux platforms.
23997 * Required Packages on GNU/Linux::
24001 @node Required Packages on GNU/Linux,,,GNU/Linux Topics
24002 @anchor{gnat_ugn/platform_specific_information id7}@anchor{1d6}@anchor{gnat_ugn/platform_specific_information required-packages-on-gnu-linux}@anchor{1d7}
24003 @subsection Required Packages on GNU/Linux
24006 GNAT requires the C library developer's package to be installed.
24007 The name of of that package depends on your GNU/Linux distribution:
24013 RedHat, SUSE: @code{glibc-devel};
24016 Debian, Ubuntu: @code{libc6-dev} (normally installed by default).
24019 If using the 32-bit version of GNAT on a 64-bit version of GNU/Linux,
24020 you'll need the 32-bit version of the following packages:
24026 RedHat, SUSE: @code{glibc.i686}, @code{glibc-devel.i686}, @code{ncurses-libs.i686}
24029 Debian, Ubuntu: @code{libc6:i386}, @code{libc6-dev:i386}, @code{lib32ncursesw5}
24032 Other GNU/Linux distributions might be choosing a different name
24033 for those packages.
24037 @node Microsoft Windows Topics,Mac OS Topics,GNU/Linux Topics,Platform-Specific Information
24038 @anchor{gnat_ugn/platform_specific_information microsoft-windows-topics}@anchor{2c}@anchor{gnat_ugn/platform_specific_information id8}@anchor{1d8}
24039 @section Microsoft Windows Topics
24042 This section describes topics that are specific to the Microsoft Windows
24047 * Using GNAT on Windows::
24048 * Using a network installation of GNAT::
24049 * CONSOLE and WINDOWS subsystems::
24050 * Temporary Files::
24051 * Disabling Command Line Argument Expansion::
24052 * Windows Socket Timeouts::
24053 * Mixed-Language Programming on Windows::
24054 * Windows Specific Add-Ons::
24058 @node Using GNAT on Windows,Using a network installation of GNAT,,Microsoft Windows Topics
24059 @anchor{gnat_ugn/platform_specific_information using-gnat-on-windows}@anchor{1d9}@anchor{gnat_ugn/platform_specific_information id9}@anchor{1da}
24060 @subsection Using GNAT on Windows
24063 One of the strengths of the GNAT technology is that its tool set
24064 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
24065 @code{gdb} debugger, etc.) is used in the same way regardless of the
24068 On Windows this tool set is complemented by a number of Microsoft-specific
24069 tools that have been provided to facilitate interoperability with Windows
24070 when this is required. With these tools:
24076 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
24080 You can use any Dynamically Linked Library (DLL) in your Ada code (both
24081 relocatable and non-relocatable DLLs are supported).
24084 You can build Ada DLLs for use in other applications. These applications
24085 can be written in a language other than Ada (e.g., C, C++, etc). Again both
24086 relocatable and non-relocatable Ada DLLs are supported.
24089 You can include Windows resources in your Ada application.
24092 You can use or create COM/DCOM objects.
24095 Immediately below are listed all known general GNAT-for-Windows restrictions.
24096 Other restrictions about specific features like Windows Resources and DLLs
24097 are listed in separate sections below.
24103 It is not possible to use @code{GetLastError} and @code{SetLastError}
24104 when tasking, protected records, or exceptions are used. In these
24105 cases, in order to implement Ada semantics, the GNAT run-time system
24106 calls certain Win32 routines that set the last error variable to 0 upon
24107 success. It should be possible to use @code{GetLastError} and
24108 @code{SetLastError} when tasking, protected record, and exception
24109 features are not used, but it is not guaranteed to work.
24112 It is not possible to link against Microsoft C++ libraries except for
24113 import libraries. Interfacing must be done by the mean of DLLs.
24116 It is possible to link against Microsoft C libraries. Yet the preferred
24117 solution is to use C/C++ compiler that comes with GNAT, since it
24118 doesn't require having two different development environments and makes the
24119 inter-language debugging experience smoother.
24122 When the compilation environment is located on FAT32 drives, users may
24123 experience recompilations of the source files that have not changed if
24124 Daylight Saving Time (DST) state has changed since the last time files
24125 were compiled. NTFS drives do not have this problem.
24128 No components of the GNAT toolset use any entries in the Windows
24129 registry. The only entries that can be created are file associations and
24130 PATH settings, provided the user has chosen to create them at installation
24131 time, as well as some minimal book-keeping information needed to correctly
24132 uninstall or integrate different GNAT products.
24135 @node Using a network installation of GNAT,CONSOLE and WINDOWS subsystems,Using GNAT on Windows,Microsoft Windows Topics
24136 @anchor{gnat_ugn/platform_specific_information id10}@anchor{1db}@anchor{gnat_ugn/platform_specific_information using-a-network-installation-of-gnat}@anchor{1dc}
24137 @subsection Using a network installation of GNAT
24140 Make sure the system on which GNAT is installed is accessible from the
24141 current machine, i.e., the install location is shared over the network.
24142 Shared resources are accessed on Windows by means of UNC paths, which
24143 have the format @code{\\\\server\\sharename\\path}
24145 In order to use such a network installation, simply add the UNC path of the
24146 @code{bin} directory of your GNAT installation in front of your PATH. For
24147 example, if GNAT is installed in @code{\GNAT} directory of a share location
24148 called @code{c-drive} on a machine @code{LOKI}, the following command will
24154 $ path \\loki\c-drive\gnat\bin;%path%`
24158 Be aware that every compilation using the network installation results in the
24159 transfer of large amounts of data across the network and will likely cause
24160 serious performance penalty.
24162 @node CONSOLE and WINDOWS subsystems,Temporary Files,Using a network installation of GNAT,Microsoft Windows Topics
24163 @anchor{gnat_ugn/platform_specific_information id11}@anchor{1dd}@anchor{gnat_ugn/platform_specific_information console-and-windows-subsystems}@anchor{1de}
24164 @subsection CONSOLE and WINDOWS subsystems
24167 @geindex CONSOLE Subsystem
24169 @geindex WINDOWS Subsystem
24173 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
24174 (which is the default subsystem) will always create a console when
24175 launching the application. This is not something desirable when the
24176 application has a Windows GUI. To get rid of this console the
24177 application must be using the @code{WINDOWS} subsystem. To do so
24178 the @code{-mwindows} linker option must be specified.
24183 $ gnatmake winprog -largs -mwindows
24187 @node Temporary Files,Disabling Command Line Argument Expansion,CONSOLE and WINDOWS subsystems,Microsoft Windows Topics
24188 @anchor{gnat_ugn/platform_specific_information id12}@anchor{1df}@anchor{gnat_ugn/platform_specific_information temporary-files}@anchor{1e0}
24189 @subsection Temporary Files
24192 @geindex Temporary files
24194 It is possible to control where temporary files gets created by setting
24197 @geindex environment variable; TMP
24198 @code{TMP} environment variable. The file will be created:
24204 Under the directory pointed to by the
24206 @geindex environment variable; TMP
24207 @code{TMP} environment variable if
24208 this directory exists.
24211 Under @code{c:\temp}, if the
24213 @geindex environment variable; TMP
24214 @code{TMP} environment variable is not
24215 set (or not pointing to a directory) and if this directory exists.
24218 Under the current working directory otherwise.
24221 This allows you to determine exactly where the temporary
24222 file will be created. This is particularly useful in networked
24223 environments where you may not have write access to some
24226 @node Disabling Command Line Argument Expansion,Windows Socket Timeouts,Temporary Files,Microsoft Windows Topics
24227 @anchor{gnat_ugn/platform_specific_information disabling-command-line-argument-expansion}@anchor{1e1}
24228 @subsection Disabling Command Line Argument Expansion
24231 @geindex Command Line Argument Expansion
24233 By default, an executable compiled for the Windows platform will do
24234 the following postprocessing on the arguments passed on the command
24241 If the argument contains the characters @code{*} and/or @code{?}, then
24242 file expansion will be attempted. For example, if the current directory
24243 contains @code{a.txt} and @code{b.txt}, then when calling:
24246 $ my_ada_program *.txt
24249 The following arguments will effectively be passed to the main program
24250 (for example when using @code{Ada.Command_Line.Argument}):
24253 Ada.Command_Line.Argument (1) -> "a.txt"
24254 Ada.Command_Line.Argument (2) -> "b.txt"
24258 Filename expansion can be disabled for a given argument by using single
24259 quotes. Thus, calling:
24262 $ my_ada_program '*.txt'
24268 Ada.Command_Line.Argument (1) -> "*.txt"
24272 Note that if the program is launched from a shell such as Cygwin Bash
24273 then quote removal might be performed by the shell.
24275 In some contexts it might be useful to disable this feature (for example if
24276 the program performs its own argument expansion). In order to do this, a C
24277 symbol needs to be defined and set to @code{0}. You can do this by
24278 adding the following code fragment in one of your Ada units:
24281 Do_Argv_Expansion : Integer := 0;
24282 pragma Export (C, Do_Argv_Expansion, "__gnat_do_argv_expansion");
24285 The results of previous examples will be respectively:
24288 Ada.Command_Line.Argument (1) -> "*.txt"
24294 Ada.Command_Line.Argument (1) -> "'*.txt'"
24297 @node Windows Socket Timeouts,Mixed-Language Programming on Windows,Disabling Command Line Argument Expansion,Microsoft Windows Topics
24298 @anchor{gnat_ugn/platform_specific_information windows-socket-timeouts}@anchor{1e2}
24299 @subsection Windows Socket Timeouts
24302 Microsoft Windows desktops older than @code{8.0} and Microsoft Windows Servers
24303 older than @code{2019} set a socket timeout 500 milliseconds longer than the value
24304 set by setsockopt with @code{SO_RCVTIMEO} and @code{SO_SNDTIMEO} options. The GNAT
24305 runtime makes a correction for the difference in the corresponding Windows
24306 versions. For Windows Server starting with version @code{2019}, the user must
24307 provide a manifest file for the GNAT runtime to be able to recognize that
24308 the Windows version does not need the timeout correction. The manifest file
24309 should be located in the same directory as the executable file, and its file
24310 name must match the executable name suffixed by @code{.manifest}. For example,
24311 if the executable name is @code{sock_wto.exe}, then the manifest file name
24312 has to be @code{sock_wto.exe.manifest}. The manifest file must contain at
24313 least the following data:
24316 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
24317 <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
24318 <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
24320 <!-- Windows Vista -->
24321 <supportedOS Id="@{e2011457-1546-43c5-a5fe-008deee3d3f0@}"/>
24323 <supportedOS Id="@{35138b9a-5d96-4fbd-8e2d-a2440225f93a@}"/>
24325 <supportedOS Id="@{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38@}"/>
24326 <!-- Windows 8.1 -->
24327 <supportedOS Id="@{1f676c76-80e1-4239-95bb-83d0f6d0da78@}"/>
24328 <!-- Windows 10 -->
24329 <supportedOS Id="@{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a@}"/>
24335 Without the manifest file, the socket timeout is going to be overcorrected on
24336 these Windows Server versions and the actual time is going to be 500
24337 milliseconds shorter than what was set with GNAT.Sockets.Set_Socket_Option.
24338 Note that on Microsoft Windows versions where correction is necessary, there
24339 is no way to set a socket timeout shorter than 500 ms. If a socket timeout
24340 shorter than 500 ms is needed on these Windows versions, a call to
24341 Check_Selector should be added before any socket read or write operations.
24343 @node Mixed-Language Programming on Windows,Windows Specific Add-Ons,Windows Socket Timeouts,Microsoft Windows Topics
24344 @anchor{gnat_ugn/platform_specific_information id13}@anchor{1e3}@anchor{gnat_ugn/platform_specific_information mixed-language-programming-on-windows}@anchor{1e4}
24345 @subsection Mixed-Language Programming on Windows
24348 Developing pure Ada applications on Windows is no different than on
24349 other GNAT-supported platforms. However, when developing or porting an
24350 application that contains a mix of Ada and C/C++, the choice of your
24351 Windows C/C++ development environment conditions your overall
24352 interoperability strategy.
24354 If you use @code{gcc} or Microsoft C to compile the non-Ada part of
24355 your application, there are no Windows-specific restrictions that
24356 affect the overall interoperability with your Ada code. If you do want
24357 to use the Microsoft tools for your C++ code, you have two choices:
24363 Encapsulate your C++ code in a DLL to be linked with your Ada
24364 application. In this case, use the Microsoft or whatever environment to
24365 build the DLL and use GNAT to build your executable
24366 (@ref{1e5,,Using DLLs with GNAT}).
24369 Or you can encapsulate your Ada code in a DLL to be linked with the
24370 other part of your application. In this case, use GNAT to build the DLL
24371 (@ref{1e6,,Building DLLs with GNAT Project files}) and use the Microsoft
24372 or whatever environment to build your executable.
24375 In addition to the description about C main in
24376 @ref{44,,Mixed Language Programming} section, if the C main uses a
24377 stand-alone library it is required on x86-windows to
24378 setup the SEH context. For this the C main must looks like this:
24384 extern void adainit (void);
24385 extern void adafinal (void);
24386 extern void __gnat_initialize(void*);
24387 extern void call_to_ada (void);
24389 int main (int argc, char *argv[])
24393 /* Initialize the SEH context */
24394 __gnat_initialize (&SEH);
24398 /* Then call Ada services in the stand-alone library */
24407 Note that this is not needed on x86_64-windows where the Windows
24408 native SEH support is used.
24411 * Windows Calling Conventions::
24412 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
24413 * Using DLLs with GNAT::
24414 * Building DLLs with GNAT Project files::
24415 * Building DLLs with GNAT::
24416 * Building DLLs with gnatdll::
24417 * Ada DLLs and Finalization::
24418 * Creating a Spec for Ada DLLs::
24419 * GNAT and Windows Resources::
24420 * Using GNAT DLLs from Microsoft Visual Studio Applications::
24421 * Debugging a DLL::
24422 * Setting Stack Size from gnatlink::
24423 * Setting Heap Size from gnatlink::
24427 @node Windows Calling Conventions,Introduction to Dynamic Link Libraries DLLs,,Mixed-Language Programming on Windows
24428 @anchor{gnat_ugn/platform_specific_information windows-calling-conventions}@anchor{1e7}@anchor{gnat_ugn/platform_specific_information id14}@anchor{1e8}
24429 @subsubsection Windows Calling Conventions
24436 This section pertain only to Win32. On Win64 there is a single native
24437 calling convention. All convention specifiers are ignored on this
24440 When a subprogram @code{F} (caller) calls a subprogram @code{G}
24441 (callee), there are several ways to push @code{G}'s parameters on the
24442 stack and there are several possible scenarios to clean up the stack
24443 upon @code{G}'s return. A calling convention is an agreed upon software
24444 protocol whereby the responsibilities between the caller (@code{F}) and
24445 the callee (@code{G}) are clearly defined. Several calling conventions
24446 are available for Windows:
24452 @code{C} (Microsoft defined)
24455 @code{Stdcall} (Microsoft defined)
24458 @code{Win32} (GNAT specific)
24461 @code{DLL} (GNAT specific)
24465 * C Calling Convention::
24466 * Stdcall Calling Convention::
24467 * Win32 Calling Convention::
24468 * DLL Calling Convention::
24472 @node C Calling Convention,Stdcall Calling Convention,,Windows Calling Conventions
24473 @anchor{gnat_ugn/platform_specific_information c-calling-convention}@anchor{1e9}@anchor{gnat_ugn/platform_specific_information id15}@anchor{1ea}
24474 @subsubsection @code{C} Calling Convention
24477 This is the default calling convention used when interfacing to C/C++
24478 routines compiled with either @code{gcc} or Microsoft Visual C++.
24480 In the @code{C} calling convention subprogram parameters are pushed on the
24481 stack by the caller from right to left. The caller itself is in charge of
24482 cleaning up the stack after the call. In addition, the name of a routine
24483 with @code{C} calling convention is mangled by adding a leading underscore.
24485 The name to use on the Ada side when importing (or exporting) a routine
24486 with @code{C} calling convention is the name of the routine. For
24487 instance the C function:
24492 int get_val (long);
24496 should be imported from Ada as follows:
24501 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24502 pragma Import (C, Get_Val, External_Name => "get_val");
24506 Note that in this particular case the @code{External_Name} parameter could
24507 have been omitted since, when missing, this parameter is taken to be the
24508 name of the Ada entity in lower case. When the @code{Link_Name} parameter
24509 is missing, as in the above example, this parameter is set to be the
24510 @code{External_Name} with a leading underscore.
24512 When importing a variable defined in C, you should always use the @code{C}
24513 calling convention unless the object containing the variable is part of a
24514 DLL (in which case you should use the @code{Stdcall} calling
24515 convention, @ref{1eb,,Stdcall Calling Convention}).
24517 @node Stdcall Calling Convention,Win32 Calling Convention,C Calling Convention,Windows Calling Conventions
24518 @anchor{gnat_ugn/platform_specific_information stdcall-calling-convention}@anchor{1eb}@anchor{gnat_ugn/platform_specific_information id16}@anchor{1ec}
24519 @subsubsection @code{Stdcall} Calling Convention
24522 This convention, which was the calling convention used for Pascal
24523 programs, is used by Microsoft for all the routines in the Win32 API for
24524 efficiency reasons. It must be used to import any routine for which this
24525 convention was specified.
24527 In the @code{Stdcall} calling convention subprogram parameters are pushed
24528 on the stack by the caller from right to left. The callee (and not the
24529 caller) is in charge of cleaning the stack on routine exit. In addition,
24530 the name of a routine with @code{Stdcall} calling convention is mangled by
24531 adding a leading underscore (as for the @code{C} calling convention) and a
24532 trailing @code{@@@emph{nn}}, where @code{nn} is the overall size (in
24533 bytes) of the parameters passed to the routine.
24535 The name to use on the Ada side when importing a C routine with a
24536 @code{Stdcall} calling convention is the name of the C routine. The leading
24537 underscore and trailing @code{@@@emph{nn}} are added automatically by
24538 the compiler. For instance the Win32 function:
24543 APIENTRY int get_val (long);
24547 should be imported from Ada as follows:
24552 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24553 pragma Import (Stdcall, Get_Val);
24554 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
24558 As for the @code{C} calling convention, when the @code{External_Name}
24559 parameter is missing, it is taken to be the name of the Ada entity in lower
24560 case. If instead of writing the above import pragma you write:
24565 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24566 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
24570 then the imported routine is @code{_retrieve_val@@4}. However, if instead
24571 of specifying the @code{External_Name} parameter you specify the
24572 @code{Link_Name} as in the following example:
24577 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24578 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
24582 then the imported routine is @code{retrieve_val}, that is, there is no
24583 decoration at all. No leading underscore and no Stdcall suffix
24584 @code{@@@emph{nn}}.
24586 This is especially important as in some special cases a DLL's entry
24587 point name lacks a trailing @code{@@@emph{nn}} while the exported
24588 name generated for a call has it.
24590 It is also possible to import variables defined in a DLL by using an
24591 import pragma for a variable. As an example, if a DLL contains a
24592 variable defined as:
24601 then, to access this variable from Ada you should write:
24606 My_Var : Interfaces.C.int;
24607 pragma Import (Stdcall, My_Var);
24611 Note that to ease building cross-platform bindings this convention
24612 will be handled as a @code{C} calling convention on non-Windows platforms.
24614 @node Win32 Calling Convention,DLL Calling Convention,Stdcall Calling Convention,Windows Calling Conventions
24615 @anchor{gnat_ugn/platform_specific_information win32-calling-convention}@anchor{1ed}@anchor{gnat_ugn/platform_specific_information id17}@anchor{1ee}
24616 @subsubsection @code{Win32} Calling Convention
24619 This convention, which is GNAT-specific is fully equivalent to the
24620 @code{Stdcall} calling convention described above.
24622 @node DLL Calling Convention,,Win32 Calling Convention,Windows Calling Conventions
24623 @anchor{gnat_ugn/platform_specific_information id18}@anchor{1ef}@anchor{gnat_ugn/platform_specific_information dll-calling-convention}@anchor{1f0}
24624 @subsubsection @code{DLL} Calling Convention
24627 This convention, which is GNAT-specific is fully equivalent to the
24628 @code{Stdcall} calling convention described above.
24630 @node Introduction to Dynamic Link Libraries DLLs,Using DLLs with GNAT,Windows Calling Conventions,Mixed-Language Programming on Windows
24631 @anchor{gnat_ugn/platform_specific_information id19}@anchor{1f1}@anchor{gnat_ugn/platform_specific_information introduction-to-dynamic-link-libraries-dlls}@anchor{1f2}
24632 @subsubsection Introduction to Dynamic Link Libraries (DLLs)
24637 A Dynamically Linked Library (DLL) is a library that can be shared by
24638 several applications running under Windows. A DLL can contain any number of
24639 routines and variables.
24641 One advantage of DLLs is that you can change and enhance them without
24642 forcing all the applications that depend on them to be relinked or
24643 recompiled. However, you should be aware than all calls to DLL routines are
24644 slower since, as you will understand below, such calls are indirect.
24646 To illustrate the remainder of this section, suppose that an application
24647 wants to use the services of a DLL @code{API.dll}. To use the services
24648 provided by @code{API.dll} you must statically link against the DLL or
24649 an import library which contains a jump table with an entry for each
24650 routine and variable exported by the DLL. In the Microsoft world this
24651 import library is called @code{API.lib}. When using GNAT this import
24652 library is called either @code{libAPI.dll.a}, @code{libapi.dll.a},
24653 @code{libAPI.a} or @code{libapi.a} (names are case insensitive).
24655 After you have linked your application with the DLL or the import library
24656 and you run your application, here is what happens:
24662 Your application is loaded into memory.
24665 The DLL @code{API.dll} is mapped into the address space of your
24666 application. This means that:
24672 The DLL will use the stack of the calling thread.
24675 The DLL will use the virtual address space of the calling process.
24678 The DLL will allocate memory from the virtual address space of the calling
24682 Handles (pointers) can be safely exchanged between routines in the DLL
24683 routines and routines in the application using the DLL.
24687 The entries in the jump table (from the import library @code{libAPI.dll.a}
24688 or @code{API.lib} or automatically created when linking against a DLL)
24689 which is part of your application are initialized with the addresses
24690 of the routines and variables in @code{API.dll}.
24693 If present in @code{API.dll}, routines @code{DllMain} or
24694 @code{DllMainCRTStartup} are invoked. These routines typically contain
24695 the initialization code needed for the well-being of the routines and
24696 variables exported by the DLL.
24699 There is an additional point which is worth mentioning. In the Windows
24700 world there are two kind of DLLs: relocatable and non-relocatable
24701 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
24702 in the target application address space. If the addresses of two
24703 non-relocatable DLLs overlap and these happen to be used by the same
24704 application, a conflict will occur and the application will run
24705 incorrectly. Hence, when possible, it is always preferable to use and
24706 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
24707 supported by GNAT. Note that the @code{-s} linker option (see GNU Linker
24708 User's Guide) removes the debugging symbols from the DLL but the DLL can
24709 still be relocated.
24711 As a side note, an interesting difference between Microsoft DLLs and
24712 Unix shared libraries, is the fact that on most Unix systems all public
24713 routines are exported by default in a Unix shared library, while under
24714 Windows it is possible (but not required) to list exported routines in
24715 a definition file (see @ref{1f3,,The Definition File}).
24717 @node Using DLLs with GNAT,Building DLLs with GNAT Project files,Introduction to Dynamic Link Libraries DLLs,Mixed-Language Programming on Windows
24718 @anchor{gnat_ugn/platform_specific_information id20}@anchor{1f4}@anchor{gnat_ugn/platform_specific_information using-dlls-with-gnat}@anchor{1e5}
24719 @subsubsection Using DLLs with GNAT
24722 To use the services of a DLL, say @code{API.dll}, in your Ada application
24729 The Ada spec for the routines and/or variables you want to access in
24730 @code{API.dll}. If not available this Ada spec must be built from the C/C++
24731 header files provided with the DLL.
24734 The import library (@code{libAPI.dll.a} or @code{API.lib}). As previously
24735 mentioned an import library is a statically linked library containing the
24736 import table which will be filled at load time to point to the actual
24737 @code{API.dll} routines. Sometimes you don't have an import library for the
24738 DLL you want to use. The following sections will explain how to build
24739 one. Note that this is optional.
24742 The actual DLL, @code{API.dll}.
24745 Once you have all the above, to compile an Ada application that uses the
24746 services of @code{API.dll} and whose main subprogram is @code{My_Ada_App},
24747 you simply issue the command
24752 $ gnatmake my_ada_app -largs -lAPI
24756 The argument @code{-largs -lAPI} at the end of the @code{gnatmake} command
24757 tells the GNAT linker to look for an import library. The linker will
24758 look for a library name in this specific order:
24764 @code{libAPI.dll.a}
24782 The first three are the GNU style import libraries. The third is the
24783 Microsoft style import libraries. The last two are the actual DLL names.
24785 Note that if the Ada package spec for @code{API.dll} contains the
24791 pragma Linker_Options ("-lAPI");
24795 you do not have to add @code{-largs -lAPI} at the end of the
24796 @code{gnatmake} command.
24798 If any one of the items above is missing you will have to create it
24799 yourself. The following sections explain how to do so using as an
24800 example a fictitious DLL called @code{API.dll}.
24803 * Creating an Ada Spec for the DLL Services::
24804 * Creating an Import Library::
24808 @node Creating an Ada Spec for the DLL Services,Creating an Import Library,,Using DLLs with GNAT
24809 @anchor{gnat_ugn/platform_specific_information id21}@anchor{1f5}@anchor{gnat_ugn/platform_specific_information creating-an-ada-spec-for-the-dll-services}@anchor{1f6}
24810 @subsubsection Creating an Ada Spec for the DLL Services
24813 A DLL typically comes with a C/C++ header file which provides the
24814 definitions of the routines and variables exported by the DLL. The Ada
24815 equivalent of this header file is a package spec that contains definitions
24816 for the imported entities. If the DLL you intend to use does not come with
24817 an Ada spec you have to generate one such spec yourself. For example if
24818 the header file of @code{API.dll} is a file @code{api.h} containing the
24819 following two definitions:
24829 then the equivalent Ada spec could be:
24834 with Interfaces.C.Strings;
24839 function Get (Str : C.Strings.Chars_Ptr) return C.int;
24842 pragma Import (C, Get);
24843 pragma Import (DLL, Some_Var);
24848 @node Creating an Import Library,,Creating an Ada Spec for the DLL Services,Using DLLs with GNAT
24849 @anchor{gnat_ugn/platform_specific_information id22}@anchor{1f7}@anchor{gnat_ugn/platform_specific_information creating-an-import-library}@anchor{1f8}
24850 @subsubsection Creating an Import Library
24853 @geindex Import library
24855 If a Microsoft-style import library @code{API.lib} or a GNAT-style
24856 import library @code{libAPI.dll.a} or @code{libAPI.a} is available
24857 with @code{API.dll} you can skip this section. You can also skip this
24858 section if @code{API.dll} or @code{libAPI.dll} is built with GNU tools
24859 as in this case it is possible to link directly against the
24860 DLL. Otherwise read on.
24862 @geindex Definition file
24863 @anchor{gnat_ugn/platform_specific_information the-definition-file}@anchor{1f3}
24864 @subsubheading The Definition File
24867 As previously mentioned, and unlike Unix systems, the list of symbols
24868 that are exported from a DLL must be provided explicitly in Windows.
24869 The main goal of a definition file is precisely that: list the symbols
24870 exported by a DLL. A definition file (usually a file with a @code{.def}
24871 suffix) has the following structure:
24876 [LIBRARY `@w{`}name`@w{`}]
24877 [DESCRIPTION `@w{`}string`@w{`}]
24879 `@w{`}symbol1`@w{`}
24880 `@w{`}symbol2`@w{`}
24888 @item @emph{LIBRARY name}
24890 This section, which is optional, gives the name of the DLL.
24892 @item @emph{DESCRIPTION string}
24894 This section, which is optional, gives a description string that will be
24895 embedded in the import library.
24897 @item @emph{EXPORTS}
24899 This section gives the list of exported symbols (procedures, functions or
24900 variables). For instance in the case of @code{API.dll} the @code{EXPORTS}
24901 section of @code{API.def} looks like:
24910 Note that you must specify the correct suffix (@code{@@@emph{nn}})
24911 (see @ref{1e7,,Windows Calling Conventions}) for a Stdcall
24912 calling convention function in the exported symbols list.
24914 There can actually be other sections in a definition file, but these
24915 sections are not relevant to the discussion at hand.
24916 @anchor{gnat_ugn/platform_specific_information create-def-file-automatically}@anchor{1f9}
24917 @subsubheading Creating a Definition File Automatically
24920 You can automatically create the definition file @code{API.def}
24921 (see @ref{1f3,,The Definition File}) from a DLL.
24922 For that use the @code{dlltool} program as follows:
24927 $ dlltool API.dll -z API.def --export-all-symbols
24930 Note that if some routines in the DLL have the @code{Stdcall} convention
24931 (@ref{1e7,,Windows Calling Conventions}) with stripped @code{@@@emph{nn}}
24932 suffix then you'll have to edit @code{api.def} to add it, and specify
24933 @code{-k} to @code{gnatdll} when creating the import library.
24935 Here are some hints to find the right @code{@@@emph{nn}} suffix.
24941 If you have the Microsoft import library (.lib), it is possible to get
24942 the right symbols by using Microsoft @code{dumpbin} tool (see the
24943 corresponding Microsoft documentation for further details).
24946 $ dumpbin /exports api.lib
24950 If you have a message about a missing symbol at link time the compiler
24951 tells you what symbol is expected. You just have to go back to the
24952 definition file and add the right suffix.
24955 @anchor{gnat_ugn/platform_specific_information gnat-style-import-library}@anchor{1fa}
24956 @subsubheading GNAT-Style Import Library
24959 To create a static import library from @code{API.dll} with the GNAT tools
24960 you should create the .def file, then use @code{gnatdll} tool
24961 (see @ref{1fb,,Using gnatdll}) as follows:
24966 $ gnatdll -e API.def -d API.dll
24969 @code{gnatdll} takes as input a definition file @code{API.def} and the
24970 name of the DLL containing the services listed in the definition file
24971 @code{API.dll}. The name of the static import library generated is
24972 computed from the name of the definition file as follows: if the
24973 definition file name is @code{xyz.def}, the import library name will
24974 be @code{libxyz.a}. Note that in the previous example option
24975 @code{-e} could have been removed because the name of the definition
24976 file (before the @code{.def} suffix) is the same as the name of the
24977 DLL (@ref{1fb,,Using gnatdll} for more information about @code{gnatdll}).
24979 @anchor{gnat_ugn/platform_specific_information msvs-style-import-library}@anchor{1fc}
24980 @subsubheading Microsoft-Style Import Library
24983 A Microsoft import library is needed only if you plan to make an
24984 Ada DLL available to applications developed with Microsoft
24985 tools (@ref{1e4,,Mixed-Language Programming on Windows}).
24987 To create a Microsoft-style import library for @code{API.dll} you
24988 should create the .def file, then build the actual import library using
24989 Microsoft's @code{lib} utility:
24994 $ lib -machine:IX86 -def:API.def -out:API.lib
24997 If you use the above command the definition file @code{API.def} must
24998 contain a line giving the name of the DLL:
25004 See the Microsoft documentation for further details about the usage of
25008 @node Building DLLs with GNAT Project files,Building DLLs with GNAT,Using DLLs with GNAT,Mixed-Language Programming on Windows
25009 @anchor{gnat_ugn/platform_specific_information id23}@anchor{1fd}@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat-project-files}@anchor{1e6}
25010 @subsubsection Building DLLs with GNAT Project files
25016 There is nothing specific to Windows in the build process.
25017 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
25018 chapter of the @emph{GPRbuild User's Guide}.
25020 Due to a system limitation, it is not possible under Windows to create threads
25021 when inside the @code{DllMain} routine which is used for auto-initialization
25022 of shared libraries, so it is not possible to have library level tasks in SALs.
25024 @node Building DLLs with GNAT,Building DLLs with gnatdll,Building DLLs with GNAT Project files,Mixed-Language Programming on Windows
25025 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat}@anchor{1fe}@anchor{gnat_ugn/platform_specific_information id24}@anchor{1ff}
25026 @subsubsection Building DLLs with GNAT
25032 This section explain how to build DLLs using the GNAT built-in DLL
25033 support. With the following procedure it is straight forward to build
25034 and use DLLs with GNAT.
25040 Building object files.
25041 The first step is to build all objects files that are to be included
25042 into the DLL. This is done by using the standard @code{gnatmake} tool.
25046 To build the DLL you must use the @code{gcc} @code{-shared} and
25047 @code{-shared-libgcc} options. It is quite simple to use this method:
25050 $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ...
25053 It is important to note that in this case all symbols found in the
25054 object files are automatically exported. It is possible to restrict
25055 the set of symbols to export by passing to @code{gcc} a definition
25056 file (see @ref{1f3,,The Definition File}).
25060 $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ...
25063 If you use a definition file you must export the elaboration procedures
25064 for every package that required one. Elaboration procedures are named
25065 using the package name followed by "_E".
25068 Preparing DLL to be used.
25069 For the DLL to be used by client programs the bodies must be hidden
25070 from it and the .ali set with read-only attribute. This is very important
25071 otherwise GNAT will recompile all packages and will not actually use
25072 the code in the DLL. For example:
25076 $ copy *.ads *.ali api.dll apilib
25077 $ attrib +R apilib\\*.ali
25081 At this point it is possible to use the DLL by directly linking
25082 against it. Note that you must use the GNAT shared runtime when using
25083 GNAT shared libraries. This is achieved by using the @code{-shared} binder
25089 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
25093 @node Building DLLs with gnatdll,Ada DLLs and Finalization,Building DLLs with GNAT,Mixed-Language Programming on Windows
25094 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnatdll}@anchor{200}@anchor{gnat_ugn/platform_specific_information id25}@anchor{201}
25095 @subsubsection Building DLLs with gnatdll
25101 Note that it is preferred to use GNAT Project files
25102 (@ref{1e6,,Building DLLs with GNAT Project files}) or the built-in GNAT
25103 DLL support (@ref{1fe,,Building DLLs with GNAT}) or to build DLLs.
25105 This section explains how to build DLLs containing Ada code using
25106 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
25107 remainder of this section.
25109 The steps required to build an Ada DLL that is to be used by Ada as well as
25110 non-Ada applications are as follows:
25116 You need to mark each Ada entity exported by the DLL with a @code{C} or
25117 @code{Stdcall} calling convention to avoid any Ada name mangling for the
25118 entities exported by the DLL
25119 (see @ref{202,,Exporting Ada Entities}). You can
25120 skip this step if you plan to use the Ada DLL only from Ada applications.
25123 Your Ada code must export an initialization routine which calls the routine
25124 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
25125 the Ada code in the DLL (@ref{203,,Ada DLLs and Elaboration}). The initialization
25126 routine exported by the Ada DLL must be invoked by the clients of the DLL
25127 to initialize the DLL.
25130 When useful, the DLL should also export a finalization routine which calls
25131 routine @code{adafinal} generated by @code{gnatbind} to perform the
25132 finalization of the Ada code in the DLL (@ref{204,,Ada DLLs and Finalization}).
25133 The finalization routine exported by the Ada DLL must be invoked by the
25134 clients of the DLL when the DLL services are no further needed.
25137 You must provide a spec for the services exported by the Ada DLL in each
25138 of the programming languages to which you plan to make the DLL available.
25141 You must provide a definition file listing the exported entities
25142 (@ref{1f3,,The Definition File}).
25145 Finally you must use @code{gnatdll} to produce the DLL and the import
25146 library (@ref{1fb,,Using gnatdll}).
25149 Note that a relocatable DLL stripped using the @code{strip}
25150 binutils tool will not be relocatable anymore. To build a DLL without
25151 debug information pass @code{-largs -s} to @code{gnatdll}. This
25152 restriction does not apply to a DLL built using a Library Project.
25153 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
25154 chapter of the @emph{GPRbuild User's Guide}.
25156 @c Limitations_When_Using_Ada_DLLs_from Ada:
25159 * Limitations When Using Ada DLLs from Ada::
25160 * Exporting Ada Entities::
25161 * Ada DLLs and Elaboration::
25165 @node Limitations When Using Ada DLLs from Ada,Exporting Ada Entities,,Building DLLs with gnatdll
25166 @anchor{gnat_ugn/platform_specific_information limitations-when-using-ada-dlls-from-ada}@anchor{205}
25167 @subsubsection Limitations When Using Ada DLLs from Ada
25170 When using Ada DLLs from Ada applications there is a limitation users
25171 should be aware of. Because on Windows the GNAT run-time is not in a DLL of
25172 its own, each Ada DLL includes a part of the GNAT run-time. Specifically,
25173 each Ada DLL includes the services of the GNAT run-time that are necessary
25174 to the Ada code inside the DLL. As a result, when an Ada program uses an
25175 Ada DLL there are two independent GNAT run-times: one in the Ada DLL and
25176 one in the main program.
25178 It is therefore not possible to exchange GNAT run-time objects between the
25179 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
25180 handles (e.g., @code{Text_IO.File_Type}), tasks types, protected objects
25183 It is completely safe to exchange plain elementary, array or record types,
25184 Windows object handles, etc.
25186 @node Exporting Ada Entities,Ada DLLs and Elaboration,Limitations When Using Ada DLLs from Ada,Building DLLs with gnatdll
25187 @anchor{gnat_ugn/platform_specific_information exporting-ada-entities}@anchor{202}@anchor{gnat_ugn/platform_specific_information id26}@anchor{206}
25188 @subsubsection Exporting Ada Entities
25191 @geindex Export table
25193 Building a DLL is a way to encapsulate a set of services usable from any
25194 application. As a result, the Ada entities exported by a DLL should be
25195 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
25196 any Ada name mangling. As an example here is an Ada package
25197 @code{API}, spec and body, exporting two procedures, a function, and a
25203 with Interfaces.C; use Interfaces;
25205 Count : C.int := 0;
25206 function Factorial (Val : C.int) return C.int;
25208 procedure Initialize_API;
25209 procedure Finalize_API;
25210 -- Initialization & Finalization routines. More in the next section.
25212 pragma Export (C, Initialize_API);
25213 pragma Export (C, Finalize_API);
25214 pragma Export (C, Count);
25215 pragma Export (C, Factorial);
25220 package body API is
25221 function Factorial (Val : C.int) return C.int is
25224 Count := Count + 1;
25225 for K in 1 .. Val loop
25231 procedure Initialize_API is
25233 pragma Import (C, Adainit);
25236 end Initialize_API;
25238 procedure Finalize_API is
25239 procedure Adafinal;
25240 pragma Import (C, Adafinal);
25248 If the Ada DLL you are building will only be used by Ada applications
25249 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
25250 convention. As an example, the previous package could be written as
25257 Count : Integer := 0;
25258 function Factorial (Val : Integer) return Integer;
25260 procedure Initialize_API;
25261 procedure Finalize_API;
25262 -- Initialization and Finalization routines.
25267 package body API is
25268 function Factorial (Val : Integer) return Integer is
25269 Fact : Integer := 1;
25271 Count := Count + 1;
25272 for K in 1 .. Val loop
25279 -- The remainder of this package body is unchanged.
25284 Note that if you do not export the Ada entities with a @code{C} or
25285 @code{Stdcall} convention you will have to provide the mangled Ada names
25286 in the definition file of the Ada DLL
25287 (@ref{207,,Creating the Definition File}).
25289 @node Ada DLLs and Elaboration,,Exporting Ada Entities,Building DLLs with gnatdll
25290 @anchor{gnat_ugn/platform_specific_information ada-dlls-and-elaboration}@anchor{203}@anchor{gnat_ugn/platform_specific_information id27}@anchor{208}
25291 @subsubsection Ada DLLs and Elaboration
25294 @geindex DLLs and elaboration
25296 The DLL that you are building contains your Ada code as well as all the
25297 routines in the Ada library that are needed by it. The first thing a
25298 user of your DLL must do is elaborate the Ada code
25299 (@ref{f,,Elaboration Order Handling in GNAT}).
25301 To achieve this you must export an initialization routine
25302 (@code{Initialize_API} in the previous example), which must be invoked
25303 before using any of the DLL services. This elaboration routine must call
25304 the Ada elaboration routine @code{adainit} generated by the GNAT binder
25305 (@ref{b4,,Binding with Non-Ada Main Programs}). See the body of
25306 @code{Initialize_Api} for an example. Note that the GNAT binder is
25307 automatically invoked during the DLL build process by the @code{gnatdll}
25308 tool (@ref{1fb,,Using gnatdll}).
25310 When a DLL is loaded, Windows systematically invokes a routine called
25311 @code{DllMain}. It would therefore be possible to call @code{adainit}
25312 directly from @code{DllMain} without having to provide an explicit
25313 initialization routine. Unfortunately, it is not possible to call
25314 @code{adainit} from the @code{DllMain} if your program has library level
25315 tasks because access to the @code{DllMain} entry point is serialized by
25316 the system (that is, only a single thread can execute 'through' it at a
25317 time), which means that the GNAT run-time will deadlock waiting for the
25318 newly created task to complete its initialization.
25320 @node Ada DLLs and Finalization,Creating a Spec for Ada DLLs,Building DLLs with gnatdll,Mixed-Language Programming on Windows
25321 @anchor{gnat_ugn/platform_specific_information id28}@anchor{209}@anchor{gnat_ugn/platform_specific_information ada-dlls-and-finalization}@anchor{204}
25322 @subsubsection Ada DLLs and Finalization
25325 @geindex DLLs and finalization
25327 When the services of an Ada DLL are no longer needed, the client code should
25328 invoke the DLL finalization routine, if available. The DLL finalization
25329 routine is in charge of releasing all resources acquired by the DLL. In the
25330 case of the Ada code contained in the DLL, this is achieved by calling
25331 routine @code{adafinal} generated by the GNAT binder
25332 (@ref{b4,,Binding with Non-Ada Main Programs}).
25333 See the body of @code{Finalize_Api} for an
25334 example. As already pointed out the GNAT binder is automatically invoked
25335 during the DLL build process by the @code{gnatdll} tool
25336 (@ref{1fb,,Using gnatdll}).
25338 @node Creating a Spec for Ada DLLs,GNAT and Windows Resources,Ada DLLs and Finalization,Mixed-Language Programming on Windows
25339 @anchor{gnat_ugn/platform_specific_information id29}@anchor{20a}@anchor{gnat_ugn/platform_specific_information creating-a-spec-for-ada-dlls}@anchor{20b}
25340 @subsubsection Creating a Spec for Ada DLLs
25343 To use the services exported by the Ada DLL from another programming
25344 language (e.g., C), you have to translate the specs of the exported Ada
25345 entities in that language. For instance in the case of @code{API.dll},
25346 the corresponding C header file could look like:
25351 extern int *_imp__count;
25352 #define count (*_imp__count)
25353 int factorial (int);
25357 It is important to understand that when building an Ada DLL to be used by
25358 other Ada applications, you need two different specs for the packages
25359 contained in the DLL: one for building the DLL and the other for using
25360 the DLL. This is because the @code{DLL} calling convention is needed to
25361 use a variable defined in a DLL, but when building the DLL, the variable
25362 must have either the @code{Ada} or @code{C} calling convention. As an
25363 example consider a DLL comprising the following package @code{API}:
25369 Count : Integer := 0;
25371 -- Remainder of the package omitted.
25376 After producing a DLL containing package @code{API}, the spec that
25377 must be used to import @code{API.Count} from Ada code outside of the
25385 pragma Import (DLL, Count);
25391 * Creating the Definition File::
25396 @node Creating the Definition File,Using gnatdll,,Creating a Spec for Ada DLLs
25397 @anchor{gnat_ugn/platform_specific_information creating-the-definition-file}@anchor{207}@anchor{gnat_ugn/platform_specific_information id30}@anchor{20c}
25398 @subsubsection Creating the Definition File
25401 The definition file is the last file needed to build the DLL. It lists
25402 the exported symbols. As an example, the definition file for a DLL
25403 containing only package @code{API} (where all the entities are exported
25404 with a @code{C} calling convention) is:
25417 If the @code{C} calling convention is missing from package @code{API},
25418 then the definition file contains the mangled Ada names of the above
25419 entities, which in this case are:
25428 api__initialize_api
25432 @node Using gnatdll,,Creating the Definition File,Creating a Spec for Ada DLLs
25433 @anchor{gnat_ugn/platform_specific_information using-gnatdll}@anchor{1fb}@anchor{gnat_ugn/platform_specific_information id31}@anchor{20d}
25434 @subsubsection Using @code{gnatdll}
25439 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
25440 and non-Ada sources that make up your DLL have been compiled.
25441 @code{gnatdll} is actually in charge of two distinct tasks: build the
25442 static import library for the DLL and the actual DLL. The form of the
25443 @code{gnatdll} command is
25448 $ gnatdll [ switches ] list-of-files [ -largs opts ]
25452 where @code{list-of-files} is a list of ALI and object files. The object
25453 file list must be the exact list of objects corresponding to the non-Ada
25454 sources whose services are to be included in the DLL. The ALI file list
25455 must be the exact list of ALI files for the corresponding Ada sources
25456 whose services are to be included in the DLL. If @code{list-of-files} is
25457 missing, only the static import library is generated.
25459 You may specify any of the following switches to @code{gnatdll}:
25463 @geindex -a (gnatdll)
25469 @item @code{-a[@emph{address}]}
25471 Build a non-relocatable DLL at @code{address}. If @code{address} is not
25472 specified the default address @code{0x11000000} will be used. By default,
25473 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
25474 advise the reader to build relocatable DLL.
25476 @geindex -b (gnatdll)
25478 @item @code{-b @emph{address}}
25480 Set the relocatable DLL base address. By default the address is
25483 @geindex -bargs (gnatdll)
25485 @item @code{-bargs @emph{opts}}
25487 Binder options. Pass @code{opts} to the binder.
25489 @geindex -d (gnatdll)
25491 @item @code{-d @emph{dllfile}}
25493 @code{dllfile} is the name of the DLL. This switch must be present for
25494 @code{gnatdll} to do anything. The name of the generated import library is
25495 obtained algorithmically from @code{dllfile} as shown in the following
25496 example: if @code{dllfile} is @code{xyz.dll}, the import library name is
25497 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
25498 by option @code{-e}) is obtained algorithmically from @code{dllfile}
25499 as shown in the following example:
25500 if @code{dllfile} is @code{xyz.dll}, the definition
25501 file used is @code{xyz.def}.
25503 @geindex -e (gnatdll)
25505 @item @code{-e @emph{deffile}}
25507 @code{deffile} is the name of the definition file.
25509 @geindex -g (gnatdll)
25513 Generate debugging information. This information is stored in the object
25514 file and copied from there to the final DLL file by the linker,
25515 where it can be read by the debugger. You must use the
25516 @code{-g} switch if you plan on using the debugger or the symbolic
25519 @geindex -h (gnatdll)
25523 Help mode. Displays @code{gnatdll} switch usage information.
25525 @geindex -I (gnatdll)
25527 @item @code{-I@emph{dir}}
25529 Direct @code{gnatdll} to search the @code{dir} directory for source and
25530 object files needed to build the DLL.
25531 (@ref{89,,Search Paths and the Run-Time Library (RTL)}).
25533 @geindex -k (gnatdll)
25537 Removes the @code{@@@emph{nn}} suffix from the import library's exported
25538 names, but keeps them for the link names. You must specify this
25539 option if you want to use a @code{Stdcall} function in a DLL for which
25540 the @code{@@@emph{nn}} suffix has been removed. This is the case for most
25541 of the Windows NT DLL for example. This option has no effect when
25542 @code{-n} option is specified.
25544 @geindex -l (gnatdll)
25546 @item @code{-l @emph{file}}
25548 The list of ALI and object files used to build the DLL are listed in
25549 @code{file}, instead of being given in the command line. Each line in
25550 @code{file} contains the name of an ALI or object file.
25552 @geindex -n (gnatdll)
25556 No Import. Do not create the import library.
25558 @geindex -q (gnatdll)
25562 Quiet mode. Do not display unnecessary messages.
25564 @geindex -v (gnatdll)
25568 Verbose mode. Display extra information.
25570 @geindex -largs (gnatdll)
25572 @item @code{-largs @emph{opts}}
25574 Linker options. Pass @code{opts} to the linker.
25577 @subsubheading @code{gnatdll} Example
25580 As an example the command to build a relocatable DLL from @code{api.adb}
25581 once @code{api.adb} has been compiled and @code{api.def} created is
25586 $ gnatdll -d api.dll api.ali
25590 The above command creates two files: @code{libapi.dll.a} (the import
25591 library) and @code{api.dll} (the actual DLL). If you want to create
25592 only the DLL, just type:
25597 $ gnatdll -d api.dll -n api.ali
25601 Alternatively if you want to create just the import library, type:
25606 $ gnatdll -d api.dll
25610 @subsubheading @code{gnatdll} behind the Scenes
25613 This section details the steps involved in creating a DLL. @code{gnatdll}
25614 does these steps for you. Unless you are interested in understanding what
25615 goes on behind the scenes, you should skip this section.
25617 We use the previous example of a DLL containing the Ada package @code{API},
25618 to illustrate the steps necessary to build a DLL. The starting point is a
25619 set of objects that will make up the DLL and the corresponding ALI
25620 files. In the case of this example this means that @code{api.o} and
25621 @code{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
25628 @code{gnatdll} builds the base file (@code{api.base}). A base file gives
25629 the information necessary to generate relocation information for the
25634 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
25637 In addition to the base file, the @code{gnatlink} command generates an
25638 output file @code{api.jnk} which can be discarded. The @code{-mdll} switch
25639 asks @code{gnatlink} to generate the routines @code{DllMain} and
25640 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
25641 is loaded into memory.
25644 @code{gnatdll} uses @code{dlltool} (see @ref{20e,,Using dlltool}) to build the
25645 export table (@code{api.exp}). The export table contains the relocation
25646 information in a form which can be used during the final link to ensure
25647 that the Windows loader is able to place the DLL anywhere in memory.
25650 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25651 --output-exp api.exp
25655 @code{gnatdll} builds the base file using the new export table. Note that
25656 @code{gnatbind} must be called once again since the binder generated file
25657 has been deleted during the previous call to @code{gnatlink}.
25661 $ gnatlink api -o api.jnk api.exp -mdll
25662 -Wl,--base-file,api.base
25666 @code{gnatdll} builds the new export table using the new base file and
25667 generates the DLL import library @code{libAPI.dll.a}.
25670 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25671 --output-exp api.exp --output-lib libAPI.a
25675 Finally @code{gnatdll} builds the relocatable DLL using the final export
25680 $ gnatlink api api.exp -o api.dll -mdll
25683 @anchor{gnat_ugn/platform_specific_information using-dlltool}@anchor{20e}
25684 @subsubheading Using @code{dlltool}
25687 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
25688 DLLs and static import libraries. This section summarizes the most
25689 common @code{dlltool} switches. The form of the @code{dlltool} command
25695 $ dlltool [`switches`]
25699 @code{dlltool} switches include:
25701 @geindex --base-file (dlltool)
25706 @item @code{--base-file @emph{basefile}}
25708 Read the base file @code{basefile} generated by the linker. This switch
25709 is used to create a relocatable DLL.
25712 @geindex --def (dlltool)
25717 @item @code{--def @emph{deffile}}
25719 Read the definition file.
25722 @geindex --dllname (dlltool)
25727 @item @code{--dllname @emph{name}}
25729 Gives the name of the DLL. This switch is used to embed the name of the
25730 DLL in the static import library generated by @code{dlltool} with switch
25731 @code{--output-lib}.
25734 @geindex -k (dlltool)
25741 Kill @code{@@@emph{nn}} from exported names
25742 (@ref{1e7,,Windows Calling Conventions}
25743 for a discussion about @code{Stdcall}-style symbols.
25746 @geindex --help (dlltool)
25751 @item @code{--help}
25753 Prints the @code{dlltool} switches with a concise description.
25756 @geindex --output-exp (dlltool)
25761 @item @code{--output-exp @emph{exportfile}}
25763 Generate an export file @code{exportfile}. The export file contains the
25764 export table (list of symbols in the DLL) and is used to create the DLL.
25767 @geindex --output-lib (dlltool)
25772 @item @code{--output-lib @emph{libfile}}
25774 Generate a static import library @code{libfile}.
25777 @geindex -v (dlltool)
25787 @geindex --as (dlltool)
25792 @item @code{--as @emph{assembler-name}}
25794 Use @code{assembler-name} as the assembler. The default is @code{as}.
25797 @node GNAT and Windows Resources,Using GNAT DLLs from Microsoft Visual Studio Applications,Creating a Spec for Ada DLLs,Mixed-Language Programming on Windows
25798 @anchor{gnat_ugn/platform_specific_information gnat-and-windows-resources}@anchor{20f}@anchor{gnat_ugn/platform_specific_information id32}@anchor{210}
25799 @subsubsection GNAT and Windows Resources
25805 Resources are an easy way to add Windows specific objects to your
25806 application. The objects that can be added as resources include:
25836 version information
25839 For example, a version information resource can be defined as follow and
25840 embedded into an executable or DLL:
25842 A version information resource can be used to embed information into an
25843 executable or a DLL. These information can be viewed using the file properties
25844 from the Windows Explorer. Here is an example of a version information
25851 FILEVERSION 1,0,0,0
25852 PRODUCTVERSION 1,0,0,0
25854 BLOCK "StringFileInfo"
25858 VALUE "CompanyName", "My Company Name"
25859 VALUE "FileDescription", "My application"
25860 VALUE "FileVersion", "1.0"
25861 VALUE "InternalName", "my_app"
25862 VALUE "LegalCopyright", "My Name"
25863 VALUE "OriginalFilename", "my_app.exe"
25864 VALUE "ProductName", "My App"
25865 VALUE "ProductVersion", "1.0"
25869 BLOCK "VarFileInfo"
25871 VALUE "Translation", 0x809, 1252
25877 The value @code{0809} (langID) is for the U.K English language and
25878 @code{04E4} (charsetID), which is equal to @code{1252} decimal, for
25881 This section explains how to build, compile and use resources. Note that this
25882 section does not cover all resource objects, for a complete description see
25883 the corresponding Microsoft documentation.
25886 * Building Resources::
25887 * Compiling Resources::
25888 * Using Resources::
25892 @node Building Resources,Compiling Resources,,GNAT and Windows Resources
25893 @anchor{gnat_ugn/platform_specific_information building-resources}@anchor{211}@anchor{gnat_ugn/platform_specific_information id33}@anchor{212}
25894 @subsubsection Building Resources
25900 A resource file is an ASCII file. By convention resource files have an
25901 @code{.rc} extension.
25902 The easiest way to build a resource file is to use Microsoft tools
25903 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
25904 @code{dlgedit.exe} to build dialogs.
25905 It is always possible to build an @code{.rc} file yourself by writing a
25908 It is not our objective to explain how to write a resource file. A
25909 complete description of the resource script language can be found in the
25910 Microsoft documentation.
25912 @node Compiling Resources,Using Resources,Building Resources,GNAT and Windows Resources
25913 @anchor{gnat_ugn/platform_specific_information compiling-resources}@anchor{213}@anchor{gnat_ugn/platform_specific_information id34}@anchor{214}
25914 @subsubsection Compiling Resources
25924 This section describes how to build a GNAT-compatible (COFF) object file
25925 containing the resources. This is done using the Resource Compiler
25926 @code{windres} as follows:
25931 $ windres -i myres.rc -o myres.o
25935 By default @code{windres} will run @code{gcc} to preprocess the @code{.rc}
25936 file. You can specify an alternate preprocessor (usually named
25937 @code{cpp.exe}) using the @code{windres} @code{--preprocessor}
25938 parameter. A list of all possible options may be obtained by entering
25939 the command @code{windres} @code{--help}.
25941 It is also possible to use the Microsoft resource compiler @code{rc.exe}
25942 to produce a @code{.res} file (binary resource file). See the
25943 corresponding Microsoft documentation for further details. In this case
25944 you need to use @code{windres} to translate the @code{.res} file to a
25945 GNAT-compatible object file as follows:
25950 $ windres -i myres.res -o myres.o
25954 @node Using Resources,,Compiling Resources,GNAT and Windows Resources
25955 @anchor{gnat_ugn/platform_specific_information using-resources}@anchor{215}@anchor{gnat_ugn/platform_specific_information id35}@anchor{216}
25956 @subsubsection Using Resources
25962 To include the resource file in your program just add the
25963 GNAT-compatible object file for the resource(s) to the linker
25964 arguments. With @code{gnatmake} this is done by using the @code{-largs}
25970 $ gnatmake myprog -largs myres.o
25974 @node Using GNAT DLLs from Microsoft Visual Studio Applications,Debugging a DLL,GNAT and Windows Resources,Mixed-Language Programming on Windows
25975 @anchor{gnat_ugn/platform_specific_information using-gnat-dll-from-msvs}@anchor{217}@anchor{gnat_ugn/platform_specific_information using-gnat-dlls-from-microsoft-visual-studio-applications}@anchor{218}
25976 @subsubsection Using GNAT DLLs from Microsoft Visual Studio Applications
25979 @geindex Microsoft Visual Studio
25980 @geindex use with GNAT DLLs
25982 This section describes a common case of mixed GNAT/Microsoft Visual Studio
25983 application development, where the main program is developed using MSVS, and
25984 is linked with a DLL developed using GNAT. Such a mixed application should
25985 be developed following the general guidelines outlined above; below is the
25986 cookbook-style sequence of steps to follow:
25992 First develop and build the GNAT shared library using a library project
25993 (let's assume the project is @code{mylib.gpr}, producing the library @code{libmylib.dll}):
25999 $ gprbuild -p mylib.gpr
26007 Produce a .def file for the symbols you need to interface with, either by
26008 hand or automatically with possibly some manual adjustments
26009 (see @ref{1f9,,Creating Definition File Automatically}):
26015 $ dlltool libmylib.dll -z libmylib.def --export-all-symbols
26023 Make sure that MSVS command-line tools are accessible on the path.
26026 Create the Microsoft-style import library (see @ref{1fc,,MSVS-Style Import Library}):
26032 $ lib -machine:IX86 -def:libmylib.def -out:libmylib.lib
26036 If you are using a 64-bit toolchain, the above becomes...
26041 $ lib -machine:X64 -def:libmylib.def -out:libmylib.lib
26055 $ cl /O2 /MD main.c libmylib.lib
26063 Before running the executable, make sure you have set the PATH to the DLL,
26064 or copy the DLL into into the directory containing the .exe.
26067 @node Debugging a DLL,Setting Stack Size from gnatlink,Using GNAT DLLs from Microsoft Visual Studio Applications,Mixed-Language Programming on Windows
26068 @anchor{gnat_ugn/platform_specific_information id36}@anchor{219}@anchor{gnat_ugn/platform_specific_information debugging-a-dll}@anchor{21a}
26069 @subsubsection Debugging a DLL
26072 @geindex DLL debugging
26074 Debugging a DLL is similar to debugging a standard program. But
26075 we have to deal with two different executable parts: the DLL and the
26076 program that uses it. We have the following four possibilities:
26082 The program and the DLL are built with GCC/GNAT.
26085 The program is built with foreign tools and the DLL is built with
26089 The program is built with GCC/GNAT and the DLL is built with
26093 In this section we address only cases one and two above.
26094 There is no point in trying to debug
26095 a DLL with GNU/GDB, if there is no GDB-compatible debugging
26096 information in it. To do so you must use a debugger compatible with the
26097 tools suite used to build the DLL.
26100 * Program and DLL Both Built with GCC/GNAT::
26101 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
26105 @node Program and DLL Both Built with GCC/GNAT,Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Debugging a DLL
26106 @anchor{gnat_ugn/platform_specific_information id37}@anchor{21b}@anchor{gnat_ugn/platform_specific_information program-and-dll-both-built-with-gcc-gnat}@anchor{21c}
26107 @subsubsection Program and DLL Both Built with GCC/GNAT
26110 This is the simplest case. Both the DLL and the program have @code{GDB}
26111 compatible debugging information. It is then possible to break anywhere in
26112 the process. Let's suppose here that the main procedure is named
26113 @code{ada_main} and that in the DLL there is an entry point named
26116 The DLL (@ref{1f2,,Introduction to Dynamic Link Libraries (DLLs)}) and
26117 program must have been built with the debugging information (see GNAT -g
26118 switch). Here are the step-by-step instructions for debugging it:
26124 Launch @code{GDB} on the main program.
26131 Start the program and stop at the beginning of the main procedure
26137 This step is required to be able to set a breakpoint inside the DLL. As long
26138 as the program is not run, the DLL is not loaded. This has the
26139 consequence that the DLL debugging information is also not loaded, so it is not
26140 possible to set a breakpoint in the DLL.
26143 Set a breakpoint inside the DLL
26146 (gdb) break ada_dll
26151 At this stage a breakpoint is set inside the DLL. From there on
26152 you can use the standard approach to debug the whole program
26153 (@ref{24,,Running and Debugging Ada Programs}).
26155 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Program and DLL Both Built with GCC/GNAT,Debugging a DLL
26156 @anchor{gnat_ugn/platform_specific_information program-built-with-foreign-tools-and-dll-built-with-gcc-gnat}@anchor{21d}@anchor{gnat_ugn/platform_specific_information id38}@anchor{21e}
26157 @subsubsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
26160 In this case things are slightly more complex because it is not possible to
26161 start the main program and then break at the beginning to load the DLL and the
26162 associated DLL debugging information. It is not possible to break at the
26163 beginning of the program because there is no @code{GDB} debugging information,
26164 and therefore there is no direct way of getting initial control. This
26165 section addresses this issue by describing some methods that can be used
26166 to break somewhere in the DLL to debug it.
26168 First suppose that the main procedure is named @code{main} (this is for
26169 example some C code built with Microsoft Visual C) and that there is a
26170 DLL named @code{test.dll} containing an Ada entry point named
26173 The DLL (see @ref{1f2,,Introduction to Dynamic Link Libraries (DLLs)}) must have
26174 been built with debugging information (see the GNAT @code{-g} option).
26176 @subsubheading Debugging the DLL Directly
26183 Find out the executable starting address
26186 $ objdump --file-header main.exe
26189 The starting address is reported on the last line. For example:
26192 main.exe: file format pei-i386
26193 architecture: i386, flags 0x0000010a:
26194 EXEC_P, HAS_DEBUG, D_PAGED
26195 start address 0x00401010
26199 Launch the debugger on the executable.
26206 Set a breakpoint at the starting address, and launch the program.
26209 $ (gdb) break *0x00401010
26213 The program will stop at the given address.
26216 Set a breakpoint on a DLL subroutine.
26219 (gdb) break ada_dll.adb:45
26222 Or if you want to break using a symbol on the DLL, you need first to
26223 select the Ada language (language used by the DLL).
26226 (gdb) set language ada
26227 (gdb) break ada_dll
26231 Continue the program.
26237 This will run the program until it reaches the breakpoint that has been
26238 set. From that point you can use the standard way to debug a program
26239 as described in (@ref{24,,Running and Debugging Ada Programs}).
26242 It is also possible to debug the DLL by attaching to a running process.
26244 @subsubheading Attaching to a Running Process
26247 @geindex DLL debugging
26248 @geindex attach to process
26250 With @code{GDB} it is always possible to debug a running process by
26251 attaching to it. It is possible to debug a DLL this way. The limitation
26252 of this approach is that the DLL must run long enough to perform the
26253 attach operation. It may be useful for instance to insert a time wasting
26254 loop in the code of the DLL to meet this criterion.
26260 Launch the main program @code{main.exe}.
26267 Use the Windows @emph{Task Manager} to find the process ID. Let's say
26268 that the process PID for @code{main.exe} is 208.
26278 Attach to the running process to be debugged.
26285 Load the process debugging information.
26288 (gdb) symbol-file main.exe
26292 Break somewhere in the DLL.
26295 (gdb) break ada_dll
26299 Continue process execution.
26306 This last step will resume the process execution, and stop at
26307 the breakpoint we have set. From there you can use the standard
26308 approach to debug a program as described in
26309 @ref{24,,Running and Debugging Ada Programs}.
26311 @node Setting Stack Size from gnatlink,Setting Heap Size from gnatlink,Debugging a DLL,Mixed-Language Programming on Windows
26312 @anchor{gnat_ugn/platform_specific_information setting-stack-size-from-gnatlink}@anchor{136}@anchor{gnat_ugn/platform_specific_information id39}@anchor{21f}
26313 @subsubsection Setting Stack Size from @code{gnatlink}
26316 It is possible to specify the program stack size at link time. On modern
26317 versions of Windows, starting with XP, this is mostly useful to set the size of
26318 the main stack (environment task). The other task stacks are set with pragma
26319 Storage_Size or with the @emph{gnatbind -d} command.
26321 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
26322 reserve size of individual tasks, the link-time stack size applies to all
26323 tasks, and pragma Storage_Size has no effect.
26324 In particular, Stack Overflow checks are made against this
26325 link-time specified size.
26327 This setting can be done with @code{gnatlink} using either of the following:
26333 @code{-Xlinker} linker option
26336 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
26339 This sets the stack reserve size to 0x10000 bytes and the stack commit
26340 size to 0x1000 bytes.
26343 @code{-Wl} linker option
26346 $ gnatlink hello -Wl,--stack=0x1000000
26349 This sets the stack reserve size to 0x1000000 bytes. Note that with
26350 @code{-Wl} option it is not possible to set the stack commit size
26351 because the comma is a separator for this option.
26354 @node Setting Heap Size from gnatlink,,Setting Stack Size from gnatlink,Mixed-Language Programming on Windows
26355 @anchor{gnat_ugn/platform_specific_information setting-heap-size-from-gnatlink}@anchor{137}@anchor{gnat_ugn/platform_specific_information id40}@anchor{220}
26356 @subsubsection Setting Heap Size from @code{gnatlink}
26359 Under Windows systems, it is possible to specify the program heap size from
26360 @code{gnatlink} using either of the following:
26366 @code{-Xlinker} linker option
26369 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
26372 This sets the heap reserve size to 0x10000 bytes and the heap commit
26373 size to 0x1000 bytes.
26376 @code{-Wl} linker option
26379 $ gnatlink hello -Wl,--heap=0x1000000
26382 This sets the heap reserve size to 0x1000000 bytes. Note that with
26383 @code{-Wl} option it is not possible to set the heap commit size
26384 because the comma is a separator for this option.
26387 @node Windows Specific Add-Ons,,Mixed-Language Programming on Windows,Microsoft Windows Topics
26388 @anchor{gnat_ugn/platform_specific_information windows-specific-add-ons}@anchor{221}@anchor{gnat_ugn/platform_specific_information win32-specific-addons}@anchor{222}
26389 @subsection Windows Specific Add-Ons
26392 This section describes the Windows specific add-ons.
26400 @node Win32Ada,wPOSIX,,Windows Specific Add-Ons
26401 @anchor{gnat_ugn/platform_specific_information win32ada}@anchor{223}@anchor{gnat_ugn/platform_specific_information id41}@anchor{224}
26402 @subsubsection Win32Ada
26405 Win32Ada is a binding for the Microsoft Win32 API. This binding can be
26406 easily installed from the provided installer. To use the Win32Ada
26407 binding you need to use a project file, and adding a single with_clause
26408 will give you full access to the Win32Ada binding sources and ensure
26409 that the proper libraries are passed to the linker.
26416 for Sources use ...;
26421 To build the application you just need to call gprbuild for the
26422 application's project, here p.gpr:
26431 @node wPOSIX,,Win32Ada,Windows Specific Add-Ons
26432 @anchor{gnat_ugn/platform_specific_information id42}@anchor{225}@anchor{gnat_ugn/platform_specific_information wposix}@anchor{226}
26433 @subsubsection wPOSIX
26436 wPOSIX is a minimal POSIX binding whose goal is to help with building
26437 cross-platforms applications. This binding is not complete though, as
26438 the Win32 API does not provide the necessary support for all POSIX APIs.
26440 To use the wPOSIX binding you need to use a project file, and adding
26441 a single with_clause will give you full access to the wPOSIX binding
26442 sources and ensure that the proper libraries are passed to the linker.
26449 for Sources use ...;
26454 To build the application you just need to call gprbuild for the
26455 application's project, here p.gpr:
26464 @node Mac OS Topics,,Microsoft Windows Topics,Platform-Specific Information
26465 @anchor{gnat_ugn/platform_specific_information mac-os-topics}@anchor{2d}@anchor{gnat_ugn/platform_specific_information id43}@anchor{227}
26466 @section Mac OS Topics
26471 This section describes topics that are specific to Apple's OS X
26475 * Codesigning the Debugger::
26479 @node Codesigning the Debugger,,,Mac OS Topics
26480 @anchor{gnat_ugn/platform_specific_information codesigning-the-debugger}@anchor{228}
26481 @subsection Codesigning the Debugger
26484 The Darwin Kernel requires the debugger to have special permissions
26485 before it is allowed to control other processes. These permissions
26486 are granted by codesigning the GDB executable. Without these
26487 permissions, the debugger will report error messages such as:
26490 Starting program: /x/y/foo
26491 Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5).
26492 (please check gdb is codesigned - see taskgated(8))
26495 Codesigning requires a certificate. The following procedure explains
26502 Start the Keychain Access application (in
26503 /Applications/Utilities/Keychain Access.app)
26506 Select the Keychain Access -> Certificate Assistant ->
26507 Create a Certificate... menu
26516 Choose a name for the new certificate (this procedure will use
26517 "gdb-cert" as an example)
26520 Set "Identity Type" to "Self Signed Root"
26523 Set "Certificate Type" to "Code Signing"
26526 Activate the "Let me override defaults" option
26530 Click several times on "Continue" until the "Specify a Location
26531 For The Certificate" screen appears, then set "Keychain" to "System"
26534 Click on "Continue" until the certificate is created
26537 Finally, in the view, double-click on the new certificate,
26538 and set "When using this certificate" to "Always Trust"
26541 Exit the Keychain Access application and restart the computer
26542 (this is unfortunately required)
26545 Once a certificate has been created, the debugger can be codesigned
26546 as follow. In a Terminal, run the following command:
26551 $ codesign -f -s "gdb-cert" <gnat_install_prefix>/bin/gdb
26555 where "gdb-cert" should be replaced by the actual certificate
26556 name chosen above, and <gnat_install_prefix> should be replaced by
26557 the location where you installed GNAT. Also, be sure that users are
26558 in the Unix group @code{_developer}.
26560 @node Example of Binder Output File,Elaboration Order Handling in GNAT,Platform-Specific Information,Top
26561 @anchor{gnat_ugn/example_of_binder_output example-of-binder-output-file}@anchor{e}@anchor{gnat_ugn/example_of_binder_output doc}@anchor{229}@anchor{gnat_ugn/example_of_binder_output id1}@anchor{22a}
26562 @chapter Example of Binder Output File
26565 @geindex Binder output (example)
26567 This Appendix displays the source code for the output file
26568 generated by @emph{gnatbind} for a simple 'Hello World' program.
26569 Comments have been added for clarification purposes.
26572 -- The package is called Ada_Main unless this name is actually used
26573 -- as a unit name in the partition, in which case some other unique
26578 package ada_main is
26579 pragma Warnings (Off);
26581 -- The main program saves the parameters (argument count,
26582 -- argument values, environment pointer) in global variables
26583 -- for later access by other units including
26584 -- Ada.Command_Line.
26586 gnat_argc : Integer;
26587 gnat_argv : System.Address;
26588 gnat_envp : System.Address;
26590 -- The actual variables are stored in a library routine. This
26591 -- is useful for some shared library situations, where there
26592 -- are problems if variables are not in the library.
26594 pragma Import (C, gnat_argc);
26595 pragma Import (C, gnat_argv);
26596 pragma Import (C, gnat_envp);
26598 -- The exit status is similarly an external location
26600 gnat_exit_status : Integer;
26601 pragma Import (C, gnat_exit_status);
26603 GNAT_Version : constant String :=
26604 "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL;
26605 pragma Export (C, GNAT_Version, "__gnat_version");
26607 Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL;
26608 pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name");
26610 -- This is the generated adainit routine that performs
26611 -- initialization at the start of execution. In the case
26612 -- where Ada is the main program, this main program makes
26613 -- a call to adainit at program startup.
26616 pragma Export (C, adainit, "adainit");
26618 -- This is the generated adafinal routine that performs
26619 -- finalization at the end of execution. In the case where
26620 -- Ada is the main program, this main program makes a call
26621 -- to adafinal at program termination.
26623 procedure adafinal;
26624 pragma Export (C, adafinal, "adafinal");
26626 -- This routine is called at the start of execution. It is
26627 -- a dummy routine that is used by the debugger to breakpoint
26628 -- at the start of execution.
26630 -- This is the actual generated main program (it would be
26631 -- suppressed if the no main program switch were used). As
26632 -- required by standard system conventions, this program has
26633 -- the external name main.
26637 argv : System.Address;
26638 envp : System.Address)
26640 pragma Export (C, main, "main");
26642 -- The following set of constants give the version
26643 -- identification values for every unit in the bound
26644 -- partition. This identification is computed from all
26645 -- dependent semantic units, and corresponds to the
26646 -- string that would be returned by use of the
26647 -- Body_Version or Version attributes.
26649 -- The following Export pragmas export the version numbers
26650 -- with symbolic names ending in B (for body) or S
26651 -- (for spec) so that they can be located in a link. The
26652 -- information provided here is sufficient to track down
26653 -- the exact versions of units used in a given build.
26655 type Version_32 is mod 2 ** 32;
26656 u00001 : constant Version_32 := 16#8ad6e54a#;
26657 pragma Export (C, u00001, "helloB");
26658 u00002 : constant Version_32 := 16#fbff4c67#;
26659 pragma Export (C, u00002, "system__standard_libraryB");
26660 u00003 : constant Version_32 := 16#1ec6fd90#;
26661 pragma Export (C, u00003, "system__standard_libraryS");
26662 u00004 : constant Version_32 := 16#3ffc8e18#;
26663 pragma Export (C, u00004, "adaS");
26664 u00005 : constant Version_32 := 16#28f088c2#;
26665 pragma Export (C, u00005, "ada__text_ioB");
26666 u00006 : constant Version_32 := 16#f372c8ac#;
26667 pragma Export (C, u00006, "ada__text_ioS");
26668 u00007 : constant Version_32 := 16#2c143749#;
26669 pragma Export (C, u00007, "ada__exceptionsB");
26670 u00008 : constant Version_32 := 16#f4f0cce8#;
26671 pragma Export (C, u00008, "ada__exceptionsS");
26672 u00009 : constant Version_32 := 16#a46739c0#;
26673 pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB");
26674 u00010 : constant Version_32 := 16#3aac8c92#;
26675 pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS");
26676 u00011 : constant Version_32 := 16#1d274481#;
26677 pragma Export (C, u00011, "systemS");
26678 u00012 : constant Version_32 := 16#a207fefe#;
26679 pragma Export (C, u00012, "system__soft_linksB");
26680 u00013 : constant Version_32 := 16#467d9556#;
26681 pragma Export (C, u00013, "system__soft_linksS");
26682 u00014 : constant Version_32 := 16#b01dad17#;
26683 pragma Export (C, u00014, "system__parametersB");
26684 u00015 : constant Version_32 := 16#630d49fe#;
26685 pragma Export (C, u00015, "system__parametersS");
26686 u00016 : constant Version_32 := 16#b19b6653#;
26687 pragma Export (C, u00016, "system__secondary_stackB");
26688 u00017 : constant Version_32 := 16#b6468be8#;
26689 pragma Export (C, u00017, "system__secondary_stackS");
26690 u00018 : constant Version_32 := 16#39a03df9#;
26691 pragma Export (C, u00018, "system__storage_elementsB");
26692 u00019 : constant Version_32 := 16#30e40e85#;
26693 pragma Export (C, u00019, "system__storage_elementsS");
26694 u00020 : constant Version_32 := 16#41837d1e#;
26695 pragma Export (C, u00020, "system__stack_checkingB");
26696 u00021 : constant Version_32 := 16#93982f69#;
26697 pragma Export (C, u00021, "system__stack_checkingS");
26698 u00022 : constant Version_32 := 16#393398c1#;
26699 pragma Export (C, u00022, "system__exception_tableB");
26700 u00023 : constant Version_32 := 16#b33e2294#;
26701 pragma Export (C, u00023, "system__exception_tableS");
26702 u00024 : constant Version_32 := 16#ce4af020#;
26703 pragma Export (C, u00024, "system__exceptionsB");
26704 u00025 : constant Version_32 := 16#75442977#;
26705 pragma Export (C, u00025, "system__exceptionsS");
26706 u00026 : constant Version_32 := 16#37d758f1#;
26707 pragma Export (C, u00026, "system__exceptions__machineS");
26708 u00027 : constant Version_32 := 16#b895431d#;
26709 pragma Export (C, u00027, "system__exceptions_debugB");
26710 u00028 : constant Version_32 := 16#aec55d3f#;
26711 pragma Export (C, u00028, "system__exceptions_debugS");
26712 u00029 : constant Version_32 := 16#570325c8#;
26713 pragma Export (C, u00029, "system__img_intB");
26714 u00030 : constant Version_32 := 16#1ffca443#;
26715 pragma Export (C, u00030, "system__img_intS");
26716 u00031 : constant Version_32 := 16#b98c3e16#;
26717 pragma Export (C, u00031, "system__tracebackB");
26718 u00032 : constant Version_32 := 16#831a9d5a#;
26719 pragma Export (C, u00032, "system__tracebackS");
26720 u00033 : constant Version_32 := 16#9ed49525#;
26721 pragma Export (C, u00033, "system__traceback_entriesB");
26722 u00034 : constant Version_32 := 16#1d7cb2f1#;
26723 pragma Export (C, u00034, "system__traceback_entriesS");
26724 u00035 : constant Version_32 := 16#8c33a517#;
26725 pragma Export (C, u00035, "system__wch_conB");
26726 u00036 : constant Version_32 := 16#065a6653#;
26727 pragma Export (C, u00036, "system__wch_conS");
26728 u00037 : constant Version_32 := 16#9721e840#;
26729 pragma Export (C, u00037, "system__wch_stwB");
26730 u00038 : constant Version_32 := 16#2b4b4a52#;
26731 pragma Export (C, u00038, "system__wch_stwS");
26732 u00039 : constant Version_32 := 16#92b797cb#;
26733 pragma Export (C, u00039, "system__wch_cnvB");
26734 u00040 : constant Version_32 := 16#09eddca0#;
26735 pragma Export (C, u00040, "system__wch_cnvS");
26736 u00041 : constant Version_32 := 16#6033a23f#;
26737 pragma Export (C, u00041, "interfacesS");
26738 u00042 : constant Version_32 := 16#ece6fdb6#;
26739 pragma Export (C, u00042, "system__wch_jisB");
26740 u00043 : constant Version_32 := 16#899dc581#;
26741 pragma Export (C, u00043, "system__wch_jisS");
26742 u00044 : constant Version_32 := 16#10558b11#;
26743 pragma Export (C, u00044, "ada__streamsB");
26744 u00045 : constant Version_32 := 16#2e6701ab#;
26745 pragma Export (C, u00045, "ada__streamsS");
26746 u00046 : constant Version_32 := 16#db5c917c#;
26747 pragma Export (C, u00046, "ada__io_exceptionsS");
26748 u00047 : constant Version_32 := 16#12c8cd7d#;
26749 pragma Export (C, u00047, "ada__tagsB");
26750 u00048 : constant Version_32 := 16#ce72c228#;
26751 pragma Export (C, u00048, "ada__tagsS");
26752 u00049 : constant Version_32 := 16#c3335bfd#;
26753 pragma Export (C, u00049, "system__htableB");
26754 u00050 : constant Version_32 := 16#99e5f76b#;
26755 pragma Export (C, u00050, "system__htableS");
26756 u00051 : constant Version_32 := 16#089f5cd0#;
26757 pragma Export (C, u00051, "system__string_hashB");
26758 u00052 : constant Version_32 := 16#3bbb9c15#;
26759 pragma Export (C, u00052, "system__string_hashS");
26760 u00053 : constant Version_32 := 16#807fe041#;
26761 pragma Export (C, u00053, "system__unsigned_typesS");
26762 u00054 : constant Version_32 := 16#d27be59e#;
26763 pragma Export (C, u00054, "system__val_lluB");
26764 u00055 : constant Version_32 := 16#fa8db733#;
26765 pragma Export (C, u00055, "system__val_lluS");
26766 u00056 : constant Version_32 := 16#27b600b2#;
26767 pragma Export (C, u00056, "system__val_utilB");
26768 u00057 : constant Version_32 := 16#b187f27f#;
26769 pragma Export (C, u00057, "system__val_utilS");
26770 u00058 : constant Version_32 := 16#d1060688#;
26771 pragma Export (C, u00058, "system__case_utilB");
26772 u00059 : constant Version_32 := 16#392e2d56#;
26773 pragma Export (C, u00059, "system__case_utilS");
26774 u00060 : constant Version_32 := 16#84a27f0d#;
26775 pragma Export (C, u00060, "interfaces__c_streamsB");
26776 u00061 : constant Version_32 := 16#8bb5f2c0#;
26777 pragma Export (C, u00061, "interfaces__c_streamsS");
26778 u00062 : constant Version_32 := 16#6db6928f#;
26779 pragma Export (C, u00062, "system__crtlS");
26780 u00063 : constant Version_32 := 16#4e6a342b#;
26781 pragma Export (C, u00063, "system__file_ioB");
26782 u00064 : constant Version_32 := 16#ba56a5e4#;
26783 pragma Export (C, u00064, "system__file_ioS");
26784 u00065 : constant Version_32 := 16#b7ab275c#;
26785 pragma Export (C, u00065, "ada__finalizationB");
26786 u00066 : constant Version_32 := 16#19f764ca#;
26787 pragma Export (C, u00066, "ada__finalizationS");
26788 u00067 : constant Version_32 := 16#95817ed8#;
26789 pragma Export (C, u00067, "system__finalization_rootB");
26790 u00068 : constant Version_32 := 16#52d53711#;
26791 pragma Export (C, u00068, "system__finalization_rootS");
26792 u00069 : constant Version_32 := 16#769e25e6#;
26793 pragma Export (C, u00069, "interfaces__cB");
26794 u00070 : constant Version_32 := 16#4a38bedb#;
26795 pragma Export (C, u00070, "interfaces__cS");
26796 u00071 : constant Version_32 := 16#07e6ee66#;
26797 pragma Export (C, u00071, "system__os_libB");
26798 u00072 : constant Version_32 := 16#d7b69782#;
26799 pragma Export (C, u00072, "system__os_libS");
26800 u00073 : constant Version_32 := 16#1a817b8e#;
26801 pragma Export (C, u00073, "system__stringsB");
26802 u00074 : constant Version_32 := 16#639855e7#;
26803 pragma Export (C, u00074, "system__stringsS");
26804 u00075 : constant Version_32 := 16#e0b8de29#;
26805 pragma Export (C, u00075, "system__file_control_blockS");
26806 u00076 : constant Version_32 := 16#b5b2aca1#;
26807 pragma Export (C, u00076, "system__finalization_mastersB");
26808 u00077 : constant Version_32 := 16#69316dc1#;
26809 pragma Export (C, u00077, "system__finalization_mastersS");
26810 u00078 : constant Version_32 := 16#57a37a42#;
26811 pragma Export (C, u00078, "system__address_imageB");
26812 u00079 : constant Version_32 := 16#bccbd9bb#;
26813 pragma Export (C, u00079, "system__address_imageS");
26814 u00080 : constant Version_32 := 16#7268f812#;
26815 pragma Export (C, u00080, "system__img_boolB");
26816 u00081 : constant Version_32 := 16#e8fe356a#;
26817 pragma Export (C, u00081, "system__img_boolS");
26818 u00082 : constant Version_32 := 16#d7aac20c#;
26819 pragma Export (C, u00082, "system__ioB");
26820 u00083 : constant Version_32 := 16#8365b3ce#;
26821 pragma Export (C, u00083, "system__ioS");
26822 u00084 : constant Version_32 := 16#6d4d969a#;
26823 pragma Export (C, u00084, "system__storage_poolsB");
26824 u00085 : constant Version_32 := 16#e87cc305#;
26825 pragma Export (C, u00085, "system__storage_poolsS");
26826 u00086 : constant Version_32 := 16#e34550ca#;
26827 pragma Export (C, u00086, "system__pool_globalB");
26828 u00087 : constant Version_32 := 16#c88d2d16#;
26829 pragma Export (C, u00087, "system__pool_globalS");
26830 u00088 : constant Version_32 := 16#9d39c675#;
26831 pragma Export (C, u00088, "system__memoryB");
26832 u00089 : constant Version_32 := 16#445a22b5#;
26833 pragma Export (C, u00089, "system__memoryS");
26834 u00090 : constant Version_32 := 16#6a859064#;
26835 pragma Export (C, u00090, "system__storage_pools__subpoolsB");
26836 u00091 : constant Version_32 := 16#e3b008dc#;
26837 pragma Export (C, u00091, "system__storage_pools__subpoolsS");
26838 u00092 : constant Version_32 := 16#63f11652#;
26839 pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB");
26840 u00093 : constant Version_32 := 16#fe2f4b3a#;
26841 pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS");
26843 -- BEGIN ELABORATION ORDER
26847 -- system.case_util%s
26848 -- system.case_util%b
26850 -- system.img_bool%s
26851 -- system.img_bool%b
26852 -- system.img_int%s
26853 -- system.img_int%b
26856 -- system.parameters%s
26857 -- system.parameters%b
26859 -- interfaces.c_streams%s
26860 -- interfaces.c_streams%b
26861 -- system.standard_library%s
26862 -- system.exceptions_debug%s
26863 -- system.exceptions_debug%b
26864 -- system.storage_elements%s
26865 -- system.storage_elements%b
26866 -- system.stack_checking%s
26867 -- system.stack_checking%b
26868 -- system.string_hash%s
26869 -- system.string_hash%b
26871 -- system.strings%s
26872 -- system.strings%b
26874 -- system.traceback_entries%s
26875 -- system.traceback_entries%b
26876 -- ada.exceptions%s
26877 -- system.soft_links%s
26878 -- system.unsigned_types%s
26879 -- system.val_llu%s
26880 -- system.val_util%s
26881 -- system.val_util%b
26882 -- system.val_llu%b
26883 -- system.wch_con%s
26884 -- system.wch_con%b
26885 -- system.wch_cnv%s
26886 -- system.wch_jis%s
26887 -- system.wch_jis%b
26888 -- system.wch_cnv%b
26889 -- system.wch_stw%s
26890 -- system.wch_stw%b
26891 -- ada.exceptions.last_chance_handler%s
26892 -- ada.exceptions.last_chance_handler%b
26893 -- system.address_image%s
26894 -- system.exception_table%s
26895 -- system.exception_table%b
26896 -- ada.io_exceptions%s
26901 -- system.exceptions%s
26902 -- system.exceptions%b
26903 -- system.exceptions.machine%s
26904 -- system.finalization_root%s
26905 -- system.finalization_root%b
26906 -- ada.finalization%s
26907 -- ada.finalization%b
26908 -- system.storage_pools%s
26909 -- system.storage_pools%b
26910 -- system.finalization_masters%s
26911 -- system.storage_pools.subpools%s
26912 -- system.storage_pools.subpools.finalization%s
26913 -- system.storage_pools.subpools.finalization%b
26916 -- system.standard_library%b
26917 -- system.pool_global%s
26918 -- system.pool_global%b
26919 -- system.file_control_block%s
26920 -- system.file_io%s
26921 -- system.secondary_stack%s
26922 -- system.file_io%b
26923 -- system.storage_pools.subpools%b
26924 -- system.finalization_masters%b
26927 -- system.soft_links%b
26929 -- system.secondary_stack%b
26930 -- system.address_image%b
26931 -- system.traceback%s
26932 -- ada.exceptions%b
26933 -- system.traceback%b
26937 -- END ELABORATION ORDER
26944 -- The following source file name pragmas allow the generated file
26945 -- names to be unique for different main programs. They are needed
26946 -- since the package name will always be Ada_Main.
26948 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26949 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26951 pragma Suppress (Overflow_Check);
26952 with Ada.Exceptions;
26954 -- Generated package body for Ada_Main starts here
26956 package body ada_main is
26957 pragma Warnings (Off);
26959 -- These values are reference counter associated to units which have
26960 -- been elaborated. It is also used to avoid elaborating the
26961 -- same unit twice.
26963 E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E");
26964 E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E");
26965 E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E");
26966 E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E");
26967 E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E");
26968 E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E");
26969 E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E");
26970 E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E");
26971 E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E");
26972 E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E");
26973 E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E");
26974 E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E");
26975 E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E");
26976 E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E");
26977 E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E");
26978 E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E");
26979 E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E");
26980 E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E");
26982 Local_Priority_Specific_Dispatching : constant String := "";
26983 Local_Interrupt_States : constant String := "";
26985 Is_Elaborated : Boolean := False;
26987 procedure finalize_library is
26992 pragma Import (Ada, F1, "ada__text_io__finalize_spec");
27000 pragma Import (Ada, F2, "system__file_io__finalize_body");
27007 pragma Import (Ada, F3, "system__file_control_block__finalize_spec");
27015 pragma Import (Ada, F4, "system__pool_global__finalize_spec");
27021 pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec");
27027 pragma Import (Ada, F6, "system__finalization_masters__finalize_spec");
27032 procedure Reraise_Library_Exception_If_Any;
27033 pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any");
27035 Reraise_Library_Exception_If_Any;
27037 end finalize_library;
27043 procedure adainit is
27045 Main_Priority : Integer;
27046 pragma Import (C, Main_Priority, "__gl_main_priority");
27047 Time_Slice_Value : Integer;
27048 pragma Import (C, Time_Slice_Value, "__gl_time_slice_val");
27049 WC_Encoding : Character;
27050 pragma Import (C, WC_Encoding, "__gl_wc_encoding");
27051 Locking_Policy : Character;
27052 pragma Import (C, Locking_Policy, "__gl_locking_policy");
27053 Queuing_Policy : Character;
27054 pragma Import (C, Queuing_Policy, "__gl_queuing_policy");
27055 Task_Dispatching_Policy : Character;
27056 pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy");
27057 Priority_Specific_Dispatching : System.Address;
27058 pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching");
27059 Num_Specific_Dispatching : Integer;
27060 pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching");
27061 Main_CPU : Integer;
27062 pragma Import (C, Main_CPU, "__gl_main_cpu");
27063 Interrupt_States : System.Address;
27064 pragma Import (C, Interrupt_States, "__gl_interrupt_states");
27065 Num_Interrupt_States : Integer;
27066 pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states");
27067 Unreserve_All_Interrupts : Integer;
27068 pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts");
27069 Detect_Blocking : Integer;
27070 pragma Import (C, Detect_Blocking, "__gl_detect_blocking");
27071 Default_Stack_Size : Integer;
27072 pragma Import (C, Default_Stack_Size, "__gl_default_stack_size");
27073 Leap_Seconds_Support : Integer;
27074 pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support");
27076 procedure Runtime_Initialize;
27077 pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize");
27079 Finalize_Library_Objects : No_Param_Proc;
27080 pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects");
27082 -- Start of processing for adainit
27086 -- Record various information for this partition. The values
27087 -- are derived by the binder from information stored in the ali
27088 -- files by the compiler.
27090 if Is_Elaborated then
27093 Is_Elaborated := True;
27094 Main_Priority := -1;
27095 Time_Slice_Value := -1;
27096 WC_Encoding := 'b';
27097 Locking_Policy := ' ';
27098 Queuing_Policy := ' ';
27099 Task_Dispatching_Policy := ' ';
27100 Priority_Specific_Dispatching :=
27101 Local_Priority_Specific_Dispatching'Address;
27102 Num_Specific_Dispatching := 0;
27104 Interrupt_States := Local_Interrupt_States'Address;
27105 Num_Interrupt_States := 0;
27106 Unreserve_All_Interrupts := 0;
27107 Detect_Blocking := 0;
27108 Default_Stack_Size := -1;
27109 Leap_Seconds_Support := 0;
27111 Runtime_Initialize;
27113 Finalize_Library_Objects := finalize_library'access;
27115 -- Now we have the elaboration calls for all units in the partition.
27116 -- The Elab_Spec and Elab_Body attributes generate references to the
27117 -- implicit elaboration procedures generated by the compiler for
27118 -- each unit that requires elaboration. Increment a counter of
27119 -- reference for each unit.
27121 System.Soft_Links'Elab_Spec;
27122 System.Exception_Table'Elab_Body;
27124 Ada.Io_Exceptions'Elab_Spec;
27126 Ada.Tags'Elab_Spec;
27127 Ada.Streams'Elab_Spec;
27129 Interfaces.C'Elab_Spec;
27130 System.Exceptions'Elab_Spec;
27132 System.Finalization_Root'Elab_Spec;
27134 Ada.Finalization'Elab_Spec;
27136 System.Storage_Pools'Elab_Spec;
27138 System.Finalization_Masters'Elab_Spec;
27139 System.Storage_Pools.Subpools'Elab_Spec;
27140 System.Pool_Global'Elab_Spec;
27142 System.File_Control_Block'Elab_Spec;
27144 System.File_Io'Elab_Body;
27147 System.Finalization_Masters'Elab_Body;
27150 Ada.Tags'Elab_Body;
27152 System.Soft_Links'Elab_Body;
27154 System.Os_Lib'Elab_Body;
27156 System.Secondary_Stack'Elab_Body;
27158 Ada.Text_Io'Elab_Spec;
27159 Ada.Text_Io'Elab_Body;
27167 procedure adafinal is
27168 procedure s_stalib_adafinal;
27169 pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal");
27171 procedure Runtime_Finalize;
27172 pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize");
27175 if not Is_Elaborated then
27178 Is_Elaborated := False;
27183 -- We get to the main program of the partition by using
27184 -- pragma Import because if we try to with the unit and
27185 -- call it Ada style, then not only do we waste time
27186 -- recompiling it, but also, we don't really know the right
27187 -- switches (e.g.@@: identifier character set) to be used
27190 procedure Ada_Main_Program;
27191 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27197 -- main is actually a function, as in the ANSI C standard,
27198 -- defined to return the exit status. The three parameters
27199 -- are the argument count, argument values and environment
27204 argv : System.Address;
27205 envp : System.Address)
27208 -- The initialize routine performs low level system
27209 -- initialization using a standard library routine which
27210 -- sets up signal handling and performs any other
27211 -- required setup. The routine can be found in file
27214 procedure initialize;
27215 pragma Import (C, initialize, "__gnat_initialize");
27217 -- The finalize routine performs low level system
27218 -- finalization using a standard library routine. The
27219 -- routine is found in file a-final.c and in the standard
27220 -- distribution is a dummy routine that does nothing, so
27221 -- really this is a hook for special user finalization.
27223 procedure finalize;
27224 pragma Import (C, finalize, "__gnat_finalize");
27226 -- The following is to initialize the SEH exceptions
27228 SEH : aliased array (1 .. 2) of Integer;
27230 Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address;
27231 pragma Volatile (Ensure_Reference);
27233 -- Start of processing for main
27236 -- Save global variables
27242 -- Call low level system initialization
27244 Initialize (SEH'Address);
27246 -- Call our generated Ada initialization routine
27250 -- Now we call the main program of the partition
27254 -- Perform Ada finalization
27258 -- Perform low level system finalization
27262 -- Return the proper exit status
27263 return (gnat_exit_status);
27266 -- This section is entirely comments, so it has no effect on the
27267 -- compilation of the Ada_Main package. It provides the list of
27268 -- object files and linker options, as well as some standard
27269 -- libraries needed for the link. The gnatlink utility parses
27270 -- this b~hello.adb file to read these comment lines to generate
27271 -- the appropriate command line arguments for the call to the
27272 -- system linker. The BEGIN/END lines are used for sentinels for
27273 -- this parsing operation.
27275 -- The exact file names will of course depend on the environment,
27276 -- host/target and location of files on the host system.
27278 -- BEGIN Object file/option list
27281 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27282 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27283 -- END Object file/option list
27288 The Ada code in the above example is exactly what is generated by the
27289 binder. We have added comments to more clearly indicate the function
27290 of each part of the generated @code{Ada_Main} package.
27292 The code is standard Ada in all respects, and can be processed by any
27293 tools that handle Ada. In particular, it is possible to use the debugger
27294 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27295 suppose that for reasons that you do not understand, your program is crashing
27296 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27297 you can place a breakpoint on the call:
27302 Ada.Text_Io'Elab_Body;
27306 and trace the elaboration routine for this package to find out where
27307 the problem might be (more usually of course you would be debugging
27308 elaboration code in your own application).
27310 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
27312 @node Elaboration Order Handling in GNAT,Inline Assembler,Example of Binder Output File,Top
27313 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order-handling-in-gnat}@anchor{f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat doc}@anchor{22b}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id1}@anchor{22c}
27314 @chapter Elaboration Order Handling in GNAT
27317 @geindex Order of elaboration
27319 @geindex Elaboration control
27321 This appendix describes the handling of elaboration code in Ada and GNAT, and
27322 discusses how the order of elaboration of program units can be controlled in
27323 GNAT, either automatically or with explicit programming features.
27326 * Elaboration Code::
27327 * Elaboration Order::
27328 * Checking the Elaboration Order::
27329 * Controlling the Elaboration Order in Ada::
27330 * Controlling the Elaboration Order in GNAT::
27331 * Mixing Elaboration Models::
27332 * ABE Diagnostics::
27333 * SPARK Diagnostics::
27334 * Elaboration Circularities::
27335 * Resolving Elaboration Circularities::
27336 * Elaboration-related Compiler Switches::
27337 * Summary of Procedures for Elaboration Control::
27338 * Inspecting the Chosen Elaboration Order::
27342 @node Elaboration Code,Elaboration Order,,Elaboration Order Handling in GNAT
27343 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-code}@anchor{22d}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id2}@anchor{22e}
27344 @section Elaboration Code
27347 Ada defines the term @emph{execution} as the process by which a construct achieves
27348 its run-time effect. This process is also referred to as @strong{elaboration} for
27349 declarations and @emph{evaluation} for expressions.
27351 The execution model in Ada allows for certain sections of an Ada program to be
27352 executed prior to execution of the program itself, primarily with the intent of
27353 initializing data. These sections are referred to as @strong{elaboration code}.
27354 Elaboration code is executed as follows:
27360 All partitions of an Ada program are executed in parallel with one another,
27361 possibly in a separate address space, and possibly on a separate computer.
27364 The execution of a partition involves running the environment task for that
27368 The environment task executes all elaboration code (if available) for all
27369 units within that partition. This code is said to be executed at
27370 @strong{elaboration time}.
27373 The environment task executes the Ada program (if available) for that
27377 In addition to the Ada terminology, this appendix defines the following terms:
27385 The act of calling a subprogram, instantiating a generic, or activating a
27391 A construct that is elaborated or invoked by elaboration code is referred to
27392 as an @emph{elaboration scenario} or simply a @strong{scenario}. GNAT recognizes the
27393 following scenarios:
27399 @code{'Access} of entries, operators, and subprograms
27402 Activation of tasks
27405 Calls to entries, operators, and subprograms
27408 Instantiations of generic templates
27414 A construct elaborated by a scenario is referred to as @emph{elaboration target}
27415 or simply @strong{target}. GNAT recognizes the following targets:
27421 For @code{'Access} of entries, operators, and subprograms, the target is the
27422 entry, operator, or subprogram being aliased.
27425 For activation of tasks, the target is the task body
27428 For calls to entries, operators, and subprograms, the target is the entry,
27429 operator, or subprogram being invoked.
27432 For instantiations of generic templates, the target is the generic template
27433 being instantiated.
27437 Elaboration code may appear in two distinct contexts:
27443 @emph{Library level}
27445 A scenario appears at the library level when it is encapsulated by a package
27446 [body] compilation unit, ignoring any other package [body] declarations in
27455 Val : ... := Server.Func;
27460 In the example above, the call to @code{Server.Func} is an elaboration scenario
27461 because it appears at the library level of package @code{Client}. Note that the
27462 declaration of package @code{Nested} is ignored according to the definition
27463 given above. As a result, the call to @code{Server.Func} will be invoked when
27464 the spec of unit @code{Client} is elaborated.
27467 @emph{Package body statements}
27469 A scenario appears within the statement sequence of a package body when it is
27470 bounded by the region starting from the @code{begin} keyword of the package body
27471 and ending at the @code{end} keyword of the package body.
27474 package body Client is
27484 In the example above, the call to @code{Proc} is an elaboration scenario because
27485 it appears within the statement sequence of package body @code{Client}. As a
27486 result, the call to @code{Proc} will be invoked when the body of @code{Client} is
27490 @node Elaboration Order,Checking the Elaboration Order,Elaboration Code,Elaboration Order Handling in GNAT
27491 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order}@anchor{22f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id3}@anchor{230}
27492 @section Elaboration Order
27495 The sequence by which the elaboration code of all units within a partition is
27496 executed is referred to as @strong{elaboration order}.
27498 Within a single unit, elaboration code is executed in sequential order.
27503 package body Client is
27504 Result : ... := Server.Func;
27507 package Inst is new Server.Gen;
27509 Inst.Eval (Result);
27517 In the example above, the elaboration order within package body @code{Client} is
27524 The object declaration of @code{Result} is elaborated.
27530 Function @code{Server.Func} is invoked.
27534 The subprogram body of @code{Proc} is elaborated.
27537 Procedure @code{Proc} is invoked.
27543 Generic unit @code{Server.Gen} is instantiated as @code{Inst}.
27546 Instance @code{Inst} is elaborated.
27549 Procedure @code{Inst.Eval} is invoked.
27553 The elaboration order of all units within a partition depends on the following
27560 @emph{with}ed units
27569 preelaborability of units
27572 presence of elaboration-control pragmas
27575 invocations performed in elaboration code
27578 A program may have several elaboration orders depending on its structure.
27584 function Func (Index : Integer) return Integer;
27589 package body Server is
27590 Results : array (1 .. 5) of Integer := (1, 2, 3, 4, 5);
27592 function Func (Index : Integer) return Integer is
27594 return Results (Index);
27602 Val : constant Integer := Server.Func (3);
27608 procedure Main is begin null; end Main;
27612 The following elaboration order exhibits a fundamental problem referred to as
27613 @emph{access-before-elaboration} or simply @strong{ABE}.
27625 The elaboration of @code{Server}'s spec materializes function @code{Func}, making it
27626 callable. The elaboration of @code{Client}'s spec elaborates the declaration of
27627 @code{Val}. This invokes function @code{Server.Func}, however the body of
27628 @code{Server.Func} has not been elaborated yet because @code{Server}'s body comes
27629 after @code{Client}'s spec in the elaboration order. As a result, the value of
27630 constant @code{Val} is now undefined.
27632 Without any guarantees from the language, an undetected ABE problem may hinder
27633 proper initialization of data, which in turn may lead to undefined behavior at
27634 run time. To prevent such ABE problems, Ada employs dynamic checks in the same
27635 vein as index or null exclusion checks. A failed ABE check raises exception
27636 @code{Program_Error}.
27638 The following elaboration order avoids the ABE problem and the program can be
27639 successfully elaborated.
27651 Ada states that a total elaboration order must exist, but it does not define
27652 what this order is. A compiler is thus tasked with choosing a suitable
27653 elaboration order which satisfies the dependencies imposed by @emph{with} clauses,
27654 unit categorization, elaboration-control pragmas, and invocations performed in
27655 elaboration code. Ideally an order that avoids ABE problems should be chosen,
27656 however a compiler may not always find such an order due to complications with
27657 respect to control and data flow.
27659 @node Checking the Elaboration Order,Controlling the Elaboration Order in Ada,Elaboration Order,Elaboration Order Handling in GNAT
27660 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id4}@anchor{231}@anchor{gnat_ugn/elaboration_order_handling_in_gnat checking-the-elaboration-order}@anchor{232}
27661 @section Checking the Elaboration Order
27664 To avoid placing the entire elaboration-order burden on the programmer, Ada
27665 provides three lines of defense:
27671 @emph{Static semantics}
27673 Static semantic rules restrict the possible choice of elaboration order. For
27674 instance, if unit Client @emph{with}s unit Server, then the spec of Server is
27675 always elaborated prior to Client. The same principle applies to child units
27676 - the spec of a parent unit is always elaborated prior to the child unit.
27679 @emph{Dynamic semantics}
27681 Dynamic checks are performed at run time, to ensure that a target is
27682 elaborated prior to a scenario that invokes it, thus avoiding ABE problems.
27683 A failed run-time check raises exception @code{Program_Error}. The following
27684 restrictions apply:
27690 @emph{Restrictions on calls}
27692 An entry, operator, or subprogram can be called from elaboration code only
27693 when the corresponding body has been elaborated.
27696 @emph{Restrictions on instantiations}
27698 A generic unit can be instantiated by elaboration code only when the
27699 corresponding body has been elaborated.
27702 @emph{Restrictions on task activation}
27704 A task can be activated by elaboration code only when the body of the
27705 associated task type has been elaborated.
27708 The restrictions above can be summarized by the following rule:
27710 @emph{If a target has a body, then this body must be elaborated prior to the
27711 scenario that invokes the target.}
27714 @emph{Elaboration control}
27716 Pragmas are provided for the programmer to specify the desired elaboration
27720 @node Controlling the Elaboration Order in Ada,Controlling the Elaboration Order in GNAT,Checking the Elaboration Order,Elaboration Order Handling in GNAT
27721 @anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order-in-ada}@anchor{233}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id5}@anchor{234}
27722 @section Controlling the Elaboration Order in Ada
27725 Ada provides several idioms and pragmas to aid the programmer with specifying
27726 the desired elaboration order and avoiding ABE problems altogether.
27732 @emph{Packages without a body}
27734 A library package which does not require a completing body does not suffer
27740 type Element is private;
27741 package Containers is
27742 type Element_Array is array (1 .. 10) of Element;
27747 In the example above, package @code{Pack} does not require a body because it
27748 does not contain any constructs which require completion in a body. As a
27749 result, generic @code{Pack.Containers} can be instantiated without encountering
27753 @geindex pragma Pure
27761 Pragma @code{Pure} places sufficient restrictions on a unit to guarantee that no
27762 scenario within the unit can result in an ABE problem.
27765 @geindex pragma Preelaborate
27771 @emph{pragma Preelaborate}
27773 Pragma @code{Preelaborate} is slightly less restrictive than pragma @code{Pure},
27774 but still strong enough to prevent ABE problems within a unit.
27777 @geindex pragma Elaborate_Body
27783 @emph{pragma Elaborate_Body}
27785 Pragma @code{Elaborate_Body} requires that the body of a unit is elaborated
27786 immediately after its spec. This restriction guarantees that no client
27787 scenario can invoke a server target before the target body has been
27788 elaborated because the spec and body are effectively "glued" together.
27792 pragma Elaborate_Body;
27794 function Func return Integer;
27799 package body Server is
27800 function Func return Integer is
27810 Val : constant Integer := Server.Func;
27814 In the example above, pragma @code{Elaborate_Body} guarantees the following
27823 because the spec of @code{Server} must be elaborated prior to @code{Client} by
27824 virtue of the @emph{with} clause, and in addition the body of @code{Server} must be
27825 elaborated immediately after the spec of @code{Server}.
27827 Removing pragma @code{Elaborate_Body} could result in the following incorrect
27836 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func} has
27837 not been elaborated yet.
27840 The pragmas outlined above allow a server unit to guarantee safe elaboration
27841 use by client units. Thus it is a good rule to mark units as @code{Pure} or
27842 @code{Preelaborate}, and if this is not possible, mark them as @code{Elaborate_Body}.
27844 There are however situations where @code{Pure}, @code{Preelaborate}, and
27845 @code{Elaborate_Body} are not applicable. Ada provides another set of pragmas for
27846 use by client units to help ensure the elaboration safety of server units they
27849 @geindex pragma Elaborate (Unit)
27855 @emph{pragma Elaborate (Unit)}
27857 Pragma @code{Elaborate} can be placed in the context clauses of a unit, after a
27858 @emph{with} clause. It guarantees that both the spec and body of its argument will
27859 be elaborated prior to the unit with the pragma. Note that other unrelated
27860 units may be elaborated in between the spec and the body.
27864 function Func return Integer;
27869 package body Server is
27870 function Func return Integer is
27879 pragma Elaborate (Server);
27881 Val : constant Integer := Server.Func;
27885 In the example above, pragma @code{Elaborate} guarantees the following
27894 Removing pragma @code{Elaborate} could result in the following incorrect
27903 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func}
27904 has not been elaborated yet.
27907 @geindex pragma Elaborate_All (Unit)
27913 @emph{pragma Elaborate_All (Unit)}
27915 Pragma @code{Elaborate_All} is placed in the context clauses of a unit, after
27916 a @emph{with} clause. It guarantees that both the spec and body of its argument
27917 will be elaborated prior to the unit with the pragma, as well as all units
27918 @emph{with}ed by the spec and body of the argument, recursively. Note that other
27919 unrelated units may be elaborated in between the spec and the body.
27923 function Factorial (Val : Natural) return Natural;
27928 package body Math is
27929 function Factorial (Val : Natural) return Natural is
27937 package Computer is
27938 type Operation_Kind is (None, Op_Factorial);
27942 Op : Operation_Kind) return Natural;
27948 package body Computer is
27951 Op : Operation_Kind) return Natural
27953 if Op = Op_Factorial then
27954 return Math.Factorial (Val);
27964 pragma Elaborate_All (Computer);
27966 Val : constant Natural :=
27967 Computer.Compute (123, Computer.Op_Factorial);
27971 In the example above, pragma @code{Elaborate_All} can result in the following
27982 Note that there are several allowable suborders for the specs and bodies of
27983 @code{Math} and @code{Computer}, but the point is that these specs and bodies will
27984 be elaborated prior to @code{Client}.
27986 Removing pragma @code{Elaborate_All} could result in the following incorrect
27997 where @code{Client} invokes @code{Computer.Compute}, which in turn invokes
27998 @code{Math.Factorial}, but the body of @code{Math.Factorial} has not been
28002 All pragmas shown above can be summarized by the following rule:
28004 @emph{If a client unit elaborates a server target directly or indirectly, then if
28005 the server unit requires a body and does not have pragma Pure, Preelaborate,
28006 or Elaborate_Body, then the client unit should have pragma Elaborate or
28007 Elaborate_All for the server unit.}
28009 If the rule outlined above is not followed, then a program may fall in one of
28010 the following states:
28016 @emph{No elaboration order exists}
28018 In this case a compiler must diagnose the situation, and refuse to build an
28019 executable program.
28022 @emph{One or more incorrect elaboration orders exist}
28024 In this case a compiler can build an executable program, but
28025 @code{Program_Error} will be raised when the program is run.
28028 @emph{Several elaboration orders exist, some correct, some incorrect}
28030 In this case the programmer has not controlled the elaboration order. As a
28031 result, a compiler may or may not pick one of the correct orders, and the
28032 program may or may not raise @code{Program_Error} when it is run. This is the
28033 worst possible state because the program may fail on another compiler, or
28034 even another version of the same compiler.
28037 @emph{One or more correct orders exist}
28039 In this case a compiler can build an executable program, and the program is
28040 run successfully. This state may be guaranteed by following the outlined
28041 rules, or may be the result of good program architecture.
28044 Note that one additional advantage of using @code{Elaborate} and @code{Elaborate_All}
28045 is that the program continues to stay in the last state (one or more correct
28046 orders exist) even if maintenance changes the bodies of targets.
28048 @node Controlling the Elaboration Order in GNAT,Mixing Elaboration Models,Controlling the Elaboration Order in Ada,Elaboration Order Handling in GNAT
28049 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id6}@anchor{235}@anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order-in-gnat}@anchor{236}
28050 @section Controlling the Elaboration Order in GNAT
28053 In addition to Ada semantics and rules synthesized from them, GNAT offers
28054 three elaboration models to aid the programmer with specifying the correct
28055 elaboration order and to diagnose elaboration problems.
28057 @geindex Dynamic elaboration model
28063 @emph{Dynamic elaboration model}
28065 This is the most permissive of the three elaboration models and emulates the
28066 behavior specified by the Ada Reference Manual. When the dynamic model is in
28067 effect, GNAT makes the following assumptions:
28073 All code within all units in a partition is considered to be elaboration
28077 Some of the invocations in elaboration code may not take place at run time
28078 due to conditional execution.
28081 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28082 that invoke internal targets. In addition, GNAT generates run-time checks for
28083 all external targets and for all scenarios that may exhibit ABE problems.
28085 The elaboration order is obtained by honoring all @emph{with} clauses, purity and
28086 preelaborability of units, and elaboration-control pragmas. The dynamic model
28087 attempts to take all invocations in elaboration code into account. If an
28088 invocation leads to a circularity, GNAT ignores the invocation based on the
28089 assumptions stated above. An order obtained using the dynamic model may fail
28090 an ABE check at run time when GNAT ignored an invocation.
28092 The dynamic model is enabled with compiler switch @code{-gnatE}.
28095 @geindex Static elaboration model
28101 @emph{Static elaboration model}
28103 This is the middle ground of the three models. When the static model is in
28104 effect, GNAT makes the following assumptions:
28110 Only code at the library level and in package body statements within all
28111 units in a partition is considered to be elaboration code.
28114 All invocations in elaboration will take place at run time, regardless of
28115 conditional execution.
28118 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28119 that invoke internal targets. In addition, GNAT generates run-time checks for
28120 all external targets and for all scenarios that may exhibit ABE problems.
28122 The elaboration order is obtained by honoring all @emph{with} clauses, purity and
28123 preelaborability of units, presence of elaboration-control pragmas, and all
28124 invocations in elaboration code. An order obtained using the static model is
28125 guaranteed to be ABE problem-free, excluding dispatching calls and
28126 access-to-subprogram types.
28128 The static model is the default model in GNAT.
28131 @geindex SPARK elaboration model
28137 @emph{SPARK elaboration model}
28139 This is the most conservative of the three models and enforces the SPARK
28140 rules of elaboration as defined in the SPARK Reference Manual, section 7.7.
28141 The SPARK model is in effect only when a scenario and a target reside in a
28142 region subject to @code{SPARK_Mode On}, otherwise the dynamic or static model
28145 The SPARK model is enabled with compiler switch @code{-gnatd.v}.
28148 @geindex Legacy elaboration models
28154 @emph{Legacy elaboration models}
28156 In addition to the three elaboration models outlined above, GNAT provides the
28157 following legacy models:
28163 @cite{Legacy elaboration-checking model} available in pre-18.x versions of GNAT.
28164 This model is enabled with compiler switch @code{-gnatH}.
28167 @cite{Legacy elaboration-order model} available in pre-20.x versions of GNAT.
28168 This model is enabled with binder switch @code{-H}.
28172 @geindex Relaxed elaboration mode
28174 The dynamic, legacy, and static models can be relaxed using compiler switch
28175 @code{-gnatJ}, making them more permissive. Note that in this mode, GNAT
28176 may not diagnose certain elaboration issues or install run-time checks.
28178 @node Mixing Elaboration Models,ABE Diagnostics,Controlling the Elaboration Order in GNAT,Elaboration Order Handling in GNAT
28179 @anchor{gnat_ugn/elaboration_order_handling_in_gnat mixing-elaboration-models}@anchor{237}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id7}@anchor{238}
28180 @section Mixing Elaboration Models
28183 It is possible to mix units compiled with a different elaboration model,
28184 however the following rules must be observed:
28190 A client unit compiled with the dynamic model can only @emph{with} a server unit
28191 that meets at least one of the following criteria:
28197 The server unit is compiled with the dynamic model.
28200 The server unit is a GNAT implementation unit from the @code{Ada}, @code{GNAT},
28201 @code{Interfaces}, or @code{System} hierarchies.
28204 The server unit has pragma @code{Pure} or @code{Preelaborate}.
28207 The client unit has an explicit @code{Elaborate_All} pragma for the server
28212 These rules ensure that elaboration checks are not omitted. If the rules are
28213 violated, the binder emits a warning:
28218 warning: "x.ads" has dynamic elaboration checks and with's
28219 warning: "y.ads" which has static elaboration checks
28223 The warnings can be suppressed by binder switch @code{-ws}.
28225 @node ABE Diagnostics,SPARK Diagnostics,Mixing Elaboration Models,Elaboration Order Handling in GNAT
28226 @anchor{gnat_ugn/elaboration_order_handling_in_gnat abe-diagnostics}@anchor{239}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id8}@anchor{23a}
28227 @section ABE Diagnostics
28230 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28231 that invoke internal targets, regardless of whether the dynamic, SPARK, or
28232 static model is in effect.
28234 Note that GNAT emits warnings rather than hard errors whenever it encounters an
28235 elaboration problem. This is because the elaboration model in effect may be too
28236 conservative, or a particular scenario may not be invoked due conditional
28237 execution. The warnings can be suppressed selectively with @code{pragma Warnings
28238 (Off)} or globally with compiler switch @code{-gnatwL}.
28240 A @emph{guaranteed ABE} arises when the body of a target is not elaborated early
28241 enough, and causes @emph{all} scenarios that directly invoke the target to fail.
28246 package body Guaranteed_ABE is
28247 function ABE return Integer;
28249 Val : constant Integer := ABE;
28251 function ABE return Integer is
28255 end Guaranteed_ABE;
28259 In the example above, the elaboration of @code{Guaranteed_ABE}'s body elaborates
28260 the declaration of @code{Val}. This invokes function @code{ABE}, however the body of
28261 @code{ABE} has not been elaborated yet. GNAT emits the following diagnostic:
28266 4. Val : constant Integer := ABE;
28268 >>> warning: cannot call "ABE" before body seen
28269 >>> warning: Program_Error will be raised at run time
28273 A @emph{conditional ABE} arises when the body of a target is not elaborated early
28274 enough, and causes @emph{some} scenarios that directly invoke the target to fail.
28279 1. package body Conditional_ABE is
28280 2. procedure Force_Body is null;
28283 5. with function Func return Integer;
28285 7. Val : constant Integer := Func;
28288 10. function ABE return Integer;
28290 12. function Cause_ABE return Boolean is
28291 13. package Inst is new Gen (ABE);
28296 18. Val : constant Boolean := Cause_ABE;
28298 20. function ABE return Integer is
28303 25. Safe : constant Boolean := Cause_ABE;
28304 26. end Conditional_ABE;
28308 In the example above, the elaboration of package body @code{Conditional_ABE}
28309 elaborates the declaration of @code{Val}. This invokes function @code{Cause_ABE},
28310 which instantiates generic unit @code{Gen} as @code{Inst}. The elaboration of
28311 @code{Inst} invokes function @code{ABE}, however the body of @code{ABE} has not been
28312 elaborated yet. GNAT emits the following diagnostic:
28317 13. package Inst is new Gen (ABE);
28319 >>> warning: in instantiation at line 7
28320 >>> warning: cannot call "ABE" before body seen
28321 >>> warning: Program_Error may be raised at run time
28322 >>> warning: body of unit "Conditional_ABE" elaborated
28323 >>> warning: function "Cause_ABE" called at line 18
28324 >>> warning: function "ABE" called at line 7, instance at line 13
28328 Note that the same ABE problem does not occur with the elaboration of
28329 declaration @code{Safe} because the body of function @code{ABE} has already been
28330 elaborated at that point.
28332 @node SPARK Diagnostics,Elaboration Circularities,ABE Diagnostics,Elaboration Order Handling in GNAT
28333 @anchor{gnat_ugn/elaboration_order_handling_in_gnat spark-diagnostics}@anchor{23b}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id9}@anchor{23c}
28334 @section SPARK Diagnostics
28337 GNAT enforces the SPARK rules of elaboration as defined in the SPARK Reference
28338 Manual section 7.7 when compiler switch @code{-gnatd.v} is in effect. Note
28339 that GNAT emits hard errors whenever it encounters a violation of the SPARK
28346 2. package body SPARK_Diagnostics with SPARK_Mode is
28347 3. Val : constant Integer := Server.Func;
28349 >>> call to "Func" during elaboration in SPARK
28350 >>> unit "SPARK_Diagnostics" requires pragma "Elaborate_All" for "Server"
28351 >>> body of unit "SPARK_Model" elaborated
28352 >>> function "Func" called at line 3
28354 4. end SPARK_Diagnostics;
28358 @node Elaboration Circularities,Resolving Elaboration Circularities,SPARK Diagnostics,Elaboration Order Handling in GNAT
28359 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id10}@anchor{23d}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-circularities}@anchor{23e}
28360 @section Elaboration Circularities
28363 An @strong{elaboration circularity} occurs whenever the elaboration of a set of
28364 units enters a deadlocked state, where each unit is waiting for another unit
28365 to be elaborated. This situation may be the result of improper use of @emph{with}
28366 clauses, elaboration-control pragmas, or invocations in elaboration code.
28368 The following example exhibits an elaboration circularity.
28373 with B; pragma Elaborate (B);
28380 procedure Force_Body;
28387 procedure Force_Body is null;
28389 Elab : constant Integer := C.Func;
28395 function Func return Integer;
28402 function Func return Integer is
28410 The binder emits the following diagnostic:
28415 error: Elaboration circularity detected
28419 info: unit "a (spec)" depends on its own elaboration
28423 info: unit "a (spec)" has with clause and pragma Elaborate for unit "b (spec)"
28424 info: unit "b (body)" is in the closure of pragma Elaborate
28425 info: unit "b (body)" invokes a construct of unit "c (body)" at elaboration time
28426 info: unit "c (body)" has with clause for unit "a (spec)"
28430 info: remove pragma Elaborate for unit "b (body)" in unit "a (spec)"
28431 info: use the dynamic elaboration model (compiler switch -gnatE)
28435 The diagnostic consist of the following sections:
28443 This section provides a short explanation describing why the set of units
28444 could not be ordered.
28449 This section enumerates the units comprising the deadlocked set, along with
28450 their interdependencies.
28455 This section enumerates various tactics for eliminating the circularity.
28458 @node Resolving Elaboration Circularities,Elaboration-related Compiler Switches,Elaboration Circularities,Elaboration Order Handling in GNAT
28459 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id11}@anchor{23f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat resolving-elaboration-circularities}@anchor{240}
28460 @section Resolving Elaboration Circularities
28463 The most desirable option from the point of view of long-term maintenance is to
28464 rearrange the program so that the elaboration problems are avoided. One useful
28465 technique is to place the elaboration code into separate child packages.
28466 Another is to move some of the initialization code to explicitly invoked
28467 subprograms, where the program controls the order of initialization explicitly.
28468 Although this is the most desirable option, it may be impractical and involve
28469 too much modification, especially in the case of complex legacy code.
28471 When faced with an elaboration circularity, the programmer should also consider
28472 the tactics given in the suggestions section of the circularity diagnostic.
28473 Depending on the units involved in the circularity, their @emph{with} clauses,
28474 purity, preelaborability, presence of elaboration-control pragmas and
28475 invocations at elaboration time, the binder may suggest one or more of the
28476 following tactics to eliminate the circularity:
28482 Pragma Elaborate elimination
28485 remove pragma Elaborate for unit "..." in unit "..."
28488 This tactic is suggested when the binder has determined that pragma
28495 Prevents a set of units from being elaborated.
28498 The removal of the pragma will not eliminate the semantic effects of the
28499 pragma. In other words, the argument of the pragma will still be elaborated
28500 prior to the unit containing the pragma.
28503 The removal of the pragma will enable the successful ordering of the units.
28506 The programmer should remove the pragma as advised, and rebuild the program.
28509 Pragma Elaborate_All elimination
28512 remove pragma Elaborate_All for unit "..." in unit "..."
28515 This tactic is suggested when the binder has determined that pragma
28516 @code{Elaborate_All}:
28522 Prevents a set of units from being elaborated.
28525 The removal of the pragma will not eliminate the semantic effects of the
28526 pragma. In other words, the argument of the pragma along with its @emph{with}
28527 closure will still be elaborated prior to the unit containing the pragma.
28530 The removal of the pragma will enable the successful ordering of the units.
28533 The programmer should remove the pragma as advised, and rebuild the program.
28536 Pragma Elaborate_All downgrade
28539 change pragma Elaborate_All for unit "..." to Elaborate in unit "..."
28542 This tactic is always suggested with the pragma @code{Elaborate_All} elimination
28543 tactic. It offers a different alernative of guaranteeing that the argument of
28544 the pragma will still be elaborated prior to the unit containing the pragma.
28546 The programmer should update the pragma as advised, and rebuild the program.
28549 Pragma Elaborate_Body elimination
28552 remove pragma Elaborate_Body in unit "..."
28555 This tactic is suggested when the binder has determined that pragma
28556 @code{Elaborate_Body}:
28562 Prevents a set of units from being elaborated.
28565 The removal of the pragma will enable the successful ordering of the units.
28568 Note that the binder cannot determine whether the pragma is required for
28569 other purposes, such as guaranteeing the initialization of a variable
28570 declared in the spec by elaboration code in the body.
28572 The programmer should remove the pragma as advised, and rebuild the program.
28575 Use of pragma Restrictions
28578 use pragma Restrictions (No_Entry_Calls_In_Elaboration_Code)
28581 This tactic is suggested when the binder has determined that a task
28582 activation at elaboration time:
28588 Prevents a set of units from being elaborated.
28591 Note that the binder cannot determine with certainty whether the task will
28592 block at elaboration time.
28594 The programmer should create a configuration file, place the pragma within,
28595 update the general compilation arguments, and rebuild the program.
28598 Use of dynamic elaboration model
28601 use the dynamic elaboration model (compiler switch -gnatE)
28604 This tactic is suggested when the binder has determined that an invocation at
28611 Prevents a set of units from being elaborated.
28614 The use of the dynamic model will enable the successful ordering of the
28618 The programmer has two options:
28624 Determine the units involved in the invocation using the detailed
28625 invocation information, and add compiler switch @code{-gnatE} to the
28626 compilation arguments of selected files only. This approach will yield
28627 safer elaboration orders compared to the other option because it will
28628 minimize the opportunities presented to the dynamic model for ignoring
28632 Add compiler switch @code{-gnatE} to the general compilation arguments.
28636 Use of detailed invocation information
28639 use detailed invocation information (compiler switch -gnatd_F)
28642 This tactic is always suggested with the use of the dynamic model tactic. It
28643 causes the circularity section of the circularity diagnostic to describe the
28644 flow of elaboration code from a unit to a unit, enumerating all such paths in
28647 The programmer should analyze this information to determine which units
28648 should be compiled with the dynamic model.
28651 Forced-dependency elimination
28654 remove the dependency of unit "..." on unit "..." from the argument of switch -f
28657 This tactic is suggested when the binder has determined that a dependency
28658 present in the forced-elaboration-order file indicated by binder switch
28665 Prevents a set of units from being elaborated.
28668 The removal of the dependency will enable the successful ordering of the
28672 The programmer should edit the forced-elaboration-order file, remove the
28673 dependency, and rebind the program.
28676 All forced-dependency elimination
28682 This tactic is suggested in case editing the forced-elaboration-order file is
28685 The programmer should remove binder switch @code{-f} from the binder
28686 arguments, and rebind.
28689 Multiple-circularities diagnostic
28692 diagnose all circularities (binder switch -d_C)
28695 By default, the binder will diagnose only the highest-precedence circularity.
28696 If the program contains multiple circularities, the binder will suggest the
28697 use of binder switch @code{-d_C} in order to obtain the diagnostics of all
28700 The programmer should add binder switch @code{-d_C} to the binder
28701 arguments, and rebind.
28704 If none of the tactics suggested by the binder eliminate the elaboration
28705 circularity, the programmer should consider using one of the legacy elaboration
28706 models, in the following order:
28712 Use the pre-20.x legacy elaboration-order model, with binder switch
28716 Use both pre-18.x and pre-20.x legacy elaboration models, with compiler
28717 switch @code{-gnatH} and binder switch @code{-H}.
28720 Use the relaxed static-elaboration model, with compiler switches
28721 @code{-gnatH} @code{-gnatJ} and binder switch @code{-H}.
28724 Use the relaxed dynamic-elaboration model, with compiler switches
28725 @code{-gnatH} @code{-gnatJ} @code{-gnatE} and binder switch
28729 @node Elaboration-related Compiler Switches,Summary of Procedures for Elaboration Control,Resolving Elaboration Circularities,Elaboration Order Handling in GNAT
28730 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id12}@anchor{241}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-related-compiler-switches}@anchor{242}
28731 @section Elaboration-related Compiler Switches
28734 GNAT has several switches that affect the elaboration model and consequently
28735 the elaboration order chosen by the binder.
28737 @geindex -gnatE (gnat)
28742 @item @code{-gnatE}
28744 Dynamic elaboration checking mode enabled
28746 When this switch is in effect, GNAT activates the dynamic model.
28749 @geindex -gnatel (gnat)
28754 @item @code{-gnatel}
28756 Turn on info messages on generated Elaborate[_All] pragmas
28758 This switch is only applicable to the pre-20.x legacy elaboration models.
28759 The post-20.x elaboration model no longer relies on implicitly generated
28760 @code{Elaborate} and @code{Elaborate_All} pragmas to order units.
28762 When this switch is in effect, GNAT will emit the following supplementary
28763 information depending on the elaboration model in effect.
28769 @emph{Dynamic model}
28771 GNAT will indicate missing @code{Elaborate} and @code{Elaborate_All} pragmas for
28772 all library-level scenarios within the partition.
28775 @emph{Static model}
28777 GNAT will indicate all scenarios invoked during elaboration. In addition,
28778 it will provide detailed traceback when an implicit @code{Elaborate} or
28779 @code{Elaborate_All} pragma is generated.
28784 GNAT will indicate how an elaboration requirement is met by the context of
28785 a unit. This diagnostic requires compiler switch @code{-gnatd.v}.
28788 1. with Server; pragma Elaborate_All (Server);
28789 2. package Client with SPARK_Mode is
28790 3. Val : constant Integer := Server.Func;
28792 >>> info: call to "Func" during elaboration in SPARK
28793 >>> info: "Elaborate_All" requirement for unit "Server" met by pragma at line 1
28800 @geindex -gnatH (gnat)
28805 @item @code{-gnatH}
28807 Legacy elaboration checking mode enabled
28809 When this switch is in effect, GNAT will utilize the pre-18.x elaboration
28813 @geindex -gnatJ (gnat)
28818 @item @code{-gnatJ}
28820 Relaxed elaboration checking mode enabled
28822 When this switch is in effect, GNAT will not process certain scenarios,
28823 resulting in a more permissive elaboration model. Note that this may
28824 eliminate some diagnostics and run-time checks.
28827 @geindex -gnatw.f (gnat)
28832 @item @code{-gnatw.f}
28834 Turn on warnings for suspicious Subp'Access
28836 When this switch is in effect, GNAT will treat @code{'Access} of an entry,
28837 operator, or subprogram as a potential call to the target and issue warnings:
28840 1. package body Attribute_Call is
28841 2. function Func return Integer;
28842 3. type Func_Ptr is access function return Integer;
28844 5. Ptr : constant Func_Ptr := Func'Access;
28846 >>> warning: "Access" attribute of "Func" before body seen
28847 >>> warning: possible Program_Error on later references
28848 >>> warning: body of unit "Attribute_Call" elaborated
28849 >>> warning: "Access" of "Func" taken at line 5
28852 7. function Func return Integer is
28856 11. end Attribute_Call;
28859 In the example above, the elaboration of declaration @code{Ptr} is assigned
28860 @code{Func'Access} before the body of @code{Func} has been elaborated.
28863 @geindex -gnatwl (gnat)
28868 @item @code{-gnatwl}
28870 Turn on warnings for elaboration problems
28872 When this switch is in effect, GNAT emits diagnostics in the form of warnings
28873 concerning various elaboration problems. The warnings are enabled by default.
28874 The switch is provided in case all warnings are suppressed, but elaboration
28875 warnings are still desired.
28877 @item @code{-gnatwL}
28879 Turn off warnings for elaboration problems
28881 When this switch is in effect, GNAT no longer emits any diagnostics in the
28882 form of warnings. Selective suppression of elaboration problems is possible
28883 using @code{pragma Warnings (Off)}.
28886 1. package body Selective_Suppression is
28887 2. function ABE return Integer;
28889 4. Val_1 : constant Integer := ABE;
28891 >>> warning: cannot call "ABE" before body seen
28892 >>> warning: Program_Error will be raised at run time
28895 6. pragma Warnings (Off);
28896 7. Val_2 : constant Integer := ABE;
28897 8. pragma Warnings (On);
28899 10. function ABE return Integer is
28903 14. end Selective_Suppression;
28906 Note that suppressing elaboration warnings does not eliminate run-time
28907 checks. The example above will still fail at run time with an ABE.
28910 @node Summary of Procedures for Elaboration Control,Inspecting the Chosen Elaboration Order,Elaboration-related Compiler Switches,Elaboration Order Handling in GNAT
28911 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id13}@anchor{243}@anchor{gnat_ugn/elaboration_order_handling_in_gnat summary-of-procedures-for-elaboration-control}@anchor{244}
28912 @section Summary of Procedures for Elaboration Control
28915 A programmer should first compile the program with the default options, using
28916 none of the binder or compiler switches. If the binder succeeds in finding an
28917 elaboration order, then apart from possible cases involing dispatching calls
28918 and access-to-subprogram types, the program is free of elaboration errors.
28920 If it is important for the program to be portable to compilers other than GNAT,
28921 then the programmer should use compiler switch @code{-gnatel} and consider
28922 the messages about missing or implicitly created @code{Elaborate} and
28923 @code{Elaborate_All} pragmas.
28925 If the binder reports an elaboration circularity, the programmer has several
28932 Ensure that elaboration warnings are enabled. This will allow the static
28933 model to output trace information of elaboration issues. The trace
28934 information could shed light on previously unforeseen dependencies, as well
28935 as their origins. Elaboration warnings are enabled with compiler switch
28939 Cosider the tactics given in the suggestions section of the circularity
28943 If none of the steps outlined above resolve the circularity, use a more
28944 permissive elaboration model, in the following order:
28950 Use the pre-20.x legacy elaboration-order model, with binder switch
28954 Use both pre-18.x and pre-20.x legacy elaboration models, with compiler
28955 switch @code{-gnatH} and binder switch @code{-H}.
28958 Use the relaxed static elaboration model, with compiler switches
28959 @code{-gnatH} @code{-gnatJ} and binder switch @code{-H}.
28962 Use the relaxed dynamic elaboration model, with compiler switches
28963 @code{-gnatH} @code{-gnatJ} @code{-gnatE} and binder switch
28968 @node Inspecting the Chosen Elaboration Order,,Summary of Procedures for Elaboration Control,Elaboration Order Handling in GNAT
28969 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id14}@anchor{245}@anchor{gnat_ugn/elaboration_order_handling_in_gnat inspecting-the-chosen-elaboration-order}@anchor{246}
28970 @section Inspecting the Chosen Elaboration Order
28973 To see the elaboration order chosen by the binder, inspect the contents of file
28974 @cite{b~xxx.adb}. On certain targets, this file appears as @cite{b_xxx.adb}. The
28975 elaboration order appears as a sequence of calls to @code{Elab_Body} and
28976 @code{Elab_Spec}, interspersed with assignments to @cite{Exxx} which indicates that a
28977 particular unit is elaborated. For example:
28982 System.Soft_Links'Elab_Body;
28984 System.Secondary_Stack'Elab_Body;
28986 System.Exception_Table'Elab_Body;
28988 Ada.Io_Exceptions'Elab_Spec;
28990 Ada.Tags'Elab_Spec;
28991 Ada.Streams'Elab_Spec;
28993 Interfaces.C'Elab_Spec;
28995 System.Finalization_Root'Elab_Spec;
28997 System.Os_Lib'Elab_Body;
28999 System.Finalization_Implementation'Elab_Spec;
29000 System.Finalization_Implementation'Elab_Body;
29002 Ada.Finalization'Elab_Spec;
29004 Ada.Finalization.List_Controller'Elab_Spec;
29006 System.File_Control_Block'Elab_Spec;
29008 System.File_Io'Elab_Body;
29010 Ada.Tags'Elab_Body;
29012 Ada.Text_Io'Elab_Spec;
29013 Ada.Text_Io'Elab_Body;
29018 Note also binder switch @code{-l}, which outputs the chosen elaboration
29019 order and provides a more readable form of the above:
29027 system.case_util (spec)
29028 system.case_util (body)
29029 system.concat_2 (spec)
29030 system.concat_2 (body)
29031 system.concat_3 (spec)
29032 system.concat_3 (body)
29033 system.htable (spec)
29034 system.parameters (spec)
29035 system.parameters (body)
29037 interfaces.c_streams (spec)
29038 interfaces.c_streams (body)
29039 system.restrictions (spec)
29040 system.restrictions (body)
29041 system.standard_library (spec)
29042 system.exceptions (spec)
29043 system.exceptions (body)
29044 system.storage_elements (spec)
29045 system.storage_elements (body)
29046 system.secondary_stack (spec)
29047 system.stack_checking (spec)
29048 system.stack_checking (body)
29049 system.string_hash (spec)
29050 system.string_hash (body)
29051 system.htable (body)
29052 system.strings (spec)
29053 system.strings (body)
29054 system.traceback (spec)
29055 system.traceback (body)
29056 system.traceback_entries (spec)
29057 system.traceback_entries (body)
29058 ada.exceptions (spec)
29059 ada.exceptions.last_chance_handler (spec)
29060 system.soft_links (spec)
29061 system.soft_links (body)
29062 ada.exceptions.last_chance_handler (body)
29063 system.secondary_stack (body)
29064 system.exception_table (spec)
29065 system.exception_table (body)
29066 ada.io_exceptions (spec)
29069 interfaces.c (spec)
29070 interfaces.c (body)
29071 system.finalization_root (spec)
29072 system.finalization_root (body)
29073 system.memory (spec)
29074 system.memory (body)
29075 system.standard_library (body)
29076 system.os_lib (spec)
29077 system.os_lib (body)
29078 system.unsigned_types (spec)
29079 system.stream_attributes (spec)
29080 system.stream_attributes (body)
29081 system.finalization_implementation (spec)
29082 system.finalization_implementation (body)
29083 ada.finalization (spec)
29084 ada.finalization (body)
29085 ada.finalization.list_controller (spec)
29086 ada.finalization.list_controller (body)
29087 system.file_control_block (spec)
29088 system.file_io (spec)
29089 system.file_io (body)
29090 system.val_uns (spec)
29091 system.val_util (spec)
29092 system.val_util (body)
29093 system.val_uns (body)
29094 system.wch_con (spec)
29095 system.wch_con (body)
29096 system.wch_cnv (spec)
29097 system.wch_jis (spec)
29098 system.wch_jis (body)
29099 system.wch_cnv (body)
29100 system.wch_stw (spec)
29101 system.wch_stw (body)
29103 ada.exceptions (body)
29111 @node Inline Assembler,GNU Free Documentation License,Elaboration Order Handling in GNAT,Top
29112 @anchor{gnat_ugn/inline_assembler inline-assembler}@anchor{10}@anchor{gnat_ugn/inline_assembler doc}@anchor{247}@anchor{gnat_ugn/inline_assembler id1}@anchor{248}
29113 @chapter Inline Assembler
29116 @geindex Inline Assembler
29118 If you need to write low-level software that interacts directly
29119 with the hardware, Ada provides two ways to incorporate assembly
29120 language code into your program. First, you can import and invoke
29121 external routines written in assembly language, an Ada feature fully
29122 supported by GNAT. However, for small sections of code it may be simpler
29123 or more efficient to include assembly language statements directly
29124 in your Ada source program, using the facilities of the implementation-defined
29125 package @code{System.Machine_Code}, which incorporates the gcc
29126 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29127 including the following:
29133 No need to use non-Ada tools
29136 Consistent interface over different targets
29139 Automatic usage of the proper calling conventions
29142 Access to Ada constants and variables
29145 Definition of intrinsic routines
29148 Possibility of inlining a subprogram comprising assembler code
29151 Code optimizer can take Inline Assembler code into account
29154 This appendix presents a series of examples to show you how to use
29155 the Inline Assembler. Although it focuses on the Intel x86,
29156 the general approach applies also to other processors.
29157 It is assumed that you are familiar with Ada
29158 and with assembly language programming.
29161 * Basic Assembler Syntax::
29162 * A Simple Example of Inline Assembler::
29163 * Output Variables in Inline Assembler::
29164 * Input Variables in Inline Assembler::
29165 * Inlining Inline Assembler Code::
29166 * Other Asm Functionality::
29170 @node Basic Assembler Syntax,A Simple Example of Inline Assembler,,Inline Assembler
29171 @anchor{gnat_ugn/inline_assembler id2}@anchor{249}@anchor{gnat_ugn/inline_assembler basic-assembler-syntax}@anchor{24a}
29172 @section Basic Assembler Syntax
29175 The assembler used by GNAT and gcc is based not on the Intel assembly
29176 language, but rather on a language that descends from the AT&T Unix
29177 assembler @code{as} (and which is often referred to as 'AT&T syntax').
29178 The following table summarizes the main features of @code{as} syntax
29179 and points out the differences from the Intel conventions.
29180 See the gcc @code{as} and @code{gas} (an @code{as} macro
29181 pre-processor) documentation for further information.
29185 @emph{Register names}@w{ }
29187 gcc / @code{as}: Prefix with '%'; for example @code{%eax}@w{ }
29188 Intel: No extra punctuation; for example @code{eax}@w{ }
29196 @emph{Immediate operand}@w{ }
29198 gcc / @code{as}: Prefix with '$'; for example @code{$4}@w{ }
29199 Intel: No extra punctuation; for example @code{4}@w{ }
29207 @emph{Address}@w{ }
29209 gcc / @code{as}: Prefix with '$'; for example @code{$loc}@w{ }
29210 Intel: No extra punctuation; for example @code{loc}@w{ }
29218 @emph{Memory contents}@w{ }
29220 gcc / @code{as}: No extra punctuation; for example @code{loc}@w{ }
29221 Intel: Square brackets; for example @code{[loc]}@w{ }
29229 @emph{Register contents}@w{ }
29231 gcc / @code{as}: Parentheses; for example @code{(%eax)}@w{ }
29232 Intel: Square brackets; for example @code{[eax]}@w{ }
29240 @emph{Hexadecimal numbers}@w{ }
29242 gcc / @code{as}: Leading '0x' (C language syntax); for example @code{0xA0}@w{ }
29243 Intel: Trailing 'h'; for example @code{A0h}@w{ }
29251 @emph{Operand size}@w{ }
29253 gcc / @code{as}: Explicit in op code; for example @code{movw} to move a 16-bit word@w{ }
29254 Intel: Implicit, deduced by assembler; for example @code{mov}@w{ }
29262 @emph{Instruction repetition}@w{ }
29264 gcc / @code{as}: Split into two lines; for example@w{ }
29269 Intel: Keep on one line; for example @code{rep stosl}@w{ }
29277 @emph{Order of operands}@w{ }
29279 gcc / @code{as}: Source first; for example @code{movw $4, %eax}@w{ }
29280 Intel: Destination first; for example @code{mov eax, 4}@w{ }
29286 @node A Simple Example of Inline Assembler,Output Variables in Inline Assembler,Basic Assembler Syntax,Inline Assembler
29287 @anchor{gnat_ugn/inline_assembler a-simple-example-of-inline-assembler}@anchor{24b}@anchor{gnat_ugn/inline_assembler id3}@anchor{24c}
29288 @section A Simple Example of Inline Assembler
29291 The following example will generate a single assembly language statement,
29292 @code{nop}, which does nothing. Despite its lack of run-time effect,
29293 the example will be useful in illustrating the basics of
29294 the Inline Assembler facility.
29299 with System.Machine_Code; use System.Machine_Code;
29300 procedure Nothing is
29307 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29308 here it takes one parameter, a @emph{template string} that must be a static
29309 expression and that will form the generated instruction.
29310 @code{Asm} may be regarded as a compile-time procedure that parses
29311 the template string and additional parameters (none here),
29312 from which it generates a sequence of assembly language instructions.
29314 The examples in this chapter will illustrate several of the forms
29315 for invoking @code{Asm}; a complete specification of the syntax
29316 is found in the @code{Machine_Code_Insertions} section of the
29317 @cite{GNAT Reference Manual}.
29319 Under the standard GNAT conventions, the @code{Nothing} procedure
29320 should be in a file named @code{nothing.adb}.
29321 You can build the executable in the usual way:
29330 However, the interesting aspect of this example is not its run-time behavior
29331 but rather the generated assembly code.
29332 To see this output, invoke the compiler as follows:
29337 $ gcc -c -S -fomit-frame-pointer -gnatp nothing.adb
29341 where the options are:
29352 compile only (no bind or link)
29361 generate assembler listing
29368 @item @code{-fomit-frame-pointer}
29370 do not set up separate stack frames
29377 @item @code{-gnatp}
29379 do not add runtime checks
29383 This gives a human-readable assembler version of the code. The resulting
29384 file will have the same name as the Ada source file, but with a @code{.s}
29385 extension. In our example, the file @code{nothing.s} has the following
29391 .file "nothing.adb"
29393 ___gnu_compiled_ada:
29396 .globl __ada_nothing
29408 The assembly code you included is clearly indicated by
29409 the compiler, between the @code{#APP} and @code{#NO_APP}
29410 delimiters. The character before the 'APP' and 'NOAPP'
29411 can differ on different targets. For example, GNU/Linux uses '#APP' while
29412 on NT you will see '/APP'.
29414 If you make a mistake in your assembler code (such as using the
29415 wrong size modifier, or using a wrong operand for the instruction) GNAT
29416 will report this error in a temporary file, which will be deleted when
29417 the compilation is finished. Generating an assembler file will help
29418 in such cases, since you can assemble this file separately using the
29419 @code{as} assembler that comes with gcc.
29421 Assembling the file using the command
29430 will give you error messages whose lines correspond to the assembler
29431 input file, so you can easily find and correct any mistakes you made.
29432 If there are no errors, @code{as} will generate an object file
29433 @code{nothing.out}.
29435 @node Output Variables in Inline Assembler,Input Variables in Inline Assembler,A Simple Example of Inline Assembler,Inline Assembler
29436 @anchor{gnat_ugn/inline_assembler id4}@anchor{24d}@anchor{gnat_ugn/inline_assembler output-variables-in-inline-assembler}@anchor{24e}
29437 @section Output Variables in Inline Assembler
29440 The examples in this section, showing how to access the processor flags,
29441 illustrate how to specify the destination operands for assembly language
29447 with Interfaces; use Interfaces;
29448 with Ada.Text_IO; use Ada.Text_IO;
29449 with System.Machine_Code; use System.Machine_Code;
29450 procedure Get_Flags is
29451 Flags : Unsigned_32;
29454 Asm ("pushfl" & LF & HT & -- push flags on stack
29455 "popl %%eax" & LF & HT & -- load eax with flags
29456 "movl %%eax, %0", -- store flags in variable
29457 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29458 Put_Line ("Flags register:" & Flags'Img);
29463 In order to have a nicely aligned assembly listing, we have separated
29464 multiple assembler statements in the Asm template string with linefeed
29465 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29466 The resulting section of the assembly output file is:
29474 movl %eax, -40(%ebp)
29479 It would have been legal to write the Asm invocation as:
29484 Asm ("pushfl popl %%eax movl %%eax, %0")
29488 but in the generated assembler file, this would come out as:
29494 pushfl popl %eax movl %eax, -40(%ebp)
29499 which is not so convenient for the human reader.
29501 We use Ada comments
29502 at the end of each line to explain what the assembler instructions
29503 actually do. This is a useful convention.
29505 When writing Inline Assembler instructions, you need to precede each register
29506 and variable name with a percent sign. Since the assembler already requires
29507 a percent sign at the beginning of a register name, you need two consecutive
29508 percent signs for such names in the Asm template string, thus @code{%%eax}.
29509 In the generated assembly code, one of the percent signs will be stripped off.
29511 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29512 variables: operands you later define using @code{Input} or @code{Output}
29513 parameters to @code{Asm}.
29514 An output variable is illustrated in
29515 the third statement in the Asm template string:
29524 The intent is to store the contents of the eax register in a variable that can
29525 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29526 necessarily work, since the compiler might optimize by using a register
29527 to hold Flags, and the expansion of the @code{movl} instruction would not be
29528 aware of this optimization. The solution is not to store the result directly
29529 but rather to advise the compiler to choose the correct operand form;
29530 that is the purpose of the @code{%0} output variable.
29532 Information about the output variable is supplied in the @code{Outputs}
29533 parameter to @code{Asm}:
29538 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29542 The output is defined by the @code{Asm_Output} attribute of the target type;
29543 the general format is
29548 Type'Asm_Output (constraint_string, variable_name)
29552 The constraint string directs the compiler how
29553 to store/access the associated variable. In the example
29558 Unsigned_32'Asm_Output ("=m", Flags);
29562 the @code{"m"} (memory) constraint tells the compiler that the variable
29563 @code{Flags} should be stored in a memory variable, thus preventing
29564 the optimizer from keeping it in a register. In contrast,
29569 Unsigned_32'Asm_Output ("=r", Flags);
29573 uses the @code{"r"} (register) constraint, telling the compiler to
29574 store the variable in a register.
29576 If the constraint is preceded by the equal character '=', it tells
29577 the compiler that the variable will be used to store data into it.
29579 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29580 allowing the optimizer to choose whatever it deems best.
29582 There are a fairly large number of constraints, but the ones that are
29583 most useful (for the Intel x86 processor) are the following:
29588 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
29603 global (i.e., can be stored anywhere)
29675 use one of eax, ebx, ecx or edx
29683 use one of eax, ebx, ecx, edx, esi or edi
29689 The full set of constraints is described in the gcc and @code{as}
29690 documentation; note that it is possible to combine certain constraints
29691 in one constraint string.
29693 You specify the association of an output variable with an assembler operand
29694 through the @code{%@emph{n}} notation, where @emph{n} is a non-negative
29700 Asm ("pushfl" & LF & HT & -- push flags on stack
29701 "popl %%eax" & LF & HT & -- load eax with flags
29702 "movl %%eax, %0", -- store flags in variable
29703 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29707 @code{%0} will be replaced in the expanded code by the appropriate operand,
29709 the compiler decided for the @code{Flags} variable.
29711 In general, you may have any number of output variables:
29717 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29720 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29721 of @code{Asm_Output} attributes
29729 Asm ("movl %%eax, %0" & LF & HT &
29730 "movl %%ebx, %1" & LF & HT &
29732 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29733 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29734 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29738 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29739 in the Ada program.
29741 As a variation on the @code{Get_Flags} example, we can use the constraints
29742 string to direct the compiler to store the eax register into the @code{Flags}
29743 variable, instead of including the store instruction explicitly in the
29744 @code{Asm} template string:
29749 with Interfaces; use Interfaces;
29750 with Ada.Text_IO; use Ada.Text_IO;
29751 with System.Machine_Code; use System.Machine_Code;
29752 procedure Get_Flags_2 is
29753 Flags : Unsigned_32;
29756 Asm ("pushfl" & LF & HT & -- push flags on stack
29757 "popl %%eax", -- save flags in eax
29758 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29759 Put_Line ("Flags register:" & Flags'Img);
29764 The @code{"a"} constraint tells the compiler that the @code{Flags}
29765 variable will come from the eax register. Here is the resulting code:
29774 movl %eax,-40(%ebp)
29778 The compiler generated the store of eax into Flags after
29779 expanding the assembler code.
29781 Actually, there was no need to pop the flags into the eax register;
29782 more simply, we could just pop the flags directly into the program variable:
29787 with Interfaces; use Interfaces;
29788 with Ada.Text_IO; use Ada.Text_IO;
29789 with System.Machine_Code; use System.Machine_Code;
29790 procedure Get_Flags_3 is
29791 Flags : Unsigned_32;
29794 Asm ("pushfl" & LF & HT & -- push flags on stack
29795 "pop %0", -- save flags in Flags
29796 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29797 Put_Line ("Flags register:" & Flags'Img);
29802 @node Input Variables in Inline Assembler,Inlining Inline Assembler Code,Output Variables in Inline Assembler,Inline Assembler
29803 @anchor{gnat_ugn/inline_assembler id5}@anchor{24f}@anchor{gnat_ugn/inline_assembler input-variables-in-inline-assembler}@anchor{250}
29804 @section Input Variables in Inline Assembler
29807 The example in this section illustrates how to specify the source operands
29808 for assembly language statements.
29809 The program simply increments its input value by 1:
29814 with Interfaces; use Interfaces;
29815 with Ada.Text_IO; use Ada.Text_IO;
29816 with System.Machine_Code; use System.Machine_Code;
29817 procedure Increment is
29819 function Incr (Value : Unsigned_32) return Unsigned_32 is
29820 Result : Unsigned_32;
29823 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29824 Inputs => Unsigned_32'Asm_Input ("a", Value));
29828 Value : Unsigned_32;
29832 Put_Line ("Value before is" & Value'Img);
29833 Value := Incr (Value);
29834 Put_Line ("Value after is" & Value'Img);
29839 The @code{Outputs} parameter to @code{Asm} specifies
29840 that the result will be in the eax register and that it is to be stored
29841 in the @code{Result} variable.
29843 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29844 but with an @code{Asm_Input} attribute.
29845 The @code{"="} constraint, indicating an output value, is not present.
29847 You can have multiple input variables, in the same way that you can have more
29848 than one output variable.
29850 The parameter count (%0, %1) etc, still starts at the first output statement,
29851 and continues with the input statements.
29853 Just as the @code{Outputs} parameter causes the register to be stored into the
29854 target variable after execution of the assembler statements, so does the
29855 @code{Inputs} parameter cause its variable to be loaded into the register
29856 before execution of the assembler statements.
29858 Thus the effect of the @code{Asm} invocation is:
29864 load the 32-bit value of @code{Value} into eax
29867 execute the @code{incl %eax} instruction
29870 store the contents of eax into the @code{Result} variable
29873 The resulting assembler file (with @code{-O2} optimization) contains:
29878 _increment__incr.1:
29891 @node Inlining Inline Assembler Code,Other Asm Functionality,Input Variables in Inline Assembler,Inline Assembler
29892 @anchor{gnat_ugn/inline_assembler id6}@anchor{251}@anchor{gnat_ugn/inline_assembler inlining-inline-assembler-code}@anchor{252}
29893 @section Inlining Inline Assembler Code
29896 For a short subprogram such as the @code{Incr} function in the previous
29897 section, the overhead of the call and return (creating / deleting the stack
29898 frame) can be significant, compared to the amount of code in the subprogram
29899 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29900 which directs the compiler to expand invocations of the subprogram at the
29901 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29902 Here is the resulting program:
29907 with Interfaces; use Interfaces;
29908 with Ada.Text_IO; use Ada.Text_IO;
29909 with System.Machine_Code; use System.Machine_Code;
29910 procedure Increment_2 is
29912 function Incr (Value : Unsigned_32) return Unsigned_32 is
29913 Result : Unsigned_32;
29916 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29917 Inputs => Unsigned_32'Asm_Input ("a", Value));
29920 pragma Inline (Increment);
29922 Value : Unsigned_32;
29926 Put_Line ("Value before is" & Value'Img);
29927 Value := Increment (Value);
29928 Put_Line ("Value after is" & Value'Img);
29933 Compile the program with both optimization (@code{-O2}) and inlining
29934 (@code{-gnatn}) enabled.
29936 The @code{Incr} function is still compiled as usual, but at the
29937 point in @code{Increment} where our function used to be called:
29943 call _increment__incr.1
29947 the code for the function body directly appears:
29960 thus saving the overhead of stack frame setup and an out-of-line call.
29962 @node Other Asm Functionality,,Inlining Inline Assembler Code,Inline Assembler
29963 @anchor{gnat_ugn/inline_assembler other-asm-functionality}@anchor{253}@anchor{gnat_ugn/inline_assembler id7}@anchor{254}
29964 @section Other @code{Asm} Functionality
29967 This section describes two important parameters to the @code{Asm}
29968 procedure: @code{Clobber}, which identifies register usage;
29969 and @code{Volatile}, which inhibits unwanted optimizations.
29972 * The Clobber Parameter::
29973 * The Volatile Parameter::
29977 @node The Clobber Parameter,The Volatile Parameter,,Other Asm Functionality
29978 @anchor{gnat_ugn/inline_assembler the-clobber-parameter}@anchor{255}@anchor{gnat_ugn/inline_assembler id8}@anchor{256}
29979 @subsection The @code{Clobber} Parameter
29982 One of the dangers of intermixing assembly language and a compiled language
29983 such as Ada is that the compiler needs to be aware of which registers are
29984 being used by the assembly code. In some cases, such as the earlier examples,
29985 the constraint string is sufficient to indicate register usage (e.g.,
29987 the eax register). But more generally, the compiler needs an explicit
29988 identification of the registers that are used by the Inline Assembly
29991 Using a register that the compiler doesn't know about
29992 could be a side effect of an instruction (like @code{mull}
29993 storing its result in both eax and edx).
29994 It can also arise from explicit register usage in your
29995 assembly code; for example:
30000 Asm ("movl %0, %%ebx" & LF & HT &
30002 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30003 Inputs => Unsigned_32'Asm_Input ("g", Var_In));
30007 where the compiler (since it does not analyze the @code{Asm} template string)
30008 does not know you are using the ebx register.
30010 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30011 to identify the registers that will be used by your assembly code:
30016 Asm ("movl %0, %%ebx" & LF & HT &
30018 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30019 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30024 The Clobber parameter is a static string expression specifying the
30025 register(s) you are using. Note that register names are @emph{not} prefixed
30026 by a percent sign. Also, if more than one register is used then their names
30027 are separated by commas; e.g., @code{"eax, ebx"}
30029 The @code{Clobber} parameter has several additional uses:
30035 Use 'register' name @code{cc} to indicate that flags might have changed
30038 Use 'register' name @code{memory} if you changed a memory location
30041 @node The Volatile Parameter,,The Clobber Parameter,Other Asm Functionality
30042 @anchor{gnat_ugn/inline_assembler the-volatile-parameter}@anchor{257}@anchor{gnat_ugn/inline_assembler id9}@anchor{258}
30043 @subsection The @code{Volatile} Parameter
30046 @geindex Volatile parameter
30048 Compiler optimizations in the presence of Inline Assembler may sometimes have
30049 unwanted effects. For example, when an @code{Asm} invocation with an input
30050 variable is inside a loop, the compiler might move the loading of the input
30051 variable outside the loop, regarding it as a one-time initialization.
30053 If this effect is not desired, you can disable such optimizations by setting
30054 the @code{Volatile} parameter to @code{True}; for example:
30059 Asm ("movl %0, %%ebx" & LF & HT &
30061 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30062 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30068 By default, @code{Volatile} is set to @code{False} unless there is no
30069 @code{Outputs} parameter.
30071 Although setting @code{Volatile} to @code{True} prevents unwanted
30072 optimizations, it will also disable other optimizations that might be
30073 important for efficiency. In general, you should set @code{Volatile}
30074 to @code{True} only if the compiler's optimizations have created
30077 @node GNU Free Documentation License,Index,Inline Assembler,Top
30078 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{259}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{25a}
30079 @chapter GNU Free Documentation License
30082 Version 1.3, 3 November 2008
30084 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
30085 @indicateurl{http://fsf.org/}
30087 Everyone is permitted to copy and distribute verbatim copies of this
30088 license document, but changing it is not allowed.
30092 The purpose of this License is to make a manual, textbook, or other
30093 functional and useful document "free" in the sense of freedom: to
30094 assure everyone the effective freedom to copy and redistribute it,
30095 with or without modifying it, either commercially or noncommercially.
30096 Secondarily, this License preserves for the author and publisher a way
30097 to get credit for their work, while not being considered responsible
30098 for modifications made by others.
30100 This License is a kind of "copyleft", which means that derivative
30101 works of the document must themselves be free in the same sense. It
30102 complements the GNU General Public License, which is a copyleft
30103 license designed for free software.
30105 We have designed this License in order to use it for manuals for free
30106 software, because free software needs free documentation: a free
30107 program should come with manuals providing the same freedoms that the
30108 software does. But this License is not limited to software manuals;
30109 it can be used for any textual work, regardless of subject matter or
30110 whether it is published as a printed book. We recommend this License
30111 principally for works whose purpose is instruction or reference.
30113 @strong{1. APPLICABILITY AND DEFINITIONS}
30115 This License applies to any manual or other work, in any medium, that
30116 contains a notice placed by the copyright holder saying it can be
30117 distributed under the terms of this License. Such a notice grants a
30118 world-wide, royalty-free license, unlimited in duration, to use that
30119 work under the conditions stated herein. The @strong{Document}, below,
30120 refers to any such manual or work. Any member of the public is a
30121 licensee, and is addressed as "@strong{you}". You accept the license if you
30122 copy, modify or distribute the work in a way requiring permission
30123 under copyright law.
30125 A "@strong{Modified Version}" of the Document means any work containing the
30126 Document or a portion of it, either copied verbatim, or with
30127 modifications and/or translated into another language.
30129 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
30130 the Document that deals exclusively with the relationship of the
30131 publishers or authors of the Document to the Document's overall subject
30132 (or to related matters) and contains nothing that could fall directly
30133 within that overall subject. (Thus, if the Document is in part a
30134 textbook of mathematics, a Secondary Section may not explain any
30135 mathematics.) The relationship could be a matter of historical
30136 connection with the subject or with related matters, or of legal,
30137 commercial, philosophical, ethical or political position regarding
30140 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
30141 are designated, as being those of Invariant Sections, in the notice
30142 that says that the Document is released under this License. If a
30143 section does not fit the above definition of Secondary then it is not
30144 allowed to be designated as Invariant. The Document may contain zero
30145 Invariant Sections. If the Document does not identify any Invariant
30146 Sections then there are none.
30148 The "@strong{Cover Texts}" are certain short passages of text that are listed,
30149 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
30150 the Document is released under this License. A Front-Cover Text may
30151 be at most 5 words, and a Back-Cover Text may be at most 25 words.
30153 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
30154 represented in a format whose specification is available to the
30155 general public, that is suitable for revising the document
30156 straightforwardly with generic text editors or (for images composed of
30157 pixels) generic paint programs or (for drawings) some widely available
30158 drawing editor, and that is suitable for input to text formatters or
30159 for automatic translation to a variety of formats suitable for input
30160 to text formatters. A copy made in an otherwise Transparent file
30161 format whose markup, or absence of markup, has been arranged to thwart
30162 or discourage subsequent modification by readers is not Transparent.
30163 An image format is not Transparent if used for any substantial amount
30164 of text. A copy that is not "Transparent" is called @strong{Opaque}.
30166 Examples of suitable formats for Transparent copies include plain
30167 ASCII without markup, Texinfo input format, LaTeX input format, SGML
30168 or XML using a publicly available DTD, and standard-conforming simple
30169 HTML, PostScript or PDF designed for human modification. Examples of
30170 transparent image formats include PNG, XCF and JPG. Opaque formats
30171 include proprietary formats that can be read and edited only by
30172 proprietary word processors, SGML or XML for which the DTD and/or
30173 processing tools are not generally available, and the
30174 machine-generated HTML, PostScript or PDF produced by some word
30175 processors for output purposes only.
30177 The "@strong{Title Page}" means, for a printed book, the title page itself,
30178 plus such following pages as are needed to hold, legibly, the material
30179 this License requires to appear in the title page. For works in
30180 formats which do not have any title page as such, "Title Page" means
30181 the text near the most prominent appearance of the work's title,
30182 preceding the beginning of the body of the text.
30184 The "@strong{publisher}" means any person or entity that distributes
30185 copies of the Document to the public.
30187 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
30188 title either is precisely XYZ or contains XYZ in parentheses following
30189 text that translates XYZ in another language. (Here XYZ stands for a
30190 specific section name mentioned below, such as "@strong{Acknowledgements}",
30191 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
30192 To "@strong{Preserve the Title}"
30193 of such a section when you modify the Document means that it remains a
30194 section "Entitled XYZ" according to this definition.
30196 The Document may include Warranty Disclaimers next to the notice which
30197 states that this License applies to the Document. These Warranty
30198 Disclaimers are considered to be included by reference in this
30199 License, but only as regards disclaiming warranties: any other
30200 implication that these Warranty Disclaimers may have is void and has
30201 no effect on the meaning of this License.
30203 @strong{2. VERBATIM COPYING}
30205 You may copy and distribute the Document in any medium, either
30206 commercially or noncommercially, provided that this License, the
30207 copyright notices, and the license notice saying this License applies
30208 to the Document are reproduced in all copies, and that you add no other
30209 conditions whatsoever to those of this License. You may not use
30210 technical measures to obstruct or control the reading or further
30211 copying of the copies you make or distribute. However, you may accept
30212 compensation in exchange for copies. If you distribute a large enough
30213 number of copies you must also follow the conditions in section 3.
30215 You may also lend copies, under the same conditions stated above, and
30216 you may publicly display copies.
30218 @strong{3. COPYING IN QUANTITY}
30220 If you publish printed copies (or copies in media that commonly have
30221 printed covers) of the Document, numbering more than 100, and the
30222 Document's license notice requires Cover Texts, you must enclose the
30223 copies in covers that carry, clearly and legibly, all these Cover
30224 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
30225 the back cover. Both covers must also clearly and legibly identify
30226 you as the publisher of these copies. The front cover must present
30227 the full title with all words of the title equally prominent and
30228 visible. You may add other material on the covers in addition.
30229 Copying with changes limited to the covers, as long as they preserve
30230 the title of the Document and satisfy these conditions, can be treated
30231 as verbatim copying in other respects.
30233 If the required texts for either cover are too voluminous to fit
30234 legibly, you should put the first ones listed (as many as fit
30235 reasonably) on the actual cover, and continue the rest onto adjacent
30238 If you publish or distribute Opaque copies of the Document numbering
30239 more than 100, you must either include a machine-readable Transparent
30240 copy along with each Opaque copy, or state in or with each Opaque copy
30241 a computer-network location from which the general network-using
30242 public has access to download using public-standard network protocols
30243 a complete Transparent copy of the Document, free of added material.
30244 If you use the latter option, you must take reasonably prudent steps,
30245 when you begin distribution of Opaque copies in quantity, to ensure
30246 that this Transparent copy will remain thus accessible at the stated
30247 location until at least one year after the last time you distribute an
30248 Opaque copy (directly or through your agents or retailers) of that
30249 edition to the public.
30251 It is requested, but not required, that you contact the authors of the
30252 Document well before redistributing any large number of copies, to give
30253 them a chance to provide you with an updated version of the Document.
30255 @strong{4. MODIFICATIONS}
30257 You may copy and distribute a Modified Version of the Document under
30258 the conditions of sections 2 and 3 above, provided that you release
30259 the Modified Version under precisely this License, with the Modified
30260 Version filling the role of the Document, thus licensing distribution
30261 and modification of the Modified Version to whoever possesses a copy
30262 of it. In addition, you must do these things in the Modified Version:
30268 Use in the Title Page (and on the covers, if any) a title distinct
30269 from that of the Document, and from those of previous versions
30270 (which should, if there were any, be listed in the History section
30271 of the Document). You may use the same title as a previous version
30272 if the original publisher of that version gives permission.
30275 List on the Title Page, as authors, one or more persons or entities
30276 responsible for authorship of the modifications in the Modified
30277 Version, together with at least five of the principal authors of the
30278 Document (all of its principal authors, if it has fewer than five),
30279 unless they release you from this requirement.
30282 State on the Title page the name of the publisher of the
30283 Modified Version, as the publisher.
30286 Preserve all the copyright notices of the Document.
30289 Add an appropriate copyright notice for your modifications
30290 adjacent to the other copyright notices.
30293 Include, immediately after the copyright notices, a license notice
30294 giving the public permission to use the Modified Version under the
30295 terms of this License, in the form shown in the Addendum below.
30298 Preserve in that license notice the full lists of Invariant Sections
30299 and required Cover Texts given in the Document's license notice.
30302 Include an unaltered copy of this License.
30305 Preserve the section Entitled "History", Preserve its Title, and add
30306 to it an item stating at least the title, year, new authors, and
30307 publisher of the Modified Version as given on the Title Page. If
30308 there is no section Entitled "History" in the Document, create one
30309 stating the title, year, authors, and publisher of the Document as
30310 given on its Title Page, then add an item describing the Modified
30311 Version as stated in the previous sentence.
30314 Preserve the network location, if any, given in the Document for
30315 public access to a Transparent copy of the Document, and likewise
30316 the network locations given in the Document for previous versions
30317 it was based on. These may be placed in the "History" section.
30318 You may omit a network location for a work that was published at
30319 least four years before the Document itself, or if the original
30320 publisher of the version it refers to gives permission.
30323 For any section Entitled "Acknowledgements" or "Dedications",
30324 Preserve the Title of the section, and preserve in the section all
30325 the substance and tone of each of the contributor acknowledgements
30326 and/or dedications given therein.
30329 Preserve all the Invariant Sections of the Document,
30330 unaltered in their text and in their titles. Section numbers
30331 or the equivalent are not considered part of the section titles.
30334 Delete any section Entitled "Endorsements". Such a section
30335 may not be included in the Modified Version.
30338 Do not retitle any existing section to be Entitled "Endorsements"
30339 or to conflict in title with any Invariant Section.
30342 Preserve any Warranty Disclaimers.
30345 If the Modified Version includes new front-matter sections or
30346 appendices that qualify as Secondary Sections and contain no material
30347 copied from the Document, you may at your option designate some or all
30348 of these sections as invariant. To do this, add their titles to the
30349 list of Invariant Sections in the Modified Version's license notice.
30350 These titles must be distinct from any other section titles.
30352 You may add a section Entitled "Endorsements", provided it contains
30353 nothing but endorsements of your Modified Version by various
30354 parties---for example, statements of peer review or that the text has
30355 been approved by an organization as the authoritative definition of a
30358 You may add a passage of up to five words as a Front-Cover Text, and a
30359 passage of up to 25 words as a Back-Cover Text, to the end of the list
30360 of Cover Texts in the Modified Version. Only one passage of
30361 Front-Cover Text and one of Back-Cover Text may be added by (or
30362 through arrangements made by) any one entity. If the Document already
30363 includes a cover text for the same cover, previously added by you or
30364 by arrangement made by the same entity you are acting on behalf of,
30365 you may not add another; but you may replace the old one, on explicit
30366 permission from the previous publisher that added the old one.
30368 The author(s) and publisher(s) of the Document do not by this License
30369 give permission to use their names for publicity for or to assert or
30370 imply endorsement of any Modified Version.
30372 @strong{5. COMBINING DOCUMENTS}
30374 You may combine the Document with other documents released under this
30375 License, under the terms defined in section 4 above for modified
30376 versions, provided that you include in the combination all of the
30377 Invariant Sections of all of the original documents, unmodified, and
30378 list them all as Invariant Sections of your combined work in its
30379 license notice, and that you preserve all their Warranty Disclaimers.
30381 The combined work need only contain one copy of this License, and
30382 multiple identical Invariant Sections may be replaced with a single
30383 copy. If there are multiple Invariant Sections with the same name but
30384 different contents, make the title of each such section unique by
30385 adding at the end of it, in parentheses, the name of the original
30386 author or publisher of that section if known, or else a unique number.
30387 Make the same adjustment to the section titles in the list of
30388 Invariant Sections in the license notice of the combined work.
30390 In the combination, you must combine any sections Entitled "History"
30391 in the various original documents, forming one section Entitled
30392 "History"; likewise combine any sections Entitled "Acknowledgements",
30393 and any sections Entitled "Dedications". You must delete all sections
30394 Entitled "Endorsements".
30396 @strong{6. COLLECTIONS OF DOCUMENTS}
30398 You may make a collection consisting of the Document and other documents
30399 released under this License, and replace the individual copies of this
30400 License in the various documents with a single copy that is included in
30401 the collection, provided that you follow the rules of this License for
30402 verbatim copying of each of the documents in all other respects.
30404 You may extract a single document from such a collection, and distribute
30405 it individually under this License, provided you insert a copy of this
30406 License into the extracted document, and follow this License in all
30407 other respects regarding verbatim copying of that document.
30409 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
30411 A compilation of the Document or its derivatives with other separate
30412 and independent documents or works, in or on a volume of a storage or
30413 distribution medium, is called an "aggregate" if the copyright
30414 resulting from the compilation is not used to limit the legal rights
30415 of the compilation's users beyond what the individual works permit.
30416 When the Document is included in an aggregate, this License does not
30417 apply to the other works in the aggregate which are not themselves
30418 derivative works of the Document.
30420 If the Cover Text requirement of section 3 is applicable to these
30421 copies of the Document, then if the Document is less than one half of
30422 the entire aggregate, the Document's Cover Texts may be placed on
30423 covers that bracket the Document within the aggregate, or the
30424 electronic equivalent of covers if the Document is in electronic form.
30425 Otherwise they must appear on printed covers that bracket the whole
30428 @strong{8. TRANSLATION}
30430 Translation is considered a kind of modification, so you may
30431 distribute translations of the Document under the terms of section 4.
30432 Replacing Invariant Sections with translations requires special
30433 permission from their copyright holders, but you may include
30434 translations of some or all Invariant Sections in addition to the
30435 original versions of these Invariant Sections. You may include a
30436 translation of this License, and all the license notices in the
30437 Document, and any Warranty Disclaimers, provided that you also include
30438 the original English version of this License and the original versions
30439 of those notices and disclaimers. In case of a disagreement between
30440 the translation and the original version of this License or a notice
30441 or disclaimer, the original version will prevail.
30443 If a section in the Document is Entitled "Acknowledgements",
30444 "Dedications", or "History", the requirement (section 4) to Preserve
30445 its Title (section 1) will typically require changing the actual
30448 @strong{9. TERMINATION}
30450 You may not copy, modify, sublicense, or distribute the Document
30451 except as expressly provided under this License. Any attempt
30452 otherwise to copy, modify, sublicense, or distribute it is void, and
30453 will automatically terminate your rights under this License.
30455 However, if you cease all violation of this License, then your license
30456 from a particular copyright holder is reinstated (a) provisionally,
30457 unless and until the copyright holder explicitly and finally
30458 terminates your license, and (b) permanently, if the copyright holder
30459 fails to notify you of the violation by some reasonable means prior to
30460 60 days after the cessation.
30462 Moreover, your license from a particular copyright holder is
30463 reinstated permanently if the copyright holder notifies you of the
30464 violation by some reasonable means, this is the first time you have
30465 received notice of violation of this License (for any work) from that
30466 copyright holder, and you cure the violation prior to 30 days after
30467 your receipt of the notice.
30469 Termination of your rights under this section does not terminate the
30470 licenses of parties who have received copies or rights from you under
30471 this License. If your rights have been terminated and not permanently
30472 reinstated, receipt of a copy of some or all of the same material does
30473 not give you any rights to use it.
30475 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
30477 The Free Software Foundation may publish new, revised versions
30478 of the GNU Free Documentation License from time to time. Such new
30479 versions will be similar in spirit to the present version, but may
30480 differ in detail to address new problems or concerns. See
30481 @indicateurl{http://www.gnu.org/copyleft/}.
30483 Each version of the License is given a distinguishing version number.
30484 If the Document specifies that a particular numbered version of this
30485 License "or any later version" applies to it, you have the option of
30486 following the terms and conditions either of that specified version or
30487 of any later version that has been published (not as a draft) by the
30488 Free Software Foundation. If the Document does not specify a version
30489 number of this License, you may choose any version ever published (not
30490 as a draft) by the Free Software Foundation. If the Document
30491 specifies that a proxy can decide which future versions of this
30492 License can be used, that proxy's public statement of acceptance of a
30493 version permanently authorizes you to choose that version for the
30496 @strong{11. RELICENSING}
30498 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
30499 World Wide Web server that publishes copyrightable works and also
30500 provides prominent facilities for anybody to edit those works. A
30501 public wiki that anybody can edit is an example of such a server. A
30502 "Massive Multiauthor Collaboration" (or "MMC") contained in the
30503 site means any set of copyrightable works thus published on the MMC
30506 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
30507 license published by Creative Commons Corporation, a not-for-profit
30508 corporation with a principal place of business in San Francisco,
30509 California, as well as future copyleft versions of that license
30510 published by that same organization.
30512 "Incorporate" means to publish or republish a Document, in whole or
30513 in part, as part of another Document.
30515 An MMC is "eligible for relicensing" if it is licensed under this
30516 License, and if all works that were first published under this License
30517 somewhere other than this MMC, and subsequently incorporated in whole
30518 or in part into the MMC, (1) had no cover texts or invariant sections,
30519 and (2) were thus incorporated prior to November 1, 2008.
30521 The operator of an MMC Site may republish an MMC contained in the site
30522 under CC-BY-SA on the same site at any time before August 1, 2009,
30523 provided the MMC is eligible for relicensing.
30525 @strong{ADDENDUM: How to use this License for your documents}
30527 To use this License in a document you have written, include a copy of
30528 the License in the document and put the following copyright and
30529 license notices just after the title page:
30533 Copyright © YEAR YOUR NAME.
30534 Permission is granted to copy, distribute and/or modify this document
30535 under the terms of the GNU Free Documentation License, Version 1.3
30536 or any later version published by the Free Software Foundation;
30537 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
30538 A copy of the license is included in the section entitled "GNU
30539 Free Documentation License".
30542 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
30543 replace the "with ... Texts." line with this:
30547 with the Invariant Sections being LIST THEIR TITLES, with the
30548 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
30551 If you have Invariant Sections without Cover Texts, or some other
30552 combination of the three, merge those two alternatives to suit the
30555 If your document contains nontrivial examples of program code, we
30556 recommend releasing these examples in parallel under your choice of
30557 free software license, such as the GNU General Public License,
30558 to permit their use in free software.
30560 @node Index,,GNU Free Documentation License,Top
30567 @anchor{gnat_ugn/gnat_utility_programs switches-related-to-project-files}@w{ }