1. About This Guide

For ease of exposition, ‘GNAT Pro’ will be referred to simply as ‘GNAT’ in the remainder of this document.

This guide describes the use of GNAT, a compiler and software development toolset for the full Ada programming language. It documents the features of the compiler and tools, and explains how to use them to build Ada applications.

GNAT implements Ada 95, Ada 2005, Ada 2012, and Ada 2022. You may also invoke it in Ada 83 compatibility mode. By default, GNAT assumes Ada 2012, but you can use a compiler switch (Compiling Different Versions of Ada) to explicitly specify the language version. Throughout this manual, references to ‘Ada’ without a year suffix apply to all versions of the Ada language starting with Ada 95.

GNAT supports both the GCC and LLVM back end compilation families. Most GNAT versions use the GCC back end, but some are now available using the LLVM back end. In some places in this manual, we distinguish between the two back ends, but in most cases, everything in this manual applies to both back ends. We refer to GNAT with the LLVM back end as ‘GNAT LLVM’. See GNAT with the LLVM Back End for limitations of GNAT LLVM.

1.1. What This Guide Contains

This guide contains the following chapters:

• Getting Started with GNAT describes how to get started compiling and running Ada programs with the GNAT Ada programming environment.

• The GNAT Compilation Model describes the compilation model used by GNAT.

• Building Executable Programs with GNAT describes how to use the main GNAT tools to build executable programs, and it also gives examples of using the GNU make utility with GNAT.

• GNAT Utility Programs explains the various utility programs that are included in the GNAT environment.

• GNAT and Program Execution covers a number of topics related to running, debugging, and tuning the performance of programs developed with GNAT.

Appendices cover several additional topics:

• Platform-Specific Information describes the different run-time library implementations and also presents information on how to use GNAT on several specific platforms.

• Example of Binder Output File shows the source code for the binder output file for a sample program.

• Elaboration Order Handling in GNAT describes how GNAT helps you deal with elaboration order issues.

• Inline Assembler shows how to use the inline assembly facility in an Ada program.

1.2. What You Should Know before Reading This Guide

This guide assumes a basic familiarity with the Ada 95 language, as described in the International Standard ANSI/ISO/IEC-8652:1995, January 1995. Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in the GNAT documentation package.

1.3. Related Information

For further information about Ada and related tools, please refer to the following documents:

• Ada 95 Reference Manual, Ada 2005 Reference Manual, and Ada 2012 Reference Manual, which contain reference material for the several revisions of the Ada language standard.

• GNAT Reference_Manual, which contains all reference material for the GNAT implementation of Ada.

• Using GNAT Studio, which describes the GNAT Studio Integrated Development Environment.

• GNAT Studio Tutorial, which introduces the main GNAT Studio features through examples.

• Debugging with GDB, for all details on the use of the GNU source-level debugger.

• GNU Emacs Manual, for full information on the extensible editor and programming environment Emacs.

1.4. Conventions

Following are examples of the typographical and graphic conventions used in this guide:

• Functions, utility program names, standard names, and classes.

• Option flags

• File names

• Variables

• Emphasis

• [optional information or parameters]

• Examples are described by text

  and then shown this way.
  

• Commands that you enter are shown as preceded by a prompt string comprising the $ character followed by a space.

• Full file names are shown with the ‘/’ character as the directory separator; e.g., parent-dir/subdir/myfile.adb. If you are using GNAT on a Windows platform, please note that you should use the ‘\’ character instead.