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Autoconf

This manual (4 December 2023) is for GNU Autoconf (version 2.72), a package for creating scripts to configure source code packages using templates and an M4 macro package.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License.”

1 Introduction
2 The GNU Build System
- 2.1 Automake
- 2.2 Gnulib
- 2.3 Libtool
- 2.4 Pointers
3 Making configure Scripts
- 3.1 Writing configure.ac
- 3.2 Using autoscan to Create configure.ac
- 3.3 Using ifnames to List Conditionals
- 3.4 Using autoconf to Create configure
- 3.5 Using autoreconf to Update configure Scripts
4 Initialization and Output Files
- 4.1 Initializing configure
- 4.2 Dealing with Autoconf versions
- 4.3 Notices in configure
- 4.4 Configure Input: Source Code, Macros, and Auxiliary Files
- 4.5 Outputting Files
- 4.6 Performing Configuration Actions
- 4.7 Creating Configuration Files
- 4.8 Substitutions in Makefiles
- 4.9 Configuration Header Files
- 4.10 Running Arbitrary Configuration Commands
- 4.11 Creating Configuration Links
- 4.12 Configuring Other Packages in Subdirectories
- 4.13 Default Prefix
5 Existing Tests
- 5.1 Common Behavior
  - 5.1.1 Standard Symbols
  - 5.1.2 Default Includes
- 5.2 Alternative Programs
  - 5.2.1 Particular Program Checks
  - 5.2.2 Generic Program and File Checks
- 5.3 Files
- 5.4 Library Files
- 5.5 Library Functions
- 5.6 Header Files
- 5.7 Declarations
  - 5.7.1 Particular Declaration Checks
  - 5.7.2 Generic Declaration Checks
- 5.8 Structures
  - 5.8.1 Particular Structure Checks
  - 5.8.2 Generic Structure Checks
- 5.9 Types
  - 5.9.1 Particular Type Checks
  - 5.9.2 Generic Type Checks
- 5.10 Compilers and Preprocessors
- 5.11 System Services
- 5.12 C and Posix Variants
- 5.13 Erlang Libraries
6 Writing Tests
- 6.1 Language Choice
- 6.2 Writing Test Programs
- 6.3 Running the Preprocessor
- 6.4 Running the Compiler
- 6.5 Running the Linker
- 6.6 Checking Runtime Behavior
- 6.7 Systemology
- 6.8 Multiple Cases
7 Results of Tests
- 7.1 Defining C Preprocessor Symbols
- 7.2 Setting Output Variables
- 7.3 Special Characters in Output Variables
- 7.4 Caching Results
- 7.5 Printing Messages
8 Programming in M4
- 8.1 M4 Quotation
- 8.2 Using autom4te
  - 8.2.1 Invoking autom4te
  - 8.2.2 Customizing autom4te
- 8.3 Programming in M4sugar
- 8.4 Debugging via autom4te
9 Programming in M4sh
- 9.1 Common Shell Constructs
- 9.2 Support for indirect variable names
- 9.3 Initialization Macros
- 9.4 File Descriptor Macros
10 Writing Autoconf Macros
- 10.1 Macro Definitions
- 10.2 Macro Names
- 10.3 Dependencies Between Macros
- 10.4 Obsoleting Macros
- 10.5 Coding Style
11 Portable Shell Programming
- 11.1 Shellology
- 11.2 Invoking the Shell
- 11.3 Here-Documents
- 11.4 File Descriptors
- 11.5 Signal Handling
- 11.6 File System Conventions
- 11.7 Shell Pattern Matching
- 11.8 Shell Substitutions
- 11.9 Assignments
- 11.10 Parentheses in Shell Scripts
- 11.11 Slashes in Shell Scripts
- 11.12 Special Shell Variables
- 11.13 Shell Functions
- 11.14 Limitations of Shell Builtins
- 11.15 Limitations of Usual Tools
12 Portable Make Programming
- 12.1 $< in Ordinary Make Rules
- 12.2 Failure in Make Rules
- 12.3 Special Characters in Make Macro Names
- 12.4 Backslash-Newline Before Empty Lines
- 12.5 Backslash-Newline in Make Comments
- 12.6 Long Lines in Makefiles
- 12.7 make macro=value and Submakes
- 12.8 The Make Macro MAKEFLAGS
- 12.9 The Make Macro SHELL
- 12.10 Parallel Make
- 12.11 Comments in Make Rules
- 12.12 Newlines in Make Rules
- 12.13 Comments in Make Macros
- 12.14 Trailing whitespace in Make Macros
- 12.15 Command-line Macros and whitespace
- 12.16 The obj/ Subdirectory and Make
- 12.17 Exit Status of make -k
- 12.18 VPATH and Make
  - 12.18.1 Variables listed in VPATH
  - 12.18.2 VPATH and Double-colon Rules
  - 12.18.3 $< Not Supported in Explicit Rules
  - 12.18.4 Automatic Rule Rewriting
  - 12.18.5 Tru64 make Creates Prerequisite Directories Magically
  - 12.18.6 Make Target Lookup
- 12.19 Single Suffix Rules and Separated Dependencies
- 12.20 Timestamp Resolution and Make
13 Portable C and C++ Programming
- 13.1 Varieties of Unportability
- 13.2 Integer Overflow
- 13.3 Preprocessor Arithmetic
- 13.4 Properties of Null Pointers
- 13.5 Buffer Overruns and Subscript Errors
- 13.6 Volatile Objects
- 13.7 Floating Point Portability
- 13.8 Exiting Portably
14 Manual Configuration
- 14.1 Specifying target triplets
- 14.2 Getting the Canonical System Type
- 14.3 Using the System Type
15 Site Configuration
- 15.1 Controlling Help Output
- 15.2 Working With External Software
- 15.3 Choosing Package Options
- 15.4 Making Your Help Strings Look Pretty
- 15.5 Controlling Checking of configure Options
- 15.6 Configuring Site Details
- 15.7 Transforming Program Names When Installing
- 15.8 Setting Site Defaults
16 Running configure Scripts
- 16.1 Basic Installation
- 16.2 Compilers and Options
- 16.3 Compiling For Multiple Architectures
- 16.4 Installation Names
- 16.5 Optional Features
- 16.6 Specifying a System Type
- 16.7 Sharing Defaults
- 16.8 Defining Variables
- 16.9 configure Invocation
17 config.status Invocation
18 Obsolete Constructs
- 18.1 Obsolete config.status Invocation
- 18.2 acconfig.h
- 18.3 Using autoupdate to Modernize configure.ac
- 18.4 Obsolete Macros
- 18.5 Upgrading From Version 1
- 18.6 Upgrading From Version 2.13
19 Generating Test Suites with Autotest
- 19.1 Using an Autotest Test Suite
  - 19.1.1 testsuite Scripts
  - 19.1.2 Autotest Logs
- 19.2 Writing testsuite.at
- 19.3 Running testsuite Scripts
- 19.4 Making testsuite Scripts
20 Frequent Autoconf Questions, with answers
- 20.1 Distributing configure Scripts
- 20.2 Why Require GNU M4?
- 20.3 How Can I Bootstrap?
- 20.4 Why Not Imake?
- 20.5 How Do I #define Installation Directories?
- 20.6 What is autom4te.cache?
- 20.7 Header Present But Cannot Be Compiled
- 20.8 Expanded Before Required
- 20.9 Debugging configure scripts
21 History of Autoconf
- 21.1 Genesis
- 21.2 Exodus
- 21.3 Leviticus
- 21.4 Numbers
- 21.5 Deuteronomy
Appendix A GNU Free Documentation License
Appendix B Indices
- B.1 Environment Variable Index
- B.2 Output Variable Index
- B.3 Preprocessor Symbol Index
- B.4 Cache Variable Index
- B.5 Autoconf Macro Index
- B.6 M4 Macro Index
- B.7 Autotest Macro Index
- B.8 Program and Function Index
- B.9 Concept Index

Autoconf

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