\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename autoconf.info @settitle Autoconf @c For double-sided printing, uncomment: @c @setchapternewpage odd @c %**end of header @set EDITION 1.97 @set VERSION 1.97 @set UPDATED August 1994 @iftex @finalout @end iftex @ifinfo @format START-INFO-DIR-ENTRY * autoconf: (autoconf). The Autoconf configuration system. END-INFO-DIR-ENTRY @end format This file documents the GNU Autoconf package for creating scripts to configure source code packages using templates and an @code{m4} macro package. Copyright (C) 1992, 1993, 1994 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. @ignore Permission is granted to process this file through TeX and print the results, provided the printed document carries copying permission notice identical to this one except for the removal of this paragraph (this paragraph not being relevant to the printed manual). @end ignore Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. @end ifinfo @titlepage @title Autoconf @subtitle Generating Automatic Configuration Scripts @subtitle Edition @value{EDITION}, for Autoconf version @value{VERSION} @subtitle @value{UPDATED} @author by David MacKenzie, Roland McGrath, and Noah Friedman @page @vskip 0pt plus 1filll Copyright @copyright{} 1992, 1993, 1994 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. @end titlepage @c Define a macro index that @@defmac doesn't write to. @defcodeindex ma @node Top, Introduction, , (dir) @comment node-name, next, previous, up @ifinfo This file documents the GNU Autoconf package for creating scripts to configure source code packages using templates and an @code{m4} macro package. This is edition @value{EDITION}, for Autoconf version @value{VERSION}. @end ifinfo @c The master menu, created with texinfo-master-menu, goes here. @menu * Introduction:: Autoconf's purpose, strengths, and weaknesses. * Distributing:: Legal restrictions on Autoconf output. * Making configure Scripts:: How to organize and produce Autoconf scripts. * Specific Tests:: Macros that check for particular features. * General Purpose Macros:: Macros that check for kinds of features. * Manual Configuration:: Selecting features that can't be guessed. * Writing Macros:: How to add your own macros to Autoconf. * Caching Values:: Speeding up subsequent @code{configure} runs. * Makefiles:: Information Autoconf uses in @file{Makefile}s. * Invoking configure:: How to use the Autoconf output. * Invoking config.status:: Recreating a configuration. * Site Default Values:: Providing local defaults for @code{configure}. * Old Macro Names:: Backward compatibility macros. * Example:: Sample Autoconf input files. * Preprocessor Symbol Index:: Index of C preprocessor symbols defined. * Macro Index:: Index of Autoconf macros. --- The Detailed Node Listing --- Making @code{configure} Scripts * Writing configure.in:: What to put in an Autoconf input file. * Invoking autoconf:: How to create configuration scripts. * Invoking autoheader:: How to create configuration header files. * Invoking autoscan:: Semi-automatic @file{configure.in} writing. * Invoking ifnames:: Listing the conditionals in source code. * Invoking autoreconf:: Remaking multiple @code{configure} scripts. * Invoking autoupdate:: Replacing old macro names in @code{configure.in}. * Invoking shindent:: Making @code{configure} scripts more readable. Specific Tests * Alternative Programs:: Selecting between alternative programs. * Header Files:: Header files that might be missing. * Typedefs:: @code{typedef}s that might be missing. * Library Functions:: C library functions that might be missing. * Structures:: Structures or members that might be missing. * Compiler Characteristics:: C compiler or machine architecture features. * System Services:: Operating system services. * UNIX Variants:: Special cases for specific UNIX variants. General Purpose Macros * Setup:: Controlling Autoconf operation. * File Existence:: Checking whether particular files exist. * C Features:: Checking for features of the C system. * Command Line:: Checking command line arguments. * Setting Variables:: Setting shell and @code{make} variables. * Printing Messages:: Notifying users of progress or problems. * Language Choice:: Selecting which language to use for testing. * Macro Ordering:: Enforcing ordering constraints. Writing Macros * Macro Format:: Basic format of an Autoconf macro. * Macro Naming:: What to call your new macros. * Quoting:: Protecting macros from unwanted expansion. * Dependencies Between Macros:: What to do when macros depend on other macros. * Checking for Files:: Finding whether a file exists. * Checking for Symbols:: Finding whether a symbol is defined. * Test Programs:: Writing programs to test for features. * Multiple Cases:: Tests for several possible values. Dependencies Between Macros * Prerequisite Macros:: Ensuring required information. * Suggested Ordering:: Warning about possible ordering problems. Test Programs * Guidelines:: General rules for writing test programs. * Tricks:: Special ways to work around problems. Caching Values * Cache Files:: Files @code{configure} uses for caching. * Cache Variables:: Shell variables used in caches. Makefiles * Predefined Variables:: Heavily used @code{make} variables. * VPATH Substitutions:: Compiling in a different directory. * Automatic Remaking:: Makefile rules for configuring. Running @code{configure} Scripts * Basic Installation:: Instructions for typical cases. * Compilers and Options:: Selecting compilers and optimization. * Build Directory:: Configuring in a different directory. * Installation Directories:: Installing in different directories. * System Type:: Specifying the system type. * Optional Features:: Selecting optional features. An Example * Sample configure.in:: An example of a @file{configure} template. * Sample Makefile.in:: An example of a @file{Makefile} template. @end menu @node Introduction, Distributing, Top, Top @chapter Introduction Autoconf is a tool for producing shell scripts that automatically configure software source code packages to adapt to many kinds of UNIX-like systems. The configuration scripts produced by Autoconf are independent of Autoconf when they are run, so their users do not need to have Autoconf. The configuration scripts produced by Autoconf normally require no manual user intervention when run; they do not even take an argument specifying the system type. Instead, they test for the presence of each feature that the software package they are for might need individually. (Before each check, they print a one-line message stating what they are checking for, so the user doesn't get too bored while waiting for the script to finish.) As a result, they deal well with systems that are hybrids or customized from the more common UNIX variants. There is no need to maintain files that list the features supported by each release of each variant of UNIX. For each software package that Autoconf is used with, it creates a configuration script from a template file that lists the operating system features that the package can use. After the shell code to recognize and respond to an operating system feature has been written, Autoconf allows it to be shared by many software packages that can use (or need) that feature. If it later turns out that the shell code needs adjustment for some reason, it needs to be changed in only one place; all of the the configuration scripts can be regenerated automatically to take advantage of the updated code. Larry Wall's Metaconfig package is similar in purpose to Autoconf, but is more general. The scripts it produces require manual user intervention, which is quite inconvenient when configuring large source trees. Unlike Metaconfig scripts, Autoconf scripts can support cross-compiling, if some care is taken in writing them. They should avoid executing test programs, since test programs compiled with a cross-compiler can not be executed on the host system. Also, they shouldn't do anything that tests features of the host system instead of the target system. Autoconf imposes some restrictions on the names of macros used with @code{#ifdef} in C programs (@pxref{Preprocessor Symbol Index}). Autoconf requires GNU @code{m4} in order to generate the scripts. It uses features that some UNIX versions of @code{m4} do not have. It also overflows internal limits of some versions of @code{m4}, including GNU @code{m4} 1.0; so use a later version of GNU @code{m4}. Autoconf does not work well with GNU C library releases before 1.06. The GNU C library contains stubs (which always return an error) for functions that are not available instead of omitting them from the library. As a result, Autoconf scripts are fooled into thinking that those functions are available. This problem does not exist with releases 1.06 and later of the GNU C library, which define C preprocessor macros that the Autoconf macros @code{AC_CHECK_FUNC} and @code{AC_REPLACE_FUNCS} test, indicating that certain functions are stubs (@pxref{C Features}, for more information on checking for functions). @ifinfo Autoconf was written by David MacKenzie, with help from Franc,ois @end ifinfo @tex Autoconf was written by David MacKenzie, with help from Fran\c cois @end tex Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor, Roland McGrath, Noah Friedman, and david d zuhn. It was inspired by Brian Fox's automatic configuration system for Bash, by Larry Wall's Metaconfig, and by Richard Stallman, Richard Pixley, and John Gilmore's configuration tools for the GNU compiler and object file utilities. Mail suggestions and bug reports for Autoconf to @code{bug-gnu-utils@@prep.ai.mit.edu}. Please include the Autoconf version number, which you can get by running @samp{autoconf --version}. @node Distributing, Making configure Scripts, Introduction, Top @chapter Distributing Autoconf Output The configuration scripts that Autoconf produces are covered by the GNU General Public License. This is because they consist almost entirely of parts of Autoconf itself, rearranged somewhat, and Autoconf is distributed under the terms of the GPL. As applied to Autoconf, the GPL just means that you need to distribute @file{configure.in}, and @file{aclocal.m4}, @file{acconfig.h}, and @file{@var{config}.h.top} and @file{@var{config}.h.bot} if you use them, along with @file{configure}. Programs that use Autoconf scripts to configure themselves do not automatically come under the GPL. Distributing an Autoconf configuration script as part of a program is considered to be @emph{mere aggregation} of that work with the Autoconf script. Such programs are not derivative works based on Autoconf; only their configuration scripts are. We still encourage software authors to distribute their work under terms like those of the GPL, but doing so is not required to use Autoconf. @node Making configure Scripts, Specific Tests, Distributing, Top @chapter Making @code{configure} Scripts The configuration scripts that Autoconf produces are by convention called @code{configure}. When run, @code{configure} creates several files, replacing configuration parameters in them with values appropriate for the system being configured. The files that @code{configure} creates are: @itemize @bullet @item one or more @file{Makefile} files (one in each subdirectory of the package), from template @file{Makefile.in} files (@pxref{Makefiles}); @item optionally, a C header file, the name of which is configurable, containing @code{#define} directives (@pxref{Setup}); @item a shell script called @file{config.status} that, when run, will recreate the files listed above (@pxref{Invoking config.status}); @item a shell script called @file{config.cache} that saves the results of running many of the tests; @item a file called @file{config.log} containing any messages produced by compilers, to help debugging if @code{configure} makes a mistake. @end itemize To create a @code{configure} script with Autoconf, you need to write an Autoconf input file (@file{configure.in}) and run Autoconf on it to produce the script. If you write your own feature tests to supplement those that come with Autoconf, you might also write a file called @file{aclocal.m4}. If you use a C header file to contain @code{#define} directives, you might also write @file{config.h.top}, @file{config.h.bot}, and @file{acconfig.h}, and you will distribute the Autoconf-generated file @file{config.h.in} with the package. Here is a diagram showing how the files that can be used in configuration are produced. Programs that are executed are suffixed by @samp{*}. Optional files are enclosed in square brackets (@samp{[]}). @code{autoconf} and @code{autoheader} also read the installed files @file{acgeneral.m4} and @file{acspecific.m4}, and also an installed @file{aclocal.m4} if it exists. @noindent Files used in preparing a software package for distribution: @example @group your source files --> [autoscan*] --> [configure.scan] --> configure.in configure.in --. .------> autoconf* -----> configure +---+ [aclocal.m4] --' `---. +--> [autoheader*] -> [config.h.in] [acconfig.h] ----. | +-----' [config.h.top] --+ [config.h.bot] --' Makefile.in -------------------------------> Makefile.in @end group @end example @noindent Files used in configuring a software package: @example @group configure* ------------. | [config.h.in] -. v .-> [config.h] -. +--> config.status* -+ +--> make* Makefile.in ---' `-> Makefile ---' @end group @end example @menu * Writing configure.in:: What to put in an Autoconf input file. * Invoking autoconf:: How to create configuration scripts. * Invoking autoheader:: How to create configuration header files. * Invoking autoscan:: Semi-automatic @file{configure.in} writing. * Invoking ifnames:: Listing the conditionals in source code. * Invoking autoreconf:: Remaking multiple @code{configure} scripts. * Invoking autoupdate:: Replacing old macro names in @code{configure.in}. * Invoking shindent:: Making @code{configure} scripts more readable. @end menu @node Writing configure.in, Invoking autoconf, , Making configure Scripts @section Writing @file{configure.in} To produce a @code{configure} script for a software package, create a file called @file{configure.in} that contains invocations of the Autoconf macros that test the system features your package needs or can use. Autoconf macros already exist to check for many features; see @ref{Specific Tests}, for their descriptions. For most other features, you can use Autoconf template macros to produce custom checks; see @ref{General Purpose Macros}, for information about them. For especially tricky or specialized features, @file{configure.in} might need to contain some hand-crafted shell commands. @xref{Writing Macros}, for guidelines on writing tests from scratch. Other than that, the order in which @file{configure.in} calls the Autoconf macros is generally not important, with a few exceptions. Every @file{configure.in} must contain a call to @code{AC_INIT} before the checks, and a call to @code{AC_OUTPUT} at the end (@pxref{Setup}). Additionally, some macros rely on other macros having been called first, because they check previously set values of some variables to decide what to do. These macros are noted in the individual descriptions (@pxref{Specific Tests}), and they also warn you if they are called out of order. To encourage consistency, here is a suggested order for calling the Autoconf macros. Note that there must not be any space between a macro name and the open parentheses. @display @group macros that control Autoconf operation @code{AC_INIT(@var{file})} checks for alternative programs checks for UNIX variants that set C preprocessor variables checks for header files checks for typedefs checks for library functions checks for structures checks for compiler characteristics checks for system services other checks for UNIX variants @code{AC_OUTPUT(@r{[}@var{file@dots{}}@r{]})} @end group @end display You can include comments in @file{configure.in} files by starting them with the @code{m4} predefined macro @code{dnl}, which discards text up through the next newline. These comments do not appear in the generated @code{configure} scripts. For example, it is helpful to begin @file{configure.in} files with a line like this: @example dnl Process this file with autoconf to produce a configure script. @end example @xref{Sample configure.in}, for an example of a real @file{configure.in} script. @node Invoking autoconf, Invoking autoheader, Writing configure.in, Making configure Scripts @section Invoking @code{autoconf} To create @code{configure} from @file{configure.in}, run the @code{autoconf} program with no arguments. @code{autoconf} processes @file{configure.in} with the @code{m4} macro processor, using the Autoconf macros. If you give @code{autoconf} an argument, it reads that file instead of @file{configure.in} and writes the configuration script to the standard output instead of to @file{configure}. If you give @code{autoconf} the argument @samp{-}, it reads the standard input instead of @file{configure.in} and writes the configuration script on the standard output. The Autoconf macros are defined in two or more files. Two of the files are distributed with Autoconf: @code{autoconf} first reads @file{acgeneral.m4} (@pxref{General Purpose Macros}), then @file{acspecific.m4} (@pxref{Specific Tests}). After reading them, @code{autoconf} looks for an optional file called @file{aclocal.m4}, first in the directory that contains other installed Autoconf macro files, and then in the current directory. If both files exist, it uses both of them. Those files can contain your site's own locally written Autoconf macro definitions (@pxref{Writing Macros}, for more information). If a macro is defined in more than one of the files that @code{autoconf} reads, the last definition it reads overrides the earlier ones. You can override the directory where @code{autoconf} looks for the installed macro files by setting the @code{AC_MACRODIR} environment variable to a different directory. You can also give @code{autoconf} the @samp{--macrodir} option, which overrides @code{AC_MACRODIR}. @code{autoconf} also accepts the options @code{--version}, which prints the Autoconf version number and exits, and @code{--help}, which prints a summary of the command-line options and exits. @node Invoking autoheader, Invoking autoscan, Invoking autoconf, Making configure Scripts @section Invoking @code{autoheader} You can use the @code{autoheader} program to create a template file of C @samp{#define} statements for @code{configure} to use. By default, the file that @code{autoheader} creates is called @file{config.h.in}; if @file{configure.in} invokes @code{AC_CONFIG_HEADER(@var{file})}, @code{autoheader} creates @file{@var{file}.in}. @code{autoheader} scans @file{configure.in} and figures out which C preprocessor symbols it might define. It copies comments and @code{#define} and @code{#undef} statements from a file called @file{acconfig.h}, which comes with and is installed with Autoconf. It also uses a file called @file{acconfig.h} in the current directory, if present; you must create that file to contain entries for any additional symbols that you @code{AC_DEFINE}. For symbols defined by @code{AC_CHECK_HEADERS}, @code{AC_CHECK_FUNCS}, @code{AC_CHECK_SIZEOF}, or @code{AC_CHECK_LIB}, @code{autoheader} generates comments and @code{#undef} statements itself rather than copying them from a file, since the possible symbols are effectively limitless. The file that @code{autoheader} creates usually contains only @code{#define} and @code{#undef} statements and their accompanying comments. However, if a file called @file{@var{file}.top} (typically @file{config.h.top}) exists in the current directory, @code{autoheader} copies that file to the beginning of its output. Similarly, if @file{@var{file}.bot} exists, it copies that file to the end of its output. If you give @code{autoheader} an argument, it uses that file instead of @file{configure.in} and writes the header file to the standard output instead of to @file{config.h.in}. If you give @code{autoheader} an argument of @samp{-}, it reads the standard input instead of @file{configure.in} and writes the header file to the standard output. You can override the directory where @code{autoheader} looks for the installed macro and @file{acconfig.h} files by setting the @code{AC_MACRODIR} environment variable to a different directory. You can also give @code{autoheader} the @samp{--macrodir} option, which overrides @code{AC_MACRODIR}. @code{autoheader} also accepts the options @code{--version}, which prints the Autoconf version number and exits, and @code{--help}, which prints a summary of the command-line options and exits. @node Invoking autoscan, Invoking ifnames, Invoking autoheader, Making configure Scripts @section Invoking autoscan The @code{autoscan} program can help you create a @file{configure.in} file for a software package. @code{autoscan} examines source files in the directory tree rooted at a directory given as a command line argument, or the current directory if none is given. It searches the source files for common portability problems and creates a file @file{configure.scan} which is a preliminary @file{configure.in} for that package. You should manually examine @file{configure.scan} before renaming it to @file{configure.in}; it will probably need some adjustments. If you want the package to use a configuration header file, you will have to add a call to @code{AC_CONFIG_HEADER}. You might have to change or add some @code{#if} directives in order to make the package work with Autoconf (@pxref{Invoking ifnames}, for information about a program that might help with that job). @code{autoscan} uses several data files, which are installed with the distributed Autoconf macro files, to determine which macros to output when it finds particular symbols in a package's source files. These files all have the same format. Each line consists of a symbol, whitespace, and the Autoconf macro to output if that symbol is encountered. Lines starting with @samp{#} are comments. @code{autoscan} is only installed if you already have Perl installed. @code{autoscan} accepts the following options: @table @code @item --help Print a summary of the command line options and exit. @item --macrodir=@var{dir} Look for the data files in directory @var{dir} instead of the default installation directory. @item --verbose Print the names of the files it examines and the potentially interesting symbols it finds in them. This output can be voluminous. @item --version Print the version number of @code{autoscan} and exit. @end table @node Invoking ifnames, Invoking autoreconf, Invoking autoscan, Making configure Scripts @section Invoking ifnames @code{ifnames} can help when writing a @file{configure.in} for a software package. It prints the identifiers used in C preprocessor conditionals. If a package has already been set up to have some portability, this program can help you figure out what its @code{configure} needs to check for. It may fill in some gaps in a @file{configure.in} generated by @code{autoscan} (@pxref{Invoking autoscan}). @code{ifnames} scans all of the C source files named on the command line (or the standard input, if none are given) and writes to the standard output a sorted list of all the identifiers that appear in those files in @code{#if}, @code{#elif}, or @code{#ifdef} directives. It prints each identifier on a line, followed by a space-separated list of the files in which that identifier occurs. @noindent @code{ifnames} accepts the following options: @table @code @item --help Print a summary of the command line options and exit. @item --macrodir=@var{dir} Look for the Autoconf macro files in directory @var{dir} instead of the default installation directory. Only used to get the version number. @item --version Print the version number of @code{ifnames} and exit. @end table @node Invoking autoreconf, Invoking autoupdate, Invoking ifnames, Making configure Scripts @section Invoking autoreconf If you have a lot of Autoconf-generated @code{configure} scripts and you get a new version of Autoconf, the @code{autoreconf} program can be handy. It runs @code{autoconf} (and @code{autoheader}, where appropriate) repeatedly to remake all of the Autoconf @code{configure} scripts in a directory tree. @noindent @code{autoreconf} accepts the following options: @table @code @item --help Print a summary of the command line options and exit. @item --macrodir=@var{dir} Look for the Autoconf macro files in directory @var{dir} instead of the default installation directory. @item --verbose Print the name of each directory where @code{autoreconf} runs @code{autoconf} (and @code{autoheader}, if that directory's @file{configure.in} calls @code{AC_CONFIG_HEADER}). @item --version Print the version number of @code{autoreconf} and exit. @end table @node Invoking autoupdate, Invoking shindent, Invoking autoreconf, Making configure Scripts @section Invoking autoupdate The @code{autoupdate} program updates a @file{configure.in} file that calls Autoconf macros by their old names to use the current macro names. In version 2 of Autoconf, most of the macros were renamed to use a more uniform and descriptive naming scheme. @xref{Macro Naming}, for a description of the new scheme. Although the old names still work (@pxref{Old Macro Names}, for a list of the old macro names and the corresponding new names), you can make your @file{configure.in} files more readable and make it easier to use the current Autoconf documentation if you update them to use the new macro names. If given no arguments, @code{autoupdate} updates @file{configure.in}, backing up the original version in the file @file{configure.in~}. If you give @code{autoupdate} an argument, it reads that file instead of @file{configure.in} and writes the updated file to the standard output. @noindent @code{autoupdate} accepts the following options: @table @code @item --help @itemx -h Print a summary of the command line options and exit. @item --macrodir=@var{dir} @itemx -m @var{dir} Look for the Autoconf macro files in directory @var{dir} instead of the default installation directory. @item --version @itemx -v Print the version number of @code{autoupdate} and exit. @end table @node Invoking shindent, , Invoking autoupdate, Making configure Scripts @section Invoking shindent Autoconf-generated @code{configure} scripts can be somewhat hard to read, because they @emph{look} machine-generated---mainly because they do not use whitespace rationally. Unfortunately, it is impossible to do proper indentation using a macro processor like @code{m4}. However, if you have GNU @code{bash} installed, you can use the @code{shindent} program, which uses @code{bash} to give a Bourne shell script readable indentation. @code{shindent} indents each script named on the command line, backing up the original version using the original file name with @samp{~} appended. @code{shindent} places some restrictions on its input, due to the way it uses @code{bash} to do the indentation: @itemize @bullet @item It removes comments and blank lines between cases case statements. @item Doing odd things in case statements might cause odd problems. @item The script must not define any shell functions. @item If any string literals or here-documents contain lines that start with four spaces, those spaces will be removed. @item The script must not be @code{shindent} itself. @end itemize @noindent @code{shindent} accepts the following options: @table @code @item --help Print a summary of the command line options and exit. @item --macrodir=@var{dir} Look for the Autoconf macro files in directory @var{dir} instead of the default installation directory. Only used to get the version number. @item --version Print the version number of @code{shindent} and exit. @end table @node Specific Tests, General Purpose Macros, Making configure Scripts, Top @chapter Specific Tests These macros test for particular operating system features that packages might need or want to use. If you need to test for a feature that none of these macros check for, you can probably do it by calling one of the general purpose test macros with appropriate arguments (@pxref{General Purpose Macros}). All of these macros that set @code{make} variables call @code{AC_SUBST} on those variables (@pxref{Setting Variables}, for details about @code{AC_SUBST}). The phrase ``define @var{name}'' is used below as a shorthand to mean either add @samp{-D@var{name}=1} to the @code{make} variable @code{DEFS}, or put @samp{#define @var{name} 1} in the configuration header file, depending on whether @code{AC_CONFIG_HEADER} has been called. @xref{Setting Variables}, for more information. Within each section below, the macros are listed in alphabetical order. The macros are generally named for the @code{make} variables or C preprocessor macros that they define; those names are based largely on what existing GNU programs use. These macros are defined in the file @file{acspecific.m4}. @menu * Alternative Programs:: Selecting between alternative programs. * Header Files:: Header files that might be missing. * Typedefs:: @code{typedef}s that might be missing. * Library Functions:: C library functions that might be missing. * Structures:: Structures or members that might be missing. * Compiler Characteristics:: C compiler or machine architecture features. * System Services:: Operating system services. * UNIX Variants:: Special cases for specific UNIX variants. @end menu @node Alternative Programs, Header Files, , Specific Tests @section Alternative Programs The following macros check for the presence or behavior of particular programs: @defmac AC_PROG_GCC_TRADITIONAL @maindex PROG_GCC_TRADITIONAL Add @samp{-traditional} to @code{make} variable @code{CC} if using the GNU C compiler and @code{ioctl} does not work properly without @samp{-traditional}. This macro calls @code{AC_PROG_CC} and @code{AC_PROG_CPP} if they haven't been called already. @end defmac @defmac AC_PROG_LN_S @maindex PROG_LN_S If @samp{ln -s} works on the current filesystem (the operating system and filesystem support symbolic links), set shell and @code{make} variable @code{LN_S} to @samp{ln -s}, otherwise set it to @samp{ln}. @end defmac @defmac AC_PROG_CC_C_O @maindex PROG_CC_C_O @vindex NO_MINUS_C_MINUS_O If the C compiler does not accept the @samp{-c} and @samp{-o} options simultaneously, define @code{NO_MINUS_C_MINUS_O}. @end defmac @defmac AC_PROG_AWK @maindex PROG_AWK Check for @code{mawk}, @code{gawk}, @code{nawk}, and @code{awk}, in that order, and set @code{make} variable @code{AWK} to the first one that it finds. @end defmac @defmac AC_PROG_CC @maindex PROG_CC If @code{gcc} is found, set @code{make} variable @code{CC} to @samp{gcc}, and set shell variable @code{GCC} to @samp{yes}. Otherwise set @code{GCC} to be empty. @end defmac @defmac AC_PROG_CPP @maindex PROG_CPP Set shell and @code{make} variable @code{CPP} to a command that runs the C preprocessor. If @samp{$CC -E} doesn't work, it uses @file{/lib/cpp}. It is only portable to run @code{CPP} on files with a @file{.c} extension. If the current language is C (@pxref{Language Choice}), many of the specific test macros use the value of @code{CPP} indirectly by calling @code{AC_TRY_CPP}, @code{AC_CHECK_HEADER}, @code{AC_EGREP_HEADER}, or @code{AC_EGREP_CPP}. Those macros call this macro first if it hasn't been called already. It calls @code{AC_PROG_CC} if it hasn't been called already. @end defmac @defmac AC_PROG_CXX @maindex PROG_CXX Determine a C++ compiler to use. Check if the environment variable @var{CXX} or @var{CCC} (in that order) is set; if so, set @code{make} variable @code{CXX} to its value. Otherwise search for a C++ compiler under likely names (@code{c++}, @code{g++}, @code{gcc}, and @code{CC}). If none of those checks succeed, as a last resort set @code{CXX} to @code{gcc}. Also set shell variable @code{GXX} to @samp{yes} if it found the GNU C++ compiler, empty otherwise. @end defmac @defmac AC_PROG_CXXCPP @maindex PROG_CXXCPP Set shell and @code{make} variable @code{CXXCPP} to a command that runs the C++ preprocessor. If @samp{$CXX -E} doesn't work, it uses @file{/lib/cpp}. It is only portable to run @code{CXXCPP} on files with a @file{.c}, @file{.C}, or @file{.cc} extension. If the current language is C++ (@pxref{Language Choice}), many of the specific test macros use the value of @code{CXXCPP} indirectly by calling @code{AC_TRY_CPP}, @code{AC_CHECK_HEADER}, @code{AC_EGREP_HEADER}, or @code{AC_EGREP_CPP}. Those macros call this macro first if it hasn't been called already. This macro calls @code{AC_PROG_CXX} if it hasn't been called already. @end defmac @defmac AC_PROG_INSTALL @maindex PROG_INSTALL Set @code{make} variable @code{INSTALL} to @samp{install -c} if @code{install} is found and is compatible with the BSD and GNU versions. Otherwise, set @code{INSTALL} to @samp{@var{dir}/install.sh -c}, where it checks the directories specified to @code{AC_CONFIG_AUX_DIR} (or its default directories) to determine @var{dir} (@pxref{Setup}). This macro screens out the false matches @file{/etc/install}, @file{/usr/sbin/install}, and other instances of @code{install} known not to work. It also sets the variable @code{INSTALL_PROGRAM} to @samp{$@{INSTALL@}} and @code{INSTALL_DATA} to @samp{$@{INSTALL@} -m 644}. If you need to use your own installation program because it has features not found in standard @code{install} programs, there is no reason to use @code{AC_PROG_INSTALL}; just put the pathname of your program into your @file{Makefile.in} files. @end defmac @defmac AC_PROG_LEX @maindex PROG_LEX If @code{flex} is found, set @code{make} variable @code{LEX} to @samp{flex} and @code{LEXLIB} to @samp{-lfl}, if that library is in a standard place. Otherwise set @code{LEX} to @samp{lex} and @code{LEXLIB} to @samp{-ll}. @end defmac @defmac AC_PROG_RANLIB @maindex PROG_RANLIB Set @code{make} variable @code{RANLIB} to @samp{ranlib} if @code{ranlib} is found, otherwise to @samp{:} (do nothing). @end defmac @defmac AC_PROG_YACC @maindex PROG_YACC If @code{bison} is found, set @code{make} variable @code{YACC} to @samp{bison -y}. Otherwise, if @code{byacc} is found, set @code{YACC} to @samp{byacc}. Otherwise set @code{YACC} to @samp{yacc}. @end defmac @defmac AC_PROG_RSH @maindex PROG_RSH @vindex RSH @vindex NO_REMOTE @vindex HAVE_NETDB_H If a remote shell is available, set @code{make} variable @code{RSH} to its pathname. Otherwise, if @file{netdb.h} exists (implying the @code{rexec} function), define @code{HAVE_NETDB_H}. If either is true, also put @samp{rtapelib.o} in @code{make} variable @code{RTAPELIB}. Otherwise, define @code{NO_REMOTE}. @end defmac @defmac AC_PROG_MAKE_SET @maindex PROG_MAKE_SET If @code{make} predefines the variable @code{MAKE}, define @code{make} variable @code{SET_MAKE} to be empty. Otherwise, define @code{SET_MAKE} to contain @samp{MAKE=make}. Calls @code{AC_SUBST} for @code{SET_MAKE}. In recent versions of @code{make}, the variable @code{MAKE} contains the name of the @code{make} program plus options it was given. It is used when running @code{make} recursively in subdirectories. But some old versions of @code{make} don't set the @code{MAKE} variable. This macro allows use of @code{MAKE} on all systems. If you use this macro, simply place a line like this in your @file{Makefile.in} file(s): @example @@SET_MAKE@@ @end example @end defmac @defmac AC_DECL_YYTEXT @maindex DECL_YYTEXT @vindex YYTEXT_POINTER Define @code{YYTEXT_POINTER} if @code{yytext} is a @samp{char *} instead of a @samp{char []}. This depends on whether @code{lex} or @code{flex} is being used. This macro calls @code{AC_PROG_CPP} (or @code{AC_PROG_CXXCPP} if C++ is the current language, @pxref{Language Choice}) and @code{AC_PROG_LEX} if they haven't been called already. This macro replaces @code{AC_DECLARE_YYTEXT}, which didn't work. @end defmac @node Header Files, Typedefs, Alternative Programs, Specific Tests @section Header Files The following macros check for the presence of certain C header files: @defmac AC_DIR_HEADER @maindex DIR_HEADER @vindex DIRENT @vindex SYSDIR @vindex SYSNDIR @vindex NDIR @vindex VOID_CLOSEDIR Like @code{AC_HEADER_DIRENT}, but defines a different set of C preprocessor macros to indicate which header file is found. This macro and the names it defines are considered obsolete. The names it defines are: @table @file @item dirent.h @code{DIRENT} @item sys/ndir.h @code{SYSNDIR} @item sys/dir.h @code{SYSDIR} @item ndir.h @code{NDIR} @end table Also, if the directory library header file contains a declaration of the @code{closedir} function with a @code{void} return type, define @code{VOID_CLOSEDIR}. @end defmac @defmac AC_HEADER_DIRENT @maindex HEADER_DIRENT @vindex HAVE_DIRENT_H @vindex HAVE_NDIR_H @vindex HAVE_SYS_DIR_H @vindex HAVE_SYS_NDIR_H @vindex CLOSEDIR_VOID Check for the the following header files, and for the first one that is found, define the listed C preprocessor macro: @table @file @item dirent.h @code{HAVE_DIRENT_H} @item sys/ndir.h @code{HAVE_SYS_NDIR_H} @item sys/dir.h @code{HAVE_SYS_DIR_H} @item ndir.h @code{HAVE_NDIR_H} @end table Also, if the directory library header file contains a declaration of the @code{closedir} function with a @code{void} return type, define @code{CLOSEDIR_VOID}. The directory library declarations in the source code should look something like the following, which assumes that you have also called @samp{AC_CHECK_HEADERS(unistd.h)}: @example @group #ifdef HAVE_UNISTD_H #include #include #endif #ifdef HAVE_DIRENT_H # include # define NAMLEN(dirent) (strlen((dirent)->d_name)) #else /* !HAVE_DIRENT_H */ # define dirent direct # define NAMLEN(dirent) ((dirent)->d_namlen) # ifdef HAVE_SYS_NDIR_H # include # endif /* HAVE_SYS_NDIR_H */ # ifdef HAVE_SYS_DIR_H # include # endif /* HAVE_SYS_DIR_H */ # ifdef HAVE_NDIR_H # include # endif /* HAVE_NDIR_H */ #endif /* !HAVE_DIRENT_H */ @end group @end example Using the above declarations, the program would declare variables to be type @code{struct dirent}, not @code{struct direct}, and would access the length of a directory entry name by passing a pointer to a @code{struct dirent} to the @code{NAMLEN} macro. @end defmac @defmac AC_HEADER_MAJOR @maindex HEADER_MAJOR @vindex MAJOR_IN_MKDEV @vindex MAJOR_IN_SYSMACROS If @file{sys/types.h} does not define @code{major}, @code{minor}, and @code{makedev}, but @file{sys/mkdev.h} does, define @code{MAJOR_IN_MKDEV}; otherwise, if @file{sys/sysmacros.h} does, define @code{MAJOR_IN_SYSMACROS}. @end defmac @defmac AC_MEMORY_H @maindex MEMORY_H @vindex NEED_MEMORY_H Define @code{NEED_MEMORY_H} if @code{memcpy}, @code{memcmp}, etc. are not declared in @file{string.h} and @file{memory.h} exists. This macro is obsolete; instead, use @code{AC_CHECK_HEADERS(memory.h)}. See the example for @code{AC_HEADER_STDC}. @end defmac @defmac AC_HEADER_STDC @maindex HEADER_STDC @vindex STDC_HEADERS Define @code{STDC_HEADERS} if the system has ANSI C header files. Specifically, this macro checks for @file{stdlib.h}, @file{stdarg.h}, @file{string.h}, and @file{float.h}; if the system has those, it probably has the rest of the ANSI C header files. This macro also checks whether @file{string.h} declares @code{memchr} (and thus presumably the other @code{mem} functions), whether @file{stdlib.h} declare @code{free} (and thus presumably @code{malloc} and other related functions), and whether the @file{ctype.h} macros work on characters with the high bit set, as ANSI C requires. Use @code{STDC_HEADERS} instead of @code{__STDC__} to determine whether the system has ANSI-compliant header files (and probably C library functions) because many systems that have GCC do not have ANSI C header files. To check whether to use the System V/ANSI C string functions and header file, you can put the following in @file{configure.in}: @example AC_HEADER_STDC AC_CHECK_HEADERS(string.h memory.h) @end example @noindent Then, in the code, use a test like this: @example @group #if STDC_HEADERS || HAVE_STRING_H #include /* An ANSI string.h and pre-ANSI memory.h might conflict. */ #if !STDC_HEADERS && HAVE_MEMORY_H #include #endif /* not STDC_HEADERS and HAVE_MEMORY_H */ #else /* not STDC_HEADERS and not HAVE_STRING_H */ #include /* memory.h and strings.h conflict on some systems. */ #ifndef strchr #define strchr index #endif #ifndef strrchr #define strrchr rindex #endif #ifndef memcpy #define memcpy(d, s, n) bcopy ((s), (d), (n)) #endif #ifndef memcmp #define memcmp(s1, s2, n) bcmp ((s1), (s2), (n)) #endif #endif /* not STDC_HEADERS and not HAVE_STRING_H */ @end group @end example @noindent This example asssumes that your code uses the ANSI C/System V style functions. If you use the BSD style functions, replace the macro definitions with ones that go in the other direction. (Or, better, modernize your code.) This macro calls @code{AC_PROG_CPP} or @code{AC_PROG_CXXCPP} (depending on which language is current, @pxref{Language Choice}), if it hasn't been called already. @end defmac @defmac AC_UNISTD_H @maindex UNISTD_H @vindex HAVE_UNISTD_H Define @code{HAVE_UNISTD_H} if the system has @file{unistd.h}. This macro is obsolete; instead, use @samp{AC_CHECK_HEADERS(unistd.h)}. The way to check if the system supports POSIX.1 is: @example @group #if HAVE_UNISTD_H #include #include #endif #ifdef _POSIX_VERSION /* Code for POSIX.1 systems. */ #endif @end group @end example @vindex _POSIX_VERSION @code{_POSIX_VERSION} is defined when @file{unistd.h} is included on POSIX.1 systems. If there is no @file{unistd.h}, it is definitely not a POSIX.1 system. However, some non-POSIX.1 systems do have @file{unistd.h}. @end defmac @defmac AC_USG @maindex USG @vindex USG Define @code{USG} if the system does not have @file{strings.h}, @code{rindex}, @code{bzero}, etc. This implies that it has @file{string.h}, @code{strrchr}, @code{memset}, etc. The symbol @code{USG} is obsolete. Instead of this macro, use @code{AC_CHECK_HEADERS(string.h)} and use @code{HAVE_STRING_H} in your code. See the example for @code{AC_HEADER_STDC}. @end defmac @defmac AC_DECL_SYS_SIGLIST @maindex DECL_SYS_SIGLIST @vindex SYS_SIGLIST_DECLARED Define @code{SYS_SIGLIST_DECLARED} if the variable @code{sys_siglist} is declared in a system header file, either @file{signal.h} or @file{unistd.h}. @end defmac @node Typedefs, Library Functions, Header Files, Specific Tests @section Typedefs The following macros check for predefined C types: @defmac AC_TYPE_GETGROUPS @maindex TYPE_GETGROUPS @vindex GETGROUPS_T Define @code{GETGROUPS_T} to be whichever of @code{gid_t} or @code{int} is the base type of the array argument to @code{getgroups}. @end defmac @defmac AC_TYPE_MODE_T @maindex TYPE_MODE_T @vindex mode_t If @code{mode_t} is not defined in @file{sys/types.h}, define @code{mode_t} to be @code{int}. @end defmac @defmac AC_TYPE_OFF_T @maindex TYPE_OFF_T @vindex off_t If @code{off_t} is not defined in @file{sys/types.h}, define @code{off_t} to be @code{long}. @end defmac @defmac AC_TYPE_PID_T @maindex TYPE_PID_T @vindex pid_t If @code{pid_t} is not defined in @file{sys/types.h}, define @code{pid_t} to be @code{int}. @end defmac @defmac AC_TYPE_SIGNAL @maindex TYPE_SIGNAL @vindex RETSIGTYPE If @file{signal.h} declares @code{signal} as returning a pointer to a function returning @code{void}, define @code{RETSIGTYPE} to be @code{void}; otherwise, define it to be @code{int}. Define signal handlers as returning type @code{RETSIGTYPE}: @example @group RETSIGTYPE hup_handler () @{ @dots{} @} @end group @end example @end defmac @defmac AC_TYPE_SIZE_T @maindex TYPE_SIZE_T @vindex size_t If @code{size_t} is not defined in @file{sys/types.h}, define @code{size_t} to be @code{unsigned}. @end defmac @defmac AC_TYPE_UID_T @maindex TYPE_UID_T @vindex uid_t @vindex gid_t If @code{uid_t} is not defined in @file{sys/types.h}, define @code{uid_t} to be @code{int} and @code{gid_t} to be @code{int}. @end defmac @node Library Functions, Structures, Typedefs, Specific Tests @section Library Functions The following macros check for particular C library functions: @defmac AC_FUNC_ALLOCA @maindex FUNC_ALLOCA @vindex C_ALLOCA @vindex HAVE_ALLOCA_H Check how to get @code{alloca}. Tries to get a builtin version by checking for @file{alloca.h} or the predefined C preprocessor macros @code{__GNUC__} and @code{_AIX}. If that fails, it looks for a function in the standard C library. If any of those methods succeed, it defines @code{HAVE_ALLOCA}. Otherwise, it sets the @code{make} variable @code{ALLOCA} to @samp{alloca.o} and defines @code{C_ALLOCA} (so programs can periodically call @samp{alloca(0)} to garbage collect). This variable is separate from @code{LIBOBJS} so multiple programs can share the value of @code{ALLOCA} without needing to create an actual library, in case only some of them use the code in @code{LIBOBJS}. If this macro finds @file{alloca.h}, it defines @code{HAVE_ALLOCA_H}. This macro does not try to get @code{alloca} from the SVR3 @file{libPW} or the SVR4 @file{libucb} because those libraries contain some incompatible functions that cause trouble. Some versions do not even contain @code{alloca} or contain a buggy version. If you still want to use their @code{alloca}, use @code{ar} to extract @file{alloca.o} from them instead of compiling @file{alloca.c}. Source files that use @code{alloca} should start with a piece of code like the following, to declare it properly. Note that in some versions of AIX, the declaration of @code{alloca} must precede everything else except for comments and preprocessor directives. The @code{#pragma} directive is indented so that pre-ANSI C compilers will ignore it, rather than choke on it. @example @group /* AIX requires this to be the first thing in the file. */ #ifdef __GNUC__ #define alloca __builtin_alloca #else /* not __GNUC__ */ #if HAVE_ALLOCA_H #include #else /* not HAVE_ALLOCA_H */ #ifdef _AIX #pragma alloca #else /* not _AIX */ #ifndef alloca /* predefined by HP cc +Olibcalls */ char *alloca (); #endif /* not defined(alloca) */ #endif /* not _AIX */ #endif /* not HAVE_ALLOCA_H */ #endif /* not __GNUC__ */ @end group @end example @end defmac @defmac AC_FUNC_GETLOADAVG @maindex FUNC_GETLOADAVG @vindex SVR4 @vindex DGUX @vindex UMAX @vindex UMAX4_3 @vindex NLIST_STRUCT @vindex NLIST_NAME_UNION @vindex GETLODAVG_PRIVILEGED @vindex NEED_SETGID Check how to get the system load averages. If the system has the @code{getloadavg} function, this macro defines @code{HAVE_GETLOADAVG}, and adds to @code{LIBS} any libraries needed to get that function. Otherwise, it adds @samp{getloadavg.o} to the @code{make} variable @code{LIBOBJS}, and possibly defines several other C preprocessor macros and @code{make} variables: @enumerate @item It defines @code{SVR4}, @code{DGUX}, @code{UMAX}, or @code{UMAX4_3} if on those systems. @item If it finds @file{nlist.h}, it defines @code{NLIST_STRUCT}. @item If @samp{struct nlist} has an @samp{n_un} member, it defines @code{NLIST_NAME_UNION}. @item If compiling @file{getloadavg.c} defines @code{LDAV_PRIVILEGED}, programs need to be installed specially on this system for @code{getloadavg} to work, and this macro defines @code{GETLOADAVG_PRIVILEGED}. @item This macro always defines @code{NEED_SETGID}, for @code{make}. The value is @samp{true} if special installation is required, @samp{false} if not. If @code{NEED_SETGID} is @samp{true}, it sets @code{KMEM_GROUP} to the name of the group that should own the installed program. @end enumerate @end defmac @defmac AC_FUNC_MMAP @maindex FUNC_MMAP @vindex HAVE_MMAP If the @code{mmap} function exists and works correctly, define @code{HAVE_MMAP}. @end defmac @defmac AC_FUNC_SETVBUF_REVERSED @maindex FUNC_SETVBUF_REVERSED @vindex SETVBUF_REVERSED If @code{setvbuf} takes the buffering type as its second argument and the buffer pointer as the third, instead of the other way around, define @code{SETVBUF_REVERSED}. This is the case on System V before release 3. @end defmac @defmac AC_FUNC_STRCOLL @maindex FUNC_STRCOLL @vindex HAVE_STRCOLL If the @code{strcoll} function exists and works correctly, define @code{HAVE_STRCOLL}. This does a bit more than @samp{AC_CHECK_FUNCS(strcoll)}, because some systems have incorrect definitions of @code{strcoll}, which should not be used. @end defmac @defmac AC_FUNC_UTIME_NULL @maindex FUNC_UTIME_NULL @vindex HAVE_UTIME_NULL If @samp{utime(@var{file}, NULL)} sets @var{file}'s timestamp to the present, define @code{HAVE_UTIME_NULL}. @end defmac @defmac AC_FUNC_VFORK @maindex FUNC_VFORK @vindex HAVE_VFORK_H @vindex vfork If @file{vfork.h} is found, define @code{HAVE_VFORK_H}. If a working @code{vfork} is not found, define @code{vfork} to be @code{fork}. This macro checks for several known errors in implementations of @code{vfork} and considers the system to not have a working @code{vfork} if it detects any of them. @end defmac @defmac AC_FUNC_VPRINTF @maindex FUNC_VPRINTF @vindex HAVE_VPRINTF @vindex HAVE_DOPRNT If @code{vprintf} is found, define @code{HAVE_VPRINTF}. Otherwise, if @code{_doprnt} is found, define @code{HAVE_DOPRNT}. (If @code{vprintf} is available, you may assume that @code{vfprintf} and @code{vsprintf} are also available.) @end defmac @defmac AC_FUNC_WAIT3 @maindex FUNC_WAIT3 @vindex HAVE_WAIT3 If @code{wait3} is found and fills in the contents of its third argument (a @samp{struct rusage *}), which HP-UX does not do, define @code{HAVE_WAIT3}. @end defmac @node Structures, Compiler Characteristics, Library Functions, Specific Tests @section Structures The following macros check for certain structures or structure members: @defmac AC_HEADER_STAT @maindex HEADER_STAT @maindex STAT_MACROS_BROKEN If the macros @code{S_ISDIR}, @code{S_ISREG} et al. defined in @file{sys/stat.h} do not work properly (returning false positives), define @code{STAT_MACROS_BROKEN}. This is the case on Tektronix UTekV, Amdahl UTS and Motorola System V/88. @end defmac @defmac AC_STRUCT_ST_BLKSIZE @maindex STRUCT_ST_BLKSIZE @vindex HAVE_ST_BLKSIZE If @code{struct stat} contains an @code{st_blksize} member, define @code{HAVE_ST_BLKSIZE}. @end defmac @defmac AC_STRUCT_ST_BLOCKS @maindex STRUCT_ST_BLOCKS @vindex HAVE_ST_BLOCKS If @code{struct stat} contains an @code{st_blocks} member, define @code{HAVE_ST_BLOCKS}. Otherwise, add @samp{fileblocks.o} to the @code{make} variable @code{LIBOBJS}. @end defmac @defmac AC_STRUCT_ST_RDEV @maindex STRUCT_ST_RDEV @vindex HAVE_ST_RDEV If @code{struct stat} contains an @code{st_rdev} member, define @code{HAVE_ST_RDEV}. @end defmac @defmac AC_HEADER_TIME @maindex HEADER_TIME @vindex TIME_WITH_SYS_TIME If a program may include both @file{time.h} and @file{sys/time.h}, define @code{TIME_WITH_SYS_TIME}. On some older systems, @file{sys/time.h} includes @file{time.h}, but @file{time.h} is not protected against multiple inclusion, so programs should not explicitly include both files. This macro is useful in programs that use, for example, @code{struct timeval} or @code{struct timezone} as well as @code{struct tm}. It is best used in conjunction with @code{HAVE_SYS_TIME_H}. @example #ifdef TIME_WITH_SYS_TIME #include #include #else #ifdef HAVE_SYS_TIME_H #include #else #include #endif #endif @end example @end defmac @defmac AC_STRUCT_TM @maindex STRUCT_TM @vindex TM_IN_SYS_TIME If @file{time.h} does not define @code{struct tm}, define @code{TM_IN_SYS_TIME}, which means that including @file{sys/time.h} defines @code{struct tm}. @end defmac @defmac AC_STRUCT_TIMEZONE @maindex STRUCT_TIMEZONE @vindex HAVE_TM_ZONE @vindex HAVE_TZNAME Figure out how to get the current timezone. If @code{struct tm} has a @code{tm_zone} member, define @code{HAVE_TM_ZONE}. Otherwise, if the external array @code{tzname} is found, define @code{HAVE_TZNAME}. This macro calls @code{AC_STRUCT_TM} if it hasn't been called already. @end defmac @node Compiler Characteristics, System Services, Structures, Specific Tests @section Compiler Characteristics The following macros check for C compiler or machine architecture features: @defmac AC_C_ARG_ARRAY @maindex C_ARG_ARRAY @vindex NO_ARG_ARRAY If the address of an argument to a C function can not be used like the start of an array, define @code{NO_ARG_ARRAY}. This ability allows a sequence of arguments with the same type to be accessed as if they were an array of values. @end defmac @defmac AC_TRY_CROSS @maindex TRY_CROSS If the C compiler being used does not produce executables that can run on the system where @code{configure} is being run, set the shell variable @code{cross_compiling} to @samp{yes}, otherwise @samp{no}. This information can be used by @code{AC_TRY_RUN} to determine whether to take a default action instead of trying to run a test program (@pxref{C Features}). @end defmac @defmac AC_C_CHAR_UNSIGNED @maindex C_CHAR_UNSIGNED @vindex __CHAR_UNSIGNED__ If the C type @code{char} is unsigned, define @code{__CHAR_UNSIGNED__}, unless the C compiler predefines it. @end defmac @defmac AC_C_CONST @maindex C_CONST @vindex const If the C compiler does not fully support the keyword @code{const}, define @code{const} to be empty. Some C compilers that do not define @code{__STDC__} do support @code{const}; some compilers that define @code{__STDC__} do not completely support @code{const}. Programs can simply use @code{const} as if every C compiler supported it; for those that don't, the @file{Makefile} or configuration header file will define it as empty. (If using a configuration header file, the program should include it before any other header files, to prevent inconsistencies in declarations.) @end defmac @defmac AC_C_INLINE @maindex C_INLINE @vindex inline If the C compiler is a version of GCC that supports the keyword @code{__inline} but not @code{inline} (such as some NeXT versions), define @code{inline} to be @code{__inline}. This macro calls @code{AC_PROG_CC} if it hasn't been called already. @end defmac @defmac AC_INT_16_BITS @maindex INT_16_BITS @vindex INT_16_BITS If the C type @code{int} is 16 bits wide, define @code{INT_16_BITS}. This macro is obsolete; it is more general to use @samp{AC_CHECK_SIZEOF(int)} instead (@pxref{C Features}). @end defmac @defmac AC_LONG_64_BITS @maindex LONG_64_BITS @vindex LONG_64_BITS If the C type @code{long int} is 64 bits wide, define @code{LONG_64_BITS}. This macro is obsolete; it is more general to use @samp{AC_CHECK_SIZEOF(long)} instead (@pxref{C Features}). @end defmac @defmac AC_C_LONG_DOUBLE @maindex C_LONG_DOUBLE @vindex HAVE_LONG_DOUBLE If the C compiler supports the @code{long double} type, define @code{HAVE_LONG_DOUBLE}. Some C compilers that do not define @code{__STDC__} do support the @code{long double} type; some compilers that define @code{__STDC__} do not support @code{long double}. @end defmac @defmac AC_C_BIGENDIAN @maindex C_BIGENDIAN @vindex WORDS_BIGENDIAN If words are stored with the most significant byte first (like Motorola and SPARC, but not Intel and VAX, CPUs), define @code{WORDS_BIGENDIAN}. @end defmac @node System Services, UNIX Variants, Compiler Characteristics, Specific Tests @section System Services The following macros check for operating system services: @defmac AC_PATH_X @maindex PATH_X Try to locate the X Window System include files and libraries. Try first by running @code{xmkmf} on a trivial @file{Imakefile} and examining the @file{Makefile} that it produces. If that fails (such as if @code{xmkmf} is not present), look for them in several directories where they often reside. If either method is successful, set the shell variables @code{x_includes} and @code{x_libraries} to their locations, unless they are in directories the compiler searches by default. If both methods fail, or the user gave the command line option @samp{--without-x}, set the shell variable @code{no_x} to @samp{true}; otherwise set it to the empty string. The command line options @samp{--x-includes=@var{dir}} and @samp{--x-libraries=@var{dir}} override the values chosen by this macro. @end defmac @defmac AC_PATH_XTRA @maindex PATH_XTRA An enhanced version of @code{AC_PATH_X}. Put the C compiler flags that X needs into @code{make} variable @code{X_CFLAGS}, and the X linker flags into @code{X_LIBS}. If X is not available, put @samp{-DX_DISPLAY_MISSING} into @code{X_CFLAGS}. Also check for special libraries that some systems need in order to compile X programs. Add any that the system needs to @code{make} variable @code{X_EXTRA_LIBS}. This macro calls @code{AC_PATH_X} and @code{AC_OS_ISC} (@pxref{UNIX Variants}) if they have not already been called. Because of the macro dependencies, if you call this macro, you should let it call @code{AC_PATH_X} rather than doing that yourself. @end defmac @defmac AC_HAVE_POUNDBANG (@var{action-if-supported} @r{[}, @var{action-if-not-supported}@r{]}) @maindex HAVE_POUNDBANG Check whether the system supports starting shell scripts with a line of the form @samp{#!/bin/csh} to select the shell to use. If @samp{#!} works, execute shell commands @var{action-if-supported}; if not, execute @var{action-if-not-supported}. @end defmac @defmac AC_SYS_LONG_FILE_NAMES @maindex SYS_LONG_FILE_NAMES @vindex HAVE_LONG_FILE_NAMES If the system supports file names longer than 14 characters, define @code{HAVE_LONG_FILE_NAMES}. @end defmac @defmac AC_SYS_REMOTE_TAPE @maindex SYS_REMOTE_TAPE @vindex HAVE_SYS_MTIO_H If BSD tape drive ioctls are available, define @code{HAVE_SYS_MTIO_H}, and if sockets are available add @code{rmt} to @code{make} variable @code{PROGS}. @end defmac @defmac AC_SYS_RESTARTABLE_SYSCALLS @maindex SYS_RESTARTABLE_SYSCALLS @vindex HAVE_RESTARTABLE_SYSCALLS If the system automatically restarts a system call that is interrupted by a signal, define @code{HAVE_RESTARTABLE_SYSCALLS}. @end defmac @node UNIX Variants, , System Services, Specific Tests @section UNIX Variants The following macros check for certain operating systems that need special treatment for some programs, due to exceptional oddities in their header files or libraries. These macros are warts; they should be replaced by a more systematic approach, based either on the functions they make available or the environments they provide. @defmac AC_OS_AIX @maindex OS_AIX @vindex _ALL_SOURCE If on AIX, define @code{_ALL_SOURCE}. Allows the use of some BSD functions. Should be called before any macros that run the C compiler. @end defmac @defmac AC_OS_DYNIX @maindex OS_DYNIX If on DYNIX/ptx (Sequent UNIX), add @samp{-lseq} to @code{make} variable @code{LIBS}. Allows use of some BSD system calls and @code{getmntent}. @end defmac @defmac AC_OS_IRIX @maindex OS_IRIX If on IRIX (Silicon Graphics UNIX), add @samp{-lsun} to @code{make} variable @code{LIBS}. Needed to get @code{getmntent}. At sites using Yellow Pages/NIS, it is also needed to get properly working @code{gethostby*}, @code{getpw*}, @code{getgr*}, @code{getnetby*}, and so on. @c (According to Garrett.Wollman@uvm.edu.) @end defmac @defmac AC_OS_ISC @maindex OS_ISC @vindex _POSIX_SOURCE If on a POSIXized ISC UNIX, define @code{_POSIX_SOURCE} and add @samp{-posix} (for the GNU C compiler) or @samp{-Xp} (for other C compilers) to @code{make} variable @code{CC}. This allows the use of POSIX facilities. Must be called after @code{AC_PROG_CC} and before any other macros that run the C compiler. @end defmac @defmac AC_OS_MINIX @maindex OS_MINIX @vindex _MINIX @vindex _POSIX_SOURCE @vindex _POSIX_1_SOURCE If on Minix, define @code{_MINIX} and @code{_POSIX_SOURCE} and define @code{_POSIX_1_SOURCE} to be 2. This allows the use of POSIX facilities. Should be called before any macros that run the C compiler. @end defmac @defmac AC_OS_SCO @maindex OS_SCO If on SCO UNIX, add @samp{-lintl} to @code{make} variable @code{LIBS}. Used to get @code{strftime}. It must be called before checking for @code{strftime}. @end defmac @defmac AC_OS_XENIX @maindex OS_XENIX If on Xenix, add @samp{-lx} to @code{make} variable @code{LIBS}. Also, if @file{sys/ndir.h} is not being used, add @samp{-ldir} to @code{LIBS}. Needed when using the directory reading functions. This macro calls @code{AC_DIR_HEADER} if it has not been called already. @end defmac @node General Purpose Macros, Manual Configuration, Specific Tests, Top @chapter General Purpose Macros These macros provide ways for other macros to control the kind of output that Autoconf produces or to check whether various kinds of features are available. They all take arguments. When calling these macros, there must not be any blank space between the macro name and the open parentheses. Arguments to these macros can be more than one line long if they are enclosed within the @code{m4} quote characters @samp{[} and @samp{]}. Many of these macros handle two cases: what to do if the given condition is met, and what to do if the condition is not met. In some places you you might want to do something if a condition is true but do nothing if it's false, or vice versa. To omit the true case, pass an empty value for the @var{action-if-found} argument to the macro. To omit the false case, omit the @var{action-if-not-found} argument to the macro, including the comma before it. One shell programming construction that you should not use in the action arguments to these macros is @samp{@var{var}=$@{@var{var}:-@var{value}@}}. Old BSD shells, including the Ultrix @code{sh}, don't understand the colon, and complain and die. If you omit the colon, it works fine: @samp{@var{var}=$@{@var{var}-@var{value}@}}. Using the form without the colon has one small disadvantage. Users can not select a default value by giving a variable an empty value, e.g., @samp{CC= configure}. Instead, they must unset the variable, e.g., @samp{unset CC; configure}. Within each section below, the macros are listed in alphabetical order. These macros are defined in the file @file{acgeneral.m4}. @menu * Setup:: Controlling Autoconf operation. * File Existence:: Checking whether particular files exist. * C Features:: Checking for features of the C system. * Command Line:: Checking command line arguments. * Setting Variables:: Setting shell and @code{make} variables. * Printing Messages:: Notifying users of progress or problems. * Language Choice:: Selecting which language to use for testing. * Macro Ordering:: Enforcing ordering constraints. @end menu @node Setup, File Existence, , General Purpose Macros @section Controlling Autoconf Setup The following macros control the kind of output that Autoconf produces. @file{configure.in} should call them before @code{AC_INIT} or @code{AC_INIT_PREPARE}. Remember to put a @code{dnl} comment at the ends of the lines containing their calls, to avoid inserting blank lines at the beginning of @file{configure}. @defmac AC_CONFIG_AUX_DIR(@var{dir}) @maindex CONFIG_AUX_DIR Use the @file{install.sh}, @file{config.sub}, @file{config.guess}, and Cygnus @file{configure} scripts that are in directory @var{dir}. These are auxiliary files used in configuration. @var{dir} can be either absolute or relative to @file{@var{srcdir}}. The default is @file{@var{srcdir}} or @file{@var{srcdir}/..} or @file{@var{srcdir}/../..}, whichever is the first that contains @file{install.sh}. The other files are not checked for, so that using @code{AC_PROG_INSTALL} does not automatically require distributing the other auxiliary files. @end defmac @defmac AC_CONFIG_HEADER (@var{header-to-create} @dots{}) @maindex CONFIG_HEADER @vindex HAVE_CONFIG_H Make @code{AC_OUTPUT} create the file(s) in the whitespace-separated list @var{header-to-create} containing C preprocessor @code{#define} statements and replace @samp{@@DEFS@@} in generated files with @samp{-DHAVE_CONFIG_H} instead of the value of @code{DEFS}. The usual name for @var{header-to-create} is @file{config.h}. If @var{header-to-create} already exists and its contents are identical to what @code{AC_OUTPUT} would put in it, it is left alone. Doing this allows some changes in configuration without needlessly causing object files that depend on the header file to be recompiled. Your distribution should contain a file @file{@var{header-to-create}.in} that looks as you want the final header file to look, including comments, with default values in the @code{#define} statements. A default value can be to @code{#undef} the variable instead of to define it to a value, if your code tests for configuration options using @code{#ifdef} instead of @code{#if}. You can use the program @code{autoheader} to create @file{@var{header-to-create}.in} (@pxref{Invoking autoheader}). @end defmac @defmac AC_CONFIG_SUBDIRS (@var{dir} @dots{}) @maindex CONFIG_SUBDIRS Run @code{configure} in each subdirectory @var{dir} in the given whitespace-separated list. If a given @var{dir} is not found, no error is reported, so a @code{configure} script can configure whichever parts of a large source tree are present. If a given @var{dir} contains @file{configure.in} but no @file{configure}, the Cygnus @code{configure} script found by @code{AC_CONFIG_AUXDIR} is used. The subdirectory @code{configure} scripts are given the same command line options that were given to this @code{configure} script, with minor changes if needed (e.g., to adjust a relative path for the cache file or source directory). This macro also sets the shell and @code{make} variable @code{subdirs} to the list of directories @samp{@var{dir} @dots{}}. @file{Makefile} rules can use this variable to determine which subdirectories to recurse into. @end defmac @defmac AC_INIT (@var{unique-file-in-source-dir}) @maindex INIT Process the command-line arguments and find the source code directory. @var{unique-file-in-source-dir} is some file that is in the package's source directory; @code{configure} checks for this file's existence to make sure that the directory that it is told contains the source code in fact does (@pxref{Invoking configure}, for more information). @end defmac @defmac AC_OUTPUT (@r{[}@var{file}@dots{}@r{] [,}@var{extra-cmds}@r{]}) @maindex OUTPUT Create output files (typically one or more @file{Makefile}s) and @file{config.status}. If @code{AC_CONFIG_HEADER} has been called, also create the header file that was named as its argument. The argument is a whitespace-separated list of files to create; if it is omitted, no files are created. @code{AC_OUTPUT} creates each file @file{@var{file}} in the list by copying @file{@var{file}.in}, substituting the variable values that have been selected by calling @code{AC_SUBST}. It creates the directory that each file is in if it doesn't exist (but not the parents of that directory). A plausible value for the argument to @code{AC_OUTPUT} is @samp{Makefile src/Makefile man/Makefile X/Imakefile}. If you pass @var{extra-cmds}, those commands will be inserted into @file{config.status} to be run after all its other processing. @end defmac @defmac AC_PREFIX_PROGRAM (@var{program}) @maindex PREFIX_PROGRAM If the user did not specify an installation prefix (using the @samp{--prefix} option), guess a value for it by looking for @var{program} in @code{PATH}, the way the shell does. If @var{program} is found, set the prefix to the parent of the directory containing @var{program}; otherwise leave the prefix specified in @file{Makefile.in} unchanged. For example, if @var{program} is @code{gcc} and the @code{PATH} contains @file{/usr/local/gnu/bin/gcc}, set the prefix to @file{/usr/local/gnu}. @end defmac @defmac AC_INIT_PREPARE (@var{unique-file-in-source-dir}) @maindex INIT_PREPARE Find the source code directory and set up shell variables necessary for other Autoconf macros to work. @var{unique-file-in-source-dir} is some file that is in the package's source directory; @code{configure} checks for this file's existence to make sure that the directory that it is told contains the source code in fact does (@pxref{Invoking configure}, for more information). @code{AC_INIT_PREPARE} is the last thing done by @code{AC_INIT}. Use @code{AC_INIT_PREPARE} instead of @code{AC_INIT} if you want to do argument parsing yourself; never use both. @end defmac @defmac AC_PREREQ (@var{version}) @maindex PREREQ Ensure that a recent enough version of Autoconf is being used. If the version of Autoconf being used to create @code{configure} is earlier than @var{version} (e.g., @samp{1.8}), print an error message on the standard error output and do not create @code{configure}. This macro is useful if your @file{configure.in} relies on non-obvious behavior that changed between Autoconf releases. If it merely needs recently added macros, then @code{AC_PREREQ} is less useful, because the @code{autoconf} program already tells the user which macros are not found. The same thing happens if @file{configure.in} is processed by a version of Autoconf older than when @code{AC_PREREQ} was added. @end defmac @defmac AC_REVISION (@var{revision-info}) @maindex REVISION Copy revision stamp @var{revision-info} into the @file{configure} script, with any dollar signs or double-quotes removed. This macro lets you put a revision stamp from @file{configure.in} into @file{configure} without RCS or CVS changing it when you check in @file{configure}. That way, you can determine easily which revision of @file{configure.in} a particular @file{configure} corresponds to. It is a good idea to call this macro before @code{AC_INIT} so that the revision number is near the top of both @file{configure.in} and @file{configure}. To support doing that, the @code{AC_REVISION} output begins with @samp{#!/bin/sh}, like the normal start of a @file{configure} script does. For example, this line in @file{configure.in}: @example AC_REVISION($@asis{Revision: 1.30 }$)dnl @end example @noindent produces this in @file{configure}: @example #!/bin/sh # From configure.in Revision: 1.30 @end example @end defmac @node File Existence, C Features, Setup, General Purpose Macros @section Checking Whether Particular Files Exist These macros check whether particular files exist. @defmac AC_CHECK_LIB (@var{library} @r{[}, @var{action-if-found} @r{[}, @var{action-if-not-found} @r{[}, @var{other-libraries}@r{]]]}) @maindex CHECK_LIB Create a test C program to see whether that program can be linked with the library @var{library}. @var{action-if-found} is a list of shell commands to run if the link succeeds (which means that the library is present); @var{action-if-not-found} is a list of shell commands to run if the link fails. If @var{action-if-found} and @var{action-if-not-found} are not specified, the default action is to add @samp{-lfoo} to @code{LIBS} and define @samp{HAVE_LIBfoo} for library @samp{foo}. @var{library} can be written as any of @samp{foo}, @samp{-lfoo}, or @samp{libfoo.a}. In all of those cases, the compiler is passed @samp{-lfoo}. If linking with @var{library} results in unresolved symbols, which would be resolved by linking with additional libraries, give those libraries as the @var{other-libraries} argument, separated by spaces: @samp{-lX11 -lXt}. Otherwise this macro will fail to detect that @var{library} is present, because linking the test program will always fail with unresolved symbols. @end defmac @defmac AC_PREFIX (@var{program}) @maindex PREFIX This macro is like @code{AC_PREFIX_PROGRAM}, except that it prevents finding the site-wide defaults file correctly, so it is obsolete. @end defmac @defmac AC_CHECK_PROG (@var{variable}, @var{prog-to-check-for}, @var{value-if-found} @r{[}, @var{value-if-not-found}@r{]}) @maindex CHECK_PROG Check whether program @var{prog-to-check-for} exists in @code{PATH}. If it is found, set @var{variable} to @var{value-if-found}, otherwise to @var{value-if-not-found}, if given. If @var{variable} was already set, do nothing. Calls @code{AC_SUBST} for @var{variable}. @end defmac @defmac AC_PATH_PROG (@var{variable}, @var{prog-to-check-for} @r{[}, @var{value-if-not-found}@r{]}) @maindex PATH_PROG Similar to @code{AC_CHECK_PROG}, but set @var{variable} to the entire path of @var{prog-to-check-for} if found. Otherwise, set @var{variable} to @var{value-if-not-found}, if given. If @var{variable} was already set, do nothing. Calls @code{AC_SUBST} for @var{variable}. @end defmac @defmac AC_CHECK_PROGS (@var{variable}, @var{progs-to-check-for} @r{[}, @var{value-if-not-found}@r{]}) @maindex CHECK_PROGS Check for each program in the whitespace-separated list @var{progs-to-check-for} exists in @code{PATH}. If it is found, set @var{variable} to the name of that program. Otherwise, continue checking the next program in the list. If none of the programs in the list are found, set @var{variable} to @var{value-if-not-found}; if @var{value-if-not-found} is not specified, the value of @var{variable} is not changed. Calls @code{AC_SUBST} for @var{variable}. @end defmac @defmac AC_PATH_PROGS (@var{variable}, @var{progs-to-check-for} @r{[}, @var{value-if-not-found}@r{]}) @maindex PATH_PROGS Like @code{AC_CHECK_PROGS}, but if any of @var{progs-to-check-for} are found, set @var{variable} to the entire pathname of the program found. @end defmac @node C Features, Command Line, File Existence, General Purpose Macros @section Checking For C Features These macros check for features of the C compiler, libraries, and headers. @defmac AC_CHECK_TYPE (@var{type}, @var{default}) @maindex CHECK_TYPE If the type @var{type} is not defined in @file{sys/types.h}, define it to be the C (or C++) builtin type @var{default}, e.g. @samp{short} or @samp{unsigned}. @end defmac @defmac AC_COMPILE_CHECK (@var{echo-text}, @var{includes}, @var{function-body}, @var{action-if-found} @r{[}, @var{action-if-not-found}@r{]}) @maindex COMPILE_CHECK This is an obsolete alias for @code{AC_TRY_LINK}, with the addition that it prints @samp{checking for @var{echo-text}} to the standard output first. @end defmac @defmac AC_CHECK_FUNC (@var{function}, @var{action-if-found} @r{[}, @var{action-if-not-found}@r{]}) @maindex CHECK_FUNC If @var{function} is available, run shell commands @var{action-if-found}, otherwise @var{action-if-not-found}. If the functions might be in libraries other than the default C library, first call @code{AC_CHECK_LIB} for those libraries. If you just want to define a symbol if the function is available, consider using @code{AC_CHECK_FUNCS} instead. @end defmac @defmac AC_CHECK_FUNCS (@var{function}@dots{}) @maindex CHECK_FUNCS @vindex HAVE_@var{function} For each given @var{function} in the whitespace-separated argument list that is available, define @code{HAVE_@var{function}} (in all caps). @xref{Specific Tests}, for a precise definition of ``define'' as it is used here. If the functions might be in libraries other than the default C library, first call @code{AC_CHECK_LIB} for those libraries. @end defmac @defmac AC_CHECK_HEADERS (@var{header-file}@dots{}) @maindex CHECK_HEADERS @vindex HAVE_@var{header} For each given system header file @var{header-file} in the whitespace-separated argument list that exists, define @code{HAVE_@var{header-file}} (in all caps). @xref{Specific Tests}, for a precise definition of ``define'' as it is used here. @end defmac @defmac AC_CHECK_HEADER (@var{header-file}, @var{action-if-found} @r{[}, @var{action-if-not-found}@r{]}) @maindex CHECK_HEADER If the system header file @var{header-file} exists, execute shell commands @var{action-if-found}, otherwise execute @var{action-if-not-found}. If you just want to define a symbol if the header file is available, consider using @code{AC_CHECK_HEADERS} instead. @end defmac @defmac AC_EGREP_HEADER (@var{pattern}, @var{header-file}, @var{action-if-found} @r{[}, @var{action-if-not-found}@r{]}) @maindex EGREP_HEADER If the output of running the preprocessor on the system header file @var{header-file} contains the @code{egrep} regular expression @var{pattern}, execute shell commands @var{action-if-found}, otherwise execute This macro calls @code{AC_PROG_CPP} or @code{AC_PROG_CXXCPP} (depending on which language is current, @pxref{Language Choice}), if it hasn't been called already. @var{action-if-not-found}. You can not check whether preprocessor symbols are defined this way, because they get expanded before @code{egrep} sees them. But you can almost always detect them by simply using @code{#ifdef} directives in your programs. @end defmac @defmac AC_EGREP_CPP (@var{pattern}, @var{program}, @var{action-if-found} @r{[}, @var{action-if-not-found}@r{]}) @maindex EGREP_CPP @var{program} is the text of a C or C++ program, on which shell variable and backquote substitutions are performed. If the output of running the preprocessor on @var{program} contains the @code{egrep} regular expression @var{pattern}, execute shell commands @var{action-if-found}, otherwise execute @var{action-if-not-found}. (It is an unfortunate oversight that we use the word @code{PROGRAM} in Autoconf macro names to sometimes mean C or C++ source code and sometimes mean a UNIX command.) This macro calls @code{AC_PROG_CPP} or @code{AC_PROG_CXXCPP} (depending on which language is current, @pxref{Language Choice}), if it hasn't been called already. @end defmac @defmac AC_REPLACE_FUNCS (@var{function-name}@dots{}) @maindex REPLACE_FUNCS For each given @var{function-name} in the whitespace-separated argument list that is not in the C library, add @samp{@var{function-name}.o} to the value of the @code{make} variable @code{LIBOBJS}. If the functions might be in libraries other than the default C library, first call @code{AC_CHECK_LIB} for those libraries. @end defmac @defmac AC_CHECK_SIZEOF (@var{type}) @maindex CHECK_SIZEOF Define @code{SIZEOF_@var{uctype}} to be the size in bytes of the C (or C++) builtin type @var{type}, e.g. @samp{int} or @samp{char *}. If @samp{type} is unknown to the compiler, gets a size of 0. @var{uctype} is @var{type}, with lowercase converted to uppercase, spaces changed to underscores, and asterisks changed to @samp{P}. For example, the call @example AC_CHECK_SIZEOF(int *) @end example @noindent defines @code{SIZEOF_INT_P} to be 8 on DEC Alpha AXP systems. @end defmac @defmac AC_TRY_CPP (@var{includes}, @var{action-if-true} @r{[}, @var{action-if-false}@r{]}) @maindex TRY_CPP @var{includes} is C or C++ @code{#include} statements and declarations, on which shell variable and backquote substitutions are performed. (Actually, it can be any C program, but other statements are probably not useful.) If the preprocessor produces no error messages while processing it, run shell commands @var{action-if-true}. Otherwise run shell commands @var{action-if-false}. This macro calls @code{AC_PROG_CPP} or @code{AC_PROG_CXXCPP} (depending on which language is current, @pxref{Language Choice}), if it hasn't been called already. @end defmac @defmac AC_TRY_LINK (@var{includes}, @var{function-body}, @var{action-if-found} @r{[}, @var{action-if-not-found}@r{]}) @maindex TRY_LINK Create a test C program to see whether a function whose body consists of @var{function-body} can be compiled and linked; @var{includes} is any @code{#include} statements needed by the code in @var{function-body}. If the file compiles and links successfully, run shell commands @var{action-if-found}, otherwise run @var{action-if-not-found}. @end defmac @defmac AC_TRY_RUN (@var{program}, @var{action-if-true} @r{[}, @var{action-if-false} @r{[}, @var{action-if-cross-compiling}@r{]]}) @maindex TRY_RUN @var{program} is the text of a C program, on which shell variable and backquote substitutions are performed. If it compiles and links successfully and returns an exit status of 0 when executed, run shell commands @var{action-if-true}. Otherwise run shell commands @var{action-if-false}. If the optional argument @var{action-if-cross-compiling} is given and the C compiler being used does not produce executables that run on the system where @code{configure} is being run, then the test program is not run. Instead, the shell commands @var{action-if-cross-compiling} are run. If that argument is given, this macro calls @code{AC_TRY_CROSS} if it has not already been called (@pxref{Compiler Characteristics}). @end defmac @node Command Line, Setting Variables, C Features, General Purpose Macros @section Checking Command Line Arguments These macros check whether the user gave @code{configure} various command line arguments. Like the general feature tests (@pxref{General Purpose Macros}), they may take an argument to use if the argument was given and one for if it was not given. @defmac AC_ARG_ENABLE (@var{feature}, @var{help-string}, @var{action-if-true} @r{[}, @var{action-if-false}@r{]}) @maindex ARG_ENABLE If the user gave @code{configure} the option @samp{--enable-@var{feature}} or @samp{--disable-@var{feature}}, run shell commands @var{action-if-true}. Otherwise run shell commands @var{action-if-false}. @var{help-string} is a description of the option which looks like this: @example --enable-readline support fancy command line editing @end example @noindent @var{help-string} may be more than one line long, if more detail is needed. Just make sure the columns line up in @samp{configure --help}. The name @var{feature} should consist only of alphanumeric characters and dashes. The @var{feature} indicates an optional user-level facility. This option allows users to choose which optional features to build and install. @samp{--enable-@var{feature}} options should never make a feature behave differently or cause one feature to replace another. They should only cause parts of the program to be built rather than left out. The user can give an argument by following the feature name with @samp{=} and the argument. Giving an argument of @samp{no} indicates that the feature is @emph{not} available. A feature with an argument looks like @samp{--enable-debug=stabs}. The argument is available to the shell commands @var{action-if-true} in the shell variable @code{enableval}. If no argument was given to @samp{--enable-@var{feature}}, @code{enableval} is @samp{yes}. @samp{--disable-@var{feature}} is equivalent to @samp{--enable-@var{feature}=no}. At present, arguments containing blanks are not handled correctly; if you need an argument to contain a list, require the items to be separated by commas instead. @end defmac @defmac AC_ARG_WITH (@var{package}, @var{help-string}, @var{action-if-true} @r{[}, @var{action-if-false}@r{]}) @maindex ARG_WITH If the user gave @code{configure} the option @samp{--with-@var{package}} or @samp{--without-@var{package}}, run shell commands @var{action-if-true}. Otherwise run shell commands @var{action-if-false}. @var{help-string} is a description of the option which looks like this: @example --with-gnu-as use the GNU assembler @end example @noindent @var{help-string} may be more than one line long, if more detail is needed. Just make sure the columns line up in @samp{configure --help}. The name @var{package} should consist only of alphanumeric characters and dashes. The @var{package} indicates another software package that this program should work with. For example, @samp{--with-gnu-ld} means work with the GNU linker instead of some other linker. @samp{--with-x11} means work with X11. The user can give an argument by following the package name with @samp{=} and the argument. Giving an argument of @samp{no} is for packages that would be used by default; it says to @emph{not} use the package. An argument that is neither @samp{yes} nor @samp{no} could include a name or number of a version of the other package, to specify more precisely which other package this program is supposed to work with. The argument is available to the shell commands @var{action-if-true} in the shell variable @code{withval}. If no argument was given to @samp{--with-@var{package}}, @code{withval} is @samp{yes}. @samp{--without-@var{package}} is equivalent to @samp{--with-@var{package}=no}. At present, arguments containing blanks are not handled correctly; if you need an argument to contain a list, require the items to be separated by commas instead. @end defmac @defmac AC_ENABLE (@var{feature}, @var{action-if-true} @r{[}, @var{action-if-false}@r{]}) @maindex ENABLE This is an obsolete version of @code{AC_ARG_ENABLE} that does not provide a help string. @end defmac @defmac AC_WITH (@var{package}, @var{action-if-true} @r{[}, @var{action-if-false}@r{]}) @maindex WITH This is an obsolete version of @code{AC_ARG_WITH} that does not provide a help string. @end defmac @node Setting Variables, Printing Messages, Command Line, General Purpose Macros @section Setting Variables These macros help other macros to define shell and @code{make} variables. @defmac AC_DEFINE (@var{variable} @r{[}, @var{value}@r{]}) @maindex DEFINE Define C preprocessor variable @var{variable}. If @var{value} is given, set @var{variable} to that value, otherwise set it to 1. To use a shell variable as the value, use @code{AC_DEFINE_UNQUOTED} instead and precede double quotes in the value with backslashes. This macro adds to the shell variable @code{DEFS}. @code{AC_OUTPUT} later substitutes the values in @code{DEFS} into the file(s) that it generates (typically @file{Makefile}). Alternately, if @code{AC_CONFIG_HEADER} has been called, @code{AC_OUTPUT} creates a header file by substituting the correct values into @code{#define} statements in a template file. For example, suppose your @file{configure.in} calls @code{AC_CONFIG_HEADER(conf.h)} and @code{AC_CHECK_HEADERS(unistd.h)}. You could have code like this in @file{conf.h.in}: @example @group /* Define as 1 if you have unistd.h. */ #define HAVE_UNISTD_H 0 @end group @end example On systems that have @file{unistd.h}, @code{configure} will change the 0 to a 1. On other systems, it will leave the line unchanged. Alternately, if you prefer to use @code{#ifdef}, your @file{conf.h.in} could have code like this: @example @group /* Define if you have unistd.h. */ #undef HAVE_UNISTD_H @end group @end example On systems that have @file{unistd.h}, @code{configure} will change the second line to read @samp{#define HAVE_UNISTD_H 1}. On other systems, it will comment that line out (in case the system predefines that symbol). Due to the syntactical bizarreness of the Bourne shell, do not use semicolons to separate @code{AC_DEFINE} calls from other macro calls or shell code; that can cause syntax errors in the resulting @code{configure} script. Use either spaces or newlines. That is, do this: @example AC_CHECK_HEADER(elf.h, AC_DEFINE(SVR4) LIBS="$LIBS -lelf") @end example @noindent or this: @example AC_CHECK_HEADER(elf.h, AC_DEFINE(SVR4) LIBS="$LIBS -lelf") @end example @noindent instead of this: @example AC_CHECK_HEADER(elf.h, AC_DEFINE(SVR4); LIBS="$LIBS -lelf") @end example @end defmac @defmac AC_DEFINE_UNQUOTED (@var{variable} @r{[}, @var{value}@r{]}) @maindex DEFINE_UNQUOTED Like @code{AC_DEFINE}, but it does nothing to quote @var{value} from various shell and @code{sed} expansions it will undergo. @var{value} will be used in many different contexts requiring different quoting, and it is up to you to make sure it works right. Use this macro instead of @code{AC_DEFINE} when @var{value} contains a shell variable. For example: @example AC_DEFINE_UNQUOTED(config_machfile, $@{machfile@}) @end example @end defmac @defmac AC_SUBST (@var{variable}) @maindex SUBST Substitute the variable @var{variable} when creating the output files (typically one or more @file{Makefile}s). This means replace instances of @samp{@@@var{variable}@@}, e.g. in @file{Makefile.in}, with the current value of the shell variable @var{variable}. If this macro were not called, the value of @var{variable} would not be set in the output files, even though @code{configure} had figured out a value for it. You can set or add to the value of @var{variable} in the usual shell way. For example, to add @samp{-ltermcap} to the value of the variable @code{LIBS}: @example LIBS="$LIBS -ltermcap" @end example @end defmac @defmac AC_SUBST_FILE (@var{variable}, @var{file}) @maindex SUBST_FILE Substitute the contents of the file @file{@var{srcdir}/@var{file}} into @file{Makefile} variable @var{variable} when creating the output files (typically one or more @file{Makefile}s). This macro is useful for inserting @file{Makefile} fragments for particular host or tartet types into @file{Makefile}s. @end defmac @node Printing Messages, Language Choice, Setting Variables, General Purpose Macros @section Printing Messages @code{configure} scripts need to give users running them several kinds of information. The following macros print messages in ways appropriate for different kinds of information. The arguments to all of them get enclosed in shell double quotes, so the shell performs variable and backquote substitution on them. These macros are all wrappers around the @code{echo} shell command. Other macros should rarely need to run @code{echo} directly to print messages for the @code{configure} user. Using these macros makes it easy to change how and when each kind of message is printed; such changes need only be made to the macro definitions, and all of the callers change automatically. @defmac AC_MSG_CHECKING (@var{feature-description}) @maindex MSG_CHECKING Notify the user that @code{configure} is checking for a particular feature. This macro prints a message that starts with @samp{checking }. It prints nothing if @code{configure} is run with the @samp{--silent} or @samp{--quiet} option. The @var{feature-description} should be something like @samp{whether the Fortran compiler accepts C++ comments} or @samp{for c89}. @end defmac @defmac AC_MSG_ERROR (@var{error-description}) @maindex MSG_ERROR Notify the user of an error that prevents @code{configure} from completing. This macro prints an error message on the standard error stream and exits @code{configure} with a nonzero status. @var{error-description} should be something like @samp{invalid value $HOME for \$HOME}. @end defmac @defmac AC_MSG_RESULT (@var{result-description}) @maindex MSG_RESULT Notify the user of the results of a check. This information is only printed if @code{configure} is run with the @samp{--verbose} option. @var{result-description} should be something like @samp{setting ADA to $ADA}. @end defmac @defmac AC_MSG_WARN (@var{problem-description}) @maindex MSG_WARN Notify the @code{configure} user of a possible problem. This macro prints the message on the standard error stream; @code{configure} continues running afterward, so macros that call @code{AC_MSG_WARN} should provide a default (back-up) behavior for the situations they warn about. @var{problem-description} should be something like @samp{ln -s seems to make hard links}. @end defmac @node Language Choice, Macro Ordering, Printing Messages, General Purpose Macros @section Language Choice Packages that use both C and C++ need to test features of both compilers. Autoconf-generated @code{configure} scripts check for C features by default. The following macros determine which language's compiler is used in tests that follow in @file{configure.in}. @defmac AC_LANG_C @maindex LANG_C Do compilation tests using @code{CC} and @code{CPP} and use extension @file{.c} for test programs. This is the initial state. @end defmac @defmac AC_LANG_CPLUSPLUS @maindex LANG_CPLUSPLUS Do compilation tests using @code{CXX} and @code{CXXCPP} and use extension @file{.C} for test programs. @end defmac @defmac AC_LANG_RESTORE @maindex LANG_RESTORE Select the language that is saved on the top of the stack, as set by @code{AC_LANG_SAVE}, and remove it from the stack. This macro is equivalent to either @code{AC_LANG_C} or @code{AC_LANG_CPLUSPLUS}, whichever had been run most recently when @code{AC_LANG_SAVE} was last called. Do not call this macro more times than @code{AC_LANG_SAVE}. @end defmac @defmac AC_LANG_SAVE @maindex LANG_SAVE Remember the current language (as set by @code{AC_LANG_C} or @code{AC_LANG_CPLUSPLUS}) on a stack. Does not change which language is current. Use this macro and @code{AC_LANG_RESTORE} in macros that need to temporarily switch to a particular language. @end defmac @defmac AC_REQUIRE_CPP @maindex REQUIRE_CPP Ensure that whichever preprocessor would currently be used for tests has been found. Calls @code{AC_REQUIRE} (@pxref{Macro Ordering}) with an argument of either @code{AC_PROG_CPP} or @code{AC_PROG_CXXCPP}, depending on which language is current. @end defmac @node Macro Ordering, , Language Choice, General Purpose Macros @section Macro Ordering These macros provide ways for other macros to make sure that they are called in the correct order. @defmac AC_BEFORE (@var{this-macro-name}, @var{called-macro-name}) @maindex BEFORE Make @code{m4} print a warning message on the standard error output if @var{called-macro-name} has already been called. @var{this-macro-name} should be the name of the macro that is calling @code{AC_BEFORE}. The macro @var{called-macro-name} must contain a call to @code{AC_PROVIDE} to indicate that it has been called. This macro should be used when one macro makes changes that might affect another macro, so that the other macro should probably not be called first. For example, @code{AC_PROG_CPP} checks whether the C compiler can run the C preprocessor when given the @samp{-E} option. It should therefore be called after any macros that change which C compiler is being used, such as @code{AC_PROG_CC}. So @code{AC_PROG_CC} contains: @example AC_BEFORE([$0], [AC_PROG_CPP]) @end example @noindent This warns the user if a call to @code{AC_PROG_CPP} has already occurred when @code{AC_PROG_CC} is called. @end defmac @defmac AC_OBSOLETE (@var{this-macro-name} @r{[}, @var{suggestion}@r{]}) @maindex OBSOLETE Make @code{m4} print a message on the standard error output warning that @var{this-macro-name} is obsolete, and giving the file and line number where it was called. @var{this-macro-name} should be the name of the macro that is calling @code{AC_BEFORE}. If @var{suggestion} is given, it is printed at the end of the warning message; for example, it can be a suggestion for what to use instead of @var{this-macro-name}. A sample call is: @example AC_OBSOLETE([$0], [; use AC_CHECK_HEADERS(unistd.h) instead]) @end example @end defmac @defmac AC_PROVIDE (@var{macro-name}) @maindex PROVIDE Set a flag recording that @var{macro-name} has been called. The argument should be the name of the macro that is calling @code{AC_PROVIDE}. An easy way to get it is from the @code{m4} builtin variable @code{$0}, like this: @example AC_PROVIDE([$0]) @end example @end defmac @defmac AC_REQUIRE (@var{macro-name}) @maindex REQUIRE If the @code{m4} macro @var{macro-name} has not already been called, call it (without any arguments). Make sure to quote @var{macro-name} with square brackets. The body of @var{macro-name} must contain a call to @code{AC_PROVIDE} to indicate that it has been called. Macros that need some other macro to be called before they are called can use @code{AC_REQUIRE} to ensure that it has been, in case the person who made @file{configure.in} forgot or didn't know to do it. @code{AC_REQUIRE} and @code{AC_PROVIDE} together can ensure that a macro is only called if it is needed, and only called once. @xref{Dependencies Between Macros}, for more information. @end defmac @node Manual Configuration, Writing Macros, General Purpose Macros, Top @chapter Manual Configuration Some kinds of features can't be guessed automatically by running test programs. For example, how to allocate a pty, or the details of the object file format, or special options that need to be passed to the compiler or linker to provide a POSIX or ANSI C environment. It is possible to check for such features using ad-hoc means, such as having @code{configure} check the output of the @code{uname} program, or looking for libraries that are unique to particular systems. However, Autoconf provides a uniform method for handling unguessable features. Like other GNU @code{configure} scripts, Autoconf-generated @code{configure} scripts can make decisions based on a canonical name for the system type, which has the form: @example @var{cpu}-@var{company}-@var{system} @end example @code{configure} can usually guess the canonical name for the type of system it's running on. To do so it runs a script called @code{config.guess}, which derives the name using the @code{uname} command or symbols predefined by the C preprocessor. Alternately, the user can specify the system type with command line arguments to @code{configure}. Doing so is necessary when cross-compiling. In the most complex case of cross-compiling, three system types are involved. The options to specify them are: @table @code @item --build=@var{build-type} the type of system on which the package is being configured and compiled; @item --host=@var{host-type} the type of system on which the package will run; @item --target=@var{target-type} the type of system for which any compiler tools in the package will produce code. @end table @noindent If the user gives @code{configure} a non-option argument, it is used as the default for the host, target, and build system types if the user does not specify them explicitly with options. The target and build types default to the host type if it is given and they are not. Note that if you are cross-compiling, you still have to specify the names of the cross-tools you use, in particular the C compiler, on the @code{configure} and @code{make} command lines, e.g., @example CC=m68k-coff-gcc configure --target=m68k-coff; CC=m68k-coff-gcc make @end example @code{configure} recognizes short aliases for many system types; for example, @samp{decstation} can be given on the command line instead of @samp{mips-dec-ultrix4.2}. @code{configure} runs a script called @code{config.sub} to canonicalize system type aliases. @defmac AC_CANONICAL_SYSTEM @maindex CANONICAL_SYSTEM Set shell and @code{make} variables to the names of the canonical system types. If the user did not specify one or more of those values on the command line, run @code{config.guess} to determine them. Run @code{config.sub} to canonicalize any aliases the user gave. If you use this macro, you must distribute those two shell scripts along with your source code (@pxref{Setup}, for information about the @code{AC_CONFIG_AUX_DIR} macro which you can use to control which directory @code{configure} looks for those scripts in). If you do not run this macro, @code{configure} ignores any @samp{--host}, etc. options given to it. The variables set are: @table @code @item @code{build}, @code{host}, @code{target} the canonical system names; @item @code{build_alias}, @code{host_alias}, @code{target_alias} the names the user specified, or the canonical names if @code{config.guess} was used; @item @code{build_cpu}, @code{build_vendor}, @code{build_os} @itemx @code{host_cpu}, @code{host_vendor}, @code{host_os} @itemx @code{target_cpu}, @code{target_vendor}, @code{target_os} the individual parts of the canonical names (for convenience). @end table @end defmac How do you use a canonical system type? Usually, you use it in one or more @code{case} statements in @file{configure.in} to select system-specific C files. Then link those files, which have names based on the system name, to generic names, such as @file{host.h} or @file{target.c}. The @code{case} statement patterns can use shell wildcards to group several cases together, like in this fragment: @example case "$target" in i386-*-mach* | i386-*-gnu*) obj_format=aout emulation=mach bfd_gas=yes ;; i960-*-bout) obj_format=bout ;; esac @end example @defmac AC_LINK_FILES (@var{link} @dots{}, @var{file} @dots{}) @maindex LINK_FILES Link each of the existing files @var{file} to the corresponding link name @var{link}. Makes a symbolic link if possible, otherwise a hard link. For example, this call: @example AC_LINK_FILES(config/sun3.h config/aout.h, host.h object.h) @end example @noindent creates in the current directory @file{host.h}, which is a link to @file{@var{srcdir}/config/sun3.h}, and @file{object.h}, which is a link to @file{@var{srcdir}/config/aout.h}. @end defmac @node Writing Macros, Caching Values, Manual Configuration, Top @chapter Writing Macros If your package needs to test for some feature that none of the macros supplied with Autoconf handles, you'll need to write one or more new Autoconf macros. Here are some suggestions and some of the rationale behind why the existing macros are written the way they are. You can also learn a lot about how to write Autoconf macros by looking at the existing ones. If something goes wrong in one or more of the Autoconf tests, this information can help you understand why they work the way they do and the assumptions behind them, which might help you figure out how to best solve the problem. If you add macros that you think would be useful to other people, or find problems with the distributed macros, please send electronic mail to @file{bug-gnu-utils@@prep.ai.mit.edu}, so we can consider them for future releases of Autoconf. Please include the Autoconf version number, which you can get by running @samp{autoconf --version}. @menu * Macro Format:: Basic format of an Autoconf macro. * Macro Naming:: What to call your new macros. * Quoting:: Protecting macros from unwanted expansion. * Dependencies Between Macros:: What to do when macros depend on other macros. * Checking for Files:: Finding whether a file exists. * Checking for Symbols:: Finding whether a symbol is defined. * Test Programs:: Writing programs to test for features. * Multiple Cases:: Tests for several possible values. @end menu @node Macro Format, Macro Naming, , Writing Macros @section Macro Format Autoconf macros are defined as arguments to the @code{m4} builtin command @code{define}. Their overall structure looks like this: @example define(@var{macro-name}, [@var{macro-body}])dnl @end example @noindent The square brackets here do not indicate optional text: they should literally be present in the macro definition. The @code{m4} builtin @code{dnl} prevents a newline from being inserted in the output where the macro is defined; without it, the generated @code{configure} script would begin with dozens of blank lines. @code{dnl} is also used to introduce comments in @code{m4}; it causes @code{m4} to discard the rest of the input line. You should quote the entire macro body with square brackets to avoid macro expansion problems (@pxref{Quoting}). You can refer to any arguments passed to the macro as @samp{$1}, @samp{$2}, etc. @xref{Definitions, , How to define new macros, m4.info, GNU m4}, for more complete information on writing @code{m4} macros. @node Macro Naming, Quoting, Macro Format, Writing Macros @section Macro Naming All of the Autoconf macros have all-uppercase names starting with @samp{AC_} to prevent them from accidentally conflicting with other text. All shell variables that they use for internal purposes have mostly-lowercase names starting with @samp{ac_}. To ensure that your macros don't conflict with present or future Autoconf macros, you should prefix your own macro names and any shell variables they use with some other sequence. Possibilities include your initials, or an abbreviation for the name of your organization or software package. Most of the Autoconf macros' names follow a structured naming convention that indicates the kind of feature check by the name. The macro names consist of several words, separated by underscores, going from most general to most specific. The names of their cache variables use the same convention (@pxref{Cache Variables}, for more information on them). The first word of the name after @samp{AC_} usually tells the category of feature being tested. Here are the categories for specific test macros, the kind of macro that you are more likely to write. You are not required to use these names, but consistency helps readability. @table @code @item C C language builtin features. @item DECL Declarations of C variables in header files. @item FUNC Functions in libraries. @item HEADER Header files. @item OS Quirks of particular operating systems. @item PATH The full path names to files. @item PROG The names of programs. @item STRUCT Definitions of C structures in header files. @item SYS Operating system features. @item TYPE C builtin or declared types. @end table After the category comes the name of the particular feature being tested. Any further words in the macro name indicate particular aspects of the feature. For example, @code{AC_FUNC_UTIME_NULL} checks the behavior of the @code{utime} function when called with a @code{NULL} pointer. @node Quoting, Dependencies Between Macros, Macro Naming, Writing Macros @section Quoting Macros that are called by other macros are evaluated by @code{m4} several times; each evaluation might require another layer of quotes to prevent unwanted expansions of macros or @code{m4} builtins, such as @samp{define} and @samp{$1}. Quotes are also required around macro arguments that contain commas, since commas separate the arguments from each other. It's a good idea to quote any macro arguments that contain newlines or calls to other macros, as well. Autoconf (in @file{acgeneral.m4}) changes the @code{m4} quote characters from the default @samp{`} and @samp{'} to @samp{[} and @samp{]}, because many of the macros use @samp{`} and @samp{'}, mismatched. However, in a few places the macros need to use brackets. In those places, they use the @code{m4} builtin command @code{changequote} to temporarily disable quoting before the code that uses brackets, like this: @example changequote(, )dnl @end example @noindent Then they turn quoting back on again with another call to @code{changequote}: @example changequote([, ])dnl @end example When you create a @code{configure} script using newly written macros, examine it carefully to check whether you need to add more quotes in your macros. If one or more words have disappeared in the @code{m4} output, you need more quotes. When in doubt, quote. However, it's also possible to put on too many layers of quotes. If this happens, the resulting @code{configure} script will contain unexpanded macros. The @code{autoconf} program checks for this problem by doing @samp{grep AC_ configure}. @node Dependencies Between Macros, Checking for Files, Quoting, Writing Macros @section Dependencies Between Macros Some Autoconf macros depend on other macros having been called first in order to work correctly. Autoconf provides a way to ensure that certain macros are called if needed and a way to warn the user if macros are called in an order that might cause incorrect operation. @menu * Prerequisite Macros:: Ensuring required information. * Suggested Ordering:: Warning about possible ordering problems. @end menu @node Prerequisite Macros, Suggested Ordering, , Dependencies Between Macros @subsection Prerequisite Macros A macro that you write might need to use values that have previously been computed by other macros. For example, if you write a new macro that uses the C preprocessor, it depends on @code{AC_PROG_CPP} having been called first to set the shell variable @code{CPP} (@pxref{Alternative Programs}). Rather than forcing the user of the macros to keep track of all of the dependencies between them, you can use the macros @code{AC_PROVIDE} and @code{AC_REQUIRE} to do it automatically. @xref{Macro Ordering}, for more information on their syntax. The new macro that runs the C preprocessor should contain, somewhere before @code{CPP} is used, the statement @example AC_REQUIRE([AC_PROG_CPP]) @end example @noindent and the macro @code{AC_PROG_CPP} should contain the statement (anywhere in its body) @example AC_PROVIDE([$0]) @end example @noindent Then, when the new macro is run, it will invoke @code{AC_PROG_CPP} if and only if @code{AC_PROG_CPP} has not already been run. @node Suggested Ordering, , Prerequisite Macros, Dependencies Between Macros @subsection Suggested Ordering Some macros should be run before another macro if both are called, but neither requires the other to be called. For example, a macro like @code{AC_OS_AIX} that changes the behavior of the C compiler (@pxref{UNIX Variants}) should be called before any macros that run the C compiler. Many of these dependencies are noted in the documentation. Autoconf provides a way to warn users when macros with this kind of dependency appear out of order in a @file{configure.in} file. The warning occurs when creating @file{configure} from @file{configure.in}, not when running @file{configure}. It is not a fatal error; @file{configure} is created as usual. The @code{AC_BEFORE} macro causes @code{m4} to print a warning message on the standard error output when a macro is used before another macro which might change its behavior. The macro which should come first should contain a call to @code{AC_BEFORE} and the macro which should come later should contain a call to @code{AC_PROVIDE}. For example, @code{AC_OS_AIX} contains @example AC_BEFORE([$0], [AC_TRY_LINK]) @end example @noindent and @code{AC_TRY_LINK} contains @example AC_PROVIDE([$0]) @end example @noindent As a result, if @code{AC_OS_AIX} is called after @code{AC_TRY_LINK}, it will note that @code{AC_TRY_LINK} has already been called and print a warning message. @node Checking for Files, Checking for Symbols, Dependencies Between Macros, Writing Macros @section Checking for Files If you need to check whether a file other than a C header file exists, use @samp{test -f @var{filename}}. If you need to make multiple checks using @code{test}, combine them with the shell operators @samp{&&} and @samp{||} instead of using the @code{test} operators @samp{-a} and @samp{-o}. On System V, the precedence of @samp{-a} and @samp{-o} is wrong relative to the unary operators; consequently, POSIX does not specify them, so using them is nonportable. If you combine @samp{&&} and @samp{||} in the same statement, keep in mind that they have equal precedence. Do not use @samp{test -x}, because 4.3BSD does not have it. Use @samp{test -f} or @samp{test -r} instead. @node Checking for Symbols, Test Programs, Checking for Files, Writing Macros @section Checking for Symbols If you need to check whether a symbol is defined in a C header file, you can use @code{AC_EGREP_HEADER} if the symbol is not a C preprocessor macro (@pxref{C Features}), or compile a small test program that includes the file and references the symbol (@pxref{Test Programs}). Don't directly @code{grep} for the symbol in the file, because on some systems it might be defined in another header file that the file you are checking @samp{#include}s. However, if you need to check for a particular UNIX variant which is distinguished by having certain text in a certain file, then use @code{grep} (or @code{egrep}). But don't use @samp{grep -s} to suppress output, because @samp{grep -s} on System V does not suppress output, only error messages. Instead, redirect the standard output and standard error (in case the file doesn't exist) of @code{grep} to @file{/dev/null}. Check the exit status of @code{grep} to determine whether it found a match. To check whether the Autoconf macros have already defined a certain C preprocessor symbol, you can use a @code{case} statement like this: @example case "$DEFS" in *HAVE_FOO*) ;; *) LIBOBJS="$LIBOBJS foo.o" ;; esac @end example @noindent Make sure to enclose the variable name you are checking (usually @code{DEFS}) in double quotes, because otherwise some old versions of @code{bash} misinterpret the statement. @node Test Programs, Multiple Cases, Checking for Symbols, Writing Macros @section Test Programs Autoconf checks for many features by compiling small test programs. To find out whether a library function is available, Autoconf tries to compile a small program that uses it. This is unlike Larry Wall's Metaconfig, which uses @code{nm} or @code{ar} on the C library to try to figure out which functions are available. Trying to link with the function is usually a more reliable and flexible approach because it avoids dealing with the variations in the options and output formats of @code{nm} and @code{ar} and in the location of the standard libraries. It also allows @code{configure} to check aspects of the function's runtime behavior if needed. On the other hand, it is sometimes slower than scanning the libraries. If you need to check for a condition other than whether some symbol exists on the system or has a certain value, then you can't use @code{AC_TRY_LINK} (@pxref{C Features}). You have to write a test program by hand. You can compile and run it using @code{AC_TRY_RUN} (@pxref{C Features}). Try to avoid writing test programs if possible, because using them prevents people from configuring your package for cross-compiling. If it's really best that you test for a run-time behavior, try to provide a default ``worst case'' value to use when cross-compiling makes run-time tests impossible. You do this by passing the optional last argument to @code{AC_TRY_RUN}. @menu * Guidelines:: General rules for writing test programs. * Tricks:: Special ways to work around problems. @end menu @node Guidelines, Tricks, , Test Programs @subsection Guidelines for Test Programs Test programs should return 0 if the test succeeds, nonzero otherwise, so that success can be distinguished easily from a core dump or other failure; segmentation violations and other failures produce a nonzero exit status. Test programs should @code{exit}, not @code{return}, from @code{main}, because on some systems the argument to @code{return} in @code{main} is ignored. They should not write anything to the standard output. Test programs can use @code{#if} or @code{#ifdef} to check the values of preprocessor macros defined by tests that have already run. For example, if you call @code{AC_HEADER_STDC}, then later on in @file{configure.in} you can have a test program that includes an ANSI C header file conditionally: @example @group #if STDC_HEADERS #include #endif @end group @end example If a test program needs to use or create a data file, give it a name that starts with @file{conftest}, such as @file{conftestdata}. The @code{configure} script cleans up by running @samp{rm -rf conftest*} after running test programs and if the script is interrupted. @node Tricks, , Guidelines, Test Programs @subsection Tricks for Test Programs If a test program calls a function with invalid parameters (just to see whether it exists), organize the program to ensure that it never invokes that function. You can do this by calling it in another function that is never invoked. You can't do it by putting it after a call to @code{exit}, because GCC version 2 knows that @code{exit} never returns and optimizes out any code that follows it in the same block. If you include any header files, make sure to call the functions relevant to them with the correct number of arguments, even if they are just 0, to avoid compilation errors due to prototypes. GCC version 2 has internal prototypes for several functions that it automatically inlines; for example, @code{memcpy}. To avoid errors when checking for them, either pass them the correct number of arguments or redeclare them with a different return type (such as @code{char}). @node Multiple Cases, , Test Programs, Writing Macros @section Multiple Cases Some operations are accomplished in several possible ways, depending on the UNIX variant. Checking for them essentially requires a ``case statement''. Autoconf does not directly provide one; however, it is easy to simulate by using a shell variable to keep track of whether a way to perform the operation has been found yet. Here is an example excerpted from the @file{configure.in} for GNU @code{find}. It uses the shell variable @code{fstype} to keep track of whether the remaining cases need to be checked. There are several more cases which are not shown here but follow the same pattern. @example @group echo checking how to get filesystem type # SVR4. AC_TRY_CPP([#include #include ], AC_DEFINE(FSTYPE_STATVFS) fstype=1) if test -z "$fstype"; then # SVR3. AC_TRY_CPP([#include #include ], AC_DEFINE(FSTYPE_USG_STATFS) fstype=1) fi if test -z "$fstype"; then # AIX. AC_TRY_CPP([#include #include ], AC_DEFINE(FSTYPE_AIX_STATFS) fstype=1) fi @end group @end example @node Caching Values, Makefiles, Writing Macros, Top @chapter Caching Values To avoid checking for the same features repeatedly in various @code{configure} scripts (or repeated runs of one script), @code{configure} saves the results of many of its checks in a @dfn{cache file}. If, when a @code{configure} script runs, it finds a cache file, it reads from it the results from previous runs and avoids rerunning those checks. As a result, @code{configure} can run much faster than if it had to perform all of the checks every time. @defmac AC_CACHE_VAL (@var{cache-id}, @var{commands-to-set-it}) @maindex CACHE_VAL Ensure that the results of the check identified by @var{cache-id} are available. If the results of the check were in the cache file that was read, print a verbose message saying so; otherwise, run the shell commands @var{commands-to-set-it}. Those commands should have no side effects except for setting the variable @var{cache-id}. In particular, they should not call @code{AC_DEFINE}; the code that follows the call to @code{AC_CACHE_VAL} should do that, based on the cached value. Also, they should not print any messages, for example with @code{AC_MSG_CHECKING}; do that before calling @code{AC_CACHE_VAL}, so the messages are printed regardless of whether the results of the check are retrieved from the cache or determined by running the shell commands. If the shell commands are run to determine the value, the value will be saved in the cache file just before @code{configure} creates its output files. @end defmac @menu * Cache Files:: Files @code{configure} uses for caching. * Cache Variables:: Shell variables used in caches. @end menu @node Cache Files, Cache Variables, , Caching Values @section Cache Files The cache file is a shell script that caches the results of configure tests run on one system so they can be shared between configure scripts and configure runs. It is not useful on other systems. If its contents are invalid for some reason, the user may delete or edit it. By default, configure uses @file{./config.cache} as the cache file, creating it if it does not exist already. @code{configure} accepts the @samp{--cache-file=@var{file}} option to use a different cache file; that is what @code{configure} does when it calls @code{configure} scripts in subdirectories, so they share the cache. @xref{Setup}, for information on configuring subdirectories with the @code{AC_CONFIG_SUBDIRS} macro. @file{config.status} only pays attention to the cache file if it is given the @samp{--recheck} option, which makes it rerun @code{configure}. It is wrong to try to distribute cache files for particular system types. There is too much room for error in doing that, and too much administrative overhead in maintaining them. For any features that can't be guessed automatically, use the standard method of the canonical system type and linking files (@pxref{Manual Configuration}). The cache file on a particular system will gradually accumulate whenever someone runs a @code{configure} script; it will be initially nonexistent. Running @code{configure} merges the new cache results with the existing cache file. The site initialization script can specify a site-wide cache file to use instead of the default, to make it work transparently (@pxref{Site Default Values}). @node Cache Variables, , Cache Files, Caching Values @section Cache Variables The names of cache variables should have the following format: @example @var{package-prefix}_cv_@var{value-type}_@var{specific-value}@r{[}_@var{additional-options}@r{]} @end example @noindent for example, @samp{ac_cv_header_stat_broken} or @samp{ac_cv_prog_gcc_traditional}. The parts of the variable name are: @table @asis @item @var{package-prefix} An abbreviation for your package or organization; the same prefix you begin local Autoconf macros with, except lowercase by convention. For cache values used by the distributed Autoconf macros, this value is @samp{ac}. @item @code{_cv_} Indicates that this shell variable is a cache value. @item @var{value-type} A convention for classifying cache values, to produce a rational naming system. The values used in Autoconf are for the following classes of features; use them where applicable, otherwise invent your own categories: @table @code @item c C language @item func C functions @item group Unix groups @item header C header files @item lib C libraries @item path the absolute path names of programs @item prog the base names of programs @item struct C structures @item sys operating systems @item type C types @item var C variables in libraries @item x X Window System @end table @item @var{specific-value} Which member of the class of cache values this test applies to. For example, which function (@samp{alloca}), program (@samp{gcc}), or @code{make} variable (@samp{INSTALL}). @item @var{additional-options} Any particular behavior of the specific member that this test applies to. For example, @samp{broken} or @samp{set}. This part of the name may be omitted if it does not apply. @end table Like their names, the values the may be assigned to cache variables have a few restrictions. The values may not contain single quotes or curly braces. Usually, their values will be boolean (@samp{yes} or @samp{no}) or the names of files or functions; so this is not an important restriction. @node Makefiles, Invoking configure, Caching Values, Top @chapter Makefiles Each subdirectory in a distribution should come with a file @file{Makefile.in}, from which @code{configure} will produce a @file{Makefile} in that directory. Most of the substitutions that @code{configure} does are simple: for each configuration variable that the package uses, it just replaces occurrences of @samp{@@@var{variable}@@} with the value that @code{configure} has determined for that variable. Any occurrences of @samp{@@@var{variable}@@} for variables that @code{configure} does not know about are passed through unchanged. There is no point in checking for the correct value to give a variable that is never used. Every variable that the @code{configure} script might set a value for should appear in a @samp{@@@var{variable}@@} reference in at least one @file{Makefile.in}. If @code{AC_CONFIG_HEADER} is called, @code{configure} replaces @samp{@@DEFS@@} with @samp{-DHAVE_CONFIG_H}, since the contents of @code{DEFS} would be redundant. @xref{Makefile Conventions, , Makefile Conventions, standards.info, The GNU Coding Standards}, for more information on what to put in Makefiles. @xref{Sample Makefile.in}, for an example of a real @file{Makefile.in}. @menu * Predefined Variables:: Heavily used @code{make} variables. * VPATH Substitutions:: Compiling in a different directory. * Automatic Remaking:: Makefile rules for configuring. @end menu @node Predefined Variables, VPATH Substitutions, , Makefiles @section Predefined Variables Some @code{make} variables are predefined by the Autoconf macros. @code{AC_SUBST} is called for them automatically (@pxref{Setting Variables}), so in your @file{Makefile.in} files you can get their values by enclosing their names in @samp{@@} characters. @ifinfo @xref{Makefiles}, for more information on @samp{@@} substitutions. @end ifinfo The variables that are defined by the general purpose Autoconf macros are: @defvar exec_prefix The installation prefix for architecture-specific files. @end defvar @defvar prefix The installation prefix for architecture-independent files. @end defvar @defvar srcdir The directory that contains the source code for that @file{Makefile}. @end defvar @defvar top_srcdir The top-level source code directory for the package. In the top-level directory, this is the same as @code{srcdir}. @end defvar @defvar DEFS @samp{-D} options to pass to the C compiler. If @code{AC_CONFIG_HEADER} is called, @code{configure} replaces @samp{@@DEFS@@} with @samp{-DHAVE_CONFIG_H}, since the contents of @code{DEFS} would be redundant. @end defvar @defvar LIBS @samp{-l} and @samp{-L} options to pass to the linker. @end defvar @defvar LIBOBJS Names of object files (ending in @file{.o}). Set by @code{AC_REPLACE_FUNCS} (@pxref{C Features}). @end defvar @node VPATH Substitutions, Automatic Remaking, Predefined Variables, Makefiles @section @code{VPATH} Substitutions You might want to compile a software package in a different directory from the one that contains the source code. Doing this allows you to compile the package for several architectures simultaneously from the same copy of the source code and keep multiple sets of object files on disk. To support doing this, @code{make} uses the @code{VPATH} variable to find the files that are in the source directory. GNU @code{make} and most other recent @code{make} programs can do this. Older @code{make} programs do not support @code{VPATH}; when using them, the source code must be in the same directory as the object files. To support @code{VPATH}, each @file{Makefile.in} should contain two lines that look like: @example srcdir = @@srcdir@@ VPATH = @@srcdir@@ @end example Do not set @code{VPATH} to the value of another variable, for example @samp{VPATH = $(srcdir)}, because some versions of @code{make} do not do variable substitutions on the value of @code{VPATH}. @code{configure} substitutes in the correct value for @code{srcdir} when it produces @file{Makefile.in}. Do not use the @code{make} variable @code{$<}, which expands to the pathname of the file in the source directory (found with @code{VPATH}), except in implicit rules. (An implicit rule is one such as @samp{.c.o}, which tells how to create a @file{.o} file from a @file{.c} file.) Some versions of @code{make} do not set @code{$<} in explicit rules; they expand it to an empty value. Instead, @file{Makefile} command lines should always refer to source files by prefixing them with @samp{$(srcdir)/}. For example: @example time.info: time.texinfo $(MAKEINFO) $(srcdir)/time.texinfo @end example @node Automatic Remaking, , VPATH Substitutions, Makefiles @section Automatic Remaking You can put rules like the following in the top-level @file{Makefile.in} for a package to automatically update the configuration information when you change the configuration files. This example includes all of the optional files, such as @file{aclocal.m4} and those related to configuration header files. Omit from the @file{Makefile.in} rules any of these files that your package does not use. The @file{stamp-} files are necessary because the timestamps of @file{config.h.in} and @file{config.h} will not be changed if remaking them does not change their contents. This feature avoids unnecessary recompilation. You should include the file @file{stamp-h.in} your package's distribution, so @code{make} will consider @file{config.h.in} up to date. @example @group configure: configure.in aclocal.m4 cd $@{srcdir@} && autoconf # autoheader might not change config.h.in config.h.in: stamp-h.in stamp-h.in: configure.in aclocal.m4 acconfig.h config.h.top config.h.bot cd $@{srcdir@} && autoheader touch $@{srcdir@}/stamp-h.in # config.status might not change config.h # Don't rerun config.status if we just configured. config.h: stamp-h stamp-h: config.h.in config.status test ! -f stamp-h || ./config.status touch stamp-h Makefile: Makefile.in config.status ./config.status config.status: configure ./config.status --recheck @end group @end example @xref{Invoking config.status}, for more information on handling configuration-related dependencies. @node Invoking configure, Invoking config.status, Makefiles, Top @chapter Running @code{configure} Scripts A software package that uses a @code{configure} script should be distributed with a file @file{Makefile.in}, but no @file{Makefile}; that way, the user has to properly configure the package for the local system before compiling it. Below are instructions on how to configure a package that uses a @code{configure} script, suitable for inclusion as an @file{INSTALL} file in the package. @menu * Basic Installation:: Instructions for typical cases. * Compilers and Options:: Selecting compilers and optimization. * Build Directory:: Configuring in a different directory. * Installation Directories:: Installing in different directories. * System Type:: Specifying the system type. * Optional Features:: Selecting optional features. @end menu @include install.texi @node Invoking config.status, Site Default Values, Invoking configure, Top @chapter Recreating a Configuration The @code{configure} script creates a file named @file{config.status} which describes which configuration options were specified when the package was last configured. This file is a shell script which, if run, will recreate the same configuration. You can give @file{config.status} the @samp{--recheck} option to update itself. This option is useful if you change @code{configure}, so that the results of some tests might be different from the previous run. The @samp{--recheck} option re-runs @code{configure} with the same arguments you used before, plus the @samp{--no-create} option, which prevents @code{configure} from running @file{config.status} and creating @file{Makefile} and other files. (This is so other @file{Makefile} rules can run @file{config.status} when it changes; @pxref{Automatic Remaking}, for an example). @file{config.status} also accepts the options @samp{--help}, which prints a summary of the options to @file{config.status}, and @samp{--version}, which prints the version of Autoconf used to create the @code{configure} script that generated @file{config.status}. @file{config.status} checks several optional environment variables that can alter its behavior: @defvar CONFIG_SHELL The shell with which to run @code{configure} for the @samp{--recheck} option. The default is @file{/bin/sh}. @end defvar @defvar CONFIG_STATUS The file name to use for the shell script that records the configuration. The default is @file{./config.status}. This variable is useful when one package uses parts of another and the @file{configure} scripts shouldn't be merged because they are maintained separately. @end defvar The following variables provide one way for separately distributed packages to share the values computed by @code{configure}. Doing so can be useful if some of the packages need a superset of the features that one of them, perhaps a common library, does. These variables allow a @file{config.status} file to create files other than the ones that its @file{configure.in} specifies, so it can be used for a different package. @defvar CONFIG_FILES The files in which to perform @samp{@@@var{variable}@@} substitutions. The default is the arguments given to @code{AC_OUTPUT} in @file{configure.in}. @end defvar @defvar CONFIG_HEADERS The files in which to substitute C @code{#define} statements. The default is the arguments given to @code{AC_CONFIG_HEADER}; if that macro was not called, @file{config.status} ignores this variable. @end defvar These variables also allow you to write @file{Makefile} rules that regenerate only some of the files. For example, in the dependencies given above (@pxref{Automatic Remaking}), @file{config.status} is run twice when @file{configure.in} has changed. If that bothers you, you can make each run only regenerate the files for that rule: @example @group # config.status might not change config.h config.h: stamp-h stamp-h: config.h.in config.status CONFIG_FILES= CONFIG_HEADERS=config.h ./config.status touch stamp-h Makefile: Makefile.in config.status CONFIG_FILES=Makefile CONFIG_HEADERS= ./config.status @end group @end example @noindent (If @file{configure.in} does not call @code{AC_CONFIG_HEADER}, there is no need to set @code{CONFIG_HEADERS} in the @code{make} rules.) @node Site Default Values, Old Macro Names, Invoking config.status, Top @chapter Site Default Values Autoconf-generated @code{configure} scripts support site and system wide initialization files. You can create these files to provide default values for some configuration values, both on all of your systems and separately for each architecture. @code{configure} reads the shell script @file{@var{exec_prefix}/lib/config.site} if it exists, then @file{@var{prefix}/lib/config.site} if it exists. Thus, settings in system dependent files override those in system independent ones in case of conflict. @code{configure} reads any cache file after it has read any site files. This way, the site file can define a default cache file, to be shared between all Autoconf-generated @code{configure} scripts run on that system. Site files can be arbitrary shell scripts, but only certain kinds of code are really appropriate to be in them. Besides a cache file, they are good places to set default values for other shell variables like @code{CC}, if you need to give them unusual values: anything you would normally do, repetitively, on the command line. If you use non-default values for @var{prefix} or @var{exec_prefix}, you can't set them in the site file, since you have to specify them on the command line in order for @code{configure} to find the site file! In addition, it is possible to set some cache values in the site file. If you are cross-compiling, it is impossible to check features that require running a test program. You could ``prime the cache'' by setting those values correctly for that system in @file{@var{exec_prefix}/lib/config.site}. The cache file is careful to not override any variables set in the site files. Similarly, you should not override command-line options in the site files. Your code should check that variables such as @code{prefix} and @code{cache_file} have their default values (as set near the top of @code{configure}) before changing them. @node Old Macro Names, Example, Site Default Values, Top @chapter Old Macro Names In version 2 of Autoconf, most of the macros were renamed to use a more uniform and descriptive naming scheme. Here are the old names of the macros that were renamed, followed by the current names of those macros. Although the old names are still accepted by the @code{autoconf} program for backward compatibility, the old names are considered obsolete. @xref{Macro Naming}, for a description of the new naming scheme. @table @code @item AC_NOTICE @vindex NOTICE @vindex INIT_NOTICE @code{AC_INIT_NOTICE} @item AC_PARSEARGS @vindex PARSEARGS @vindex INIT_PARSEARGS @code{AC_INIT_PARSEARGS} @item AC_PREPARE @vindex PREPARE @vindex INIT_PREPARE @code{AC_INIT_PREPARE} @item AC_CHECKING @vindex CHECKING @vindex MSG_CHECKING @code{AC_MSG_CHECKING} @item AC_VERBOSE @vindex VERBOSE @vindex MSG_RESULT @code{AC_MSG_RESULT} @item AC_WARN @vindex WARN @vindex MSG_WARN @code{AC_MSG_WARN} @item AC_ERROR @vindex ERROR @vindex MSG_ERROR @code{AC_MSG_ERROR} @item AC_PROGRAM_CHECK @vindex PROGRAM_CHECK @vindex CHECK_PROG @code{AC_CHECK_PROG} @item AC_PROGRAM_PATH @vindex PROGRAM_PATH @vindex PATH_PROG @code{AC_PATH_PROG} @item AC_PROGRAMS_CHECK @vindex PROGRAMS_CHECK @vindex CHECK_PROGS @code{AC_CHECK_PROGS} @item AC_PROGRAMS_PATH @vindex PROGRAMS_PATH @vindex PATH_PROGS @code{AC_PATH_PROGS} @item AC_HAVE_LIBRARY @vindex HAVE_LIBRARY @vindex CHECK_LIB @code{AC_CHECK_LIB} @item AC_HEADER_EGREP @vindex HEADER_EGREP @vindex EGREP_HEADER @code{AC_EGREP_HEADER} @item AC_PROGRAM_EGREP @vindex PROGRAM_EGREP @vindex EGREP_CPP @code{AC_EGREP_CPP} @item AC_TEST_PROGRAM @vindex TEST_PROGRAM @vindex TRY_RUN @code{AC_TRY_RUN} @item AC_TEST_CPP @vindex TEST_CPP @vindex TRY_CPP @code{AC_TRY_CPP} @item AC_HEADER_CHECK @vindex HEADER_CHECK @vindex CHECK_HEADER @code{AC_CHECK_HEADER} @item AC_FUNC_CHECK @vindex FUNC_CHECK @vindex CHECK_FUNC @code{AC_CHECK_FUNC} @item AC_HAVE_FUNCS @vindex HAVE_FUNCS @vindex CHECK_FUNCS @code{AC_CHECK_FUNCS} @item AC_HAVE_HEADERS @vindex HAVE_HEADERS @vindex CHECK_HEADERS @code{AC_CHECK_HEADERS} @item AC_SIZEOF_TYPE @vindex SIZEOF_TYPE @vindex CHECK_SIZEOF @code{AC_CHECK_SIZEOF} @item AC_GCC_TRADITIONAL @vindex GCC_TRADITIONAL @vindex PROG_GCC_TRADITIONAL @code{AC_PROG_GCC_TRADITIONAL} @item AC_MINUS_C_MINUS_O @vindex MINUS_C_MINUS_O @vindex PROG_CC_C_O @code{AC_PROG_CC_C_O} @item AC_SET_MAKE @vindex SET_MAKE @vindex PROG_MAKE_SET @code{AC_PROG_MAKE_SET} @item AC_YYTEXT_POINTER @vindex YYTEXT_POINTER @vindex DECL_YYTEXT @code{AC_DECL_YYTEXT} @item AC_LN_S @vindex LN_S @vindex PROG_LN_S @code{AC_PROG_LN_S} @item AC_RSH @vindex RSH @vindex PROG_RSH @code{AC_PROG_RSH} @item AC_STDC_HEADERS @vindex STDC_HEADERS @vindex HEADER_STDC @code{AC_HEADER_STDC} @item AC_MAJOR_HEADER @vindex MAJOR_HEADER @vindex HEADER_MAJOR @code{AC_HEADER_MAJOR} @item AC_STAT_MACROS_BROKEN @vindex STAT_MACROS_BROKEN @vindex HEADER_STAT @code{AC_HEADER_STAT} @item AC_SYS_SIGLIST_DECLARED @vindex SYS_SIGLIST_DECLARED @vindex DECL_SYS_SIGLIST @code{AC_DECL_SYS_SIGLIST} @item AC_GETGROUPS_T @vindex GETGROUPS_T @vindex TYPE_GETGROUPS @code{AC_TYPE_GETGROUPS} @item AC_UID_T @vindex UID_T @vindex TYPE_UID_T @code{AC_TYPE_UID_T} @item AC_SIZE_T @vindex SIZE_T @vindex TYPE_SIZE_T @code{AC_TYPE_SIZE_T} @item AC_PID_T @vindex PID_T @vindex TYPE_PID_T @code{AC_TYPE_PID_T} @item AC_OFF_T @vindex OFF_T @vindex TYPE_OFF_T @code{AC_TYPE_OFF_T} @item AC_MODE_T @vindex MODE_T @vindex TYPE_MODE_T @code{AC_TYPE_MODE_T} @item AC_RETSIGTYPE @vindex RETSIGTYPE @vindex TYPE_SIGNAL @code{AC_TYPE_SIGNAL} @item AC_MMAP @vindex MMAP @vindex FUNC_MMAP @code{AC_FUNC_MMAP} @item AC_VPRINTF @vindex VPRINTF @vindex FUNC_VPRINTF @code{AC_FUNC_VPRINTF} @item AC_VFORK @vindex VFORK @vindex FUNC_VFORK @code{AC_FUNC_VFORK} @item AC_WAIT3 @vindex WAIT3 @vindex FUNC_WAIT3 @code{AC_FUNC_WAIT3} @item AC_ALLOCA @vindex ALLOCA @vindex FUNC_ALLOCA @code{AC_FUNC_ALLOCA} @item AC_GETLOADAVG @vindex GETLOADAVG @vindex FUNC_GETLOADAVG @code{AC_FUNC_GETLOADAVG} @item AC_UTIME_NULL @vindex UTIME_NULL @vindex FUNC_UTIME_NULL @code{AC_FUNC_UTIME_NULL} @item AC_STRCOLL @vindex STRCOLL @vindex FUNC_STRCOLL @code{AC_FUNC_STRCOLL} @item AC_SETVBUF_REVERSED @vindex SETVBUF_REVERSED @vindex FUNC_SETVBUF_REVERSED @code{AC_FUNC_SETVBUF_REVERSED} @item AC_TIME_WITH_SYS_TIME @vindex TIME_WITH_SYS_TIME @vindex HEADER_TIME @code{AC_HEADER_TIME} @item AC_TIMEZONE @vindex TIMEZONE @vindex STRUCT_TIMEZONE @code{AC_STRUCT_TIMEZONE} @item AC_ST_BLOCKS @vindex ST_BLOCKS @vindex STRUCT_ST_BLOCKS @code{AC_STRUCT_ST_BLOCKS} @item AC_ST_BLKSIZE @vindex ST_BLKSIZE @vindex STRUCT_ST_BLKSIZE @code{AC_STRUCT_ST_BLKSIZE} @item AC_ST_RDEV @vindex ST_RDEV @vindex STRUCT_ST_RDEV @code{AC_STRUCT_ST_RDEV} @item AC_CROSS_CHECK @vindex CROSS_CHECK @vindex TRY_CROSS @code{AC_TRY_CROSS} @item AC_CHAR_UNSIGNED @vindex CHAR_UNSIGNED @vindex C_CHAR_UNSIGNED @code{AC_C_CHAR_UNSIGNED} @item AC_LONG_DOUBLE @vindex LONG_DOUBLE @vindex C_LONG_DOUBLE @code{AC_C_LONG_DOUBLE} @item AC_WORDS_BIGENDIAN @vindex WORDS_BIGENDIAN @vindex C_BIGENDIAN @code{AC_C_BIGENDIAN} @item AC_ARG_ARRAY @vindex ARG_ARRAY @vindex C_ARG_ARRAY @code{AC_C_ARG_ARRAY} @item AC_INLINE @vindex INLINE @vindex C_INLINE @code{AC_C_INLINE} @item AC_CONST @vindex CONST @vindex C_CONST @code{AC_C_CONST} @item AC_REMOTE_TAPE @vindex REMOTE_TAPE @vindex SYS_REMOTE_TAPE @code{AC_SYS_REMOTE_TAPE} @item AC_LONG_FILE_NAMES @vindex LONG_FILE_NAMES @vindex SYS_LONG_FILE_NAMES @code{AC_SYS_LONG_FILE_NAMES} @item AC_RESTARTABLE_SYSCALLS @vindex RESTARTABLE_SYSCALLS @vindex SYS_RESTARTABLE_SYSCALLS @code{AC_SYS_RESTARTABLE_SYSCALLS} @item AC_FIND_X @vindex FIND_X @vindex PATH_X @code{AC_PATH_X} @item AC_FIND_X_XMKMF @vindex FIND_X_XMKMF @vindex PATH_X_XMKMF @code{AC_PATH_X_XMKMF} @item AC_FIND_X_DIRECT @vindex FIND_X_DIRECT @vindex PATH_X_DIRECT @code{AC_PATH_X_DIRECT} @item AC_FIND_XTRA @vindex FIND_XTRA @vindex PATH_XTRA @code{AC_PATH_XTRA} @item AC_AIX @vindex AIX @vindex OS_AIX @code{AC_OS_AIX} @item AC_MINIX @vindex MINIX @vindex OS_MINIX @code{AC_OS_MINIX} @item AC_ISC_POSIX @vindex ISC_POSIX @vindex OS_ISC @code{AC_OS_ISC} @item AC_XENIX_DIR @vindex XENIX_DIR @vindex OS_XENIX @code{AC_OS_XENIX} @item AC_SCO_INTL @vindex SCO_INTL @vindex OS_SCO @code{AC_OS_SCO} @item AC_IRIX_SUN @vindex IRIX_SUN @vindex OS_IRIX @code{AC_OS_IRIX} @item AC_DYNIX_SEQ @vindex DYNIX_SEQ @vindex OS_DYNIX @code{AC_OS_DYNIX} @end table @node Example, Preprocessor Symbol Index, Old Macro Names, Top @chapter An Example Here are sample @file{configure.in} and @file{Makefile.in} files, to give a real illustration of using Autoconf. They are from the GNU @code{cpio} package, which also includes the @code{mt} and @code{rmt} programs. This package does not use a configuration header file; it passes @samp{-D} options to the C compiler on the command line. @menu * Sample configure.in:: An example of a @file{configure} template. * Sample Makefile.in:: An example of a @file{Makefile} template. @end menu @node Sample configure.in, Sample Makefile.in, , Example @section Sample @file{configure.in} @noindent Here is @file{configure.in} from GNU @code{cpio}. The @code{dnl} macro after @code{AC_SUBST} is suppresses an extra (though harmless) newline in the generated @code{configure} script (because the @code{AC_SUBST} macro does not produce any output where it is called). @example dnl Process this file with autoconf to produce a configure script. AC_INIT(cpio.h) PROGS="cpio" AC_SUBST(PROGS)dnl AC_PROG_CC AC_PROG_CPP AC_PROG_GCC_TRADITIONAL AC_PROG_INSTALL AC_OS_AIX AC_OS_MINIX AC_OS_ISC AC_TYPE_SIGNAL AC_HEADER_MAJOR AC_SYS_REMOTE_TAPE test -n "$have_mtio" && PROGS="$PROGS mt" AC_PROG_RSH AC_C_CONST AC_TYPE_UID_T AC_HEADER_STDC AC_CHECK_HEADERS(string.h fcntl.h utime.h unistd.h sys/io/trioctl.h) AC_REPLACE_FUNCS(fnmatch bcopy mkdir strdup) AC_CHECK_FUNCS(strerror lchown) AC_FUNC_VPRINTF AC_FUNC_ALLOCA AC_OS_XENIX AC_CHECK_LIB(socket, [LIBS="$LIBS -lsocket"]) AC_CHECK_LIB(nsl, [LIBS="$LIBS -lnsl"]) AC_OUTPUT(Makefile) @end example @node Sample Makefile.in, , Sample configure.in, Example @section Sample @file{Makefile.in} @noindent Here is @file{Makefile.in} from GNU @code{cpio}, with some irrelevant lines omitted, for brevity. @example srcdir = @@srcdir@@ VPATH = @@srcdir@@ CC = @@CC@@ INSTALL = @@INSTALL@@ INSTALL_PROGRAM = @@INSTALL_PROGRAM@@ INSTALL_DATA = @@INSTALL_DATA@@ DEFS = @@DEFS@@ LIBS = @@LIBS@@ RTAPELIB = @@RTAPELIB@@ CFLAGS = -g LDFLAGS = -g prefix = /usr/local exec_prefix = $(prefix) binprefix = manprefix = bindir = $(exec_prefix)/bin libdir = $(exec_prefix)/lib mandir = $(prefix)/man/man1 manext = 1 SHELL = /bin/sh SRCS = copyin.c copyout.c copypass.c defer.c dstring.c global.c \ main.c tar.c util.c error.c getopt.c getopt1.c filemode.c version.c \ rtapelib.c dirname.c idcache.c makepath.c xmalloc.c stripslash.c \ userspec.c xstrdup.c bcopy.c fnmatch.c mkdir.c strdup.c OBJS = copyin.o copyout.o copypass.o defer.o dstring.o global.o \ main.o tar.o util.o error.o getopt.o getopt1.o filemode.o version.o \ $(RTAPELIB) dirname.o idcache.o makepath.o xmalloc.o stripslash.o \ userspec.o xstrdup.o @@LIBOBJS@@ @@ALLOCA@@ # mt source files not shared with cpio. MT_SRCS = mt.c argmatch.c MT_OBJS = mt.o argmatch.o error.o getopt.o getopt1.o \ xmalloc.o version.o $(RTAPELIB) @@ALLOCA@@ HDRS = cpio.h cpiohdr.h tar.h tarhdr.h defer.h dstring.h extern.h filetypes.h \ system.h fnmatch.h getopt.h rmt.h DISTFILES = $(SRCS) $(HDRS) COPYING COPYING.LIB ChangeLog Makefile.in \ README NEWS INSTALL cpio.1 mt.1 makefile.pc makefile.os2 cpio.def \ configure configure.in mkinstalldirs $(MT_SRCS) rmt.c tcexparg.c alloca.c all: @@PROGS@@ .c.o: $(CC) -c $(CPPFLAGS) $(DEFS) -I$(srcdir) $(CFLAGS) $< install: installdirs all $(srcdir)/cpio.1 $(srcdir)/mt.1 $(INSTALL_PROGRAM) cpio $(bindir)/$(binprefix)cpio test ! -f mt || $(INSTALL_PROGRAM) mt $(bindir)/$(binprefix)mt -test ! -f rmt || $(INSTALL_PROGRAM) rmt $(libdir)/rmt $(INSTALL_DATA) $(srcdir)/cpio.1 $(mandir)/$(manprefix)cpio.$(manext) test ! -f mt || \ $(INSTALL_DATA) $(srcdir)/mt.1 $(mandir)/$(manprefix)mt.$(manext) installdirs: $(srcdir)/mkinstalldirs $(bindir) $(libdir) $(mandir) uninstall: cd $(bindir); rm -f $(binprefix)cpio $(binprefix)mt -rm -f $(libdir)/rmt cd $(mandir); rm -f $(manprefix)cpio.$(manext) $(manprefix)mt.$(manext) check: @@echo No tests are supplied. cpio: $(OBJS) $(CC) $(LDFLAGS) -o $@@ $(OBJS) $(LIBS) rmt: rmt.o $(CC) $(LDFLAGS) -o $@@ rmt.o $(LIBS) mt: $(MT_OBJS) $(CC) $(LDFLAGS) -o $@@ $(MT_OBJS) $(LIBS) Makefile: Makefile.in config.status $(SHELL) config.status config.status: configure $(SHELL) config.status --recheck configure: configure.in cd $(srcdir); autoconf TAGS: $(SRCS) etags $(SRCS) clean: rm -f cpio rmt mt *.o core mostlyclean: clean distclean: clean rm -f Makefile config.status realclean: distclean rm -f TAGS dist: $(DISTFILES) echo cpio-`sed -e '/version_string/!d' \ -e 's/[^0-9.]*\([0-9.]*\).*/\1/' -e q version.c` > .fname rm -rf `cat .fname` mkdir `cat .fname` -ln $(DISTFILES) `cat .fname` for file in $(DISTFILES); do \ test -r `cat .fname`/$$file || cp -p $$file `cat .fname`; \ done tar chzf `cat .fname`.tar.gz `cat .fname` rm -rf `cat .fname` .fname @end example @node Preprocessor Symbol Index, Macro Index, Example, Top @unnumbered Preprocessor Symbol Index This is an alphabetical list of the C preprocessor symbols that the Autoconf macros define. To work with Autoconf, C source code needs to use these names in @code{#if} directives. @printindex vr @node Macro Index, , Preprocessor Symbol Index, Top @unnumbered Macro Index This is an alphabetical list of the Autoconf macros. To make the list easier to use, the macros are listed without their preceding @samp{AC_}. @printindex ma @contents @bye @c Local variables: @c compile-command: "makeinfo autoconf.texi" @c End: