Making configure Scripts

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3 Making `configure` Scripts

The configuration scripts that Autoconf produces are by convention called configure. When run, configure creates several files, replacing configuration parameters in them with appropriate values. The files that configure creates are:

one or more Makefile files, usually one in each subdirectory of the package (see Makefile Substitutions);
optionally, a C header file, the name of which is configurable, containing #define directives (see Configuration Headers);
a shell script called config.status that, when run, recreates the files listed above (see config.status Invocation);
an optional shell script normally called config.cache (created when using ‘configure --config-cache’) that saves the results of running many of the tests (see Cache Files);
a file called config.log containing any messages produced by compilers, to help debugging if configure makes a mistake.

To create a configure script with Autoconf, you need to write an Autoconf input file configure.ac (or configure.in) and run autoconf on it. If you write your own feature tests to supplement those that come with Autoconf, you might also write files called aclocal.m4 and acsite.m4. If you use a C header file to contain #define directives, you might also run autoheader, and you can distribute the generated 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 ‘*’. Optional files are enclosed in square brackets (‘[]’). autoconf and autoheader also read the installed Autoconf macro files (by reading autoconf.m4).

Files used in preparing a software package for distribution, when using just Autoconf:

     your source files --> [autoscan*] --> [configure.scan] --> configure.ac
     
     configure.ac --.
                    |   .------> autoconf* -----> configure
     [aclocal.m4] --+---+
                    |   `-----> [autoheader*] --> [config.h.in]
     [acsite.m4] ---'
     
     Makefile.in

Additionally, if you use Automake, the following additional productions come into play:

     [acinclude.m4] --.
                      |
     [local macros] --+--> aclocal* --> aclocal.m4
                      |
     configure.ac ----'
     
     configure.ac --.
                    +--> automake* --> Makefile.in
     Makefile.am ---'

Files used in configuring a software package:

                            .-------------> [config.cache]
     configure* ------------+-------------> config.log
                            |
     [config.h.in] -.       v            .-> [config.h] -.
                    +--> config.status* -+               +--> make*
     Makefile.in ---'                    `-> Makefile ---'

3 Making configure Scripts

3 Making `configure` Scripts