configure is designed so that it appears to do everything itself, but there is actually a hidden slave: config.status. configure is in charge of examining your system, but it is config.status that actually takes the proper actions based on the results of configure. The most typical task of config.status is to instantiate files.
This section describes the common behavior of the four standard
AC_CONFIG_LINKS. They all
have this prototype:
AC_CONFIG_ITEMS(tag..., [commands], [init-cmds])
where the arguments are:
You are encouraged to use literals as tags. In particular, you should avoid
... && my_foos="$my_foos fooo" ... && my_foos="$my_foos foooo" AC_CONFIG_ITEMS([$my_foos])
and use this instead:
... && AC_CONFIG_ITEMS([fooo]) ... && AC_CONFIG_ITEMS([foooo])
special tag values: they may have the form ‘output’ or
‘output:inputs’. The file output is instantiated
from its templates, inputs (defaulting to ‘output.in’).
‘AC_CONFIG_FILES([Makefile:boiler/top.mk:boiler/bot.mk])’, for example, asks for the creation of the file Makefile that contains the expansion of the output variables in the concatenation of boiler/top.mk and boiler/bot.mk.
The special value ‘-’ might be used to denote the standard output when used in output, or the standard input when used in the inputs. You most probably don't need to use this in configure.ac, but it is convenient when using the command line interface of ./config.status, see config.status Invocation, for more details.
The inputs may be absolute or relative file names. In the latter
case they are first looked for in the build tree, and then in the source
tree. Input files should be text files, and a line length below 2000
bytes should be safe.
The variables set during the execution of configure are not available here: you first need to set them via the init-cmds. Nonetheless the following variables are precomputed:
The current directory refers to the directory (or pseudo-directory) containing the input part of tags. For instance, running
AC_CONFIG_COMMANDS([deep/dir/out:in/in.in], [...], [...])
with --srcdir=../package produces the following values:
# Argument of --srcdir srcdir='../package' # Reversing deep/dir ac_top_build_prefix='../../' # Concatenation of $ac_top_build_prefix and srcdir ac_top_srcdir='../../../package' # Concatenation of $ac_top_srcdir and deep/dir ac_srcdir='../../../package/deep/dir'
independently of ‘in/in.in’.
var. init-cmds is typically used by configure to give config.status some variables it needs to run the commands.
You should be extremely cautious in your variable names: all the init-cmds share the same name space and may overwrite each other in unpredictable ways. Sorry...
All these macros can be called multiple times, with different tag values, of course!