autoconf.info: Using System Type

Using the System Type

How do you use a canonical system type?  Usually, you use it in one or
more `case' statements in `configure.ac' to select system-specific C
files.  Then, using `AC_CONFIG_LINKS', link those files which have
names based on the system name, to generic names, such as `host.h' or
`target.c' (*note Configuration Links::).  The `case' statement
patterns can use shell wild cards to group several cases together, like
in this fragment:

     case $target in
     i386-*-mach* | i386-*-gnu*)
                  obj_format=aout emulation=mach bfd_gas=yes ;;
     i960-*-bout) obj_format=bout ;;
     esac

and later in `configure.ac', use:

     AC_CONFIG_LINKS(host.h:config/$machine.h
                     object.h:config/$obj_format.h)

   Note that the above example uses `$target' because it's taken from a
tool which can be built on some architecture (`$build'), run on another
(`$host'), but yet handle data for a third architecture (`$target').
Such tools are usually part of a compiler suite, they generate code for
a specific `$target'.

   However `$target' should be meaningless for most packages.  If you
want to base a decision on the system where your program will be run,
make sure you use the `$host' variable, as in the following excerpt:

     case $host in
       *-*-msdos* | *-*-go32* | *-*-mingw32* | *-*-cygwin* | *-*-windows*)
         MUMBLE_INIT="mumble.ini"
         ;;
       *)
         MUMBLE_INIT=".mumbleinit"
         ;;
     esac
     AC_SUBST([MUMBLE_INIT])

   You can also use the host system type to find cross-compilation
tools.  *Note Generic Programs::, for information about the
`AC_CHECK_TOOL' macro which does that.