ax_expand_prefix

when $prefix and $exec_prefix are still set to NONE then set them to the usual default values - being based on $ac_default_prefix.
- this macro can be AC_REQUIREd by other macros that need to
compute values for installation directories. It has been observed that it was done wrong over and over again, so this is a bit more safe to do.

remember - setting exec_prefix='${prefix}' needs you interpolate directories multiple times, it is not sufficient to just say MYVAR="${datadir}/putter" but you do have to run `eval` a few times, sth. like MYVAR=`eval "echo \"$MYVAR\""` done atleast two times.

The implementation of this macro simply picks up the lines that would be run at the start of AC_OUTPUT anyway to set the prefix/exec_prefix defaults. Between AC_INIT and the first command to AC_REQUIRE this macro you can set the two variables to something explicit instead. Probably, any command to compute installation directories should be run _after_ AM_INIT_AUTOMAKE

@: guidod@gmx.de @$Id: ax_expand_prefix.m4,v 1.1 2003/10/19 00:05:18 guidod Exp $

AC_DEFUN([AX_EXPAND_PREFIX],[dnl
  # The prefix default can be set in configure.ac (otherwise it is /usr/local)
  test "x$prefix" = xNONE && prefix=$ac_default_prefix
  # Let make expand exec_prefix. Allows to override the makevar 'prefix' later
  test "x$exec_prefix" = xNONE && exec_prefix='${prefix}'
])