@node ax_expand_prefix
@unnumberedsec ax_expand_prefix

@majorheading Synopsis

@smallexample
AX_EXPAND_PREFIX
@end smallexample

@majorheading Description

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 at least 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

@majorheading Source Code

Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_expand_prefix.m4,latest
version of @file{ax_expand_prefix.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_expand_prefix.m4,the
macro's revision history}.

@majorheading License

@w{Copyright @copyright{} 2008 Guido U. Draheim @email{guidod@@gmx.de}}

Copying and distribution of this file, with or without modification, are
permitted in any medium without royalty provided the copyright notice
and this notice are preserved.  This file is offered as-is, without any
warranty.