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From: Eric Sunshine
Subject: AC_CONFIG_COMMANDS problem
Date: Fri, 27 Dec 2002 05:42:05 -0500


In Autoconf 2.57 and in the CVS version, there is a problem with  
AC_CONFIG_COMMANDS when it is used to create a file in a directory which does  
not already exist at the time config.status is run.  Consider the following  

AC_INIT([myprog], [0])
AC_CONFIG_COMMANDS([foo/bar], [echo "test" > foo/bar])

This results in a config.status which produces these error messages:

configure: creating ./config.status
./config.status: line 1: cd: foo: No such file or directory
./config.status: line 1: cd: foo: No such file or directory
./config.status: line 1: cd: foo: No such file or directory
./config.status: line 1: cd: foo: No such file or directory
config.status: executing foo/bar commands

These errors are caused by the following commands in config.status which are  
executed right before the "foo/bar" target is invoked:

ac_abs_builddir=`cd "$ac_dir" && cd $ac_builddir && pwd`
ac_abs_top_builddir=`cd "$ac_dir" && cd ${ac_top_builddir}. && pwd`
ac_abs_srcdir=`cd "$ac_dir" && cd $ac_srcdir && pwd`
ac_abs_top_srcdir=`cd "$ac_dir" && cd $ac_top_srcdir && pwd`

The problem is that these commands are trying to change to the non-existent  
"foo" directory.

This raises the question of whether AC_CONFIG_COMMANDS should be be  
responsible for creating the "foo" directory itself before running the  
target's commands.  Considering that AC_CONFIG_COMMANDS is intended to be  
generic (that is, the target does not necessarily have to represent a file),  
then one can successfully argue that AC_CONFIG_COMMANDS should _not_ create  
the "foo" directory.  This leads to the obvious answer that the target should  
itself be responsible for creating its own directory if necessary.  Thus, a  
re-written configure.ac which creates its own output directory would appear  
as follows:

AC_INIT([myprog], [0])
AC_CONFIG_COMMANDS([foo/bar], [AS_MKDIR_P([foo])
    echo "test" > foo/bar])

Unfortunately, this version _also_ fails with the exact same error messages.  
 The reason it fails is because config.status still attempts to compute  
ac_abs_builddir, ac_abs_top_builddir, ac_abs_srcdir, and ac_abs_top_srcdir  
_before_ the target's commands have been invoked (before `mkdir' is issued),  
thus the problem is not solved.

One hack to work around this problem is to move the `mkdir' to  
AC_CONFIG_COMMANDS's "init-cmds", as follows:

AC_INIT([myprog], [0])
    [echo "test" > foo/bar],

Unfortunately, this solution is incorrect because it causes "foo" to be  
created when _any_ config.status target is invoked, even though "foo" should  
only be created when the "foo/bar" target is invoked.

-- ES

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