Re: expand-before-require bug

[Bruno Haible]

Hi Eric,

[CCing bug-autoconf. This is a reply to
 <http://lists.gnu.org/archive/html/bug-gnulib/2009-01/msg00247.html>]

> * gnulib-tool (func_dest_tmpfilename, func_create_testdir): Using
> obsolete AC_GNU_SOURCE causes out-of-order expansion; avoid it,
> and rely solely on gl_USE_SYSTEM_EXTENSIONS.

When you are applying such a patch to gnulib, I think you should also
deprecate AC_GNU_SOURCE in autoconf.

Why? Currently autoconf documents AC_GNU_SOURCE as
   "This macro is a platform-specific subset of
    @code{AC_USE_SYSTEM_EXTENSIONS} (@pxref{AC_USE_SYSTEM_EXTENSIONS})."
If a user needs only AC_GNU_SOURCE, because of a problem only present in the
glibc header files, according to this documentation AC_GNU_SOURCE is his
primary choice. But what you discovered is that AC_GNU_SOURCE and
AC_USE_SYSTEM_EXTENSIONS don't play well together with each other.

Or otherwise, you can fix the conflict between AC_GNU_SOURCE and
AC_USE_SYSTEM_EXTENSIONS differently, and then undo the gnulib change.

Bruno