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Re: [toplevel] GCC_NO_EXECUTABLES


On Fri, Nov 26, 2004 at 04:34:02PM +0100, Andreas Schwab wrote:
> Daniel Jacobowitz <drow@mvista.com> writes:
> 
> > dnl This is a shame.  We have to provide a default for some link tests,
> > dnl similar to the default for run tests.
> > m4_define([AC_FUNC_MMAP],
> > if test x$gcc_no_link = xyes; then
> >   if test "x${ac_cv_func_mmap_fixed_mapped+set}" != xset; then
> >     ac_cv_func_mmap_fixed_mapped=no
> >   fi
> > fi
> > if test "x${ac_cv_func_mmap_fixed_mapped+set}" != xset; then
> >   m4_defn([AC_FUNC_MMAP])
> > fi)
> 
> For what is this needed?  It breaks configure in libgfortran.  In general
> it is a bad idea to put such a macro in a shell conditional because it
> breaks AC_REQUIRE.  In the case of libgfortran this is the first macro
> that triggers inclusion of the general C language setup (things like
> AC_PROC_CPP, etc), which will not be executed at all when
> ac_cv_func_mmap_fixed_mapped is set.  It also excludes a few test for
> headers that libgfortran is depending upon, although the latter is
> arguably a bug in the libgfortran configure script in that it should
> explicitly test for them.

I assume that libiberty couldn't build without this in some
configurations.  I don't know exactly which anymore.  It didn't go in to
CVS autoconf when I updated their implementation of AC_NO_EXECUTABLES;
it's possible we could do without it now by some other change to
libiberty.

The problem probably arises because we AC_REQUIRE AC_FUNC_MMAP from
libiberty_AC_FUNC_STRNCMP, which is used unconditionally.  If
GCC_NO_EXECUTABLES is in effect, we must suppress this somehow.  I
think that doing it in libiberty's configure didn't work because of the
semantics of AC_REQUIRE.

I can only suggest you play around with it...

-- 
Daniel Jacobowitz


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