[PATCH] fix bug in autoconf-2.13 that keeps cross gcc from buildingon cygwin

Earnie Boyd earnie_boyd@yahoo.com
Mon Aug 26 13:57:00 GMT 2002

I suggest that this issue be dealt with within the Cygwin distribution of autoconf-2.13.


Dan Kegel wrote:

> [repost -- mail system problems]
> Building cross gcc's on cygwin fails because autoconf 2.13's AC_TRY_COMPILER
> test assumes that it's ok to try to run possibly cross-compiled binaries,
> and that if they run, the compiler must not be a cross-compiler.
> This assumption fails on Cygwin; see
>    http://www.oarcorp.com/rtems/maillistArchives/rtems-users/1999/may/msg00075.html
>    http://gcc.gnu.org/ml/gcc-help/2002-05/msg00165.html
>    http://sources.redhat.com/ml/crossgcc/2002-08/msg00099.html
> The symptom is the build hangs about twenty times waiting for you to click a dialog box,
> and the target directory's ac_cv_prog_cc_cross is improperly set to 'no'.
> The problem will likely go away when gcc moves to using autoconf 2.5x, but
> that may take a while, and won't help people who need to build oldish
> gcc's like 3.0.x.  So it's worth fixing autoconf-2.13 if it's a small, safe fix.
> Fortunately, the fix does look small and safe:
> --- /usr/share/autoconf2.13/acgeneral.m4.orig   Thu Aug 22 18:26:58 2002
> +++ acgeneral.m4        Thu Aug 22 19:03:12 2002
> @@ -1510,11 +1510,13 @@
>    EOF
>    if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext}; then
>      [$2]=yes
> -  # If we can't run a trivial program, we are probably using a cross compiler.
> -  if (./conftest; exit) 2>/dev/null; then
> -    [$3]=no
> -  else
> -    [$3]=yes
> +  if test "$[$3]" != yes; then
> +    # If we can't run a trivial program, we are probably using a cross compiler.
> +    if (./conftest; exit) 2>/dev/null; then
> +      [$3]=no
> +    else
> +      [$3]=yes
> +    fi
>      fi
>    else
>      echo "configure: failed program was:" >&AC_FD_CC
> i.e. after the patch, AC_TRY_COMPILER checks its 3rd parameter,
> and if it's already 'yes', it knows not to run the binaries.
> After applying this patch to autoconf-2.13 and installing,
> you then need to regenerate libiberty/configure,
> gcc/configure and fastjar/configure.  It might be good if future releases
> of gcc that still used autoconf-2.13 were done on machines with an
> autoconf-2.13 with this patch applied.
> This is only a partial fix; it requires the user to override
> ac_cv_prog_cc_cross.  A similar bug in ltconfig can be worked around
> without a patch by overriding cross_compiling=yes in the same way.
> Both overrides should only be done during the build of runtime libraries.
> Fortunately, gcc's makefile has pseudotargets that let you do this.
> For instance:
>       make all-gcc
>       ac_cv_prog_cc_cross=yes cross_compiling=yes make all-target
>       make install
> Users on non-cygwin platforms can ignore this issue, and just do
> 'make install' as usual.  This patch will neither help nor hurt them.
> (Note that overriding ac_cv_prog_cc_cross at make time appears to be sufficient.
> Although it would be more logical to override them when doing initial
> configuration of gcc, that wouldn't let you work around the ltconfig bug.)
> Even if future autoconf and gcc releases don't apply this patch, maybe
> this post will help people who need to build gcc on cygwin.
> - Dan
> http://www.kegel.com

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