[Bug libfortran/54097] New: configure: error: GNU Fortran is not working (CPU you selected does not support x86-64 instruction set)

[pentium4borg at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54097

             Bug #: 54097
           Summary: configure: error: GNU Fortran is not working (CPU you
                    selected does not support x86-64 instruction set)
    Classification: Unclassified
           Product: gcc
           Version: 4.5.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: pentium4b...@gmail.com


Created attachment 27875
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27875
config.log

I'm trying to build a 64-bit gcc-4.3.2-r2 in a 32-bit crossdev environment on
Gentoo. The CPU and host system are 64-bit. The root Gentoo system is itself a
32-bit chroot, and within this chroot I am trying to cross-compile a 64-bit
environment from the 32-bit system. This has worked many times in the past, but
gcc is now is failing to build.

When configure for libgfortran runs, it fails with the following:


configure:14588: checking whether the GNU Fortran compiler is working
configure:14601:
/var/tmp/portage/cross-x86_64-pc-linux-gnu/gcc-4.5.3-r2/work/build/./gcc/gfortran
-B/var/tmp/portage/cross-x86_64-pc-linux-gnu/gcc-4.5.3-r2/work/build/./gcc/
-B/usr/x86_64-pc-linux-gnu/bin/ -B/usr/x86_64-pc-linux-gnu/lib/ -isystem
/usr/x86_64-pc-linux-gnu/include -isystem /usr/x86_64-pc-linux-gnu/sys-include 
  -c -O2 -march=i686 -pipe  conftest.f >&5
f951: error: CPU you selected does not support x86-64 instruction set          
                                                                               
                                                                             
configure:14601: $? = 1
configure: failed program was:                                                 
                                                                               
                                                                              |
                                                                               
                                                                               
                                                                            |  
    program foo                                                                
                                                                               
                                                                          |    
  real, parameter :: bar = sin (12.34 / 2.5)
|       end program foo                                                        
                                                                               
                                                                             
configure:14605: result: no                                                    
                                                                               
                                                                             
configure:14607: error: GNU Fortran is not working; please report a bug in
http://gcc.gnu.org/bugzilla, attaching
/var/tmp/portage/cross-x86_64-pc-linux-gnu/gcc-4.5.3-r2/work/build/x86_64-pc-linux-gnu/libgfortran/config.log


If I copy the command and test program, and run it with -m32, that test program
compiles fine. Since the target arch is i686, why does the compiler have to
deliberately be told to generate 32-bit code? Is there a fix for gcc's
configure or Makefiles?

(Full config.log is attached.)

Thanks!