[Bug libf2c/12897] New: g77 datan2 hangs with -m64 flag on Opteron (specific case)

["etc231etc231 at willus dot com" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12897

           Summary: g77 datan2 hangs with -m64 flag on Opteron (specific
                    case)
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libf2c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: etc231etc231 at willus dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: Same
  GCC host triplet: Dual 1.8 GHz Opteron running SuSE Linux 2.4.19-SMP
                    x86_64
GCC target triplet: Same

The code below hangs when compiled on the above specified host with this command:

    g77 -m64 -o test test.f

I don't know if it's the atan2 function or the nature of the 64-bit compile, but
the same code does NOT hang when compiled with the -m32 flag:

    g77 -m32 -o test test.f

The atan2 function doesn't hang all the time--just for this specific input. 
Lucky me for finding it!

-Willus

      program test
      real*8 x,y
      x = -0.01792735857538728036d0
      y = -0.00756827042671106339d0
      write(*,*) 'Starting program...'
      write(*,*) 'datan2(y,x) = ',datan2(y,x)
      end