GCC 4.2 branch comparision failure building Java

[Joe Buck]

On Thu, Mar 15, 2007 at 05:30:48PM -0700, Mark Mitchell wrote:
> Joe Buck wrote:
> 
> >> For what it's worth, I bootstrapped on a few different GNU/Linux
> >> systems with different kernels and base compilers.  I only saw
> >> bootstrap comparison failures on one; that one was running Red Hat 9
> >> and had gcc 3.2.2 installed in /usr/bin.  On that one, a bootstrap4
> >> worked.  So I assumed that that one was due to some miscompilation of
> >> stage1.
> > 
> > Yes, this has been reported before (I've also seen bootstrap failures
> > when using Red Hat's version 3.2.3 on an x86 RHEL3 box).
> 
> I do indeed generally build GCC releases on an RHEL3 box.  However, I
> believe that I was using a version of GCC 3.4.x (built by CodeSourcery)
> as the bootstrap compiler.  It does seem like a suspiciously similar
> situation, though; I'm sure that Joseph will be able to tell us if the
> problem is reproducible with GCC 3.4.x.

The problem does not happen with 3.4.x at least for x==2.  I regularly use
gcc 3.4.2 as the bootstrap compiler for my gcc testing.  Here's last
night's run for the 4.2 branch:

http://gcc.gnu.org/ml/gcc-testresults/2007-03/msg00710.html

At one point I considered trying a search to see which files get
miscompiled, by combining stage1 object files from a run with 3.2.3 and
3.4.2 and trying to do the rest of the bootstrap with that, then varying
which .o files come from which compilers.  But then I got much busier and
lost the motivation.