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Date: Sat, 26 May 2007 18:57:31 -0400
From: Kris Kennaway <kris@obsecurity.org>
To: Steve Kargl <sgk@troutmask.apl.washington.edu>
Message-ID: <20070526225731.GA56181@xor.obsecurity.org>
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Cc: freebsd-current@freebsd.org, Ed Schouten <ed@fxq.nl>
Subject: Re: HEADS-UP: gcc-4.2 import appears to miscompile libm.
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On Sat, May 26, 2007 at 03:40:40PM -0700, Steve Kargl wrote:
> On Sat, May 26, 2007 at 11:48:35PM +0200, Ed Schouten wrote:
> > Hello Steve,
> > 
> > * Steve Kargl <sgk@troutmask.apl.washington.edu> wrote:
> > > mobile:kargl[234] cat a.c
> > > #include <stdio.h>
> > > #include <math.h>
> > > 
> > > int main (void) {
> > >    int n;
> > >    float a;
> > >    a = 1.f;
> > >    printf("%f\n", frexpf(a,&n));
> > >    return 0;
> > > }
> > > mobile:kargl[235] cc -o z a.c -lm
> > > mobile:kargl[236] ./z
> > > 1.000000
> > > mobile:kargl[237] cc --version
> > > cc (GCC) 4.2.0 20070514 [FreeBSD]
> > > Copyright (C) 2007 Free Software Foundation, Inc.
> > > This is free software; see the source for copying conditions.  There is NO
> > > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > > 
> > > frexpf() should return a value in [1/2,1).
> > 
> > In a different thread (about snd_emu10k1) a user noticed that -ftree-vrp
> > (part of -O2) may cause miscompilations. Could you try installing a libm
> > (src/lib/msun) that is compiled with -O1?
> > 
> 
> (cc'd -current list)
> 
> Using -O instead of -O2 indeed appears to fix the problem.

How about -O2 -fno-tree-vrp?

Kris