[Bug target/55522] -funsafe-math-optimizations is unexpectedly harmful, especially w/ -shared

[spathiwa at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522

--- Comment #7 from Craig Smith <spathiwa at gmail dot com> ---
(In reply to Orion Poplawski from comment #6)
> (In reply to Craig Smith from comment #5)
> > For example, on RHEL 7, liblzma.so.5 is linked with -Ofast, which also
> > triggers crtfastmath.o to be used, corrupting the mxcsr register at library
> > load time.
> > (The bug might be specific to RedHat, because -Ofast is added in the rpm
> > spec.)
> 
> I don't see any evidence of liblzma.so.5 being linked with -Ofast on RHEL7,
> can you point to that?

The xz.spec file from the xz-5.1.2-0.alpha.1 source RPM includes the following:

%build
export CONFIGURE_TOP=`pwd`
mkdir objs
pushd objs
CFLAGS="%{optflags} -Ofast -funroll-loops" \
%configure2_5x
%make
popd