https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |rguenth at gcc dot gnu.org
--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
Note that when a shared library wants -ffast-math like behavior (FTZ, etc.)
_not_ linking crtfastmath.o will cause its behavior to depend on the process
loading
it and whether that sets the appropriate flags or not. That might also cause
highly surprising effects.
That said, a "true fix" would redesign how these things work and make
FTZ part of the instruction encoding.
I suppose setting/restoring the control word around all public API of a
translation unit (and with LTO a bit more optimized) would be prohibitly
expensive.
Short of dropping the feature or re-implementing it, for example in the
dynamic loader via some ELF annotations with documented behavior on
"mismatch", I don't see any fix for this bug besides asking users to
conciously not link with -ffast-math when building shared libraries - unless
that's intended.
