Disable -Woverflow errors for i386 for GCC 9.
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Authored by jhb on Aug 26 2020, 6:45 PM.

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rG5cf638d0049e: Disable -Woverflow errors for i386 for GCC 9.
rG93d6fa53c995: Disable -Woverflow errors for i386 for GCC 9.

Summary

GCC 9 warns about floating point constants overflowing for i386.

Test Plan

build i386 and amd64 with gcc9

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rG FreeBSD src repository

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Event Timeline

jhb created this revision.Aug 26 2020, 6:45 PM

Herald added a subscriber: bdrewery. · View Herald TranscriptAug 26 2020, 6:45 PM

jhb requested review of this revision.Aug 26 2020, 6:45 PM

Harbormaster completed remote builds in B33177: Diff 76257.Aug 26 2020, 6:45 PM

Fine with me

This revision is now accepted and ready to land.Aug 26 2020, 7:34 PM

jhb added a child revision: D26202: Switch to GCC 9 for the GCC tinderbox..Aug 26 2020, 7:46 PM

There is a larger issue here that GCC has special features in place to deal with the unusual floating point setup FreeBSD/i386 uses. That is what triggers these warnings. clang treats FreeBSD/i386 like Linux i386 and assumes we use the same floating point setup as Linux. Probably we should really change FreeBSD to be more standard to match what clang assumes and let GCC drop patches that are only used on FreeBSD (AFAICT). It would also remove the need for the hack to not install GCC's float.h for amd64 and i386.

Is there a canonical reference for these differences?

Is this specifically for LDBL_MAX?

When I looked at something like this last (around r323003), gcc wasn't just producing a warning, it was also producing wrong code (an infinite value instead of a finite one).

Going to a more sane long double for i386 would be great, but might have some ABI/upgrade consequences.

jhb retitled this revision from Disabling -Woverflow errors for i386 for GCC 9. to Disable -Woverflow errors for i386 for GCC 9..Sep 13 2021, 3:50 PM

Closed by commit rG93d6fa53c995: Disable -Woverflow errors for i386 for GCC 9. (authored by jhb). · Explain WhySep 13 2021, 6:02 PM

This revision was automatically updated to reflect the committed changes.

jhb added a commit: rG93d6fa53c995: Disable -Woverflow errors for i386 for GCC 9..

jhb added a commit: rG5cf638d0049e: Disable -Woverflow errors for i386 for GCC 9..May 10 2022, 11:24 PM

Herald added a subscriber: imp. · View Herald TranscriptMay 10 2022, 11:24 PM