Code compiled with -Ofast fails to find math symbols. (eg `__expf_finite')

[XapaJIaMnu]

Bugzilla Link	45034
Resolution	FIXED
Resolved on	Feb 28, 2020 07:02
Version	9.0
OS	Linux
Blocks	#43900
Attachments	simple testcase.
CC	@DougGregor,@efriedma-quic,@zmodem,@zygoloid,@serge-sans-paille,@tstellar
Fixed by commit(s)	6d15c4d

Extended Description

Hey,

After some recent changes, various projects fail to compile with clang when using -Ofast ( or -O2 -ffast-math ). Example bugs from the web:

cms-sw/cmssw#24935
dpiparo/vdt#11

https://bugs.archlinux.org/task/65541

I have attached a sample file that triggers the bug, taken from the Arch bugtracker:

clang++ bug.cpp works
clang++ bug.cpp -Ofast fails with:

/usr/bin/ld: /tmp/bug-6a1f7c.o: in function main': bug.cpp:(.text+0xd): undefined reference to __expf_finite'
clang-9: error: linker command failed with exit code 1 (use -v to see invocation)

According to the arch user, this is likely related to https://reviews.llvm.org/D74712

Cheers,

Nick

[efriedma-quic]

Yes, probably the same thing.

If it's starting to break code already, probably should be a release blocker.

[zmodem]

Since it's not really an llvm regression, but a glibc change, I'm not sure I want to block on this. It may have to wait until 10.0.1...

[serge-sans-paille]

https://reviews.llvm.org/D74712 fixes the issue.

[serge-sans-paille]

Fixed by 6d15c4d

[zmodem]

Fixed by 6d15c4d

And pushed to 10.x as cd0926d. Please let me know if there are any follow-ups.

[XapaJIaMnu]

Fixed by 6d15c4d

And pushed to 10.x as cd0926d. Please let
me know if there are any follow-ups.

Is this going to be backported to the older point releases?

Cheers,

Nick

[zmodem]

Fixed by 6d15c4d

And pushed to 10.x as cd0926d. Please let
me know if there are any follow-ups.

Is this going to be backported to the older point releases?

That's a question for Tom if he wants to consider it, but in general I don't think there are any more point releases planned for 9.x and before.

[tstellar]

Fixed by 6d15c4d

And pushed to 10.x as cd0926d. Please let
me know if there are any follow-ups.

Is this going to be backported to the older point releases?

No, we aren't planning any more 9.x releases.

-Tom

Cheers,

Nick