Bug 434414 – sys-devel/llvm-3.1-r2[gold] and sys-devel/clang-3.1-r5 do not run with -flto

• Product: Gentoo Linux
• Status: RESOLVED INVALID

[Description Martin Väth 2012-09-09 09:40:53 UTC]

clang -flto
(tested with sys-devel/llvm-3.1-r2[gold] and sys-devel/clang-3.1-r5)
does not work in gentoo for at least two reasons, one I could identify:

1. The gold plugin will not load if built with the injected --as-needed:
Although it seems that there was an attempt to fix this upstream,
also Ubuntu needed additional patches:
https://bugs.launchpad.net/ubuntu/+source/llvm-3.0/+bug/1026359

For testing, I just exported LD_AS_NEEDED="" when emerging llvm.
Then the linker plugin can be loaded, but there occurs another problem:

2. When actually linking with clang++ -flo,
there occur errors with all .o files:
....o: file not recognized: File format not recognized

No idea yet what is involved for 2; perhaps this is a different issue
(or perhaps not if LD_AS_NEEDED= was just too aggressive;
I did not play with the ubuntu patches yet).

[Comment 1 Michał Górny 2012-09-09 17:39:07 UTC]

Sorry for asking the stupid question but have you enabled gold as default linker? I mean made ld symlink point to ld.gold.

[Comment 2 Martin Väth 2012-09-10 06:40:06 UTC]

(In reply to comment #1)
> Sorry for asking the stupid question

PEBKAC: Switched between bfd and gold so many times (playing with LD=ld.gold
etc) that I did not realize that finally I used the wrong linker.

Strange that "LD_AS_NEEDED= emerge -1 llvm" changed the behavior with
bfd linker, but of course not a bug.

No problems with reemerged llvm and gold linker. Sorry for the noise.