Bug 948027 – dev-lang/rust-1.84.0 fails to build with lto+bfd

• Status: CONFIRMED
• Product: Gentoo Linux

[Description Sven B. 2025-01-13 09:07:03 UTC]

Created attachment 916419 [details]
rust-1.84.0 build log

1.84.0 fails to build, 1.83.0-r1 builds fine.

  = note: /usr/bin/x86_64-pc-linux-gnu-ld.bfd: /var/tmp/portage/dev-lang/rust-1.84.0/temp/rustco5smjh/librustc_codegen_llvm-66164a4ba99020e3.rlib: error adding symbols: file format not recognized
          clang-19: error: linker command failed with exit code 1 (use -v to see invocation)

(...)

-------------
error: could not compile `rustc_driver` (lib) due to 1 previous error

[Comment 1 Sven B. 2025-01-13 09:07:31 UTC]

Created attachment 916420 [details]
emerge info

[Comment 2 Sven B. 2025-01-16 22:05:47 UTC]

ok, seems to be an lto+bfd issue.
According to e.g. https://github.com/rust-lang/rust/issues/54971 
this happens quite frequently.
Using lld as in the referenced bug fixed the issue.

[Comment 3 Zhixu Liu 2025-02-07 13:52:06 UTC]

same problem today, build success after remore USE="lto"

[Comment 4 Zhixu Liu 2025-02-09 16:43:40 UTC]

(In reply to Zhixu Liu from comment #3)
> same problem today, build success after remore USE="lto"

updated: use profile default/linux/amd64/23.0/hardened
   CC=gcc CXX=g++ USE="lto" emerge -Ov1e =rust-1.84.1 success
   CC=clang CXX=clang++ USE="lto" emerge -Ov1e =rust-1.84.1 failed

IIRC, I'm always use the later for emerge, never failed, seemes the failed start from 1.84.0

[Comment 5 Sam James 2025-02-10 03:01:07 UTC]

bfd can't work with Clang LTO (at least without using hacky plugin or maybe not at all). I'm surprised it ever worked.

[Comment 6 Zhixu Liu 2025-02-10 03:31:42 UTC]

(In reply to Sam James from comment #5)
> bfd can't work with Clang LTO (at least without using hacky plugin or maybe
> not at all). I'm surprised it ever worked.

hmm, it works for me until 1.84, :(

so we should handle this in ebuild too, i think?

[Comment 7 Sam James 2025-02-10 03:48:24 UTC]

I think the configuration is invalid... it'll definitely fail on other packages too.

[Comment 8 Nuno Alexandre 2025-02-22 18:55:46 UTC]

For anyone trying this too and getting an error I managed to get it working with this use flags:
+clippy +cpu_flags_x86_sse2 +doc +llvm_targets_NVPTX +lto +nightly +parallel-compiler +rust-analyzer +rust-src +rustfmt +system-llvm +verify-sig

env:
CFLAGS="-O2 -march=native -flto=thin"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-fuse-ld=lld"

CC="clang"
CXX="clang++"
LD="ld.lld"
AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"

RUSTFLAGS="-C opt-level=2 -C target-cpu=native -C embed-bitcode=yes -C linker=clang -C link-arg=-fuse-ld=lld"

[Comment 9 Sam James 2025-02-22 19:07:23 UTC]

*** Bug 950100 has been marked as a duplicate of this bug. ***

[Comment 10 rodolfo 2025-02-24 16:08:31 UTC]

(In reply to Nuno Alexandre from comment #8)
> RUSTFLAGS="-C opt-level=2 -C target-cpu=native -C embed-bitcode=yes -C
> linker=clang -C link-arg=-fuse-ld=lld"

Is lto actually enabled if -Clinker-plugin-lto is missing?

[Comment 11 zyxhere 2025-02-25 22:39:44 UTC]

(In reply to rodolfo from comment #10)
> (In reply to Nuno Alexandre from comment #8)
> > RUSTFLAGS="-C opt-level=2 -C target-cpu=native -C embed-bitcode=yes -C
> > linker=clang -C link-arg=-fuse-ld=lld"
> 
> Is lto actually enabled if -Clinker-plugin-lto is missing?

With USE="lto" yes

[Comment 12 Zhixu Liu 2025-03-03 02:29:56 UTC]

RUSTFLAGS="-C link-arg=-fuse-ld=lld" is enough, but the problem is "llvm-core/lld" is not in BDEPEND, so it still failed if lld is not emerged.

I don't know howto add llvm-core/lld into BDEPEND, like bellow:

> if use lto && tc-is-clang ; then
>        BDEPEND+="llvm-core/lld"
> fi

[Comment 13 zyxhere 2025-03-09 08:53:27 UTC]

Created attachment 920386 [details]
build.log,xz