Enabling LTO causes miscompilation on x86_64-apple-darwin

[briansmith]

This is from https://github.com/briansmith/ring 's CI, testing the tip of the main branch. The CI passes on 1.86 and fails on multiple targets when building with 1.87. In at least one case, building and linking passes but the test fails, indicating potentially the code (computing HMAC) or the test of the code is being miscompiled.

Unfortunately, I have limited access to systems that would help me reduce these today. I have noticed another project has run into a similar linker error recently. I apologize in advance for such a poor bug report. I hope I, or ideally others, could fill in the details, as I have limited availability today.

x86_64-apple-darwin

https://github.com/briansmith/ring/actions/runs/15143648178/job/42573984175

running 2 tests
test hmac_debug ... ok
test hmac_tests ... FAILED

failures:

---- hmac_tests stdout ----

thread 'hmac_tests' panicked at tests/hmac_tests.rs:83:9:
assertion `left == right` failed
  left: true
 right: false
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

(The test is checking whether the output of the HMAC computation is correct.)

[briansmith]

See tikv/tikv#18465 for another project that seems to have encountered the same error with the same unrecognized relocation type error on ARM64 Linux, using nightly-2025-04-04.

[briansmith]

The problem seems to be caused by LTO, as when I remove "lto = true" from the release profile in Cargo.toml, things are working. See https://github.com/briansmith/ring/actions/runs/15145798156.

[lqd]

Can you bisect the PR causing this with cargo-bisect-rustc? Thanks!

[briansmith]

Can you bisect the PR causing this with cargo-bisect-rustc? Thanks!

If you are asking me, then no. It is very unlikely I will get to it, though in normal circumstances I would try.

[lqd]

The bisection should be helpful regardless of who's doing it, it doesn't have to be you, no worries.