malformed instrumentation profile data in nightly-2025-07-24

[davidhewitt]

On the PyO3 repository, I tried this code with nightly-2025-07-24 (ace633090 2025-07-23):

cargo llvm-cov --lib

I expected to see this happen: successful generation of coverage report.

Instead, this happened:

error: failed to load coverage: 'target/llvm-cov-target/debug/deps/pyo3-9c271fe7713fe0d5': malformed instrumentation profile data: function name is empty

Meta

The issue is not present on nightly-2025-07-23 (a7a1618e6 2025-07-22) or earlier versions, and continues to be an issue with all nightly versions tested since.

rustc --version --verbose:

rustc 1.90.0-nightly (ace633090 2025-07-23)
binary: rustc
commit-hash: ace633090349fc5075b5b0d56294de985e7d1191
commit-date: 2025-07-23
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.8
``

[davidhewitt]

Possibly can be closed as a duplicate of #141577

[lqd]

This issue will be fixed soon by #144480. Closing this one as a duplicate of #141577.

Thanks for opening the issue!