Files without tests missing from final report

[dnaka91]

I noticed that files without any test data are not included in the grcov outputs (specifically the HTML report). This additionally seems to give a wrong coverage percentage, showing a higher percentage than expected as all files without coverage data are not counted in.

Noticed this in my Rust projects so it might be specific to Rust eventually.

Is there any option to tell grcov to take uncovered files into account when generating the report?
Couldn't find anything so far that would help in this regards.

[TilBlechschmidt]

I ran across the same issue. It is related to the fact that compilers are way too smart these days and strip all the unused functions from the binary. In a test-scenario this means that all the files that have no used functions under a #[cfg(test)] scenario will not be included. This in turn, results in grcov having no clue about them even existing.

For more information, have a look at this Rust PR: rust-lang/rust#31368

TL;DR Run your code with the new compiler flag -Clink-dead-code like this

export RUSTFLAGS="-Zinstrument-coverage -Clink-dead-code"
export LLVM_PROFILE_FILE="coverage-pid%p.profraw"

cargo +nightly test --tests

# Run grcov now as usual

[taiki-e]

This is a bug of -Zinstrument-coverage: rust-lang/rust#86177

Note that -Clink-dead-code works as a workaround, but -Clink-dead-code is basically considered incompatible with -Zinstrument-coverage. So it is likely to cause other problems.
See also richkadel's comments in taiki-e/cargo-llvm-cov#26

[snue]

rust-lang/rust#86177 has been resolved.
I think this issue can be closed.