`llvm-cov` [rust] Coverage Source code not covered when rust code is across multiple lines

[Ryang20718]

I tried this code:

    log::info!(
        "hello world {} 12323123123123123123123123123123123123123123123123",
        "Testing"
    );

I expected all lines to be covered. However, only the first line is covered

log::info!(

All other lines are not covered

Version

LLVM (http://llvm.org/):
  LLVM version 19.1.7-rust-1.86.0-stable
  Optimized build.

might be related?

#82259
#54579

[EugeneZelenko]

Could you please try 20 or main branch?

[Ryang20718]

@EugeneZelenko I made a minimal repro which still has the issue on llvm 20 https://github.com/Ryang20718/llvm-rust-repro/blob/main/README.md

Instructions are on readme

[Ryang20718]

apologies made this repo public

[arielb1]

As far as I can tell LLVM is correct. You have not enabled logging in your test, so the code within log::info! did not run.

As you can see in https://docs.rs/log/0.4.27/src/log/macros.rs.html#121, the code within the info! macro will not run unless you enable a log level.

[Ryang20718]

what's interesting is that if the entire line is formatted on 1 line, it's counted as covered. Is this a bug?

[arielb1]

The log::info!( line contains the if lvl <= $crate::STATIC_MAX_LEVEL && lvl <= $crate::max_level() condition, which is always run (even if the code doesn't go into the if). Therefore, that line is always covered.

Since you are using line coverage as opposed to MC/DC coverage, the only thing that counts is that, for every source code line that is associated with binary instructions, at least 1 instruction from that line is run.

If you have lines within the log statement, then these lines have code associated with them, and all the code associated with them if the log statement is entered into, and therefore they are uncovered if the log is skipped.