Code compiled with different #[cfg] flags shows up as different instantiations

[Ekleog-NEAR]

Initially reported by @Dushistov here:

Oh, that's why not generic functions some times have several instantiation according to html generated by cargo-llvm-cov:

The solution might end up being the same as #43

[michaelvlach]

As taiki-e said in the other thread this is a problem of LLVM and not much can be done in cargo-llvm-cov about it. The coverage profiles should be merged but llvm-cov/llvm-profdata would need to do that.

[taiki-e]

(I'm wondering if this may be another instance of #325.)

[michaelvlach]

(I'm wondering if this may be another instance of #325.)

It almost certainly is. I am also pleasantly surprised that I was wrong and that the issue can be solved with a demangler even with current LLVM implementation! That is great news and could improve teh quality of the coverage reporting.

[taiki-e]

This probably has been fixed in v0.6.7 (#354). Could you recheck this with v0.6.7?

[michaelvlach]

This probably has been fixed in v0.6.7 (#354). Could you recheck this with v0.6.7?

Thanks for this, I have tried it and I see no missing lines with multiple instantiations anymore as long as the coverage overlaps.

The only remaining issue is await not always mark as executed even though call cahing before/after was executed. But that is a different issue I think not related to demangler or instantiations.

[taiki-e]

Thanks for confirming!

The only remaining issue is await not always mark as executed even though call cahing before/after was executed. But that is a different issue I think not related to demangler or instantiations.

Yeah, it's different rustc bug: rust-lang/rust#98712