[cfe-dev] Absolute paths in code coverage info

[Keith Smiley via cfe-dev]

Thanks for the context! I found the revert
https://github.com/llvm/llvm-project/commit/62808631acceaa8b78f8ab9b407eb6b943ff5f77
and
it looks like it was caused by a small test issue. I'm a bit surprised by
the justification for it since I would expect relying on the specific
directory of the test to be safe, but I think I can make it work and
re-submit.
--
Keith Smiley


On Tue, Jun 2, 2020 at 10:44 AM Vedant Kumar <vsk at apple.com> wrote:

> A problem that absolute paths solve in local builds is dealing with a
> changing compilation directory - this can result in two different files
> being referenced by the same relative path.
>
> There was a promising attempt to make this work with remote builds. The
> idea was to have the coverage mapping logic respect a fixed compilation
> directory option (https://reviews.llvm.org/D68733), i.e. the paths
> embedded in the coverage mapping should be rooted at the
> -fdebug-compilation-dir <path>. It looks like the patch was reverted, but
> (as far as I know) there aren’t any fundamental issues with it.
>
> On Jun 2, 2020, at 9:57 AM, Keith Smiley via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
> Hey everyone,
>
> Currently when generating code coverage by passing
> `-fprofile-instr-generate -fcoverage-mapping` to clang, the __LLVM_COV /
> __llvm_covmap section ends up containing absolute paths to the source files
> being compiled. This causes issues when producing coverage info with remote
> builds where the absolute paths to the source files may differ between
> machines.
>
> llvm-cov has a `-path-equivalence` flag in order for you to remap a single
> absolute path from the coverage info which definitely helps, but it doesn't
> solve this entirely for the cases where you have multiple paths that need
> remapping, or you're using another tool such as, Xcode's code coverage UI,
> that doesn't support this kind of path remapping.
>
> I'm wondering if it has been discussed, or how feasible it would be, for
> me to remove the necessity for absolute paths in this info.
>
> Thanks!
> --
> Keith Smiley
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>
>
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