[cfe-dev] Absolute paths in code coverage info

[Keith Smiley via cfe-dev]

FWIW after updating this patch I've verified that llvm-cov in the source
directory with no `-path-equivalence` works fine, and also using
`-path-equivalence=,$SRCROOT` works if you want to run it not from the
source root. The latter might be a bit unexpected since folks may prefer
`-path-equivalence=.,$SRCROOT` which I'm sure we could implement if that
was the missing piece.
--
Keith Smiley


On Tue, Jun 2, 2020 at 2:49 PM Keith Smiley <keithbsmiley at gmail.com> wrote:

> Ah actually it looks like that issue was resolved, but it was reverted a
> second time for:
>
> > There seem to be bugs in llvm-cov --path-equivalence that are causing
> Chromium problems. Revert this until they are understood or fixed.
>
>
> https://github.com/llvm/llvm-project/commit/7cd595df96d5929488063d8ff5cc3b5d800386da
>
> Does anyone have more context on those?
> --
> Keith Smiley
>
>
> On Tue, Jun 2, 2020 at 2:27 PM Keith Smiley <keithbsmiley at gmail.com>
> wrote:
>
>> 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
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>
>>>
>>>
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