[cfe-dev] Absolute paths in code coverage info

Mon Sep 21 17:09:15 PDT 2020

If folks are interested by havn't been following along with the diff,
there's also an implementation of the `-fdebug-compilation-dir`-like flag
for profile data here: https://reviews.llvm.org/D87928 along with some more
discussion around the details of how `-fprofile-prefix-map` would work
here: https://reviews.llvm.org/D83154
--
Keith Smiley

On Fri, Jul 3, 2020 at 10:31 PM Keith Smiley <keithbsmiley at gmail.com> wrote:

> Here's the diff, please let me know what you think!
> https://reviews.llvm.org/D83154
> --
> Keith Smiley
>
>
> On Fri, Jun 26, 2020 at 3:11 PM Max Moroz <mmoroz at google.com> wrote:
>
>> No objections from me!
>>
>> On Thu, Jun 25, 2020 at 11:42 AM Vedant Kumar <vsk at apple.com> wrote:
>>
>>> Thanks Keith, that sounds great to me!
>>>
>>> vedant
>>>
>>> On Jun 24, 2020, at 6:11 PM, Keith Smiley <keithbsmiley at gmail.com>
>>> wrote:
>>>
>>> Yes. I'm happy to implement the plan as I it understand so far. Please
>>> correct me if I'm wrong.
>>>
>>> 1. Add the new -coverage-prefix-map flag
>>> 2. Make -ffile-prefix-map imply this new flag.
>>> 3. No new *dir flags for now
>>> 4. No changes to -fdebug-prefix-map
>>>
>>> --
>>> Keith Smiley
>>>
>>>
>>> On Wed, Jun 24, 2020 at 4:10 PM Max Moroz <mmoroz at chromium.org> wrote:
>>>
>>>> Sorry for the late reply (I was on leave). Is this still relevant?
>>>>
>>>> On Tue, Jun 9, 2020 at 5:50 PM Vedant Kumar <vsk at apple.com> wrote:
>>>>
>>>>> Any objections to starting with having -ffile-prefix-map imply
>>>>> “relative paths for coverage mappings”? I think this would work for both
>>>>> Petr and Keith’s use cases.
>>>>>
>>>>> vedant
>>>>>
>>>>> On Jun 5, 2020, at 11:04 AM, Vedant Kumar <vsk at apple.com> wrote:
>>>>>
>>>>>
>>>>> On Jun 4, 2020, at 4:17 PM, Dan McGregor <danismostlikely at gmail.com>
>>>>> wrote:
>>>>>
>>>>> I like Vendant and Petr's proposals. -ffile-prefix-map was really
>>>>> intended to be a union of -fdebug-prefix-map and -fmacro-prefix-map.
>>>>> If a coverage-prefix-map is added I think it makes sense to add it to
>>>>> file-prefix-map.
>>>>>
>>>>>
>>>>> Thanks Dan. This part sounds good to me. If I’ve understood the
>>>>> motivation for https://reviews.llvm.org/D68733, and given Petr’s
>>>>> plans, it sounds there’s interest in both the coverage-prefix-map and the
>>>>> coverage-compilation-dir options. Is that a fair summary?
>>>>>
>>>>> Likewise for debug-compilation-dir and
>>>>> coverage-compilation-dir, and any hypothetical users of
>>>>> macro-compilation-dir, though I don't think the compilation directory
>>>>> is exposed to the preprocessor at all..
>>>>>
>>>>>
>>>>> Is your preference for -coverage-compilation-dir being set by
>>>>> -file-prefix-map, or for a new union flag that sets a relative compilation
>>>>> dir (like -ffile-compilation-dir)? I’m assuming the latter, since the
>>>>> summary from https://reviews.llvm.org/D63387 states that a downside
>>>>> of the -fdebug-prefix-map=old=new syntax is that it "requires putting the
>>>>> absolute path to the build directory on the build command line”, which I
>>>>> suppose we’d want to avoid for any *-compilation-dir flag. I’d be
>>>>> interested in hearing what others think as well.
>>>>>
>>>>> vedant
>>>>>
>>>>>
>>>>> On Thu, 4 Jun 2020 at 15:08, Keith Smiley <keithbsmiley at gmail.com>
>>>>> wrote:
>>>>>
>>>>>
>>>>> I don't have a ton of context on the history of all these flags, but
>>>>> I'm happy to implement either of those solutions once we have consensus!
>>>>> --
>>>>> Keith Smiley
>>>>>
>>>>>
>>>>> On Thu, Jun 4, 2020 at 12:05 PM Vedant Kumar <vsk at apple.com> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On Jun 3, 2020, at 2:38 PM, Petr Hosek <phosek at chromium.org> wrote:
>>>>>
>>>>> Would there be any opposition against supporting -ffile-prefix-map in
>>>>> coverage mappings in addition to -fdebug-compilation-dir? We hit this issue
>>>>> recently as well, and I was thinking about implementing a similar change
>>>>> for -ffile-prefix-map.
>>>>>
>>>>>
>>>>> I think it’s a good idea.
>>>>>
>>>>> One potential issue is that -ffile-prefix-map isn't currently passed
>>>>> to cc1, rather it implies --debug-prefix-map but I'm not sure if we want to
>>>>> make change semantics of that flag to apply to coverage as well which would
>>>>> affect existing users of -fdebug-prefix-map,
>>>>>
>>>>>
>>>>> Thanks for flagging this. You’re right, changing the absolute path
>>>>> behavior under -fdebug-prefix-map might break llvm-cov workflows which
>>>>> aren’t using -path-equivalence. -ffile-prefix-map seems relatively new, and
>>>>> also its purpose is to be a ‘union’ of other *prefix-map options, so having
>>>>> this imply —coverage-prefix-map makes sense to me.
>>>>>
>>>>> maybe we should introduce a new cc1 flag, e.g. --coverage-prefix-map,
>>>>> which would be also implied by -ffile-prefix-map.
>>>>>
>>>>>
>>>>> Sounds good to me. But for consistency, maybe we should rethink how
>>>>> -fdebug-compilation-dir <relpath> is handled. A couple options:
>>>>>
>>>>> - Have `-fdebug-compilation-dir <relpath>` (driver flag) imply
>>>>> `—coverage-prefix-map=$(abspath <relpath>)=./` (cc1 flag).
>>>>>
>>>>> The absolute path is hidden from the driver invocation, so this can
>>>>> still be used by a caching build system. I’m assuming we don’t embed the
>>>>> cc1 flags anywhere, e.g. not in the DW_AT_APPLE_flags. This is the closest
>>>>> to what https://reviews.llvm.org/D81122 is currently doing.
>>>>>
>>>>> - Introduce `-ffile-compilation-dir <relpath>` (driver flag), which
>>>>> implies `-fdebug-compilation-dir <relpath>` (cc1 flag) and a new
>>>>> `-fcoverage-compilation-dir <relpath>`
>>>>>
>>>>> Essentially, make -ffile-compilation-dir analogous to
>>>>> -ffile-prefix-map, a union of *compilation-dir options.
>>>>>
>>>>> vedant
>>>>>
>>>>>
>>>>> On Wed, Jun 3, 2020 at 11:09 AM Vedant Kumar via cfe-dev <
>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On Jun 2, 2020, at 5:17 PM, Keith Smiley <keithbsmiley at gmail.com>
>>>>> wrote:
>>>>>
>>>>> FWIW after updating this patch I've verified that llvm-cov in the
>>>>> source directory with no `-path-equivalence` works fine, and also using
>>>>> `-path-equivalence=,$SRCROOT` works if you want to run it not from the
>>>>> source root.
>>>>>
>>>>>
>>>>> That’s great to hear. I’ve cc’d Reid and Yuke who may have more
>>>>> context on this patch and any potential pitfalls with it.
>>>>>
>>>>> 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.
>>>>>
>>>>>
>>>>> It might be sufficient to add a section to the llvm-cov command guide
>>>>> explaining how to use -fdebug-compilation-dir and -path-equivalence to get
>>>>> remote builds working.
>>>>>
>>>>> --
>>>>> 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
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> cfe-dev mailing list
>>>>> cfe-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>> --
>>> Keith Smiley
>>>
>>>
>>>
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