[PATCH] D45454: Make __gcov_flush visible outside a shared library

[Chih-hung Hsieh via llvm-commits]

Should we have two versions of `__gcov_flush`?

One version is visible outside a .so file,
we use dlsym to find and call it to dump
profile data of .so files, like Android.

One version is hidden and must be called from another
wrapper function in a .so file. An application that
wants to flush .so file profile data will need to call
those wrapper functions.


On Wed, Apr 11, 2018 at 12:31 PM, Xinliang David Li <xinliangli at gmail.com>
wrote:

>
>
> On Wed, Apr 11, 2018 at 11:31 AM, Chih-Hung Hsieh via Phabricator via
> llvm-commits <llvm-commits at lists.llvm.org> wrote:
>
>> chh added a comment.
>>
>> Yes, calling `__gcov_flush` within .so files are different,
>> but it's a revert of https://reviews.llvm.org/D38124.
>> I think  https://bugs.llvm.org/show_bug.cgi?id=27224
>> can be fixed by hiding only llvm_gcda_* functions,
>> without any change to `__gcov_flush`.
>>
>>
> The coverage dumping behavior for shared libraries (not dlopened) was also
> wrong before D38124. D38124 fixed the crash as well as the dumping bug.
>
> David
>
>
>
>
>
>> (1) Before https://reviews.llvm.org/D38124:
>>
>> - Calling `__gcov_flush` within .so or main function dumps to main gcda
>> file.
>> - Android's dlsym() lookup/call of `__gcov_flush` dumps to .so file
>> specific gcda files.
>>
>> (2) After https://reviews.llvm.org/D38124:
>>
>> - Android's dlsym() cannot find/call `__gcov_flush`.
>> - Calling `__gcov_flush` from main works as in (1).
>> - Calling `__gcov_flush` from .so works differently; it will dump to .so
>> specific gcda file, not the main one.
>>
>> (3) With this change, we revert `__gcov_flush` behavior back to (1).
>>
>> Is there any application that needs to call `__gcov_flush` within .so
>> and expects the output to .so specific gcda file like in (2)?
>> I think the behavior of (1) is more desirable.
>> If a main program wants to dump to .so specific gcda file, like Android,
>> it can use dlsym() to look up .so specific `__gcov_flush`.
>>
>>
>> https://reviews.llvm.org/D45454
>>
>>
>>
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>
>
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