[PATCH] D120305: [Driver] Default CLANG_DEFAULT_PIE_ON_LINUX to ON

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added a comment.

In D120305#3346947 <https://reviews.llvm.org/D120305#3346947>, @tstellar wrote:

> In D120305#3346880 <https://reviews.llvm.org/D120305#3346880>, @MaskRay wrote:
>
>> In D120305#3346787 <https://reviews.llvm.org/D120305#3346787>, @nemanjai wrote:
>>
>>> In D120305#3346144 <https://reviews.llvm.org/D120305#3346144>, @MaskRay wrote:
>>>
>>>> In D120305#3345978 <https://reviews.llvm.org/D120305#3345978>, @MaskRay wrote:
>>>>
>>>>> In D120305#3345810 <https://reviews.llvm.org/D120305#3345810>, @RKSimon wrote:
>>>>>
>>>>>> @MaskRay The ppc buildbots have been red since these patches - please can you take a look? https://lab.llvm.org/buildbot/#/builders/57/builds/15454
>>>>>
>>>>> Seems that ppc64 doesn't support test/sanitizer_common test/crt -fpie. I'll just disable them: https://github.com/llvm/llvm-project/issues/54084
>>>>
>>>> Actually I don't know how to disable the tests: https://lab.llvm.org/buildbot/#/builders/57/builds/15497 still failed.
>>>> Hope someone from #powerpc <https://reviews.llvm.org/tag/powerpc/> can disable them.
>>>
>>> This does not appear to be a matter of simply marking some tests as UNSUPPORTED. Since this landed, there have been many builds with different sanitizer failures and different numbers of sanitizer failures. Please pull this patch to bring the bots back to green and we can work with you next week on fixing what needs to be fixed.
>>
>> I enabled -DCLANG_DEFAULT_PIE_ON_LINUX=OFF for clang-ppc64le-rhel: https://github.com/llvm/llvm-zorg/commit/b6ddf02ce3a54da2df29e7e599b1838167e0e3ad
>> which should fix the issues.
>>
>> While I feel sorry for leaving clang-ppc64le-rhel red for some time and am willing to fix issues if I have access to a ppc64 machine (especially compiler-rt ones that I care about),
>> I feel uncomfortably if a group just bluntly request "please pull this patch" when apparently (a) there is a better approach (explicitly setting CLANG_DEFAULT_PIE_ON_LINUX=OFF) and (b) there is something a bot maintainer can do
>> and (c) there is just some inherent stability problem (in this case, consider not enabling the testing when the target is still unstable) that is causing not only this issue, but various other reports (as I watch sanitizer failures quite closely and ppc64 often tends to be the outlier thing)
>
> Fixing the buildbot like this doesn't help regular users though.  I think it's better to revert and then work on a solution as @nemanjai suggested.  What  are the downsides to reverting this?

Well, I can speak for regular ppc64le users now since q66 kindly gives me access to a ppc64le machine.
`check-lsan check-sanitizer check-crt` etc passed fairly well with default PIE Clang.

I think we previously paid too less attention on build bot stability problems.
In this case I suspected again this is such a problem (typically sanitizer not so compatible with some older glibc/binutils)

  <stdin>:1:16: note: possible intended match here
  error: Segmentation fault (core dumped)


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https://reviews.llvm.org/D120305