bugGNU Octave - Bugs: bug #57591, Segmentation faults with clang...

 
 

bug #57591: Segmentation faults with clang when running the test suite

Submitted by:  Markus Mützel <mmuetzel>
Submitted on:  Mon 13 Jan 2020 03:34:54 PM UTC  
 
Category:  Test Suite Severity:  5 - Blocker
Priority:  5 - Normal Item Group:  Segfault, Bus Error, etc.
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  Open
Release:  dev Operating System:  GNU/Linux

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( Jump to the original submission)

Mon 20 Jan 2020 07:59:31 AM UTC, comment #9: 

Thanks for testing again.

There seem to be occasional segfaults also for the gcc-7-lto-debian buildbot:
http://buildbot.octave.org:8010/#/builders/24/builds/1141/steps/6/logs/stdio

This might be related or it might be caused by something different.

Markus Mützel <mmuetzel>
Project Member
Fri 17 Jan 2020 10:03:36 PM UTC, comment #8: 

I ran the test suite twice while compiling other projects in the background, and no difference for me.

Mike Miller <mtmiller>
Project Administrator
Fri 17 Jan 2020 06:23:28 AM UTC, comment #7: 

@Mike: Thanks for your tests. The segfaults occur only intermittently on the buildbots. It might be that they only occur when the machine is under heavy load. E.g. when an mxe job is running on the same machine at the same time.

Could you please try to stress your machine while you are running the test suite and check if it still doesn't segfault?

Markus Mützel <mmuetzel>
Project Member
Thu 16 Jan 2020 10:53:06 PM UTC, comment #6: 

I further built the default branch with Clang 6 and Clang 10 (Git snapshot), and the full test suite runs fine with them. I don't have any older versions of Clang readily available without setting up a container or VM.

So if this buildbot segmentation fault is real, it seems to have been fixed with Clang 6 and later.

I don't think there's any particular reason why those buildbots use Clang 4 and 5, probably just old configurations that haven't been updated.

Mike Miller <mtmiller>
Project Administrator
Thu 16 Jan 2020 08:10:44 AM UTC, comment #5: 

That wasn't clear to me either.
Would it make sense to update the buildbots to use newer clang versions? Or is there a particular reason they run with clang 4 and clang 5?

Markus Mützel <mmuetzel>
Project Member
Wed 15 Jan 2020 09:10:31 PM UTC, comment #4: 

Ok, that wasn't clear in this report. If this error only occurs with older versions of Clang, and never with newer versions, then it's probably not worth fixing, right?

Mike Miller <mtmiller>
Project Administrator
Wed 15 Jan 2020 09:00:19 PM UTC, comment #3: 

8 is reasonably new, the fault is with clang 4 and 5.
Fedora has 9 and it is also fine.

Dmitri.
--

Dmitri A. Sergatskov <dasergatskov>
Wed 15 Jan 2020 08:55:34 PM UTC, comment #2: 

I am not able to reproduce this segmentation fault on my system (Debian) with Clang version 8 (with or without xvfb-run). The full test suite runs for me with only 2 test failures in publish.tst, same exact results as with GCC.

Mike Miller <mtmiller>
Project Administrator
Tue 14 Jan 2020 04:22:52 PM UTC, comment #1: 

Maybe need to compile a version with debugging symbols and attempt "__run_test_suite__" manually under a debugger so that a backtrace can be obtained.

This could be a problem with clang, but more likely it is something generic that we are doing incorrectly that only occasionaly surfaces for combinations of compiler, libraries, and machine.

Rik <rik5>
Project Administrator
Mon 13 Jan 2020 03:34:54 PM UTC, original submission:  

The test suite repeatedly fails to complete on the clang buildbots:
http://buildbot.octave.org:8010/#/builders/12/builds/1525/steps/6/logs/stdio
http://buildbot.octave.org:8010/#/builders/10/builds/1322/steps/6/logs/stdio
http://buildbot.octave.org:8010/#/builders/12/builds/1522/steps/6/logs/stdio
http://buildbot.octave.org:8010/#/builders/10/builds/1317/steps/6/logs/stdio
http://buildbot.octave.org:8010/#/builders/10/builds/1315/steps/6/logs/stdio
http://buildbot.octave.org:8010/#/builders/12/builds/1516/steps/6/logs/stdio
And several more.

The segmentation fault seems to occur at random tests. It occurs with both the clang 4.0 and the clang 5.0 buildbots.

This should ideally be fixed before releasing Octave 6.1.
If we don't aim to support clang, the priority can probably be lowered.

Markus Mützel <mmuetzel>
Project Member

 

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