Arch Linux

Kid98

Member

Registered: 2013-08-27

Posts: 3

Mythbackend Segfault

Hello all,
     I was having an issue with mythbackend running on arch 64 on an intel setup.  Since I updated a few weeks ago, mythbackend started crashing whenever I attempted to access it via mythweb or the new version 0.28 internal browser and also via the mythtv channel pllugin via plex.
I have tried everything from reinstalling to rolling back packages that updated at the time the problem began.  Finally I found the culprit. QT5-base.  It seems the new version has a bug that can cause this crashing.  (found that info on a ticket regarding backend crashing at mythtv.org)
Just wanted to post for others benefit that rolling back to qt5-base-5.6.0-4-x86_64 fixed the crashing issue for me.

Hope this helps others.  I know this forum has been a blessing to me....

Kid

Last edited by Kid98 (2016-06-02 16:33:13)

Da_Coynul

Member

From: United States of America

Registered: 2010-10-02

Posts: 85

Re: Mythbackend Segfault

Thanks for the tip, Kid! I have been struggling with the segfaults as well. I just got around to doing a backtrace and was planning to add it to ticket #12688 on the MythTV bug tracker.

Jon

Last edited by Da_Coynul (2016-06-04 17:41:44)

Da_Coynul

Member

From: United States of America

Registered: 2010-10-02

Posts: 85

Re: Mythbackend Segfault

Here's an update:

This problem seems to be related to GCC 6 and "some non-conforming code-bases" including Qt-5 as stated here. A workaround is to build  qt5-base with the GCC flag -fno-delete-null-pointer-checks. This can be accomplished using the Arch Build System (ABS) and modifying the PKGBUILD to include an options array allowing the use of custom buildflags:

options=( buildflags )

Next, add the following to ~/.makepkg.conf:

CFLAGS="-fno-delete-null-pointer-checks"
CXXFLAGS="-fno-delete-null-pointer-checks"

Finally, build your custom qt5-base, install it and restart mythbackend. Now you should have mythbackend running with the latest Qt5 minus the segfaults.

This issue has been discussed on the Qt Development mailing list but it clearly has not been fixed as of the 5.6 release.

Last edited by Da_Coynul (2016-06-04 17:54:28)

sultanoswing

Member

Registered: 2008-07-23

Posts: 314

Re: Mythbackend Segfault

Fantastic!

Thanks for the workaround Da_Coynul. This problem had been bugging me for several weeks, so it's great to have a working solution. Cheers!

---

6.5.3.arch1-1(x86_64) w/Gnome 44.4
Arch on: ASUS Pro-PRIME x470, AMD 5800X3D, AMD 6800XT, 32GB, | Intel NUC 7i5RYK | ASUS ux303ua | Surface Laptop

jabster

Member

Registered: 2013-05-04

Posts: 10

Re: Mythbackend Segfault

Just wanted to post for others benefit that rolling back to qt5-base-5.6.0-4-x86_64 fixed the crashing issue for me.

Hope this helps others.  I know this forum has been a blessing to me....

Kid

Ah.

Thank you SO much for this.

I can finally watch TV again!

-john

Kid98

Member

Registered: 2013-08-27

Posts: 3

Re: Mythbackend Segfault

Well I got brave when I saw qt 5.7 packages out.  It seems that was a mistake.  Da Coynul, are you on x86-64 and if so could you share your packages to fix this  issue.  Mythweb works for a short while for me then eventually crashes after several  accesses.  I am worried that installilng ABS and configuring it might be over my head...

Kid

hamelg

Member

From: France

Registered: 2008-06-19

Posts: 128

Re: Mythbackend Segfault

qt5-base-5.7.0-1-x86_64.pkg.tar.xz
http://dl.free.fr/wRrP6zDyj

Kid98

Member

Registered: 2013-08-27

Posts: 3

Re: Mythbackend Segfault

Thanks so much hamelg.  That seems to have mythtv working now.  I am gonna install ABS when time allows and learn how to use it.
Thanks again!!

Kid

Da_Coynul

Member

From: United States of America

Registered: 2010-10-02

Posts: 85

Re: Mythbackend Segfault

Well I got brave when I saw qt 5.7 packages out.  It seems that was a mistake.  Da Coynul, are you on x86-64 and if so could you share your packages to fix this  issue.  Mythweb works for a short while for me then eventually crashes after several  accesses.  I am worried that installilng ABS and configuring it might be over my head...

It turns out that the segfaults were caused by a bug in mythtv after all.  A fix has been proposed: https://github.com/MythTV/mythtv/pull/122 although it has not yet been accepted.  I applied the patch, rebuilt mythtv and using the latest unmodified qt5-base package I am not seeing any segfaults. So the workaround I posted earlier is no longer needed

Jon

Last edited by Da_Coynul (2016-07-03 10:47:41)