Bug: QLC+ (4.5.0 GIT) Crashes when running a chaser and faders in level mode are present in VC

Luis García-Tornel · Tue Aug 05, 2014 8:38 pm

Hi Massimo:

I've just compiled from sources to test the feedback in VC sliders (Thanks for implementing this!!!) but I've run into trouble.

The program crashes with a "Segmentation fault (core dumped)" error in the console When running a chaser from the VC **AND** faders (in level mode) are present the VC **AND** the chaser involves a scene with more than one channel.

In ubuntu's bug report appears the following line:
qlcplus crashed with SIGSEGV in QWidgetPrivate::syncBackingStore()

I've recompileed with a make distclean in the case was compiling error but the problem persisted

Additional data:
QLC+ 4.7.5 GIT
Both Ubuntu 14.04 64bits and 13.10 32bits

If there's any more info you need feel free to ask.

LUIS

EDIT: Attached a test workspace where the error occurs
Sorry about the error in the title where it says 4.5.0 it should be 4.7.5

Luis García-Tornel · Tue Aug 05, 2014 10:20 pm

One more thing: it happens with QT4 but with QT5 all seems to work OK

Massimo Callegari · Wed Aug 06, 2014 8:51 am

Hi Luis, I moved this to the development thread.
Do you have a simple project that you can share that shows this issue ?

I will check again on Qt4, maybe it's a trivial thing to fix.
Thanks

Luis García-Tornel · Wed Aug 06, 2014 2:23 pm

I've already attached a file in the first post

Massimo Callegari · Wed Aug 06, 2014 2:39 pm

Ooops sorry, didn't see it. Gonna test it later tonight, thanks

Massimo Callegari · Wed Aug 06, 2014 8:27 pm

Luis, the bug is confirmed and I'm struggling right now to fix it.
Unfortunately I believe this is one of those Qt multithread graphics issue not easy at all to solve.
Working on it...

Massimo Callegari · Sun Aug 10, 2014 1:01 pm

Hi Luis, I think I have solved this (thanks to how Jano did it on the XY pad

)

Can you please try the GIT sources on your system and tell me if the crash has gone ?

Thanks

Luis García-Tornel · Sun Aug 10, 2014 7:29 pm

Yes, the crash has gone! Thanks!

However, there's one more issue (I don't know if it's related or not).

You can't set the intensities with the faders even if the chaser is not running, they come back to 0 (or, if a scene is active, to whatever the intensities of the scene are).

Checking with the fixture monitor you can see that it actually tries to set the intensity but *something* overrides it.

It happens in both QT4 and QT5.

Luis García-Tornel · Sun Aug 10, 2014 8:09 pm

Since I don't know if I made myself clear here is a video showing the issue.

http://youtu.be/FrMFCHyiSy4

Chris Laurie · Sun Aug 10, 2014 9:32 pm

I "think" I have seen this as well. I thought it was because I was trying to re-use an previous (very busy) workspace and had edited in a way that left it unstable. I was deleting/add/updating fixtures, scenes, audio and loads of widgets.

I will try the exact file in an older version and see if I can reconstruct.

This was on the GIT version of about a week ago.