Bug 385648

Summary: discover doesn't start with Qt 5.9.2
Product: [Applications] Discover Reporter: Antonio Rojas <arojas>
Component: discoverAssignee: Aleix Pol <aleixpol>
Status: RESOLVED FIXED    
Severity: major    
Priority: NOR    
Version First Reported In: 5.11.0   
Target Milestone: ---   
Platform: Compiled Sources   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Antonio Rojas 2017-10-12 09:25:02 UTC 
discover --listmodes crashes with Qt 5.9.2. Works fine with 5.9.1.

ASSERT failure in QList<T>::at: "index out of range", file /usr/include/qt/QtCore/qlist.h, line 541

Thread 1 "plasma-discover" received signal SIGABRT, Aborted.
0x00007ffff35f08a0 in raise () from /usr/lib/libc.so.6
(gdb) bt
#0  0x00007ffff35f08a0 in raise () from /usr/lib/libc.so.6
#1  0x00007ffff35f1f09 in abort () from /usr/lib/libc.so.6
#2  0x00007ffff3d90858 in QMessageLogger::fatal(char const*, ...) const () from /usr/lib/libQt5Core.so.5
#3  0x00007ffff3d8bc0b in qt_assert_x(char const*, char const*, char const*, int) () from /usr/lib/libQt5Core.so.5
#4  0x00005555555691b4 in QList<QObject*>::at (i=0, this=0x7fffffffe2f0) at /usr/include/qt/QtCore/qlist.h:541
#5  DiscoverMainWindow::rootObject (this=<optimized out>) at /build/discover/src/discover-5.11.0/discover/DiscoverMainWindow.cpp:404
#6  0x0000555555569ee3 in DiscoverMainWindow::modes (this=<optimized out>) at /build/discover/src/discover-5.11.0/discover/DiscoverMainWindow.cpp:130
#7  0x0000555555565b96 in main (argc=<optimized out>, argv=<optimized out>) at /build/discover/src/discover-5.11.0/discover/main.cpp:137
Comment 1 Antonio Rojas 2017-10-12 10:02:53 UTC 
Possibly related: running plasma-discover (without parameters) hangs and the application never starts. Again, no issues with Qt 5.9.1

Thread 1 "plasma-discover" received signal SIGINT, Interrupt.
0x00007ffff36a7d4b in poll () from /usr/lib/libc.so.6
(gdb) bt
#0  0x00007ffff36a7d4b in poll () at /usr/lib/libc.so.6
#1  0x00007fffedcf0ed3 in  () at /usr/lib/libglib-2.0.so.0
#2  0x00007fffedcf0fae in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#3  0x00007ffff3fe4cd1 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#4  0x00007ffff3f8848b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#5  0x00007ffff3f914d8 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5
#6  0x0000555555565d8a in main(int, char**) (argc=<optimized out>, argv=<optimized out>) at /build/discover/src/discover-5.11.0/discover/main.cpp:151
Comment 2 Antonio Rojas 2017-10-12 17:46:38 UTC 
Reverting this commit in qtdeclarative fixes both issues

https://github.com/qt/qtdeclarative/commit/98358715930739ca8de172d88c5ce6941c275ff3
Comment 3 Antonio Rojas 2017-10-14 10:08:49 UTC 
Backporting 36fc062a77257e5d744fe4029149fc05a71db4b2 fixes the crash, but it breaks the UI since Helpers is still used in 5.11
Comment 4 Aleix Pol 2017-10-14 22:35:51 UTC 
So you don't have the issue if you clear the cache?
Comment 5 Antonio Rojas 2017-10-14 22:49:20 UTC 
Removing ~/.cache/discover doesn't make any difference
Comment 6 Aleix Pol 2017-10-16 10:22:07 UTC 
I backported the Helpers removal into 5.11.

I could reproduce this issue on my system too.

Thanks a lot Antonio for the bug!