Application: kwin_x11 (5.12.6)

Qt Version: 5.11.1
Frameworks Version: 5.50.0
Operating System: Linux 4.18.0-12-generic x86_64
Distribution: Ubuntu 18.10

-- Information about the crash:
- Unusual behavior I noticed:
When starting KDE for the first time, plasmashell also crashed as well, and I had to restart SDDM to get back. KWin will still not load, though. I'm using Openbox for now.

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin_x11), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7ff8756af840 (LWP 3281))]

Thread 4 (Thread 0x7ff85ffff700 (LWP 3381)):
#0  0x00007ff87d4822eb in futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x7ff87e65afb8) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  0x00007ff87d4822eb in __pthread_cond_wait_common (abstime=0x0, mutex=0x7ff87e65af68, cond=0x7ff87e65af90) at pthread_cond_wait.c:502
#2  0x00007ff87d4822eb in __pthread_cond_wait (cond=0x7ff87e65af90, mutex=0x7ff87e65af68) at pthread_cond_wait.c:655
#3  0x00007ff87e563e2a in  () at /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#4  0x00007ff87e563e49 in  () at /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#5  0x00007ff87d47c164 in start_thread (arg=<optimized out>) at pthread_create.c:486
#6  0x00007ff8806a5def in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 3 (Thread 0x7ff86e429700 (LWP 3371)):
#0  0x00007ff87f037a92 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#1  0x00007ff87f0374c2 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007ff87efe716b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007ff87ee360b6 in QThread::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007ff87ccad1f5 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#5  0x00007ff87ee3fc87 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#6  0x00007ff87d47c164 in start_thread (arg=<optimized out>) at pthread_create.c:486
#7  0x00007ff8806a5def in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 2 (Thread 0x7ff86fa30700 (LWP 3324)):
#0  0x00007ff8806997d6 in __GI_ppoll (fds=0x7ff86800b468, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007ff87f036141 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007ff87f0375b9 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007ff87efe716b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007ff87ee360b6 in QThread::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007ff87c791545 in  () at /usr/lib/x86_64-linux-gnu/libQt5DBus.so.5
#6  0x00007ff87ee3fc87 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7  0x00007ff87d47c164 in start_thread (arg=<optimized out>) at pthread_create.c:486
#8  0x00007ff8806a5def in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 1 (Thread 0x7ff8756af840 (LWP 3281)):
[KCrash Handler]
#6  0x00007ff880260b34 in  () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#7  0x00007ff87e2cfb75 in KDecoration2::DecoratedClient::color(KDecoration2::ColorGroup, KDecoration2::ColorRole) const () at /usr/lib/x86_64-linux-gnu/libkdecorations2.so.5
#8  0x00007ff86e443a5e in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/org.kde.kdecoration2/breezedecoration.so
#9  0x00007ff88026becd in KWin::Decoration::Renderer::renderToImage(QRect const&) () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#10 0x00007ff86f00cd8f in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/org.kde.kwin.platforms/KWinX11Platform.so
#11 0x00007ff87f011830 in QMetaObject::activate(QObject*, int, int, void**) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#12 0x00007ff87f01d407 in QTimer::timeout(QTimer::QPrivateSignal) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#13 0x00007ff87f011f4b in QObject::event(QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#14 0x00007ff87f9a94a1 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#15 0x00007ff87f9b0ae0 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#16 0x00007ff87efe8499 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#17 0x00007ff87f039558 in QTimerInfoList::activateTimers() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#18 0x00007ff87f03770c in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#19 0x00007ff8750740ed in  () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#20 0x00007ff87efe716b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#21 0x00007ff87efef2e2 in QCoreApplication::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#22 0x00007ff88077ddbb in kdemain () at /usr/lib/x86_64-linux-gnu/libkdeinit5_kwin_x11.so
#23 0x00007ff8805af09b in __libc_start_main (main=0x55d3ee1ff730, argc=3, argv=0x7fff85464c08, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff85464bf8) at ../csu/libc-start.c:308
#24 0x000055d3ee1ff76a in _start ()
[Inferior 1 (process 3281) detached]

Reported using DrKonqi