Crash is caused by Aurorae decoration engine, which uses QtQuick.

Cannot reproduce. What themes do you have installed?

The crash is not reproducible, it happened just once.
I only have the default themes breeze, oxygen and plastik.

*** Bug 411376 has been marked as a duplicate of this bug. ***

*** Bug 411434 has been marked as a duplicate of this bug. ***

Patrick, now it happened (at least) twice. Maybe you can see a pattern, but it always involves the window decorations page.

*** Bug 411499 has been marked as a duplicate of this bug. ***

Sometimes I can reproduce this crash on Plasma 5.17 beta (on Wayland session), but the backtrace looks different.

Operating System: Arch Linux 
KDE Plasma Version: 5.16.90
KDE Frameworks Version: 5.62.0
Qt Version: 5.13.1
Kernel Version: 5.3.0-arch1-1-ARCH

open system settings > desktop behavior > desktop effects
click on "All settings" on top left corner
open "Application style"

if system settings did not crash, close it and repeat the steps above.
At some point probably it will crash.

Application: System Settings (systemsettings5), signal: Segmentation fault
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f3847625800 (LWP 8230))]

Thread 5 (Thread 0x7f38277bf700 (LWP 8257)):
#0  0x00007f384c2fd686 in __libc_disable_asynccancel () at /usr/lib/libc.so.6
#1  0x00007f384c2e567b in poll () at /usr/lib/libc.so.6
#2  0x00007f3848690130 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f381c00a080, timeout=<optimized out>, context=0x7f381c002540) at ../glib/glib/gmain.c:4216
#3  0x00007f3848690130 in g_main_context_iterate (context=context@entry=0x7f381c002540, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/glib/gmain.c:3912
#4  0x00007f3848690201 in g_main_context_iteration (context=0x7f381c002540, may_block=may_block@entry=1) at ../glib/glib/gmain.c:3978
#5  0x00007f384c889a1c in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f381c005070, flags=...) at kernel/qeventdispatcher_glib.cpp:425
#6  0x00007f384c8304ec in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7f38277bed80, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#7  0x00007f384c662385 in QThread::exec() (this=this@entry=0x55613cfb9d10) at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#8  0x00007f384b96d849 in QQmlThreadPrivate::run() (this=0x55613cfb9d10) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/ftw/qqmlthread.cpp:152
#9  0x00007f384c6635b0 in QThreadPrivate::start(void*) (arg=0x55613cfb9d10) at thread/qthread_unix.cpp:360
#10 0x00007f384aec457f in start_thread () at /usr/lib/libpthread.so.0
#11 0x00007f384c2f00e3 in clone () at /usr/lib/libc.so.6

Thread 4 (Thread 0x7f38369dc700 (LWP 8234)):
#0  0x00007f384c2e118c in read () at /usr/lib/libc.so.6
#1  0x00007f38486409f0 in read (__nbytes=16, __buf=0x7f38369dbb60, __fd=<optimized out>, __fd=<optimized out>, __buf=<optimized out>, __nbytes=<optimized out>) at /usr/include/bits/unistd.h:44
#2  0x00007f38486409f0 in g_wakeup_acknowledge (wakeup=0x7f3840003db0) at ../glib/glib/gwakeup.c:210
#3  0x00007f384868e9f1 in g_main_context_check (context=context@entry=0x7f3830000bf0, max_priority=2147483647, fds=fds@entry=0x7f3830004e30, n_fds=n_fds@entry=1) at ../glib/glib/gmain.c:3695
#4  0x00007f38486900d8 in g_main_context_iterate (context=context@entry=0x7f3830000bf0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/glib/gmain.c:3914
#5  0x00007f3848690201 in g_main_context_iteration (context=0x7f3830000bf0, may_block=may_block@entry=1) at ../glib/glib/gmain.c:3978
#6  0x00007f384c889a1c in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f3830000b20, flags=...) at kernel/qeventdispatcher_glib.cpp:425
#7  0x00007f384c8304ec in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7f38369dbd80, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#8  0x00007f384c662385 in QThread::exec() (this=this@entry=0x55613738a1b0) at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#9  0x00007f384b96d849 in QQmlThreadPrivate::run() (this=0x55613738a1b0) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/ftw/qqmlthread.cpp:152
#10 0x00007f384c6635b0 in QThreadPrivate::start(void*) (arg=0x55613738a1b0) at thread/qthread_unix.cpp:360
#11 0x00007f384aec457f in start_thread () at /usr/lib/libpthread.so.0
#12 0x00007f384c2f00e3 in clone () at /usr/lib/libc.so.6

Thread 3 (Thread 0x7f3844913700 (LWP 8233)):
#0  0x00007f384aeca415 in pthread_cond_wait@@GLIBC_2.3.2 () at /usr/lib/libpthread.so.0
#1  0x00007f383f57bf5c in  () at /usr/lib/dri/i965_dri.so
#2  0x00007f383f57bb58 in  () at /usr/lib/dri/i965_dri.so
#3  0x00007f384aec457f in start_thread () at /usr/lib/libpthread.so.0
#4  0x00007f384c2f00e3 in clone () at /usr/lib/libc.so.6

Thread 2 (Thread 0x7f384639e700 (LWP 8232)):
#0  0x00007f384c2e5667 in poll () at /usr/lib/libc.so.6
#1  0x00007f3848690130 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f3840005260, timeout=<optimized out>, context=0x7f3840000bf0) at ../glib/glib/gmain.c:4216
#2  0x00007f3848690130 in g_main_context_iterate (context=context@entry=0x7f3840000bf0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/glib/gmain.c:3912
#3  0x00007f3848690201 in g_main_context_iteration (context=0x7f3840000bf0, may_block=may_block@entry=1) at ../glib/glib/gmain.c:3978
#4  0x00007f384c889a1c in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f3840000b20, flags=...) at kernel/qeventdispatcher_glib.cpp:425
#5  0x00007f384c8304ec in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7f384639dd70, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#6  0x00007f384c662385 in QThread::exec() (this=this@entry=0x7f384cb46080 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#7  0x00007f384cac2b37 in QDBusConnectionManager::run() (this=0x7f384cb46080 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at qdbusconnection.cpp:178
#8  0x00007f384c6635b0 in QThreadPrivate::start(void*) (arg=0x7f384cb46080 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at thread/qthread_unix.cpp:360
#9  0x00007f384aec457f in start_thread () at /usr/lib/libpthread.so.0
#10 0x00007f384c2f00e3 in clone () at /usr/lib/libc.so.6

Thread 1 (Thread 0x7f3847625800 (LWP 8230)):
[KCrash Handler]
#6  0x00007f384c6dda96 in std::__atomic_base<QtSharedPointer::ExternalRefCountData*>::load(std::memory_order) const (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/9.1.0/bits/atomic_base.h:734
#7  0x00007f384c6dda96 in std::atomic<QtSharedPointer::ExternalRefCountData*>::load(std::memory_order) const (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/9.1.0/atomic:519
#8  0x00007f384c6dda96 in QAtomicOps<QtSharedPointer::ExternalRefCountData*>::load<QtSharedPointer::ExternalRefCountData*>(std::atomic<QtSharedPointer::ExternalRefCountData*> const&) (_q_value=...) at ../../include/QtCore/../../src/corelib/thread/qatomic_cxx11.h:227
#9  0x00007f384c6dda96 in QBasicAtomicPointer<QtSharedPointer::ExternalRefCountData>::load() const (this=<optimized out>) at ../../include/QtCore/../../src/corelib/thread/qbasicatomic.h:239
#10 0x00007f384c6dda96 in QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) (obj=obj@entry=0x3) at tools/qsharedpointer.cpp:1347
#11 0x00007f384b938408 in QWeakPointer<QObject>::QWeakPointer<QObject>(QObject*, bool) (ptr=0x3, this=<optimized out>) at /usr/include/qt/QtCore/qsharedpointer_impl.h:688
#12 0x00007f384b938408 in QWeakPointer<QObject>::assign<QObject>(QObject*) (ptr=0x3, this=0x556140261bd0) at /usr/include/qt/QtCore/qsharedpointer_impl.h:684
#13 0x00007f384b938408 in QPointer<QObject>::operator=(QObject*) (p=0x3, this=0x556140261bd0) at /usr/include/qt/QtCore/qpointer.h:83
#14 0x00007f384b938408 in QQmlListReferencePrivate::init(QQmlListProperty<QObject> const&, int, QQmlEngine*) (prop=..., propType=1951, engine=<optimized out>) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmllist.cpp:64
#15 0x00007f384b946632 in QV4::QmlListWrapper::toVariant() const (this=<optimized out>) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmllistwrapper_p.h:87
#16 0x00007f384b886b26 in toVariant(QV4::ExecutionEngine*, QV4::Value const&, int, bool, V4ObjectSet*) (e=e@entry=0x5561402d9270, value=..., typeHint=typeHint@entry=2, createJSValueForObjects=createJSValueForObjects@entry=true, visitedObjects=visitedObjects@entry=0x0) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/jsruntime/qv4engine.cpp:1316
#17 0x00007f384b886fa5 in QV4::ExecutionEngine::toVariant(QV4::Value const&, int, bool) (this=this@entry=0x5561402d9270, value=..., typeHint=typeHint@entry=2, createJSValueForObjects=createJSValueForObjects@entry=true) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/jsruntime/qv4engine.cpp:1281
#18 0x00007f384b941260 in QQmlBinding::slowWrite(QQmlPropertyData const&, QQmlPropertyData const&, QV4::Value const&, bool, QFlags<QQmlPropertyData::WriteFlag>) (this=this@entry=0x55613cd62800, core=..., valueTypeData=..., result=..., isUndefined=isUndefined@entry=false, flags=..., flags@entry=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlbinding.cpp:415
#19 0x00007f384b9430a1 in GenericBinding<2>::write(QV4::Value const&, bool, QFlags<QQmlPropertyData::WriteFlag>) (this=0x55613cd62800, result=..., isUndefined=<optimized out>, flags=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/include/QtQml/5.13.1/QtQml/private/../../../../../src/qml/jsruntime/qv4value_p.h:297
#20 0x00007f384b943c5d in QQmlNonbindingBinding::doUpdate(QQmlJavaScriptExpression::DeleteWatcher const&, QFlags<QQmlPropertyData::WriteFlag>, QV4::Scope&) (this=0x55613cd62800, watcher=..., flags=..., scope=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/include/QtQml/5.13.1/QtQml/private/../../../../../src/qml/jsruntime/qv4scopedvalue_p.h:239
#21 0x00007f384b9403a4 in QQmlBinding::update(QFlags<QQmlPropertyData::WriteFlag>) (this=0x55613cd62800, flags=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlbinding.cpp:185
#22 0x00007f384b94eebe in QQmlObjectCreator::finalize(QQmlInstantiationInterrupt&) (this=0x5561401bf040, interrupt=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlobjectcreator.cpp:1383
#23 0x00007f384b8cf732 in QQmlComponentPrivate::complete(QQmlEnginePrivate*, QQmlComponentPrivate::ConstructionState*) (state=0x5561401befa0, enginePriv=0x55613d58ea50) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlcomponent.cpp:935
#24 0x00007f384b8cf732 in QQmlComponentPrivate::complete(QQmlEnginePrivate*, QQmlComponentPrivate::ConstructionState*) (enginePriv=0x55613d58ea50, state=0x5561401befa0) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlcomponent.cpp:931
#25 0x00007f384b8cf854 in QQmlComponentPrivate::completeCreate() (this=0x5561401bef00) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlcomponent.cpp:971
#26 0x00007f384b8cf854 in QQmlComponentPrivate::completeCreate() (this=0x5561401bef00) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlcomponent.cpp:966
#27 0x00007f384b8cf636 in QQmlComponent::create(QQmlContext*) (this=0x5561401beb80, context=0x55613cfb8e10) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlcomponent.cpp:797
#28 0x00007f382c1dce2b in  () at /usr/lib/qt/plugins/org.kde.kdecoration2/kwin5_aurorae.so
#29 0x00007f382f0a154c in  () at /usr/lib/qt/qml/org/kde/kwin/private/kdecoration/libkdecorationprivatedeclarative.so
#30 0x00007f384b94f09d in QQmlObjectCreator::finalize(QQmlInstantiationInterrupt&) (this=0x556143b507d0, interrupt=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlobjectcreator.cpp:1403
#31 0x00007f384b8d4acb in QQmlIncubatorPrivate::incubate(QQmlInstantiationInterrupt&) (this=0x55613cdc4aa0, i=...) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlincubator.cpp:345
#32 0x00007f384b8d5033 in QQmlEnginePrivate::incubate(QQmlIncubator&, QQmlContextData*) (this=0x556137372e60, i=..., forContext=<optimized out>) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/qml/qqmlincubator.cpp:89
#33 0x00007f384b9bf290 in QQmlDelegateModelPrivate::object(QQmlListCompositor::Group, int, QQmlIncubator::IncubationMode) (this=0x5561373857e0, group=QQmlListCompositor::Default, index=2, incubationMode=<optimized out>) at /usr/include/c++/9.1.0/bits/atomic_base.h:413
#34 0x00007f384b9bf435 in QQmlDelegateModel::object(int, QQmlIncubator::IncubationMode) (this=<optimized out>, index=2, incubationMode=QQmlIncubator::AsynchronousIfNested) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/types/qqmldelegatemodel.cpp:1114
#35 0x00007f384be16336 in QQuickItemViewPrivate::createItem(int, QQmlIncubator::IncubationMode) (this=this@entry=0x55613d634590, modelIndex=modelIndex@entry=2, incubationMode=incubationMode@entry=QQmlIncubator::AsynchronousIfNested) at /usr/include/c++/9.1.0/bits/atomic_base.h:413
#36 0x00007f384be09f5e in QQuickGridViewPrivate::addVisibleItems(double, double, double, double, bool) (this=0x55613d634590, fillFrom=-0, fillTo=331, bufferFrom=<optimized out>, bufferTo=651, doBuffer=false) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/quick/items/qquickgridview.cpp:520
#37 0x00007f384be17594 in QQuickItemViewPrivate::refill(double, double) (this=0x55613d634590, from=-0, to=331) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/quick/items/qquickitemview.cpp:1751
#38 0x00007f384be1a1f1 in QQuickItemViewPrivate::regenerate(bool) (orientationChanged=<optimized out>, this=0x55613d634590) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/quick/items/qquickitemview.cpp:1797
#39 0x00007f384be1a1f1 in QQuickItemViewPrivate::regenerate(bool) (this=0x55613d634590, orientationChanged=<optimized out>) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/quick/items/qquickitemview.cpp:1782
#40 0x00007f384be1a39d in QQuickItemView::modelUpdated(QQmlChangeSet const&, bool) (this=0x55613ccd8a60, changeSet=..., reset=<optimized out>) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/quick/items/qquickitemview.cpp:1199
#41 0x00007f384be1b87d in QQuickItemView::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at .moc/moc_qquickitemview_p.cpp:541
#42 0x00007f384c85da11 in QMetaObject::activate(QObject*, int, int, void**) (sender=0x55613cd37440, signalOffset=<optimized out>, local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3809
#43 0x00007f384b997ea7 in QQmlInstanceModel::modelUpdated(QQmlChangeSet const&, bool) (this=this@entry=0x55613cd37440, _t1=..., _t2=<optimized out>) at .moc/moc_qqmlobjectmodel_p.cpp:226
#44 0x00007f384b9b4389 in QQmlDelegateModelPrivate::emitModelUpdated(QQmlChangeSet const&, bool) (this=<optimized out>, changeSet=..., reset=<optimized out>) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/types/qqmldelegatemodel.cpp:1578
#45 0x00007f384b9bb362 in QQmlDelegateModelGroupPrivate::emitModelUpdated(bool) (this=0x55613cd376c0, reset=reset@entry=true) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/types/qqmldelegatemodel.cpp:2456
#46 0x00007f384b9bb778 in QQmlDelegateModelPrivate::emitChanges() (this=0x5561373857e0) at /usr/include/qt/QtCore/qobject.h:122
#47 0x00007f384b9bb778 in QQmlDelegateModelPrivate::emitChanges() (this=0x5561373857e0) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/types/qqmldelegatemodel.cpp:1609
#48 0x00007f384b9c583a in QQmlDelegateModel::_q_modelReset() (this=0x55613cd37440) at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-everywhere-src-5.13.1/src/qml/types/qqmldelegatemodel.cpp:1668
#49 0x00007f384b9c5db9 in QQmlDelegateModel::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=_o@entry=0x55613cd37440, _c=_c@entry=QMetaObject::InvokeMetaMethod, _id=_id@entry=7, _a=_a@entry=0x7ffd654f1c20) at .moc/moc_qqmldelegatemodel_p.cpp:198
#50 0x00007f384b9c6163 in QQmlDelegateModel::qt_metacall(QMetaObject::Call, int, void**) (this=0x55613cd37440, _c=QMetaObject::InvokeMetaMethod, _id=7, _a=0x7ffd654f1c20) at .moc/moc_qqmldelegatemodel_p.cpp:335
#51 0x00007f384c85dacd in QMetaObject::activate(QObject*, int, int, void**) (sender=0x5561402e3050, signalOffset=<optimized out>, local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3825
#52 0x00007f384c7d4b5b in QAbstractItemModel::modelReset(QAbstractItemModel::QPrivateSignal) (this=this@entry=0x5561402e3050, _t1=...) at .moc/moc_qabstractitemmodel.cpp:648
#53 0x00007f384c7d6bfe in QAbstractItemModel::endResetModel() (this=this@entry=0x5561402e3050) at itemmodels/qabstractitemmodel.cpp:3271
#54 0x00007f384c8055c5 in QSortFilterProxyModelPrivate::_q_sourceReset() (this=0x55613d1cc5f0) at itemmodels/qsortfilterproxymodel.cpp:1546
#55 0x00007f384c809ed8 in QSortFilterProxyModel::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at itemmodels/qsortfilterproxymodel.h:189
#56 0x00007f384c85da11 in QMetaObject::activate(QObject*, int, int, void**) (sender=0x5561374b5eb0, signalOffset=<optimized out>, local_signal_index=<optimized out>, argv=<optimized out>) at kernel/qobject.cpp:3809
#57 0x00007f384c7d4b5b in QAbstractItemModel::modelReset(QAbstractItemModel::QPrivateSignal) (this=<optimized out>, _t1=...) at .moc/moc_qabstractitemmodel.cpp:648
#58 0x00007f382f0d44f8 in  () at /usr/lib/qt/plugins/kcms/kcm_kwindecoration.so
#59 0x00007f384c85e44a in QObject::event(QEvent*) (this=0x5561374b5eb0, e=<optimized out>) at kernel/qobject.cpp:1260
#60 0x00007f384d2904f5 in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=this@entry=0x556136e1a620, receiver=receiver@entry=0x5561374b5eb0, e=e@entry=0x556143e55b30) at kernel/qapplication.cpp:3703
#61 0x00007f384d299e11 in QApplication::notify(QObject*, QEvent*) (this=0x7ffd654f2610, receiver=0x5561374b5eb0, e=0x556143e55b30) at kernel/qapplication.cpp:3449
#62 0x00007f384c8319c2 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x5561374b5eb0, event=0x556143e55b30) at ../../include/QtCore/../../src/corelib/kernel/qobject.h:143
#63 0x00007f384c834739 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (receiver=0x0, event_type=0, data=0x556136e11b80) at kernel/qcoreapplication.cpp:1840
#64 0x00007f384c88a404 in postEventSourceDispatch(GSource*, GSourceFunc, gpointer) (s=0x556136e5ee80) at kernel/qeventdispatcher_glib.cpp:277
#65 0x00007f384868e3ae in g_main_dispatch (context=0x556136e46630) at ../glib/glib/gmain.c:3179
#66 0x00007f384868e3ae in g_main_context_dispatch (context=context@entry=0x556136e46630) at ../glib/glib/gmain.c:3844
#67 0x00007f38486901c1 in g_main_context_iterate (context=context@entry=0x556136e46630, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/glib/gmain.c:3917
#68 0x00007f3848690201 in g_main_context_iteration (context=0x556136e46630, may_block=may_block@entry=1) at ../glib/glib/gmain.c:3978
#69 0x00007f384c889a03 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x556136e5e300, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#70 0x00007f384c8304ec in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7ffd654f2530, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#71 0x00007f384c838326 in QCoreApplication::exec() () at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#72 0x0000556134e5b475 in  ()
#73 0x00007f384c21aee3 in __libc_start_main () at /usr/lib/libc.so.6
#74 0x0000556134e5b4fe in _start ()
[Inferior 1 (process 8230) detached]

Created attachment 123366 [details]
New crash information added by DrKonqi

systemsettings5 (5.17.80) using Qt 5.13.1

- What I was doing when the application crashed:

System Settings crashes when I click on "Application Style"

-- Backtrace (Reduced):
#6  std::__atomic_base<QtSharedPointer::ExternalRefCountData*>::load (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/7/bits/atomic_base.h:713
#7  std::atomic<QtSharedPointer::ExternalRefCountData*>::load (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/7/atomic:452
#8  QAtomicOps<QtSharedPointer::ExternalRefCountData*>::load<QtSharedPointer::ExternalRefCountData*> (_q_value=...) at ../../include/QtCore/../../src/corelib/thread/qatomic_cxx11.h:227
#9  QBasicAtomicPointer<QtSharedPointer::ExternalRefCountData>::load (this=<optimized out>) at ../../include/QtCore/../../src/corelib/thread/qbasicatomic.h:239
#10 QtSharedPointer::ExternalRefCountData::getAndRef (obj=obj@entry=0x3) at tools/qsharedpointer.cpp:1347

Created attachment 123675 [details]
New crash information added by DrKonqi

systemsettings5 (5.17.2) using Qt 5.13.1

When I was changing on window management the settings application closed.

-- Backtrace (Reduced):
#6  std::__atomic_base<QtSharedPointer::ExternalRefCountData*>::load (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/7/bits/atomic_base.h:713
#7  std::atomic<QtSharedPointer::ExternalRefCountData*>::load (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/7/atomic:452
#8  QAtomicOps<QtSharedPointer::ExternalRefCountData*>::load<QtSharedPointer::ExternalRefCountData*> (_q_value=...) at ../../include/QtCore/../../src/corelib/thread/qatomic_cxx11.h:227
#9  QBasicAtomicPointer<QtSharedPointer::ExternalRefCountData>::load (this=<optimized out>) at ../../include/QtCore/../../src/corelib/thread/qbasicatomic.h:239
#10 QtSharedPointer::ExternalRefCountData::getAndRef (obj=obj@entry=0x3) at tools/qsharedpointer.cpp:1347

Created attachment 123733 [details]
New crash information added by DrKonqi

systemsettings5 (5.12.8) using Qt 5.9.7

- What I was doing when the application crashed:

After a fresh install of opensuse leap 15.1, I was quickly going through settings, when clicking application style the system settings crashed.

-- Backtrace (Reduced):
#6  std::__atomic_base<QtSharedPointer::ExternalRefCountData*>::load (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/7/bits/atomic_base.h:713
#7  std::atomic<QtSharedPointer::ExternalRefCountData*>::load (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/7/atomic:452
#8  QAtomicOps<QtSharedPointer::ExternalRefCountData*>::load<QtSharedPointer::ExternalRefCountData*> (_q_value=...) at ../../include/QtCore/../../src/corelib/arch/qatomic_cxx11.h:227
#9  QBasicAtomicPointer<QtSharedPointer::ExternalRefCountData>::load (this=<optimized out>) at ../../include/QtCore/../../src/corelib/thread/qbasicatomic.h:238
#10 QtSharedPointer::ExternalRefCountData::getAndRef (obj=obj@entry=0x3) at tools/qsharedpointer.cpp:1445

Created attachment 123965 [details]
New crash information added by DrKonqi

systemsettings5 (5.17.3) using Qt 5.12.5

- What I was doing when the application crashed:
I was using Plasma 5.17.3 on Wayland in Fedora 31. I opened System Settings. I clicked on Global Theme, Plasma Style, Application Style GNOME/GTK application style, then Window Decorations. System Settings disappeared after I clicked Window Decorations. System Settings had a segmentation fault in std::__atomic_base<QtSharedPointer::ExternalRefCountData*>::load at /usr/include/c++/9/bits/atomic_base.h:734.
The crashes occurred 2/4 times I've tried to click on Window Decorations.

-- Backtrace (Reduced):
#6  0x00007fdc6f2246aa in std::__atomic_base<QtSharedPointer::ExternalRefCountData*>::load(std::memory_order) const (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/9/bits/atomic_base.h:734
#7  std::atomic<QtSharedPointer::ExternalRefCountData*>::load(std::memory_order) const (__m=std::memory_order_relaxed, this=<optimized out>) at /usr/include/c++/9/atomic:519
#8  QAtomicOps<QtSharedPointer::ExternalRefCountData*>::load<QtSharedPointer::ExternalRefCountData*>(std::atomic<QtSharedPointer::ExternalRefCountData*> const&) (_q_value=...) at ../../include/QtCore/../../src/corelib/thread/qatomic_cxx11.h:227
#9  QBasicAtomicPointer<QtSharedPointer::ExternalRefCountData>::load() const (this=<optimized out>) at ../../include/QtCore/../../src/corelib/thread/qbasicatomic.h:239
#10 QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) (obj=obj@entry=0x3) at tools/qsharedpointer.cpp:1358

Created attachment 124037 [details]
valgrind log file for system settings segmentation fault

I ran valgrind --log-file=valgrind-systemsettings5-2.txt systemsettings5 &
I reproduced the crash in the same way as in my previous comment. The valgrind log showed an invalid read in wl_proxy_unref at wayland-client.c:229 and an invalid write in wl_proxy_unref at wayland-client.c:230 in libwayland-client. They appeared to be use-after-free errors like those I've previously reported for kwin_wayland, plasmashell, konsole, powerdevil, etc. ( https://bugs.kde.org/show_bug.cgi?id=409688 ) Several Conditional jump or move depends on uninitialised value(s) messages were shown. An invalid read at in load at atomic_base.h:740 of the address 0xb was shown which had a similar trace similar to that of the crashing threads.

==4968== Invalid read of size 8
==4968==    at 0x5D136AA: load (atomic_base.h:740)
==4968==    by 0x5D136AA: load (atomic:519)
==4968==    by 0x5D136AA: load<QtSharedPointer::ExternalRefCountData*> (qatomic_cxx11.h:227)
==4968==    by 0x5D136AA: load (qbasicatomic.h:239)
==4968==    by 0x5D136AA: QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) (qsharedpointer.cpp:1358)
==4968==    by 0x6ECFCF7: QWeakPointer<QObject> (qsharedpointer_impl.h:688)
==4968==    by 0x6ECFCF7: assign<QObject> (qsharedpointer_impl.h:684)
==4968==    by 0x6ECFCF7: operator= (qpointer.h:83)
==4968==    by 0x6ECFCF7: QQmlListReferencePrivate::init(QQmlListProperty<QObject> const&, int, QQmlEngine*) (qqmllist.cpp:64)
==4968==    by 0x6EDE064: QV4::QmlListWrapper::toVariant() const (qqmllistwrapper.cpp:101)
==4968==    by 0x6E20603: toVariant(QV4::ExecutionEngine*, QV4::Value const&, int, bool, QSet<QV4::Heap::Object*>*) (qv4engine.cpp:1306)
==4968==    by 0x6E20A68: QV4::ExecutionEngine::toVariant(QV4::Value const&, int, bool) (qv4engine.cpp:1271)
==4968==    by 0x6ED8B24: QQmlBinding::slowWrite(QQmlPropertyData const&, QQmlPropertyData const&, QV4::Value const&, bool, QFlags<QQmlPropertyData::WriteFlag>) (qqmlbinding.cpp:415)
==4968==    by 0x6EDA8F2: GenericBinding<2>::write(QV4::Value const&, bool, QFlags<QQmlPropertyData::WriteFlag>) (qqmlbinding.cpp:325)
==4968==    by 0x6EDB53F: QQmlNonbindingBinding::doUpdate(QQmlJavaScriptExpression::DeleteWatcher const&, QFlags<QQmlPropertyData::WriteFlag>, QV4::Scope&) (qqmlbinding.cpp:249)
==4968==    by 0x6ED7C93: QQmlBinding::update(QFlags<QQmlPropertyData::WriteFlag>) (qqmlbinding.cpp:185)
==4968==    by 0x6EE6825: QQmlObjectCreator::finalize(QQmlInstantiationInterrupt&) (qqmlobjectcreator.cpp:1352)
==4968==    by 0x6E65F80: complete (qqmlcomponent.cpp:935)
==4968==    by 0x6E65F80: QQmlComponentPrivate::complete(QQmlEnginePrivate*, QQmlComponentPrivate::ConstructionState*) (qqmlcomponent.cpp:931)
==4968==    by 0x6E66091: completeCreate (qqmlcomponent.cpp:971)
==4968==    by 0x6E66091: QQmlComponentPrivate::completeCreate() (qqmlcomponent.cpp:966)
==4968==  Address 0xb is not stack'd, malloc'd or (recently) free'd
==4968== 

This crash might be due to an invalid pointer from the earlier use-after-free errors and use of uninitialized variables. Two further invalid reads were shown in socketNotifierSourceCheck at qeventdispatcher_glib.cpp:88 which look like use-after-free errors. Those errors might be side-effects of the segmentation fault. I've seen this crash 9 times which is about half the times I've tried to reproduce it. I'm attaching the full valgrind log.

*** This bug has been marked as a duplicate of bug 390857 ***