Application: systemsettings5 (5.10.90)
 (Compiled from sources)
Qt Version: 5.9.0
Frameworks Version: 5.35.0
Operating System: Linux 4.11.4-gentoo x86_64
Distribution: "Gentoo Base System release 2.3"

-- Information about the crash:
- What I was doing when the application crashed:

When I try to open style config window, kcmshell5 crashes:

1. run "kcmshell5 style"
2. Ensure QtCurve style is selected.
3. Click "Configure"  button.

The crash can be reproduced every time.

-- Backtrace:
Application: System Settings (systemsettings5), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f1c9a2095c0 (LWP 32370))]

Thread 3 (Thread 0x7f1c8b0be700 (LWP 32373)):
#0  0x00007f1ca628508d in poll () from /lib64/libc.so.6
#1  0x00007f1c9ee2f346 in g_main_context_iterate.isra () from /usr/lib64/libglib-2.0.so.0
#2  0x00007f1c9ee2f44c in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#3  0x00007f1ca70ef9eb in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Core.so.5
#4  0x00007f1ca709e03a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Core.so.5
#5  0x00007f1ca6ef91da in QThread::exec() () from /usr/lib64/libQt5Core.so.5
#6  0x00007f1cab241629 in QDBusConnectionManager::run() () from /usr/lib64/libQt5DBus.so.5
#7  0x00007f1ca6efd2d2 in QThreadPrivate::start(void*) () from /usr/lib64/libQt5Core.so.5
#8  0x00007f1ca338a374 in start_thread () from /lib64/libpthread.so.0
#9  0x00007f1ca628e43f in clone () from /lib64/libc.so.6

Thread 2 (Thread 0x7f1c97b04700 (LWP 32372)):
#0  0x00007f1ca628508d in poll () from /lib64/libc.so.6
#1  0x00007f1ca39c860f in _xcb_conn_wait () from /usr/lib64/libxcb.so.1
#2  0x00007f1ca39d08c9 in xcb_wait_for_event () from /usr/lib64/libxcb.so.1
#3  0x00007f1c99a39bb9 in QXcbEventReader::run() () from /usr/lib64/libQt5XcbQpa.so.5
#4  0x00007f1ca6efd2d2 in QThreadPrivate::start(void*) () from /usr/lib64/libQt5Core.so.5
#5  0x00007f1ca338a374 in start_thread () from /lib64/libpthread.so.0
#6  0x00007f1ca628e43f in clone () from /lib64/libc.so.6

Thread 1 (Thread 0x7f1c9a2095c0 (LWP 32370)):
[KCrash Handler]
#6  0x00007f1ca7ff6af5 in QWindow::winId() const () from /usr/lib64/libQt5Gui.so.5
#7  0x00007f1c96eb1f5d in QDBusMenuBar::unregisterMenuBar (this=this@entry=0x1f7cd60) at /usr/src/debug/kde-plasma/plasma-integration-9999/plasma-integration-9999/src/platformtheme/qdbusmenubar.cpp:179
#8  0x00007f1c96eb256f in QDBusMenuBar::handleReparent (this=0x1f7cd60, newParentWindow=0x24225b0) at /usr/src/debug/kde-plasma/plasma-integration-9999/plasma-integration-9999/src/platformtheme/qdbusmenubar.cpp:128
#9  0x00007f1ca866e73b in QMenuBarPrivate::handleReparent() () from /usr/lib64/libQt5Widgets.so.5
#10 0x00007f1ca866f2c8 in QMenuBar::eventFilter(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#11 0x00007f1ca709ee0c in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) () from /usr/lib64/libQt5Core.so.5
#12 0x00007f1ca8503cd5 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#13 0x00007f1ca850b534 in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#14 0x00007f1ca709f077 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib64/libQt5Core.so.5
#15 0x00007f1ca8545c1a in QWidget::setParent(QWidget*, QFlags<Qt::WindowType>) () from /usr/lib64/libQt5Widgets.so.5
#16 0x00007f1ca8520a1e in QLayout::addChildWidget(QWidget*) () from /usr/lib64/libQt5Widgets.so.5
#17 0x00007f1ca8520abf in QLayout::addWidget(QWidget*) () from /usr/lib64/libQt5Widgets.so.5
#18 0x00007f1ca86537cc in QMdiSubWindow::setWidget(QWidget*) () from /usr/lib64/libQt5Widgets.so.5
#19 0x00007f1ca8647493 in QMdiArea::addSubWindow(QWidget*, QFlags<Qt::WindowType>) () from /usr/lib64/libQt5Widgets.so.5
#20 0x00007f1c82853a1f in QtCurveConfig::previewControlPressed (this=0x2909bc0) at /usr/src/debug/x11-themes/qtcurve-9999/qtcurve-9999/qt5/config/qtcurveconfig.cpp:2219
#21 0x00007f1c82850493 in QtCurveConfig::setupPreview (this=0x2909bc0) at /usr/src/debug/x11-themes/qtcurve-9999/qtcurve-9999/qt5/config/qtcurveconfig.cpp:1786
#22 0x00007f1c8284c912 in QtCurveConfig::QtCurveConfig (this=0x2909bc0, parent=0x244cf80) at /usr/src/debug/x11-themes/qtcurve-9999/qtcurve-9999/qt5/config/qtcurveconfig.cpp:1222
#23 0x00007f1c82842e69 in allocate_kstyle_config (parent=0x244cf80) at /usr/src/debug/x11-themes/qtcurve-9999/qtcurve-9999/qt5/config/qtcurveconfig.cpp:106
#24 0x00007f1c8331ecd3 in KCMStyle::styleSpecificConfig() () from /usr/lib64/qt5/plugins/kcm_style.so
#25 0x00007f1ca70c7ca7 in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib64/libQt5Core.so.5
#26 0x00007f1ca86c5d52 in QAbstractButton::clicked(bool) () from /usr/lib64/libQt5Widgets.so.5
#27 0x00007f1ca86c5f6a in QAbstractButtonPrivate::emitClicked() () from /usr/lib64/libQt5Widgets.so.5
#28 0x00007f1ca86c736d in QAbstractButtonPrivate::click() () from /usr/lib64/libQt5Widgets.so.5
#29 0x00007f1ca86c7564 in QAbstractButton::mouseReleaseEvent(QMouseEvent*) () from /usr/lib64/libQt5Widgets.so.5
#30 0x00007f1ca8544858 in QWidget::event(QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#31 0x00007f1ca8503cfc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#32 0x00007f1ca850ba8f in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#33 0x00007f1ca709f077 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib64/libQt5Core.so.5
#34 0x00007f1ca850aa62 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /usr/lib64/libQt5Widgets.so.5
#35 0x00007f1ca855f36b in QWidgetWindow::handleMouseEvent(QMouseEvent*) () from /usr/lib64/libQt5Widgets.so.5
#36 0x00007f1ca85619af in QWidgetWindow::event(QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#37 0x00007f1ca8503cfc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#38 0x00007f1ca850b534 in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#39 0x00007f1ca709f077 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib64/libQt5Core.so.5
#40 0x00007f1ca7fed0ab in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) () from /usr/lib64/libQt5Gui.so.5
#41 0x00007f1ca7feec95 in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) () from /usr/lib64/libQt5Gui.so.5
#42 0x00007f1ca7fc936b in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Gui.so.5
#43 0x00007f1c99a9c2c0 in userEventSourceDispatch(_GSource*, int (*)(void*), void*) () from /usr/lib64/libQt5XcbQpa.so.5
#44 0x00007f1c9ee2f177 in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#45 0x00007f1c9ee2f3a8 in g_main_context_iterate.isra () from /usr/lib64/libglib-2.0.so.0
#46 0x00007f1c9ee2f44c in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#47 0x00007f1ca70ef9cf in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Core.so.5
#48 0x00007f1ca709e03a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Core.so.5
#49 0x00007f1ca70a6324 in QCoreApplication::exec() () from /usr/lib64/libQt5Core.so.5
#50 0x000000000040b5da in main ()

Reported using DrKonqi