Arch Linux

Description:
After upgrading to 5.14.1-1, most Qt5 applications crash with segfault under Plasma 5.17.90 (kde-unstable), including qdbusviewer.

Additional info:
* package version(s)
* config and/or log files etc.
* link to upstream bug report, if any

qt5-{base,...} 5.14.1-1

% gdb qdbusviewer
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Reading symbols from qdbusviewer...
(No debugging symbols found in qdbusviewer)
(gdb) r
Starting program: /usr/bin/qdbusviewer
/usr/lib/../share/gcc-9.2.0/python/libstdcxx/v6/xmethods.py:731: SyntaxWarning: list indices must be integers or slices, not str; perhaps you missed a comma?
refcounts = ['_M_refcount']['_M_pi']
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[New Thread 0x7ffff2897700 (LWP 2195754)]
[New Thread 0x7fffeba38700 (LWP 2195755)]

Thread 1 "qdbusviewer" received signal SIGSEGV, Segmentation fault.
0x00007ffff6d21173 in QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) () from /usr/lib/libQt5Core.so.5
(gdb) thread apply all bt

Thread 3 (Thread 0x7fffeba38700 (LWP 2195755)):
#0 0x00007ffff69569ef in poll () from /usr/lib/libc.so.6
#1 0x00007ffff5d20120 in ?? () from /usr/lib/libglib-2.0.so.0
#2 0x00007ffff5d201f1 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#3 0x00007ffff6f13020 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#4 0x00007ffff6eb94cc in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#5 0x00007ffff6cdde52 in QThread::exec() () from /usr/lib/libQt5Core.so.5
#6 0x00007ffff71a5b28 in ?? () from /usr/lib/libQt5DBus.so.5
#7 0x00007ffff6cdefc6 in ?? () from /usr/lib/libQt5Core.so.5
#8 0x00007ffff68494cf in start_thread () from /usr/lib/libpthread.so.0
#9 0x00007ffff69612d3 in clone () from /usr/lib/libc.so.6

Thread 2 (Thread 0x7ffff2897700 (LWP 2195754)):
#0 0x00007ffff69569ef in poll () from /usr/lib/libc.so.6
#1 0x00007ffff3ca6630 in ?? () from /usr/lib/libxcb.so.1
#2 0x00007ffff3ca82db in xcb_wait_for_event () from /usr/lib/libxcb.so.1
#3 0x00007ffff3449b81 in ?? () from /usr/lib/libQt5XcbQpa.so.5
#4 0x00007ffff6cdefc6 in ?? () from /usr/lib/libQt5Core.so.5
#5 0x00007ffff68494cf in start_thread () from /usr/lib/libpthread.so.0
#6 0x00007ffff69612d3 in clone () from /usr/lib/libc.so.6

Thread 1 (Thread 0x7ffff3c87c80 (LWP 2195738)):
#0 0x00007ffff6d21173 in QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) () from /usr/lib/libQt5Core.so.5
#1 0x00007ffff2033ea6 in ?? () from /usr/lib/qt/plugins/styles/breeze.so
#2 0x00007fffe4018640 in ?? ()
#3 0x00007ffff1891757 in ?? () from /usr/lib/libKF5ConfigWidgets.so.5
#4 0x00007ffff1892119 in KColorScheme::KColorScheme(QPalette::ColorGroup, KColorScheme::ColorSet, QExplicitlySharedDataPointer<KSharedConfig>) () from /usr/lib/libKF5ConfigWidgets.so.5
#5 0x00007ffff1893219 in KStatefulBrush::KStatefulBrush(KColorScheme::ColorSet, KColorScheme::DecorationRole, QExplicitlySharedDataPointer<KSharedConfig>) () from /usr/lib/libKF5ConfigWidgets.so.5
#6 0x00007ffff202eb9d in ?? () from /usr/lib/qt/plugins/styles/breeze.so
#7 0x00007ffff203bb45 in ?? () from /usr/lib/qt/plugins/styles/breeze.so
#8 0x00007ffff2041fb4 in ?? () from /usr/lib/qt/plugins/styles/breeze.so
#9 0x00007ffff2051d24 in ?? () from /usr/lib/qt/plugins/styles/breeze.so
#10 0x00007ffff7aa5dee in QStyleFactory::create(QString const&) () from /usr/lib/libQt5Widgets.so.5
#11 0x00007ffff7a3555a in QApplication::style() () from /usr/lib/libQt5Widgets.so.5
#12 0x00007ffff7a35ade in QApplicationPrivate::initialize() () from /usr/lib/libQt5Widgets.so.5
#13 0x00007ffff7a35d98 in QApplicationPrivate::init() () from /usr/lib/libQt5Widgets.so.5
#14 0x000055555556207c in ?? ()
#15 0x00007ffff6889153 in __libc_start_main () from /usr/lib/libc.so.6
#16 0x000055555556248e in ?? ()

Steps to reproduce:
1. Enable kde-unstable and testing, and then upgrade everything to latest version.
2. Observe that qdbusviewer, qtcreator and other Qt programs crashes on startup.