I had just logged in to try Plasma 5.5.3 was launching some Konsoles.

Here is the backtrace, but sorry, debug symbols for QML are not available for Kubuntu at the moment.

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 0x7f2b84e52840 (LWP 8856))]

Thread 4 (Thread 0x7f2b74c8d700 (LWP 8881)):
#0  0x00007f2b9b0da743 in select () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f2b996bcb7f in qt_safe_select(int, fd_set*, fd_set*, fd_set*, timespec const*) (nfds=17, fdread=fdread@entry=0x7f2b68000a78, fdwrite=fdwrite@entry=0x7f2b68000d08, fdexcept=fdexcept@entry=0x7f2b68000f98, orig_timeout=orig_timeout@entry=0x0) at kernel/qcore_unix.cpp:75
#2  0x00007f2b996be67e in QEventDispatcherUNIXPrivate::doSelect(QFlags<QEventLoop::ProcessEventsFlag>, timespec*) (timeout=0x0, exceptfds=0x7f2b68000f98, writefds=0x7f2b68000d08, readfds=0x7f2b68000a78, nfds=<optimized out>, this=0x7f2b680008c0) at kernel/qeventdispatcher_unix.cpp:320
#3  0x00007f2b996be67e in QEventDispatcherUNIXPrivate::doSelect(QFlags<QEventLoop::ProcessEventsFlag>, timespec*) (this=this@entry=0x7f2b680008e0, flags=..., flags@entry=..., timeout=timeout@entry=0x0) at kernel/qeventdispatcher_unix.cpp:196
#4  0x00007f2b996bebae in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f2b680008c0, flags=...) at kernel/qeventdispatcher_unix.cpp:607
#5  0x00007f2b9966850a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7f2b74c8cd60, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#6  0x00007f2b99484ac4 in QThread::exec() (this=<optimized out>) at thread/qthread.cpp:503
#7  0x00007f2b941bbc35 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#8  0x00007f2b99489a6e in QThreadPrivate::start(void*) (arg=0xcd3320) at thread/qthread_unix.cpp:331
#9  0x00007f2b9a6e26aa in start_thread (arg=0x7f2b74c8d700) at pthread_create.c:333
#10 0x00007f2b9b0e3eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 3 (Thread 0x7f2b6f7ff700 (LWP 8886)):
#0  0x00007f2b9a6e7da0 in pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007f2b98612194 in QTWTF::TCMalloc_PageHeap::scavengerThread() (this=0x7f2b986faee0 <QTWTF::pageheap_memory>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:2359
#2  0x00007f2b986121d9 in QTWTF::TCMalloc_PageHeap::runScavengerThread(void*) (context=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:1464
#3  0x00007f2b9a6e26aa in start_thread (arg=0x7f2b6f7ff700) at pthread_create.c:333
#4  0x00007f2b9b0e3eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7f2b6e9d6700 (LWP 9316)):
#0  0x00007f2b9b0da743 in select () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f2b996bcb7f in qt_safe_select(int, fd_set*, fd_set*, fd_set*, timespec const*) (nfds=19, fdread=fdread@entry=0x7f2ae40d9228, fdwrite=fdwrite@entry=0x7f2ae40d94b8, fdexcept=fdexcept@entry=0x7f2ae40d9748, orig_timeout=orig_timeout@entry=0x0) at kernel/qcore_unix.cpp:75
#2  0x00007f2b996be67e in QEventDispatcherUNIXPrivate::doSelect(QFlags<QEventLoop::ProcessEventsFlag>, timespec*) (timeout=0x0, exceptfds=0x7f2ae40d9748, writefds=0x7f2ae40d94b8, readfds=0x7f2ae40d9228, nfds=<optimized out>, this=0x7f2ae41466b0) at kernel/qeventdispatcher_unix.cpp:320
#3  0x00007f2b996be67e in QEventDispatcherUNIXPrivate::doSelect(QFlags<QEventLoop::ProcessEventsFlag>, timespec*) (this=this@entry=0x7f2ae40d9090, flags=..., flags@entry=..., timeout=timeout@entry=0x0) at kernel/qeventdispatcher_unix.cpp:196
#4  0x00007f2b996bebae in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f2ae41466b0, flags=...) at kernel/qeventdispatcher_unix.cpp:607
#5  0x00007f2b9966850a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7f2b6e9d5d60, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#6  0x00007f2b99484ac4 in QThread::exec() (this=<optimized out>) at thread/qthread.cpp:503
#7  0x00007f2b941bbc35 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#8  0x00007f2b99489a6e in QThreadPrivate::start(void*) (arg=0xbfbd70) at thread/qthread_unix.cpp:331
#9  0x00007f2b9a6e26aa in start_thread (arg=0x7f2b6e9d6700) at pthread_create.c:333
#10 0x00007f2b9b0e3eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7f2b84e52840 (LWP 8856)):
[KCrash Handler]
#6  0x00007f2b940d4d35 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#7  0x00007f2b9407bbd5 in QV4::ExecutionEngine::newStringObject(QV4::Value const&) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#8  0x00007f2b94115092 in QV4::Runtime::getProperty(QV4::ExecutionEngine*, QV4::Value const&, int) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#9  0x00007f2b741ec319 in  ()
#10 0x00007f2b948e97a2 in QQuickItem::staticMetaObject () at /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#11 0x00007f2b6d9d7238 in  ()
#12 0x0000000001773ad0 in  ()
#13 0x00007f2b6d9d7230 in  ()
#14 0x0000000000c57150 in  ()
#15 0x00007f2b999d0119 in (anonymous namespace)::construct(QVariant::Private*, void const*) (this=<synthetic pointer>, tc=<synthetic pointer>) at ../../include/QtCore/5.5.1/QtCore/private/../../../../../src/corelib/kernel/qvariant_p.h:339
#16 0x00007f2b999d0119 in (anonymous namespace)::construct(QVariant::Private*, void const*) (this=<optimized out>, tc=<synthetic pointer>) at ../../include/QtCore/5.5.1/QtCore/private/../../../../../src/corelib/kernel/qvariant_p.h:362
#17 0x00007f2b999d0119 in (anonymous namespace)::construct(QVariant::Private*, void const*) (this=<synthetic pointer>) at ../../include/QtCore/5.5.1/QtCore/private/../../../../../src/corelib/kernel/qvariant_p.h:383
#18 0x00007f2b999d0119 in (anonymous namespace)::construct(QVariant::Private*, void const*) (data=0x0, type=<optimized out>, logic=<synthetic pointer>) at ../../include/QtCore/5.5.1/QtCore/private/../../../../../src/corelib/kernel/qmetatypeswitcher_p.h:68
#19 0x00007f2b999d0119 in (anonymous namespace)::construct(QVariant::Private*, void const*) (x=0xd76240, copy=0x7ffc6b6cde40) at kernel/qguivariant.cpp:101
#20 0x0000000000c57150 in  ()
#21 0x0000000000c57150 in  ()
#22 0x0000000001777038 in  ()
#23 0x0000000000000003 in  ()
#24 0x0000000001776da0 in  ()
#25 0x00007f2b942fde20 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#26 0x00007f2b6d9d71d0 in  ()
#27 0x0000000000c57150 in  ()
#28 0x00007ffc6b6ce8d0 in  ()
#29 0x00007f2b74228ca0 in  ()
#30 0x0000000000000000 in  ()


Reproducible: Didn't try


Actual Results:  
crash

Expected Results:  
no crash

The "Enable Compositor on startup" setting is not checked.

Here are some version info:

Package: kwin-x11
Version: 4:5.5.3-0ubuntu1~ubuntu15.10~ppa1

Package: libkf5windowsystem5
Version: 5.18.0-0ubuntu1~ubuntu15.10~ppa1

Package: libqt5core5a
Version: 5.5.1+dfsg-1ubuntu1~wily1~test1