~/foo/hangtest$ gdb ./hangtest
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Reading symbols from ./hangtest...done.
(gdb) run
Starting program: /home/horst/foo/hangtest/hangtest
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Qt: gdb: -nograb added to command-line options.
         Use the -dograb option to enforce grabbing.
[New Thread 0x7fffec5ef700 (LWP 4905)]
[New Thread 0x7fffe3fff700 (LWP 4906)]
[Thread 0x7fffe3fff700 (LWP 4906) exited]
^C
Program received signal SIGINT, Interrupt.
pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
185     ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S: No such file or directory.
(gdb) thread apply all bt

Thread 2 (Thread 0x7fffec5ef700 (LWP 4905)):
#0  0x00007ffff6f7688d in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007ffff39d8bd2 in ?? () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#2  0x00007ffff39da74f in xcb_wait_for_event () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#3  0x00007ffff7edae8a in QXcbEventReader::run (this=0x43d420)
    at /home/horst/ksrc5/qt/stable/qtbase/src/plugins/platforms/xcb/qxcbconnection.cpp:1321
#4  0x00007ffff72f11b1 in QThreadPrivate::start (arg=0x43d420)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/thread/qthread_unix.cpp:340
#5  0x00007ffff66e86aa in start_thread (arg=0x7fffec5ef700) at pthread_create.c:333
#6  0x00007ffff6f81e9d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7ffff7fa2780 (LWP 4896)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007ffff72f17b9 in QWaitConditionPrivate::wait (time=18446744073709551615, this=0x48c7b0)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/thread/qwaitcondition_unix.cpp:136
#2  QWaitCondition::wait (this=<optimized out>, mutex=mutex@entry=0x48cba0, time=time@entry=18446744073709551615)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/thread/qwaitcondition_unix.cpp:208
#3  0x00007ffff72ea234 in QSemaphore::acquire (this=this@entry=0x7fffffffd8c0, n=n@entry=1)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/thread/qsemaphore.cpp:137
#4  0x00007ffff74c63da in QMetaObject::activate (sender=sender@entry=0x485100, signalOffset=<optimized out>,
    local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x7fffffffd970)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:3701
#5  0x00007ffff74c69bd in QMetaObject::activate (sender=sender@entry=0x485100, m=m@entry=0x7ffff76e26e0 <QObject::staticMetaObject>,
    local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x7fffffffd970)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:3595
#6  0x00007ffff74c6a54 in QObject::destroyed (this=this@entry=0x485100, _t1=_t1@entry=0x485100) at .moc/moc_qobject.cpp:216
#7  0x00007ffff74cc468 in QObject::~QObject (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:913
#8  0x00007ffff78d9b37 in QStyle::~QStyle (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/widgets/styles/qstyle.cpp:413
#9  0x00007ffff78e2791 in QCommonStyle::~QCommonStyle (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/widgets/styles/qcommonstyle.cpp:128
#10 0x00007fffeac2fae2 in KStyle::~KStyle (this=0x485100, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/frameworks/frameworkintegration/src/kstyle/kstyle.cpp:191
#11 0x00007fffe835d5c8 in Breeze::Style::~Style (this=0x485100, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/kde/workspace/breeze/kstyle/breezestyle.cpp:199
#12 0x00007fffe835d5d3 in Breeze::Style::~Style (this=0x485100, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/kde/workspace/breeze/kstyle/breezestyle.cpp:203
#13 0x00007fffe8371c68 in Breeze::StylePlugin::<lambda()>::operator() (__closure=<synthetic pointer>)
    at /home/horst/ksrc5/kde/workspace/breeze/kstyle/breezestyleplugin.cpp:43
#14 QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, Breeze::StylePlugin::create(const QString&)::<lambda()> >::call (arg=<optimized out>, f=...) at /opt/kde5/include/QtCore/qobjectdefs_impl.h:495
#15 QtPrivate::Functor<Breeze::StylePlugin::create(const QString&)::<lambda()>, 0>::call<QtPrivate::List<>, void> (
    arg=<optimized out>, f=...) at /opt/kde5/include/QtCore/qobjectdefs_impl.h:552
#16 QtPrivate::QFunctorSlotObject<Breeze::StylePlugin::create(const QString&)::<lambda()>, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *) (which=<optimized out>, this_=<optimized out>, r=<optimized out>,
    a=<optimized out>, ret=<optimized out>) at /opt/kde5/include/QtCore/qobject_impl.h:192
#17 0x00007ffff74c64d2 in QtPrivate::QSlotObjectBase::call (a=0x7fffffffdbf0, r=0x485100, this=<optimized out>)
    at ../../include/QtCore/../../../qtbase/src/corelib/kernel/qobject_impl.h:124
#18 QMetaObject::activate (sender=sender@entry=0x47c9c0, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=0,
    argv=argv@entry=0x7fffffffdbf0) at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:3718
#19 0x00007ffff74c69bd in QMetaObject::activate (sender=sender@entry=0x47c9c0, m=m@entry=0x7ffff76e26e0 <QObject::staticMetaObject>,
    local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x7fffffffdbf0)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:3595
#20 0x00007ffff74c6a54 in QObject::destroyed (this=this@entry=0x47c9c0, _t1=_t1@entry=0x47c9c0) at .moc/moc_qobject.cpp:216
#21 0x00007ffff74cc468 in QObject::~QObject (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:913
---Type <return> to continue, or q <return> to quit---
#22 0x00007ffff78df0b3 in QStylePlugin::~QStylePlugin (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/widgets/styles/qstyleplugin.cpp:97
#23 0x00007fffe8371dff in Breeze::StylePlugin::~StylePlugin (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/kde/workspace/breeze/kstyle/breezestyleplugin.cpp:52
#24 0x00007fffe8371e0d in Breeze::StylePlugin::~StylePlugin (this=0x47c9c0, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/kde/workspace/breeze/kstyle/breezestyleplugin.cpp:54
#25 0x00007ffff748d2eb in QLibraryPrivate::unload (this=this@entry=0x4844f0, flag=flag@entry=QLibraryPrivate::UnloadSys)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/plugin/qlibrary.cpp:551
#26 0x00007ffff74829f2 in QFactoryLoaderPrivate::~QFactoryLoaderPrivate (this=0x47c910, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/plugin/qfactoryloader.cpp:88
#27 0x00007ffff7483561 in QFactoryLoaderPrivate::~QFactoryLoaderPrivate (this=0x47c910, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/plugin/qfactoryloader.cpp:91
#28 0x00007ffff74ccaac in QScopedPointerDeleter<QObjectData>::cleanup (pointer=<optimized out>)
    at ../../include/QtCore/../../../qtbase/src/corelib/tools/qscopedpointer.h:54
#29 QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> >::~QScopedPointer (
    this=0x7ffff7dd7d58 <(anonymous namespace)::Q_QGS_loader::innerFunction()::holder+8>, __in_chrg=<optimized out>)
    at ../../include/QtCore/../../../qtbase/src/corelib/tools/qscopedpointer.h:101
#30 QObject::~QObject (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/kernel/qobject.cpp:893
#31 0x00007ffff7485510 in QFactoryLoader::~QFactoryLoader (
    this=0x7ffff7dd7d50 <(anonymous namespace)::Q_QGS_loader::innerFunction()::holder>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/corelib/plugin/qfactoryloader.cpp:226
#32 0x00007ffff78dbc83 in (anonymous namespace)::Q_QGS_loader::Holder::~Holder (this=<optimized out>, __in_chrg=<optimized out>)
    at /home/horst/ksrc5/qt/stable/qtbase/src/widgets/styles/qstylefactory.cpp:70
#33 0x00007ffff6eb4d32 in __run_exit_handlers (status=status@entry=0, listp=0x7ffff723f698 <__exit_funcs>,
    run_list_atexit=run_list_atexit@entry=true) at exit.c:82
#34 0x00007ffff6eb4d85 in __GI_exit (status=status@entry=0) at exit.c:104
#35 0x00000000004007ef in main (argc=1, argv=<optimized out>) at main.cpp:7
(gdb)