Hi,
I had a crash in QDBusConnection::sessionBus() earlier today, called from a
dtor in a style plugin. The traceback showed a NULL "this" pointer (frame #12):
frame #4: 0x00007fff8b9035aa libsystem_platform.dylib`_sigtramp + 26
frame #5: 0x000000010a30b15f QtCore`QMutex::lock() [inlined]
std::__1::__atomic_base<QMutexData*,
false>::compare_exchange_strong(__m=<unavailable>) + 1 at atomic:622
frame #6: 0x000000010a30b15e QtCore`QMutex::lock() [inlined] bool
QAtomicOps<QMutexData*>::testAndSetAcquire<QMutexData*>(std::__1::atomic<QMutexData*>&,
QMutexData*, QMutexData*, QMutexData**) at qatomic_cxx11.h:158
frame #7: 0x000000010a30b15e QtCore`QMutex::lock() [inlined]
QBasicAtomicPointer<QMutexData>::testAndSetAcquire(QMutexData*, QMutexData*,
QMutexData*&) at qbasicatomic.h:276
frame #8: 0x000000010a30b15e QtCore`QMutex::lock() [inlined]
QBasicMutex::fastTryLock(QMutexData*&) at qmutex.h:82
frame #9: 0x000000010a30b15e QtCore`QMutex::lock(this=0x0000000000000020) +
14 at qmutex.cpp:219
frame #10: 0x0000000108b60f31
QtDBus`QDBusConnectionManager::busConnection(QDBusConnection::BusType)
[inlined] QMutexLocker::QMutexLocker(m=0x0000000000000020) + 81 at qmutex.h:128
frame #11: 0x0000000108b60f29
QtDBus`QDBusConnectionManager::busConnection(QDBusConnection::BusType)
[inlined] QMutexLocker::QMutexLocker(m=0x0000000000000020) at qmutex.h:131
frame #12: 0x0000000108b60f29
QtDBus`QDBusConnectionManager::busConnection(this=0x0000000000000000,
type=SessionBus) + 73 at qdbusconnection.cpp:116
frame #13: 0x0000000108b63878 QtDBus`QDBusConnection::sessionBus() + 24 at
qdbusconnection.cpp:1180
the dtor cannot do a double disconnect or something of the sort as far as I can
see. It does however do
auto bus = QDBusConnection::sessionBus();
just like the ctor does when setting up DBus. Is that correct practice or
should one somehow cache the result of sessionBus() in order to call it only
once?
This is Qt 5.6, btw.
Thanks,
R.
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