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  1. Qt
  2. QTBUG-38635

QML Crash in garbage collection when creating new Component

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    • Commits:
      a560018d08d4212bc65c163eb608639f19b38df2 (qtdeclarative)

      Description

      Observed a crash when creating new QML Components from C++. Verified that object ownership was correct.

      Did a stack trace and discovered that in qv4qobjectwrapper.cpp markChildQObjectsRecursively() we are attempting to dereference a NULL child pointer. I know that the QML parent of these children is being destroyed via a call to destroy() in QML and was dynamically created. So when I look at the QList of children one step up in the recursive stack all the children are null.

      Will include the stack trace. It is difficult to provide example code because this is buried in a proprietary C++ class. It is also not reproducible 100% of the time, only about 80% in my case. This indicates that an element of timing may be involved so here is the timeline in my code that leads to the crash:

      1. A "Page" is being destroyed.
      2. When one of the components on the page is set to null it triggers a binding in an external component which changes its model.
      3. The model change causes the external component to re-create its delegates (which happens in C++). During the beginCreate() call (and occasionally during the completeCreate() call) garbage collection is triggered and seems to be trying to garbage collect my entire application. When I followed the recursive marking up to the top, the first QObject without a parent that is being garbage collected is the QML component in my main.qml file.

      Could be related to https://bugreports.qt-project.org/browse/QTBUG-36183

      Stack Backtrace:

      0	QScopedPointer<QObjectData,QScopedPointerDeleter<QObjectData> >::data	qscopedpointer.h	143	0x59f7277a	
      1	qGetPtrHelper<QScopedPointer<QObjectData,QScopedPointerDeleter<QObjectData> > >	qglobal.h	938	0x59f69b4b	
      2	QObject::d_func	qobject.h	118	0x59f6fc23	
      3	QObjectPrivate::get	qobject_p.h	200	0x59f6c47b	
      4	QQmlData::get	qqmldata_p.h	196	0x656adb30	
      5	markChildQObjectsRecursively	qv4qobjectwrapper.cpp	958	0x658de1fd	
      6	markChildQObjectsRecursively	qv4qobjectwrapper.cpp	961	0x658de225	
      7	markChildQObjectsRecursively	qv4qobjectwrapper.cpp	961	0x658de225	
      8	markChildQObjectsRecursively	qv4qobjectwrapper.cpp	961	0x658de225	
      9	markChildQObjectsRecursively	qv4qobjectwrapper.cpp	961	0x658de225	
      10	QV4::QObjectWrapper::markObjects	qv4qobjectwrapper.cpp	979	0x658de18b	
      11	QV4::MemoryManager::mark	qv4mm.cpp	312	0x65868733	
      12	QV4::MemoryManager::runGC	qv4mm.cpp	440	0x65868bf4	
      13	QV4::MemoryManager::alloc	qv4mm.cpp	207	0x658682d3	
      14	QV4::MemoryManager::allocManaged	qv4mm_p.h	102	0x657b4614	
      15	QV4::Members::ensureIndex	qv4memberdata.cpp	78	0x65899fb0	
      16	QV4::Object::ensureMemberIndex	qv4object.cpp	232	0x6589c1df	
      17	QV4::Object::insertMember	qv4object.cpp	242	0x6589c22f	
      18	QV4::SimpleScriptFunction::SimpleScriptFunction	qv4functionobject.cpp	458	0x658885bc	
      19	QV4::FunctionObject::createScriptFunction	qv4functionobject.cpp	183	0x658870ee	
      20	QQmlObjectCreator::setPropertyBinding	qqmlobjectcreator.cpp	823	0x659c9c51	
      21	QQmlObjectCreator::setupBindings	qqmlobjectcreator.cpp	724	0x659c94b5	
      22	QQmlObjectCreator::populateInstance	qqmlobjectcreator.cpp	1316	0x659cc182	
      23	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1158	0x659cb7f9	
      24	QQmlObjectCreator::setPropertyBinding	qqmlobjectcreator.cpp	765	0x659c9887	
      25	QQmlObjectCreator::setupBindings	qqmlobjectcreator.cpp	724	0x659c94b5	
      26	QQmlObjectCreator::populateInstance	qqmlobjectcreator.cpp	1316	0x659cc182	
      27	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1158	0x659cb7f9	
      28	QQmlObjectCreator::create	qqmlobjectcreator.cpp	219	0x659c6cc3	
      29	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1075	0x659cb1c9	
      30	QQmlObjectCreator::create	qqmlobjectcreator.cpp	219	0x659c6cc3	
      31	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1075	0x659cb1c9	
      32	QQmlObjectCreator::setPropertyBinding	qqmlobjectcreator.cpp	765	0x659c9887	
      33	QQmlObjectCreator::setupBindings	qqmlobjectcreator.cpp	724	0x659c94b5	
      34	QQmlObjectCreator::populateInstance	qqmlobjectcreator.cpp	1316	0x659cc182	
      35	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1158	0x659cb7f9	
      36	QQmlObjectCreator::setPropertyBinding	qqmlobjectcreator.cpp	765	0x659c9887	
      37	QQmlObjectCreator::setupBindings	qqmlobjectcreator.cpp	724	0x659c94b5	
      38	QQmlObjectCreator::populateInstance	qqmlobjectcreator.cpp	1316	0x659cc182	
      39	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1158	0x659cb7f9	
      40	QQmlObjectCreator::setPropertyBinding	qqmlobjectcreator.cpp	765	0x659c9887	
      41	QQmlObjectCreator::setupBindings	qqmlobjectcreator.cpp	724	0x659c94b5	
      42	QQmlObjectCreator::populateInstance	qqmlobjectcreator.cpp	1316	0x659cc182	
      43	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1158	0x659cb7f9	
      44	QQmlObjectCreator::create	qqmlobjectcreator.cpp	219	0x659c6cc3	
      45	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1075	0x659cb1c9	
      46	QQmlObjectCreator::create	qqmlobjectcreator.cpp	219	0x659c6cc3	
      47	QQmlObjectCreator::createInstance	qqmlobjectcreator.cpp	1075	0x659cb1c9	
      48	QQmlObjectCreator::create	qqmlobjectcreator.cpp	219	0x659c6cc3	
      49	QQmlComponentPrivate::beginCreate	qqmlcomponent.cpp	884	0x6592d7ff	
      50	QQmlComponent::beginCreate	qqmlcomponent.cpp	834	0x6592d512	
      51	Hmi::Core::KeyboardAbstract::generateKeyboard	KeyboardAbstract.cpp	474	0x10062ff3	
      52	Hmi::Core::KeyboardAbstract::handleKeysChanged	KeyboardAbstract.cpp	302	0x100627df	
      53	Hmi::Core::KeyboardAbstract::qt_static_metacall	KeyboardAbstract.moc.1.cpp	150	0x100aaba0	
      54	QMetaObject::activate	qobject.cpp	3680	0x5a29b66c	
      55	QMetaObject::activate	qobject.cpp	3546	0x5a29b081	
      56	Hmi::Core::KeyboardModel::keysChanged	KeyboardModel.moc.1.cpp	285	0x100ac7ea	
      57	Hmi::Core::KeyboardModel::setLevel	KeyboardModel.cpp	277	0x1006bcbb	
      58	Hmi::Core::KeyboardModel::qt_metacall	KeyboardModel.moc.1.cpp	260	0x100ac70c	
      59	QMetaObject::metacall	qmetaobject.cpp	309	0x5a2542a0	
      60	QQmlPropertyPrivate::write	qqmlproperty.cpp	1449	0x659282a2	
      61	QQmlPropertyPrivate::writeValueProperty	qqmlproperty.cpp	1246	0x659274ce	
      62	QQmlPropertyPrivate::writeValueProperty	qqmlproperty.cpp	1212	0x65927390	
      63	QQmlPropertyPrivate::write	qqmlproperty.cpp	1709	0x65929582	
      64	QQmlProperty::write	qqmlproperty.cpp	1631	0x659293e9	
      65	QQmlBind::eval	qqmlbind.cpp	307	0x65a19fa4	
      66	QQmlBind::setObject	qqmlbind.cpp	209	0x65a19c36	
      67	QQmlBind::qt_metacall	moc_qqmlbind_p.cpp	118	0x65a5a2a5	
      68	QMetaObject::metacall	qmetaobject.cpp	309	0x5a2542a0	
      69	QQmlPropertyPrivate::write	qqmlproperty.cpp	1317	0x659278f3	
      70	QQmlPropertyPrivate::writeValueProperty	qqmlproperty.cpp	1246	0x659274ce	
      71	QQmlPropertyPrivate::writeBinding	qqmlproperty.cpp	1572	0x6592904a	
      72	QQmlBinding::update	qqmlbinding.cpp	266	0x659bb660	
      73	QQmlBinding::update	qqmlbinding_p.h	105	0x6578906b	
      74	QQmlBinding::expressionChanged	qqmlbinding.cpp	328	0x659bba3c	
      75	QQmlJavaScriptExpressionGuard_callback	qqmljavascriptexpression.cpp	371	0x659b0c3e	
      76	QQmlNotifier::emitNotify	qqmlnotifier.cpp	81	0x6598b0bc	
      77	QQmlData::signalEmitted	qqmlengine.cpp	721	0x6590a5cc	
      78	QMetaObject::activate	qobject.cpp	3567	0x5a29b13f	
      79	QMetaObject::activate	qobject.cpp	3546	0x5a29b081	
      80	Hmi::Core::KeyboardAbstract::modelChanged	KeyboardAbstract.moc.1.cpp	333	0x100ab2ca	
      81	Hmi::Core::KeyboardAbstract::setModel	KeyboardAbstract.cpp	224	0x10062659	
      82	Hmi::Core::KeyboardAbstract::setGroupName	KeyboardAbstract.cpp	261	0x1006271a	
      83	Hmi::Core::KeyboardAbstract::qt_metacall	KeyboardAbstract.moc.1.cpp	284	0x100ab116	
      84	QQmlVMEMetaObject::metaCall	qqmlvmemetaobject.cpp	981	0x65903fec	
      85	QAbstractDynamicMetaObject::metaCall	qobject_p.h	428	0x59f6cd90	
      86	QMetaObject::metacall	qmetaobject.cpp	306	0x5a254283	
      87	QQmlPropertyPrivate::writeBinding	qqmlproperty.cpp	1500	0x6592893e	
      88	QQmlBinding::update	qqmlbinding.cpp	266	0x659bb660	
      89	QQmlBinding::update	qqmlbinding_p.h	105	0x6578906b	
      90	QQmlBinding::expressionChanged	qqmlbinding.cpp	328	0x659bba3c	
      91	QQmlJavaScriptExpressionGuard_callback	qqmljavascriptexpression.cpp	371	0x659b0c3e	
      92	QQmlNotifier::emitNotify	qqmlnotifier.cpp	81	0x6598b0bc	
      93	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      94	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      95	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      96	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      97	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      98	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      99	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      100	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      101	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      102	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      103	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      104	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      105	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      106	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      107	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      108	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      109	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      110	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      111	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      112	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      113	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      114	QQmlNotifier::emitNotify	qqmlnotifier.cpp	76	0x6598b054	
      115	QQmlData::signalEmitted	qqmlengine.cpp	721	0x6590a5cc	
      116	QMetaObject::activate	qobject.cpp	3567	0x5a29b13f	
      117	QQmlVMEMetaObject::activate	qqmlvmemetaobject.cpp	1333	0x6590540c	
      118	QQmlVMEVariantQObjectPtr::objectDestroyed	qqmlvmemetaobject.cpp	88	0x659075ef	
      119	QQmlData::destroyed	qqmlengine.cpp	1659	0x6590c079	
      120	QQmlData::destroyed	qqmlengine.cpp	633	0x6590a292	
      121	QObject::~QObject	qobject.cpp	916	0x5a295631	
      122	QQuickItem::~QQuickItem	qquickitem.cpp	2118	0xf437805	
      123	QQuickFocusScope::~QQuickFocusScope	qquickfocusscope.cpp	69	0xf468be2	
      124	QQmlPrivate::QQmlElement<QQuickFocusScope>::~QQmlElement<QQuickFocusScope>	qqmlprivate.h	106	0xf4a6cef	
      125	QQmlPrivate::QQmlElement<QQuickFocusScope>::`scalar deleting destructor'	Qt5Quickd		0xf4967cf	
      126	QObjectPrivate::deleteChildren	qobject.cpp	1935	0x5a296f29	
      127	QObject::~QObject	qobject.cpp	1030	0x5a295a05	
      128	QQuickItem::~QQuickItem	qquickitem.cpp	2118	0xf437805	
      129	QQmlPrivate::QQmlElement<QQuickItem>::~QQmlElement<QQuickItem>	qqmlprivate.h	106	0xf4a6f5f	
      130	QQmlPrivate::QQmlElement<QQuickItem>::`scalar deleting destructor'	Qt5Quickd		0xf49694f	
      131	qDeleteInEventHandler	qobject.cpp	4342	0x5a29cf07	
      132	QObject::event	qobject.cpp	1232	0x5a295d20	
      133	QQuickItem::event	qquickitem.cpp	7112	0xf441e0b	
      134	QCoreApplicationPrivate::notify_helper	qcoreapplication.cpp	1053	0x5a248cde	
      135	QCoreApplication::notify	qcoreapplication.cpp	997	0x5a248a93	
      136	QGuiApplication::notify	qguiapplication.cpp	1458	0x996d6a	
      137	QCoreApplication::notifyInternal	qcoreapplication.cpp	935	0x5a2489e4	
      138	QCoreApplication::sendEvent	qcoreapplication.h	237	0x5a24d379	
      139	QCoreApplicationPrivate::sendPostedEvents	qcoreapplication.cpp	1539	0x5a249886	
      140	QCoreApplication::sendPostedEvents	qcoreapplication.cpp	1397	0x5a249542	
      141	QWindowsGuiEventDispatcher::sendPostedEvents	qwindowsguieventdispatcher.cpp	88	0x5746ce91	
      142	qt_internal_proc	qeventdispatcher_win.cpp	423	0x5a2e1404	
      143	InternalCallWinProc	USER32		0x772162fa	
      144	UserCallWinProcCheckWow	USER32		0x77216d3a	
      145	DispatchMessageWorker	USER32		0x772177c4	
      146	DispatchMessageW	USER32		0x7721788a	
      147	QEventDispatcherWin32::processEvents	qeventdispatcher_win.cpp	757	0x5a2e255b	
      148	QWindowsGuiEventDispatcher::processEvents	qwindowsguieventdispatcher.cpp	80	0x5746cdbc	
      149	QEventLoop::processEvents	qeventloop.cpp	137	0x5a2455fc	
      150	QEventLoop::exec	qeventloop.cpp	212	0x5a245762	
      151	QCoreApplication::exec	qcoreapplication.cpp	1188	0x5a248f42	
      152	QGuiApplication::exec	qguiapplication.cpp	1437	0x996cb8	
      153	main	main.cpp	135	0x4bc2e0	
      154	WinMain	hmi_main		0x596702	
      155	__tmainCRTStartup	crtexe.c	574	0x5952a8	
      156	WinMainCRTStartup	crtexe.c	399	0x59500f	
      157	BaseThreadInitThunk	kernel32		0x7594336a	
      158	__RtlUserThreadStart	ntdll32		0x77c89f72	
      159	_RtlUserThreadStart	ntdll32		0x77c89f45	
      

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              Assignee:
              shausman Simon Hausmann
              Reporter:
              leonard777 Corey Pendleton
              Votes:
              6 Vote for this issue
              Watchers:
              10 Start watching this issue

                Dates

                Created:
                Updated:
                Resolved:

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