2.5 and main crash on shutdown

[ronso0]

Bug Description

I'm getting this crash on 2.5 and main 359c40e

• --developer
• with Qt 6.2.3 and
• the legacy skin (backtrace below)

Did git bisect for some hours and it seems that it's caused by 4ba370b (or rather that/2.5/2.4 being merged to main?).

mixxx/src/mixxxapplication.cpp

Lines 202 to 212 in 028e3ff

	if (m_isDeveloper && time.elapsed() > kEventNotifyExecTimeWarningThreshold) {
	qDebug() << "Processing event type"
	<< event->type()
	<< "for object"
	<< target->metaObject()->className()
	<< target->objectName()
	<< "running in thread:"
	<< target->thread()->objectName()
	<< "took"
	<< time.elapsed().debugMillisWithUnit();
	}

If I disable the logging everything shuts down cleanly.

The crash happens when trying to with target->metaObject() for
MixxxMainWindow(0x561df6faa0d0, ...) QChildEvent(ChildRemoved, QWidget(0x5605e0e18530) name="Mixxx")
= when the skin widget has been deleted.

With some debug logging added in this method (which expectedly slows everything down significantly) I get the crash even for
MixxxApplication::notify: LaunchImage(0x5605e1028700) QChildEvent(ChildRemoved, QObject(0x5605e0e18530))
Later on, with simple logging only in the 'long time' branch, I get it for
QWidgetWindow(0x561df6faa0d0, name = "MixxxMainWindowClassWindow") QCloseEvent(Close, 0x7ffd1966c8a0)

Conclusion?

The target has been deleted after QApplication::notify(target, event);
Hence even the additional condition for logging
target->metaObject() != nullptr
won't work.
Could it be that the logging itself causes the delay which in turn causes the crash??

Backtrace of thread #1

debug [Main] ~DlgAutoDJ() Thread 1 "mixxx" received signal SIGSEGV, Segmentation fault. 0x0000046200000000 in ?? ()

Thread 1 (Thread 0x7fffeade0100 (LWP 1002332) "mixxx"):
#0 0x0000046200000000 in ()
#1 0x00005555560c4e9b in MixxxApplication::notify(QObject*, QEvent*) (this=, target=0x5555797d84d0, event=) at /src/mixxxapplication.cpp:206
time = {m_startTime = std::chrono::_V2::steady_clock time_point = { 304985613821353ns }, static kStoppedTimerValue = {__d = std::chrono::duration = { -9223372036854775808ns }}}
ret = true
PRETTY_FUNCTION = "virtual bool MixxxApplication::notify(QObject*, QEvent*)"
#2 0x00007ffff594c830 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#3 0x00007ffff595002c in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#4 0x00005555560d9d5f in MixxxMainWindow::~MixxxMainWindow() (this=0x7fffffffdad0, __in_chrg=) at /src/mixxxmainwindow.cpp:476
t = {m_key = {d = {d = 0x555578e5c040, ptr = 0x555578e5c050 u"~MixxxMainWindow", size = 16}, static _empty = 0 u'\000'}, m_compute = {i = 111}, m_time = {m_startTime = std::chrono::_V2::steady_clock time_point = { 304985606973501ns }, static kStoppedTimerValue = {__d = std::chrono::duration = { -9223372036854775808ns }}}}
fullscreenPref =
#5 0x000055555595d57d in (anonymous namespace)::runMixxx (args=, pApp=0x7fffffffdaa0) at /src/main.cpp:110
mainWindow = { = {}, static staticMetaObject = {d = {superdata = {direct = 0x7ffff6f60200 QMainWindow::staticMetaObject}, stringdata = 0x55555589eee0 <qt_meta_stringdata_MixxxMainWindow>, data = 0x55555589ec00 <qt_meta_data_MixxxMainWindow>, static_metacall = 0x5555560df270 <MixxxMainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x5555567d6c60 <qt_incomplete_metaTypeArray<qt_meta_stringdata_MixxxMainWindow_t, QtPrivate::TypeAndForceComplete<MixxxMainWindow, std::integral_constant<bool, true> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<int, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<int, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<bool, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<int, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<bool, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<bool, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<bool, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<std::shared_ptr, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<int, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<QString const&, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<void, std::integral_constant<bool, false> >, QtPrivate::TypeAndForceComplete<mixxx::preferences::constants::Tooltips, std::integral_constant<bool, false> > >>, extradata = 0x0}}, m_pCoreServices = std::shared_ptr (use count 2, weak count 0) = {get() = 0x555556a32410}, m_pCentralWidget = 0x0, m_pLaunchImage = 0x0, m_prevState = {i = 2}, m_pSkinLoader = std::shared_ptr (use count 2, weak count 0) = {get() = 0x555556fe44c0}, m_pGuiTick = 0x7fffb400f8a0, m_pVisualsManager = 0x5555569d1830, m_pMenuBar = {m_ptr = 0x555556dee1d0}, m_supportsGlobalMenuBar = true, m_pDeveloperToolsDlg = 0x0, m_pPrefDlg = 0x555574f3f800, m_pKeywheel = {m_ptr = 0x0}, m_toolTipsCfg = mixxx::preferences::constants::Tooltips::On, m_inhibitScreensaver = (mixxx::preferences::constants::ScreenSaver::On | unknown: 0x5554), m_skinCreatedControls = {q_hash = {d = 0x5555797e6200}}}
exitCode = 0
console = {}
args =
app = { = {}, static staticMetaObject = {d = {superdata = {direct = 0x7ffff6f54960 QApplication::staticMetaObject}, stringdata = 0x55555589eb80 <qt_meta_stringdata_MixxxApplication>, data = 0x55555589eb40 <qt_meta_data_MixxxApplication>, static_metacall = 0x5555560c3510 <MixxxApplication::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x5555567d6858 <qt_incomplete_metaTypeArray<qt_meta_stringdata_MixxxApplication_t, QtPrivate::TypeAndForceComplete<MixxxApplication, std::integral_constant<bool, true> > >>, extradata = 0x0}}, m_rightPressedButtons = 0, m_pTouchShift = 0x0, m_isDeveloper = true}
exitCode =
PRETTY_FUNCTION = "int main(int, char**)"
#6 main(int, char**) (argc=, argv=) at /src/main.cpp:243
console = {}
args =
app = { = {}, static staticMetaObject = {d = {superdata = {direct = 0x7ffff6f54960 QApplication::staticMetaObject}, stringdata = 0x55555589eb80 <qt_meta_stringdata_MixxxApplication>, data = 0x55555589eb40 <qt_meta_data_MixxxApplication>, static_metacall = 0x5555560c3510 <MixxxApplication::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x5555567d6858 <qt_incomplete_metaTypeArray<qt_meta_stringdata_MixxxApplication_t, QtPrivate::TypeAndForceComplete<MixxxApplication, std::integral_constant<bool, true> > >>, extradata = 0x0}}, m_rightPressedButtons = 0, m_pTouchShift = 0x0, m_isDeveloper = true}
exitCode =
PRETTY_FUNCTION = "int main(int, char**)"

Version

2.5 and main

OS

Linux, Ubuntu 20.04.5

[Swiftb0y]

Do you have time and energy to look into this @JoergAtGithub?

[daschuer]

I can confirm the crash with main.