19c4db4201
Amends b6b489db6968fbc3b4aab3755d0166ee09712ff0, which introduced UB
(invalid downcast):
By the time the
QMainWindowTabBars are destroyed, and they want to unregister
themselves from the QMainWindow, the ex-QMainWindow has already been
demoted to a QWidget. Says UBSan:
qmainwindow.cpp:63:47: runtime error: member call on address 0x6040000267d0 which does not point to an object of type 'QMainWindow'
0x6040000267d0: note: object is of type 'QWidget'
00 00 00 00 28 c1 e6 f3 c7 7f 00 00 80 24 00 00 60 61 00 00 d8 c2 e6 f3 c7 7f 00 00 00 00 be be
^~~~~~~~~~~~~~~~~~~~~~~
vptr for 'QWidget'
#0 0x7fc7f06da8c5 in QMainWindowPrivate::mainWindowLayout(QMainWindow const*) qmainwindow.cpp:63
#1 0x7fc7f06da8c5 in qt_mainwindow_layout(QMainWindow const*) qmainwindow.cpp:69
#2 0x7fc7f07bb4ed in QMainWindowTabBar::~QMainWindowTabBar() qmainwindowlayout.cpp:2042
#3 0x7fc7f07bf4e5 in QMainWindowTabBar::~QMainWindowTabBar() qmainwindowlayout.cpp:2047
#4 0x7fc7c69f9c2a in QObjectPrivate::deleteChildren() qobject.cpp:2226
#5 0x7fc7ef0b7f3d in QWidget::~QWidget() qwidget.cpp:1557
#6 0x7fc7f082c7c7 in QDockWidgetGroupWindow::~QDockWidgetGroupWindow() qmainwindowlayout_p.h:343
#7 0x7fc7f082c7c7 in QDockWidgetGroupWindow::~QDockWidgetGroupWindow() qmainwindowlayout_p.h:343
#8 0x7fc7c69f9c2a in QObjectPrivate::deleteChildren() qobject.cpp:2226
#9 0x7fc7ef0b7f3d in QWidget::~QWidget() qwidget.cpp:1557
#10 0x7fc7f06ce495 in QMainWindow::~QMainWindow() qmainwindow.cpp:338
#12 0x556a6180a84c in std::default_delete<QMainWindow>::operator()(QMainWindow*) const unique_ptr.h:85
#13 0x556a6180a84c in std::unique_ptr<QMainWindow, std::default_delete<QMainWindow> >::~unique_ptr() unique_ptr.h:361
#14 0x556a6180a84c in tst_QDockWidget::setFloatingReparenting() tst_qdockwidget.cpp:492
Use qobject_cast to verify that the mainWindow is not pointing to a
QMainWindow that is being destroyed (and has passed the ~QMainWindow
destructor). If the main window is destroyed, then removing the tab bar
from the list of unused tab bars is unnecessary.
Pick-to: 6.8 6.5
Change-Id: I25e12d79198137b75cd2576ff1440b6c94277eba
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
(cherry picked from commit 1bbbacbecb0bd03a58fea889215850dfffebeb3b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>