App crashes when moving a DockWidget outside MainWindow

[franku]

Hi There, I have got an application that always crashes when having moved a dockwidget outside the mainwindow. When I leave the dockwidget at its iriginal Place on the left docking area the application will close fine.


App ist build up with this code (Control will instantiate and destroy mainwindow):


int main(int argc, char *argv[])
{
QApplication app(argc, argv);

// app will destroy Control
// because it becomes Control's
// parent object via constructur
Control::getSingleton(&app);
int ret = app.exec();

return ret;
} // app Object will be destroyed (and its children)


IMHO the ~Control() Destructor will be called by the Application at last, so when finishing the application there will be (the destr. ist definitively called):




/* singleton-private Constructor */
Control::Control(QObject *parent) :
QObject(parent),
{
...
if(!mainWindow)
mainWindow = new MainWindow();
...
}

Control::~Control()
{
...
if(mainWindow) {
delete mainWindow; // will delete the ui including dockwidgets
mainWindow = NULL;
}
}


The Problem now is that when I have App destroying the mainwindow there comes a segmentation fault along - ending always in qwidget.cpp...



....
else if (!internalWinId() && isVisible()) {
qApp->d_func()->sendSyntheticEnterLeave(this);
....


...where the d_func() with its scoped pointer will fail.

But: This only happens, when I have moved the DockWidet "Floating" away from its orignial Place in the main window. If I leave it there, everthing is ok.

As someone may see the stacktrace shows that the Dockwidget will make use of the qapplication d_func(). Am I wrong, or why do at least two parents try to delete the Widget (Mainwindow and App) ?


0 QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> >::data qscopedpointer.h 135 0x00ff01e6
1 qGetPtrHelper<QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> > > qglobal.h 2314 0x008a63ff
2 QApplication::d_func qapplication.h 376 0x00eef9c4
3 ~QWidget qwidget.cpp 1438 0x008ec5f8
4 ~QDockWidget qdockwidget.cpp 1181 0x00c51fce
5 QObjectPrivate::deleteChildren qobject.cpp 1978 0x6a20f1b0
6 ~QWidget qwidget.cpp 1476 0x008ec6dc
7 ~QMainWindow qmainwindow.cpp 329 0x00c82888
8 ~MainWindow mainwindow.cpp 50 0x004018c0
9 ~Control control.cpp 83 0x00408feb
10 QObjectPrivate::deleteChildren qobject.cpp 1978 0x6a20f1b0
11 ~QObject qobject.cpp 975 0x6a20d0f9
12 ~QCoreApplication qcoreapplication.cpp 642 0x6a1fd127
13 ~QApplication qapplication.cpp 1118 0x008aa05e
14 qMain main.cpp 14 0x00401400
15 WinMain@16 qtmain_win.cpp 131 0x0040e612
16 main 0 0x0040e338


Any Comments ?

[The Storm]

QApplication will delete the main window without caring if it is his child or not and I guess that when you delete it yourself when the application object is destructing there is no way for the MainWindow to tell to QApplication that it is deleted and eventually QApplication will try to delete it while looping trough all the objects. So you have 2 choices:

1. Make sure you delete the MainWindow before the destruction of QApplication
2. Let QApplication care for that( this can be tricky depending on your program logic ).