Fix to crash in QWindow::event when delete this called on closeEvent

Starting from Qt 5.11 QWindow::event is called after QDialog::closeEvent
which would cause a crash if "delete this" was called on closeEvent.  The commit
that changed this was e0b5ff4ad583befbecbcbe462998e3ed80899531. Added
a check before QWindow::event call utilizing QPointer to prevent the
function call in case object is destroyed by a user in close event handler.

Change-Id: I64a4a0f3271714e55bf7e806177f0d8b39b67fa3
Fixes: QTBUG-84222
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 036c3c19e7da5f1a280750d3c68a0cff38678029)
(cherry picked from commit 710777d5d32ef13f2037cfe58e40ff2343355759)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/widgets/kernel/qwidgetwindow.cpp b/src/widgets/kernel/qwidgetwindow.cpp
index c3f570ce4f..e74243203a 100644
--- a/src/widgets/kernel/qwidgetwindow.cpp
+++ b/src/widgets/kernel/qwidgetwindow.cpp
@@ -243,10 +243,14 @@ bool QWidgetWindow::event(QEvent *event)
     }
 
     switch (event->type()) {
-    case QEvent::Close:
+    case QEvent::Close: {
+        // The widget might be deleted in the close event handler.
+        QPointer<QObject> guard = this;
         handleCloseEvent(static_cast<QCloseEvent *>(event));
-        QWindow::event(event);
+        if (guard)
+            QWindow::event(event);
         return true;
+    }
 
     case QEvent::Enter:
     case QEvent::Leave: