Reset QWindowPrivate::platformWindow during destruction before deleting it

Otherwise the deletion of the platform window may result in platform events
that then conclude the QWindow has a valid platform window and calls into
it, when it's been half-way destroyed.

Change-Id: If9eaad1b4e6aa414ba0f96475756a2146e0c01d5
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 5b5c1bd0e3..6dbba8b433 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -1882,11 +1882,16 @@ void QWindowPrivate::destroy()
     QPlatformSurfaceEvent e(QPlatformSurfaceEvent::SurfaceAboutToBeDestroyed);
     QGuiApplication::sendEvent(q, &e);
 
-    delete platformWindow;
+    // Unset platformWindow before deleting, so that the destructor of the
+    // platform window does not recurse back into the platform window via
+    // this window during destruction (e.g. as a result of platform events).
+    QPlatformWindow *pw = platformWindow;
+    platformWindow = nullptr;
+    delete pw;
+
     resizeEventPending = true;
     receivedExpose = false;
     exposed = false;
-    platformWindow = 0;
 
     if (wasVisible)
         maybeQuitOnLastWindowClosed();