Fix crash in QRuntimeGraphicsSystem due to destruction order.

Firstly, fix a "leak" by deleting the graphics system when QApplication
is destroyed.

Secondly, fix a crash when the following scenario occurs:
- ~QApplication() deletes the current graphics system (see above)
- ~QApplication() calls qt_cleanup()
- qt_cleanup() calls QPixmapCache::clear() to delete pixmaps
- ~QRuntimePixmapData() tries to remove the pixmap from the runtime
  graphics system, but it has already been deleted.
- *Crash*

Reviewed-by: Gunnar Sletta
Reviewed-by: Jani Hautakangas

2 files changed, 6 insertions, 2 deletions

diff --git a/src/gui/kernel/qapplication.cpp b/src/gui/kernel/qapplication.cpp
index 82dd83a..ebad56e 100644
--- a/src/gui/kernel/qapplication.cpp
+++ b/src/gui/kernel/qapplication.cpp
@@ -1116,6 +1116,8 @@ QApplication::~QApplication()
     QApplicationPrivate::app_style = 0;
     delete QApplicationPrivate::app_icon;
     QApplicationPrivate::app_icon = 0;
+    delete QApplicationPrivate::graphics_system;
+    QApplicationPrivate::graphics_system = 0;
 #ifndef QT_NO_CURSOR
     d->cursor_list.clear();
 #endif
diff --git a/src/gui/painting/qgraphicssystem_runtime.cpp b/src/gui/painting/qgraphicssystem_runtime.cpp
index 2828e9d..a9fbbee 100644
--- a/src/gui/painting/qgraphicssystem_runtime.cpp
+++ b/src/gui/painting/qgraphicssystem_runtime.cpp
@@ -94,7 +94,8 @@ QRuntimePixmapData::QRuntimePixmapData(const QRuntimeGraphicsSystem *gs, PixelTy
 
 QRuntimePixmapData::~QRuntimePixmapData()
 {
-    m_graphicsSystem->removePixmapData(this);
+    if (QApplicationPrivate::graphics_system)
+        m_graphicsSystem->removePixmapData(this);
     delete m_data;
 }
 
@@ -258,7 +259,8 @@ QRuntimeWindowSurface::QRuntimeWindowSurface(const QRuntimeGraphicsSystem *gs, Q
 
 QRuntimeWindowSurface::~QRuntimeWindowSurface()
 {
-    m_graphicsSystem->removeWindowSurface(this);
+    if (QApplicationPrivate::graphics_system)
+        m_graphicsSystem->removeWindowSurface(this);
 }
 
 QPaintDevice *QRuntimeWindowSurface::paintDevice()