QTBUG-4887 and other exception safety fixes

This change includes a fix for QTBUG-4887 and other exception safety
problems found while testing it.

The QTBUG-4887 fix is to qimage.cpp. QImage doesn't throw exceptions on
failure like a proper class should, instead it tries to fail "nice".
What happens here is that setAlphaChannel would crash on OOM as after
the convertToFormat call, d could be NULL. This new version checks the
result of the conversion before using it.

The other fixes are all cases where exceptions were thrown from
destructors. I added code to the test app to help debug these cases,
and I fixed all the problems I found.

With these changes, tst_exceptionsafety_objects runs and passes on the
Symbian emulator.

Reviewed-by: Shane Kearns

1 files changed, 8 insertions, 6 deletions

diff --git a/src/gui/widgets/qmenu.cpp b/src/gui/widgets/qmenu.cpp
index a9978f9..c7573bf 100644
--- a/src/gui/widgets/qmenu.cpp
+++ b/src/gui/widgets/qmenu.cpp
@@ -1406,12 +1406,14 @@ QMenu::QMenu(QMenuPrivate &dd, QWidget *parent)
 QMenu::~QMenu()
 {
     Q_D(QMenu);
-    QHash<QAction *, QWidget *>::iterator it = d->widgetItems.begin();
-    for (; it != d->widgetItems.end(); ++it) {
-        if (QWidget *widget = it.value()) {
-            QWidgetAction *action = static_cast<QWidgetAction *>(it.key());
-            action->releaseWidget(widget);
-            *it = 0;
+    if (!d->widgetItems.isEmpty()) {  // avoid detach on shared null hash
+        QHash<QAction *, QWidget *>::iterator it = d->widgetItems.begin();
+        for (; it != d->widgetItems.end(); ++it) {
+            if (QWidget *widget = it.value()) {
+                QWidgetAction *action = static_cast<QWidgetAction *>(it.key());
+                action->releaseWidget(widget);
+                *it = 0;
+            }
         }
     }