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

2 files changed, 13 insertions, 4 deletions

diff --git a/src/gui/kernel/qapplication_s60.cpp b/src/gui/kernel/qapplication_s60.cpp
index 37d1b62..e986ce9 100644
--- a/src/gui/kernel/qapplication_s60.cpp
+++ b/src/gui/kernel/qapplication_s60.cpp
@@ -372,8 +372,13 @@ QSymbianControl::~QSymbianControl()
 {
     if (S60->curWin == this)
         S60->curWin = 0;
-    if (!QApplicationPrivate::is_app_closing)
-        setFocusSafely(false);
+    if (!QApplicationPrivate::is_app_closing) {
+        QT_TRY {
+            setFocusSafely(false);
+        } QT_CATCH(const std::exception&) {
+            // ignore exceptions, nothing can be done
+        }
+    }
     S60->appUi()->RemoveFromStack(this);
     delete m_longTapDetector;
 }
diff --git a/src/gui/kernel/qwidget.cpp b/src/gui/kernel/qwidget.cpp
index cd943cd..e180001 100644
--- a/src/gui/kernel/qwidget.cpp
+++ b/src/gui/kernel/qwidget.cpp
@@ -1487,8 +1487,12 @@ QWidget::~QWidget()
     if (QWidgetPrivate::allWidgets) // might have been deleted by ~QApplication
         QWidgetPrivate::allWidgets->remove(this);
 
-    QEvent e(QEvent::Destroy);
-    QCoreApplication::sendEvent(this, &e);
+    QT_TRY {
+        QEvent e(QEvent::Destroy);
+        QCoreApplication::sendEvent(this, &e);
+    } QT_CATCH(const std::exception&) {
+        // if this fails we can't do anything about it but at least we are not allowed to throw.
+    }
 }
 
 int QWidgetPrivate::instanceCounter = 0;  // Current number of widget instances