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, 5 insertions, 1 deletions

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 4f5efa1..5d2b4c0 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -5667,7 +5667,11 @@ void QImage::setAlphaChannel(const QImage &alphaChannel)
 
     detach();
 
-    *this = convertToFormat(QImage::Format_ARGB32_Premultiplied);
+    QImage converted = convertToFormat(QImage::Format_ARGB32_Premultiplied);
+    if (!converted.isNull())
+        *this = converted;
+    else
+        return;
 
     // Slight optimization since alphachannels are returned as 8-bit grays.
     if (alphaChannel.d->depth == 8 && alphaChannel.isGrayscale()) {