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

5 files changed, 45 insertions, 11 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()) {
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
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;
+            }
         }
     }
 
diff --git a/tests/auto/exceptionsafety_objects/tst_exceptionsafety_objects.cpp b/tests/auto/exceptionsafety_objects/tst_exceptionsafety_objects.cpp
index 4433c7a..91d1a44 100644
--- a/tests/auto/exceptionsafety_objects/tst_exceptionsafety_objects.cpp
+++ b/tests/auto/exceptionsafety_objects/tst_exceptionsafety_objects.cpp
@@ -43,6 +43,7 @@
 #include <QtTest/QtTest>
 
 #include <stddef.h>
+#include <exception>
 
 QT_USE_NAMESPACE
 
@@ -285,8 +286,26 @@ void tst_ExceptionSafetyObjects::safeMessageHandler(QtMsgType type, const char *
     allocFailer.reactivateAt(currentIndex);
 }
 
+typedef void (*PVF)();
+PVF defaultTerminate;
+void debugTerminate()
+{
+    // you can detect uncaught exceptions with a breakpoint in here
+    (*defaultTerminate)();
+}
+
+PVF defaultUnexpected;
+void debugUnexpected()
+{
+    // you can detect unexpected exceptions with a breakpoint in here
+    (*defaultUnexpected)();
+}
+
 void tst_ExceptionSafetyObjects::initTestCase()
 {
+    // set handlers for bad exception cases, you might want to step in and breakpoint the default handlers too
+    defaultTerminate = std::set_terminate(&debugTerminate);
+    defaultUnexpected = std::set_unexpected(&debugUnexpected);
     testMessageHandler = qInstallMsgHandler(safeMessageHandler);
 
     QVERIFY(AllocFailer::initialize());