Fix crash when deleting component in Component.onComplete through loader

This is a regression introduced with Qt 5.3.0. The recursion watcher code that
is supposed to handle the test case of QTBUG-39775 can detect the recursion
into the object creator. However the boolean that indicates the recursion is a
member of a structure that's deleted afterwards. To avoid access to deleted
memory, this patch simply reference counts data structure shared between the
creators and also wraps the recursion watcher into a convenience class that
also increases/decreases the reference count accordingly.

Change-Id: I8d2e3e200ab1295e89d951e09f187d382a056d5a
Task-number: QTBUG-39775
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

2 files changed, 28 insertions, 7 deletions

diff --git a/src/qml/qml/qqmlobjectcreator.cpp b/src/qml/qml/qqmlobjectcreator.cpp
index 16c9dd7aa0..36c7dfb0e9 100644
--- a/src/qml/qml/qqmlobjectcreator.cpp
+++ b/src/qml/qml/qqmlobjectcreator.cpp
@@ -91,7 +91,7 @@ QQmlObjectCreator::QQmlObjectCreator(QQmlContextData *parentContext, QQmlCompile
     init(parentContext);
 
     sharedState = new QQmlObjectCreatorSharedState;
-    sharedState.setFlag(); // We own it, so we must delete it
+    topLevelCreator = true;
     sharedState->componentAttached = 0;
     sharedState->allCreatedBindings.allocate(compiledData->totalBindingsCount);
     sharedState->allParserStatusCallbacks.allocate(compiledData->totalParserStatusCount);
@@ -115,6 +115,7 @@ QQmlObjectCreator::QQmlObjectCreator(QQmlContextData *parentContext, QQmlCompile
     init(parentContext);
 
     sharedState = inheritedSharedState;
+    topLevelCreator = false;
 }
 
 void QQmlObjectCreator::init(QQmlContextData *providedParentContext)
@@ -139,9 +140,9 @@ void QQmlObjectCreator::init(QQmlContextData *providedParentContext)
 
 QQmlObjectCreator::~QQmlObjectCreator()
 {
-    if (sharedState.flag()) {
+    if (topLevelCreator) {
         {
-            QRecursionWatcher<QQmlObjectCreatorSharedState, &QQmlObjectCreatorSharedState::recursionNode> watcher(sharedState.data());
+            QQmlObjectCreatorRecursionWatcher watcher(this);
         }
         for (int i = 0; i < sharedState->allCreatedBindings.count(); ++i) {
             QQmlAbstractBinding *b = sharedState->allCreatedBindings.at(i);
@@ -157,7 +158,6 @@ QQmlObjectCreator::~QQmlObjectCreator()
             QQmlComponentAttached *a = sharedState->componentAttached;
             a->rem();
         }
-        delete sharedState.data();
     }
 }
 
@@ -1172,7 +1172,7 @@ QQmlContextData *QQmlObjectCreator::finalize(QQmlInstantiationInterrupt &interru
     Q_ASSERT(phase == ObjectsCreated || phase == Finalizing);
     phase = Finalizing;
 
-    QRecursionWatcher<QQmlObjectCreatorSharedState, &QQmlObjectCreatorSharedState::recursionNode> watcher(sharedState.data());
+    QQmlObjectCreatorRecursionWatcher watcher(this);
     ActiveOCRestorer ocRestorer(this, QQmlEnginePrivate::get(engine));
 
     {
@@ -1334,3 +1334,10 @@ bool QQmlObjectCreator::populateInstance(int index, QObject *instance, QObject *
 }
 
 
+
+
+QQmlObjectCreatorRecursionWatcher::QQmlObjectCreatorRecursionWatcher(QQmlObjectCreator *creator)
+    : sharedState(creator->sharedState)
+    , watcher(creator->sharedState.data())
+{
+}
diff --git a/src/qml/qml/qqmlobjectcreator_p.h b/src/qml/qml/qqmlobjectcreator_p.h
index 379a3b2970..ad2d67624f 100644
--- a/src/qml/qml/qqmlobjectcreator_p.h
+++ b/src/qml/qml/qqmlobjectcreator_p.h
@@ -57,7 +57,7 @@ struct QQmlTypeCompiler;
 class QQmlInstantiationInterrupt;
 struct QQmlVmeProfiler;
 
-struct QQmlObjectCreatorSharedState
+struct QQmlObjectCreatorSharedState : public QSharedData
 {
     QQmlContextData *rootContext;
     QQmlContextData *creationContext;
@@ -128,7 +128,8 @@ private:
     const QVector<QQmlPropertyCache *> &propertyCaches;
     const QVector<QByteArray> &vmeMetaObjectData;
     QHash<int, int> objectIndexToId;
-    QFlagPointer<QQmlObjectCreatorSharedState> sharedState;
+    QExplicitlySharedDataPointer<QQmlObjectCreatorSharedState> sharedState;
+    bool topLevelCreator;
     void *activeVMEDataForRootContext;
 
     QObject *_qobject;
@@ -142,6 +143,19 @@ private:
     QQmlVMEMetaObject *_vmeMetaObject;
     QQmlListProperty<void> _currentList;
     QV4::ExecutionContext *_qmlContext;
+
+    friend struct QQmlObjectCreatorRecursionWatcher;
+};
+
+struct QQmlObjectCreatorRecursionWatcher
+{
+    QQmlObjectCreatorRecursionWatcher(QQmlObjectCreator *creator);
+
+    bool hasRecursed() const { return watcher.hasRecursed(); }
+
+private:
+    QExplicitlySharedDataPointer<QQmlObjectCreatorSharedState> sharedState;
+    QRecursionWatcher<QQmlObjectCreatorSharedState, &QQmlObjectCreatorSharedState::recursionNode> watcher;
 };
 
 QT_END_NAMESPACE