Prevent object being delete by GC before object is fully created

Add a new flag inCreation to QQmlData. Set it to true when a top-level object begins creation,
and back to false when initial creation is finished and the object has been marked indestructible.
In the GC callback function, if inCreation is true, skip the GC and make a weak reference for next GC loop.

Change-Id: I4ec82864c52f6be0c3e6ef892474dd77d835e152
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>
Reviewed-by: Chris Adams <christopher.adams@nokia.com>

5 files changed, 21 insertions, 3 deletions

diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index 2e46192246..e5c498a662 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -836,6 +836,7 @@ QQmlComponentPrivate::beginCreate(QQmlContextData *context)
         //if JS ownership is needed this needs to be explicitly undone (like in component.createObject())
         ddata->indestructible = true;
         ddata->explicitIndestructibleSet = true;
+        ddata->inCreation = false;
     }
 
     if (enginePriv->isDebugging && rv) {
diff --git a/src/qml/qml/qqmldata_p.h b/src/qml/qml/qqmldata_p.h
index 1a188f9e59..ffaa7e2cb5 100644
--- a/src/qml/qml/qqmldata_p.h
+++ b/src/qml/qml/qqmldata_p.h
@@ -79,7 +79,7 @@ class Q_QML_EXPORT QQmlData : public QAbstractDeclarativeData
 public:
     QQmlData()
         : ownMemory(true), ownContext(false), indestructible(true), explicitIndestructibleSet(false), 
-          hasTaintedV8Object(false), isQueuedForDeletion(false), notifyList(0), context(0), outerContext(0),
+          hasTaintedV8Object(false), isQueuedForDeletion(false), inCreation(false), notifyList(0), context(0), outerContext(0),
           bindings(0), signalHandlers(0), nextContextObject(0), prevContextObject(0), bindingBitsSize(0), bindingBits(0),
           lineNumber(0), columnNumber(0), deferredComponent(0), deferredIdx(0), v8objectid(0), 
           propertyCache(0), guards(0), extendedData(0) {
@@ -114,7 +114,12 @@ public:
     quint32 explicitIndestructibleSet:1;
     quint32 hasTaintedV8Object:1;
     quint32 isQueuedForDeletion:1;
-    quint32 dummy:26;
+    /*
+     * inCreation should be true only when creating top level CPP and QML objects,
+     * v8 GC will check this flag, only deletes the objects when inCreation is false.
+     */
+    quint32 inCreation:1;
+    quint32 dummy:25;
 
     struct NotifyList {
         quint64 connectionMask;
diff --git a/src/qml/qml/qqmlincubator.cpp b/src/qml/qml/qqmlincubator.cpp
index fad2ae2f28..817e7b89e7 100644
--- a/src/qml/qml/qqmlincubator.cpp
+++ b/src/qml/qml/qqmlincubator.cpp
@@ -296,6 +296,7 @@ void QQmlIncubatorPrivate::incubate(QQmlVME::Interrupt &i)
             //see QQmlComponent::beginCreate for explanation of indestructible
             ddata->indestructible = true;
             ddata->explicitIndestructibleSet = true;
+            ddata->inCreation = false;
             q->setInitialState(result);
         }
 
diff --git a/src/qml/qml/qqmlvme.cpp b/src/qml/qml/qqmlvme.cpp
index 985d291a8e..47ea690973 100644
--- a/src/qml/qml/qqmlvme.cpp
+++ b/src/qml/qml/qqmlvme.cpp
@@ -513,6 +513,9 @@ QObject *QQmlVME::run(QList<QQmlError> *errors,
             QQmlData *ddata = QQmlData::get(o);
             Q_ASSERT(ddata);
 
+            if (states.count() == 1)
+                ddata->inCreation = true;
+
             if (instr.isRoot) {
                 if (ddata->context) {
                     Q_ASSERT(ddata->context != CTXT);
@@ -547,6 +550,9 @@ QObject *QQmlVME::run(QList<QQmlError> *errors,
             ddata->ownMemory = false;
             QObjectPrivate::get(o)->declarativeData = ddata;
 
+            if (states.count() == 1)
+                ddata->inCreation = true;
+
             if (type.typePropertyCache && !ddata->propertyCache) {
                 ddata->propertyCache = type.typePropertyCache;
                 ddata->propertyCache->addref();
diff --git a/src/qml/qml/v8/qv8qobjectwrapper.cpp b/src/qml/qml/v8/qv8qobjectwrapper.cpp
index 2d6c5ec24a..f2acac5bbc 100644
--- a/src/qml/qml/v8/qv8qobjectwrapper.cpp
+++ b/src/qml/qml/v8/qv8qobjectwrapper.cpp
@@ -1153,6 +1153,11 @@ void QV8QObjectWrapper::deleteWeakQObject(QV8QObjectResource *resource)
     if (object) {
         QQmlData *ddata = QQmlData::get(object, false);
         if (ddata) {
+            if (ddata->inCreation) {
+                ddata->v8object.MakeWeak(0, WeakQObjectReferenceCallback);
+                return;
+            }
+
             ddata->v8object.Clear();
             if (!object->parent() && !ddata->indestructible) {
                 ddata->isQueuedForDeletion = true;
@@ -1888,7 +1893,7 @@ static v8::Handle<v8::Value> ToString(QV8Engine *engine, QObject *object, int, v
 static v8::Handle<v8::Value> Destroy(QV8Engine *, QObject *object, int argCount, v8::Handle<v8::Object> args)
 {
     QQmlData *ddata = QQmlData::get(object, false);
-    if (!ddata || ddata->indestructible) {
+    if (!ddata || ddata->indestructible || ddata->inCreation) {
         const char *error = "Invalid attempt to destroy() an indestructible object";
         v8::ThrowException(v8::Exception::Error(v8::String::New(error)));
         return v8::Undefined();