Further work towards an exact GC

Add some more convenience in the helper classes
in qscopedvalue_p.h
Make accesses to CallData safer, and change
ExecutionEngine::newObject() to return a safe
pointer.

Change-Id: I980909754ce9681cf6faa1355bab3a1e5d6dd186
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

45 files changed, 1000 insertions, 600 deletions

diff --git a/src/imports/localstorage/plugin.cpp b/src/imports/localstorage/plugin.cpp
index 246ddd96c5..900a5a09a3 100644
--- a/src/imports/localstorage/plugin.cpp
+++ b/src/imports/localstorage/plugin.cpp
@@ -201,12 +201,13 @@ static QString qmlsqldatabase_databaseFile(const QString& connectionName, QV8Eng
 
 static ReturnedValue qmlsqldatabase_rows_index(QQmlSqlDatabaseWrapper *r, ExecutionEngine *v4, quint32 index, bool *hasProperty = 0)
 {
+    Scope scope(v4);
     QV8Engine *v8 = v4->v8Engine;
 
     if (r->sqlQuery.at() == (int)index || r->sqlQuery.seek(index)) {
         QSqlRecord record = r->sqlQuery.record();
         // XXX optimize
-        Object *row = v4->newObject();
+        Scoped<Object> row(scope, v4->newObject());
         for (int ii = 0; ii < record.count(); ++ii) {
             QVariant v = record.value(ii);
             if (v.isNull()) {
@@ -217,11 +218,11 @@ static ReturnedValue qmlsqldatabase_rows_index(QQmlSqlDatabaseWrapper *r, Execut
         }
         if (hasProperty)
             *hasProperty = true;
-        return Value::fromObject(row).asReturnedValue();
+        return row.asReturnedValue();
     } else {
         if (hasProperty)
             *hasProperty = false;
-        return Value::undefinedValue().asReturnedValue();
+        return Encode::undefined();
     }
 }
 
@@ -247,7 +248,7 @@ static ReturnedValue qmlsqldatabase_rows_item(SimpleCallContext *ctx)
 static ReturnedValue qmlsqldatabase_executeSql(SimpleCallContext *ctx)
 {
     QV4::Scope scope(ctx);
-    QQmlSqlDatabaseWrapper *r = ctx->thisObject.as<QQmlSqlDatabaseWrapper>();
+    Scoped<QQmlSqlDatabaseWrapper> r(scope, ctx->thisObject);
     if (!r || r->type != QQmlSqlDatabaseWrapper::Query)
         V4THROW_REFERENCE("Not a SQLDatabase::Query object");
 
@@ -258,7 +259,7 @@ static ReturnedValue qmlsqldatabase_executeSql(SimpleCallContext *ctx)
 
     QSqlDatabase db = r->database;
 
-    QString sql = ctx->argument(0).toQStringNoThrow();
+    QString sql = ctx->argumentCount ? ctx->arguments[0].toQString() : QString();
 
     if (r->readonly && !sql.startsWith(QLatin1String("SELECT"),Qt::CaseInsensitive)) {
         V4THROW_SQL(SQLEXCEPTION_SYNTAX_ERR, QQmlEngine::tr("Read-only Transaction"));
@@ -303,8 +304,8 @@ static ReturnedValue qmlsqldatabase_executeSql(SimpleCallContext *ctx)
             rows->database = db;
             rows->sqlQuery = query;
 
-            Object *resultObject = ctx->engine->newObject();
-            result = Value::fromObject(resultObject);
+            Scoped<Object> resultObject(scope, ctx->engine->newObject());
+            result = resultObject.asValue();
             // XXX optimize
             resultObject->put(ctx->engine->newIdentifier("rowsAffected"), Value::fromInt32(query.numRowsAffected()));
             resultObject->put(ctx->engine->newIdentifier("insertId"), engine->toString(query.lastInsertId().toString()));
@@ -328,16 +329,16 @@ static ReturnedValue qmlsqldatabase_changeVersion(SimpleCallContext *ctx)
 
     Scope scope(ctx);
 
-    QQmlSqlDatabaseWrapper *r = ctx->thisObject.as<QQmlSqlDatabaseWrapper>();
+    Scoped<QQmlSqlDatabaseWrapper> r(scope, ctx->thisObject);
     if (!r || r->type != QQmlSqlDatabaseWrapper::Database)
         V4THROW_REFERENCE("Not a SQLDatabase object");
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
     QSqlDatabase db = r->database;
-    QString from_version = ctx->arguments[0].toQStringNoThrow();
-    QString to_version = ctx->arguments[1].toQStringNoThrow();
-    Value callback = ctx->argument(2);
+    QString from_version = ctx->arguments[0].toQString();
+    QString to_version = ctx->arguments[1].toQString();
+    Scoped<FunctionObject> callback(scope, ctx->argument(2));
 
     if (from_version != r->version)
         V4THROW_SQL(SQLEXCEPTION_VERSION_ERR, QQmlEngine::tr("Version mismatch: expected %1, found %2").arg(from_version).arg(r->version));
@@ -350,7 +351,7 @@ static ReturnedValue qmlsqldatabase_changeVersion(SimpleCallContext *ctx)
     w->inTransaction = true;
 
     bool ok = true;
-    if (FunctionObject *f = callback.asFunctionObject()) {
+    if (!!callback) {
         ok = false;
         db.transaction();
 
@@ -358,7 +359,7 @@ static ReturnedValue qmlsqldatabase_changeVersion(SimpleCallContext *ctx)
         callData->thisObject = engine->global();
         callData->args[0] = Value::fromObject(w);
         try {
-            f->call(callData);
+            callback->call(callData);
         } catch (Exception &) {
             db.rollback();
             throw;
@@ -442,24 +443,25 @@ static ReturnedValue qmlsqldatabase_read_transaction(SimpleCallContext *ctx)
 QQmlSqlDatabaseData::QQmlSqlDatabaseData(QV8Engine *engine)
 {
     ExecutionEngine *v4 = QV8Engine::getV4(engine);
+    Scope scope(v4);
     {
-        Object *proto = v4->newObject();
+        Scoped<Object> proto(scope, v4->newObject());
         proto->defineDefaultProperty(v4, QStringLiteral("transaction"), qmlsqldatabase_transaction);
         proto->defineDefaultProperty(v4, QStringLiteral("readTransaction"), qmlsqldatabase_read_transaction);
         Property *p = proto->insertMember(v4->newString(QStringLiteral("version")),
                                           Attr_Accessor|Attr_NotConfigurable|Attr_NotEnumerable);
         p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->newString(QStringLiteral("version")), qmlsqldatabase_version));
         proto->defineDefaultProperty(v4, QStringLiteral("changeVersion"), qmlsqldatabase_changeVersion);
-        databaseProto = Value::fromObject(proto);
+        databaseProto = proto;
     }
 
     {
-        Object *proto = v4->newObject();
+        Scoped<Object> proto(scope, v4->newObject());
         proto->defineDefaultProperty(v4, QStringLiteral("executeSql"), qmlsqldatabase_executeSql);
-        queryProto = Value::fromObject(proto);
+        queryProto = proto;
     }
     {
-        Object *proto = v4->newObject();
+        Scoped<Object> proto(scope, v4->newObject());
         proto->defineDefaultProperty(v4, QStringLiteral("item"), qmlsqldatabase_rows_item);
         Property *p = proto->insertMember(v4->newString(QStringLiteral("length")),
                                           Attr_Accessor|Attr_NotConfigurable|Attr_NotEnumerable);
@@ -468,7 +470,7 @@ QQmlSqlDatabaseData::QQmlSqlDatabaseData(QV8Engine *engine)
                                 Attr_Accessor|Attr_NotConfigurable|Attr_NotEnumerable);
         p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->newString(QStringLiteral("forwardOnly")), qmlsqldatabase_rows_forwardOnly));
         p->setSetter(v4->newBuiltinFunction(v4->rootContext, v4->newString(QStringLiteral("setForwardOnly")), qmlsqldatabase_rows_setForwardOnly));
-        rowsProto = Value::fromObject(proto);
+        rowsProto = proto;
     }
 }
 
diff --git a/src/imports/xmllistmodel/qqmlxmllistmodel.cpp b/src/imports/xmllistmodel/qqmlxmllistmodel.cpp
index 9f6437625d..f87273be40 100644
--- a/src/imports/xmllistmodel/qqmlxmllistmodel.cpp
+++ b/src/imports/xmllistmodel/qqmlxmllistmodel.cpp
@@ -923,13 +923,14 @@ QQmlV4Handle QQuickXmlListModel::get(int index) const
     QQmlEngine *engine = qmlContext(this)->engine();
     QV8Engine *v8engine = QQmlEnginePrivate::getV8Engine(engine);
     ExecutionEngine *v4engine = QV8Engine::getV4(v8engine);
-    Object *o = v4engine->newObject();
+    Scope scope(v4engine);
+    Scoped<Object> o(scope, v4engine->newObject());
     for (int ii = 0; ii < d->roleObjects.count(); ++ii) {
         Property *p = o->insertMember(v4engine->newIdentifier(d->roleObjects[ii]->name()), PropertyAttributes());
         p->value = Value::fromReturnedValue(v8engine->fromVariant(d->data.value(ii).value(index)));
     }
 
-    return QQmlV4Handle(Value::fromObject(o));
+    return QQmlV4Handle(o.asValue());
 }
 
 /*!
diff --git a/src/particles/qquickv4particledata.cpp b/src/particles/qquickv4particledata.cpp
index 1a574600e0..23018677ea 100644
--- a/src/particles/qquickv4particledata.cpp
+++ b/src/particles/qquickv4particledata.cpp
@@ -328,7 +328,8 @@ static QV4::ReturnedValue particleData_curSize(QV4::SimpleCallContext *ctx)
 }
 #define COLOR_GETTER_AND_SETTER(VAR, NAME) static QV4::ReturnedValue particleData_get_ ## NAME (QV4::SimpleCallContext *ctx) \
 { \
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum) \
         ctx->throwError(QStringLiteral("Not a valid ParticleData object")); \
 \
@@ -337,18 +338,21 @@ static QV4::ReturnedValue particleData_curSize(QV4::SimpleCallContext *ctx)
 \
 static QV4::ReturnedValue particleData_set_ ## NAME (QV4::SimpleCallContext *ctx)\
 {\
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum)\
         ctx->throwError(QStringLiteral("Not a valid ParticleData object"));\
 \
-    r->datum->color. VAR = qMin(255, qMax(0, (int)floor(ctx->argument(0).toNumber() * 255.0)));\
+    double d = ctx->argumentCount ? ctx->arguments[0].toNumber() : 0; \
+    r->datum->color. VAR = qMin(255, qMax(0, (int)floor(d * 255.0)));\
     return QV4::Encode::undefined(); \
 }
 
 
 #define SEMIBOOL_GETTER_AND_SETTER(VARIABLE) static QV4::ReturnedValue particleData_get_ ## VARIABLE (QV4::SimpleCallContext *ctx) \
 { \
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum) \
         ctx->throwError(QStringLiteral("Not a valid ParticleData object")); \
 \
@@ -357,17 +361,19 @@ static QV4::ReturnedValue particleData_set_ ## NAME (QV4::SimpleCallContext *ctx
 \
 static QV4::ReturnedValue particleData_set_ ## VARIABLE (QV4::SimpleCallContext *ctx)\
 {\
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum)\
         ctx->throwError(QStringLiteral("Not a valid ParticleData object"));\
 \
-    r->datum-> VARIABLE = ctx->argument(0).toBoolean() ? 1.0 : 0.0;\
+    r->datum-> VARIABLE = (ctx->argumentCount && ctx->arguments[0].toBoolean()) ? 1.0 : 0.0;\
     return QV4::Encode::undefined(); \
 }
 
 #define FLOAT_GETTER_AND_SETTER(VARIABLE) static QV4::ReturnedValue particleData_get_ ## VARIABLE (QV4::SimpleCallContext *ctx) \
 { \
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum) \
         ctx->throwError(QStringLiteral("Not a valid ParticleData object")); \
 \
@@ -376,17 +382,19 @@ static QV4::ReturnedValue particleData_set_ ## VARIABLE (QV4::SimpleCallContext
 \
 static QV4::ReturnedValue particleData_set_ ## VARIABLE (QV4::SimpleCallContext *ctx)\
 {\
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum)\
         ctx->throwError(QStringLiteral("Not a valid ParticleData object"));\
 \
-    r->datum-> VARIABLE = ctx->argument(0).toNumber();\
+    r->datum-> VARIABLE = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();\
     return QV4::Encode::undefined(); \
 }
 
 #define FAKE_FLOAT_GETTER_AND_SETTER(VARIABLE, GETTER, SETTER) static QV4::ReturnedValue particleData_get_ ## VARIABLE (QV4::SimpleCallContext *ctx) \
 { \
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum) \
         ctx->throwError(QStringLiteral("Not a valid ParticleData object")); \
 \
@@ -395,11 +403,12 @@ static QV4::ReturnedValue particleData_set_ ## VARIABLE (QV4::SimpleCallContext
 \
 static QV4::ReturnedValue particleData_set_ ## VARIABLE (QV4::SimpleCallContext *ctx)\
 {\
-    QV4ParticleData *r = ctx->thisObject.as<QV4ParticleData>(); \
+    QV4::Scope scope(ctx); \
+    QV4::Scoped<QV4ParticleData> r(scope, ctx->thisObject); \
     if (!r || !r->datum)\
         ctx->throwError(QStringLiteral("Not a valid ParticleData object"));\
 \
-    r->datum-> SETTER ( ctx->argument(0).toNumber() );\
+    r->datum-> SETTER (ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN());\
     return QV4::Encode::undefined(); \
 }
 
@@ -444,7 +453,8 @@ FAKE_FLOAT_GETTER_AND_SETTER(curAY, curAY, setInstantaneousAY)
 QV8ParticleDataDeletable::QV8ParticleDataDeletable(QV8Engine *engine)
 {
     QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
-    QV4::Object *p = v4->newObject();
+    QV4::Scope scope(v4);
+    QV4::Scoped<QV4::Object> p(scope, v4->newObject());
 
     p->defineDefaultProperty(v4, QStringLiteral("discard"), particleData_discard);
     p->defineDefaultProperty(v4, QStringLiteral("lifeLeft"), particleData_lifeLeft);
@@ -485,7 +495,7 @@ QV8ParticleDataDeletable::QV8ParticleDataDeletable(QV8Engine *engine)
     REGISTER_ACCESSOR(p, v4, blue, blue);
     REGISTER_ACCESSOR(p, v4, alpha, alpha);
 
-    proto = QV4::Value::fromObject(p);
+    proto = p;
 }
 
 QV8ParticleDataDeletable::~QV8ParticleDataDeletable()
diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index b66dd51648..f99463256e 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -286,7 +286,7 @@ QJSValue QJSEngine::evaluate(const QString& program, const QString& fileName, in
 */
 QJSValue QJSEngine::newObject()
 {
-    return new QJSValuePrivate(d->m_v4Engine->newObject());
+    return new QJSValuePrivate(d->m_v4Engine->newObject()->getPointer());
 }
 
 /*!
diff --git a/src/qml/jsruntime/qv4argumentsobject.cpp b/src/qml/jsruntime/qv4argumentsobject.cpp
index 6c028de372..62937921aa 100644
--- a/src/qml/jsruntime/qv4argumentsobject.cpp
+++ b/src/qml/jsruntime/qv4argumentsobject.cpp
@@ -84,12 +84,12 @@ ArgumentsObject::ArgumentsObject(CallContext *context)
         ensureArrayAttributes();
         context->engine->requireArgumentsAccessors(numAccessors);
         for (uint i = 0; i < (uint)numAccessors; ++i) {
-            mappedArguments.append(context->argument(i));
+            mappedArguments.append(context->arguments[i]);
             arrayData[i] = context->engine->argumentsAccessors.at(i);
             arrayAttributes[i] = Attr_Accessor;
         }
         for (uint i = numAccessors; i < argCount; ++i) {
-            arrayData[i] = Property::fromValue(context->argument(i));
+            arrayData[i] = Property::fromValue(context->arguments[i]);
             arrayAttributes[i] = Attr_Data;
         }
         arrayDataLen = argCount;
@@ -160,7 +160,7 @@ ReturnedValue ArgumentsGetterFunction::call(Managed *getter, CallData *callData)
         getter->engine()->current->throwTypeError();
 
     assert(g->index < o->context->argumentCount);
-    return o->context->argument(g->index).asReturnedValue();
+    return o->context->argument(g->index);
 }
 
 DEFINE_MANAGED_VTABLE(ArgumentsSetterFunction);
diff --git a/src/qml/jsruntime/qv4arrayobject.cpp b/src/qml/jsruntime/qv4arrayobject.cpp
index 1f09b97d5c..ce6bdca627 100644
--- a/src/qml/jsruntime/qv4arrayobject.cpp
+++ b/src/qml/jsruntime/qv4arrayobject.cpp
@@ -131,9 +131,8 @@ uint ArrayPrototype::getLength(ExecutionContext *ctx, Object *o)
 
 ReturnedValue ArrayPrototype::method_isArray(SimpleCallContext *ctx)
 {
-    Value arg = ctx->argument(0);
-    bool isArray = arg.asArrayObject();
-    return Value::fromBoolean(isArray).asReturnedValue();
+    bool isArray = ctx->argumentCount ? ctx->arguments[0].asArrayObject() : false;
+    return Encode(isArray);
 }
 
 ReturnedValue ArrayPrototype::method_toString(SimpleCallContext *ctx)
@@ -174,13 +173,11 @@ ReturnedValue ArrayPrototype::method_concat(SimpleCallContext *ctx)
     }
 
     for (uint i = 0; i < ctx->argumentCount; ++i) {
-        Value arg = ctx->argument(i);
-
-        if (ArrayObject *elt = arg.asArrayObject())
+        if (ArrayObject *elt = ctx->arguments[i].asArrayObject())
             result->arrayConcat(elt);
 
         else
-            result->arraySet(getLength(ctx, result.getPointer()), arg);
+            result->arraySet(getLength(ctx, result.getPointer()), ctx->arguments[i]);
     }
 
     return result.asReturnedValue();
@@ -189,13 +186,13 @@ ReturnedValue ArrayPrototype::method_concat(SimpleCallContext *ctx)
 ReturnedValue ArrayPrototype::method_join(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Value arg = ctx->argument(0);
+    ScopedValue arg(scope, ctx->argument(0));
 
     QString r4;
-    if (arg.isUndefined())
+    if (arg->isUndefined())
         r4 = QStringLiteral(",");
     else
-        r4 = arg.toString(ctx)->toQString();
+        r4 = arg->toQString();
 
     Scoped<Object> self(scope, ctx->thisObject);
     ScopedValue length(scope, self->get(ctx->engine->id_length));
@@ -276,9 +273,9 @@ ReturnedValue ArrayPrototype::method_push(SimpleCallContext *ctx)
     if (len + ctx->argumentCount < len) {
         // ughh...
         double l = len;
-        for (double i = 0; i < ctx->argumentCount; ++i) {
+        for (int i = 0; i < ctx->argumentCount; ++i) {
             Value idx = Value::fromDouble(l + i);
-            instance->put(idx.toString(ctx), ctx->argument(i));
+            instance->put(idx.toString(ctx), ctx->arguments[i]);
         }
         double newLen = l + ctx->argumentCount;
         if (!instance->isArrayObject())
@@ -290,7 +287,7 @@ ReturnedValue ArrayPrototype::method_push(SimpleCallContext *ctx)
 
     if (!instance->protoHasArray() && instance->arrayDataLen <= len) {
         for (uint i = 0; i < ctx->argumentCount; ++i) {
-            Value v = ctx->argument(i);
+            Value v = ctx->arguments[i];
 
             if (!instance->sparseArray) {
                 if (len >= instance->arrayAlloc)
@@ -307,7 +304,7 @@ ReturnedValue ArrayPrototype::method_push(SimpleCallContext *ctx)
         }
     } else {
         for (uint i = 0; i < ctx->argumentCount; ++i)
-            instance->putIndexed(len + i, ctx->argument(i));
+            instance->putIndexed(len + i, ctx->arguments[i]);
         len += ctx->argumentCount;
     }
     if (instance->isArrayObject())
@@ -408,7 +405,7 @@ ReturnedValue ArrayPrototype::method_slice(SimpleCallContext *ctx)
 
     Scoped<ArrayObject> result(scope, ctx->engine->newArrayObject());
     uint len = ArrayPrototype::getLength(ctx, o);
-    double s = ctx->argument(0).toInteger();
+    double s = ScopedValue(scope, ctx->argument(0))->toInteger();
     uint start;
     if (s < 0)
         start = (uint)qMax(len + s, 0.);
@@ -417,8 +414,8 @@ ReturnedValue ArrayPrototype::method_slice(SimpleCallContext *ctx)
     else
         start = (uint) s;
     uint end = len;
-    if (!ctx->argument(1).isUndefined()) {
-        double e = ctx->argument(1).toInteger();
+    if (ctx->argumentCount > 1 && !ctx->arguments[1].isUndefined()) {
+        double e = ctx->arguments[1].toInteger();
         if (e < 0)
             end = (uint)qMax(len + e, 0.);
         else if (e > len)
@@ -442,12 +439,13 @@ ReturnedValue ArrayPrototype::method_slice(SimpleCallContext *ctx)
 
 ReturnedValue ArrayPrototype::method_sort(SimpleCallContext *ctx)
 {
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scope scope(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    Value comparefn = ctx->argument(0);
-    instance->arraySort(ctx, instance, comparefn, len);
+    ScopedValue comparefn(scope, ctx->argument(0));
+    instance->arraySort(ctx, instance.getPointer(), comparefn, len);
     return ctx->thisObject.asReturnedValue();
 }
 
@@ -459,14 +457,14 @@ ReturnedValue ArrayPrototype::method_splice(SimpleCallContext *ctx)
 
     Scoped<ArrayObject> newArray(scope, ctx->engine->newArrayObject());
 
-    double rs = ctx->argument(0).toInteger();
+    double rs = ScopedValue(scope, ctx->argument(0))->toInteger();
     uint start;
     if (rs < 0)
         start = (uint) qMax(0., len + rs);
     else
         start = (uint) qMin(rs, (double)len);
 
-    uint deleteCount = (uint)qMin(qMax(ctx->argument(1).toInteger(), 0.), (double)(len - start));
+    uint deleteCount = (uint)qMin(qMax(ScopedValue(scope, ctx->argument(1))->toInteger(), 0.), (double)(len - start));
 
     newArray->arrayReserve(deleteCount);
     Property *pd = newArray->arrayData;
@@ -505,7 +503,7 @@ ReturnedValue ArrayPrototype::method_splice(SimpleCallContext *ctx)
     }
 
     for (uint i = 0; i < itemCount; ++i)
-        instance->putIndexed(start + i, ctx->argument(i + 2));
+        instance->putIndexed(start + i, ctx->arguments[i + 2]);
 
     ctx->strictMode = true;
     instance->put(ctx->engine->id_length, Value::fromDouble(len - deleteCount + itemCount));
@@ -520,8 +518,9 @@ ReturnedValue ArrayPrototype::method_unshift(SimpleCallContext *ctx)
     uint len = getLength(ctx, instance);
 
     if (!instance->protoHasArray() && instance->arrayDataLen <= len) {
+        ScopedValue v(scope);
         for (int i = ctx->argumentCount - 1; i >= 0; --i) {
-            Value v = ctx->argument(i);
+            v = ctx->argument(i);
 
             if (!instance->sparseArray) {
                 if (!instance->arrayOffset)
@@ -551,7 +550,7 @@ ReturnedValue ArrayPrototype::method_unshift(SimpleCallContext *ctx)
                 instance->deleteIndexedProperty(k + ctx->argumentCount - 1);
         }
         for (uint i = 0; i < ctx->argumentCount; ++i)
-            instance->putIndexed(i, ctx->argument(i));
+            instance->putIndexed(i, ctx->arguments[i]);
     }
 
     uint newLen = len + ctx->argumentCount;
@@ -578,14 +577,14 @@ ReturnedValue ArrayPrototype::method_indexOf(SimpleCallContext *ctx)
     uint fromIndex = 0;
 
     if (ctx->argumentCount >= 1)
-        searchValue = ctx->argument(0);
+        searchValue = ctx->arguments[0];
     else
         searchValue = Value::undefinedValue();
 
     if (ctx->argumentCount >= 2) {
-        double f = ctx->argument(1).toInteger();
+        double f = ctx->arguments[1].toInteger();
         if (f >= len)
-            return Value::fromInt32(-1).asReturnedValue();
+            return Encode(-1);
         if (f < 0)
             f = qMax(len + f, 0.);
         fromIndex = (uint) f;
@@ -597,9 +596,9 @@ ReturnedValue ArrayPrototype::method_indexOf(SimpleCallContext *ctx)
             bool exists;
             v = instance->getIndexed(k, &exists);
             if (exists && __qmljs_strict_equal(v, searchValue))
-                return Value::fromDouble(k).asReturnedValue();
+                return Encode(k);
         }
-        return Value::fromInt32(-1).asReturnedValue();
+        return Encode(-1);
     }
 
     return instance->arrayIndexOf(searchValue, fromIndex, len, ctx, instance);
@@ -623,13 +622,13 @@ ReturnedValue ArrayPrototype::method_lastIndexOf(SimpleCallContext *ctx)
         searchValue = Value::undefinedValue();
 
     if (ctx->argumentCount >= 2) {
-        double f = ctx->argument(1).toInteger();
+        double f = ctx->arguments[1].toInteger();
         if (f > 0)
             f = qMin(f, (double)(len - 1));
         else if (f < 0) {
             f = len + f;
             if (f < 0)
-                return Value::fromInt32(-1).asReturnedValue();
+                return Encode(-1);
         }
         fromIndex = (uint) f + 1;
     }
@@ -648,19 +647,17 @@ ReturnedValue ArrayPrototype::method_lastIndexOf(SimpleCallContext *ctx)
 ReturnedValue ArrayPrototype::method_every(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
-    Value thisArg = ctx->argument(1);
-
     ScopedCallData callData(scope, 3);
-    callData->args[2] = Value::fromObject(instance);
-    callData->thisObject = thisArg;
+    callData->args[2] = instance.asValue();
+    callData->thisObject = ctx->argument(1);
     ScopedValue r(scope);
     ScopedValue v(scope);
 
@@ -682,17 +679,17 @@ ReturnedValue ArrayPrototype::method_every(SimpleCallContext *ctx)
 ReturnedValue ArrayPrototype::method_some(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
     ScopedCallData callData(scope, 3);
     callData->thisObject = ctx->argument(1);
-    callData->args[2] = Value::fromObject(instance);
+    callData->args[2] = instance;
     ScopedValue v(scope);
 
     for (uint k = 0; k < len; ++k) {
@@ -705,25 +702,25 @@ ReturnedValue ArrayPrototype::method_some(SimpleCallContext *ctx)
         callData->args[1] = Value::fromDouble(k);
         Value r = Value::fromReturnedValue(callback->call(callData));
         if (r.toBoolean())
-            return Value::fromBoolean(true).asReturnedValue();
+            return Encode(true);
     }
-    return Value::fromBoolean(false).asReturnedValue();
+    return Encode(false);
 }
 
 ReturnedValue ArrayPrototype::method_forEach(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
     ScopedCallData callData(scope, 3);
     callData->thisObject = ctx->argument(1);
-    callData->args[2] = Value::fromObject(instance);
+    callData->args[2] = instance;
 
     ScopedValue v(scope);
     for (uint k = 0; k < len; ++k) {
@@ -736,30 +733,28 @@ ReturnedValue ArrayPrototype::method_forEach(SimpleCallContext *ctx)
         callData->args[1] = Value::fromDouble(k);
         callback->call(callData);
     }
-    return Value::undefinedValue().asReturnedValue();
+    return Encode::undefined();
 }
 
 ReturnedValue ArrayPrototype::method_map(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
-    Value thisArg = ctx->argument(1);
-
     Scoped<ArrayObject> a(scope, ctx->engine->newArrayObject());
     a->arrayReserve(len);
     a->setArrayLengthUnchecked(len);
 
     ScopedValue mapped(scope);
     ScopedCallData callData(scope, 3);
-    callData->thisObject = thisArg;
-    callData->args[2] = Value::fromObject(instance);
+    callData->thisObject = ctx->argument(1);
+    callData->args[2] = instance;
 
     ScopedValue v(scope);
     for (uint k = 0; k < len; ++k) {
@@ -779,23 +774,21 @@ ReturnedValue ArrayPrototype::method_map(SimpleCallContext *ctx)
 ReturnedValue ArrayPrototype::method_filter(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
-    Value thisArg = ctx->argument(1);
-
     Scoped<ArrayObject> a(scope, ctx->engine->newArrayObject());
     a->arrayReserve(len);
 
     ScopedValue selected(scope);
     ScopedCallData callData(scope, 3);
-    callData->thisObject = thisArg;
-    callData->args[2] = Value::fromObject(instance);
+    callData->thisObject = ctx->argument(1);
+    callData->args[2] = instance;
 
     ScopedValue v(scope);
 
@@ -820,11 +813,11 @@ ReturnedValue ArrayPrototype::method_filter(SimpleCallContext *ctx)
 ReturnedValue ArrayPrototype::method_reduce(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
@@ -849,7 +842,7 @@ ReturnedValue ArrayPrototype::method_reduce(SimpleCallContext *ctx)
     ScopedCallData callData(scope, 4);
     callData->thisObject = Value::undefinedValue();
     callData->args[0] = acc;
-    callData->args[3] = Value::fromObject(instance);
+    callData->args[3] = instance;
 
     while (k < len) {
         bool kPresent;
@@ -868,18 +861,18 @@ ReturnedValue ArrayPrototype::method_reduce(SimpleCallContext *ctx)
 ReturnedValue ArrayPrototype::method_reduceRight(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Object *instance = ctx->thisObject.toObject(ctx);
+    Scoped<Object> instance(scope, ctx->thisObject.toObject(ctx));
 
-    uint len = getLength(ctx, instance);
+    uint len = getLength(ctx, instance.getPointer());
 
-    FunctionObject *callback = ctx->argument(0).asFunctionObject();
+    Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
         ctx->throwTypeError();
 
     if (len == 0) {
         if (ctx->argumentCount == 1)
             ctx->throwTypeError();
-        return ctx->argument(1).asReturnedValue();
+        return ctx->argument(1);
     }
 
     uint k = len;
@@ -901,7 +894,7 @@ ReturnedValue ArrayPrototype::method_reduceRight(SimpleCallContext *ctx)
 
     ScopedCallData callData(scope, 4);
     callData->thisObject = Value::undefinedValue();
-    callData->args[3] = Value::fromObject(instance);
+    callData->args[3] = instance;
 
     while (k > 0) {
         bool kPresent;
diff --git a/src/qml/jsruntime/qv4context.cpp b/src/qml/jsruntime/qv4context.cpp
index 6a97b9cfab..01cb2dd780 100644
--- a/src/qml/jsruntime/qv4context.cpp
+++ b/src/qml/jsruntime/qv4context.cpp
@@ -64,7 +64,7 @@ CallContext *ExecutionContext::newCallContext(void *stackSpace, FunctionObject *
 
     c->function = function;
     // ###
-    c->arguments = const_cast<Value *>(callData->args);
+    c->arguments = const_cast<SafeValue *>(callData->args);
     c->realArgumentCount = callData->argc;
     c->argumentCount = callData->argc;
     c->thisObject = callData->thisObject;
@@ -135,7 +135,7 @@ CallContext *ExecutionContext::newCallContext(FunctionObject *function, CallData
         std::fill(c->locals, c->locals + function->varCount, Value::undefinedValue());
 
     c->argumentCount = qMax((uint)callData->argc, function->formalParameterCount);
-    c->arguments = c->locals + function->varCount;
+    c->arguments = static_cast<SafeValue *>(c->locals + function->varCount);
     if (callData->argc)
         ::memcpy(c->arguments, callData->args, callData->argc * sizeof(Value));
     if (callData->argc < function->formalParameterCount)
@@ -182,7 +182,7 @@ void ExecutionContext::createMutableBinding(String *name, bool deletable)
         if (ctx->type >= Type_CallContext) {
             CallContext *c = static_cast<CallContext *>(ctx);
             if (!c->activation)
-                c->activation = engine->newObject();
+                c->activation = engine->newObject()->getPointer();
             activation = c->activation;
             break;
         }
diff --git a/src/qml/jsruntime/qv4context_p.h b/src/qml/jsruntime/qv4context_p.h
index 0c3b189401..fe15a53fd2 100644
--- a/src/qml/jsruntime/qv4context_p.h
+++ b/src/qml/jsruntime/qv4context_p.h
@@ -148,8 +148,6 @@ struct Q_QML_EXPORT ExecutionContext
     ReturnedValue getPropertyAndBase(String *name, Object **base);
     bool deleteProperty(String *name);
 
-    inline Value argument(unsigned int index = 0);
-
     void mark();
 
     inline CallContext *asCallContext();
@@ -160,9 +158,13 @@ struct SimpleCallContext : public ExecutionContext
 {
     void initSimpleCallContext(ExecutionEngine *engine);
     FunctionObject *function;
-    Value *arguments;
+    SafeValue *arguments;
     unsigned int realArgumentCount;
     unsigned int argumentCount;
+
+    ReturnedValue argument(uint i) {
+        return i < argumentCount ? arguments[i].asReturnedValue() : Value::undefinedValue().asReturnedValue();
+    }
 };
 
 struct CallContext : public SimpleCallContext
@@ -196,16 +198,6 @@ struct WithContext : public ExecutionContext
     void initWithContext(ExecutionContext *p, Object *with);
 };
 
-inline Value ExecutionContext::argument(unsigned int index)
-{
-    if (type >= Type_SimpleCallContext) {
-        CallContext *ctx = static_cast<CallContext *>(this);
-        if (index < ctx->argumentCount)
-            return ctx->arguments[index];
-    }
-    return Value::undefinedValue();
-}
-
 inline CallContext *ExecutionContext::asCallContext()
 {
     return type >= Type_CallContext ? static_cast<CallContext *>(this) : 0;
diff --git a/src/qml/jsruntime/qv4dateobject.cpp b/src/qml/jsruntime/qv4dateobject.cpp
index 76d712656a..14e54a2e53 100644
--- a/src/qml/jsruntime/qv4dateobject.cpp
+++ b/src/qml/jsruntime/qv4dateobject.cpp
@@ -772,20 +772,22 @@ double DatePrototype::getThisDate(ExecutionContext *ctx)
 
 ReturnedValue DatePrototype::method_parse(SimpleCallContext *ctx)
 {
-    return Encode(ParseString(ctx->argument(0).toString(ctx)->toQString()));
+    if (!ctx->argumentCount)
+        return Encode(qSNaN());
+    return Encode(ParseString(ctx->arguments[0].toString(ctx)->toQString()));
 }
 
 ReturnedValue DatePrototype::method_UTC(SimpleCallContext *ctx)
 {
     const int numArgs = ctx->argumentCount;
     if (numArgs >= 2) {
-        double year  = ctx->argument(0).toNumber();
-        double month = ctx->argument(1).toNumber();
-        double day   = numArgs >= 3 ? ctx->argument(2).toNumber() : 1;
-        double hours = numArgs >= 4 ? ctx->argument(3).toNumber() : 0;
-        double mins  = numArgs >= 5 ? ctx->argument(4).toNumber() : 0;
-        double secs  = numArgs >= 6 ? ctx->argument(5).toNumber() : 0;
-        double ms    = numArgs >= 7 ? ctx->argument(6).toNumber() : 0;
+        double year  = ctx->arguments[0].toNumber();
+        double month = ctx->arguments[1].toNumber();
+        double day   = numArgs >= 3 ? ctx->arguments[2].toNumber() : 1;
+        double hours = numArgs >= 4 ? ctx->arguments[3].toNumber() : 0;
+        double mins  = numArgs >= 5 ? ctx->arguments[4].toNumber() : 0;
+        double secs  = numArgs >= 6 ? ctx->arguments[5].toNumber() : 0;
+        double ms    = numArgs >= 7 ? ctx->arguments[6].toNumber() : 0;
         if (year >= 0 && year <= 99)
             year += 1900;
         double t = MakeDate(MakeDay(year, month, day),
@@ -996,22 +998,25 @@ ReturnedValue DatePrototype::method_getTimezoneOffset(SimpleCallContext *ctx)
 
 ReturnedValue DatePrototype::method_setTime(SimpleCallContext *ctx)
 {
-    DateObject *self = ctx->thisObject.asDateObject();
+    Scope scope(ctx);
+    Scoped<DateObject> self(scope, ctx->thisObject);
     if (!self)
         ctx->throwTypeError();
 
-    self->value.setDouble(TimeClip(ctx->argument(0).toNumber()));
+    double t = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    self->value.setDouble(TimeClip(t));
     return self->value.asReturnedValue();
 }
 
 ReturnedValue DatePrototype::method_setMilliseconds(SimpleCallContext *ctx)
 {
-    DateObject *self = ctx->thisObject.asDateObject();
+    Scope scope(ctx);
+    Scoped<DateObject> self(scope, ctx->thisObject);
     if (!self)
         ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
-    double ms = ctx->argument(0).toNumber();
+    double ms = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     self->value.setDouble(TimeClip(UTC(MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), SecFromTime(t), ms)))));
     return self->value.asReturnedValue();
 }
@@ -1023,7 +1028,7 @@ ReturnedValue DatePrototype::method_setUTCMilliseconds(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double ms = ctx->argument(0).toNumber();
+    double ms = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     self->value.setDouble(TimeClip(UTC(MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), SecFromTime(t), ms)))));
     return self->value.asReturnedValue();
 }
@@ -1035,8 +1040,8 @@ ReturnedValue DatePrototype::method_setSeconds(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
-    double sec = ctx->argument(0).toNumber();
-    double ms = (ctx->argumentCount < 2) ? msFromTime(t) : ctx->argument(1).toNumber();
+    double sec = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double ms = (ctx->argumentCount < 2) ? msFromTime(t) : ctx->arguments[1].toNumber();
     t = TimeClip(UTC(MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), sec, ms))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1049,8 +1054,8 @@ ReturnedValue DatePrototype::method_setUTCSeconds(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double sec = ctx->argument(0).toNumber();
-    double ms = (ctx->argumentCount < 2) ? msFromTime(t) : ctx->argument(1).toNumber();
+    double sec = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double ms = (ctx->argumentCount < 2) ? msFromTime(t) : ctx->arguments[1].toNumber();
     t = TimeClip(UTC(MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), sec, ms))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1063,9 +1068,9 @@ ReturnedValue DatePrototype::method_setMinutes(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
-    double min = ctx->argument(0).toNumber();
-    double sec = (ctx->argumentCount < 2) ? SecFromTime(t) : ctx->argument(1).toNumber();
-    double ms = (ctx->argumentCount < 3) ? msFromTime(t) : ctx->argument(2).toNumber();
+    double min = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double sec = (ctx->argumentCount < 2) ? SecFromTime(t) : ctx->arguments[1].toNumber();
+    double ms = (ctx->argumentCount < 3) ? msFromTime(t) : ctx->arguments[2].toNumber();
     t = TimeClip(UTC(MakeDate(Day(t), MakeTime(HourFromTime(t), min, sec, ms))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1078,9 +1083,9 @@ ReturnedValue DatePrototype::method_setUTCMinutes(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double min = ctx->argument(0).toNumber();
-    double sec = (ctx->argumentCount < 2) ? SecFromTime(t) : ctx->argument(1).toNumber();
-    double ms = (ctx->argumentCount < 3) ? msFromTime(t) : ctx->argument(2).toNumber();
+    double min = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double sec = (ctx->argumentCount < 2) ? SecFromTime(t) : ctx->arguments[1].toNumber();
+    double ms = (ctx->argumentCount < 3) ? msFromTime(t) : ctx->arguments[2].toNumber();
     t = TimeClip(UTC(MakeDate(Day(t), MakeTime(HourFromTime(t), min, sec, ms))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1093,10 +1098,10 @@ ReturnedValue DatePrototype::method_setHours(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
-    double hour = ctx->argument(0).toNumber();
-    double min = (ctx->argumentCount < 2) ? MinFromTime(t) : ctx->argument(1).toNumber();
-    double sec = (ctx->argumentCount < 3) ? SecFromTime(t) : ctx->argument(2).toNumber();
-    double ms = (ctx->argumentCount < 4) ? msFromTime(t) : ctx->argument(3).toNumber();
+    double hour = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double min = (ctx->argumentCount < 2) ? MinFromTime(t) : ctx->arguments[1].toNumber();
+    double sec = (ctx->argumentCount < 3) ? SecFromTime(t) : ctx->arguments[2].toNumber();
+    double ms = (ctx->argumentCount < 4) ? msFromTime(t) : ctx->arguments[3].toNumber();
     t = TimeClip(UTC(MakeDate(Day(t), MakeTime(hour, min, sec, ms))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1109,10 +1114,10 @@ ReturnedValue DatePrototype::method_setUTCHours(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double hour = ctx->argument(0).toNumber();
-    double min = (ctx->argumentCount < 2) ? MinFromTime(t) : ctx->argument(1).toNumber();
-    double sec = (ctx->argumentCount < 3) ? SecFromTime(t) : ctx->argument(2).toNumber();
-    double ms = (ctx->argumentCount < 4) ? msFromTime(t) : ctx->argument(3).toNumber();
+    double hour = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double min = (ctx->argumentCount < 2) ? MinFromTime(t) : ctx->arguments[1].toNumber();
+    double sec = (ctx->argumentCount < 3) ? SecFromTime(t) : ctx->arguments[2].toNumber();
+    double ms = (ctx->argumentCount < 4) ? msFromTime(t) : ctx->arguments[3].toNumber();
     t = TimeClip(UTC(MakeDate(Day(t), MakeTime(hour, min, sec, ms))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1125,7 +1130,7 @@ ReturnedValue DatePrototype::method_setDate(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
-    double date = ctx->argument(0).toNumber();
+    double date = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     t = TimeClip(UTC(MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), date), TimeWithinDay(t))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1138,7 +1143,7 @@ ReturnedValue DatePrototype::method_setUTCDate(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double date = ctx->argument(0).toNumber();
+    double date = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     t = TimeClip(UTC(MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), date), TimeWithinDay(t))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1151,8 +1156,8 @@ ReturnedValue DatePrototype::method_setMonth(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
-    double month = ctx->argument(0).toNumber();
-    double date = (ctx->argumentCount < 2) ? DateFromTime(t) : ctx->argument(1).toNumber();
+    double month = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double date = (ctx->argumentCount < 2) ? DateFromTime(t) : ctx->arguments[1].toNumber();
     t = TimeClip(UTC(MakeDate(MakeDay(YearFromTime(t), month, date), TimeWithinDay(t))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1165,8 +1170,8 @@ ReturnedValue DatePrototype::method_setUTCMonth(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double month = ctx->argument(0).toNumber();
-    double date = (ctx->argumentCount < 2) ? DateFromTime(t) : ctx->argument(1).toNumber();
+    double month = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double date = (ctx->argumentCount < 2) ? DateFromTime(t) : ctx->arguments[1].toNumber();
     t = TimeClip(UTC(MakeDate(MakeDay(YearFromTime(t), month, date), TimeWithinDay(t))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1183,7 +1188,7 @@ ReturnedValue DatePrototype::method_setYear(SimpleCallContext *ctx)
         t = 0;
     else
         t = LocalTime(t);
-    double year = ctx->argument(0).toNumber();
+    double year = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     double r;
     if (std::isnan(year)) {
         r = qSNaN();
@@ -1205,9 +1210,9 @@ ReturnedValue DatePrototype::method_setUTCFullYear(SimpleCallContext *ctx)
         ctx->throwTypeError();
 
     double t = self->value.asDouble();
-    double year = ctx->argument(0).toNumber();
-    double month = (ctx->argumentCount < 2) ? MonthFromTime(t) : ctx->argument(1).toNumber();
-    double date = (ctx->argumentCount < 3) ? DateFromTime(t) : ctx->argument(2).toNumber();
+    double year = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double month = (ctx->argumentCount < 2) ? MonthFromTime(t) : ctx->arguments[1].toNumber();
+    double date = (ctx->argumentCount < 3) ? DateFromTime(t) : ctx->arguments[2].toNumber();
     t = TimeClip(UTC(MakeDate(MakeDay(year, month, date), TimeWithinDay(t))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
@@ -1222,9 +1227,9 @@ ReturnedValue DatePrototype::method_setFullYear(SimpleCallContext *ctx)
     double t = LocalTime(self->value.asDouble());
     if (std::isnan(t))
         t = 0;
-    double year = ctx->argument(0).toNumber();
-    double month = (ctx->argumentCount < 2) ? MonthFromTime(t) : ctx->argument(1).toNumber();
-    double date = (ctx->argumentCount < 3) ? DateFromTime(t) : ctx->argument(2).toNumber();
+    double year = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
+    double month = (ctx->argumentCount < 2) ? MonthFromTime(t) : ctx->arguments[1].toNumber();
+    double date = (ctx->argumentCount < 3) ? DateFromTime(t) : ctx->arguments[2].toNumber();
     t = TimeClip(UTC(MakeDate(MakeDay(year, month, date), TimeWithinDay(t))));
     self->value.setDouble(t);
     return self->value.asReturnedValue();
diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index daa58d5e81..5bde6b8e46 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -248,7 +248,7 @@ ExecutionEngine::ExecutionEngine(QQmlJS::EvalISelFactory *factory)
     //
     // set up the global object
     //
-    globalObject = newObject();
+    globalObject = newObject()->getPointer();
     rootContext->global = globalObject;
     rootContext->thisObject = Value::fromObject(globalObject);
 
@@ -350,25 +350,25 @@ FunctionObject *ExecutionEngine::newBuiltinFunction(ExecutionContext *scope, Str
     return f;
 }
 
-BoundFunction *ExecutionEngine::newBoundFunction(ExecutionContext *scope, FunctionObject *target, Value boundThis, const QVector<Value> &boundArgs)
+Returned<BoundFunction> *ExecutionEngine::newBoundFunction(ExecutionContext *scope, FunctionObject *target, Value boundThis, const QVector<Value> &boundArgs)
 {
     assert(target);
 
     BoundFunction *f = new (memoryManager) BoundFunction(scope, target, boundThis, boundArgs);
-    return f;
+    return f->asReturned<BoundFunction>();
 }
 
 
-Object *ExecutionEngine::newObject()
+Returned<Object> *ExecutionEngine::newObject()
 {
     Object *object = new (memoryManager) Object(this);
-    return object;
+    return object->asReturned<Object>();
 }
 
-Object *ExecutionEngine::newObject(InternalClass *internalClass)
+Returned<Object> *ExecutionEngine::newObject(InternalClass *internalClass)
 {
     Object *object = new (memoryManager) Object(internalClass);
-    return object;
+    return object->asReturned<Object>();
 }
 
 String *ExecutionEngine::newString(const QString &s)
diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index 297f756033..d00ef0ea35 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -262,10 +262,10 @@ struct Q_QML_EXPORT ExecutionEngine
     ExecutionContext *popContext();
 
     FunctionObject *newBuiltinFunction(ExecutionContext *scope, String *name, ReturnedValue (*code)(SimpleCallContext *));
-    BoundFunction *newBoundFunction(ExecutionContext *scope, FunctionObject *target, Value boundThis, const QVector<Value> &boundArgs);
+    Returned<BoundFunction> *newBoundFunction(ExecutionContext *scope, FunctionObject *target, Value boundThis, const QVector<Value> &boundArgs);
 
-    Object *newObject();
-    Object *newObject(InternalClass *internalClass);
+    Returned<Object> *newObject();
+    Returned<Object> *newObject(InternalClass *internalClass);
 
     String *newString(const QString &s);
     String *newIdentifier(const QString &text);
diff --git a/src/qml/jsruntime/qv4errorobject_p.h b/src/qml/jsruntime/qv4errorobject_p.h
index 73d9362a6d..fb526e9b1e 100644
--- a/src/qml/jsruntime/qv4errorobject_p.h
+++ b/src/qml/jsruntime/qv4errorobject_p.h
@@ -77,6 +77,11 @@ struct ErrorObject: Object {
     static void destroy(Managed *that) { static_cast<ErrorObject *>(that)->~ErrorObject(); }
 };
 
+template<>
+inline ErrorObject *value_cast(const Value &v) {
+    return v.asErrorObject();
+}
+
 struct EvalErrorObject: ErrorObject {
     EvalErrorObject(ExecutionEngine *engine, const Value &message);
 };
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index 0cf235475e..011ea34b7d 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -92,9 +92,10 @@ FunctionObject::FunctionObject(ExecutionContext *scope, String *name, bool creat
 #endif
 
      if (createProto) {
-         Object *proto = scope->engine->newObject(scope->engine->protoClass);
+         Scope s(scope);
+         Scoped<Object> proto(s, scope->engine->newObject(scope->engine->protoClass));
          proto->memberData[Index_ProtoConstructor].value = Value::fromObject(this);
-         memberData[Index_Prototype].value = Value::fromObject(proto);
+         memberData[Index_Prototype].value = proto.asValue();
      }
 
      if (name)
@@ -158,16 +159,16 @@ bool FunctionObject::hasInstance(Managed *that, const Value &value)
 
 ReturnedValue FunctionObject::construct(Managed *that, CallData *)
 {
-    FunctionObject *f = static_cast<FunctionObject *>(that);
-    ExecutionEngine *v4 = f->engine();
+    ExecutionEngine *v4 = that->engine();
     Scope scope(v4);
+    Scoped<FunctionObject> f(scope, that, Scoped<FunctionObject>::Cast);
 
     InternalClass *ic = v4->objectClass;
     Scoped<Object> proto(scope, f->get(v4->id_prototype));
     if (!!proto)
         ic = v4->emptyClass->changePrototype(proto.getPointer());
-    Object *obj = v4->newObject(ic);
-    return Value::fromObject(obj).asReturnedValue();
+    Scoped<Object> obj(scope, v4->newObject(ic));
+    return obj.asReturnedValue();
 }
 
 ReturnedValue FunctionObject::call(Managed *, CallData *)
@@ -298,20 +299,19 @@ ReturnedValue FunctionPrototype::method_apply(SimpleCallContext *ctx)
     if (!o)
         ctx->throwTypeError();
 
-    Value thisArg = ctx->argument(0);
-    Value arg = ctx->argument(1);
+    ScopedValue arg(scope, ctx->argument(1));
 
-    Object *arr = arg.asObject();
+    Scoped<Object> arr(scope, arg);
 
     quint32 len;
     if (!arr) {
         len = 0;
-        if (!arg.isNullOrUndefined()) {
+        if (!arg->isNullOrUndefined()) {
             ctx->throwTypeError();
             return Encode::undefined();
         }
     } else {
-        len = ArrayPrototype::getLength(ctx, arr);
+        len = ArrayPrototype::getLength(ctx, arr.getPointer());
     }
 
     ScopedCallData callData(scope, len);
@@ -329,14 +329,13 @@ ReturnedValue FunctionPrototype::method_apply(SimpleCallContext *ctx)
         }
     }
 
-    callData->thisObject = thisArg;
+    callData->thisObject = ctx->argument(0);
     return o->call(callData);
 }
 
 ReturnedValue FunctionPrototype::method_call(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
-    Value thisArg = ctx->argument(0);
 
     FunctionObject *o = ctx->thisObject.asFunctionObject();
     if (!o)
@@ -347,24 +346,23 @@ ReturnedValue FunctionPrototype::method_call(SimpleCallContext *ctx)
         std::copy(ctx->arguments + 1,
                   ctx->arguments + ctx->argumentCount, callData->args);
     }
-    callData->thisObject = thisArg;
+    callData->thisObject = ctx->argument(0);
     return o->call(callData);
 }
 
 ReturnedValue FunctionPrototype::method_bind(SimpleCallContext *ctx)
 {
-    FunctionObject *target = ctx->thisObject.asFunctionObject();
+    Scope scope(ctx);
+    Scoped<FunctionObject> target(scope, ctx->thisObject);
     if (!target)
         ctx->throwTypeError();
 
-    Value boundThis = ctx->argument(0);
+    ScopedValue boundThis(scope, ctx->argument(0));
     QVector<Value> boundArgs;
     for (uint i = 1; i < ctx->argumentCount; ++i)
-        boundArgs += ctx->argument(i);
+        boundArgs += ctx->arguments[i];
 
-
-    BoundFunction *f = ctx->engine->newBoundFunction(ctx->engine->rootContext, target, boundThis, boundArgs);
-    return Value::fromObject(f).asReturnedValue();
+    return ctx->engine->newBoundFunction(ctx->engine->rootContext, target.getPointer(), boundThis, boundArgs)->asReturnedValue();
 }
 
 
@@ -411,19 +409,19 @@ ScriptFunction::ScriptFunction(ExecutionContext *scope, Function *function)
 
 ReturnedValue ScriptFunction::construct(Managed *that, CallData *callData)
 {
-    ScriptFunction *f = static_cast<ScriptFunction *>(that);
-    ExecutionEngine *v4 = f->engine();
+    ExecutionEngine *v4 = that->engine();
     Scope scope(v4);
+    Scoped<ScriptFunction> f(scope, static_cast<ScriptFunction *>(that));
 
     InternalClass *ic = v4->objectClass;
     Value proto = f->memberData[Index_Prototype].value;
     if (proto.isObject())
         ic = v4->emptyClass->changePrototype(proto.objectValue());
-    Object *obj = v4->newObject(ic);
+    Scoped<Object> obj(scope, v4->newObject(ic));
 
     ExecutionContext *context = v4->current;
-    callData->thisObject = Value::fromObject(obj);
-    ExecutionContext *ctx = context->newCallContext(f, callData);
+    callData->thisObject = obj.asValue();
+    ExecutionContext *ctx = context->newCallContext(f.getPointer(), callData);
 
     ScopedValue result(scope);
     SAVE_JS_STACK(f->scope);
@@ -438,7 +436,7 @@ ReturnedValue ScriptFunction::construct(Managed *that, CallData *callData)
 
     if (result->isObject())
         return result.asReturnedValue();
-    return Value::fromObject(obj).asReturnedValue();
+    return obj.asReturnedValue();
 }
 
 ReturnedValue ScriptFunction::call(Managed *that, CallData *callData)
@@ -507,35 +505,32 @@ SimpleScriptFunction::SimpleScriptFunction(ExecutionContext *scope, Function *fu
 
 ReturnedValue SimpleScriptFunction::construct(Managed *that, CallData *callData)
 {
-    SimpleScriptFunction *f = static_cast<SimpleScriptFunction *>(that);
-    ExecutionEngine *v4 = f->engine();
+    ExecutionEngine *v4 = that->engine();
     Scope scope(v4);
+    Scoped<SimpleScriptFunction> f(scope, static_cast<SimpleScriptFunction *>(that));
 
     InternalClass *ic = v4->objectClass;
-    Value proto = f->memberData[Index_Prototype].value;
-    if (proto.isObject())
-        ic = v4->emptyClass->changePrototype(proto.objectValue());
-    Object *obj = v4->newObject(ic);
+    Scoped<Object> proto(scope, f->memberData[Index_Prototype].value);
+    if (!!proto)
+        ic = v4->emptyClass->changePrototype(proto.getPointer());
+    Scoped<Object> obj(scope, v4->newObject(ic));
 
     ExecutionContext *context = v4->current;
     void *stackSpace = alloca(requiredMemoryForExecutionContectSimple(f));
-    callData->thisObject = Value::fromObject(obj);
-    ExecutionContext *ctx = context->newCallContext(stackSpace, f, callData);
+    callData->thisObject = obj;
+    ExecutionContext *ctx = context->newCallContext(stackSpace, f.getPointer(), callData);
 
-    ScopedValue result(scope);
-    SAVE_JS_STACK(f->scope);
     try {
-        result = f->function->code(ctx, f->function->codeData);
+        Scoped<Object> result(scope, f->function->code(ctx, f->function->codeData));
+        ctx->engine->popContext();
+
+        if (!result)
+            return obj.asReturnedValue();
+        return result.asReturnedValue();
     } catch (Exception &ex) {
         ex.partiallyUnwindContext(context);
         throw;
     }
-    CHECK_JS_STACK(f->scope);
-    ctx->engine->popContext();
-
-    if (result->isObject())
-        return result.asReturnedValue();
-    return Value::fromObject(obj).asReturnedValue();
 }
 
 ReturnedValue SimpleScriptFunction::call(Managed *that, CallData *callData)
@@ -598,7 +593,7 @@ ReturnedValue BuiltinFunction::call(Managed *that, CallData *callData)
     ctx.strictMode = f->scope->strictMode; // ### needed? scope or parent context?
     ctx.thisObject = callData->thisObject;
     // ### const_cast
-    ctx.arguments = const_cast<Value *>(callData->args);
+    ctx.arguments = const_cast<SafeValue *>(callData->args);
     ctx.argumentCount = callData->argc;
     v4->pushContext(&ctx);
 
@@ -626,7 +621,7 @@ ReturnedValue IndexedBuiltinFunction::call(Managed *that, CallData *callData)
     ctx.strictMode = f->scope->strictMode; // ### needed? scope or parent context?
     ctx.thisObject = callData->thisObject;
     // ### const_cast
-    ctx.arguments = const_cast<Value *>(callData->args);
+    ctx.arguments = const_cast<SafeValue *>(callData->args);
     ctx.argumentCount = callData->argc;
     v4->pushContext(&ctx);
 
diff --git a/src/qml/jsruntime/qv4functionobject_p.h b/src/qml/jsruntime/qv4functionobject_p.h
index 333b95ad74..a0f4cf9463 100644
--- a/src/qml/jsruntime/qv4functionobject_p.h
+++ b/src/qml/jsruntime/qv4functionobject_p.h
@@ -142,6 +142,11 @@ protected:
     { static_cast<FunctionObject*>(that)->~FunctionObject(); }
 };
 
+template<>
+inline FunctionObject *value_cast(const Value &v) {
+    return v.asFunctionObject();
+}
+
 struct FunctionCtor: FunctionObject
 {
     Q_MANAGED
diff --git a/src/qml/jsruntime/qv4global_p.h b/src/qml/jsruntime/qv4global_p.h
index 096187d91f..389468cc39 100644
--- a/src/qml/jsruntime/qv4global_p.h
+++ b/src/qml/jsruntime/qv4global_p.h
@@ -105,6 +105,11 @@ struct QObjectWrapper;
 // will return it in a register on all platforms.
 // It will be returned in rax on x64, [eax,edx] on x86 and [r0,r1] on arm
 typedef quint64 ReturnedValue;
+template<typename T> struct Scoped;
+template<typename T> struct Returned;
+struct CallData;
+struct ScopedValue;
+struct ValueRef;
 
 namespace Global {
     enum {
diff --git a/src/qml/jsruntime/qv4globalobject.cpp b/src/qml/jsruntime/qv4globalobject.cpp
index e0cbee11ca..9ec70f59be 100644
--- a/src/qml/jsruntime/qv4globalobject.cpp
+++ b/src/qml/jsruntime/qv4globalobject.cpp
@@ -444,7 +444,7 @@ ReturnedValue EvalFunction::call(Managed *that, CallData *callData)
 {
     // indirect call
     // ### const_cast
-    return static_cast<EvalFunction *>(that)->evalCall(callData->thisObject, const_cast<Value *>(callData->args), callData->argc, false);
+    return static_cast<EvalFunction *>(that)->evalCall(callData->thisObject, const_cast<Value *>(static_cast<const Value *>(callData->args)), callData->argc, false);
 }
 
 
@@ -465,14 +465,15 @@ static inline int toInt(const QChar &qc, int R)
 }
 
 // parseInt [15.1.2.2]
-ReturnedValue GlobalFunctions::method_parseInt(SimpleCallContext *context)
+ReturnedValue GlobalFunctions::method_parseInt(SimpleCallContext *ctx)
 {
-    Value string = context->argument(0);
-    Value radix = context->argument(1);
-    int R = radix.isUndefined() ? 0 : radix.toInt32();
+    Scope scope(ctx);
+    ScopedValue string(scope, ctx->argument(0));
+    ScopedValue radix(scope, ctx->argument(1));
+    int R = radix->isUndefined() ? 0 : radix->toInt32();
 
     // [15.1.2.2] step by step:
-    String *inputString = string.toString(context); // 1
+    String *inputString = string->toString(ctx); // 1
     QString trimmed = inputString->toQString().trimmed(); // 2
     const QChar *pos = trimmed.constData();
     const QChar *end = pos + trimmed.length();
@@ -544,12 +545,12 @@ ReturnedValue GlobalFunctions::method_parseInt(SimpleCallContext *context)
 }
 
 // parseFloat [15.1.2.3]
-ReturnedValue GlobalFunctions::method_parseFloat(SimpleCallContext *context)
+ReturnedValue GlobalFunctions::method_parseFloat(SimpleCallContext *ctx)
 {
-    Value string = context->argument(0);
+    Scope scope(ctx);
 
     // [15.1.2.3] step by step:
-    String *inputString = string.toString(context); // 1
+    Scoped<String> inputString(scope, ctx->argument(0), Scoped<String>::Convert);
     QString trimmed = inputString->toQString().trimmed(); // 2
 
     // 4:
@@ -570,24 +571,30 @@ ReturnedValue GlobalFunctions::method_parseFloat(SimpleCallContext *context)
 }
 
 /// isNaN [15.1.2.4]
-ReturnedValue GlobalFunctions::method_isNaN(SimpleCallContext *context)
+ReturnedValue GlobalFunctions::method_isNaN(SimpleCallContext *ctx)
 {
-    const Value &v = context->argument(0);
-    if (v.integerCompatible())
+    if (!ctx->argumentCount)
+        // undefined gets converted to NaN
+        return Encode(true);
+
+    if (ctx->arguments[0].integerCompatible())
         return Encode(false);
 
-    double d = v.toNumber();
+    double d = ctx->arguments[0].toNumber();
     return Encode((bool)std::isnan(d));
 }
 
 /// isFinite [15.1.2.5]
-ReturnedValue GlobalFunctions::method_isFinite(SimpleCallContext *context)
+ReturnedValue GlobalFunctions::method_isFinite(SimpleCallContext *ctx)
 {
-    const Value &v = context->argument(0);
-    if (v.integerCompatible())
+    if (!ctx->argumentCount)
+        // undefined gets converted to NaN
+        return Encode(false);
+
+    if (ctx->arguments[0].integerCompatible())
         return Encode(true);
 
-    double d = v.toNumber();
+    double d = ctx->arguments[0].toNumber();
     return Encode((bool)std::isfinite(d));
 }
 
@@ -656,7 +663,7 @@ ReturnedValue GlobalFunctions::method_escape(SimpleCallContext *context)
     if (!context->argumentCount)
         return Value::fromString(context, QStringLiteral("undefined")).asReturnedValue();
 
-    QString str = context->argument(0).toString(context)->toQString();
+    QString str = context->arguments[0].toString(context)->toQString();
     return Value::fromString(context, escape(str)).asReturnedValue();
 }
 
@@ -665,6 +672,6 @@ ReturnedValue GlobalFunctions::method_unescape(SimpleCallContext *context)
     if (!context->argumentCount)
         return Value::fromString(context, QStringLiteral("undefined")).asReturnedValue();
 
-    QString str = context->argument(0).toString(context)->toQString();
+    QString str = context->arguments[0].toString(context)->toQString();
     return Value::fromString(context, unescape(str)).asReturnedValue();
 }
diff --git a/src/qml/jsruntime/qv4globalobject_p.h b/src/qml/jsruntime/qv4globalobject_p.h
index 90b3395baa..f49c8ebbb8 100644
--- a/src/qml/jsruntime/qv4globalobject_p.h
+++ b/src/qml/jsruntime/qv4globalobject_p.h
@@ -64,7 +64,7 @@ struct GlobalFunctions
     static ReturnedValue method_parseInt(SimpleCallContext *context);
     static ReturnedValue method_parseFloat(SimpleCallContext *context);
     static ReturnedValue method_isNaN(SimpleCallContext *context);
-    static ReturnedValue method_isFinite(SimpleCallContext *context);
+    static ReturnedValue method_isFinite(SimpleCallContext *ctx);
     static ReturnedValue method_decodeURI(SimpleCallContext *context);
     static ReturnedValue method_decodeURIComponent(SimpleCallContext *context);
     static ReturnedValue method_encodeURI(SimpleCallContext *context);
diff --git a/src/qml/jsruntime/qv4include.cpp b/src/qml/jsruntime/qv4include.cpp
index 740bb406f3..4d9573b990 100644
--- a/src/qml/jsruntime/qv4include.cpp
+++ b/src/qml/jsruntime/qv4include.cpp
@@ -84,9 +84,10 @@ QV4Include::~QV4Include()
 
 QV4::ReturnedValue QV4Include::resultValue(QV4::ExecutionEngine *v4, Status status)
 {
+    QV4::Scope scope(v4);
 
     // XXX It seems inefficient to create this object from scratch each time.
-    QV4::Object *o = v4->newObject();
+    QV4::Scoped<QV4::Object> o(scope, v4->newObject());
     o->put(v4->newString("OK"), QV4::Value::fromInt32(Ok));
     o->put(v4->newString("LOADING"), QV4::Value::fromInt32(Loading));
     o->put(v4->newString("NETWORK_ERROR"), QV4::Value::fromInt32(NetworkError));
@@ -94,7 +95,7 @@ QV4::ReturnedValue QV4Include::resultValue(QV4::ExecutionEngine *v4, Status stat
 
     o->put(v4->newString("status"), QV4::Value::fromInt32(status));
 
-    return QV4::Value::fromObject(o).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 void QV4Include::callback(const QV4::Value &callback, const QV4::Value &status)
diff --git a/src/qml/jsruntime/qv4jsonobject.cpp b/src/qml/jsruntime/qv4jsonobject.cpp
index 2bb755b537..aa6b261928 100644
--- a/src/qml/jsruntime/qv4jsonobject.cpp
+++ b/src/qml/jsruntime/qv4jsonobject.cpp
@@ -713,13 +713,12 @@ QString Stringify::Str(const QString &key, Value value)
     }
 
     if (replacerFunction) {
-        Object *holder = ctx->engine->newObject();
-        Value holderValue = Value::fromObject(holder);
+        Scoped<Object> holder(scope, ctx->engine->newObject());
         holder->put(ctx, QString(), value);
         ScopedCallData callData(scope, 2);
         callData->args[0] = Value::fromString(ctx, key);
         callData->args[1] = value;
-        callData->thisObject = holderValue;
+        callData->thisObject = holder;
         value = Value::fromReturnedValue(replacerFunction->call(callData));
     }
 
@@ -878,12 +877,14 @@ JsonObject::JsonObject(ExecutionContext *context)
 
 ReturnedValue JsonObject::method_parse(SimpleCallContext *ctx)
 {
-    QString jtext = ctx->argument(0).toString(ctx)->toQString();
+    Scope scope(ctx);
+    ScopedValue v(scope, ctx->argument(0));
+    QString jtext = v->toString(ctx)->toQString();
 
     DEBUG << "parsing source = " << jtext;
     JsonParser parser(ctx, jtext.constData(), jtext.length());
     QJsonParseError error;
-    Value result = parser.parse(&error);
+    ScopedValue result(scope, parser.parse(&error));
     if (error.error != QJsonParseError::NoError) {
         DEBUG << "parse error" << error.errorString();
         ctx->throwSyntaxError("JSON.parse: Parse error");
@@ -898,7 +899,7 @@ ReturnedValue JsonObject::method_stringify(SimpleCallContext *ctx)
 
     Stringify stringify(ctx);
 
-    Object *o = ctx->argument(1).asObject();
+    Scoped<Object> o(scope, ctx->argument(1));
     if (o) {
         stringify.replacerFunction = o->asFunctionObject();
         if (o->isArrayObject()) {
@@ -917,20 +918,21 @@ ReturnedValue JsonObject::method_stringify(SimpleCallContext *ctx)
         }
     }
 
-    Value s = ctx->argument(2);
-    if (NumberObject *n = s.asNumberObject())
+    ScopedValue s(scope, ctx->argument(2));
+    if (NumberObject *n = s->asNumberObject())
         s = n->value;
-    else if (StringObject *so = s.asStringObject())
+    else if (StringObject *so = s->asStringObject())
         s = so->value;
 
-    if (s.isNumber()) {
-        stringify.gap = QString(qMin(10, (int)s.toInteger()), ' ');
-    } else if (s.isString()) {
-        stringify.gap = s.stringValue()->toQString().left(10);
+    if (s->isNumber()) {
+        stringify.gap = QString(qMin(10, (int)s->toInteger()), ' ');
+    } else if (s->isString()) {
+        stringify.gap = s->stringValue()->toQString().left(10);
     }
 
 
-    QString result = stringify.Str(QString(), ctx->argument(0));
+    ScopedValue arg0(scope, ctx->argument(0));
+    QString result = stringify.Str(QString(), arg0);
     if (result.isEmpty())
         return Encode::undefined();
     return Value::fromString(ctx, result).asReturnedValue();
@@ -978,7 +980,7 @@ QJsonValue JsonObject::toJsonValue(const QV4::Value &value,
 QV4::ReturnedValue JsonObject::fromJsonObject(ExecutionEngine *engine, const QJsonObject &object)
 {
     Scope scope(engine);
-    Scoped<Object> o(scope, Value::fromObject(engine->newObject()));
+    Scoped<Object> o(scope, engine->newObject());
     for (QJsonObject::const_iterator it = object.begin(); it != object.end(); ++it)
         o->put(engine->newString(it.key()), Value::fromReturnedValue(fromJsonValue(engine, it.value())));
     return o.asReturnedValue();
diff --git a/src/qml/jsruntime/qv4managed_p.h b/src/qml/jsruntime/qv4managed_p.h
index f13f699748..4c1675ef88 100644
--- a/src/qml/jsruntime/qv4managed_p.h
+++ b/src/qml/jsruntime/qv4managed_p.h
@@ -89,21 +89,6 @@ struct GCDeletable
     bool lastCall;
 };
 
-struct CallData
-{
-    // below is to be compatible with Value. Initialize tag to 0
-#if Q_BYTE_ORDER != Q_LITTLE_ENDIAN
-    uint tag;
-#endif
-    int argc;
-#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
-    uint tag;
-#endif
-
-    Value thisObject;
-    Value args[1];
-};
-
 struct ManagedVTable
 {
     ReturnedValue (*call)(Managed *, CallData *data);
@@ -245,14 +230,8 @@ public:
         return vtbl == &T::static_vtbl ? static_cast<const T *>(this) : 0;
     }
 
-    template<typename T>
-    static T *cast(const Value &v) {
-        return v.as<T>();
-    }
-    static Managed *cast(const Value &v) {
-        return v.asManaged();
-    }
-
+    String *asString() { return type == Type_String ? reinterpret_cast<String *>(this) : 0; }
+    Object *asObject() { return type != Type_String ? reinterpret_cast<Object *>(this) : 0; }
     ArrayObject *asArrayObject() { return type == Type_ArrayObject ? reinterpret_cast<ArrayObject *>(this) : 0; }
     FunctionObject *asFunctionObject() { return type == Type_FunctionObject ? reinterpret_cast<FunctionObject *>(this) : 0; }
     BooleanObject *asBooleanObject() { return type == Type_BooleanObject ? reinterpret_cast<BooleanObject *>(this) : 0; }
@@ -353,6 +332,34 @@ private:
     friend struct ObjectIterator;
 };
 
+template<>
+inline Managed *value_cast(const Value &v) {
+    return v.asManaged();
+}
+
+template<typename T>
+inline T *managed_cast(Managed *m)
+{
+    return m->as<T>();
+}
+
+template<>
+inline String *managed_cast(Managed *m)
+{
+    return m->asString();
+}
+template<>
+inline Object *managed_cast(Managed *m)
+{
+    return m->asObject();
+}
+template<>
+inline FunctionObject *managed_cast(Managed *m)
+{
+    return m->asFunctionObject();
+}
+
+
 inline ReturnedValue Managed::construct(CallData *d) {
     return vtbl->construct(this, d);
 }
diff --git a/src/qml/jsruntime/qv4mm.cpp b/src/qml/jsruntime/qv4mm.cpp
index 2d53fa3fe5..a7e485a2a2 100644
--- a/src/qml/jsruntime/qv4mm.cpp
+++ b/src/qml/jsruntime/qv4mm.cpp
@@ -340,7 +340,7 @@ std::size_t MemoryManager::sweep(bool lastSweep)
         }
         if (Managed *m = weak->value.asManaged()) {
             if (!m->markBit) {
-                weak->value = Value::emptyValue();
+                weak->value = Value::undefinedValue();
                 PersistentValuePrivate *n = weak->next;
                 weak->removeFromList();
                 weak = n;
diff --git a/src/qml/jsruntime/qv4numberobject.cpp b/src/qml/jsruntime/qv4numberobject.cpp
index 3702428553..b9b64cf534 100644
--- a/src/qml/jsruntime/qv4numberobject.cpp
+++ b/src/qml/jsruntime/qv4numberobject.cpp
@@ -110,9 +110,8 @@ ReturnedValue NumberPrototype::method_toString(SimpleCallContext *ctx)
 {
     double num = thisNumberValue(ctx).asDouble();
 
-    Value arg = ctx->argument(0);
-    if (!arg.isUndefined()) {
-        int radix = arg.toInt32();
+    if (ctx->argumentCount && !ctx->arguments[0].isUndefined()) {
+        int radix = ctx->arguments[0].toInt32();
         if (radix < 2 || radix > 36) {
             ctx->throwError(QString::fromLatin1("Number.prototype.toString: %0 is not a valid radix")
                             .arg(radix));
@@ -180,7 +179,7 @@ ReturnedValue NumberPrototype::method_toFixed(SimpleCallContext *ctx)
     double fdigits = 0;
 
     if (ctx->argumentCount > 0)
-        fdigits = ctx->argument(0).toInteger();
+        fdigits = ctx->arguments[0].toInteger();
 
     if (std::isnan(fdigits))
         fdigits = 0;
@@ -204,11 +203,10 @@ ReturnedValue NumberPrototype::method_toExponential(SimpleCallContext *ctx)
 {
     double d = thisNumberValue(ctx).asDouble();
 
-    Value fraction = ctx->argument(0);
     int fdigits = -1;
 
-    if (!fraction.isUndefined()) {
-        int fdigits = ctx->argument(0).toInt32();
+    if (ctx->argumentCount && !ctx->arguments[0].isUndefined()) {
+        int fdigits = ctx->arguments[0].toInt32();
         if (fdigits < 0 || fdigits > 20) {
             String *error = ctx->engine->newString(QStringLiteral("Number.prototype.toExponential: fractionDigits out of range"));
             ctx->throwRangeError(Value::fromString(error));
@@ -229,11 +227,10 @@ ReturnedValue NumberPrototype::method_toPrecision(SimpleCallContext *ctx)
 
     ScopedValue v(scope, thisNumberValue(ctx));
 
-    Value prec = ctx->argument(0);
-    if (prec.isUndefined())
+    if (!ctx->argumentCount || ctx->arguments[0].isUndefined())
         return __qmljs_to_string(v, ctx);
 
-    double precision = prec.toInt32();
+    double precision = ctx->arguments[0].toInt32();
     if (precision < 1 || precision > 21) {
         String *error = ctx->engine->newString(QStringLiteral("Number.prototype.toPrecision: precision out of range"));
         ctx->throwRangeError(Value::fromString(error));
diff --git a/src/qml/jsruntime/qv4object_p.h b/src/qml/jsruntime/qv4object_p.h
index 7cb3fe45c2..83c7d864ff 100644
--- a/src/qml/jsruntime/qv4object_p.h
+++ b/src/qml/jsruntime/qv4object_p.h
@@ -178,10 +178,6 @@ struct Q_QML_EXPORT Object: Managed {
 
     inline ExecutionEngine *engine() const { return internalClass->engine; }
 
-    static Object *cast(const Value &v) {
-        return v.asObject();
-    }
-
     // Array handling
 
     uint allocArrayValue() {
@@ -464,6 +460,17 @@ inline void Object::arraySet(uint index, const Property *pd)
     *arrayInsert(index) = *pd;
 }
 
+template<>
+inline Object *value_cast(const Value &v) {
+    return v.asObject();
+}
+
+template<>
+inline ReturnedValue value_convert<Object>(ExecutionContext *ctx, const Value &v)
+{
+    return v.toObject(ctx)->asReturnedValue();
+}
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsruntime/qv4objectproto.cpp b/src/qml/jsruntime/qv4objectproto.cpp
index 073d588e56..82215e4fc5 100644
--- a/src/qml/jsruntime/qv4objectproto.cpp
+++ b/src/qml/jsruntime/qv4objectproto.cpp
@@ -85,11 +85,11 @@ ReturnedValue ObjectCtor::construct(Managed *that, CallData *callData)
     Scope scope(v4);
     ObjectCtor *ctor = static_cast<ObjectCtor *>(that);
     if (!callData->argc || callData->args[0].isUndefined() || callData->args[0].isNull()) {
-        Object *obj = v4->newObject();
+        Scoped<Object> obj(scope, v4->newObject());
         Scoped<Object> proto(scope, ctor->get(v4->id_prototype));
         if (!!proto)
             obj->setPrototype(proto.getPointer());
-        return Value::fromObject(obj).asReturnedValue();
+        return obj.asReturnedValue();
     }
     return Value::fromReturnedValue(__qmljs_to_object(v4->current, ValueRef(&callData->args[0]))).asReturnedValue();
 }
@@ -97,7 +97,7 @@ ReturnedValue ObjectCtor::construct(Managed *that, CallData *callData)
 ReturnedValue ObjectCtor::call(Managed *m, CallData *callData)
 {
     if (!callData->argc || callData->args[0].isUndefined() || callData->args[0].isNull())
-        return Value::fromObject(m->engine()->newObject()).asReturnedValue();
+        return m->engine()->newObject()->asReturnedValue();
     return __qmljs_to_object(m->engine()->current, ValueRef(&callData->args[0]));
 }
 
@@ -137,23 +137,26 @@ void ObjectPrototype::init(ExecutionContext *ctx, const Value &ctor)
 
 ReturnedValue ObjectPrototype::method_getPrototypeOf(SimpleCallContext *ctx)
 {
-    Value o = ctx->argument(0);
-    if (! o.isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *p = o.objectValue()->prototype();
-    return p ? Value::fromObject(p).asReturnedValue() : Encode::null();
+    Scoped<Object> p(scope, o->prototype());
+    return !!p ? p->asReturnedValue() : Encode::null();
 }
 
 ReturnedValue ObjectPrototype::method_getOwnPropertyDescriptor(SimpleCallContext *ctx)
 {
-    Value O = ctx->argument(0);
-    if (!O.isObject())
+    Scope scope(ctx);
+    Scoped<Object> O(scope, ctx->argument(0));
+    if (!O)
         ctx->throwTypeError();
 
-    String *name = ctx->argument(1).toString(ctx);
+    ScopedValue v(scope, ctx->argument(1));
+    Scoped<String> name(scope, v->toString(ctx));
     PropertyAttributes attrs;
-    Property *desc = O.objectValue()->__getOwnProperty__(name, &attrs);
+    Property *desc = O->__getOwnProperty__(name.getPointer(), &attrs);
     return fromPropertyDescriptor(ctx, desc, attrs);
 }
 
@@ -169,36 +172,37 @@ ReturnedValue ObjectPrototype::method_getOwnPropertyNames(SimpleCallContext *con
 
 ReturnedValue ObjectPrototype::method_create(SimpleCallContext *ctx)
 {
-    Value O = ctx->argument(0);
-    if (!O.isObject() && !O.isNull())
+    Scope scope(ctx);
+    ScopedValue O(scope, ctx->argument(0));
+    if (!O->isObject() && !O->isNull())
         ctx->throwTypeError();
 
-    Object *newObject = ctx->engine->newObject();
-    newObject->setPrototype(O.asObject());
+    Scoped<Object> newObject(scope, ctx->engine->newObject());
+    newObject->setPrototype(O->asObject());
 
-    Value objValue = Value::fromObject(newObject);
-    if (ctx->argumentCount > 1 && !ctx->argument(1).isUndefined()) {
-        ctx->arguments[0] = objValue;
-        method_defineProperties(ctx);
+    if (ctx->argumentCount > 1 && !ctx->arguments[1].isUndefined()) {
+        ctx->arguments[0] = newObject.asValue();
+        return method_defineProperties(ctx);
     }
 
-    return objValue.asReturnedValue();
+    return newObject.asReturnedValue();
 }
 
 ReturnedValue ObjectPrototype::method_defineProperty(SimpleCallContext *ctx)
 {
-    Value O = ctx->argument(0);
-    if (!O.isObject())
+    Scope scope(ctx);
+    Scoped<Object> O(scope, ctx->argument(0));
+    if (!O)
         ctx->throwTypeError();
 
-    String *name = ctx->argument(1).toString(ctx);
+    Scoped<String> name(scope, ctx->argument(1), Scoped<String>::Convert);
 
-    Value attributes = ctx->argument(2);
+    ScopedValue attributes(scope, ctx->argument(2));
     Property pd;
     PropertyAttributes attrs;
     toPropertyDescriptor(ctx, attributes, &pd, &attrs);
 
-    if (!O.objectValue()->__defineOwnProperty__(ctx, name, pd, attrs))
+    if (!O->__defineOwnProperty__(ctx, name.getPointer(), pd, attrs))
         ctx->throwTypeError();
 
     return O.asReturnedValue();
@@ -206,13 +210,14 @@ ReturnedValue ObjectPrototype::method_defineProperty(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_defineProperties(SimpleCallContext *ctx)
 {
-    Value O = ctx->argument(0);
-    if (!O.isObject())
+    Scope scope(ctx);
+    Scoped<Object> O(scope, ctx->argument(0));
+    if (!O)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(1).toObject(ctx);
+    Scoped<Object> o(scope, ctx->argument(1), Scoped<Object>::Convert);
 
-    ObjectIterator it(o, ObjectIterator::EnumerableOnly);
+    ObjectIterator it(o.getPointer(), ObjectIterator::EnumerableOnly);
     while (1) {
         uint index;
         String *name;
@@ -225,9 +230,9 @@ ReturnedValue ObjectPrototype::method_defineProperties(SimpleCallContext *ctx)
         toPropertyDescriptor(ctx, Value::fromReturnedValue(o->getValue(pd, attrs)), &n, &nattrs);
         bool ok;
         if (name)
-            ok = O.objectValue()->__defineOwnProperty__(ctx, name, n, nattrs);
+            ok = O->__defineOwnProperty__(ctx, name, n, nattrs);
         else
-            ok = O.objectValue()->__defineOwnProperty__(ctx, index, n, nattrs);
+            ok = O->__defineOwnProperty__(ctx, index, n, nattrs);
         if (!ok)
             ctx->throwTypeError();
     }
@@ -237,10 +242,11 @@ ReturnedValue ObjectPrototype::method_defineProperties(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_seal(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(0).objectValue();
     o->extensible = false;
 
     o->internalClass = o->internalClass->sealed();
@@ -251,15 +257,16 @@ ReturnedValue ObjectPrototype::method_seal(SimpleCallContext *ctx)
             o->arrayAttributes[i].setConfigurable(false);
     }
 
-    return ctx->argument(0).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 ReturnedValue ObjectPrototype::method_freeze(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(0).objectValue();
     o->extensible = false;
 
     o->internalClass = o->internalClass->frozen();
@@ -271,25 +278,27 @@ ReturnedValue ObjectPrototype::method_freeze(SimpleCallContext *ctx)
         if (o->arrayAttributes[i].isData())
             o->arrayAttributes[i].setWritable(false);
     }
-    return ctx->argument(0).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 ReturnedValue ObjectPrototype::method_preventExtensions(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(0).objectValue();
     o->extensible = false;
-    return ctx->argument(0).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 ReturnedValue ObjectPrototype::method_isSealed(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(0).objectValue();
     if (o->extensible)
         return Encode(false);
 
@@ -313,10 +322,11 @@ ReturnedValue ObjectPrototype::method_isSealed(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_isFrozen(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(0).objectValue();
     if (o->extensible)
         return Encode(false);
 
@@ -340,24 +350,24 @@ ReturnedValue ObjectPrototype::method_isFrozen(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_isExtensible(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
         ctx->throwTypeError();
 
-    Object *o = ctx->argument(0).objectValue();
     return Encode((bool)o->extensible);
 }
 
 ReturnedValue ObjectPrototype::method_keys(SimpleCallContext *ctx)
 {
-    if (!ctx->argument(0).isObject())
-        ctx->throwTypeError();
-
     Scope scope(ctx);
-    Object *o = ctx->argument(0).objectValue();
+    Scoped<Object> o(scope, ctx->argument(0));
+    if (!o)
+        ctx->throwTypeError();
 
     Scoped<ArrayObject> a(scope, ctx->engine->newArrayObject());
 
-    ObjectIterator it(o, ObjectIterator::EnumerableOnly);
+    ObjectIterator it(o.getPointer(), ObjectIterator::EnumerableOnly);
     ScopedValue name(scope);
     while (1) {
         name = it.nextPropertyNameAsString();
@@ -401,24 +411,26 @@ ReturnedValue ObjectPrototype::method_valueOf(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_hasOwnProperty(SimpleCallContext *ctx)
 {
-    String *P = ctx->argument(0).toString(ctx);
-    Object *O = ctx->thisObject.toObject(ctx);
-    bool r = O->__getOwnProperty__(P) != 0;
+    Scope scope(ctx);
+    Scoped<String> P(scope, ctx->argument(0), Scoped<String>::Convert);
+    Scoped<Object> O(scope, ctx->thisObject, Scoped<Object>::Convert);
+    bool r = O->__getOwnProperty__(P.getPointer()) != 0;
     if (!r)
-        r = !O->query(P).isEmpty();
+        r = !O->query(P.getPointer()).isEmpty();
     return Encode(r);
 }
 
 ReturnedValue ObjectPrototype::method_isPrototypeOf(SimpleCallContext *ctx)
 {
-    Value V = ctx->argument(0);
-    if (! V.isObject())
+    Scope scope(ctx);
+    Scoped<Object> V(scope, ctx->argument(0));
+    if (!V)
         return Encode(false);
 
-    Object *O = ctx->thisObject.toObject(ctx);
-    Object *proto = V.objectValue()->prototype();
+    Scoped<Object> O(scope, ctx->thisObject, Scoped<Object>::Convert);
+    Scoped<Object> proto(scope, V->prototype());
     while (proto) {
-        if (O == proto)
+        if (O.getPointer() == proto.getPointer())
             return Encode(true);
         proto = proto->prototype();
     }
@@ -427,11 +439,12 @@ ReturnedValue ObjectPrototype::method_isPrototypeOf(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_propertyIsEnumerable(SimpleCallContext *ctx)
 {
-    String *p = ctx->argument(0).toString(ctx);
+    Scope scope(ctx);
+    Scoped<String> p(scope, ctx->argument(0), Scoped<String>::Convert);
 
-    Object *o = ctx->thisObject.toObject(ctx);
+    Scoped<Object> o(scope, ctx->thisObject, Scoped<Object>::Convert);
     PropertyAttributes attrs;
-    o->__getOwnProperty__(p, &attrs);
+    o->__getOwnProperty__(p.getPointer(), &attrs);
     return Encode(attrs.isEnumerable());
 }
 
@@ -439,21 +452,23 @@ ReturnedValue ObjectPrototype::method_defineGetter(SimpleCallContext *ctx)
 {
     if (ctx->argumentCount < 2)
         ctx->throwTypeError();
-    String *prop = ctx->argument(0).toString(ctx);
 
-    FunctionObject *f = ctx->argument(1).asFunctionObject();
+    Scope scope(ctx);
+    Scoped<String> prop(scope, ctx->argument(0), Scoped<String>::Convert);
+
+    Scoped<FunctionObject> f(scope, ctx->argument(1));
     if (!f)
         ctx->throwTypeError();
 
-    Object *o = ctx->thisObject.asObject();
+    Scoped<Object> o(scope, ctx->thisObject);
     if (!o) {
         if (!ctx->thisObject.isUndefined())
             return Encode::undefined();
         o = ctx->engine->globalObject;
     }
 
-    Property pd = Property::fromAccessor(f, 0);
-    o->__defineOwnProperty__(ctx, prop, pd, Attr_Accessor);
+    Property pd = Property::fromAccessor(f.getPointer(), 0);
+    o->__defineOwnProperty__(ctx, prop.getPointer(), pd, Attr_Accessor);
     return Encode::undefined();
 }
 
@@ -461,21 +476,23 @@ ReturnedValue ObjectPrototype::method_defineSetter(SimpleCallContext *ctx)
 {
     if (ctx->argumentCount < 2)
         ctx->throwTypeError();
-    String *prop = ctx->argument(0).toString(ctx);
 
-    FunctionObject *f = ctx->argument(1).asFunctionObject();
+    Scope scope(ctx);
+    Scoped<String> prop(scope, ctx->argument(0), Scoped<String>::Convert);
+
+    Scoped<FunctionObject> f(scope, ctx->argument(1));
     if (!f)
         ctx->throwTypeError();
 
-    Object *o = ctx->thisObject.asObject();
+    Scoped<Object> o(scope, ctx->thisObject);
     if (!o) {
         if (!ctx->thisObject.isUndefined())
             return Encode::undefined();
         o = ctx->engine->globalObject;
     }
 
-    Property pd = Property::fromAccessor(0, f);
-    o->__defineOwnProperty__(ctx, prop, pd, Attr_Accessor);
+    Property pd = Property::fromAccessor(0, f.getPointer());
+    o->__defineOwnProperty__(ctx, prop.getPointer(), pd, Attr_Accessor);
     return Encode::undefined();
 }
 
@@ -490,20 +507,23 @@ ReturnedValue ObjectPrototype::method_get_proto(SimpleCallContext *ctx)
 
 ReturnedValue ObjectPrototype::method_set_proto(SimpleCallContext *ctx)
 {
-    Object *o = ctx->thisObject.asObject();
-    if (!o)
+    Scope scope(ctx);
+    Scoped<Object> o(scope, ctx->thisObject);
+    if (!o || !ctx->argumentCount)
         ctx->throwTypeError();
 
-    Value proto = ctx->argument(0);
-    bool ok = false;
-    if (proto.isNull()) {
+    if (ctx->arguments[0].isNull()) {
         o->setPrototype(0);
-        ok = true;
-    } else if (Object *p = proto.asObject()) {
-        if (o->prototype() == p) {
+        return Encode::undefined();
+    }
+
+    Scoped<Object> p(scope, ctx->arguments[0]);
+    bool ok = false;
+    if (!!p) {
+        if (o->prototype() == p.getPointer()) {
             ok = true;
         } else if (o->extensible) {
-            ok = o->setPrototype(p);
+            ok = o->setPrototype(p.getPointer());
         }
     }
     if (!ok)
@@ -532,6 +552,7 @@ void ObjectPrototype::toPropertyDescriptor(ExecutionContext *ctx, Value v, Prope
     if (o->__hasProperty__(ctx->engine->id_get)) {
         ScopedValue get(scope, o->get(ctx->engine->id_get));
         FunctionObject *f = get->asFunctionObject();
+        qDebug() << "get" << (void *)get.asReturnedValue() << f;
         if (f) {
             desc->setGetter(f);
         } else if (get->isUndefined()) {
@@ -581,8 +602,9 @@ ReturnedValue ObjectPrototype::fromPropertyDescriptor(ExecutionContext *ctx, con
         return Encode::undefined();
 
     ExecutionEngine *engine = ctx->engine;
+    Scope scope(engine);
 //    Let obj be the result of creating a new object as if by the expression new Object() where Object is the standard built-in constructor with that name.
-    Object *o = engine->newObject();
+    Scoped<Object> o(scope, engine->newObject());
 
     Property pd;
     if (attrs.isData()) {
@@ -601,7 +623,7 @@ ReturnedValue ObjectPrototype::fromPropertyDescriptor(ExecutionContext *ctx, con
     pd.value = Value::fromBoolean(attrs.isConfigurable());
     o->__defineOwnProperty__(ctx, engine->newString(QStringLiteral("configurable")), pd, Attr_Data);
 
-    return Value::fromObject(o).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 
diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 2bd201e2a1..446ea9df3a 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -1196,8 +1196,9 @@ void __qmljs_builtin_define_getter_setter(ExecutionContext *ctx, const ValueRef
 
 ReturnedValue __qmljs_builtin_define_object_literal(QV4::ExecutionContext *ctx, const QV4::Value *args, int classId)
 {
+    Scope scope(ctx);
     QV4::InternalClass *klass = ctx->compilationUnit->runtimeClasses[classId];
-    Object *o = ctx->engine->newObject(klass);
+    Scoped<Object> o(scope, ctx->engine->newObject(klass));
 
     for (int i = 0; i < klass->size; ++i) {
         if (klass->propertyData[i].isData())
@@ -1210,7 +1211,7 @@ ReturnedValue __qmljs_builtin_define_object_literal(QV4::ExecutionContext *ctx,
         }
     }
 
-    return Value::fromObject(o).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 QV4::ReturnedValue __qmljs_builtin_setup_arguments_object(ExecutionContext *ctx)
diff --git a/src/qml/jsruntime/qv4scopedvalue_p.h b/src/qml/jsruntime/qv4scopedvalue_p.h
index 1e05b6170c..711c79eb1d 100644
--- a/src/qml/jsruntime/qv4scopedvalue_p.h
+++ b/src/qml/jsruntime/qv4scopedvalue_p.h
@@ -51,32 +51,6 @@ QT_BEGIN_NAMESPACE
 
 namespace QV4 {
 
-struct ScopedValueArray {
-    ScopedValueArray(ExecutionEngine *e, int size)
-        : engine(e)
-#ifndef QT_NO_DEBUG
-        , size(size)
-#endif
-    {
-        ptr = e->stackPush(size);
-    }
-
-    ~ScopedValueArray() {
-#ifndef QT_NO_DEBUG
-        engine->stackPop(size);
-        Q_ASSERT(engine->jsStackTop == ptr);
-#else
-        engine->jsStackTop = ptr;
-#endif
-    }
-
-    ExecutionEngine *engine;
-#ifndef QT_NO_DEBUG
-    int size;
-#endif
-    Value *ptr;
-};
-
 struct ScopedValue;
 
 struct Scope {
@@ -189,6 +163,9 @@ struct ScopedValue
 template<typename T>
 struct Scoped
 {
+    enum _Convert { Convert };
+    enum _Cast { Cast };
+
     inline void setPointer(Managed *p) {
 #if QT_POINTER_SIZE == 8
         ptr->val = (quint64)p;
@@ -209,7 +186,24 @@ struct Scoped
     Scoped(const Scope &scope, const Value &v)
     {
         ptr = scope.engine->jsStackTop++;
-        setPointer(T::cast(v));
+        setPointer(value_cast<T>(v));
+#ifndef QT_NO_DEBUG
+        ++scope.size;
+#endif
+    }
+    Scoped(const Scope &scope, const ScopedValue &v)
+    {
+        ptr = scope.engine->jsStackTop++;
+        setPointer(value_cast<T>(*v.ptr));
+#ifndef QT_NO_DEBUG
+        ++scope.size;
+#endif
+    }
+
+    Scoped(const Scope &scope, const Value &v, _Convert)
+    {
+        ptr = scope.engine->jsStackTop++;
+        ptr->val = value_convert<T>(scope.engine->current, v);
 #ifndef QT_NO_DEBUG
         ++scope.size;
 #endif
@@ -226,6 +220,16 @@ struct Scoped
 #endif
     }
     template<typename X>
+    Scoped(const Scope &scope, X *t, _Cast)
+    {
+        ptr = scope.engine->jsStackTop++;
+        setPointer(managed_cast<T>(t));
+#ifndef QT_NO_DEBUG
+        ++scope.size;
+#endif
+    }
+
+    template<typename X>
     Scoped(const Scope &scope, Returned<X> *x)
     {
         ptr = scope.engine->jsStackTop++;
@@ -238,21 +242,29 @@ struct Scoped
     Scoped(const Scope &scope, const ReturnedValue &v)
     {
         ptr = scope.engine->jsStackTop++;
-        setPointer(T::cast(QV4::Value::fromReturnedValue(v)));
+        setPointer(value_cast<T>(QV4::Value::fromReturnedValue(v)));
+#ifndef QT_NO_DEBUG
+        ++scope.size;
+#endif
+    }
+    Scoped(const Scope &scope, const ReturnedValue &v, _Convert)
+    {
+        ptr = scope.engine->jsStackTop++;
+        ptr->val = value_convert<T>(scope.engine->current, QV4::Value::fromReturnedValue(v));
 #ifndef QT_NO_DEBUG
         ++scope.size;
 #endif
     }
 
     Scoped<T> &operator=(const Value &v) {
-        setPointer(T::cast(v));
+        setPointer(value_cast<T>(v));
         return *this;
     }
 
     Scoped<T> &operator=(const ValueRef &v);
 
     Scoped<T> &operator=(const ReturnedValue &v) {
-        setPointer(T::cast(QV4::Value::fromReturnedValue(v)));
+        setPointer(value_cast<T>(QV4::Value::fromReturnedValue(v)));
         return *this;
     }
 
@@ -280,7 +292,7 @@ struct Scoped
     bool operator!() const {
         return !ptr->managed();
     }
-    operator bool() const {
+    operator void *() const {
         return ptr->managed();
     }
 
@@ -307,6 +319,21 @@ struct Scoped
     Value *ptr;
 };
 
+struct CallData
+{
+    // below is to be compatible with Value. Initialize tag to 0
+#if Q_BYTE_ORDER != Q_LITTLE_ENDIAN
+    uint tag;
+#endif
+    int argc;
+#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
+    uint tag;
+#endif
+
+    SafeValue thisObject;
+    SafeValue args[1];
+};
+
 struct ScopedCallData {
     ScopedCallData(Scope &scope, int argc)
     {
@@ -388,7 +415,7 @@ template<typename T>
 inline Scoped<T>::Scoped(const Scope &scope, const ValueRef &v)
 {
     ptr = scope.engine->jsStackTop++;
-    setPointer(T::cast(*v.operator ->()));
+    setPointer(value_cast<T>(*v.operator ->()));
 #ifndef QT_NO_DEBUG
     ++scope.size;
 #endif
@@ -397,11 +424,10 @@ inline Scoped<T>::Scoped(const Scope &scope, const ValueRef &v)
 template<typename T>
 inline Scoped<T> &Scoped<T>::operator=(const ValueRef &v)
 {
-    setPointer(T::cast(*v.operator ->()));
+    setPointer(value_cast<T>(*v.operator ->()));
     return *this;
 }
 
-
 struct CallDataRef {
     CallDataRef(const ScopedCallData &c)
         : ptr(c.ptr) {}
@@ -474,6 +500,70 @@ struct Encode : private Value {
     }
 };
 
+inline SafeValue &SafeValue::operator =(const ScopedValue &v)
+{
+    val = v.ptr->val;
+    return *this;
+}
+
+template<typename T>
+inline SafeValue &SafeValue::operator=(Returned<T> *t)
+{
+    val = t->getPointer()->asReturnedValue();
+    return *this;
+}
+
+template<typename T>
+inline SafeValue &SafeValue::operator=(const Scoped<T> &t)
+{
+    val = t.ptr->val;
+    return *this;
+}
+
+template<typename T>
+inline Returned<T> *SafeValue::as()
+{
+    return Returned<T>::create(value_cast<T>(*this));
+}
+
+template<typename T>
+PersistentValue::PersistentValue(Returned<T> *obj)
+    : d(new PersistentValuePrivate(QV4::Value::fromManaged(obj->getPointer())))
+{
+}
+
+template<typename T>
+inline PersistentValue::PersistentValue(const Scoped<T> &obj)
+    : d(new PersistentValuePrivate(*obj.ptr))
+{
+}
+
+template<typename T>
+inline PersistentValue &PersistentValue::operator=(Returned<T> *obj)
+{
+    return operator=(QV4::Value::fromManaged(obj->getPointer()).asReturnedValue());
+}
+
+template<typename T>
+inline PersistentValue &PersistentValue::operator=(const Scoped<T> &obj)
+{
+    return operator=(*obj.ptr);
+}
+
+
+template<typename T>
+inline WeakValue::WeakValue(Returned<T> *obj)
+    : d(new PersistentValuePrivate(QV4::Value::fromManaged(obj->getPointer()), /*engine*/0, /*weak*/true))
+{
+}
+
+template<typename T>
+inline WeakValue &WeakValue::operator=(Returned<T> *obj)
+{
+    return operator=(QV4::Value::fromManaged(obj->getPointer()).asReturnedValue());
+}
+
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsruntime/qv4serialize.cpp b/src/qml/jsruntime/qv4serialize.cpp
index 41481ac1b8..35022acfd5 100644
--- a/src/qml/jsruntime/qv4serialize.cpp
+++ b/src/qml/jsruntime/qv4serialize.cpp
@@ -328,7 +328,7 @@ ReturnedValue Serialize::deserialize(const char *&data, QV8Engine *engine)
     case WorkerObject:
     {
         quint32 size = headersize(header);
-        QV4::Object *o = v4->newObject();
+        Scoped<Object> o(scope, v4->newObject());
         ScopedValue name(scope);
         ScopedValue value(scope);
         for (quint32 ii = 0; ii < size; ++ii) {
@@ -336,7 +336,7 @@ ReturnedValue Serialize::deserialize(const char *&data, QV8Engine *engine)
             value = deserialize(data, engine);
             o->put(name->asString(), value);
         }
-        return QV4::Value::fromObject(o).asReturnedValue();
+        return o.asReturnedValue();
     }
     case WorkerInt32:
         return QV4::Encode((qint32)popUint32(data));
diff --git a/src/qml/jsruntime/qv4string_p.h b/src/qml/jsruntime/qv4string_p.h
index 7dd912a41f..7ad428a502 100644
--- a/src/qml/jsruntime/qv4string_p.h
+++ b/src/qml/jsruntime/qv4string_p.h
@@ -120,10 +120,6 @@ struct Q_QML_EXPORT String : public Managed {
         return _text.length();
     }
 
-    static String *cast(const Value &v) {
-        return v.asString();
-    }
-
     QString _text;
     mutable Identifier *identifier;
     mutable uint stringHash;
@@ -142,6 +138,17 @@ protected:
     static bool isEqualTo(Managed *that, Managed *o);
 };
 
+template<>
+inline String *value_cast(const Value &v) {
+    return v.asString();
+}
+
+template<>
+inline ReturnedValue value_convert<String>(ExecutionContext *ctx, const Value &v)
+{
+    return v.toString(ctx)->asReturnedValue();
+}
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsruntime/qv4stringobject.cpp b/src/qml/jsruntime/qv4stringobject.cpp
index 811c5b26b9..afd6e440dc 100644
--- a/src/qml/jsruntime/qv4stringobject.cpp
+++ b/src/qml/jsruntime/qv4stringobject.cpp
@@ -472,8 +472,8 @@ ReturnedValue StringPrototype::method_replace(SimpleCallContext *ctx)
     uint *matchOffsets = _matchOffsets;
     uint nMatchOffsets = 0;
 
-    Value searchValue = ctx->argument(0);
-    RegExpObject *regExp = searchValue.as<RegExpObject>();
+    ScopedValue searchValue(scope, ctx->argument(0));
+    Scoped<RegExpObject> regExp(scope, searchValue);
     if (regExp) {
         uint offset = 0;
         while (true) {
@@ -501,7 +501,7 @@ ReturnedValue StringPrototype::method_replace(SimpleCallContext *ctx)
         numCaptures = regExp->value->captureCount();
     } else {
         numCaptures = 1;
-        QString searchString = searchValue.toString(ctx)->toQString();
+        QString searchString = searchValue->toString(ctx)->toQString();
         int idx = string.indexOf(searchString);
         if (idx != -1) {
             numStringMatches = 1;
@@ -512,9 +512,10 @@ ReturnedValue StringPrototype::method_replace(SimpleCallContext *ctx)
     }
 
     QString result;
-    Value replaceValue = ctx->argument(1);
     ScopedValue replacement(scope);
-    if (FunctionObject* searchCallback = replaceValue.asFunctionObject()) {
+    ScopedValue replaceValue(scope, ctx->argument(1));
+    Scoped<FunctionObject> searchCallback(scope, replaceValue);
+    if (!!searchCallback) {
         result.reserve(string.length() + 10*numStringMatches);
         ScopedCallData callData(scope, numCaptures + 2);
         callData->thisObject = Value::undefinedValue();
@@ -542,7 +543,7 @@ ReturnedValue StringPrototype::method_replace(SimpleCallContext *ctx)
         }
         result += string.midRef(lastEnd);
     } else {
-        QString newString = replaceValue.toString(ctx)->toQString();
+        QString newString = replaceValue->toString(ctx)->toQString();
         result.reserve(string.length() + numStringMatches*newString.size());
 
         int lastEnd = 0;
@@ -595,9 +596,9 @@ ReturnedValue StringPrototype::method_slice(SimpleCallContext *ctx)
     const QString text = getThisString(ctx);
     const double length = text.length();
 
-    double start = ctx->argument(0).toInteger();
-    double end = ctx->argument(1).isUndefined()
-            ? length : ctx->argument(1).toInteger();
+    double start = ctx->argumentCount ? ctx->arguments[0].toInteger() : 0;
+    double end = (ctx->argumentCount < 2 || ctx->arguments[1].isUndefined())
+            ? length : ctx->arguments[1].toInteger();
 
     if (start < 0)
         start = qMax(length + start, 0.);
@@ -625,32 +626,33 @@ ReturnedValue StringPrototype::method_split(SimpleCallContext *ctx)
     else
         text = ctx->thisObject.toString(ctx)->toQString();
 
-    Value separatorValue = ctx->argumentCount > 0 ? ctx->argument(0) : Value::undefinedValue();
-    Value limitValue = ctx->argumentCount > 1 ? ctx->argument(1) : Value::undefinedValue();
+    ScopedValue separatorValue(scope, ctx->argument(0));
+    ScopedValue limitValue(scope, ctx->argument(1));
 
     Scoped<ArrayObject> array(scope, ctx->engine->newArrayObject());
 
-    if (separatorValue.isUndefined()) {
-        if (limitValue.isUndefined()) {
+    if (separatorValue->isUndefined()) {
+        if (limitValue->isUndefined()) {
             array->push_back(Value::fromString(ctx, text));
             return array.asReturnedValue();
         }
-        return Value::fromString(ctx, text.left(limitValue.toInteger())).asReturnedValue();
+        return Value::fromString(ctx, text.left(limitValue->toInteger())).asReturnedValue();
     }
 
-    uint limit = limitValue.isUndefined() ? UINT_MAX : limitValue.toUInt32();
+    uint limit = limitValue->isUndefined() ? UINT_MAX : limitValue->toUInt32();
 
     if (limit == 0)
         return array.asReturnedValue();
 
-    if (RegExpObject* re = separatorValue.as<RegExpObject>()) {
+    Scoped<RegExpObject> re(scope, separatorValue);
+    if (!!re) {
         if (re->value->pattern().isEmpty()) {
-            re = 0;
+            re = (RegExpObject *)0;
             separatorValue = Value::fromString(ctx, QString());
         }
     }
 
-    if (RegExpObject* re = separatorValue.as<RegExpObject>()) {
+    if (!!re) {
         uint offset = 0;
         uint* matchOffsets = (uint*)alloca(re->value->captureCount() * 2 * sizeof(uint));
         while (true) {
@@ -675,7 +677,7 @@ ReturnedValue StringPrototype::method_split(SimpleCallContext *ctx)
         if (array->arrayLength() < limit)
             array->push_back(Value::fromString(ctx, text.mid(offset)));
     } else {
-        QString separator = separatorValue.toString(ctx)->toQString();
+        QString separator = separatorValue->toString(ctx)->toQString();
         if (separator.isEmpty()) {
             for (uint i = 0; i < qMin(limit, uint(text.length())); ++i)
                 array->push_back(Value::fromString(ctx, text.mid(i, 1)));
diff --git a/src/qml/jsruntime/qv4value.cpp b/src/qml/jsruntime/qv4value.cpp
index f97aa66669..570ba9e82e 100644
--- a/src/qml/jsruntime/qv4value.cpp
+++ b/src/qml/jsruntime/qv4value.cpp
@@ -288,6 +288,11 @@ PersistentValue::PersistentValue(const Value &val)
 {
 }
 
+PersistentValue::PersistentValue(const ScopedValue &val)
+    : d(new PersistentValuePrivate(*val.operator ->()))
+{
+}
+
 PersistentValue::PersistentValue(ReturnedValue val)
     : d(new PersistentValuePrivate(Value::fromReturnedValue(val)))
 {
@@ -326,6 +331,16 @@ PersistentValue &PersistentValue::operator =(const Value &other)
     return *this;
 }
 
+PersistentValue &PersistentValue::operator =(const ScopedValue &other)
+{
+    return operator=(*other.operator ->());
+}
+
+PersistentValue &PersistentValue::operator =(const ValueRef other)
+{
+    return operator=(*other.operator ->());
+}
+
 PersistentValue &PersistentValue::operator =(const ReturnedValue &other)
 {
     if (!d) {
@@ -354,6 +369,11 @@ WeakValue::WeakValue(const WeakValue &other)
         d->ref();
 }
 
+WeakValue::WeakValue(ReturnedValue val)
+    : d(new PersistentValuePrivate(Value::fromReturnedValue(val), /*engine*/0, /*weak*/true))
+{
+}
+
 WeakValue &WeakValue::operator=(const WeakValue &other)
 {
     if (d == other.d)
@@ -380,6 +400,16 @@ WeakValue &WeakValue::operator =(const Value &other)
     return *this;
 }
 
+WeakValue &WeakValue::operator =(const ReturnedValue &other)
+{
+    if (!d) {
+        d = new PersistentValuePrivate(Value::fromReturnedValue(other), /*engine*/0, /*weak*/true);
+        return *this;
+    }
+    d = d->detach(Value::fromReturnedValue(other), /*weak*/true);
+    return *this;
+}
+
 
 WeakValue::~WeakValue()
 {
diff --git a/src/qml/jsruntime/qv4value_def_p.h b/src/qml/jsruntime/qv4value_def_p.h
index 76f694c0e9..7d97d4531e 100644
--- a/src/qml/jsruntime/qv4value_def_p.h
+++ b/src/qml/jsruntime/qv4value_def_p.h
@@ -341,6 +341,37 @@ struct Q_QML_EXPORT Value
     inline void mark() const;
 };
 
+struct SafeValue : public Value
+{
+    SafeValue &operator =(const ScopedValue &v);
+    template<typename T>
+    SafeValue &operator=(Returned<T> *t);
+    SafeValue &operator=(ReturnedValue v) {
+        val = v;
+        return *this;
+    }
+    template<typename T>
+    SafeValue &operator=(const Scoped<T> &t);
+    SafeValue &operator=(const Value &v) {
+        val = v.val;
+        return *this;
+    }
+
+    template<typename T>
+    Returned<T> *as();
+};
+
+template<typename T>
+T *value_cast(const Value &v)
+{
+    return v.as<T>();
+}
+
+template<typename T>
+ReturnedValue value_convert(ExecutionContext *ctx, const Value &v);
+
+
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsruntime/qv4value_p.h b/src/qml/jsruntime/qv4value_p.h
index de00a2264c..6cefe13ae6 100644
--- a/src/qml/jsruntime/qv4value_p.h
+++ b/src/qml/jsruntime/qv4value_p.h
@@ -372,11 +372,22 @@ public:
     PersistentValue() : d(0) {}
 
     PersistentValue(const Value &val);
+    PersistentValue(const ScopedValue &val);
     PersistentValue(ReturnedValue val);
+    template<typename T>
+    PersistentValue(Returned<T> *obj);
+    template<typename T>
+    PersistentValue(const Scoped<T> &obj);
     PersistentValue(const PersistentValue &other);
     PersistentValue &operator=(const PersistentValue &other);
     PersistentValue &operator=(const Value &other);
+    PersistentValue &operator=(const ScopedValue &other);
+    PersistentValue &operator=(const ValueRef other);
     PersistentValue &operator =(const ReturnedValue &other);
+    template<typename T>
+    PersistentValue &operator=(Returned<T> *obj);
+    template<typename T>
+    PersistentValue &operator=(const Scoped<T> &obj);
     ~PersistentValue();
 
     Value value() const {
@@ -408,8 +419,15 @@ public:
     WeakValue() : d(0) {}
     WeakValue(const Value &val);
     WeakValue(const WeakValue &other);
+    WeakValue(ReturnedValue val);
+    template<typename T>
+    WeakValue(Returned<T> *obj);
     WeakValue &operator=(const WeakValue &other);
     WeakValue &operator=(const Value &other);
+    WeakValue &operator =(const ReturnedValue &other);
+    template<typename T>
+    WeakValue &operator=(Returned<T> *obj);
+
     ~WeakValue();
 
     Value value() const {
diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index 5ed75a1e06..149cbf2c49 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -1408,7 +1408,8 @@ void QQmlComponentPrivate::initializeObjectWithInitialProperties(const QV4::Valu
 QQmlComponentExtension::QQmlComponentExtension(QV8Engine *engine)
 {
     QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
-    QV4::Object *proto = v4->newObject();
+    QV4::Scope scope(v4);
+    QV4::Scoped<QV4::Object> proto(scope, v4->newObject());
     QV4::Property *s = proto->insertMember(v4->newString(QStringLiteral("onStatusChanged")),
                                            QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
     s->setGetter(V4FUNCTION(QmlIncubatorObject::method_get_statusChanged, v4));
@@ -1421,7 +1422,7 @@ QQmlComponentExtension::QQmlComponentExtension(QV8Engine *engine)
     s->setGetter(V4FUNCTION(QmlIncubatorObject::method_get_object, v4));
     proto->defineDefaultProperty(v4, QStringLiteral("forceCompletion"), QmlIncubatorObject::method_forceCompletion);
 
-    incubationProto = QV4::Value::fromObject(proto);
+    incubationProto = proto;
 }
 
 QV4::ReturnedValue QmlIncubatorObject::method_get_object(QV4::SimpleCallContext *ctx)
diff --git a/src/qml/qml/qqmllocale.cpp b/src/qml/qml/qqmllocale.cpp
index 405411e65c..d4998ec5ba 100644
--- a/src/qml/qml/qqmllocale.cpp
+++ b/src/qml/qml/qqmllocale.cpp
@@ -112,7 +112,7 @@ private:
 DEFINE_MANAGED_VTABLE(QQmlLocaleData);
 
 #define GET_LOCALE_DATA_RESOURCE(OBJECT) \
-    QQmlLocaleData *r = OBJECT.as<QQmlLocaleData>(); \
+    QV4::Scoped<QQmlLocaleData> r(scope, OBJECT.as<QQmlLocaleData>()); \
     if (!r) \
         V4THROW_ERROR("Not a valid Locale object")
 
@@ -140,6 +140,8 @@ QV4::ReturnedValue QQmlDateExtension::method_toLocaleString(QV4::SimpleCallConte
     if (ctx->argumentCount > 2)
         return QV4::DatePrototype::method_toLocaleString(ctx);
 
+    QV4::Scope scope(ctx);
+
     QV4::DateObject *date = ctx->thisObject.asDateObject();
     if (!date)
         return QV4::DatePrototype::method_toLocaleString(ctx);
@@ -182,6 +184,8 @@ QV4::ReturnedValue QQmlDateExtension::method_toLocaleTimeString(QV4::SimpleCallC
     if (ctx->argumentCount > 2)
         return QV4::DatePrototype::method_toLocaleTimeString(ctx);
 
+    QV4::Scope scope(ctx);
+
     QV4::DateObject *date = ctx->thisObject.asDateObject();
     if (!date)
         return QV4::DatePrototype::method_toLocaleTimeString(ctx);
@@ -225,6 +229,8 @@ QV4::ReturnedValue QQmlDateExtension::method_toLocaleDateString(QV4::SimpleCallC
     if (ctx->argumentCount > 2)
         return QV4::DatePrototype::method_toLocaleDateString(ctx);
 
+    QV4::Scope scope(ctx);
+
     QV4::DateObject *dateObj = ctx->thisObject.asDateObject();
     if (!dateObj)
         return QV4::DatePrototype::method_toLocaleDateString(ctx);
@@ -273,6 +279,8 @@ QV4::ReturnedValue QQmlDateExtension::method_fromLocaleString(QV4::SimpleCallCon
         return QV4::Encode(engine->newDateObject(dt));
     }
 
+    QV4::Scope scope(ctx);
+
     if (ctx->argumentCount < 1 || ctx->argumentCount > 3 || !isLocaleObject(ctx->arguments[0]))
         V4THROW_ERROR("Locale: Date.fromLocaleString(): Invalid arguments");
 
@@ -315,6 +323,8 @@ QV4::ReturnedValue QQmlDateExtension::method_fromLocaleTimeString(QV4::SimpleCal
     if (ctx->argumentCount < 1 || ctx->argumentCount > 3 || !isLocaleObject(ctx->arguments[0]))
         V4THROW_ERROR("Locale: Date.fromLocaleTimeString(): Invalid arguments");
 
+    QV4::Scope scope(ctx);
+
     GET_LOCALE_DATA_RESOURCE(ctx->arguments[0]);
 
     QLocale::FormatType enumFormat = QLocale::LongFormat;
@@ -355,6 +365,8 @@ QV4::ReturnedValue QQmlDateExtension::method_fromLocaleDateString(QV4::SimpleCal
     if (ctx->argumentCount < 1 || ctx->argumentCount > 3 || !isLocaleObject(ctx->arguments[0]))
         V4THROW_ERROR("Locale: Date.fromLocaleDateString(): Invalid arguments");
 
+    QV4::Scope scope(ctx);
+
     GET_LOCALE_DATA_RESOURCE(ctx->arguments[0]);
 
     QLocale::FormatType enumFormat = QLocale::LongFormat;
@@ -414,6 +426,8 @@ QV4::ReturnedValue QQmlNumberExtension::method_toLocaleString(QV4::SimpleCallCon
     if (!isLocaleObject(ctx->arguments[0]))
         return QV4::NumberPrototype::method_toLocaleString(ctx); // Use the default Number toLocaleString()
 
+    QV4::Scope scope(ctx);
+
     GET_LOCALE_DATA_RESOURCE(ctx->arguments[0]);
 
     quint16 format = 'f';
@@ -450,6 +464,8 @@ QV4::ReturnedValue QQmlNumberExtension::method_toLocaleCurrencyString(QV4::Simpl
     if (!isLocaleObject(ctx->arguments[0]))
         V4THROW_ERROR("Locale: Number.toLocaleCurrencyString(): Invalid arguments");
 
+    QV4::Scope scope(ctx);
+
     GET_LOCALE_DATA_RESOURCE(ctx->arguments[0]);
 
     QString symbol;
@@ -470,6 +486,8 @@ QV4::ReturnedValue QQmlNumberExtension::method_fromLocaleString(QV4::SimpleCallC
     int numberIdx = 0;
     QLocale locale;
 
+    QV4::Scope scope(ctx);
+
     if (ctx->argumentCount == 2) {
         if (!isLocaleObject(ctx->arguments[0]))
             V4THROW_ERROR("Locale: Number.fromLocaleString(): Invalid arguments");
@@ -671,8 +689,8 @@ public:
 QV8LocaleDataDeletable::QV8LocaleDataDeletable(QV8Engine *engine)
 {
     QV4::ExecutionEngine *eng = QV8Engine::getV4(engine);
-    QV4::Object *o = eng->newObject();
-    prototype = QV4::Value::fromObject(o);
+    QV4::Scope scope(eng);
+    QV4::Scoped<QV4::Object> o(scope, eng->newObject());
 
     o->defineDefaultProperty(eng, QStringLiteral("dateFormat"), QQmlLocaleData::method_dateFormat, 0);
     o->defineDefaultProperty(eng, QStringLiteral("standaloneDayName"), QQmlLocaleData::method_standaloneDayName, 0);
@@ -699,6 +717,8 @@ QV8LocaleDataDeletable::QV8LocaleDataDeletable(QV8Engine *engine)
     o->defineAccessorProperty(eng, QStringLiteral("amText"), QQmlLocaleData::method_get_amText, 0);
     o->defineAccessorProperty(eng, QStringLiteral("measurementSystem"), QQmlLocaleData::method_get_measurementSystem, 0);
     o->defineAccessorProperty(eng, QStringLiteral("exponential"), QQmlLocaleData::method_get_exponential, 0);
+
+    prototype = o;
 }
 
 QV8LocaleDataDeletable::~QV8LocaleDataDeletable()
diff --git a/src/qml/qml/qqmlvaluetypewrapper.cpp b/src/qml/qml/qqmlvaluetypewrapper.cpp
index f89ce15a57..b5073763b8 100644
--- a/src/qml/qml/qqmlvaluetypewrapper.cpp
+++ b/src/qml/qml/qqmlvaluetypewrapper.cpp
@@ -134,9 +134,10 @@ void QmlValueTypeWrapper::initProto(ExecutionEngine *v4)
     if (v4->qmlExtensions()->valueTypeWrapperPrototype)
         return;
 
-    Object *o = v4->newObject();
+    Scope scope(v4);
+    Scoped<Object> o(scope, v4->newObject());
     o->defineDefaultProperty(v4, QStringLiteral("toString"), method_toString, 1);
-    v4->qmlExtensions()->valueTypeWrapperPrototype = o;
+    v4->qmlExtensions()->valueTypeWrapperPrototype = o.getPointer();
 }
 
 ReturnedValue QmlValueTypeWrapper::create(QV8Engine *v8, QObject *object, int property, QQmlValueType *type)
diff --git a/src/qml/qml/qqmlxmlhttprequest.cpp b/src/qml/qml/qqmlxmlhttprequest.cpp
index dc98bd176e..bef943fd51 100644
--- a/src/qml/qml/qqmlxmlhttprequest.cpp
+++ b/src/qml/qml/qqmlxmlhttprequest.cpp
@@ -65,6 +65,7 @@
 #include <QtCore/qdebug.h>
 
 #include <private/qv4objectproto_p.h>
+#include <private/qv4scopedvalue_p.h>
 
 using namespace QV4;
 
@@ -99,15 +100,15 @@ static inline QQmlXMLHttpRequestData *xhrdata(QV8Engine *engine)
     return (QQmlXMLHttpRequestData *)engine->xmlHttpRequestData();
 }
 
-static Value constructMeObject(const Value &thisObj, QV8Engine *e)
+static ReturnedValue constructMeObject(const Value &thisObj, QV8Engine *e)
 {
     ExecutionEngine *v4 = QV8Engine::getV4(e);
     Scope scope(v4);
-    Object *meObj = v4->newObject();
+    Scoped<Object> meObj(scope, v4->newObject());
     meObj->put(v4->newString(QStringLiteral("ThisObject")), thisObj);
     ScopedValue v(scope, QmlContextWrapper::qmlScope(e, e->callingContext(), 0));
     meObj->put(v4->newString(QStringLiteral("ActivationObject")), v);
-    return Value::fromObject(meObj);
+    return meObj.asReturnedValue();
 }
 
 QQmlXMLHttpRequestData::QQmlXMLHttpRequestData()
@@ -625,10 +626,11 @@ Value Element::prototype(ExecutionEngine *engine)
 {
     QQmlXMLHttpRequestData *d = xhrdata(engine->v8Engine);
     if (d->elementPrototype.isEmpty()) {
-        Object *p = engine->newObject();
+        Scope scope(engine);
+        Scoped<Object> p(scope, engine->newObject());
         p->setPrototype(NodePrototype::getProto(engine).asObject());
         p->defineAccessorProperty(engine, QStringLiteral("tagName"), NodePrototype::method_get_nodeName, 0);
-        d->elementPrototype = Value::fromObject(p);
+        d->elementPrototype = p;
         engine->v8Engine->freezeObject(d->elementPrototype.value());
     }
     return d->elementPrototype.value();
@@ -638,12 +640,13 @@ Value Attr::prototype(ExecutionEngine *engine)
 {
     QQmlXMLHttpRequestData *d = xhrdata(engine->v8Engine);
     if (d->attrPrototype.isEmpty()) {
-        Object *p = engine->newObject();
+        Scope scope(engine);
+        Scoped<Object> p(scope, engine->newObject());
         p->setPrototype(NodePrototype::getProto(engine).asObject());
         p->defineAccessorProperty(engine, QStringLiteral("name"), method_name, 0);
         p->defineAccessorProperty(engine, QStringLiteral("value"), method_value, 0);
         p->defineAccessorProperty(engine, QStringLiteral("ownerElement"), method_ownerElement, 0);
-        d->attrPrototype = Value::fromObject(p);
+        d->attrPrototype = p;
         engine->v8Engine->freezeObject(d->attrPrototype.value());
     }
     return d->attrPrototype.value();
@@ -693,11 +696,12 @@ Value CharacterData::prototype(ExecutionEngine *v4)
 {
     QQmlXMLHttpRequestData *d = xhrdata(v4->v8Engine);
     if (d->characterDataPrototype.isEmpty()) {
-        Object *p = v4->newObject();
+        Scope scope(v4);
+        Scoped<Object> p(scope, v4->newObject());
         p->setPrototype(NodePrototype::getProto(v4).asObject());
         p->defineAccessorProperty(v4, QStringLiteral("data"), NodePrototype::method_get_nodeValue, 0);
         p->defineAccessorProperty(v4, QStringLiteral("length"), method_length, 0);
-        d->characterDataPrototype = Value::fromObject(p);
+        d->characterDataPrototype = p;
         v4->v8Engine->freezeObject(d->characterDataPrototype);
     }
     return d->characterDataPrototype.value();
@@ -725,11 +729,12 @@ Value Text::prototype(ExecutionEngine *v4)
 {
     QQmlXMLHttpRequestData *d = xhrdata(v4->v8Engine);
     if (d->textPrototype.isEmpty()) {
-        Object *p = v4->newObject();
+        Scope scope(v4);
+        Scoped<Object> p(scope, v4->newObject());
         p->setPrototype(CharacterData::prototype(v4).asObject());
         p->defineAccessorProperty(v4, QStringLiteral("isElementContentWhitespace"), method_isElementContentWhitespace, 0);
         p->defineAccessorProperty(v4, QStringLiteral("wholeText"), method_wholeText, 0);
-        d->textPrototype = Value::fromObject(p);
+        d->textPrototype = p;
         v4->v8Engine->freezeObject(d->textPrototype);
     }
     return d->textPrototype.value();
@@ -740,9 +745,10 @@ Value CDATA::prototype(ExecutionEngine *v4)
     // ### why not just use TextProto???
     QQmlXMLHttpRequestData *d = xhrdata(v4->v8Engine);
     if (d->cdataPrototype.isEmpty()) {
-        Object *p = v4->newObject();
+        Scope scope(v4);
+        Scoped<Object> p(scope, v4->newObject());
         p->setPrototype(Text::prototype(v4).asObject());
-        d->cdataPrototype = Value::fromObject(p);
+        d->cdataPrototype = p;
         v4->v8Engine->freezeObject(d->cdataPrototype);
     }
     return d->cdataPrototype.value();
@@ -752,13 +758,14 @@ Value Document::prototype(ExecutionEngine *v4)
 {
     QQmlXMLHttpRequestData *d = xhrdata(v4->v8Engine);
     if (d->documentPrototype.isEmpty()) {
-        Object *p = v4->newObject();
+        Scope scope(v4);
+        Scoped<Object> p(scope, v4->newObject());
         p->setPrototype(NodePrototype::getProto(v4).asObject());
         p->defineAccessorProperty(v4, QStringLiteral("xmlVersion"), method_xmlVersion, 0);
         p->defineAccessorProperty(v4, QStringLiteral("xmlEncoding"), method_xmlEncoding, 0);
         p->defineAccessorProperty(v4, QStringLiteral("xmlStandalone"), method_xmlStandalone, 0);
         p->defineAccessorProperty(v4, QStringLiteral("documentElement"), method_documentElement, 0);
-        d->documentPrototype = Value::fromObject(p);
+        d->documentPrototype = p;
         v4->v8Engine->freezeObject(d->documentPrototype);
     }
     return d->documentPrototype.value();
@@ -1016,9 +1023,9 @@ public:
     int replyStatus() const;
     QString replyStatusText() const;
 
-    Value open(const Value &me, const QString &, const QUrl &);
-    Value send(const Value &me, const QByteArray &);
-    Value abort(const Value &me);
+    ReturnedValue open(const ValueRef me, const QString &, const QUrl &);
+    ReturnedValue send(const ValueRef me, const QByteArray &);
+    ReturnedValue abort(const ValueRef me);
 
     void addHeader(const QString &, const QString &);
     QString header(const QString &name);
@@ -1060,11 +1067,11 @@ private:
 #endif
     void readEncoding();
 
-    Value getMe() const;
-    void setMe(const Value &me);
+    ReturnedValue getMe() const;
+    void setMe(const ValueRef me);
     PersistentValue m_me;
 
-    void dispatchCallback(const Value &me);
+    void dispatchCallback(const ValueRef me);
     void printError(const Exception &e);
 
     int m_status;
@@ -1115,8 +1122,7 @@ QString QQmlXMLHttpRequest::replyStatusText() const
     return m_statusText;
 }
 
-Value QQmlXMLHttpRequest::open(const Value &me, const QString &method,
-                                                       const QUrl &url)
+ReturnedValue QQmlXMLHttpRequest::open(const ValueRef me, const QString &method, const QUrl &url)
 {
     destroyNetwork();
     m_sendFlag = false;
@@ -1127,7 +1133,7 @@ Value QQmlXMLHttpRequest::open(const Value &me, const QString &method,
     m_state = Opened;
     m_addedHeaders.clear();
     dispatchCallback(me);
-    return Value::undefinedValue();
+    return Encode::undefined();
 }
 
 void QQmlXMLHttpRequest::addHeader(const QString &name, const QString &value)
@@ -1241,7 +1247,7 @@ void QQmlXMLHttpRequest::requestFromUrl(const QUrl &url)
                      this, SLOT(finished()));
 }
 
-Value QQmlXMLHttpRequest::send(const Value &me, const QByteArray &data)
+ReturnedValue QQmlXMLHttpRequest::send(const ValueRef me, const QByteArray &data)
 {
     m_errorFlag = false;
     m_sendFlag = true;
@@ -1252,10 +1258,10 @@ Value QQmlXMLHttpRequest::send(const Value &me, const QByteArray &data)
 
     requestFromUrl(m_url);
 
-    return Value::undefinedValue();
+    return Encode::undefined();
 }
 
-Value QQmlXMLHttpRequest::abort(const Value &me)
+ReturnedValue QQmlXMLHttpRequest::abort(const ValueRef me)
 {
     destroyNetwork();
     m_responseEntityBody = QByteArray();
@@ -1273,15 +1279,15 @@ Value QQmlXMLHttpRequest::abort(const Value &me)
 
     m_state = Unsent;
 
-    return Value::undefinedValue();
+    return Encode::undefined();
 }
 
-Value QQmlXMLHttpRequest::getMe() const
+ReturnedValue QQmlXMLHttpRequest::getMe() const
 {
-    return m_me.value();
+    return m_me.value().asReturnedValue();
 }
 
-void QQmlXMLHttpRequest::setMe(const Value &me)
+void QQmlXMLHttpRequest::setMe(const ValueRef me)
 {
     m_me = me;
 }
@@ -1293,18 +1299,22 @@ void QQmlXMLHttpRequest::readyRead()
     m_statusText =
         QString::fromUtf8(m_network->attribute(QNetworkRequest::HttpReasonPhraseAttribute).toByteArray());
 
+    Scope scope(v4);
+    ScopedValue me(scope, m_me.value());
+
     // ### We assume if this is called the headers are now available
     if (m_state < HeadersReceived) {
         m_state = HeadersReceived;
         fillHeadersList ();
-        dispatchCallback(m_me.value());
+        dispatchCallback(me);
     }
 
     bool wasEmpty = m_responseEntityBody.isEmpty();
     m_responseEntityBody.append(m_network->readAll());
     if (wasEmpty && !m_responseEntityBody.isEmpty())
         m_state = Loading;
-    dispatchCallback(m_me.value());
+
+    dispatchCallback(me);
 }
 
 static const char *errorToString(QNetworkReply::NetworkError error)
@@ -1335,6 +1345,9 @@ void QQmlXMLHttpRequest::error(QNetworkReply::NetworkError error)
         qWarning().nospace() << "    " << error << ' ' << errorToString(error) << ' ' << m_statusText;
     }
 
+    Scope scope(v4);
+    ScopedValue me(scope, m_me.value());
+
     if (error == QNetworkReply::ContentAccessDenied ||
         error == QNetworkReply::ContentOperationNotPermittedError ||
         error == QNetworkReply::ContentNotFoundError ||
@@ -1342,7 +1355,7 @@ void QQmlXMLHttpRequest::error(QNetworkReply::NetworkError error)
         error == QNetworkReply::ContentReSendError ||
         error == QNetworkReply::UnknownContentError) {
         m_state = Loading;
-        dispatchCallback(m_me.value());
+        dispatchCallback(me);
     } else {
         m_errorFlag = true;
         m_responseEntityBody = QByteArray();
@@ -1350,7 +1363,7 @@ void QQmlXMLHttpRequest::error(QNetworkReply::NetworkError error)
 
     m_state = Done;
 
-    dispatchCallback(m_me.value());
+    dispatchCallback(me);
 }
 
 #define XMLHTTPREQUEST_MAXIMUM_REDIRECT_RECURSION 15
@@ -1405,7 +1418,9 @@ void QQmlXMLHttpRequest::finished()
 
     dispatchCallback(m_me);
 
-    setMe(Value::emptyValue());
+    Scope scope(v4);
+    ScopedValue v(scope, Value::emptyValue());
+    setMe(v);
 }
 
 
@@ -1483,12 +1498,12 @@ const QByteArray &QQmlXMLHttpRequest::rawResponseBody() const
     return m_responseEntityBody;
 }
 
-void QQmlXMLHttpRequest::dispatchCallback(const Value &me)
+void QQmlXMLHttpRequest::dispatchCallback(const ValueRef me)
 {
     ExecutionContext *ctx = v4->current;
     QV4::Scope scope(v4);
     try {
-        Object *o = me.asObject();
+        Scoped<Object> o(scope, me);
         if (!o)
             ctx->throwError(QStringLiteral("QQmlXMLHttpRequest: internal error: empty ThisObject"));
 
@@ -1631,7 +1646,9 @@ DEFINE_MANAGED_VTABLE(QQmlXMLHttpRequestCtor);
 void QQmlXMLHttpRequestCtor::setupProto()
 {
     ExecutionEngine *v4 = engine();
-    proto = v4->newObject();
+    Scope scope(v4);
+    Scoped<Object> p(scope, v4->newObject());
+    proto = p.getPointer();
 
     // Methods
     proto->defineDefaultProperty(v4, QStringLiteral("open"), method_open);
@@ -1704,7 +1721,8 @@ ReturnedValue QQmlXMLHttpRequestCtor::method_open(SimpleCallContext *ctx)
     if (!username.isNull()) url.setUserName(username);
     if (!password.isNull()) url.setPassword(password);
 
-    return r->open(constructMeObject(ctx->thisObject, engine), method, url).asReturnedValue();
+    ScopedValue meObject(scope, constructMeObject(ctx->thisObject, engine));
+    return r->open(meObject, method, url);
 }
 
 ReturnedValue QQmlXMLHttpRequestCtor::method_setRequestHeader(SimpleCallContext *ctx)
@@ -1774,7 +1792,8 @@ ReturnedValue QQmlXMLHttpRequestCtor::method_send(SimpleCallContext *ctx)
     if (ctx->argumentCount > 0)
         data = ctx->arguments[0].toQStringNoThrow().toUtf8();
 
-    return r->send(constructMeObject(ctx->thisObject, engine), data).asReturnedValue();
+    ScopedValue meObject(scope, constructMeObject(ctx->thisObject, engine));
+    return r->send(meObject, data);
 }
 
 ReturnedValue QQmlXMLHttpRequestCtor::method_abort(SimpleCallContext *ctx)
@@ -1786,7 +1805,8 @@ ReturnedValue QQmlXMLHttpRequestCtor::method_abort(SimpleCallContext *ctx)
         V4THROW_REFERENCE("Not an XMLHttpRequest object");
     QQmlXMLHttpRequest *r = w->request;
 
-    return r->abort(constructMeObject(ctx->thisObject, ctx->engine->v8Engine)).asReturnedValue();
+    ScopedValue meObject(scope, constructMeObject(ctx->thisObject, ctx->engine->v8Engine));
+    return r->abort(meObject);
 }
 
 ReturnedValue QQmlXMLHttpRequestCtor::method_getResponseHeader(SimpleCallContext *ctx)
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
index 6389ad2715..40b5075ddd 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
@@ -962,12 +962,12 @@ ReturnedValue QtObject::method_createQmlObject(SimpleCallContext *ctx)
             for (int ii = 0; ii < errors.count(); ++ii) {
                 const QQmlError &error = errors.at(ii);
                 errorstr += QLatin1String("\n    ") + error.toString();
-                QV4::Object *qmlerror = v4->newObject();
+                QV4::Scoped<QV4::Object> qmlerror(scope, v4->newObject());
                 qmlerror->put(v4->newString("lineNumber"), QV4::Value::fromInt32(error.line()));
                 qmlerror->put(v4->newString("columnNumber"), QV4::Value::fromInt32(error.column()));
                 qmlerror->put(v4->newString("fileName"), Value::fromString(v4->newString(error.url().toString())));
                 qmlerror->put(v4->newString("message"), Value::fromString(v4->newString(error.description())));
-                qmlerrors->putIndexed(ii, QV4::Value::fromObject(qmlerror));
+                qmlerrors->putIndexed(ii, qmlerror.asValue());
             }
 
             Scoped<Object> errorObject(scope, v4->newErrorObject(Value::fromString(v4->newString(errorstr))));
@@ -1001,7 +1001,8 @@ ReturnedValue QtObject::method_createQmlObject(SimpleCallContext *ctx)
         url = context->resolvedUrl(url);
 
     QObject *parentArg = 0;
-    if (QV4::QObjectWrapper *qobjectWrapper = ctx->arguments[1].as<QV4::QObjectWrapper>())
+    QV4::Scoped<QV4::QObjectWrapper> qobjectWrapper(scope, ctx->arguments[1]);
+    if (!!qobjectWrapper)
         parentArg = qobjectWrapper->object();
     if (!parentArg)
         V4THROW_ERROR("Qt.createQmlObject(): Missing parent object");
diff --git a/src/qml/qml/v8/qv4domerrors.cpp b/src/qml/qml/v8/qv4domerrors.cpp
index 63c79f85c2..f89831fa2f 100644
--- a/src/qml/qml/v8/qv4domerrors.cpp
+++ b/src/qml/qml/v8/qv4domerrors.cpp
@@ -48,7 +48,8 @@ using namespace QV4;
 
 void qt_add_domexceptions(ExecutionEngine *e)
 {
-    Object *domexception = e->newObject();
+    Scope scope(e);
+    Scoped<Object> domexception(scope, e->newObject());
     domexception->defineReadonlyProperty(e, QStringLiteral("INDEX_SIZE_ERR"), Value::fromInt32(DOMEXCEPTION_INDEX_SIZE_ERR));
     domexception->defineReadonlyProperty(e, QStringLiteral("DOMSTRING_SIZE_ERR"), Value::fromInt32(DOMEXCEPTION_DOMSTRING_SIZE_ERR));
     domexception->defineReadonlyProperty(e, QStringLiteral("HIERARCHY_REQUEST_ERR"), Value::fromInt32(DOMEXCEPTION_HIERARCHY_REQUEST_ERR));
@@ -66,7 +67,7 @@ void qt_add_domexceptions(ExecutionEngine *e)
     domexception->defineReadonlyProperty(e, QStringLiteral("INVALID_ACCESS_ERR"), Value::fromInt32(DOMEXCEPTION_INVALID_ACCESS_ERR));
     domexception->defineReadonlyProperty(e, QStringLiteral("VALIDATION_ERR"), Value::fromInt32(DOMEXCEPTION_VALIDATION_ERR));
     domexception->defineReadonlyProperty(e, QStringLiteral("TYPE_MISMATCH_ERR"), Value::fromInt32(DOMEXCEPTION_TYPE_MISMATCH_ERR));
-    e->globalObject->defineDefaultProperty(e->current, QStringLiteral("DOMException"), Value::fromObject(domexception));
+    e->globalObject->defineDefaultProperty(e->current, QStringLiteral("DOMException"), domexception.asValue());
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/v8/qv4sqlerrors.cpp b/src/qml/qml/v8/qv4sqlerrors.cpp
index bd5a9fdc83..a203fd9980 100644
--- a/src/qml/qml/v8/qv4sqlerrors.cpp
+++ b/src/qml/qml/v8/qv4sqlerrors.cpp
@@ -49,7 +49,8 @@ using namespace QV4;
 
 void qt_add_sqlexceptions(QV4::ExecutionEngine *engine)
 {
-    Object *sqlexception = engine->newObject();
+    Scope scope(engine);
+    Scoped<Object> sqlexception(scope, engine->newObject());
     sqlexception->defineReadonlyProperty(engine, QStringLiteral("UNKNOWN_ERR"), Value::fromInt32(SQLEXCEPTION_UNKNOWN_ERR));
     sqlexception->defineReadonlyProperty(engine, QStringLiteral("DATABASE_ERR"), Value::fromInt32(SQLEXCEPTION_DATABASE_ERR));
     sqlexception->defineReadonlyProperty(engine, QStringLiteral("VERSION_ERR"), Value::fromInt32(SQLEXCEPTION_VERSION_ERR));
@@ -58,7 +59,7 @@ void qt_add_sqlexceptions(QV4::ExecutionEngine *engine)
     sqlexception->defineReadonlyProperty(engine, QStringLiteral("SYNTAX_ERR"), Value::fromInt32(SQLEXCEPTION_SYNTAX_ERR));
     sqlexception->defineReadonlyProperty(engine, QStringLiteral("CONSTRAINT_ERR"), Value::fromInt32(SQLEXCEPTION_CONSTRAINT_ERR));
     sqlexception->defineReadonlyProperty(engine, QStringLiteral("TIMEOUT_ERR"), Value::fromInt32(SQLEXCEPTION_TIMEOUT_ERR));
-    engine->globalObject->defineDefaultProperty(engine->current, QStringLiteral("SQLException"), Value::fromObject(sqlexception));
+    engine->globalObject->defineDefaultProperty(engine->current, QStringLiteral("SQLException"), sqlexception.asValue());
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/v8/qv8engine.cpp b/src/qml/qml/v8/qv8engine.cpp
index 08bbd4c960..b62d8c173d 100644
--- a/src/qml/qml/v8/qv8engine.cpp
+++ b/src/qml/qml/v8/qv8engine.cpp
@@ -212,10 +212,11 @@ static QV4::ReturnedValue arrayFromVariantList(QV8Engine *engine, const QVariant
 static QV4::ReturnedValue objectFromVariantMap(QV8Engine *engine, const QVariantMap &map)
 {
     QV4::ExecutionEngine *e = QV8Engine::getV4(engine);
-    QV4::Object *o = e->newObject();
+    QV4::Scope scope(e);
+    QV4::Scoped<QV4::Object> o(scope, e->newObject());
     for (QVariantMap::ConstIterator iter = map.begin(); iter != map.end(); ++iter)
         o->put(e->newString(iter.key()), QV4::Value::fromReturnedValue(engine->fromVariant(iter.value())));
-    return QV4::Value::fromObject(o).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 Q_CORE_EXPORT QString qt_regexp_toCanonical(const QString &, QRegExp::PatternSyntax);
@@ -566,13 +567,14 @@ QVariantList QV8Engine::variantListFromJS(QV4::ArrayObject *a,
 // the QVariantMap converted to JS, recursively.
 QV4::ReturnedValue QV8Engine::variantMapToJS(const QVariantMap &vmap)
 {
-    QV4::Object *o = m_v4Engine->newObject();
+    QV4::Scope scope(m_v4Engine);
+    QV4::Scoped<QV4::Object> o(scope, m_v4Engine->newObject());
     QVariantMap::const_iterator it;
     for (it = vmap.constBegin(); it != vmap.constEnd(); ++it) {
         QV4::Property *p = o->insertMember(m_v4Engine->newIdentifier(it.key()), QV4::Attr_Data);
         p->value = QV4::Value::fromReturnedValue(variantToJS(it.value()));
     }
-    return QV4::Value::fromObject(o).asReturnedValue();
+    return o.asReturnedValue();
 }
 
 // Converts a JS Object to a QVariantMap.
diff --git a/src/qml/types/qqmldelegatemodel.cpp b/src/qml/types/qqmldelegatemodel.cpp
index 0457adb348..b9f78da96e 100644
--- a/src/qml/types/qqmldelegatemodel.cpp
+++ b/src/qml/types/qqmldelegatemodel.cpp
@@ -83,10 +83,12 @@ struct DelegateModelGroupFunction: QV4::FunctionObject
 
     static QV4::ReturnedValue call(QV4::Managed *that, QV4::CallData *callData)
     {
-        DelegateModelGroupFunction *f = static_cast<DelegateModelGroupFunction *>(that);
-        QQmlDelegateModelItemObject *o = callData->thisObject.as<QQmlDelegateModelItemObject>();
+        QV4::ExecutionEngine *v4 = that->engine();
+        QV4::Scope scope(v4);
+        QV4::Scoped<DelegateModelGroupFunction> f(scope, that, QV4::Scoped<DelegateModelGroupFunction>::Cast);
+        QV4::Scoped<QQmlDelegateModelItemObject> o(scope, callData->thisObject);
         if (!o)
-            that->engine()->current->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+            v4->current->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
         QV4::Value v = callData->argc ? callData->args[0] : QV4::Value::undefinedValue();
         return f->code(o->item, f->flag, v);
@@ -1622,8 +1624,9 @@ void QQmlDelegateModelItemMetaType::initializePrototype()
 {
     QQmlDelegateModelEngineData *data = engineData(v8Engine);
     QV4::ExecutionEngine *v4 = QV8Engine::getV4(v8Engine);
+    QV4::Scope scope(v4);
 
-    QV4::Object *proto = v4->newObject();
+    QV4::Scoped<QV4::Object> proto(scope, v4->newObject());
     proto->defineAccessorProperty(v4, QStringLiteral("model"), QQmlDelegateModelItem::get_model, 0);
     proto->defineAccessorProperty(v4, QStringLiteral("groups"), QQmlDelegateModelItem::get_groups, QQmlDelegateModelItem::set_groups);
     QV4::Property *p = proto->insertMember(v4->newString(QStringLiteral("isUnresolved")),
@@ -1656,7 +1659,7 @@ void QQmlDelegateModelItemMetaType::initializePrototype()
         p = proto->insertMember(v4->newString(propertyName), QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
         p->setGetter(new (v4->memoryManager) DelegateModelGroupFunction(v4->rootContext, i + 1, QQmlDelegateModelItem::get_index));
     }
-    modelItemProto = QV4::Value::fromObject(proto);
+    modelItemProto = proto;
 }
 
 int QQmlDelegateModelItemMetaType::parseGroups(const QStringList &groups) const
@@ -3233,15 +3236,16 @@ private:
 QQmlDelegateModelEngineData::QQmlDelegateModelEngineData(QV8Engine *e)
 {
     QV4::ExecutionEngine *v4 = QV8Engine::getV4(e);
+    QV4::Scope scope(v4);
 
-    QV4::Object *proto = v4->newObject();
+    QV4::Scoped<QV4::Object> proto(scope, v4->newObject());
     QV4::Property *p = proto->insertMember(v4->newString(QStringLiteral("index")), QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
     p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, QQmlDelegateModelGroupChange::method_get_index));
     p = proto->insertMember(v4->newString(QStringLiteral("count")), QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
     p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, QQmlDelegateModelGroupChange::method_get_count));
     p = proto->insertMember(v4->newString(QStringLiteral("moveId")), QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
     p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, QQmlDelegateModelGroupChange::method_get_moveId));
-    changeProto = QV4::Value::fromObject(proto);
+    changeProto = proto;
 }
 
 QQmlDelegateModelEngineData::~QQmlDelegateModelEngineData()
diff --git a/src/qml/types/qquickworkerscript.cpp b/src/qml/types/qquickworkerscript.cpp
index 4e39682d84..d80df760fa 100644
--- a/src/qml/types/qquickworkerscript.cpp
+++ b/src/qml/types/qquickworkerscript.cpp
@@ -177,7 +177,7 @@ public:
     };
 
     QHash<int, WorkerScript *> workers;
-    QV4::Value getWorker(WorkerScript *);
+    QV4::ReturnedValue getWorker(WorkerScript *);
 
     int m_nextId;
 
@@ -282,9 +282,9 @@ QV4::ReturnedValue QQuickWorkerScriptEnginePrivate::method_sendMessage(QV4::Simp
 {
     WorkerEngine *engine = (WorkerEngine*)ctx->engine->v8Engine;
 
-    int id = ctx->argument(1).toInt32();
+    int id = ctx->argumentCount > 1 ? ctx->arguments[1].toInt32() : 0;
 
-    QByteArray data = QV4::Serialize::serialize(ctx->argument(2), engine);
+    QByteArray data = QV4::Serialize::serialize(ctx->argumentCount > 2 ? ctx->arguments[2] : QV4::Value::undefinedValue(), engine);
 
     QMutexLocker locker(&engine->p->m_lock);
     WorkerScript *script = engine->p->workers.value(id);
@@ -298,27 +298,29 @@ QV4::ReturnedValue QQuickWorkerScriptEnginePrivate::method_sendMessage(QV4::Simp
 }
 
 // Requires handle scope and context scope
-QV4::Value QQuickWorkerScriptEnginePrivate::getWorker(WorkerScript *script)
+QV4::ReturnedValue QQuickWorkerScriptEnginePrivate::getWorker(WorkerScript *script)
 {
     if (!script->initialized) {
         script->initialized = true;
 
         QV4::ExecutionEngine *v4 = QV8Engine::getV4(workerEngine);
+        QV4::Scope scope(v4);
 
         script->object = QV4::QmlContextWrapper::urlScope(workerEngine, script->source);
 
-        QV4::QmlContextWrapper *w = script->object.value().asObject()->as<QV4::QmlContextWrapper>();
+        QV4::Scoped<QV4::QmlContextWrapper> w(scope, script->object.value());
+        Q_ASSERT(!!w);
         w->setReadOnly(false);
 
-        QV4::Object *api = v4->newObject();
+        QV4::Scoped<QV4::Object> api(scope, v4->newObject());
         api->put(v4->newString("sendMessage"), workerEngine->sendFunction(script->id));
 
-        script->object.value().asObject()->put(v4->newString("WorkerScript"), QV4::Value::fromObject(api));
+        script->object.value().asObject()->put(v4->newString("WorkerScript"), api.asValue());
 
         w->setReadOnly(true);
     }
 
-    return script->object.value();
+    return script->object.value().asReturnedValue();
 }
 
 bool QQuickWorkerScriptEnginePrivate::event(QEvent *event)
@@ -386,12 +388,15 @@ void QQuickWorkerScriptEnginePrivate::processLoad(int id, const QUrl &url)
         if (!script)
             return;
         script->source = url;
-        QV4::Value activation = getWorker(script);
-        if (activation.isEmpty())
-            return;
 
         QV4::ExecutionEngine *v4 = QV8Engine::getV4(workerEngine);
-        QV4::Script program(v4, activation.asObject(), sourceCode, url.toString());
+        QV4::Scope scope(v4);
+
+        QV4::Scoped<QV4::Object> activation(scope, getWorker(script));
+        if (!activation)
+            return;
+
+        QV4::Script program(v4, activation.getPointer(), sourceCode, url.toString());
 
         QV4::ExecutionContext *ctx = v4->current;
         try {
diff --git a/src/qml/util/qqmladaptormodel.cpp b/src/qml/util/qqmladaptormodel.cpp
index 9812e2a4a6..add422b8da 100644
--- a/src/qml/util/qqmladaptormodel.cpp
+++ b/src/qml/util/qqmladaptormodel.cpp
@@ -213,7 +213,8 @@ public:
     void initializeConstructor(QQmlAdaptorModelEngineData *const data)
     {
         QV4::ExecutionEngine *v4 = data->v4;
-        QV4::Object *proto = v4->newObject();
+        QV4::Scope scope(v4);
+        QV4::Scoped<QV4::Object> proto(scope, v4->newObject());
         QV4::Property *p = proto->insertMember(v4->newString(QStringLiteral("index")),
                                                QV4::Attr_Accessor|QV4::Attr_NotEnumerable|QV4::Attr_NotConfigurable);
         p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, get_index));
@@ -232,7 +233,7 @@ public:
             p->setGetter(new (v4->memoryManager) QV4::IndexedBuiltinFunction(v4->rootContext, propertyId, QQmlDMCachedModelData::get_property));
             p->setSetter(new (v4->memoryManager) QV4::IndexedBuiltinFunction(v4->rootContext, propertyId, QQmlDMCachedModelData::set_property));
         }
-        prototype = QV4::Value::fromObject(proto);
+        prototype = proto.asValue();
     }
 
     // QAbstractDynamicMetaObject
@@ -955,7 +956,8 @@ void QQmlAdaptorModel::objectDestroyed(QObject *)
 QQmlAdaptorModelEngineData::QQmlAdaptorModelEngineData(QV8Engine *e)
     : v4(QV8Engine::getV4(e))
 {
-    QV4::Object *proto = v4->newObject();
+    QV4::Scope scope(v4);
+    QV4::Scoped<QV4::Object> proto(scope, v4->newObject());
     QV4::Property *p = proto->insertMember(v4->newString(QStringLiteral("index")),
                                            QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
     p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, get_index));
@@ -963,7 +965,7 @@ QQmlAdaptorModelEngineData::QQmlAdaptorModelEngineData(QV8Engine *e)
                             QV4::Attr_Accessor|QV4::Attr_NotConfigurable|QV4::Attr_NotEnumerable);
     p->setGetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, QQmlDMListAccessorData::get_modelData));
     p->setSetter(v4->newBuiltinFunction(v4->rootContext, v4->id_undefined, QQmlDMListAccessorData::set_modelData));
-    listItemProto = QV4::Value::fromObject(proto);
+    listItemProto = proto;
 }
 
 QQmlAdaptorModelEngineData::~QQmlAdaptorModelEngineData()
diff --git a/src/quick/items/context2d/qquickcontext2d.cpp b/src/quick/items/context2d/qquickcontext2d.cpp
index 3a84404d66..82fbbd0862 100644
--- a/src/quick/items/context2d/qquickcontext2d.cpp
+++ b/src/quick/items/context2d/qquickcontext2d.cpp
@@ -941,6 +941,8 @@ static QV4::Value qt_create_image_data(qreal w, qreal h, QV8Engine* engine, cons
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_get_canvas(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -955,6 +957,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_get_canvas(QV4::SimpleCall
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_restore(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -968,6 +972,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_restore(QV4::SimpleCallCon
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_reset(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1008,6 +1014,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_reset(QV4::SimpleCallConte
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_save(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1036,6 +1044,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_save(QV4::SimpleCallContex
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_rotate(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1063,6 +1073,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_rotate(QV4::SimpleCallCont
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_scale(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1107,6 +1119,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_scale(QV4::SimpleCallConte
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_setTransform(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1135,6 +1149,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_setTransform(QV4::SimpleCa
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_transform(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1181,6 +1197,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_translate(QV4::SimpleCallC
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_resetTransform(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1198,6 +1216,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_resetTransform(QV4::Simple
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_shear(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1225,10 +1245,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_globalAlpha(QV4::SimpleCallCont
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_globalAlpha(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    double globalAlpha = ctx->argument(0).toNumber();
+    double globalAlpha = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
 
     if (!qIsFinite(globalAlpha))
         return QV4::Encode::undefined();
@@ -1268,6 +1290,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_globalAlpha(QV4::SimpleCallCont
 */
 QV4::ReturnedValue QQuickJSContext2D::method_get_globalCompositeOperation(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1276,10 +1300,15 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_globalCompositeOperation(QV4::S
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_globalCompositeOperation(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QString mode = ctx->argument(0).toQStringNoThrow();
+    if (!ctx->argumentCount)
+            ctx->throwTypeError();
+
+    QString mode = ctx->arguments[0].toQString();
     QPainter::CompositionMode cm = qt_composite_mode_from_string(mode);
     if (cm == QPainter::CompositionMode_SourceOver && mode != QStringLiteral("source-over"))
         return QV4::Encode::undefined();
@@ -1316,6 +1345,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_globalCompositeOperation(QV4::S
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_fillStyle(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1336,20 +1367,22 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_fillStyle(QV4::SimpleCallContex
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_fillStyle(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QV4::Value value = ctx->argument(0);
+    QV4::ScopedValue value(scope, ctx->argument(0));
     QV8Engine *engine = ctx->engine->v8Engine;
 
-   if (value.asObject()) {
+   if (value->asObject()) {
        QColor color = engine->toVariant(value, qMetaTypeId<QColor>()).value<QColor>();
        if (color.isValid()) {
            r->context->state.fillStyle = color;
            r->context->buffer()->setFillStyle(color);
            r->context->m_fillStyle = value;
        } else {
-           QQuickContext2DStyle *style = value.as<QQuickContext2DStyle>();
+           QQuickContext2DStyle *style = value->as<QQuickContext2DStyle>();
            if (style && style->brush != r->context->state.fillStyle) {
                r->context->state.fillStyle = style->brush;
                r->context->buffer()->setFillStyle(style->brush, style->patternRepeatX, style->patternRepeatY);
@@ -1358,7 +1391,7 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_fillStyle(QV4::SimpleCallContex
                r->context->state.fillPatternRepeatY = style->patternRepeatY;
            }
        }
-   } else if (value.isString()) {
+   } else if (value->isString()) {
        QColor color = qt_color_from_string(value);
        if (color.isValid() && r->context->state.fillStyle != QBrush(color)) {
             r->context->state.fillStyle = QBrush(color);
@@ -1382,6 +1415,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_fillStyle(QV4::SimpleCallContex
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_fillRule(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1391,16 +1426,18 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_fillRule(QV4::SimpleCallContext
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_fillRule(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QV4::Value value = ctx->argument(0);
+    QV4::ScopedValue value(scope, ctx->argument(0));
 
-    if ((value.isString() && value.toQStringNoThrow() == QStringLiteral("WindingFill"))
-        || (value.isInt32() && value.integerValue() == Qt::WindingFill)) {
+    if ((value->isString() && value->toQString() == QStringLiteral("WindingFill"))
+        || (value->isInt32() && value->integerValue() == Qt::WindingFill)) {
         r->context->state.fillRule = Qt::WindingFill;
-    } else if ((value.isString() && value.toQStringNoThrow() == QStringLiteral("OddEvenFill"))
-               || (value.isInt32() && value.integerValue() == Qt::OddEvenFill)) {
+    } else if ((value->isString() && value->toQStringNoThrow() == QStringLiteral("OddEvenFill"))
+               || (value->isInt32() && value->integerValue() == Qt::OddEvenFill)) {
         r->context->state.fillRule = Qt::OddEvenFill;
     } else {
         //error
@@ -1423,6 +1460,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_fillRule(QV4::SimpleCallContext
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_strokeStyle(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1443,20 +1482,22 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_strokeStyle(QV4::SimpleCallCont
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_strokeStyle(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
     QV8Engine *engine = ctx->engine->v8Engine;
-    QV4::Value value = ctx->argument(0);
+    QV4::ScopedValue value(scope, ctx->argument(0));
 
-    if (value.asObject()) {
+    if (value->asObject()) {
         QColor color = engine->toVariant(value, qMetaTypeId<QColor>()).value<QColor>();
         if (color.isValid()) {
             r->context->state.fillStyle = color;
             r->context->buffer()->setStrokeStyle(color);
             r->context->m_strokeStyle = value;
         } else {
-            QQuickContext2DStyle *style = value.as<QQuickContext2DStyle>();
+            QQuickContext2DStyle *style = value->as<QQuickContext2DStyle>();
             if (style && style->brush != r->context->state.strokeStyle) {
                 r->context->state.strokeStyle = style->brush;
                 r->context->buffer()->setStrokeStyle(style->brush, style->patternRepeatX, style->patternRepeatY);
@@ -1466,7 +1507,7 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_strokeStyle(QV4::SimpleCallCont
 
             }
         }
-    } else if (value.isString()) {
+    } else if (value->isString()) {
         QColor color = qt_color_from_string(value);
         if (color.isValid() && r->context->state.strokeStyle != QBrush(color)) {
              r->context->state.strokeStyle = QBrush(color);
@@ -1496,13 +1537,13 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_strokeStyle(QV4::SimpleCallCont
 
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_createLinearGradient(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
 
     QV8Engine *engine = ctx->engine->v8Engine;
-    QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
 
     if (ctx->argumentCount == 4) {
         qreal x0 = ctx->arguments[0].toNumber();
@@ -1542,13 +1583,13 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_createLinearGradient(QV4::
 
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_createRadialGradient(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
 
     QV8Engine *engine = ctx->engine->v8Engine;
-    QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
 
     if (ctx->argumentCount == 6) {
         qreal x0 = ctx->arguments[0].toNumber();
@@ -1596,13 +1637,13 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_createRadialGradient(QV4::
 
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_createConicalGradient(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
 
     QV8Engine *engine = ctx->engine->v8Engine;
-    QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
 
     if (ctx->argumentCount == 6) {
         qreal x = ctx->arguments[0].toNumber();
@@ -1671,13 +1712,12 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_createConicalGradient(QV4:
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_createPattern(QV4::SimpleCallContext *ctx)
 {
-    QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
+    QV4::Scoped<QQuickJSContext2D> r(scope, ctx->thisObject);
     CHECK_CONTEXT(r)
 
-
     QV8Engine *engine = ctx->engine->v8Engine;
-    QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
-    QV4::Scope scope(v4);
 
     if (ctx->argumentCount == 2) {
         QQuickContext2DStyle *pattern = new (v4->memoryManager) QQuickContext2DStyle(v4);
@@ -1743,6 +1783,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_createPattern(QV4::SimpleC
 */
 QV4::ReturnedValue QQuickJSContext2D::method_get_lineCap(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1760,10 +1802,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_lineCap(QV4::SimpleCallContext
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_lineCap(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QString lineCap = ctx->argument(0).toQStringNoThrow();
+    QString lineCap = ctx->arguments[0].toQString();
     Qt::PenCapStyle cap;
     if (lineCap == QStringLiteral("round"))
         cap = Qt::RoundCap;
@@ -1797,6 +1841,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_lineCap(QV4::SimpleCallContext
 */
 QV4::ReturnedValue QQuickJSContext2D::method_get_lineJoin(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1814,10 +1860,15 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_lineJoin(QV4::SimpleCallContext
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_lineJoin(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QString lineJoin = ctx->argument(0).toQStringNoThrow();
+    if (!ctx->argumentCount)
+        ctx->throwTypeError();
+
+    QString lineJoin = ctx->arguments[0].toQString();
     Qt::PenJoinStyle join;
     if (lineJoin == QStringLiteral("round"))
         join = Qt::RoundJoin;
@@ -1841,6 +1892,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_lineJoin(QV4::SimpleCallContext
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_lineWidth(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1849,10 +1902,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_lineWidth(QV4::SimpleCallContex
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_lineWidth(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    qreal w = ctx->argument(0).toNumber();
+    qreal w = ctx->argumentCount ? ctx->arguments[0].toNumber() : -1;
 
     if (w > 0 && qIsFinite(w) && w != r->context->state.lineWidth) {
         r->context->state.lineWidth = w;
@@ -1868,6 +1923,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_lineWidth(QV4::SimpleCallContex
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_miterLimit(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1876,10 +1933,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_miterLimit(QV4::SimpleCallConte
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_miterLimit(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    qreal ml = ctx->argument(0).toNumber();
+    qreal ml = ctx->argumentCount ? ctx->arguments[0].toNumber() : -1;
 
     if (ml > 0 && qIsFinite(ml) && ml != r->context->state.miterLimit) {
         r->context->state.miterLimit = ml;
@@ -1895,6 +1954,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_miterLimit(QV4::SimpleCallConte
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_shadowBlur(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1903,10 +1964,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_shadowBlur(QV4::SimpleCallConte
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_shadowBlur(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    qreal blur = ctx->argument(0).toNumber();
+    qreal blur = ctx->argumentCount ? ctx->arguments[0].toNumber() : -1;
 
     if (blur > 0 && qIsFinite(blur) && blur != r->context->state.shadowBlur) {
         r->context->state.shadowBlur = blur;
@@ -1921,6 +1984,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_shadowBlur(QV4::SimpleCallConte
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_shadowColor(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1929,10 +1994,14 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_shadowColor(QV4::SimpleCallCont
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_shadowColor(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QColor color = qt_color_from_string(ctx->argument(0));
+    QColor color;
+    if (ctx->argumentCount)
+        color = qt_color_from_string(ctx->arguments[0]);
 
     if (color.isValid() && color != r->context->state.shadowColor) {
         r->context->state.shadowColor = color;
@@ -1950,6 +2019,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_shadowColor(QV4::SimpleCallCont
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_shadowOffsetX(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1958,10 +2029,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_shadowOffsetX(QV4::SimpleCallCo
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_shadowOffsetX(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    qreal offsetX = ctx->argument(0).toNumber();
+    qreal offsetX = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     if (qIsFinite(offsetX) && offsetX != r->context->state.shadowOffsetX) {
         r->context->state.shadowOffsetX = offsetX;
         r->context->buffer()->setShadowOffsetX(offsetX);
@@ -1976,6 +2049,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_shadowOffsetX(QV4::SimpleCallCo
  */
 QV4::ReturnedValue QQuickJSContext2D::method_get_shadowOffsetY(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -1984,10 +2059,12 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_shadowOffsetY(QV4::SimpleCallCo
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_shadowOffsetY(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    qreal offsetY = ctx->argument(0).toNumber();
+    qreal offsetY = ctx->argumentCount ? ctx->arguments[0].toNumber() : qSNaN();
     if (qIsFinite(offsetY) && offsetY != r->context->state.shadowOffsetY) {
         r->context->state.shadowOffsetY = offsetY;
         r->context->buffer()->setShadowOffsetY(offsetY);
@@ -1997,6 +2074,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_shadowOffsetY(QV4::SimpleCallCo
 
 QV4::ReturnedValue QQuickJSContext2D::method_get_path(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2005,16 +2084,18 @@ QV4::ReturnedValue QQuickJSContext2D::method_get_path(QV4::SimpleCallContext *ct
 
 QV4::ReturnedValue QQuickJSContext2D::method_set_path(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QV4::Value value = ctx->argument(0);
+    QV4::ScopedValue value(scope, ctx->argument(0));
     r->context->beginPath();
-    if (QV4::QObjectWrapper *qobjectWrapper = value.as<QV4::QObjectWrapper>()) {
+    if (QV4::QObjectWrapper *qobjectWrapper =value->as<QV4::QObjectWrapper>()) {
         if (QQuickPath *path = qobject_cast<QQuickPath*>(qobjectWrapper->object()))
             r->context->m_path = path->path();
     } else {
-        QString path = value.toQStringNoThrow();
+        QString path =value->toQStringNoThrow();
         QQuickSvgParser::parsePathDataFast(path, r->context->m_path);
     }
     r->context->m_v4path = value;
@@ -2028,6 +2109,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_path(QV4::SimpleCallContext *ct
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_clearRect(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2048,6 +2131,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_clearRect(QV4::SimpleCallC
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_fillRect(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2068,6 +2153,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_fillRect(QV4::SimpleCallCo
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_strokeRect(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2100,7 +2187,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_strokeRect(QV4::SimpleCall
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_arc(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2151,7 +2239,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_arc(QV4::SimpleCallContext
 */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_arcTo(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2178,11 +2267,11 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_arcTo(QV4::SimpleCallConte
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_beginPath(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
-
     r->context->beginPath();
 
     return ctx->thisObject.asReturnedValue();
@@ -2209,7 +2298,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_beginPath(QV4::SimpleCallC
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_bezierCurveTo(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2257,7 +2347,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_bezierCurveTo(QV4::SimpleC
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_clip(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2274,7 +2365,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_clip(QV4::SimpleCallContex
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_closePath(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2295,7 +2387,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_closePath(QV4::SimpleCallC
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_fill(QV4::SimpleCallContext *ctx)
 {
-    QV4::Scope scope(ctx);
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r);
     r->context->fill();
@@ -2487,6 +2580,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_stroke(QV4::SimpleCallCont
   */
 QV4::ReturnedValue QQuickJSContext2DPrototype::method_isPointInPath(QV4::SimpleCallContext *ctx)
 {
+    QV4::ExecutionEngine *v4 = ctx->engine;
+    QV4::Scope scope(v4);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT(r)
 
@@ -2555,8 +2650,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_font(QV4::SimpleCallContext *ct
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QString fs = ctx->argument(0).toQStringNoThrow();
-    QFont font = qt_font_from_string(fs, r->context->state.font);
+    QV4::Scoped<QV4::String> s(scope, ctx->argument(0), QV4::Scoped<QV4::String>::Convert);
+    QFont font = qt_font_from_string(s->toQString(), r->context->state.font);
     if (font != r->context->state.font) {
         r->context->state.font = font;
     }
@@ -2605,7 +2700,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_textAlign(QV4::SimpleCallContex
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
 
-    QString textAlign = ctx->argument(0).toQStringNoThrow();
+    QV4::Scoped<QV4::String> s(scope, ctx->argument(0), QV4::Scoped<QV4::String>::Convert);
+    QString textAlign = s->toQString();
 
     QQuickContext2D::TextAlignType ta;
     if (textAlign == QStringLiteral("start"))
@@ -2669,7 +2765,8 @@ QV4::ReturnedValue QQuickJSContext2D::method_set_textBaseline(QV4::SimpleCallCon
     QV4::Scope scope(ctx);
     QQuickJSContext2D *r = ctx->thisObject.as<QQuickJSContext2D>();
     CHECK_CONTEXT_SETTER(r)
-    QString textBaseline = ctx->argument(0).toQStringNoThrow();
+    QV4::Scoped<QV4::String> s(scope, ctx->argument(0), QV4::Scoped<QV4::String>::Convert);
+    QString textBaseline = s->toQString();
 
     QQuickContext2D::TextBaseLineType tb;
     if (textBaseline == QStringLiteral("alphabetic"))
@@ -2767,9 +2864,9 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_measureText(QV4::SimpleCal
     if (ctx->argumentCount == 1) {
         QFontMetrics fm(r->context->state.font);
         uint width = fm.width(ctx->arguments[0].toQStringNoThrow());
-        QV4::Object *tm = ctx->engine->newObject();
+        QV4::Scoped<QV4::Object> tm(scope, ctx->engine->newObject());
         tm->put(ctx->engine->newIdentifier(QStringLiteral("width")), QV4::Value::fromDouble(width));
-        return QV4::Value::fromObject(tm).asReturnedValue();
+        return tm.asReturnedValue();
     }
     return QV4::Encode::undefined();
 }
@@ -2850,14 +2947,15 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_drawImage(QV4::SimpleCallC
 
     QQmlRefPointer<QQuickCanvasPixmap> pixmap;
 
-    if (ctx->arguments[0].isString()) {
-        QUrl url(ctx->arguments[0].toQStringNoThrow());
+    QV4::ScopedValue arg(scope, ctx->arguments[0]);
+    if (arg->isString()) {
+        QUrl url(arg->toQString());
         if (!url.isValid())
             V4THROW_DOM(DOMEXCEPTION_TYPE_MISMATCH_ERR, "drawImage(), type mismatch");
 
         pixmap = r->context->createPixmap(url);
-    } else if (ctx->arguments[0].isObject()) {
-        if (QV4::QObjectWrapper *qobjectWrapper = ctx->arguments[0].as<QV4::QObjectWrapper>()) {
+    } else if (arg->isObject()) {
+        if (QV4::QObjectWrapper *qobjectWrapper = arg->as<QV4::QObjectWrapper>()) {
             if (QQuickImage *imageItem = qobject_cast<QQuickImage*>(qobjectWrapper->object())) {
                 pixmap.take(r->context->createPixmap(imageItem->source()));
             } else if (QQuickCanvasItem *canvas = qobject_cast<QQuickCanvasItem*>(qobjectWrapper->object())) {
@@ -2867,7 +2965,7 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_drawImage(QV4::SimpleCallC
             } else {
                 V4THROW_DOM(DOMEXCEPTION_TYPE_MISMATCH_ERR, "drawImage(), type mismatch");
             }
-        } else if (QQuickJSContext2DImageData *imageData = ctx->arguments[0].as<QQuickJSContext2DImageData>()) {
+        } else if (QQuickJSContext2DImageData *imageData = arg->as<QQuickJSContext2DImageData>()) {
             QQuickJSContext2DPixelData *pix = imageData->pixelData.as<QQuickJSContext2DPixelData>();
             if (pix && !pix->image.isNull()) {
                 pixmap.take(new QQuickCanvasPixmap(pix->image, r->context->canvas()->window()));
@@ -2875,7 +2973,7 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_drawImage(QV4::SimpleCallC
                 V4THROW_DOM(DOMEXCEPTION_TYPE_MISMATCH_ERR, "drawImage(), type mismatch");
             }
         } else {
-            QUrl url(ctx->arguments[0].toQStringNoThrow());
+            QUrl url(arg->toQStringNoThrow());
             if (url.isValid())
                 pixmap = r->context->createPixmap(url);
             else
@@ -3039,6 +3137,8 @@ QV4::ReturnedValue QQuickJSContext2DPixelData::proto_get_length(QV4::SimpleCallC
 
 QV4::ReturnedValue QQuickJSContext2DPixelData::getIndexed(QV4::Managed *m, uint index, bool *hasProperty)
 {
+    QV4::ExecutionEngine *v4 = m->engine();
+    QV4::Scope scope(v4);
     QQuickJSContext2DPixelData *r = m->as<QQuickJSContext2DPixelData>();
     if (!m)
         m->engine()->current->throwTypeError();
@@ -3069,6 +3169,8 @@ QV4::ReturnedValue QQuickJSContext2DPixelData::getIndexed(QV4::Managed *m, uint
 
 void QQuickJSContext2DPixelData::putIndexed(QV4::Managed *m, uint index, const QV4::Value &value)
 {
+    QV4::ExecutionEngine *v4 = m->engine();
+    QV4::Scope scope(v4);
     QQuickJSContext2DPixelData *r = m->as<QQuickJSContext2DPixelData>();
     if (!r)
         m->engine()->current->throwTypeError();
@@ -3127,15 +3229,16 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_createImageData(QV4::Simpl
     QV8Engine *engine = ctx->engine->v8Engine;
 
     if (ctx->argumentCount == 1) {
-        if (QQuickJSContext2DImageData *imgData = ctx->arguments[0].as<QQuickJSContext2DImageData>()) {
+        QV4::ScopedValue arg0(scope, ctx->arguments[0]);
+        if (QQuickJSContext2DImageData *imgData = arg0->as<QQuickJSContext2DImageData>()) {
             QQuickJSContext2DPixelData *pa = imgData->pixelData.as<QQuickJSContext2DPixelData>();
             if (pa) {
                 qreal w = pa->image.width();
                 qreal h = pa->image.height();
                 return qt_create_image_data(w, h, engine, QImage()).asReturnedValue();
             }
-        } else if (ctx->arguments[0].isString()) {
-            QImage image = r->context->createPixmap(QUrl(ctx->arguments[0].toQStringNoThrow()))->image();
+        } else if (arg0->isString()) {
+            QImage image = r->context->createPixmap(QUrl(arg0->toQStringNoThrow()))->image();
             return qt_create_image_data(image.width(), image.height(), engine, image).asReturnedValue();
         }
     } else if (ctx->argumentCount == 2) {
@@ -3195,7 +3298,8 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_putImageData(QV4::SimpleCa
     if (ctx->argumentCount != 3 && ctx->argumentCount != 7)
         return QV4::Encode::undefined();
 
-    if (!ctx->arguments[0].isObject())
+    QV4::ScopedValue arg0(scope, ctx->arguments[0]);
+    if (!arg0->isObject())
         V4THROW_DOM(DOMEXCEPTION_TYPE_MISMATCH_ERR, "Context2D::putImageData, the image data type mismatch");
 
     qreal dx = ctx->arguments[1].toNumber();
@@ -3205,7 +3309,7 @@ QV4::ReturnedValue QQuickJSContext2DPrototype::method_putImageData(QV4::SimpleCa
     if (!qIsFinite(dx) || !qIsFinite(dy))
         V4THROW_DOM(DOMEXCEPTION_NOT_SUPPORTED_ERR, "putImageData() : Invalid arguments");
 
-    QQuickJSContext2DImageData *imageData = ctx->arguments[0].as<QQuickJSContext2DImageData>();
+    QQuickJSContext2DImageData *imageData = arg0->as<QQuickJSContext2DImageData>();
     if (!imageData)
         return ctx->thisObject.asReturnedValue();
 
@@ -4048,8 +4152,9 @@ QImage QQuickContext2D::toImage(const QRectF& bounds)
 QQuickContext2DEngineData::QQuickContext2DEngineData(QV8Engine *engine)
 {
     QV4::ExecutionEngine *v4 = QV8Engine::getV4(engine);
+    QV4::Scope scope(v4);
 
-    QV4::Object *proto = new (v4->memoryManager) QQuickJSContext2DPrototype(v4);
+    QV4::Scoped<QV4::Object> proto(scope, new (v4->memoryManager) QQuickJSContext2DPrototype(v4));
     proto->defineAccessorProperty(v4, QStringLiteral("strokeStyle"), QQuickJSContext2D::method_get_strokeStyle, QQuickJSContext2D::method_set_strokeStyle);
     proto->defineAccessorProperty(v4, QStringLiteral("font"), QQuickJSContext2D::method_get_font, QQuickJSContext2D::method_set_font);
     proto->defineAccessorProperty(v4, QStringLiteral("fillRule"), QQuickJSContext2D::method_get_fillRule, QQuickJSContext2D::method_set_fillRule);
@@ -4067,15 +4172,15 @@ QQuickContext2DEngineData::QQuickContext2DEngineData(QV8Engine *engine)
     proto->defineAccessorProperty(v4, QStringLiteral("lineWidth"), QQuickJSContext2D::method_get_lineWidth, QQuickJSContext2D::method_set_lineWidth);
     proto->defineAccessorProperty(v4, QStringLiteral("textAlign"), QQuickJSContext2D::method_get_textAlign, QQuickJSContext2D::method_set_textAlign);
     proto->defineAccessorProperty(v4, QStringLiteral("shadowBlur"), QQuickJSContext2D::method_get_shadowBlur, QQuickJSContext2D::method_set_shadowBlur);
-    contextPrototype = QV4::Value::fromObject(proto);
+    contextPrototype = proto;
 
     proto = v4->newObject();
     proto->defineDefaultProperty(v4, QStringLiteral("addColorStop"), QQuickContext2DStyle::gradient_proto_addColorStop, 0);
-    gradientProto = QV4::Value::fromObject(proto);
+    gradientProto = proto;
 
     proto = v4->newObject();
     proto->defineAccessorProperty(v4->id_length, QQuickJSContext2DPixelData::proto_get_length, 0);
-    pixelArrayProto = QV4::Value::fromObject(proto);
+    pixelArrayProto = proto;
 }
 
 QQuickContext2DEngineData::~QQuickContext2DEngineData()
diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index 98a87a4bcf..341339e7b9 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -3878,8 +3878,9 @@ void QQuickItem::mapFromItem(QQmlV4Function *args) const
         }
 
         QV4::ExecutionEngine *v4 = QV8Engine::getV4(args->engine());
-        QV4::Object *rv = v4->newObject();
-        args->setReturnValue(QV4::Value::fromObject(rv));
+        QV4::Scope scope(v4);
+        QV4::Scoped<QV4::Object> rv(scope, v4->newObject());
+        args->setReturnValue(rv.asValue());
 
         qreal x = (args->length() > 1) ? (*args)[1].asDouble() : 0;
         qreal y = (args->length() > 2) ? (*args)[2].asDouble() : 0;
@@ -3952,8 +3953,9 @@ void QQuickItem::mapToItem(QQmlV4Function *args) const
         }
 
         QV4::ExecutionEngine *v4 = QV8Engine::getV4(args->engine());
-        QV4::Object *rv = v4->newObject();
-        args->setReturnValue(QV4::Value::fromObject(rv));
+        QV4::Scope scope(v4);
+        QV4::Scoped<QV4::Object> rv(scope, v4->newObject());
+        args->setReturnValue(rv.asValue());
 
         qreal x = (args->length() > 1) ? (*args)[1].asDouble() : 0;
         qreal y = (args->length() > 2) ? (*args)[2].asDouble() : 0;