Avoid side effects when en exception has been thrown.

We don't want to check for exceptions after every single
line on our runtime methods. A better way to handle this
is to add the check in all methods that have direct side
effects (as e.g. writing to a property of the JS stack).

We also need to return whereever we throw an exception.
To simplify the code, ExecutionContext::throwXxx methods now
return a ReturnedValue (always undefined) for convenience.

Change-Id: Ide6c804f819c731a3f14c6c43121d08029c9fb90
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

35 files changed, 485 insertions, 280 deletions

diff --git a/src/qml/jsruntime/qv4argumentsobject.cpp b/src/qml/jsruntime/qv4argumentsobject.cpp
index 47b149c9d5..fb4fcb7b1a 100644
--- a/src/qml/jsruntime/qv4argumentsobject.cpp
+++ b/src/qml/jsruntime/qv4argumentsobject.cpp
@@ -139,7 +139,7 @@ bool ArgumentsObject::defineOwnProperty(ExecutionContext *ctx, uint index, const
     }
 
     if (ctx->strictMode && !result)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     return result;
 }
 
@@ -152,7 +152,7 @@ ReturnedValue ArgumentsGetterFunction::call(Managed *getter, CallData *callData)
     Scoped<ArgumentsGetterFunction> g(scope, static_cast<ArgumentsGetterFunction *>(getter));
     Scoped<ArgumentsObject> o(scope, callData->thisObject.as<ArgumentsObject>());
     if (!o)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     Q_ASSERT(g->index < o->context->callData->argc);
     return o->context->argument(g->index);
@@ -167,7 +167,7 @@ ReturnedValue ArgumentsSetterFunction::call(Managed *setter, CallData *callData)
     Scoped<ArgumentsSetterFunction> s(scope, static_cast<ArgumentsSetterFunction *>(setter));
     Scoped<ArgumentsObject> o(scope, callData->thisObject.as<ArgumentsObject>());
     if (!o)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     Q_ASSERT(s->index < o->context->callData->argc);
     o->context->callData->args[s->index] = callData->argc ? callData->args[0].asReturnedValue() : Encode::undefined();
diff --git a/src/qml/jsruntime/qv4arrayobject.cpp b/src/qml/jsruntime/qv4arrayobject.cpp
index 3913b9ffe7..b1308e12fb 100644
--- a/src/qml/jsruntime/qv4arrayobject.cpp
+++ b/src/qml/jsruntime/qv4arrayobject.cpp
@@ -65,7 +65,7 @@ ReturnedValue ArrayCtor::construct(Managed *m, CallData *callData)
         len = callData->args[0].asArrayLength(&ok);
 
         if (!ok)
-            v4->current->throwRangeError(callData->args[0]);
+            return v4->current->throwRangeError(callData->args[0]);
 
         if (len < 0x1000)
             a->arrayReserve(len);
@@ -141,6 +141,8 @@ ReturnedValue ArrayPrototype::method_toString(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject o(scope, ctx->callData->thisObject, ScopedObject::Convert);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
     ScopedString s(scope, ctx->engine->newString("join"));
     ScopedFunctionObject f(scope, o->get(s));
     if (!!f) {
@@ -162,6 +164,8 @@ ReturnedValue ArrayPrototype::method_concat(SimpleCallContext *ctx)
     ScopedObject result(scope, ctx->engine->newArrayObject());
 
     ScopedObject thisObject(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!thisObject)
+        return Encode::undefined();
     ScopedArrayObject instance(scope, thisObject);
     if (instance) {
         result->copyArrayData(instance.getPointer());
@@ -240,6 +244,8 @@ ReturnedValue ArrayPrototype::method_pop(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
 
     if (!len) {
@@ -262,6 +268,8 @@ ReturnedValue ArrayPrototype::method_push(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
 
     if (len + ctx->callData->argc < len) {
@@ -277,7 +285,7 @@ ReturnedValue ArrayPrototype::method_push(SimpleCallContext *ctx)
             instance->put(ctx->engine->id_length, ScopedValue(scope, Primitive::fromDouble(newLen)));
         else {
             ScopedString str(scope, ctx->engine->newString(QStringLiteral("Array.prototype.push: Overflow")));
-            ctx->throwRangeError(str);
+            return ctx->throwRangeError(str);
         }
         return Encode(newLen);
     }
@@ -314,6 +322,8 @@ ReturnedValue ArrayPrototype::method_reverse(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint length = getLength(ctx, instance);
 
     int lo = 0, hi = length - 1;
@@ -340,6 +350,8 @@ ReturnedValue ArrayPrototype::method_shift(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
 
     if (!len) {
@@ -394,6 +406,8 @@ ReturnedValue ArrayPrototype::method_slice(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject o(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!o)
+        return Encode::undefined();
 
     Scoped<ArrayObject> result(scope, ctx->engine->newArrayObject());
     uint len = getLength(ctx, o);
@@ -433,6 +447,8 @@ ReturnedValue ArrayPrototype::method_sort(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
@@ -445,6 +461,8 @@ ReturnedValue ArrayPrototype::method_splice(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
 
     Scoped<ArrayObject> newArray(scope, ctx->engine->newArrayObject());
@@ -505,6 +523,8 @@ ReturnedValue ArrayPrototype::method_unshift(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
 
     ScopedValue v(scope);
@@ -556,6 +576,8 @@ ReturnedValue ArrayPrototype::method_indexOf(SimpleCallContext *ctx)
     Scope scope(ctx);
 
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
     if (!len)
         return Encode(-1);
@@ -596,6 +618,8 @@ ReturnedValue ArrayPrototype::method_lastIndexOf(SimpleCallContext *ctx)
     Scope scope(ctx);
 
     ScopedObject instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
     uint len = getLength(ctx, instance);
     if (!len)
         return Encode(-1);
@@ -635,12 +659,14 @@ ReturnedValue ArrayPrototype::method_every(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedCallData callData(scope, 3);
     callData->args[2] = instance;
@@ -667,12 +693,14 @@ ReturnedValue ArrayPrototype::method_some(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedCallData callData(scope, 3);
     callData->thisObject = ctx->argument(1);
@@ -699,12 +727,14 @@ ReturnedValue ArrayPrototype::method_forEach(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedCallData callData(scope, 3);
     callData->thisObject = ctx->argument(1);
@@ -728,12 +758,14 @@ ReturnedValue ArrayPrototype::method_map(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<ArrayObject> a(scope, ctx->engine->newArrayObject());
     a->arrayReserve(len);
@@ -763,12 +795,14 @@ ReturnedValue ArrayPrototype::method_filter(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<ArrayObject> a(scope, ctx->engine->newArrayObject());
     a->arrayReserve(len);
@@ -802,12 +836,14 @@ ReturnedValue ArrayPrototype::method_reduce(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     uint k = 0;
     ScopedValue acc(scope);
@@ -824,7 +860,7 @@ ReturnedValue ArrayPrototype::method_reduce(SimpleCallContext *ctx)
             ++k;
         }
         if (!kPresent)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
     }
 
     ScopedCallData callData(scope, 4);
@@ -850,16 +886,18 @@ ReturnedValue ArrayPrototype::method_reduceRight(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<Object> instance(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!instance)
+        return Encode::undefined();
 
     uint len = getLength(ctx, instance);
 
     Scoped<FunctionObject> callback(scope, ctx->argument(0));
     if (!callback)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (len == 0) {
         if (ctx->callData->argc == 1)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
         return ctx->argument(1);
     }
 
@@ -877,7 +915,7 @@ ReturnedValue ArrayPrototype::method_reduceRight(SimpleCallContext *ctx)
             --k;
         }
         if (!kPresent)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
     }
 
     ScopedCallData callData(scope, 4);
diff --git a/src/qml/jsruntime/qv4booleanobject.cpp b/src/qml/jsruntime/qv4booleanobject.cpp
index 025f98351f..d9de6d9fba 100644
--- a/src/qml/jsruntime/qv4booleanobject.cpp
+++ b/src/qml/jsruntime/qv4booleanobject.cpp
@@ -86,7 +86,7 @@ ReturnedValue BooleanPrototype::method_toString(SimpleCallContext *ctx)
         Scope scope(ctx);
         Scoped<BooleanObject> thisObject(scope, ctx->callData->thisObject);
         if (!thisObject)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
         result = thisObject->value.booleanValue();
     }
 
@@ -101,7 +101,7 @@ ReturnedValue BooleanPrototype::method_valueOf(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<BooleanObject> thisObject(scope, ctx->callData->thisObject);
     if (!thisObject)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return thisObject->value.asReturnedValue();
 }
diff --git a/src/qml/jsruntime/qv4context.cpp b/src/qml/jsruntime/qv4context.cpp
index c14d987171..42db229c9b 100644
--- a/src/qml/jsruntime/qv4context.cpp
+++ b/src/qml/jsruntime/qv4context.cpp
@@ -392,6 +392,7 @@ void ExecutionContext::setProperty(const StringRef name, const ValueRef value)
     if (strictMode || name->equals(engine->id_this)) {
         ScopedValue n(scope, name.asReturnedValue());
         throwReferenceError(n);
+        return;
     }
     engine->globalObject->put(name, value);
 }
@@ -457,8 +458,7 @@ ReturnedValue ExecutionContext::getProperty(const StringRef name)
         }
     }
     ScopedValue n(scope, name.asReturnedValue());
-    throwReferenceError(n);
-    return 0;
+    return throwReferenceError(n);
 }
 
 ReturnedValue ExecutionContext::getPropertyAndBase(const StringRef name, ObjectRef base)
@@ -527,58 +527,57 @@ ReturnedValue ExecutionContext::getPropertyAndBase(const StringRef name, ObjectR
         }
     }
     ScopedValue n(scope, name.asReturnedValue());
-    throwReferenceError(n);
-    return 0;
+    return throwReferenceError(n);
 }
 
 
-void ExecutionContext::throwError(const ValueRef value)
+ReturnedValue ExecutionContext::throwError(const ValueRef value)
 {
-    engine->throwException(value);
+    return engine->throwException(value);
 }
 
-void ExecutionContext::throwError(const QString &message)
+ReturnedValue ExecutionContext::throwError(const QString &message)
 {
     Scope scope(this);
     ScopedValue v(scope, engine->newString(message));
     v = engine->newErrorObject(v);
-    throwError(v);
+    return throwError(v);
 }
 
-void ExecutionContext::throwSyntaxError(const QString &message, const QString &fileName, int line, int column)
+ReturnedValue ExecutionContext::throwSyntaxError(const QString &message, const QString &fileName, int line, int column)
 {
     Scope scope(this);
     Scoped<Object> error(scope, engine->newSyntaxErrorObject(message, fileName, line, column));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwSyntaxError(const QString &message)
+ReturnedValue ExecutionContext::throwSyntaxError(const QString &message)
 {
     Scope scope(this);
     Scoped<Object> error(scope, engine->newSyntaxErrorObject(message));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwTypeError()
+ReturnedValue ExecutionContext::throwTypeError()
 {
     Scope scope(this);
     Scoped<Object> error(scope, engine->newTypeErrorObject(QStringLiteral("Type error")));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwTypeError(const QString &message)
+ReturnedValue ExecutionContext::throwTypeError(const QString &message)
 {
     Scope scope(this);
     Scoped<Object> error(scope, engine->newTypeErrorObject(message));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwUnimplemented(const QString &message)
+ReturnedValue ExecutionContext::throwUnimplemented(const QString &message)
 {
     Scope scope(this);
     ScopedValue v(scope, engine->newString(QStringLiteral("Unimplemented ") + message));
     v = engine->newErrorObject(v);
-    throwError(v);
+    return throwError(v);
 }
 
 ReturnedValue ExecutionContext::catchException(StackTrace *trace)
@@ -586,37 +585,37 @@ ReturnedValue ExecutionContext::catchException(StackTrace *trace)
     return engine->catchException(this, trace);
 }
 
-void ExecutionContext::throwReferenceError(const ValueRef value)
+ReturnedValue ExecutionContext::throwReferenceError(const ValueRef value)
 {
     Scope scope(this);
     Scoped<String> s(scope, value->toString(this));
     QString msg = s->toQString() + QStringLiteral(" is not defined");
     Scoped<Object> error(scope, engine->newReferenceErrorObject(msg));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwReferenceError(const QString &message, const QString &fileName, int line, int column)
+ReturnedValue ExecutionContext::throwReferenceError(const QString &message, const QString &fileName, int line, int column)
 {
     Scope scope(this);
     QString msg = message + QStringLiteral(" is not defined");
     Scoped<Object> error(scope, engine->newReferenceErrorObject(msg, fileName, line, column));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwRangeError(const ValueRef value)
+ReturnedValue ExecutionContext::throwRangeError(const ValueRef value)
 {
     Scope scope(this);
     ScopedString s(scope, value->toString(this));
     QString msg = s->toQString() + QStringLiteral(" out of range");
     ScopedObject error(scope, engine->newRangeErrorObject(msg));
-    throwError(error);
+    return throwError(error);
 }
 
-void ExecutionContext::throwURIError(const ValueRef msg)
+ReturnedValue ExecutionContext::throwURIError(const ValueRef msg)
 {
     Scope scope(this);
     ScopedObject error(scope, engine->newURIErrorObject(msg));
-    throwError(error);
+    return throwError(error);
 }
 
 void SimpleCallContext::initSimpleCallContext(ExecutionEngine *engine)
diff --git a/src/qml/jsruntime/qv4context_p.h b/src/qml/jsruntime/qv4context_p.h
index e85350451b..bd779f23f4 100644
--- a/src/qml/jsruntime/qv4context_p.h
+++ b/src/qml/jsruntime/qv4context_p.h
@@ -127,17 +127,17 @@ struct Q_QML_EXPORT ExecutionContext
 
     void createMutableBinding(const StringRef name, bool deletable);
 
-    void throwError(const QV4::ValueRef value);
-    void throwError(const QString &message);
-    void throwSyntaxError(const QString &message);
-    void throwSyntaxError(const QString &message, const QString &fileName, int line, int column);
-    void throwTypeError();
-    void throwTypeError(const QString &message);
-    void throwReferenceError(const ValueRef value);
-    void throwReferenceError(const QString &value, const QString &fileName, int line, int column);
-    void throwRangeError(const ValueRef value);
-    void throwURIError(const ValueRef msg);
-    void throwUnimplemented(const QString &message);
+    ReturnedValue throwError(const QV4::ValueRef value);
+    ReturnedValue throwError(const QString &message);
+    ReturnedValue throwSyntaxError(const QString &message);
+    ReturnedValue throwSyntaxError(const QString &message, const QString &fileName, int line, int column);
+    ReturnedValue throwTypeError();
+    ReturnedValue throwTypeError(const QString &message);
+    ReturnedValue throwReferenceError(const ValueRef value);
+    ReturnedValue throwReferenceError(const QString &value, const QString &fileName, int line, int column);
+    ReturnedValue throwRangeError(const ValueRef value);
+    ReturnedValue throwURIError(const ValueRef msg);
+    ReturnedValue throwUnimplemented(const QString &message);
 
     void setProperty(const StringRef name, const ValueRef value);
     ReturnedValue getProperty(const StringRef name);
diff --git a/src/qml/jsruntime/qv4dateobject.cpp b/src/qml/jsruntime/qv4dateobject.cpp
index ffc5fa891a..cfc4843ec9 100644
--- a/src/qml/jsruntime/qv4dateobject.cpp
+++ b/src/qml/jsruntime/qv4dateobject.cpp
@@ -1003,7 +1003,7 @@ ReturnedValue DatePrototype::method_setTime(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<DateObject> self(scope, ctx->callData->thisObject);
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
     self->value.setDouble(TimeClip(t));
@@ -1015,7 +1015,7 @@ ReturnedValue DatePrototype::method_setMilliseconds(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<DateObject> self(scope, ctx->callData->thisObject);
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     double ms = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1027,7 +1027,7 @@ ReturnedValue DatePrototype::method_setUTCMilliseconds(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double ms = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1039,7 +1039,7 @@ ReturnedValue DatePrototype::method_setSeconds(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     double sec = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1053,7 +1053,7 @@ ReturnedValue DatePrototype::method_setUTCSeconds(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double sec = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1067,7 +1067,7 @@ ReturnedValue DatePrototype::method_setMinutes(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     double min = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1082,7 +1082,7 @@ ReturnedValue DatePrototype::method_setUTCMinutes(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double min = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1097,7 +1097,7 @@ ReturnedValue DatePrototype::method_setHours(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     double hour = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1113,7 +1113,7 @@ ReturnedValue DatePrototype::method_setUTCHours(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double hour = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1129,7 +1129,7 @@ ReturnedValue DatePrototype::method_setDate(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     double date = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1142,7 +1142,7 @@ ReturnedValue DatePrototype::method_setUTCDate(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double date = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1155,7 +1155,7 @@ ReturnedValue DatePrototype::method_setMonth(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     double month = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1169,7 +1169,7 @@ ReturnedValue DatePrototype::method_setUTCMonth(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double month = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1183,7 +1183,7 @@ ReturnedValue DatePrototype::method_setYear(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     if (std::isnan(t))
@@ -1209,7 +1209,7 @@ ReturnedValue DatePrototype::method_setUTCFullYear(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     double year = ctx->callData->argc ? ctx->callData->args[0].toNumber() : qSNaN();
@@ -1224,7 +1224,7 @@ ReturnedValue DatePrototype::method_setFullYear(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = LocalTime(self->value.asDouble());
     if (std::isnan(t))
@@ -1241,7 +1241,7 @@ ReturnedValue DatePrototype::method_toUTCString(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     return ctx->engine->newString(ToUTCString(t))->asReturnedValue();
@@ -1264,11 +1264,11 @@ ReturnedValue DatePrototype::method_toISOString(SimpleCallContext *ctx)
 {
     DateObject *self = ctx->callData->thisObject.asDateObject();
     if (!self)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     double t = self->value.asDouble();
     if (!std::isfinite(t))
-        ctx->throwRangeError(ctx->callData->thisObject);
+        return ctx->throwRangeError(ctx->callData->thisObject);
 
     QString result;
     int year = (int)YearFromTime(t);
@@ -1312,7 +1312,7 @@ ReturnedValue DatePrototype::method_toJSON(SimpleCallContext *ctx)
     FunctionObject *toIso = v->asFunctionObject();
 
     if (!toIso)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedCallData callData(scope, 0);
     callData->thisObject = ctx->callData->thisObject;
diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index b0ede6fa20..cf39d7df4f 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -81,8 +81,7 @@ static QBasicAtomicInt engineSerial = Q_BASIC_ATOMIC_INITIALIZER(1);
 
 static ReturnedValue throwTypeError(SimpleCallContext *ctx)
 {
-    ctx->throwTypeError();
-    return Encode::undefined();
+    return ctx->throwTypeError();
 }
 
 ExecutionEngine::ExecutionEngine(QQmlJS::EvalISelFactory *factory)
@@ -807,7 +806,7 @@ QmlExtensions *ExecutionEngine::qmlExtensions()
     return m_qmlExtensions;
 }
 
-void ExecutionEngine::throwException(const ValueRef value)
+ReturnedValue ExecutionEngine::throwException(const ValueRef value)
 {
 //    Q_ASSERT(!hasException);
     hasException = true;
@@ -822,6 +821,7 @@ void ExecutionEngine::throwException(const ValueRef value)
     if (debugger)
         debugger->aboutToThrow(value);
 
+    return Encode::undefined();
 }
 
 ReturnedValue ExecutionEngine::catchException(ExecutionContext *catchingContext, StackTrace *trace)
diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index 94a4dff5b4..f6db36b0d0 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -326,7 +326,7 @@ struct Q_QML_EXPORT ExecutionEngine
     quint32 hasException;
     StackTrace exceptionStackTrace;
 
-    void throwException(const ValueRef value);
+    ReturnedValue throwException(const ValueRef value);
     ReturnedValue catchException(ExecutionContext *catchingContext, StackTrace *trace);
 
     // Use only inside catch(...) -- will re-throw if no JS exception
diff --git a/src/qml/jsruntime/qv4errorobject.cpp b/src/qml/jsruntime/qv4errorobject.cpp
index ef9dc473f3..12ac4218bd 100644
--- a/src/qml/jsruntime/qv4errorobject.cpp
+++ b/src/qml/jsruntime/qv4errorobject.cpp
@@ -172,7 +172,7 @@ ReturnedValue ErrorObject::method_get_stack(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<ErrorObject> This(scope, ctx->callData->thisObject);
     if (!This)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     if (!This->stack) {
         QString trace;
         for (int i = 0; i < This->stackTrace.count(); ++i) {
@@ -389,7 +389,7 @@ ReturnedValue ErrorPrototype::method_toString(SimpleCallContext *ctx)
 
     Object *o = ctx->callData->thisObject.asObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedValue name(scope, o->get(ctx->engine->id_name));
     QString qname;
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index 3e28024bbf..b2ef86525f 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -166,8 +166,10 @@ bool FunctionObject::hasInstance(Managed *that, const ValueRef value)
         return false;
 
     Scoped<Object> o(scope, f->get(scope.engine->id_prototype));
-    if (!o)
+    if (!o) {
         scope.engine->current->throwTypeError();
+        return false;
+    }
 
     while (v) {
         v = v->prototype();
@@ -259,13 +261,13 @@ ReturnedValue FunctionCtor::construct(Managed *that, CallData *callData)
     const bool parsed = parser.parseExpression();
 
     if (!parsed)
-        f->engine()->current->throwSyntaxError(0);
+        return f->engine()->current->throwSyntaxError(0);
 
     using namespace QQmlJS::AST;
     FunctionExpression *fe = QQmlJS::AST::cast<FunctionExpression *>(parser.rootNode());
     ExecutionEngine *v4 = f->engine();
     if (!fe)
-        v4->current->throwSyntaxError(0);
+        return v4->current->throwSyntaxError(0);
 
     QQmlJS::V4IR::Module module(v4->debugger != 0);
 
@@ -312,7 +314,7 @@ ReturnedValue FunctionPrototype::method_toString(SimpleCallContext *ctx)
 {
     FunctionObject *fun = ctx->callData->thisObject.asFunctionObject();
     if (!fun)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return ctx->engine->newString(QStringLiteral("function() { [code] }"))->asReturnedValue();
 }
@@ -322,7 +324,7 @@ ReturnedValue FunctionPrototype::method_apply(SimpleCallContext *ctx)
     Scope scope(ctx);
     FunctionObject *o = ctx->callData->thisObject.asFunctionObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedValue arg(scope, ctx->argument(1));
 
@@ -331,10 +333,8 @@ ReturnedValue FunctionPrototype::method_apply(SimpleCallContext *ctx)
     quint32 len;
     if (!arr) {
         len = 0;
-        if (!arg->isNullOrUndefined()) {
-            ctx->throwTypeError();
-            return Encode::undefined();
-        }
+        if (!arg->isNullOrUndefined())
+            return ctx->throwTypeError();
     } else {
         len = ArrayPrototype::getLength(ctx, arr);
     }
@@ -364,7 +364,7 @@ ReturnedValue FunctionPrototype::method_call(SimpleCallContext *ctx)
 
     FunctionObject *o = ctx->callData->thisObject.asFunctionObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedCallData callData(scope, ctx->callData->argc ? ctx->callData->argc - 1 : 0);
     if (ctx->callData->argc) {
@@ -380,7 +380,7 @@ ReturnedValue FunctionPrototype::method_bind(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<FunctionObject> target(scope, ctx->callData->thisObject);
     if (!target)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedValue boundThis(scope, ctx->argument(0));
     QVector<SafeValue> boundArgs;
@@ -568,8 +568,7 @@ BuiltinFunction::BuiltinFunction(ExecutionContext *scope, const StringRef name,
 
 ReturnedValue BuiltinFunction::construct(Managed *f, CallData *)
 {
-    f->engine()->current->throwTypeError();
-    return Encode::undefined();
+    return f->engine()->current->throwTypeError();
 }
 
 ReturnedValue BuiltinFunction::call(Managed *that, CallData *callData)
diff --git a/src/qml/jsruntime/qv4functionobject_p.h b/src/qml/jsruntime/qv4functionobject_p.h
index eeb041ddc0..fe69625061 100644
--- a/src/qml/jsruntime/qv4functionobject_p.h
+++ b/src/qml/jsruntime/qv4functionobject_p.h
@@ -197,8 +197,7 @@ struct IndexedBuiltinFunction: FunctionObject
 
     static ReturnedValue construct(Managed *m, CallData *)
     {
-        m->engine()->current->throwTypeError();
-        return Encode::undefined();
+        return m->engine()->current->throwTypeError();
     }
 
     static ReturnedValue call(Managed *that, CallData *callData);
diff --git a/src/qml/jsruntime/qv4globalobject.cpp b/src/qml/jsruntime/qv4globalobject.cpp
index d95ab9791f..084b508b52 100644
--- a/src/qml/jsruntime/qv4globalobject.cpp
+++ b/src/qml/jsruntime/qv4globalobject.cpp
@@ -545,6 +545,9 @@ ReturnedValue GlobalFunctions::method_parseFloat(SimpleCallContext *ctx)
 
     // [15.1.2.3] step by step:
     Scoped<String> inputString(scope, ctx->argument(0), Scoped<String>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
+
     QString trimmed = inputString->toQString().trimmed(); // 2
 
     // 4:
@@ -604,7 +607,7 @@ ReturnedValue GlobalFunctions::method_decodeURI(SimpleCallContext *context)
     if (!ok) {
         Scope scope(context);
         ScopedString s(scope, context->engine->newString(QStringLiteral("malformed URI sequence")));
-        context->throwURIError(s);
+        return context->throwURIError(s);
     }
 
     return context->engine->newString(out)->asReturnedValue();
@@ -622,7 +625,7 @@ ReturnedValue GlobalFunctions::method_decodeURIComponent(SimpleCallContext *cont
     if (!ok) {
         Scope scope(context);
         ScopedString s(scope, context->engine->newString(QStringLiteral("malformed URI sequence")));
-        context->throwURIError(s);
+        return context->throwURIError(s);
     }
 
     return context->engine->newString(out)->asReturnedValue();
@@ -640,7 +643,7 @@ ReturnedValue GlobalFunctions::method_encodeURI(SimpleCallContext *context)
     if (!ok) {
         Scope scope(context);
         ScopedString s(scope, context->engine->newString(QStringLiteral("malformed URI sequence")));
-        context->throwURIError(s);
+        return context->throwURIError(s);
     }
 
     return context->engine->newString(out)->asReturnedValue();
@@ -658,7 +661,7 @@ ReturnedValue GlobalFunctions::method_encodeURIComponent(SimpleCallContext *cont
     if (!ok) {
         Scope scope(context);
         ScopedString s(scope, context->engine->newString(QStringLiteral("malformed URI sequence")));
-        context->throwURIError(s);
+        return context->throwURIError(s);
     }
 
     return context->engine->newString(out)->asReturnedValue();
diff --git a/src/qml/jsruntime/qv4jsonobject.cpp b/src/qml/jsruntime/qv4jsonobject.cpp
index 331b528409..721843afba 100644
--- a/src/qml/jsruntime/qv4jsonobject.cpp
+++ b/src/qml/jsruntime/qv4jsonobject.cpp
@@ -779,8 +779,10 @@ QString Stringify::makeMember(const QString &key, ValueRef v)
 
 QString Stringify::JO(ObjectRef o)
 {
-    if (stack.contains(o.getPointer()))
+    if (stack.contains(o.getPointer())) {
         ctx->throwTypeError();
+        return QString();
+    }
 
     Scope scope(ctx);
 
@@ -834,8 +836,10 @@ QString Stringify::JO(ObjectRef o)
 
 QString Stringify::JA(ArrayObjectRef a)
 {
-    if (stack.contains(a.getPointer()))
+    if (stack.contains(a.getPointer())) {
         ctx->throwTypeError();
+        return QString();
+    }
 
     Scope scope(a->engine());
 
@@ -901,7 +905,7 @@ ReturnedValue JsonObject::method_parse(SimpleCallContext *ctx)
     ScopedValue result(scope, parser.parse(&error));
     if (error.error != QJsonParseError::NoError) {
         DEBUG << "parse error" << error.errorString();
-        ctx->throwSyntaxError("JSON.parse: Parse error");
+        return ctx->throwSyntaxError("JSON.parse: Parse error");
     }
 
     return result.asReturnedValue();
diff --git a/src/qml/jsruntime/qv4lookup.cpp b/src/qml/jsruntime/qv4lookup.cpp
index 4ee24d29eb..10c94734d6 100644
--- a/src/qml/jsruntime/qv4lookup.cpp
+++ b/src/qml/jsruntime/qv4lookup.cpp
@@ -97,7 +97,7 @@ ReturnedValue Lookup::getterGeneric(QV4::Lookup *l, const ValueRef object)
     switch (object->type()) {
     case Value::Undefined_Type:
     case Value::Null_Type:
-        engine->current->throwTypeError();
+        return engine->current->throwTypeError();
     case Value::Boolean_Type:
         proto = engine->booleanClass->prototype;
         break;
@@ -439,6 +439,8 @@ void Lookup::setterGeneric(Lookup *l, const ValueRef object, const ValueRef valu
     ScopedObject o(scope, object);
     if (!o) {
         o = __qmljs_convert_to_object(scope.engine->current, object);
+        if (!o) // type error
+            return;
         ScopedString s(scope, l->name);
         o->put(s, value);
         return;
diff --git a/src/qml/jsruntime/qv4managed.cpp b/src/qml/jsruntime/qv4managed.cpp
index 31bb8f2b94..4d40b72bab 100644
--- a/src/qml/jsruntime/qv4managed.cpp
+++ b/src/qml/jsruntime/qv4managed.cpp
@@ -174,23 +174,22 @@ QString Managed::className() const
 
 bool Managed::hasInstance(Managed *m, const ValueRef)
 {
-    m->engine()->current->throwTypeError();
+    return m->engine()->current->throwTypeError();
 }
 
 ReturnedValue Managed::construct(Managed *m, CallData *)
 {
-    m->engine()->current->throwTypeError();
+    return m->engine()->current->throwTypeError();
 }
 
 ReturnedValue Managed::call(Managed *m, CallData *)
 {
-    m->engine()->current->throwTypeError();
+    return m->engine()->current->throwTypeError();
 }
 
 ReturnedValue Managed::getLookup(Managed *m, Lookup *)
 {
-    m->engine()->current->throwTypeError();
-    return 0;
+    return m->engine()->current->throwTypeError();
 }
 
 void Managed::setLookup(Managed *m, Lookup *, const ValueRef)
diff --git a/src/qml/jsruntime/qv4numberobject.cpp b/src/qml/jsruntime/qv4numberobject.cpp
index 8a09de5349..dd13f493f7 100644
--- a/src/qml/jsruntime/qv4numberobject.cpp
+++ b/src/qml/jsruntime/qv4numberobject.cpp
@@ -107,7 +107,7 @@ inline ReturnedValue thisNumberValue(ExecutionContext *ctx)
         return ctx->callData->thisObject.asReturnedValue();
     NumberObject *n = ctx->callData->thisObject.asNumberObject();
     if (!n)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     return n->value.asReturnedValue();
 }
 
@@ -117,21 +117,21 @@ inline double thisNumber(ExecutionContext *ctx)
         return ctx->callData->thisObject.asDouble();
     NumberObject *n = ctx->callData->thisObject.asNumberObject();
     if (!n)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     return n->value.asDouble();
 }
 
 ReturnedValue NumberPrototype::method_toString(SimpleCallContext *ctx)
 {
     double num = thisNumber(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
 
     if (ctx->callData->argc && !ctx->callData->args[0].isUndefined()) {
         int radix = ctx->callData->args[0].toInt32();
-        if (radix < 2 || radix > 36) {
-            ctx->throwError(QString::fromLatin1("Number.prototype.toString: %0 is not a valid radix")
+        if (radix < 2 || radix > 36)
+            return ctx->throwError(QString::fromLatin1("Number.prototype.toString: %0 is not a valid radix")
                             .arg(radix));
-            return Encode::undefined();
-        }
 
         if (std::isnan(num)) {
             return ctx->engine->newString(QStringLiteral("NaN"))->asReturnedValue();
@@ -177,6 +177,8 @@ ReturnedValue NumberPrototype::method_toLocaleString(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedValue v(scope, thisNumberValue(ctx));
+    if (ctx->engine->hasException)
+        return Encode::undefined();
 
     ScopedString str(scope, v->toString(ctx));
     return str.asReturnedValue();
@@ -190,6 +192,8 @@ ReturnedValue NumberPrototype::method_valueOf(SimpleCallContext *ctx)
 ReturnedValue NumberPrototype::method_toFixed(SimpleCallContext *ctx)
 {
     double v = thisNumber(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
 
     double fdigits = 0;
 
@@ -200,7 +204,7 @@ ReturnedValue NumberPrototype::method_toFixed(SimpleCallContext *ctx)
         fdigits = 0;
 
     if (fdigits < 0 || fdigits > 20)
-        ctx->throwRangeError(ctx->callData->thisObject);
+        return ctx->throwRangeError(ctx->callData->thisObject);
 
     QString str;
     if (std::isnan(v))
@@ -218,6 +222,8 @@ ReturnedValue NumberPrototype::method_toExponential(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     double d = thisNumber(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
 
     int fdigits = -1;
 
@@ -225,7 +231,7 @@ ReturnedValue NumberPrototype::method_toExponential(SimpleCallContext *ctx)
         int fdigits = ctx->callData->args[0].toInt32();
         if (fdigits < 0 || fdigits > 20) {
             ScopedString error(scope, ctx->engine->newString(QStringLiteral("Number.prototype.toExponential: fractionDigits out of range")));
-            ctx->throwRangeError(error);
+            return ctx->throwRangeError(error);
         }
     }
 
@@ -241,6 +247,8 @@ ReturnedValue NumberPrototype::method_toPrecision(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedValue v(scope, thisNumberValue(ctx));
+    if (ctx->engine->hasException)
+        return Encode::undefined();
 
     if (!ctx->callData->argc || ctx->callData->args[0].isUndefined())
         return __qmljs_to_string(v, ctx);
@@ -248,7 +256,7 @@ ReturnedValue NumberPrototype::method_toPrecision(SimpleCallContext *ctx)
     double precision = ctx->callData->args[0].toInt32();
     if (precision < 1 || precision > 21) {
         ScopedString error(scope, ctx->engine->newString(QStringLiteral("Number.prototype.toPrecision: precision out of range")));
-        ctx->throwRangeError(error);
+        return ctx->throwRangeError(error);
     }
 
     char str[100];
diff --git a/src/qml/jsruntime/qv4object.cpp b/src/qml/jsruntime/qv4object.cpp
index b04c65196e..ca02d6703a 100644
--- a/src/qml/jsruntime/qv4object.cpp
+++ b/src/qml/jsruntime/qv4object.cpp
@@ -168,7 +168,6 @@ void Object::putValue(Property *pd, PropertyAttributes attrs, const ValueRef val
   reject:
     if (engine()->current->strictMode)
         engine()->current->throwTypeError();
-
 }
 
 void Object::defineDefaultProperty(const StringRef name, ValueRef value)
@@ -715,8 +714,10 @@ void Object::internalPut(const StringRef name, const ValueRef value)
         else if (isArrayObject() && name->equals(engine()->id_length)) {
             bool ok;
             uint l = value->asArrayLength(&ok);
-            if (!ok)
+            if (!ok) {
                 engine()->current->throwRangeError(value);
+                return;
+            }
             ok = setArrayLength(l);
             if (!ok)
                 goto reject;
@@ -914,6 +915,7 @@ bool Object::__defineOwnProperty__(ExecutionContext *ctx, const StringRef name,
             if (!ok) {
                 ScopedValue v(scope, p.value);
                 ctx->throwRangeError(v);
+                return false;
             }
             succeeded = setArrayLength(l);
         }
@@ -1230,8 +1232,10 @@ void Object::arraySort(ExecutionContext *context, ObjectRef thisObject, const Va
         }
     }
 
-    if (!(comparefn->isUndefined() || comparefn->asObject()))
+    if (!(comparefn->isUndefined() || comparefn->asObject())) {
         context->throwTypeError();
+        return;
+    }
 
     ArrayElementLessThan lessThan(context, thisObject, comparefn);
 
diff --git a/src/qml/jsruntime/qv4objectproto.cpp b/src/qml/jsruntime/qv4objectproto.cpp
index 7cfda589e5..061487f8af 100644
--- a/src/qml/jsruntime/qv4objectproto.cpp
+++ b/src/qml/jsruntime/qv4objectproto.cpp
@@ -143,7 +143,7 @@ ReturnedValue ObjectPrototype::method_getPrototypeOf(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<Object> p(scope, o->prototype());
     return !!p ? p->asReturnedValue() : Encode::null();
@@ -154,7 +154,7 @@ ReturnedValue ObjectPrototype::method_getOwnPropertyDescriptor(SimpleCallContext
     Scope scope(ctx);
     Scoped<Object> O(scope, ctx->argument(0));
     if (!O)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedValue v(scope, ctx->argument(1));
     Scoped<String> name(scope, v->toString(ctx));
@@ -168,7 +168,7 @@ ReturnedValue ObjectPrototype::method_getOwnPropertyNames(SimpleCallContext *con
     Scope scope(context);
     ScopedObject O(scope, context->argument(0));
     if (!O)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     ScopedArrayObject array(scope, getOwnPropertyNames(context->engine, context->callData->args[0]));
     return array.asReturnedValue();
@@ -179,7 +179,7 @@ ReturnedValue ObjectPrototype::method_create(SimpleCallContext *ctx)
     Scope scope(ctx);
     ScopedValue O(scope, ctx->argument(0));
     if (!O->isObject() && !O->isNull())
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<Object> newObject(scope, ctx->engine->newObject());
     newObject->setPrototype(O->asObject());
@@ -197,17 +197,21 @@ ReturnedValue ObjectPrototype::method_defineProperty(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> O(scope, ctx->argument(0));
     if (!O)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<String> name(scope, ctx->argument(1), Scoped<String>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     ScopedValue attributes(scope, ctx->argument(2));
     Property pd;
     PropertyAttributes attrs;
     toPropertyDescriptor(ctx, attributes, &pd, &attrs);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     if (!O->__defineOwnProperty__(ctx, name, pd, attrs))
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return O.asReturnedValue();
 }
@@ -217,9 +221,11 @@ ReturnedValue ObjectPrototype::method_defineProperties(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> O(scope, ctx->argument(0));
     if (!O)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<Object> o(scope, ctx->argument(1), Scoped<Object>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
     ScopedValue val(scope);
 
     ObjectIterator it(scope, o, ObjectIterator::EnumerableOnly);
@@ -234,13 +240,15 @@ ReturnedValue ObjectPrototype::method_defineProperties(SimpleCallContext *ctx)
         PropertyAttributes nattrs;
         val = o->getValue(pd, attrs);
         toPropertyDescriptor(ctx, val, &n, &nattrs);
+        if (scope.engine->hasException)
+            return Encode::undefined();
         bool ok;
         if (name)
             ok = O->__defineOwnProperty__(ctx, name, n, nattrs);
         else
             ok = O->__defineOwnProperty__(ctx, index, n, nattrs);
         if (!ok)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
     }
 
     return O.asReturnedValue();
@@ -251,7 +259,7 @@ ReturnedValue ObjectPrototype::method_seal(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     o->extensible = false;
 
@@ -271,7 +279,7 @@ ReturnedValue ObjectPrototype::method_freeze(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     o->extensible = false;
 
@@ -292,7 +300,7 @@ ReturnedValue ObjectPrototype::method_preventExtensions(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     o->extensible = false;
     return o.asReturnedValue();
@@ -303,7 +311,7 @@ ReturnedValue ObjectPrototype::method_isSealed(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (o->extensible)
         return Encode(false);
@@ -331,7 +339,7 @@ ReturnedValue ObjectPrototype::method_isFrozen(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (o->extensible)
         return Encode(false);
@@ -359,7 +367,7 @@ ReturnedValue ObjectPrototype::method_isExtensible(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return Encode((bool)o->extensible);
 }
@@ -369,7 +377,7 @@ ReturnedValue ObjectPrototype::method_keys(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->argument(0));
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<ArrayObject> a(scope, ctx->engine->newArrayObject());
 
@@ -403,9 +411,11 @@ ReturnedValue ObjectPrototype::method_toLocaleString(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedObject o(scope, ctx->callData->thisObject.toObject(ctx));
+    if (!o)
+        return Encode::undefined();
     Scoped<FunctionObject> f(scope, o->get(ctx->engine->id_toString));
     if (!f)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     ScopedCallData callData(scope, 0);
     callData->thisObject = o;
     return f->call(callData);
@@ -415,6 +425,8 @@ ReturnedValue ObjectPrototype::method_valueOf(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     ScopedValue v(scope, ctx->callData->thisObject.toObject(ctx));
+    if (ctx->engine->hasException)
+        return Encode::undefined();
     return v.asReturnedValue();
 }
 
@@ -422,7 +434,11 @@ ReturnedValue ObjectPrototype::method_hasOwnProperty(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     Scoped<String> P(scope, ctx->argument(0), Scoped<String>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
     Scoped<Object> O(scope, ctx->callData->thisObject, Scoped<Object>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
     bool r = O->__getOwnProperty__(P) != 0;
     if (!r)
         r = !O->query(P).isEmpty();
@@ -437,6 +453,8 @@ ReturnedValue ObjectPrototype::method_isPrototypeOf(SimpleCallContext *ctx)
         return Encode(false);
 
     Scoped<Object> O(scope, ctx->callData->thisObject, Scoped<Object>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
     Scoped<Object> proto(scope, V->prototype());
     while (proto) {
         if (O.getPointer() == proto.getPointer())
@@ -450,8 +468,12 @@ ReturnedValue ObjectPrototype::method_propertyIsEnumerable(SimpleCallContext *ct
 {
     Scope scope(ctx);
     Scoped<String> p(scope, ctx->argument(0), Scoped<String>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     Scoped<Object> o(scope, ctx->callData->thisObject, Scoped<Object>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
     PropertyAttributes attrs;
     o->__getOwnProperty__(p, &attrs);
     return Encode(attrs.isEnumerable());
@@ -460,14 +482,16 @@ ReturnedValue ObjectPrototype::method_propertyIsEnumerable(SimpleCallContext *ct
 ReturnedValue ObjectPrototype::method_defineGetter(SimpleCallContext *ctx)
 {
     if (ctx->callData->argc < 2)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scope scope(ctx);
     Scoped<String> prop(scope, ctx->argument(0), Scoped<String>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     Scoped<FunctionObject> f(scope, ctx->argument(1));
     if (!f)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<Object> o(scope, ctx->callData->thisObject);
     if (!o) {
@@ -484,14 +508,16 @@ ReturnedValue ObjectPrototype::method_defineGetter(SimpleCallContext *ctx)
 ReturnedValue ObjectPrototype::method_defineSetter(SimpleCallContext *ctx)
 {
     if (ctx->callData->argc < 2)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scope scope(ctx);
     Scoped<String> prop(scope, ctx->argument(0), Scoped<String>::Convert);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     Scoped<FunctionObject> f(scope, ctx->argument(1));
     if (!f)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     Scoped<Object> o(scope, ctx->callData->thisObject);
     if (!o) {
@@ -510,7 +536,7 @@ ReturnedValue ObjectPrototype::method_get_proto(SimpleCallContext *ctx)
     Scope scope(ctx);
     ScopedObject o(scope, ctx->callData->thisObject.asObject());
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return o->prototype()->asReturnedValue();
 }
@@ -520,7 +546,7 @@ ReturnedValue ObjectPrototype::method_set_proto(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Object> o(scope, ctx->callData->thisObject);
     if (!o || !ctx->callData->argc)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (ctx->callData->args[0].isNull()) {
         o->setPrototype(0);
@@ -537,7 +563,7 @@ ReturnedValue ObjectPrototype::method_set_proto(SimpleCallContext *ctx)
         }
     }
     if (!ok)
-        ctx->throwTypeError(QStringLiteral("Cyclic __proto__ value"));
+        return ctx->throwTypeError(QStringLiteral("Cyclic __proto__ value"));
     return Encode::undefined();
 }
 
@@ -545,8 +571,10 @@ void ObjectPrototype::toPropertyDescriptor(ExecutionContext *ctx, const ValueRef
 {
     Scope scope(ctx);
     ScopedObject o(scope, v);
-    if (!o)
+    if (!o) {
         ctx->throwTypeError();
+        return;
+    }
 
     attrs->clear();
     desc->setGetter(0);
@@ -568,6 +596,7 @@ void ObjectPrototype::toPropertyDescriptor(ExecutionContext *ctx, const ValueRef
             desc->setGetter((FunctionObject *)0x1);
         } else {
             ctx->throwTypeError();
+            return;
         }
         attrs->setType(PropertyAttributes::Accessor);
     }
@@ -581,21 +610,26 @@ void ObjectPrototype::toPropertyDescriptor(ExecutionContext *ctx, const ValueRef
             desc->setSetter((FunctionObject *)0x1);
         } else {
             ctx->throwTypeError();
+            return;
         }
         attrs->setType(PropertyAttributes::Accessor);
     }
 
     if (o->__hasProperty__(ctx->engine->id_writable)) {
-        if (attrs->isAccessor())
+        if (attrs->isAccessor()) {
             ctx->throwTypeError();
+            return;
+        }
         attrs->setWritable((tmp = o->get(ctx->engine->id_writable))->toBoolean());
         // writable forces it to be a data descriptor
         desc->value = Primitive::undefinedValue();
     }
 
     if (o->__hasProperty__(ctx->engine->id_value)) {
-        if (attrs->isAccessor())
+        if (attrs->isAccessor()) {
             ctx->throwTypeError();
+            return;
+        }
         desc->value = o->get(ctx->engine->id_value);
         attrs->setType(PropertyAttributes::Data);
     }
diff --git a/src/qml/jsruntime/qv4qobjectwrapper.cpp b/src/qml/jsruntime/qv4qobjectwrapper.cpp
index 05d5532f8f..a581e6bc69 100644
--- a/src/qml/jsruntime/qv4qobjectwrapper.cpp
+++ b/src/qml/jsruntime/qv4qobjectwrapper.cpp
@@ -436,7 +436,7 @@ bool QObjectWrapper::setQmlProperty(ExecutionContext *ctx, QQmlContextData *qmlC
     if (!result->isWritable() && !result->isQList()) {
         QString error = QLatin1String("Cannot assign to read-only property \"") +
                         name->toQString() + QLatin1Char('\"');
-        ctx->throwTypeError(error);
+        return ctx->throwTypeError(error);
     }
 
     QQmlBinding *newBinding = 0;
@@ -451,6 +451,7 @@ bool QObjectWrapper::setQmlProperty(ExecutionContext *ctx, QQmlContextData *qmlC
                 else
                     error += QLatin1String(QMetaType::typeName(result->propType));
                 ctx->throwError(error);
+                return false;
             }
         } else {
             // binding assignment.
@@ -504,6 +505,7 @@ bool QObjectWrapper::setQmlProperty(ExecutionContext *ctx, QQmlContextData *qmlC
         else
             error += QLatin1String(QMetaType::typeName(result->propType));
         ctx->throwError(error);
+        return false;
     } else if (value->asFunctionObject()) {
         // this is handled by the binding creation above
     } else if (result->propType == QMetaType::Int && value->isNumber()) {
@@ -542,6 +544,7 @@ bool QObjectWrapper::setQmlProperty(ExecutionContext *ctx, QQmlContextData *qmlC
                             QLatin1String(" to ") +
                             QLatin1String(targetTypeName);
             ctx->throwError(error);
+            return false;
         }
     }
 
@@ -1281,7 +1284,7 @@ static QV4::ReturnedValue CallPrecise(QObject *object, const QQmlPropertyData &d
     if (returnType == QMetaType::UnknownType) {
         QString typeName = QString::fromLatin1(unknownTypeError);
         QString error = QString::fromLatin1("Unknown method return type: %1").arg(typeName);
-        QV8Engine::getV4(engine)->current->throwError(error);
+        return QV8Engine::getV4(engine)->current->throwError(error);
     }
 
     if (data.hasArguments()) {
@@ -1295,12 +1298,12 @@ static QV4::ReturnedValue CallPrecise(QObject *object, const QQmlPropertyData &d
         if (!args) {
             QString typeName = QString::fromLatin1(unknownTypeError);
             QString error = QString::fromLatin1("Unknown method parameter type: %1").arg(typeName);
-            QV8Engine::getV4(engine)->current->throwError(error);
+            return QV8Engine::getV4(engine)->current->throwError(error);
         }
 
         if (args[0] > callArgs->argc) {
             QString error = QLatin1String("Insufficient arguments");
-            QV8Engine::getV4(engine)->current->throwError(error);
+            return QV8Engine::getV4(engine)->current->throwError(error);
         }
 
         return CallMethod(object, data.coreIndex, returnType, args[0], args + 1, engine, callArgs);
@@ -1399,7 +1402,7 @@ static QV4::ReturnedValue CallOverloaded(QObject *object, const QQmlPropertyData
             candidate = RelatedMethod(object, candidate, dummy);
         }
 
-        QV8Engine::getV4(engine)->current->throwError(error);
+        return QV8Engine::getV4(engine)->current->throwError(error);
     }
 }
 
@@ -1697,7 +1700,7 @@ QV4::ReturnedValue QObjectMethod::method_destroy(QV4::ExecutionContext *ctx, con
     if (!m_object)
         return Encode::undefined();
     if (QQmlData::keepAliveDuringGarbageCollection(m_object))
-        ctx->throwError(QStringLiteral("Invalid attempt to destroy() an indestructible object"));
+        return ctx->throwError(QStringLiteral("Invalid attempt to destroy() an indestructible object"));
 
     int delay = 0;
     if (argc > 0)
diff --git a/src/qml/jsruntime/qv4regexpobject.cpp b/src/qml/jsruntime/qv4regexpobject.cpp
index 6eaa8c387d..8bcddcce0a 100644
--- a/src/qml/jsruntime/qv4regexpobject.cpp
+++ b/src/qml/jsruntime/qv4regexpobject.cpp
@@ -249,7 +249,7 @@ ReturnedValue RegExpCtor::construct(Managed *m, CallData *callData)
     Scoped<RegExpObject> re(scope, r);
     if (re) {
         if (!f->isUndefined())
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
 
         Scoped<RegExp> newRe(scope, re->value);
         return Encode(ctx->engine->newRegExpObject(newRe, re->global));
@@ -273,14 +273,14 @@ ReturnedValue RegExpCtor::construct(Managed *m, CallData *callData)
             } else if (str.at(i) == QChar('m') && !multiLine) {
                 multiLine = true;
             } else {
-                ctx->throwSyntaxError(0);
+                return ctx->throwSyntaxError(0);
             }
         }
     }
 
     Scoped<RegExp> regexp(scope, RegExp::create(ctx->engine, pattern, ignoreCase, multiLine));
     if (!regexp->isValid())
-        ctx->throwSyntaxError(0);
+        return ctx->throwSyntaxError(0);
 
     return Encode(ctx->engine->newRegExpObject(regexp, global));
 }
@@ -314,7 +314,7 @@ ReturnedValue RegExpPrototype::method_exec(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<RegExpObject> r(scope, ctx->callData->thisObject.as<RegExpObject>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedValue arg(scope, ctx->argument(0));
     arg = __qmljs_to_string(arg, ctx);
@@ -366,7 +366,7 @@ ReturnedValue RegExpPrototype::method_toString(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<RegExpObject> r(scope, ctx->callData->thisObject.as<RegExpObject>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return ctx->engine->newString(r->toString())->asReturnedValue();
 }
@@ -376,7 +376,7 @@ ReturnedValue RegExpPrototype::method_compile(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<RegExpObject> r(scope, ctx->callData->thisObject.as<RegExpObject>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     ScopedCallData callData(scope, ctx->callData->argc);
     memcpy(callData->args, ctx->callData->args, ctx->callData->argc*sizeof(SafeValue));
diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 1eed693c3d..dbbccdea70 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -284,6 +284,8 @@ ReturnedValue __qmljs_delete_member(ExecutionContext *ctx, const ValueRef base,
 {
     Scope scope(ctx);
     ScopedObject obj(scope, base->toObject(ctx));
+    if (scope.engine->hasException)
+        return Encode::undefined();
     return Encode(obj->deleteProperty(name));
 }
 
@@ -315,7 +317,7 @@ QV4::ReturnedValue __qmljs_instanceof(ExecutionContext *ctx, const ValueRef left
 {
     Object *o = right->asObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     bool r = o->hasInstance(left);
     return Encode(r);
@@ -324,9 +326,11 @@ QV4::ReturnedValue __qmljs_instanceof(ExecutionContext *ctx, const ValueRef left
 QV4::ReturnedValue __qmljs_in(ExecutionContext *ctx, const ValueRef left, const ValueRef right)
 {
     if (!right->isObject())
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     Scope scope(ctx);
     ScopedString s(scope, left->toString(ctx));
+    if (scope.hasException())
+        return Encode::undefined();
     bool r = right->objectValue()->__hasProperty__(s);
     return Encode(r);
 }
@@ -382,6 +386,9 @@ ReturnedValue __qmljs_object_default_value(Object *object, int typeHint)
     }
 
     ExecutionEngine *engine = object->internalClass->engine;
+    if (engine->hasException)
+        return Encode::undefined();
+
     SafeString *meth1 = &engine->id_toString;
     SafeString *meth2 = &engine->id_valueOf;
 
@@ -400,6 +407,9 @@ ReturnedValue __qmljs_object_default_value(Object *object, int typeHint)
             return r->asReturnedValue();
     }
 
+    if (engine->hasException)
+        return Encode::undefined();
+
     conv = object->get(*meth2);
     if (FunctionObject *o = conv->asFunctionObject()) {
         ScopedValue r(scope, o->call(callData));
@@ -407,8 +417,7 @@ ReturnedValue __qmljs_object_default_value(Object *object, int typeHint)
             return r->asReturnedValue();
     }
 
-    ctx->throwTypeError();
-    return Encode::undefined();
+    return ctx->throwTypeError();
 }
 
 Bool __qmljs_to_boolean(const ValueRef value)
@@ -424,6 +433,7 @@ Returned<Object> *__qmljs_convert_to_object(ExecutionContext *ctx, const ValueRe
     case Value::Undefined_Type:
     case Value::Null_Type:
         ctx->throwTypeError();
+        return 0;
     case Value::Boolean_Type:
         return ctx->engine->newBooleanObject(value);
     case Value::Managed_Type:
@@ -468,6 +478,8 @@ void __qmljs_set_property(ExecutionContext *ctx, const ValueRef object, const St
 {
     Scope scope(ctx);
     ScopedObject o(scope, object->toObject(ctx));
+    if (scope.engine->hasException)
+        return;
     o->put(name, value);
 }
 
@@ -490,10 +502,12 @@ ReturnedValue __qmljs_get_element(ExecutionContext *ctx, const ValueRef object,
 
         if (object->isNullOrUndefined()) {
             QString message = QStringLiteral("Cannot read property '%1' of %2").arg(index->toQStringNoThrow()).arg(object->toQStringNoThrow());
-            ctx->throwTypeError(message);
+            return ctx->throwTypeError(message);
         }
 
         o = __qmljs_convert_to_object(ctx, object);
+        if (!o) // type error
+            return Encode::undefined();
     }
 
     if (idx < UINT_MAX) {
@@ -509,6 +523,8 @@ ReturnedValue __qmljs_get_element(ExecutionContext *ctx, const ValueRef object,
     }
 
     ScopedString name(scope, index->toString(ctx));
+    if (scope.hasException())
+        return Encode::undefined();
     return o->get(name);
 }
 
@@ -516,6 +532,8 @@ void __qmljs_set_element(ExecutionContext *ctx, const ValueRef object, const Val
 {
     Scope scope(ctx);
     ScopedObject o(scope, object->toObject(ctx));
+    if (scope.engine->hasException)
+        return;
 
     uint idx = index->asArrayIndex();
     if (idx < UINT_MAX) {
@@ -553,6 +571,8 @@ void __qmljs_set_element(ExecutionContext *ctx, const ValueRef object, const Val
     }
 
     ScopedString name(scope, index->toString(ctx));
+    if (scope.hasException())
+        return;
     o->put(name, value);
 }
 
@@ -592,10 +612,12 @@ ReturnedValue __qmljs_get_property(ExecutionContext *ctx, const ValueRef object,
 
     if (object->isNullOrUndefined()) {
         QString message = QStringLiteral("Cannot read property '%1' of %2").arg(name->toQString()).arg(object->toQStringNoThrow());
-        ctx->throwTypeError(message);
+        return ctx->throwTypeError(message);
     }
 
     o = __qmljs_convert_to_object(ctx, object);
+    if (!o) // type error
+        return Encode::undefined();
     return o->get(name);
 }
 
@@ -753,7 +775,7 @@ ReturnedValue __qmljs_call_global_lookup(ExecutionContext *context, uint index,
     Lookup *l = context->lookups + index;
     Scoped<FunctionObject> o(scope, l->globalGetter(l, context));
     if (!o)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     if (o.getPointer() == context->engine->evalFunction && l->name->equals(context->engine->id_eval))
         return static_cast<EvalFunction *>(o.getPointer())->evalCall(callData, true);
@@ -781,7 +803,7 @@ ReturnedValue __qmljs_call_activation_property(ExecutionContext *context, const
         if (base)
             objectAsString = ScopedValue(scope, base.asReturnedValue())->toQStringNoThrow();
         QString msg = QStringLiteral("Property '%1' of object %2 is not a function").arg(name->toQString()).arg(objectAsString);
-        context->throwTypeError(msg);
+        return context->throwTypeError(msg);
     }
 
     if (o == context->engine->evalFunction && name->equals(context->engine->id_eval)) {
@@ -799,17 +821,19 @@ ReturnedValue __qmljs_call_property(ExecutionContext *context, const StringRef n
         Q_ASSERT(!callData->thisObject.isEmpty());
         if (callData->thisObject.isNullOrUndefined()) {
             QString message = QStringLiteral("Cannot call method '%1' of %2").arg(name->toQString()).arg(callData->thisObject.toQStringNoThrow());
-            context->throwTypeError(message);
+            return context->throwTypeError(message);
         }
 
         baseObject = __qmljs_convert_to_object(context, ValueRef(&callData->thisObject));
+        if (!baseObject) // type error
+            return Encode::undefined();
         callData->thisObject = baseObject.asReturnedValue();
     }
 
     Scoped<FunctionObject> o(scope, baseObject->get(name));
     if (!o) {
         QString error = QString("Property '%1' of object %2 is not a function").arg(name->toQString(), callData->thisObject.toQStringNoThrow());
-        context->throwTypeError(error);
+        return context->throwTypeError(error);
     }
 
     return o->call(callData);
@@ -822,7 +846,7 @@ ReturnedValue __qmljs_call_property_lookup(ExecutionContext *context, uint index
     Lookup *l = context->lookups + index;
     Scoped<Object> o(scope, l->getter(l, callData->thisObject));
     if (!o)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return o->call(callData);
 }
@@ -831,12 +855,15 @@ ReturnedValue __qmljs_call_element(ExecutionContext *context, const ValueRef ind
 {
     Scope scope(context);
     ScopedObject baseObject(scope, callData->thisObject.toObject(context));
+    ScopedString s(scope, index->toString(context));
+
+    if (scope.engine->hasException)
+        return Encode::undefined();
     callData->thisObject = baseObject;
 
-    ScopedString s(scope, index->toString(context));
     ScopedObject o(scope, baseObject->get(s));
     if (!o)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return o->call(callData);
 }
@@ -845,7 +872,7 @@ ReturnedValue __qmljs_call_value(ExecutionContext *context, const ValueRef func,
 {
     Object *o = func->asObject();
     if (!o)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return o->call(callData);
 }
@@ -859,7 +886,7 @@ ReturnedValue __qmljs_construct_global_lookup(ExecutionContext *context, uint in
     Lookup *l = context->lookups + index;
     Scoped<Object> f(scope, l->globalGetter(l, context));
     if (!f)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return f->construct(callData);
 }
@@ -874,7 +901,7 @@ ReturnedValue __qmljs_construct_activation_property(ExecutionContext *context, c
 
     Object *f = func->asObject();
     if (!f)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return f->construct(callData);
 }
@@ -883,7 +910,7 @@ ReturnedValue __qmljs_construct_value(ExecutionContext *context, const ValueRef
 {
     Object *f = func->asObject();
     if (!f)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return f->construct(callData);
 }
@@ -892,10 +919,12 @@ ReturnedValue __qmljs_construct_property(ExecutionContext *context, const ValueR
 {
     Scope scope(context);
     ScopedObject thisObject(scope, base->toObject(context));
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     Scoped<Object> f(scope, thisObject->get(name));
     if (!f)
-        context->throwTypeError();
+        return context->throwTypeError();
 
     return f->construct(callData);
 }
@@ -948,6 +977,8 @@ QV4::ReturnedValue __qmljs_builtin_typeof_member(ExecutionContext *context, cons
 {
     Scope scope(context);
     ScopedObject obj(scope, base->toObject(context));
+    if (scope.engine->hasException)
+        return Encode::undefined();
     ScopedValue prop(scope, obj->get(name));
     return __qmljs_builtin_typeof(context, prop);
 }
@@ -957,6 +988,8 @@ QV4::ReturnedValue __qmljs_builtin_typeof_element(ExecutionContext *context, con
     Scope scope(context);
     ScopedString name(scope, index->toString(context));
     ScopedObject obj(scope, base->toObject(context));
+    if (scope.engine->hasException)
+        return Encode::undefined();
     ScopedValue prop(scope, obj->get(name));
     return __qmljs_builtin_typeof(context, prop);
 }
@@ -1097,7 +1130,12 @@ QV4::ReturnedValue __qmljs_to_object(QV4::ExecutionContext *ctx, const QV4::Valu
 {
     if (value->isObject())
         return value.asReturnedValue();
-    return Encode(__qmljs_convert_to_object(ctx, value));
+
+    Returned<Object> *o = __qmljs_convert_to_object(ctx, value);
+    if (!o) // type error
+        return Encode::undefined();
+
+    return Encode(o);
 }
 
 ReturnedValue __qmljs_value_to_double(const ValueRef value)
diff --git a/src/qml/jsruntime/qv4sequenceobject.cpp b/src/qml/jsruntime/qv4sequenceobject.cpp
index 320646805b..f6feb2f170 100644
--- a/src/qml/jsruntime/qv4sequenceobject.cpp
+++ b/src/qml/jsruntime/qv4sequenceobject.cpp
@@ -400,7 +400,7 @@ public:
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlSequence<Container> > This(scope, ctx->callData->thisObject.as<QQmlSequence<Container> >());
         if (!This)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
 
         if (This->m_isReference) {
             if (!This->m_object)
@@ -415,7 +415,7 @@ public:
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlSequence<Container> > This(scope, ctx->callData->thisObject.as<QQmlSequence<Container> >());
         if (!This)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
 
         quint32 newLength = ctx->callData->args[0].toUInt32();
         /* Qt containers have int (rather than uint) allowable indexes. */
@@ -553,7 +553,7 @@ QV4::ReturnedValue SequencePrototype::method_sort(QV4::SimpleCallContext *ctx)
     QV4::Scope scope(ctx);
     QV4::ScopedObject o(scope, ctx->callData->thisObject);
     if (!o || !o->isListType())
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (ctx->callData->argc >= 2)
         return o.asReturnedValue();
diff --git a/src/qml/jsruntime/qv4stringobject.cpp b/src/qml/jsruntime/qv4stringobject.cpp
index 25e1ea55c2..36d1433665 100644
--- a/src/qml/jsruntime/qv4stringobject.cpp
+++ b/src/qml/jsruntime/qv4stringobject.cpp
@@ -124,8 +124,10 @@ bool StringObject::deleteIndexedProperty(Managed *m, uint index)
     ExecutionEngine *v4 = m->engine();
     Scope scope(v4);
     Scoped<StringObject> o(scope, m->asStringObject());
-    if (!o)
+    if (!o) {
         v4->current->throwTypeError();
+        return false;
+    }
 
     if (index < o->value.stringValue()->toQString().length()) {
         if (v4->current->strictMode)
@@ -237,8 +239,10 @@ static QString getThisString(ExecutionContext *ctx)
         return t->stringValue()->toQString();
     if (StringObject *thisString = t->asStringObject())
         return thisString->value.stringValue()->toQString();
-    if (t->isUndefined() || t->isNull())
+    if (t->isUndefined() || t->isNull()) {
         ctx->throwTypeError();
+        return QString();
+    }
     return t->toQString();
 }
 
@@ -249,13 +253,15 @@ ReturnedValue StringPrototype::method_toString(SimpleCallContext *context)
 
     StringObject *o = context->callData->thisObject.asStringObject();
     if (!o)
-        context->throwTypeError();
+        return context->throwTypeError();
     return o->value.asReturnedValue();
 }
 
 ReturnedValue StringPrototype::method_charAt(SimpleCallContext *context)
 {
     const QString str = getThisString(context);
+    if (context->engine->hasException)
+        return Encode::undefined();
 
     int pos = 0;
     if (context->callData->argc > 0)
@@ -271,6 +277,8 @@ ReturnedValue StringPrototype::method_charAt(SimpleCallContext *context)
 ReturnedValue StringPrototype::method_charCodeAt(SimpleCallContext *context)
 {
     const QString str = getThisString(context);
+    if (context->engine->hasException)
+        return Encode::undefined();
 
     int pos = 0;
     if (context->callData->argc > 0)
@@ -288,6 +296,8 @@ ReturnedValue StringPrototype::method_concat(SimpleCallContext *context)
     Scope scope(context);
 
     QString value = getThisString(context);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     ScopedValue v(scope);
     for (int i = 0; i < context->callData->argc; ++i) {
@@ -302,6 +312,8 @@ ReturnedValue StringPrototype::method_concat(SimpleCallContext *context)
 ReturnedValue StringPrototype::method_indexOf(SimpleCallContext *context)
 {
     QString value = getThisString(context);
+    if (context->engine->hasException)
+        return Encode::undefined();
 
     QString searchString;
     if (context->callData->argc)
@@ -323,6 +335,8 @@ ReturnedValue StringPrototype::method_lastIndexOf(SimpleCallContext *context)
     Scope scope(context);
 
     const QString value = getThisString(context);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     QString searchString;
     if (context->callData->argc)
@@ -348,6 +362,9 @@ ReturnedValue StringPrototype::method_localeCompare(SimpleCallContext *context)
 {
     Scope scope(context);
     const QString value = getThisString(context);
+    if (scope.engine->hasException)
+        return Encode::undefined();
+
     ScopedValue v(scope, context->callData->argument(0));
     const QString that = v->toQString();
     return Encode(QString::localeAwareCompare(value, that));
@@ -356,7 +373,7 @@ ReturnedValue StringPrototype::method_localeCompare(SimpleCallContext *context)
 ReturnedValue StringPrototype::method_match(SimpleCallContext *context)
 {
     if (context->callData->thisObject.isUndefined() || context->callData->thisObject.isNull())
-        context->throwTypeError();
+        return context->throwTypeError();
 
     Scope scope(context);
     ScopedString s(scope, context->callData->thisObject.toString(context));
@@ -371,7 +388,7 @@ ReturnedValue StringPrototype::method_match(SimpleCallContext *context)
 
     if (!rx)
         // ### CHECK
-        context->throwTypeError();
+        return context->throwTypeError();
 
     bool global = rx->global;
 
@@ -580,6 +597,8 @@ ReturnedValue StringPrototype::method_search(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     QString string = getThisString(ctx);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     ScopedValue regExpValue(scope, ctx->argument(0));
     Scoped<RegExpObject> regExp(scope, regExpValue->as<RegExpObject>());
@@ -600,6 +619,9 @@ ReturnedValue StringPrototype::method_search(SimpleCallContext *ctx)
 ReturnedValue StringPrototype::method_slice(SimpleCallContext *ctx)
 {
     const QString text = getThisString(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
+
     const double length = text.length();
 
     double start = ctx->callData->argc ? ctx->callData->args[0].toInteger() : 0;
@@ -627,6 +649,8 @@ ReturnedValue StringPrototype::method_split(SimpleCallContext *ctx)
 {
     Scope scope(ctx);
     QString text = getThisString(ctx);
+    if (scope.engine->hasException)
+        return Encode::undefined();
 
     ScopedValue separatorValue(scope, ctx->argument(0));
     ScopedValue limitValue(scope, ctx->argument(1));
@@ -705,6 +729,8 @@ ReturnedValue StringPrototype::method_split(SimpleCallContext *ctx)
 ReturnedValue StringPrototype::method_substr(SimpleCallContext *context)
 {
     const QString value = getThisString(context);
+    if (context->engine->hasException)
+        return Encode::undefined();
 
     double start = 0;
     if (context->callData->argc > 0)
@@ -728,6 +754,8 @@ ReturnedValue StringPrototype::method_substr(SimpleCallContext *context)
 ReturnedValue StringPrototype::method_substring(SimpleCallContext *context)
 {
     QString value = getThisString(context);
+    if (context->engine->hasException)
+        return Encode::undefined();
     int length = value.length();
 
     double start = 0;
@@ -767,6 +795,8 @@ ReturnedValue StringPrototype::method_substring(SimpleCallContext *context)
 ReturnedValue StringPrototype::method_toLowerCase(SimpleCallContext *ctx)
 {
     QString value = getThisString(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
     return ctx->engine->newString(value.toLower())->asReturnedValue();
 }
 
@@ -778,6 +808,8 @@ ReturnedValue StringPrototype::method_toLocaleLowerCase(SimpleCallContext *ctx)
 ReturnedValue StringPrototype::method_toUpperCase(SimpleCallContext *ctx)
 {
     QString value = getThisString(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
     return ctx->engine->newString(value.toUpper())->asReturnedValue();
 }
 
@@ -800,6 +832,8 @@ ReturnedValue StringPrototype::method_fromCharCode(SimpleCallContext *context)
 ReturnedValue StringPrototype::method_trim(SimpleCallContext *ctx)
 {
     QString s = getThisString(ctx);
+    if (ctx->engine->hasException)
+        return Encode::undefined();
 
     const QChar *chars = s.constData();
     int start, end;
diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index 0314e4d2a9..01e87537f5 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -1451,7 +1451,7 @@ QV4::ReturnedValue QmlIncubatorObject::method_get_object(QV4::SimpleCallContext
     QV4::Scope scope(ctx);
     QV4::Scoped<QmlIncubatorObject> o(scope, ctx->callData->thisObject.as<QmlIncubatorObject>());
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return QV4::QObjectWrapper::wrap(ctx->engine, o->incubator->object());
 }
@@ -1461,7 +1461,7 @@ QV4::ReturnedValue QmlIncubatorObject::method_forceCompletion(QV4::SimpleCallCon
     QV4::Scope scope(ctx);
     QV4::Scoped<QmlIncubatorObject> o(scope, ctx->callData->thisObject.as<QmlIncubatorObject>());
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     o->incubator->forceCompletion();
 
@@ -1473,7 +1473,7 @@ QV4::ReturnedValue QmlIncubatorObject::method_get_status(QV4::SimpleCallContext
     QV4::Scope scope(ctx);
     QV4::Scoped<QmlIncubatorObject> o(scope, ctx->callData->thisObject.as<QmlIncubatorObject>());
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return QV4::Encode(o->incubator->status());
 }
@@ -1483,7 +1483,7 @@ QV4::ReturnedValue QmlIncubatorObject::method_get_statusChanged(QV4::SimpleCallC
     QV4::Scope scope(ctx);
     QV4::Scoped<QmlIncubatorObject> o(scope, ctx->callData->thisObject.as<QmlIncubatorObject>());
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return o->m_statusChanged.asReturnedValue();
 }
@@ -1493,7 +1493,7 @@ QV4::ReturnedValue QmlIncubatorObject::method_set_statusChanged(QV4::SimpleCallC
     QV4::Scope scope(ctx);
     QV4::Scoped<QmlIncubatorObject> o(scope, ctx->callData->thisObject.as<QmlIncubatorObject>());
     if (!o || ctx->callData->argc < 1)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
 
     o->m_statusChanged = ctx->callData->args[0];
diff --git a/src/qml/qml/qqmlcontextwrapper.cpp b/src/qml/qml/qqmlcontextwrapper.cpp
index c867b6e126..a187b17a08 100644
--- a/src/qml/qml/qqmlcontextwrapper.cpp
+++ b/src/qml/qml/qqmlcontextwrapper.cpp
@@ -135,7 +135,7 @@ ReturnedValue QmlContextWrapper::get(Managed *m, const StringRef name, bool *has
     QV4::Scope scope(v4);
     QmlContextWrapper *resource = m->as<QmlContextWrapper>();
     if (!resource)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     // In V8 the JS global object would come _before_ the QML global object,
     // so simulate that here.
@@ -282,8 +282,10 @@ void QmlContextWrapper::put(Managed *m, const StringRef name, const ValueRef val
     ExecutionEngine *v4 = m->engine();
     QV4::Scope scope(v4);
     QV4::Scoped<QmlContextWrapper> wrapper(scope, m->as<QmlContextWrapper>());
-    if (!wrapper)
+    if (!wrapper) {
         v4->current->throwTypeError();
+        return;
+    }
 
     if (wrapper->isNullWrapper) {
         if (wrapper && wrapper->readOnly) {
@@ -291,6 +293,7 @@ void QmlContextWrapper::put(Managed *m, const StringRef name, const ValueRef val
                             QLatin1Char('"');
             Scoped<String> e(scope, v4->current->engine->newString(error));
             v4->current->throwError(e);
+            return;
         }
 
         Object::put(m, name, value);
@@ -341,6 +344,7 @@ void QmlContextWrapper::put(Managed *m, const StringRef name, const ValueRef val
         QString error = QLatin1String("Invalid write to global property \"") + name->toQString() +
                         QLatin1Char('"');
         v4->current->throwError(error);
+        return;
     }
 
     Object::put(m, name, value);
diff --git a/src/qml/qml/qqmllistwrapper.cpp b/src/qml/qml/qqmllistwrapper.cpp
index 0364659ecc..12ebc102ee 100644
--- a/src/qml/qml/qqmllistwrapper.cpp
+++ b/src/qml/qml/qqmllistwrapper.cpp
@@ -106,7 +106,7 @@ ReturnedValue QmlListWrapper::get(Managed *m, const StringRef name, bool *hasPro
     QV4::ExecutionEngine *v4 = m->engine();
     QmlListWrapper *w = m->as<QmlListWrapper>();
     if (!w)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     if (name->equals(v4->id_length) && !w->object.isNull()) {
         quint32 count = w->property.count ? w->property.count(&w->property) : 0;
@@ -125,7 +125,7 @@ ReturnedValue QmlListWrapper::getIndexed(Managed *m, uint index, bool *hasProper
     QV4::ExecutionEngine *e = m->engine();
     QmlListWrapper *w = m->as<QmlListWrapper>();
     if (!w)
-        e->current->throwTypeError();
+        return e->current->throwTypeError();
 
     quint32 count = w->property.count ? w->property.count(&w->property) : 0;
     if (index < count && w->property.at)
diff --git a/src/qml/qml/qqmllocale.cpp b/src/qml/qml/qqmllocale.cpp
index aca18d8ef4..81a6ffc590 100644
--- a/src/qml/qml/qqmllocale.cpp
+++ b/src/qml/qml/qqmllocale.cpp
@@ -67,11 +67,13 @@ public:
 
     QLocale locale;
 
-    static QLocale &getThisLocale(QV4::SimpleCallContext *ctx) {
+    static QLocale *getThisLocale(QV4::SimpleCallContext *ctx) {
         QQmlLocaleData *thisObject = ctx->callData->thisObject.asObject()->as<QQmlLocaleData>();
-        if (!thisObject)
+        if (!thisObject) {
             ctx->throwTypeError();
-        return thisObject->locale;
+            return 0;
+        }
+        return &thisObject->locale;
     }
 
     static QV4::ReturnedValue method_currencySymbol(QV4::SimpleCallContext *ctx);
@@ -516,8 +518,10 @@ QV4::ReturnedValue QQmlNumberExtension::method_fromLocaleString(QV4::SimpleCallC
 
 QV4::ReturnedValue QQmlLocaleData::method_get_firstDayOfWeek(QV4::SimpleCallContext *ctx)
 {
-    QLocale locale = getThisLocale(ctx);
-    int fdow = int(locale.firstDayOfWeek());
+    QLocale *locale = getThisLocale(ctx);
+    if (!locale)
+        return QV4::Encode::undefined();
+    int fdow = int(locale->firstDayOfWeek());
     if (fdow == 7)
         fdow = 0; // Qt::Sunday = 7, but Sunday is 0 in JS Date
     return QV4::Encode(fdow);
@@ -525,21 +529,29 @@ QV4::ReturnedValue QQmlLocaleData::method_get_firstDayOfWeek(QV4::SimpleCallCont
 
 QV4::ReturnedValue QQmlLocaleData::method_get_measurementSystem(QV4::SimpleCallContext *ctx)
 {
-    QLocale locale = getThisLocale(ctx);
-    return QV4::Encode(locale.measurementSystem());
+    QLocale *locale = getThisLocale(ctx);
+    if (!locale)
+        return QV4::Encode::undefined();
+    return QV4::Encode(locale->measurementSystem());
 }
 
 QV4::ReturnedValue QQmlLocaleData::method_get_textDirection(QV4::SimpleCallContext *ctx)
 {
-    QLocale locale = getThisLocale(ctx);
-    return QV4::Encode(locale.textDirection());
+    QLocale *locale = getThisLocale(ctx);
+    if (!locale)
+        return QV4::Encode::undefined();
+
+    return QV4::Encode(locale->textDirection());
 }
 
 QV4::ReturnedValue QQmlLocaleData::method_get_weekDays(QV4::SimpleCallContext *ctx)
 {
     QV4::Scope scope(ctx);
-    QLocale locale = getThisLocale(ctx);
-    QList<Qt::DayOfWeek> days = locale.weekdays();
+    QLocale *locale = getThisLocale(ctx);
+    if (!locale)
+        return QV4::Encode::undefined();
+
+    QList<Qt::DayOfWeek> days = locale->weekdays();
 
     QV4::Scoped<QV4::ArrayObject> result(scope, ctx->engine->newArrayObject());
     result->arrayReserve(days.size());
@@ -558,8 +570,11 @@ QV4::ReturnedValue QQmlLocaleData::method_get_weekDays(QV4::SimpleCallContext *c
 QV4::ReturnedValue QQmlLocaleData::method_get_uiLanguages(QV4::SimpleCallContext *ctx)
 {
     QV4::Scope scope(ctx);
-    QLocale locale = getThisLocale(ctx);
-    QStringList langs = locale.uiLanguages();
+    QLocale *locale = getThisLocale(ctx);
+    if (!locale)
+        return QV4::Encode::undefined();
+
+    QStringList langs = locale->uiLanguages();
     QV4::Scoped<QV4::ArrayObject> result(scope, ctx->engine->newArrayObject());
     result->arrayReserve(langs.size());
     for (int i = 0; i < langs.size(); ++i) {
@@ -574,7 +589,10 @@ QV4::ReturnedValue QQmlLocaleData::method_get_uiLanguages(QV4::SimpleCallContext
 
 QV4::ReturnedValue QQmlLocaleData::method_currencySymbol(QV4::SimpleCallContext *ctx)
 {
-    QLocale locale = getThisLocale(ctx);
+    QLocale *locale = getThisLocale(ctx);
+    if (!locale)
+        return QV4::Encode::undefined();
+
     if (ctx->callData->argc > 1)
         V4THROW_ERROR("Locale: currencySymbol(): Invalid arguments");
 
@@ -584,12 +602,14 @@ QV4::ReturnedValue QQmlLocaleData::method_currencySymbol(QV4::SimpleCallContext
         format = QLocale::CurrencySymbolFormat(intFormat);
     }
 
-    return ctx->engine->newString(locale.currencySymbol(format))->asReturnedValue();
+    return ctx->engine->newString(locale->currencySymbol(format))->asReturnedValue();
 }
 
 #define LOCALE_FORMAT(FUNC) \
 QV4::ReturnedValue QQmlLocaleData::method_ ##FUNC (QV4::SimpleCallContext *ctx) { \
-    QLocale locale = getThisLocale(ctx); \
+    QLocale *locale = getThisLocale(ctx); \
+    if (!locale) \
+        return QV4::Encode::undefined(); \
     if (ctx->callData->argc > 1) \
         V4THROW_ERROR("Locale: " #FUNC "(): Invalid arguments"); \
     QLocale::FormatType format = QLocale::LongFormat;\
@@ -597,7 +617,7 @@ QV4::ReturnedValue QQmlLocaleData::method_ ##FUNC (QV4::SimpleCallContext *ctx)
         quint32 intFormat = ctx->callData->args[0].toUInt32(); \
         format = QLocale::FormatType(intFormat); \
     } \
-    return ctx->engine->newString(locale. FUNC (format))->asReturnedValue(); \
+    return ctx->engine->newString(locale-> FUNC (format))->asReturnedValue(); \
 }
 
 LOCALE_FORMAT(dateTimeFormat)
@@ -607,7 +627,9 @@ LOCALE_FORMAT(dateFormat)
 // +1 added to idx because JS is 0-based, whereas QLocale months begin at 1.
 #define LOCALE_FORMATTED_MONTHNAME(VARIABLE) \
 QV4::ReturnedValue QQmlLocaleData::method_ ## VARIABLE (QV4::SimpleCallContext *ctx) {\
-    QLocale locale = getThisLocale(ctx); \
+    QLocale *locale = getThisLocale(ctx); \
+    if (!locale) \
+        return QV4::Encode::undefined(); \
     if (ctx->callData->argc < 1 || ctx->callData->argc > 2) \
         V4THROW_ERROR("Locale: " #VARIABLE "(): Invalid arguments"); \
     QLocale::FormatType enumFormat = QLocale::LongFormat; \
@@ -619,12 +641,12 @@ QV4::ReturnedValue QQmlLocaleData::method_ ## VARIABLE (QV4::SimpleCallContext *
         if (ctx->callData->args[1].isNumber()) { \
             quint32 intFormat = ctx->callData->args[1].toUInt32(); \
             QLocale::FormatType format = QLocale::FormatType(intFormat); \
-            name = locale. VARIABLE(idx, format); \
+            name = locale-> VARIABLE(idx, format); \
         } else { \
             V4THROW_ERROR("Locale: Invalid datetime format"); \
         } \
     } else { \
-        name = locale. VARIABLE(idx, enumFormat); \
+        name = locale-> VARIABLE(idx, enumFormat); \
     } \
     return ctx->engine->newString(name)->asReturnedValue(); \
 }
@@ -632,7 +654,9 @@ QV4::ReturnedValue QQmlLocaleData::method_ ## VARIABLE (QV4::SimpleCallContext *
 // 0 -> 7 as Qt::Sunday is 7, but Sunday is 0 in JS Date
 #define LOCALE_FORMATTED_DAYNAME(VARIABLE) \
 QV4::ReturnedValue QQmlLocaleData::method_ ## VARIABLE (QV4::SimpleCallContext *ctx) {\
-    QLocale locale = getThisLocale(ctx); \
+    QLocale *locale = getThisLocale(ctx); \
+    if (!locale) \
+        return QV4::Encode::undefined(); \
     if (ctx->callData->argc < 1 || ctx->callData->argc > 2) \
         V4THROW_ERROR("Locale: " #VARIABLE "(): Invalid arguments"); \
     QLocale::FormatType enumFormat = QLocale::LongFormat; \
@@ -645,12 +669,12 @@ QV4::ReturnedValue QQmlLocaleData::method_ ## VARIABLE (QV4::SimpleCallContext *
         if (ctx->callData->args[1].isNumber()) { \
             quint32 intFormat = ctx->callData->args[1].toUInt32(); \
             QLocale::FormatType format = QLocale::FormatType(intFormat); \
-            name = locale. VARIABLE(idx, format); \
+            name = locale-> VARIABLE(idx, format); \
         } else { \
             V4THROW_ERROR("Locale: Invalid datetime format"); \
         } \
     } else { \
-        name = locale. VARIABLE(idx, enumFormat); \
+        name = locale-> VARIABLE(idx, enumFormat); \
     } \
     return ctx->engine->newString(name)->asReturnedValue(); \
 }
@@ -662,8 +686,10 @@ LOCALE_FORMATTED_DAYNAME(standaloneDayName)
 
 #define LOCALE_STRING_PROPERTY(VARIABLE) QV4::ReturnedValue QQmlLocaleData::method_get_ ## VARIABLE (QV4::SimpleCallContext* ctx) \
 { \
-    QLocale locale = getThisLocale(ctx); \
-    return ctx->engine->newString(locale. VARIABLE())->asReturnedValue();\
+    QLocale *locale = getThisLocale(ctx); \
+    if (!locale) \
+        return QV4::Encode::undefined(); \
+    return ctx->engine->newString(locale-> VARIABLE())->asReturnedValue();\
 }
 
 LOCALE_STRING_PROPERTY(name)
diff --git a/src/qml/qml/qqmltypewrapper.cpp b/src/qml/qml/qqmltypewrapper.cpp
index de2386daf1..ca53d1a53d 100644
--- a/src/qml/qml/qqmltypewrapper.cpp
+++ b/src/qml/qml/qqmltypewrapper.cpp
@@ -121,7 +121,7 @@ ReturnedValue QmlTypeWrapper::get(Managed *m, const StringRef name, bool *hasPro
 
     Scoped<QmlTypeWrapper> w(scope,  m->as<QmlTypeWrapper>());
     if (!w)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
 
     if (hasProperty)
@@ -229,8 +229,10 @@ void QmlTypeWrapper::put(Managed *m, const StringRef name, const ValueRef value)
 {
     QmlTypeWrapper *w = m->as<QmlTypeWrapper>();
     QV4::ExecutionEngine *v4 = m->engine();
-    if (!w)
+    if (!w) {
         v4->current->throwTypeError();
+        return;
+    }
 
     QV4::Scope scope(v4);
     QV8Engine *v8engine = v4->v8Engine;
@@ -255,6 +257,7 @@ void QmlTypeWrapper::put(Managed *m, const StringRef name, const ValueRef value)
             if (!apiprivate) {
                 QString error = QLatin1String("Cannot assign to read-only property \"") + name->toQString() + QLatin1Char('\"');
                 v4->current->throwError(error);
+                return;
             } else {
                 apiprivate->put(name, value);
             }
diff --git a/src/qml/qml/qqmlvaluetypewrapper.cpp b/src/qml/qml/qqmlvaluetypewrapper.cpp
index 6477f63daf..e892fb2c0c 100644
--- a/src/qml/qml/qqmlvaluetypewrapper.cpp
+++ b/src/qml/qml/qqmlvaluetypewrapper.cpp
@@ -208,8 +208,10 @@ PropertyAttributes QmlValueTypeWrapper::query(const Managed *m, StringRef name)
 {
     const QmlValueTypeWrapper *r = m->as<const QmlValueTypeWrapper>();
     QV4::ExecutionEngine *v4 = m->engine();
-    if (!r)
+    if (!r) {
         v4->current->throwTypeError();
+        return PropertyAttributes();
+    }
 
     QQmlPropertyData local;
     QQmlPropertyData *result = 0;
@@ -246,10 +248,10 @@ ReturnedValue QmlValueTypeWrapper::method_toString(SimpleCallContext *ctx)
 {
     Object *o = ctx->callData->thisObject.asObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     QmlValueTypeWrapper *w = o->as<QmlValueTypeWrapper>();
     if (!w)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (w->objectType == QmlValueTypeWrapper::Reference) {
         QmlValueTypeReference *reference = static_cast<QmlValueTypeReference *>(w);
@@ -271,7 +273,7 @@ ReturnedValue QmlValueTypeWrapper::get(Managed *m, const StringRef name, bool *h
     QmlValueTypeWrapper *r = m->as<QmlValueTypeWrapper>();
     QV4::ExecutionEngine *v4 = m->engine();
     if (!r)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     // Note: readReferenceValue() can change the reference->type.
     if (r->objectType == QmlValueTypeWrapper::Reference) {
@@ -333,8 +335,10 @@ void QmlValueTypeWrapper::put(Managed *m, const StringRef name, const ValueRef v
     ExecutionEngine *v4 = m->engine();
     Scope scope(v4);
     Scoped<QmlValueTypeWrapper> r(scope, m->as<QmlValueTypeWrapper>());
-    if (!r)
+    if (!r) {
         v4->current->throwTypeError();
+        return;
+    }
 
     QByteArray propName = name->toQString().toUtf8();
     if (r->objectType == QmlValueTypeWrapper::Reference) {
@@ -359,6 +363,7 @@ void QmlValueTypeWrapper::put(Managed *m, const StringRef name, const ValueRef v
                 QString error = QLatin1String("Cannot assign JavaScript function to value-type property");
                 Scoped<String> e(scope, r->v8->toString(error));
                 v4->current->throwError(e);
+                return;
             }
 
             QQmlContextData *context = r->v8->callingContext();
diff --git a/src/qml/qml/qqmlxmlhttprequest.cpp b/src/qml/qml/qqmlxmlhttprequest.cpp
index 8445b58430..e0666a1a57 100644
--- a/src/qml/qml/qqmlxmlhttprequest.cpp
+++ b/src/qml/qml/qqmlxmlhttprequest.cpp
@@ -422,7 +422,7 @@ ReturnedValue NodePrototype::method_get_nodeName(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QString name;
     switch (r->d->type) {
@@ -447,7 +447,7 @@ ReturnedValue NodePrototype::method_get_nodeValue(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (r->d->type == NodeImpl::Document ||
         r->d->type == NodeImpl::DocumentFragment ||
@@ -466,7 +466,7 @@ ReturnedValue NodePrototype::method_get_nodeType(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     return Encode(r->d->type);
 }
@@ -476,7 +476,7 @@ ReturnedValue NodePrototype::method_get_parentNode(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -491,7 +491,7 @@ ReturnedValue NodePrototype::method_get_childNodes(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -503,7 +503,7 @@ ReturnedValue NodePrototype::method_get_firstChild(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -518,7 +518,7 @@ ReturnedValue NodePrototype::method_get_lastChild(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -533,7 +533,7 @@ ReturnedValue NodePrototype::method_get_previousSibling(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -557,7 +557,7 @@ ReturnedValue NodePrototype::method_get_nextSibling(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -581,7 +581,7 @@ ReturnedValue NodePrototype::method_get_attributes(SimpleCallContext *ctx)
     Scope scope(ctx);
     Scoped<Node> r(scope, ctx->callData->thisObject.as<Node>());
     if (!r)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     QV8Engine *engine = ctx->engine->v8Engine;
 
@@ -907,7 +907,7 @@ ReturnedValue NamedNodeMap::getIndexed(Managed *m, uint index, bool *hasProperty
     QV4::ExecutionEngine *v4 = m->engine();
     NamedNodeMap *r = m->as<NamedNodeMap>();
     if (!r)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     QV8Engine *engine = v4->v8Engine;
 
@@ -926,7 +926,7 @@ ReturnedValue NamedNodeMap::get(Managed *m, const StringRef name, bool *hasPrope
     NamedNodeMap *r = m->as<NamedNodeMap>();
     QV4::ExecutionEngine *v4 = m->engine();
     if (!r)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     name->makeIdentifier();
     if (name->equals(v4->id_length))
@@ -962,7 +962,7 @@ ReturnedValue NodeList::getIndexed(Managed *m, uint index, bool *hasProperty)
     QV4::ExecutionEngine *v4 = m->engine();
     NodeList *r = m->as<NodeList>();
     if (!r)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     QV8Engine *engine = v4->v8Engine;
 
@@ -981,7 +981,7 @@ ReturnedValue NodeList::get(Managed *m, const StringRef name, bool *hasProperty)
     QV4::ExecutionEngine *v4 = m->engine();
     NodeList *r = m->as<NodeList>();
     if (!r)
-        v4->current->throwTypeError();
+        return v4->current->throwTypeError();
 
     name->makeIdentifier();
 
@@ -1540,13 +1540,17 @@ void QQmlXMLHttpRequest::dispatchCallback(const ValueRef me)
     QV4::Scope scope(v4);
     try {
         Scoped<Object> o(scope, me);
-        if (!o)
+        if (!o) {
             ctx->throwError(QStringLiteral("QQmlXMLHttpRequest: internal error: empty ThisObject"));
+            return;
+        }
 
         ScopedString s(scope, v4->newString(QStringLiteral("ThisObject")));
         Scoped<Object> thisObj(scope, o->get(s));
-        if (!thisObj)
+        if (!thisObj) {
             ctx->throwError(QStringLiteral("QQmlXMLHttpRequest: internal error: empty ThisObject"));
+            return;
+        }
 
         s = v4->newString(QStringLiteral("onreadystatechange"));
         Scoped<FunctionObject> callback(scope, thisObj->get(s));
@@ -1557,8 +1561,10 @@ void QQmlXMLHttpRequest::dispatchCallback(const ValueRef me)
 
         s = v4->newString(QStringLiteral("ActivationObject"));
         Scoped<Object> activationObject(scope, o->get(s));
-        if (!activationObject)
+        if (!activationObject) {
             v4->current->throwError(QStringLiteral("QQmlXMLHttpRequest: internal error: empty ActivationObject"));
+            return;
+        }
 
         QQmlContextData *callingContext = QmlContextWrapper::getContext(activationObject);
         if (callingContext) {
@@ -1645,7 +1651,7 @@ struct QQmlXMLHttpRequestCtor : public FunctionObject
         Scope scope(that->engine());
         Scoped<QQmlXMLHttpRequestCtor> ctor(scope, that->as<QQmlXMLHttpRequestCtor>());
         if (!ctor)
-            that->engine()->current->throwTypeError();
+            return that->engine()->current->throwTypeError();
 
         QV8Engine *engine = that->engine()->v8Engine;
         QQmlXMLHttpRequest *r = new QQmlXMLHttpRequest(engine, engine->networkAccessManager());
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
index f9aca08d5a..047faabd1a 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
@@ -1012,8 +1012,7 @@ ReturnedValue QtObject::method_createQmlObject(SimpleCallContext *ctx)
 
     if (component.isError()) {
         ScopedValue v(scope, Error::create(ctx->engine, component.errors()));
-        ctx->throwError(v);
-        return QV4::Encode::undefined();
+        return ctx->throwError(v);
     }
 
     if (!component.isReady())
@@ -1037,8 +1036,7 @@ ReturnedValue QtObject::method_createQmlObject(SimpleCallContext *ctx)
 
     if (component.isError()) {
         ScopedValue v(scope, Error::create(ctx->engine, component.errors()));
-        ctx->throwError(v);
-        return QV4::Encode::undefined();
+        return ctx->throwError(v);
     }
 
     Q_ASSERT(obj);
@@ -1080,7 +1078,7 @@ use \l{QtQml::Qt::createQmlObject()}{Qt.createQmlObject()}.
 ReturnedValue QtObject::method_createComponent(SimpleCallContext *ctx)
 {
     if (ctx->callData->argc < 1 || ctx->callData->argc > 3)
-        ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid arguments"));
+        return ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid arguments"));
 
     Scope scope(ctx);
 
@@ -1108,13 +1106,13 @@ ReturnedValue QtObject::method_createComponent(SimpleCallContext *ctx)
         if (ctx->callData->args[1].isInteger()) {
             int mode = ctx->callData->args[1].integerValue();
             if (mode != int(QQmlComponent::PreferSynchronous) && mode != int(QQmlComponent::Asynchronous))
-                ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid arguments"));
+                return ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid arguments"));
             compileMode = QQmlComponent::CompilationMode(mode);
             consumedCount += 1;
         } else {
             // The second argument could be the parent only if there are exactly two args
             if ((ctx->callData->argc != 2) || !(lastArg->isObject() || lastArg->isNull()))
-                ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid arguments"));
+                return ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid arguments"));
         }
 
         if (consumedCount < ctx->callData->argc) {
@@ -1123,11 +1121,11 @@ ReturnedValue QtObject::method_createComponent(SimpleCallContext *ctx)
                 if (qobjectWrapper)
                     parentArg = qobjectWrapper->object();
                 if (!parentArg)
-                    ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid parent object"));
+                    return ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid parent object"));
             } else if (lastArg->isNull()) {
                 parentArg = 0;
             } else {
-                ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid parent object"));
+                return ctx->throwError(QStringLiteral("Qt.createComponent(): Invalid parent object"));
             }
         }
     }
@@ -1272,10 +1270,10 @@ ReturnedValue QtObject::method_get_platform(SimpleCallContext *ctx)
     // ### inefficient. Should be just a value based getter
     Object *o = ctx->callData->thisObject.asObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     QtObject *qt = o->as<QtObject>();
     if (!qt)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (!qt->m_platform)
         // Only allocate a platform object once
@@ -1289,10 +1287,10 @@ ReturnedValue QtObject::method_get_application(SimpleCallContext *ctx)
     // ### inefficient. Should be just a value based getter
     Object *o = ctx->callData->thisObject.asObject();
     if (!o)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
     QtObject *qt = o->as<QtObject>();
     if (!qt)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (!qt->m_application)
         // Only allocate an application object once
diff --git a/src/qml/qml/v8/qv4domerrors_p.h b/src/qml/qml/v8/qv4domerrors_p.h
index 44662e8cba..faf52ce1ad 100644
--- a/src/qml/qml/v8/qv4domerrors_p.h
+++ b/src/qml/qml/v8/qv4domerrors_p.h
@@ -80,7 +80,7 @@ QT_BEGIN_NAMESPACE
     QV4::ScopedValue v(scope, ctx->engine->newString(QStringLiteral(string))); \
     QV4::Scoped<Object> ex(scope, ctx->engine->newErrorObject(v)); \
     ex->put(QV4::ScopedString(scope, ctx->engine->newIdentifier(QStringLiteral("code"))), QV4::ScopedValue(scope, QV4::Primitive::fromInt32(error))); \
-    ctx->throwError(ex); \
+    return ctx->throwError(ex); \
 }
 
 namespace QV4 {
diff --git a/src/qml/qml/v8/qv8engine_p.h b/src/qml/qml/v8/qv8engine_p.h
index a92d03ac50..e37b0d4920 100644
--- a/src/qml/qml/v8/qv8engine_p.h
+++ b/src/qml/qml/v8/qv8engine_p.h
@@ -86,10 +86,10 @@ namespace QV4 {
 // #define QML_GLOBAL_HANDLE_DEBUGGING
 
 #define V4THROW_ERROR(string) \
-    ctx->throwError(QString::fromUtf8(string));
+    return ctx->throwError(QString::fromUtf8(string));
 
 #define V4THROW_TYPE(string) \
-    ctx->throwTypeError(QStringLiteral(string));
+    return ctx->throwTypeError(QStringLiteral(string));
 
 #define V8_DEFINE_EXTENSION(dataclass, datafunction) \
     static inline dataclass *datafunction(QV8Engine *engine) \
diff --git a/src/qml/types/qqmldelegatemodel.cpp b/src/qml/types/qqmldelegatemodel.cpp
index 10f957ab40..a1163f0a98 100644
--- a/src/qml/types/qqmldelegatemodel.cpp
+++ b/src/qml/types/qqmldelegatemodel.cpp
@@ -76,8 +76,7 @@ struct DelegateModelGroupFunction: QV4::FunctionObject
 
     static QV4::ReturnedValue construct(QV4::Managed *m, QV4::CallData *)
     {
-        m->engine()->current->throwTypeError();
-        return QV4::Primitive::undefinedValue().asReturnedValue();
+        return m->engine()->current->throwTypeError();
     }
 
     static QV4::ReturnedValue call(QV4::Managed *that, QV4::CallData *callData)
@@ -87,7 +86,7 @@ struct DelegateModelGroupFunction: QV4::FunctionObject
         QV4::Scoped<DelegateModelGroupFunction> f(scope, that, QV4::Scoped<DelegateModelGroupFunction>::Cast);
         QV4::Scoped<QQmlDelegateModelItemObject> o(scope, callData->thisObject);
         if (!o)
-            v4->current->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+            return v4->current->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
         QV4::ScopedValue v(scope, callData->argument(0));
         return f->code(o->item, f->flag, v);
@@ -1711,7 +1710,7 @@ QV4::ReturnedValue QQmlDelegateModelItem::get_model(QV4::SimpleCallContext *ctx)
     QV4::Scope scope(ctx);
     QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
     if (!o)
-        ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+        return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
     if (!o->item->metaType->model)
         return QV4::Encode::undefined();
 
@@ -1723,7 +1722,7 @@ QV4::ReturnedValue QQmlDelegateModelItem::get_groups(QV4::SimpleCallContext *ctx
     QV4::Scope scope(ctx);
     QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
     if (!o)
-        ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+        return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
     QStringList groups;
     for (int i = 1; i < o->item->metaType->groupCount; ++i) {
@@ -1739,9 +1738,9 @@ QV4::ReturnedValue QQmlDelegateModelItem::set_groups(QV4::SimpleCallContext *ctx
     QV4::Scope scope(ctx);
     QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
     if (!o)
-        ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+        return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
     if (!ctx->callData->argc)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (!o->item->metaType->model)
         return QV4::Encode::undefined();
@@ -3153,21 +3152,21 @@ struct QQmlDelegateModelGroupChange : QV4::Object
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlDelegateModelGroupChange> that(scope, ctx->callData->thisObject.as<QQmlDelegateModelGroupChange>());
         if (!that)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
         return QV4::Encode(that->change.index);
     }
     static QV4::ReturnedValue method_get_count(QV4::SimpleCallContext *ctx) {
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlDelegateModelGroupChange> that(scope, ctx->callData->thisObject.as<QQmlDelegateModelGroupChange>());
         if (!that)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
         return QV4::Encode(that->change.count);
     }
     static QV4::ReturnedValue method_get_moveId(QV4::SimpleCallContext *ctx) {
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlDelegateModelGroupChange> that(scope, ctx->callData->thisObject.as<QQmlDelegateModelGroupChange>());
         if (!that)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
         if (that->change.moveId < 0)
             return QV4::Encode::undefined();
         return QV4::Encode(that->change.moveId);
@@ -3199,7 +3198,7 @@ public:
         QV4::Scope scope(v4);
         QV4::Scoped<QQmlDelegateModelGroupChangeArray> array(scope, m->as<QQmlDelegateModelGroupChangeArray>());
         if (!array)
-            v4->current->throwTypeError();
+            return v4->current->throwTypeError();
 
         if (index >= array->count()) {
             if (hasProperty)
@@ -3223,7 +3222,7 @@ public:
     {
         QQmlDelegateModelGroupChangeArray *array = m->as<QQmlDelegateModelGroupChangeArray>();
         if (!array)
-            m->engine()->current->throwTypeError();
+            return m->engine()->current->throwTypeError();
 
         if (name->equals(m->engine()->id_length)) {
             if (hasProperty)
diff --git a/src/qml/util/qqmladaptormodel.cpp b/src/qml/util/qqmladaptormodel.cpp
index 39ebd6bd4c..e8efd46039 100644
--- a/src/qml/util/qqmladaptormodel.cpp
+++ b/src/qml/util/qqmladaptormodel.cpp
@@ -68,7 +68,7 @@ static QV4::ReturnedValue get_index(QV4::SimpleCallContext *ctx)
     QV4::Scope scope(ctx);
     QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
     if (!o)
-        ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+        return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
     return QV4::Encode(o->item->index);
 }
@@ -200,7 +200,7 @@ public:
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
         if (!o)
-            ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+            return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
         const QQmlAdaptorModel *const model = static_cast<QQmlDMCachedModelData *>(o->item)->type->model;
         if (o->item->index >= 0 && *model) {
@@ -344,7 +344,7 @@ QV4::ReturnedValue QQmlDMCachedModelData::get_property(QV4::SimpleCallContext *c
     QV4::Scope scope(ctx);
     QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
     if (!o)
-        ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+        return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
     QQmlDMCachedModelData *modelData = static_cast<QQmlDMCachedModelData *>(o->item);
     if (o->item->index == -1) {
@@ -364,9 +364,9 @@ QV4::ReturnedValue QQmlDMCachedModelData::set_property(QV4::SimpleCallContext *c
     QV4::Scope scope(ctx);
     QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
     if (!o)
-        ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+        return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
     if (!ctx->callData->argc)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     if (o->item->index == -1) {
         QQmlDMCachedModelData *modelData = static_cast<QQmlDMCachedModelData *>(o->item);
@@ -584,7 +584,7 @@ public:
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
         if (!o)
-            ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+            return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
 
         return ctx->engine->v8Engine->fromVariant(static_cast<QQmlDMListAccessorData *>(o->item)->cachedData);
     }
@@ -594,9 +594,9 @@ public:
         QV4::Scope scope(ctx);
         QV4::Scoped<QQmlDelegateModelItemObject> o(scope, ctx->callData->thisObject.as<QQmlDelegateModelItemObject>());
         if (!o)
-            ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
+            return ctx->throwTypeError(QStringLiteral("Not a valid VisualData object"));
         if (!ctx->callData->argc)
-            ctx->throwTypeError();
+            return ctx->throwTypeError();
 
         static_cast<QQmlDMListAccessorData *>(o->item)->setModelData(ctx->engine->v8Engine->toVariant(ctx->callData->args[0], QVariant::Invalid));
         return QV4::Encode::undefined();