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>

1 files changed, 10 insertions, 5 deletions

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();