Throw an exception when wrong arguments are passed into SwapElements.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 242d2ccbe483b1387155fbcef04d5e2a3c9081d3..823889aced4b952183c336d3319fc43e27edf68e 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -7777,29 +7777,23 @@ static Object* Runtime_SwapElements(Arguments args) {
 
   ASSERT_EQ(3, args.length());
 
-  Handle<Object> object = args.at<Object>(0);
+  CONVERT_ARG_CHECKED(JSObject, object, 0);
   Handle<Object> key1 = args.at<Object>(1);

[Lasse Reichstein, 2010/05/06 09:03:47]

Consider using CONVERT_ARG_CHECKED for the remaining two arguments too. It's
(slightly) more efficient than creating a new handle, since it creates a handle
that is backed by the argument on the stack instead of a HandleScope entry.

[antonm, 2010/05/06 16:40:16]

Lasse, any chances you meant some other macro:

   65 #define CONVERT_ARG_CHECKED(Type, name, index)                       \    
                                                                                
                                                                                
           
   66   RUNTIME_ASSERT(args[index]->Is##Type());                           \
   67   Handle<Type> name = args.at<Type>(index);

?

[Lasse Reichstein, 2010/05/07 07:02:03]

No, that's the one. See the definition of Arguments::at in arguments.h. It
returns a Handle with a location_ that points directly to the argument on the
stack, instead of allocating a new handle location from the HandleScope.

[antonm, 2010/05/07 10:06:01]

Sorry, I use Handle<Object> key1 = arg.at<Object>(1) which looks exactly like
the thing the macro would do, so I cannot spot the difference.

[Lasse Reichstein, 2010/05/07 11:44:01]

Whoops, my bad. Didn't read your rhs' properly (too used to seeing args[1]).

You could still use the macro, but only for consistency.

   Handle<Object> key2 = args.at<Object>(2);
 
   uint32_t index1, index2;
-  // That must be the most common case.
-  if (object->IsJSObject()
-      && Array::IndexFromObject(*key1, &index1)
-      && Array::IndexFromObject(*key2, &index2)) {
-    Handle<JSObject> jsobject = Handle<JSObject>::cast(object);
-    Handle<Object> tmp1 = GetElement(jsobject, index1);
-    Handle<Object> tmp2 = GetElement(jsobject, index2);
-
-    SetElement(jsobject, index1, tmp2);
-    SetElement(jsobject, index2, tmp1);
-  } else {
-    Handle<Object> tmp1 = GetProperty(object, key1);
-    Handle<Object> tmp2 = GetProperty(object, key2);
-
-    SetProperty(object, key1, tmp2, NONE);
-    SetProperty(object, key2, tmp1, NONE);
+  if (!Array::IndexFromObject(*key1, &index1)
+      || !Array::IndexFromObject(*key2, &index2)) {
+    return Top::ThrowIllegalOperation();
   }
 
+  Handle<JSObject> jsobject = Handle<JSObject>::cast(object);
+  Handle<Object> tmp1 = GetElement(jsobject, index1);
+  Handle<Object> tmp2 = GetElement(jsobject, index2);
+
+  SetElement(jsobject, index1, tmp2);
+  SetElement(jsobject, index2, tmp1);
+
   return Heap::undefined_value();
 }