Throw an exception when wrong arguments are passed into SwapElements.

src/runtime.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7759 matching lines @@
     return array->length();
   }
 }
 
 
 static Object* Runtime_SwapElements(Arguments args) {
   HandleScope handle_scope;
 
   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);
+  if (!Array::IndexFromObject(*key1, &index1)
+      || !Array::IndexFromObject(*key2, &index2)) {
+    return Top::ThrowIllegalOperation();
+  }
 
-    SetElement(jsobject, index1, tmp2);
-    SetElement(jsobject, index2, tmp1);
-  } else {
-    Handle<Object> tmp1 = GetProperty(object, key1);
-    Handle<Object> tmp2 = GetProperty(object, key2);
+  Handle<JSObject> jsobject = Handle<JSObject>::cast(object);
+  Handle<Object> tmp1 = GetElement(jsobject, index1);
+  Handle<Object> tmp2 = GetElement(jsobject, index2);
 
-    SetProperty(object, key1, tmp2, NONE);
-    SetProperty(object, key2, tmp1, NONE);
-  }
+  SetElement(jsobject, index1, tmp2);
+  SetElement(jsobject, index2, tmp1);
 
   return Heap::undefined_value();
 }
 
 
 // Returns an array that tells you where in the [0, length) interval an array
 // might have elements.  Can either return keys or intervals.  Keys can have
 // gaps in (undefined).  Intervals can also span over some undefined keys.
 static Object* Runtime_GetArrayKeys(Arguments args) {
   ASSERT(args.length() == 2);
@@ skipping 2458 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal