Make sure that we don't actually overwrite a property that has failed access ...

src/v8natives.js

 // Copyright 2006-2008 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 473 matching lines @@
 PropertyDescriptor.prototype.getSet = function() {
   return this.set_;
 }
 
 
 PropertyDescriptor.prototype.hasSetter = function() {
   return this.hasSetter_;
 }
 
 
+// Converts an array returned from Runtime_GetOwnProperty to an actual
+// property descriptor. For a description of the array layout please
+// see the runtime.cc file.
+function ConvertDescriptorArrayToDescriptor(desc_array) {

[antonm, 2011/02/04 11:41:33]

maybe you want to add something like assert(desc_array !== false) (in the form
if (desc_array === false) throw 'Internal error: invalid desc_array)

[Rico, 2011/02/04 12:14:18]

Done.

+  if (IS_UNDEFINED(desc_array)) {
+    return void 0;
+  }
 
-// ES5 section 8.12.1.
-function GetOwnProperty(obj, p) {
   var desc = new PropertyDescriptor();
-
-  // GetOwnProperty returns an array indexed by the constants
-  // defined in macros.py.
-  // If p is not a property on obj undefined is returned.
-  var props = %GetOwnProperty(ToObject(obj), ToString(p));
-
-  if (IS_UNDEFINED(props)) return void 0;
-
-  // This is an accessor
-  if (props[IS_ACCESSOR_INDEX]) {
-    desc.setGet(props[GETTER_INDEX]);
-    desc.setSet(props[SETTER_INDEX]);
+  // This is an accessor.
+  if (desc_array[IS_ACCESSOR_INDEX]) {
+    desc.setGet(desc_array[GETTER_INDEX]);
+    desc.setSet(desc_array[SETTER_INDEX]);
   } else {
-    desc.setValue(props[VALUE_INDEX]);
-    desc.setWritable(props[WRITABLE_INDEX]);
+    desc.setValue(desc_array[VALUE_INDEX]);
+    desc.setWritable(desc_array[WRITABLE_INDEX]);
   }
-  desc.setEnumerable(props[ENUMERABLE_INDEX]);
-  desc.setConfigurable(props[CONFIGURABLE_INDEX]);
+  desc.setEnumerable(desc_array[ENUMERABLE_INDEX]);
+  desc.setConfigurable(desc_array[CONFIGURABLE_INDEX]);
 
   return desc;
 }
 
 
 // ES5 section 8.12.2.
 function GetProperty(obj, p) {
   var prop = GetOwnProperty(obj);
   if (!IS_UNDEFINED(prop)) return prop;
   var proto = obj.__proto__;
   if (IS_NULL(proto)) return void 0;
   return GetProperty(proto, p);
 }
 
 
 // ES5 section 8.12.6
 function HasProperty(obj, p) {
   var desc = GetProperty(obj, p);
   return IS_UNDEFINED(desc) ? false : true;
 }
 
 
+// ES5 section 8.12.1.
+function GetOwnProperty(obj, p) {
+  // GetOwnProperty returns an array indexed by the constants
+  // defined in macros.py.
+  // If p is not a property on obj undefined is returned.

[antonm, 2011/02/04 11:41:33]

you might want to clarify what returned false means

[Rico, 2011/02/04 12:14:18]

Done.

+  var props = %GetOwnProperty(ToObject(obj), ToString(p));
+
+  if (props == false) return void 0;
+
+  return ConvertDescriptorArrayToDescriptor(props);
+}
+
+
 // ES5 8.12.9.
 function DefineOwnProperty(obj, p, desc, should_throw) {
-  var current = GetOwnProperty(obj, p);
+  var current_or_access = %GetOwnProperty(ToObject(obj), ToString(p));
+  if (current_or_access == false) return void 0;

[antonm, 2011/02/04 11:41:33]

===?

[Rico, 2011/02/04 12:14:18]

No, this will not return true on the return value (because we return the wrapper
boolean)

+
+  var current = ConvertDescriptorArrayToDescriptor(current_or_access);
   var extensible = %IsExtensible(ToObject(obj));
 
   // Error handling according to spec.
   // Step 3
   if (IS_UNDEFINED(current) && !extensible)
     throw MakeTypeError("define_disallowed", ["defineProperty"]);
 
   if (!IS_UNDEFINED(current)) {
     // Step 5 and 6
     if ((IsGenericDescriptor(desc) ||
@@ skipping 653 matching lines @@
 // ----------------------------------------------------------------------------
 
 function SetupFunction() {
   InstallFunctions($Function.prototype, DONT_ENUM, $Array(
     "bind", FunctionBind,
     "toString", FunctionToString
   ));
 }
 
 SetupFunction();