Fix issue 965.

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 597 matching lines @@
     flag |= DONT_DELETE;
 
   if (IsDataDescriptor(desc) || IsGenericDescriptor(desc)) {
     if (desc.hasWritable()) {
       flag |= desc.isWritable() ? 0 : READ_ONLY;
     } else if (!IS_UNDEFINED(current)) {
       flag |= current.isWritable() ? 0 : READ_ONLY;
     } else {
       flag |= READ_ONLY;
     }
-    %DefineOrRedefineDataProperty(obj, p, desc.getValue(), flag);
+    var value =

[Rico, 2010/12/10 10:42:35]

Maybe add a comment that states that this actually works even when no existing
value is present (since it defaults to undefined) - even when this is an
accessor.

[Kevin Millikin (Chromium), 2010/12/10 11:08:23]

I would actually suggest writing it just like the rest of the code in this
function: if (desc.hasValue()) { ... } else if (!IS_UNDEFINED(current)) { ... }
else { ... }.  There's no need for such a comment if you make the code clear and
explicit instead.  (It's especially surprising because it differs from all the
surrounding code, forcing the reader to think about it).

We will also generate slightly better code for IS_UNDEFINED(current) than using
conversion to boolean to test if it's undefined, so there's no reason to be
cryptic.

[Lasse Reichstein, 2010/12/10 11:21:45]

Changed to:
 var value;  // Default value is undefined.
    if (desc.hasValue()) {
      value = desc.getValue();
    } else if (!IS_UNDEFINED(current)) {
      value = current.getValue();
    }

[Kevin Millikin (Chromium), 2010/12/10 11:28:20]

I still think that's too cute.  This is a long function.  If someone writes "var
value = 0" somewhere above won't this break?

[Lasse Reichstein, 2010/12/10 11:37:51]

True, good point.
I'll make a new CL and make it 
 var value = void 0;

+        desc.hasValue() ? desc.getValue() : (current && current.getValue());
+    %DefineOrRedefineDataProperty(obj, p, value, flag);
   } else {
     if (desc.hasGetter() && IS_FUNCTION(desc.getGet())) {
        %DefineOrRedefineAccessorProperty(obj, p, GETTER, desc.getGet(), flag);
     }
     if (desc.hasSetter() && IS_FUNCTION(desc.getSet())) {
       %DefineOrRedefineAccessorProperty(obj, p, SETTER, desc.getSet(), flag);
     }
   }
   return true;
 }
@@ skipping 558 matching lines @@
 // ----------------------------------------------------------------------------
 
 function SetupFunction() {
   InstallFunctions($Function.prototype, DONT_ENUM, $Array(
     "bind", FunctionBind,
     "toString", FunctionToString
   ));
 }
 
 SetupFunction();