Make global variable initialization consistent with Firefox and Safari...

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 751 matching lines @@
   bool assign = args.length() == 2;
 
   CONVERT_ARG_CHECKED(String, name, 0);
   GlobalObject* global = Top::context()->global();
 
   // According to ECMA-262, section 12.2, page 62, the property must
   // not be deletable.
   PropertyAttributes attributes = DONT_DELETE;
 
   // Lookup the property locally in the global object. If it isn't
-  // there, we add the property and take special precautions to always
-  // add it as a local property even in case of callbacks in the
-  // prototype chain (this rules out using SetProperty).
-  // We have IgnoreAttributesAndSetLocalProperty for this.
+  // there, there is a property with this name in the prototype chain.
+  // We follow Safari and Firefox behavior and only set the property
+  // locally if there is an explicit initialization value that we have
+  // to assign to the property. When adding the property we take
+  // special precautions to always add it as a local property even in
+  // case of callbacks in the prototype chain (this rules out using
+  // SetProperty).  We have IgnoreAttributesAndSetLocalProperty for
+  // this.
   LookupResult lookup;
   global->LocalLookup(*name, &lookup);
   if (!lookup.IsProperty()) {
-    Object* value = (assign) ? args[1] : Heap::undefined_value();
-    return global->IgnoreAttributesAndSetLocalProperty(*name,
-                                                       value,
-                                                       attributes);
+    if (assign) {
+      return global->IgnoreAttributesAndSetLocalProperty(*name,
+                                                         args[1],
+                                                         attributes);
+    }
+    return Heap::undefined_value();
   }
 
   // Determine if this is a redeclaration of something read-only.
   if (lookup.IsReadOnly()) {
     return ThrowRedeclarationError("const", name);
   }
 
   // Determine if this is a redeclaration of an intercepted read-only
   // property and figure out if the property exists at all.
   bool found = true;
@@ skipping 6743 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();
   }
 }
 
 
 } }  // namespace v8::internal