ES5.2 var semantics: take hidden prototypes into account.

src/runtime.cc

 // Copyright 2012 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 1291 matching lines @@
     // <expr>" the initial value is the hole.
     bool is_var = value->IsUndefined();
     bool is_const = value->IsTheHole();
     bool is_function = value->IsSharedFunctionInfo();
     bool is_module = value->IsJSModule();
     ASSERT(is_var + is_const + is_function + is_module == 1);
 
     if (is_var || is_const) {
       // Lookup the property in the global object, and don't set the
       // value of the variable if the property is already there.
-      // Do the lookup locally only, see ES5 errata.
+      // Do the lookup locally only, see ES5 erratum.
       LookupResult lookup(isolate);
-      if (FLAG_es52_globals)
-        global->LocalLookup(*name, &lookup);
-      else
+      if (FLAG_es52_globals) {
+        Object* obj = *global;
+        do {
+          JSObject::cast(obj)->LocalLookup(*name, &lookup);
+          obj = obj->GetPrototype();
+        } while (!lookup.IsFound() && obj->IsJSObject() &&

[Michael Starzinger, 2012/06/14 13:16:28]

Can we move the "lookup.IsFound()" condition into the loop before getting the
prototype? That would be cleaner IMHO ...

if (lookup.isFound()) break;

[arv (Not doing code reviews), 2012/06/20 19:34:14]

Also, there is no reason to get the prototype if lookup.IsFound() is true.

Maybe the compiler is smart enough to realize that but why take that risk?

+                 JSObject::cast(obj)->map()->is_hidden_prototype());
+      } else {
         global->Lookup(*name, &lookup);
+      }
       if (lookup.IsProperty()) {
         // We found an existing property. Unless it was an interceptor
         // that claims the property is absent, skip this declaration.
         if (lookup.type() != INTERCEPTOR) continue;
         PropertyAttributes attributes = global->GetPropertyAttribute(*name);
         if (attributes != ABSENT) continue;
         // Fall-through and introduce the absent property by using
         // SetProperty.
       }
     } else if (is_function) {
@@ skipping 12236 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal