Make sure to initialize all fields in the special maps...

src/heap.cc

 // Copyright 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 1167 matching lines @@
 Object* Heap::AllocatePartialMap(InstanceType instance_type,
                                  int instance_size) {
   Object* result = AllocateRawMap();
   if (result->IsFailure()) return result;
 
   // Map::cast cannot be used due to uninitialized map field.
   reinterpret_cast<Map*>(result)->set_map(raw_unchecked_meta_map());
   reinterpret_cast<Map*>(result)->set_instance_type(instance_type);
   reinterpret_cast<Map*>(result)->set_instance_size(instance_size);
   reinterpret_cast<Map*>(result)->set_inobject_properties(0);
+  reinterpret_cast<Map*>(result)->set_pre_allocated_property_fields(0);
   reinterpret_cast<Map*>(result)->set_unused_property_fields(0);
+  reinterpret_cast<Map*>(result)->set_bit_field(0);
+  reinterpret_cast<Map*>(result)->set_bit_field2(0);

[Rico, 2010/01/28 08:14:48]

After adding the extensible property to bit_field2 maybe this needs to be (same
as in AllocateMap):
map->set_bit_field2(1 << Map::kIsExtensible);
(default value for extensible is true)

   return result;
 }
 
 
 Object* Heap::AllocateMap(InstanceType instance_type, int instance_size) {
   Object* result = AllocateRawMap();
   if (result->IsFailure()) return result;
 
   Map* map = reinterpret_cast<Map*>(result);
   map->set_map(meta_map());
@@ skipping 3013 matching lines @@
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 List<Object*> ExternalStringTable::new_space_strings_;
 List<Object*> ExternalStringTable::old_space_strings_;
 
 } }  // namespace v8::internal