Use WeakCell to handle the script wrapper cache

src/serialize.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
@@ skipping 2000 matching lines @@
   CHECK(!heap_object->IsHashTable());
 
   SerializeHeapObject(heap_object, how_to_code, where_to_point);
 }
 
 
 void CodeSerializer::SerializeHeapObject(HeapObject* heap_object,
                                          HowToCode how_to_code,
                                          WhereToPoint where_to_point) {
   if (heap_object->IsScript()) {
-    // The wrapper cache uses a Foreign object to point to a global handle.
-    // However, the object visitor expects foreign objects to point to external
-    // references.  Clear the cache to avoid this issue.
-    Script::cast(heap_object)->ClearWrapperCache();
+    // The wrapper cache uses a WeakCell.  However it's not clear what
+    // the semantics of WeakCell are when serializing.  For now we just
+    // clear the cache.
+    HeapObject* clear = heap_object->GetHeap()->undefined_value();

[ulan, 2014/10/14 15:45:56]

Since we rebuild the WeakCell list on every GC, serialization should work
correctly.

+    Script::cast(heap_object)->set_wrapper(clear);

[ulan, 2014/10/14 15:45:56]

Should we also isolate->counters()->script_wrappers()->Decrement() ?

   }
 
   if (FLAG_trace_code_serializer) {
     PrintF("Encoding heap object: ");
     heap_object->ShortPrint();
     PrintF("\n");
   }
 
   // Object has not yet been serialized.  Serialize it here.
   ObjectSerializer serializer(this, heap_object, sink_, how_to_code,
@@ skipping 154 matching lines @@
 
 int SerializedCodeData::CheckSum(String* string) {
   int checksum = Version::Hash();
 #ifdef DEBUG
   uint32_t seed = static_cast<uint32_t>(checksum);
   checksum = static_cast<int>(IteratingStringHasher::Hash(string, seed));
 #endif  // DEBUG
   return checksum;
 }
 } }  // namespace v8::internal