Prototype of mark-and-compact support for Harmony weak maps.

src/mark-compact.h

 // 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 311 matching lines @@
   // compacting or not, because the large object space is never compacted.
   void SweepLargeObjectSpace();
 
   // Test whether a (possibly marked) object is a Map.
   static inline bool SafeIsMap(HeapObject* object);
 
   // Map transitions from a live map to a dead map must be killed.
   // We replace them with a null descriptor, with the same key.
   void ClearNonLiveTransitions();
 
+  // Mark all values associated with reachable keys in weak maps encountered
+  // so far.  This might push new object or even new weak maps onto the
+  // marking stack.
+  void ProcessWeakMaps();
+
+  // After all reachable objects have been marked those weak map entries
+  // with an unreachable key are removed from all encountered weak maps.
+  // The linked list of all encountered weak maps is destroyed.
+  void ClearWeakMaps();
+
   // -----------------------------------------------------------------------
   // Phase 2: Sweeping to clear mark bits and free non-live objects for
   // a non-compacting collection, or else computing and encoding
   // forwarding addresses for a compacting collection.
   //
   //  Before: Live objects are marked and non-live objects are unmarked.
   //
   //   After: (Non-compacting collection.)  Live objects are unmarked,
   //          non-live regions have been added to their space's free
   //          list.
@@ skipping 159 matching lines @@
   CodeFlusher* code_flusher_;
 
   friend class Heap;
   friend class OverflowedObjectsScanner;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_