Improved, safer handling of the symbol table. The symbols themselves...

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 138 matching lines @@
 
   static void MarkUnmarkedObject(HeapObject* obj);
 
   static inline void MarkObject(HeapObject* obj) {
     if (!obj->IsMarked()) MarkUnmarkedObject(obj);
   }
 
   static inline void SetMark(HeapObject* obj) {
     tracer_->increment_marked_count();
 #ifdef DEBUG
     UpdateLiveObjectCount(obj, 1);

[Kasper Lund, 2009/05/05 05:22:34]

Do you need the scale argument to UpdateLiveObjectCount anymore?

[Kevin Millikin (Chromium), 2009/05/05 05:34:07]

No, you're right.  I'll revert it when we clean this all up.

 #endif
     obj->SetMark();
   }
 
-  // Used to clear mark bits during marking for objects that are not
-  // actually live.  Since it updates bookkeeping state, it is not
-  // used when clearing mark bits on live objects (eg, during
-  // sweeping).
-  static inline void ClearMark(HeapObject* obj) {
-    obj->ClearMark();
-    tracer_->decrement_marked_count();
-#ifdef DEBUG
-    UpdateLiveObjectCount(obj, -1);
-#endif
-  }
-
   // Creates back pointers for all map transitions, stores them in
   // the prototype field.  The original prototype pointers are restored
   // in ClearNonLiveTransitions().  All JSObject maps
   // connected by map transitions have the same prototype object, which
   // is why we can use this field temporarily for back pointers.
   static void CreateBackPointers();
 
   // Mark a Map and its DescriptorArray together, skipping transitions.
   static void MarkMapContents(Map* map);
   static void MarkDescriptorArray(DescriptorArray* descriptors);
 
   // Mark the heap roots and all objects reachable from them.
-  static void ProcessRoots(RootMarkingVisitor* visitor);
+  static void MarkRoots(RootMarkingVisitor* visitor);
+
+  // Mark the symbol table specially.  References to symbols are weak.

[iposva, 2009/05/05 05:05:19]

Please clarify: References to symbols from the symbol table are weak.

+  static void MarkSymbolTable();
 
   // Mark objects in object groups that have at least one object in the
   // group marked.
   static void MarkObjectGroups();
 
   // Mark all objects in an object group with at least one marked
   // object, then all objects reachable from marked objects in object
   // groups, and repeat.
   static void ProcessObjectGroups(MarkingVisitor* visitor);
 
@@ skipping 215 matching lines @@
 
   friend class UnmarkObjectVisitor;
   static void UnmarkObject(HeapObject* obj);
 #endif
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_