Refactored PathTracer in heap.cc....

src/heap.h

Index: src/heap.h
===================================================================
--- src/heap.h	(revision 6875)
+++ src/heap.h	(working copy)
@@ -30,6 +30,8 @@
 
 #include <math.h>
 
+#include "globals.h"
+#include "list.h"
 #include "spaces.h"
 #include "splay-tree-inl.h"
 #include "v8-counters.h"
@@ -2152,6 +2154,65 @@
 };
 
 
+#if defined(DEBUG) || defined(LIVE_OBJECT_LIST)
+// Helper class for tracing paths to a search target Object from all roots.
+// The TracePathFrom() method can be used to trace paths from a specific
+// object to the search target object.
+class PathTracer : public ObjectVisitor {
+ public:
+  enum WhatToFind {

[Søren Thygesen Gjesse, 2011/02/22 08:13:24]

Going forward we should try to use names if the for kXxxYyy, however as we are
not at all consistent this is OK for now.

+    FIND_ALL,   // Will find all matches.
+    FIND_FIRST  // Will stop the search after first match.
+  };
+
+  // For the WhatToFind arg, if FIND_FIRST is specified, tracing will stop
+  // after the first match.  If FIND_ALL is specified, then tracing will be
+  // done for all matches.
+  PathTracer(Object* search_target,
+             WhatToFind what_to_find,
+             VisitMode visit_mode)
+      : search_target_(search_target),
+        found_target_(false),
+        found_target_in_trace_(false),
+        what_to_find_(what_to_find),
+        visit_mode_(visit_mode),
+        object_stack_(20),
+        no_alloc() {}
+
+  virtual void VisitPointers(Object** start, Object** end);
+
+  void Reset();
+  void TracePathFrom(Object** root);
+
+  bool found() const { return found_target_; }
+
+  static Object* const kAnyGlobalObject;
+
+ protected:
+  class MarkVisitor;
+  class UnmarkVisitor;
+
+  void MarkRecursively(Object** p, MarkVisitor* mark_visitor);
+  void UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor);
+  virtual void ProcessResults();
+
+  // Tags 0, 1, and 3 are used. Use 2 for marking visited HeapObject.
+  static const int kMarkTag = 2;
+
+  Object* search_target_;
+  bool found_target_;
+  bool found_target_in_trace_;
+  WhatToFind what_to_find_;
+  VisitMode visit_mode_;
+  List<Object*> object_stack_;
+
+  AssertNoAllocation no_alloc;  // i.e. no gc allowed.
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
+};
+#endif  // DEBUG || LIVE_OBJECT_LIST
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_