Fix memory leak caused by treating Code::next_code_link as strong in marker.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 198ab36c5090c7d17661cc8a395056b19ce99bec..ec0c9198517964c17ccafe67bb43831a085c2b8c 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -305,6 +305,7 @@ enum MarkingParity {
   EVEN_MARKING_PARITY
 };
 
+
 // ICs store extra state in a Code object. The default extra state is
 // kNoExtraICState.
 typedef int ExtraICState;
@@ -10685,6 +10686,13 @@ class VisitorSynchronization : public AllStatic {
   static const char* const kTagNames[kNumberOfSyncTags];
 };
 
+
+enum WeakPointerMode {

[Michael Starzinger, 2014/03/04 12:31:12]

As discussed offline: I am not a particular fan of having this mode, because it
assumes that all visitors either visit _all_ or _none_ weak pointers and I am
not sure this hold in general.

Alternatively I would suggest having a special visitor method (e.g.
VisitCodeNextPointer) that the concrete visitor can override to handle this slot
specially. This could be applied to both, the virtual as well as the static
visitor I think.

[ulan, 2014/03/06 11:13:32]

Done. Thanks for suggestion, it is cleaner indeed.

+  VISIT_WEAK_POINTERS,
+  SKIP_WEAK_POINTERS
+};
+
+
 // Abstract base class for visiting, and optionally modifying, the
 // pointers contained in Objects. Used in GC and serialization/deserialization.
 class ObjectVisitor BASE_EMBEDDED {
@@ -10742,6 +10750,8 @@ class ObjectVisitor BASE_EMBEDDED {
   // check for the presence of, a tag at this position in the stream.
   // Also used for marking up GC roots in heap snapshots.
   virtual void Synchronize(VisitorSynchronization::SyncTag tag) {}
+
+  virtual WeakPointerMode weak_pointer_mode() { return VISIT_WEAK_POINTERS; }
 };