Index: src/global-handles.h |
diff --git a/src/global-handles.h b/src/global-handles.h |
index a06cba0856487f625be72721819fb1342341e46a..aacdcbc072d0ae26af7ce6264767d8366ee17f7a 100644 |
--- a/src/global-handles.h |
+++ b/src/global-handles.h |
@@ -112,15 +112,24 @@ class GlobalHandles { |
typedef WeakCallbackData<v8::Value, void>::Callback WeakCallback; |
+ // For a phantom weak reference, the callback does not have access to the |
+ // dying object. Phantom weak references are preferred because they allow |
+ // memory to be reclaimed in one GC cycle rather than two. However, for |
+ // historical reasons the default is non-phantom. |
+ enum PhantomState { Nonphantom, Phantom }; |
+ |
// Make the global handle weak and set the callback parameter for the |
// handle. When the garbage collector recognizes that only weak global |
- // handles point to an object the handles are cleared and the callback |
- // function is invoked (for each handle) with the handle and corresponding |
- // parameter as arguments. Note: cleared means set to Smi::FromInt(0). The |
- // reason is that Smi::FromInt(0) does not change during garage collection. |
- static void MakeWeak(Object** location, |
- void* parameter, |
- WeakCallback weak_callback); |
+ // handles point to an object the callback function is invoked (for each |
+ // handle) with the handle and corresponding parameter as arguments. By |
+ // default the handle still contains a pointer to the object that is being |
+ // collected. For this reason the object is not collected until the next |
+ // GC. For a phantom weak handle the handle is cleared (set to a Smi) |
+ // before the callback is invoked, but the handle can still be identified |
+ // in the callback by using the location() of the handle. |
+ static void MakeWeak(Object** location, void* parameter, |
+ WeakCallback weak_callback, |
+ PhantomState phantom = Nonphantom); |
void RecordStats(HeapStats* stats); |