Global nsICycleCollector service: Difference between revisions

Global nsICycleCollector service (view source)

1,300 bytes added , 24 February 2006

37

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 * [http://venge.net/graydon/mozilla/nsIClassInfo2.idl nsIClassInfo2.idl]
 * [http://venge.net/graydon/mozilla/nsCycleCollector.cpp nsCycleCollector.cpp]
+* [http://venge.net/graydon/mozilla/nsISupportsImpl.h nsISupportsImpl.h changes]
+Some notes on the implementation:
+* The implementation requires that each participating XPCOM class implement <tt>nsIClassInfo2</tt>. The two methods on this interface must be correct: it is better '''not''' to implement <tt>nsIClassInfo2</tt> than to implement it wrong.
+** <tt>unlink(obj)</tt> should disconnect all outgoing XPCOM references held by <tt>obj</tt>.
+** <tt>traverse(obj,refcount,childcount,children)</tt> should return the refcount for <tt>obj</tt>, as well as the count and an array of outgoing XPCOM references from <tt>obj</tt>.
+* An object implementing <tt>nsIClassInfo2</tt> should also use the <tt>NS_IMPL_CYCLE_COLLECTING_*</tt> macros in the <tt>nsISupportsImpl</tt> header; these implementations hook the appropriate refcount operations to communicate with the global cycle collector.
+* The implementation commandeers a single bit from the refcount stored in <tt>nsAutoRefCnt</tt>. This is not strictly necessary, but should cut down significantly on pointless traffic to the cycle collector.
+* The global cycle collector service is kept as a singleton pointer in <tt>nsAutoRefCnt</tt>. This poses potential problems during shutdown. Advice on how to handle this safely would be appreciated.