In bug 883920, I converted these two macros into more contemporary templates.
What was NS_HOLD_JS_OBJECTS(this, nsFoo); or nsContentUtils::HoldJSObjects(this, NS_CYCLE_COLLECTION_PARTICIPANT(nsFoo)); can now just be mozilla::HoldJSObjects(this); What was NS_DROP_JS_OBJECTS(this, nsFoo); or nsContentUtils::DropJSObjects(this); can now just be mozilla::DropJSObjects(this); Both cases, nsISupports and otherwise, are now handled with a template. In addition to being more convenient, these new templates are safer, because in the nsISupports case they do automatically whatever QIing is needed in certain uncommon cases. The header for these new templates is nsCycleCollectionHoldDrop.h. nsContentUtils.h no longer has these functions. HoldJSObjects adds the cycle collected argument to a hash table. These objects are traced during GC and CC to look for JS pointers. DropJSObjects removes the object from the table, so you don't want to call it until you know that it isn't holding onto anything. Generally speaking, you want to do a Hold in the constructor, or at least when you store something into a raw JS pointer your C++ object is holding. It is a good idea to not call DropJSObjects until the destructor, to avoid various weird cases which can lead to critical security problems. It is okay to Hold an object multiple times, or Drop it if it hasn't be held, so play it safe. Find me on IRC (:mccr8) or email me if you have any questions about these changes, or anything else about tracing of C++ objects. Andrew _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
