Due to complaints about the classic stylings of my initial header name, you now need to include mozilla/HoldDropJSObjects.h rather than nsCycleCollectionHoldDrop.h for these templates.
----- Original Message ----- > 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 > _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
