In our previous episode, Sven Barth said: > No, not multiple roots. If a class is declared as refcounted (and it's > parent class is not) then a hidden field is inserted into its list of > fields, just as a normal one would, only that it isn't accesible using > the "."-operator (because it won't have a valid Pascal identifier). The > compiler of course knows the offset at compile time and at runtime the > field can be accessed using the class' RTTI which would have a > "RefCountOffset" field added (if that offset is < 0 then the object does > not support reference counting).
So in summary: the compiler must pass the fieldoffset to the runtime helper, instead of having one refcounted root with known offset. > Did anyone till now really complain about the performance impact of > reference counting on interfaces? Especially since they are used *so* > much in today's OOP designs? I never really benchmarked it. I never use interfaces in my own abstract data structure designs, mostly because the existing classes don't, and I don't like the refcount. (since i usually also need to access the classes as normal instances) I did benchmark interfaces in combination with variants as part of a decal evaluation. That was, euh, painful. > > function Test: TObject; > begin > Result := (TTestClass.Create as IInterface) as TTestClass; > end; Hmm. This looks like a (Delphi) faq item to me, how to convert interface back to a class. Usually the answer is IComponentreference (or what it is called), if this is legal, I wonder why it didn't come up before. _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
