Hi Allen,
Allen Bierbaum wrote:
> I propose that we use boost::shared_ptrs and OSG::RefPtr's to make the
> user-level API's of OpenSG 2.0 safer to use. More specifically I
> suggest that we:
>
> - Make create for non-fc types return boost::shared_ptr<>'s and that we
> traffic in these ptrs in the user API.
> - Merge the capabilities of RefPtr into whatever FCPtr class becomes the
> final standard
> - All user-level APIs would return and take smart pointer style
> arguments that would automatically handle memory management
>
> This change would be extensive, but once it is done I think the system
> would be much better off for it.
>
That was the basic idea I've been expecting to do anyway, once we have
decided whether to get rid of the FCptr hierarchy or not.
> So, let's talk about reasons that it can't or shouldn't be done and how
> we can work around them.
>
> - Performance: We don't want to give up performance. During traversals
> and other highly recursive calls, fcptr's will be passed as arguments
> many times. We don't want each of these times to require a add/sub ref
> because those calls are expensive.
>
> A solution to this problem would be to allow the internal APIs to pass
> around cptr's to maintain high-performance. I haven't looked at the
> code yet so can someone else tell me if this would work?
>
I'm all for it.
> - Cycles: There may be places in the code where we need back references.
>
> Boost solves this by using a weak_ptr. Weak_ptrs are factory objects
> that can create shared_ptr's but will return a Null ptr if the object it
> points to has been destroyed (no shared_ptrs still holding it). We
> could probably create a similar ptr type WeakRefPtr to work for the
> RefPtr types. We could base the implementation off of the
> implementation that boost uses for shared_ptr and weak_ptr.
>
> Comments, concerns, flames? :)
>
Where would we encounter those. The obvious one I can think of are
parent pointers. I think using weak_ptr for the parent pointers should
work. This would horribly break existing applications that use cptrs,
but they would have to change anyway. I can't think of any other cases
that have cycles in them right now. Am I missing something?
Dirk
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