Reference counted containers prototype

[deadalnix]

Le 26/12/2011 18:25, Andrei Alexandrescu a écrit :
> Hello,
>
>
> I've been playing with a new approach to reference counting, in
> particular for the containers library.
>
> A small prototype is at http://pastebin.com/WnSQY1Jw. The prototype
> features a simple doubly-linked list implementation DListImpl. That is
> not supposed to be manipulated directly (or it might, in case the user
> wants a simple garbage collected implementation - this is a point in the
> discussion).
>
> DListImpl has only a couple of primitives implemented. The only
> interesting points that it tries to make are:
>
> (a) the presence of the dispose() primitive, which deallocates all
> memory and brings the object back to its .init state
>
> (b) the presence of the dup() primitive, which creates a full-blown
> duplicate of the object.
>
> The interesting part of the sample is RefImpl, which has a couple of
> quite interesting details:
>
> (a) All interaction with the held object is done via opDispatch. In fact
> opDispatch can be engineered to statically enforce no reference to the
> held object escapes.
>
> (b) A const/immutable call against a non-existing is silently converted
> into a call against a default-initialized object.
>
> (c) If a call works and returns the same type for a non-const and a
> const object, then the const version is preferred. This is to reduce the
> number of calls to ensureUnique().
>
> Destroy.
>
> Andrei

The first thing that I see looking at the source code is how many null 
check you'll find in RefCounted . As the RefCounted struct is useless 
without a payload, we should ensure that the payload exists, in all 
cases, and not null check at every operation.