DIP74: Reference Counted Class Objects

[Andrei Alexandrescu via Digitalmars-d]

On 2/27/15 1:09 AM, ted wrote:
> Andrei Alexandrescu wrote:
>
>> http://wiki.dlang.org/DIP74 got to reviewable form. Please destroy and
>> discuss.
>>
>> Thanks,
>>
>> Andrei
>
> Trivial typos:
>
> struct, class, and closure types that have RCO members accommodate calls to
> Release during their destruction.
> s/Release/opRelease/
>
> Explicit casting to of from void* does not entail a call to opAddRef.
> s/of/or/
>
> also: s/opReleasecalls/opRelease calls/
>
> The examples in "Defining a reference counted object with deallocation",
> and "defining a type that owns resources" both define '_refs', and
> manipulate 'refs'.

Fixed, thanks!

> This is probably a really stupid question, but how does the 'new' work for
> an RCO. I assume it uses the GC memory allocation system, but must mark it
> as 'not for collection' (or similar), for the GC.free() call to work (as
> used in the examples).

DIP74 does not prescribe specific allocation techniques. They are left 
to the user.

One nice point of the design space would be to use the GC for allocation 
and early deallocation, in such a way that the GC is still able to 
collect cycles.

> Probably another silly question: How would the examples work with
> const/immutable (using examples in howtos)?
> e.g. const Widget a = new Widget;
>       auto b = a;	<-- mutable method Widget.opAddRef is not callable
> using a const object

This is tricky. I meant to discuss it; for now I planted a TODO.


Andrei