DIP74 - where is at?

[Andrei Alexandrescu via Digitalmars-d]

On 10/11/15 10:16 AM, Jonathan M Davis wrote:
> On Sunday, 11 October 2015 at 06:55:50 UTC, Manu wrote:
>> On 11 October 2015 at 14:35, Jonathan M Davis via Digitalmars-d
>> <digitalmars-d at puremagic.com> wrote:
>>> On Sunday, 11 October 2015 at 04:16:11 UTC, deadalnix wrote:
>>>>
>>>> If we go these DIP road, there is no coming back and this will get
>>>> in the way of a principled approach.
>>>
>>>
>>> Then come up with an alternative DIP which shows a better way to
>>> solve this. As it stands, it looks likely that we'll end up with some
>>> form of DIP 74, and if you have a better proposal, then now is
>>> probably the time to do it.
>>>
>>> Personally, I obviously haven't been following this closely enough,
>>> because I don't understand why something like RefCounted can't be
>>> made to do what we need with regards to reference counting and
>>> classes. It does get a bit nasty when inheritance and whatnot get
>>> involved, but C++ was able to solve that easily enough, and we should
>>> be able to do the same.
>>
>> C++ didn't solve anything(?). C++ doesn't support ref-counting at all!
>> shared_ptr is not a part of the language, or a proper ref counting
>> mechanism. It's just a hack; it's awkward, and really inefficient (the
>> compiler can't optimise it).
>> ARC requires language knowledge. I don't know what language primitives
>> can possibly allow the compiler to do proper ref fiddling optimisation
>> with a lib?
>
> Ref-counting with shared_ptr works just fine. It just doesn't optimize
> out any of the incrementing or decrementing. And while having those
> optimized out would be nice, I don't think that in and of itself that
> makes it worth having ref-counting in the language rather than in the
> library.
>
> Maybe C++ ref-counting hasn't work well for your use cases, but I've
> used it for years, and it's worked great for what I've needed.

Yah, it's a success story and a good baseline. Two things that are 
suboptimal are the necessity of two allocations unless make_shared is 
used, and compulsive interlocked inc/dec. We ought to address both 
issues, but by and large we're looking at a successful experience that 
we want to have D users benefit from as well. -- Andrei