Safe reference counting cannot be implemented as a library

[Manu via Digitalmars-d]

On 27 October 2015 at 22:27, Andrei Alexandrescu via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On 10/27/2015 07:57 AM, Manu via Digitalmars-d wrote:
>>
>> On 27 October 2015 at 21:41, Andrei Alexandrescu via Digitalmars-d
>> <digitalmars-d at puremagic.com> wrote:
>>>
>>>
>>> It follows that if we want safe reference counting, there must be
>>> language
>>> support for it. One possibility is to attach an attribute to the class
>>> definition:
>>>
>>> @safe @rc class Widget {
>>>    ...
>>> }
>>
>>
>> An attribute? Is presence of opInc()/opDec() insufficient? Would the
>> attribute signal fabrication of some default opInc/opDec operators
>> applicable for general use?
>
>
> You're right, opInc/opDec detection would suffice.
>
> Unrelated, and a foreshadowing of the discussion on the lifetime mailing
> list: the compiler has ample opportunity to fuse incs/decs together, so the
> signatures of these functions is:
>
> void opInc(uint delta);
> void opDec(uint delta);
>
> For example, consider:
>
> class Widget {
>   void fun(Widget, Widget);
> }
> ...
> auto w = new Widget;
> w.fun(w, w);
>
> In this case the compiler may insert opInc with a value larger than 1 prior
> to entering the call.

Awesome. Hadn't thought of that. Nice catch!
Perhaps add me to the list. I don't think I have anything to add that
I haven't said before, but I have very high interest in this topic.