DIP74: Reference Counted Class Objects

[Manu via Digitalmars-d]

On 28 February 2015 at 01:43, Andrei Alexandrescu via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On 2/27/15 7:17 AM, Manu via Digitalmars-d wrote:
>>
>> I'm not clear on structs. What is the order for calls; postblit,
>> opInc, opDec, destructor? 75% of my use cases today are thin structs
>> that wrap C/C++ api's.
>
>
> Structs don't get any special treatment with DIP74, only classes and
> interfaces.

Well this is the case of the highest value to me, and DIP74 offers nothing?
Can I call opAddRef/opRelease from within the postblit/destructor
manually and expect the compiler to elide calls correctly?
That doesn't seem foolproof though, and you also said manual calls are
not @safe. Why not specify a call sequence?


>> There's no mention of 'scope'. I presume functions that receive scope
>> RC arguments will have the opportunity to have opAddRef/opRelesae
>> elided around the call?
>
>
> That might be a future improvement. In fact that may be possible today; I've
> spoken to an ARC expert who read DIP74 and said Apple's ARC does not insert
> a retain() for a function call, i.e. it assumes functions only borrow unless
> they actually do keep a pointer (e.g. assign to a member or global), and
> only in that case inserts a retain().
>
> If I'm not missing something, we can do this with DIP74 which will reduce
> the opAddRef/opRelease traffic quite a bit.

Hmmm, that does sound right. Very nice.