DIP74: Reference Counted Class Objects

[ted via Digitalmars-d]

Andrei Alexandrescu wrote:

> 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.

I'm still a bit confused here: the examples in DIP74 showed the freeing of 
memory via 'GC.free(cast(void*) this);' - so I had assumed that 
'Widget a = new Widget' would be the way it was created? (and that 
automatically uses GC - or is this what I am missing?)

I can see how a system that used (for example) malloc/calloc/free would 
work, I'm just querying the consistency of the examples within DIP74? 

> 
> 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