draft proposal for ref counting in D

[deadalnix]

On Saturday, 12 October 2013 at 06:16:24 UTC, Rainer Schuetze 
wrote:
> in pseudo-assembly missing null-checks:
>
> Thread1 (R = P)        Thread2 (S = R)
>
>                        mov ecx,[R]
>                        ; thread suspended

You need an sequentially consistent write. You also need to 
increment the refcount BEFORE ! This codegen is incorrect.

> mov eax,[P]
> inc [eax].refcnt

Same here.

> mov ebx,[R]
> mov [R],eax
> dec [ebx].refcnt      ; refcnt of O now 0
> jnz done
> call delete_ebx
>                        ; thread resumed
>                        inc [ecx].refcnt
> done:
>
> The increment on [ecx].refcnt modifies garbage.

This can be done atomically (even with eventually consistent 
increment, don't need full sequential consistency here, you still 
need fully sequential consistent decrement).