Reference counted containers prototype

[deadalnix]

Le 26/12/2011 20:49, Andrei Alexandrescu a écrit :
> On 12/26/11 12:46 PM, Michel Fortin wrote:
>> Although I am a little concerned by this
>> small but important implementation detail:
>>
>> Your RefCounted destructor is racy.
>>
>> Just like other reference counted things in Phobos, if you somehow store
>> a reference on the GC heap (as a class member for instance), the
>> destructor for that reference struct is called from the GC thread and
>> will decrement the counter from that thread, while another reference
>> could play with the counter from another thread. I know you have plans
>> for a general fix for that hole in destructors, but meanwhile it'd be
>> wise to change the counter to a shared uint and use atomic operations to
>> avoid low level races.
>
> Does the current implementation unfreezes all threads before calling the
> destructors? If so, indeed there's a race.
>
> BTW, the plan is to have the same thread that constructed objects to
> call their destructors; each thread would have a worklist of garbage
> objects to destroy. The list can be reduced during calls to allocation
> functions within each thread, and of course when the thread terminates.
>
>
> Andrei

This is nice for thread local data, but does it make sense for 
immuables/shared ?

I'm not sure this design is secure regrading GC. What happen if the 
destructor of the RefCounted is called, (and will call dispose) and then 
the payload is destructed. We have a risk of double destruction.