Re: [SmartPtr] intrusive_ref_counter CounterPolicyT requirements API?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2020-12-04 17:44:48

Andrey Semashev wrote:

> > [*] Incidentally we want to increment with memory order relaxed instead 
> > of acq_rel.
>
> This would probably be a good optimization in atomic_count.

atomic_count can't do this because it doesn't have enough knowledge about 
the context in which it's used.

https://github.com/boostorg/smart_ptr/blob/678a544d27d016204c6aed6403b1ffdf0b021d1b/include/boost/smart_ptr/detail/atomic_count.hpp#L33-L43

In principle you can use negative values for the count, again destroying on 
zero.

I could have specified ++a to be relaxed, but it is what it is at this 
point.