[cpp-threads] RE: volatile, memory models, threads

[Peter Dimov]

Nick Maclaren wrote:
> "Peter Dimov" <pdimov at mmltd.net> wrote:
>>
>> 2. making "atomic" a (non cv-) qualifier that can't be added
>> implicitly, can be casted away relatively safely, and can possibly
>> be added via a cast relatively unsafely.
>
> The weakness of that is you then have to define ordering semantics
> between atomic and non-atomic accesses to the same object.  It
> doesn't help if you forbid it, because you have to defined WHAT
> you are forbidding.

It seems to me that we have to define it in either case, because we want to 
allow races if

1. both operations are reads
2. both operations are atomics

and disallow everything else. So outlawing write+read and write+write will 
automatically take care of atomic_write+read, write+atomic_read, 
atomic_write+write.