[cpp-threads] Increment/decrement operators on atomics package

[Raul Silvera]

Lawrence, something that we briefly touched on in Oxford was the question 
of increment operators in the atomics package doing a RMW operation.

I think that it is in generally confusing for t+=1 and t=t+1 to have 
different semantics for an Atomic t. The difference would be that t+=1 
would be RMW operation while t=t+1 is a sequence of 
load_acquire;add;store_release.
The main concern is that users consider these two idioms interchangeable 
and replace one by the other only based on programming style.

My proposal for this issue is to make t+=1 have the same semantics as 
t=t+1 (no RMW). Instead, a separate member functions would be provided to 
do RMW operations (e.g t.atomic_inc(1)).
An alternative proposal would be not to define increment operators for the 
atomic class.

Do you consider this a valid concern? Thanks...

--
Raúl E. Silvera         IBM Toronto Lab         Team Lead, Toronto 
Portable Optimizer (TPO)
Tel: 905-413-4188       T/L: 969-4188           Fax: 905-413-4854 
D2/KC9/8200/MKM
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