Re: [boost] [Atomic] Rationale for preventingcopyconstruction/assignment?

Subject: Re: [boost] [Atomic] Rationale for preventingcopyconstruction/assignment?
From: Peter Dimov (lists_at_[hidden])
Date: 2013-05-31 04:49:37

Rob Stewart wrote:
On May 30, 2013, at 5:34 AM, "Peter Dimov" <lists_at_[hidden]> wrote:
...
> > I don't think that the copy can be wrong, although I may be missing 
> > something. From a cursory inspection, it seems to me that
> >
> >   a1 = a2;
> >
> > and
> >
> >   r1 = a2;
> >   a1 = r1;
> >
> > are equivalent. It's true that in the second case a2's value can change 
> > after the first line, but it can change in the first case after the only 
> > line as well (which corresponds to changing after the second line in the 
> > second case), and the observable effect is the same (except in the 
> > trivial case in which a1 and a2 are the same variable, but that's easily 
> > taken care of).
>
> While what you say is true, the two are different from a sequential 
> consistency POV.

I don't think so.