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Subj : Re: A question about atomic_ptr
To   : comp.programming.threads
From : Alexander Terekhov
Date : Tue Apr 12 2005 02:15 am


Alexander Terekhov wrote:
> 
> Peter Dimov wrote:
> [...]
> > But on the other hand "int" offers "basic" thread safety by default and
> > "strong" thread safety if I only touch it with atomic_load_acq and
> > atomic_store_rel.
> 
> Only if you properly isolate (align and pad if nessesary) it.

And even properly isolated built-in "int" can be accessed on 
per-bit basis (or per-byte/whatnot, non-atomically) by conforming 
implementations. Just to be anal, so to speak.

> 
> That's one reason for atomic<> wrapper.
> 
> [...]
> > This is also why I'm not particularly fond of Alexander's atomic<> dedicated
> > wrapper type. Providing atomic access via ordinary functions seems more
> > natural.
> 
> Another reason is to "enforce" proper labeling for all accesses by
> making the type opaque. An exclusive access on atomic<int> doesn't
> need to be isolated/atomic at all, it can be combined with other
> accesses. How are you going to do it all with "extended-for-threads"
> C/C++ volatiles (also mentioned by you in another message not here),
> for example?
> 
> What else?

regards,
alexander.

.

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