Re: [boost] Re: [shared_ptr] Interlocked* - possible bug?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-09-30 12:25:44

Alexander Terekhov wrote:
> Peter Dimov wrote:
>> 
>> Alexander Terekhov wrote:
>>>> No, it's not; C++ behavior _is defined in terms of_ volatile (and
>>>> I/O calls), not the other way around.
>>> 
>>> As if rule. And C++ says nothing about mutiple threads.
>> 
>> Nope. "As if" is defined in terms of observable behavior, and
>> "observable behavior" is defined in terms of volatile and I/O.
> 
> int main() {
>  volatile int a = 1;
>  return --a;
> }
> 
> prove that it can't be transformed to
> 
> int main() {
> }

The observable behavior is

write volatile @a 1
read volatile @a x
write volatile @a x-1
exit(x-1)

in the first case, and

exit(0)

in the second case. By definition. There's nothing to prove. ;-)