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Re: volatile semantics
nathan@codesourcery.com (Nathan Sidwell) wrote on 03.05.05 in <42778D99.7070904@codesourcery.com>:
> Mike Stump wrote:
> > int avail;
> > int main() {
> > while (*(volatile int *)&avail == 0)
> > continue;
> > return 0;
> > }
> >
> >
> > Ok, so, the question is, should gcc produce code that infinitely loops,
> > or should it be obligated to actually fetch from memory? Hint, 3.3
> > fetched.
>
> I beleive the compiler is so licensed. [5.1.2.3/2] talks about accessing
> a volatile object. If the compiled can determine the actual object
> being accessed through a series of pointer and volatile cast conversions,
> then I see nothing in the std saying it must behave as-if the object
> were volatile when it is not.
>
> This, of course, might not be useful to users :)
As a QOI issue, it would be nice if such a situation caused a warning
("ignoring volatile cast ..." or something like that).
It's rather dangerous to have the user believe that this worked as
intended when it didn't.
MfG Kai