Re: [PATCH][RFC] Remove volatile from data members in libstdc++

[Martin Sebor <sebor at roguewave dot com>]

Boehm, Hans wrote:
> > From: Richard Guenther [mailto:rguenther@suse.de] 
> >
> > I believe gcc at the moment won't do it, but of course from 
> > the standards point of view it is permittet to treat local 
> > just like global inside the function.  And indeed volatile 
> > guarantees you a single access of global here - though it is 
> > sufficient to make the access volatile and not the data, like in
> >
> >  unsigned local = *(volatile unsigned *)&global;
[...]
> I agree that a volatile cast for the read is just as good.

Sorry to jump in on this, but just as an FYI, there is at least
one compiler where the cast doesn't have the same effect (i.e.,
the compiler takes into account the volatility of the object
in the cast) and that, we were told by the compiler vendor, is
a feature and not a bug. I realize that's unrelated to gcc or
the problem in rope but I think it's interesting to note that
different implementers have different interpretations of what
volatile should mean even in seemingly straightforward cases
like this one.

Martin