Geoff Keating <[EMAIL PROTECTED]> writes: | On 22/07/2005, at 4:33 PM, Ian Lance Taylor wrote: | | > Geoffrey Keating <[EMAIL PROTECTED]> writes: | > | >> Although I can see that this is how you might think about the | >> semantics of 'const' and 'volatile', I don't think they're an exact | >> match for the model in the standard. In fact, I think you could | >> exchange the words 'const' and 'volatile' in the above and they would | >> be equally accurate. | >> | > | > Sure, and I think my ultimate point would still be accurate: gcc | > should handle the access using the qualification of the pointer, not | > of the underlying object. The rest of the argument is just | > motivation. | | By "equally accurate", I also meant "equally inaccurate". | | You've successfully argued that 'const' and 'volatile' are the same | in lots of ways; but 'const' and 'volatile' do differ. In order to | be successful in this argument, you need to argue that the | differences don't matter. | | And, unfortunately, the differences *do* matter. The standard does | not say "any expression referring to a volatile-qualified type must | be evaluated strictly according to the rules of the abstract | machine". What it says is that "An object that has volatile | qualified type may be modified in ways unknown to the implementation" | and then lists some of the consequences of an object being modifiable | in that way. So there are no "semantics of the access"; the | semantics attach to the object.
I disagree with statement. There is a "semantics of access". It is implementation-defined. | This is part of what I meant by saying that your model isn't a match | for the model in the standard. Your model had semantics attached to | the access. On the contrary, I find his moel most faithful than the interpretation you offer. The standard describes things like side effect and such in terms of *access*. -- Gaby
