On Fri, Jul 06, 2007 at 01:33:30AM -0700, Josh Triplett wrote: > Al Viro wrote: > > On Thu, Jul 05, 2007 at 11:50:56AM -0700, Josh Triplett wrote: > > > >> No, I mean __attribute__((context(...))), which means something > >> different. __context__() works as a statement statement changing the > >> context. __attribute__((context(...))) works as an attribute modifying > >> a type to say that it requires a given context, and that > >> accessing/calling it changes the context. Somewhat of an odd > >> distinction, but sparse currently works that way. > > > > That's actually not a qualifier from the syntax point of view... > > It makes sense *only* on function types - we simply ignore it > > on anything else. > > For now, yes. I intend to make use of the context attribute on arbitrary > pointers or data. For example, I want to specify that you must hold a given > lock in order to access a structure field, and enforce that context when you > access the field. What kind of annotations on functions do you expect to need for that enforcing? > For functions, yes. In the case of pointers or data, I do want the context > attribute to work like a qualifier: you might want to apply it to a pointer, > or to the pointer target, or to a structure field, or an entire structure... I'm not sure I like the idea of having the same qualifier mean very different things on functions and data objects ["gets locks" vs. "needs locks"]... > If foo requires context x, and bar requires context y, then (n ? foo : bar)(); > *might* require context x and *might* require context y. ... the hell? On functions it's not about "requires", it's about "changes". > See above. Eventually we might have advanced dataflow analysis deriving > attributes for us; for now, function pointers will need explicit contexts. How do you compare two contexts for equality? > Currently ignored, yes. I certainly hope that providing a context expression > proves sufficient to specify a context. Yes, problems arise if you need to do > complex unification of context expressions, but I *think* that we can handle > the simpler cases first and the complicated cases as needed. If you have any > suggestions that might improve context checking, I'd love to discuss them with > you. What do you call simpler cases? A constant being a context expression? - To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
