On Wed, Feb 03, 2016 at 12:09:16PM +0800, Christopher Li wrote: > On Wed, Feb 3, 2016 at 11:43 AM, Luc Van Oostenryck > <luc.vanoostenryck@xxxxxxxxx> wrote: > pped. > > > > The nocast mod is dropped and lost in the function create_pointer(). > > In the example above, "cputime_t *" has type : > > unsigned long [nocast] [usertype] * > > while &utime is just: > > unsigned long * > > That is my point. Why does "&utime" get drop but "cputime_t *" does not? > They both are pointer of a base type. They both create pointers. Well with "cputime_t *" you got the pointer directly, by its own declaration; with "&utime" you really _create_ one with the "&"/"addressof" operator. The function "create_pointer()" is only called when evaluating an expression using the addressof operator or when when an array of a function is degenerated into a pointer. > It seems to me the bug is sparse not treating this two case consistently. > > > So, for sparse and its extended notion of type, the type we get when > > taking the address of a [variable of some] type X is not the same as > > directly using a pointer to the type X. > > In C language type system, these two should be the same type. It is a > bug in sparse if they are not. I would rather get that bug fixed. They _have_ the same type if we limit ourselves to the pure C type system, but they differ once we look also at the sparse & gcc extension to the type system, like the nocast attribute here. Now, whether they should be the same or not is a question of defining the semantic of the addressof operator on sparse's type extension. > > Which is very fine, just that MOD_NOCAST is dropped while the example > > shows that it should not. > > I think that is a separate issue weather MOD_NOCAST should be inherent > from pointer base type. I'm not sure to understand you here. > Same with MOD_STORAGE. > > Chris Luc -- 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
