On Thu, Jul 23, 2015 at 11:13:57AM +0200, Nicolai Stange wrote: > josh@xxxxxxxxxxxxxxxx writes: > >> Since the additional information on expressions obtained through the > >> first two parts is rather pointless without making any use of it, I > >> implemented part three, the checking of static storage duration > >> objects' initializers for constness. > >> This part is the reason why there is a 'RFC' tag in the subject. > >> It is up to you to decide whether letting sparse check for C99 > >> conformity is a valuable thing to have or whether being stricter than > >> GCC is counter-productive/completely idiotic. > > > > I think it's absolutely a valuable thing to have. It may or may not be > > the right *default* behavior, but having an appropriate -W option to > > enable it would be a good start. > > My next resend will contain such a -Wcheck-static-initializers then. <bikeshed>Shouldn't it be something like -Wnon-constant-initializer, since that's what it checks for?</bikeshed> > However, I will delay that resend in order to be able to incorporate > other reviews arriving in the meantime. Sounds reasonable. > > On Thu, Jul 23, 2015 at 12:54:25AM +0200, Nicolai Stange wrote: > >> sparse now finds 519 occurences of non-const initializers of static > >> storage duration objects, 474 of which are located in drivers/acpi > >> and stem from this subsystem's custom offsetof macro implemented by > >> means of taking pointer differences. > > > > Ideally, I'd suggest that ACPICA should add a translation from > > ACPI_OFFSET to offsetof as part of its Linux-izing scripts. > > > > That said, I also can't think of an obvious reason why ACPI_OFFSET > > *should* be considered non-constant. Perhaps there's a detail in the > > C99 spec that explains why what it does isn't OK, but it *seems* like it > > should be a compile-time constant expression. I've CCed Al Viro, who > > knows the C99 constant expression rules very well; Al, could you provide > > some clarity here? The ACPI_OFFSET macro in question expands to this: > > > > (acpi_size) (((u8 *) (void *) ((&(((struct some_struct *) 0)->fieldname)))) - ((u8 *) (void *) (((void *) (void *) 0)))) > > > > Does the -> make this non-constant? > > No, it is the pointer difference. At least to my interpretion of C99 > [6.6(9)] which might be arguable. > Upon your request, I could relax these constraints as I have did already for > some special cases of conditionals in [11/13]. Ah, I see. I don't know whether relaxing that makes sense or not; Al? - Josh Triplett -- 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
