josh@xxxxxxxxxxxxxxxx writes: > 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? Just a friendly ping to get some more reviews to consider in my next resend, especially on [13/13] and whether to relax the constant expression rules to treat pointer differences of address constants as (arithmetic or integer) constant expressions. -- 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
