On 11/21/2012 3:42 PM, Carlos O'Donell wrote: > David, > > Thanks for the great UAPI work. While working on glibc mman.h sync I had > the chance to look more closely at some of the UAPI headers. > > Currently (3.7.0-rc6) sparc, powerpc, and tile are including mman-common.h, > but nothing in mman-common.h helps prevent the accidental definition of an > overlapping new constant value. > > For example in mman.h powerpc defines: > #define MAP_NORESERVE 0x40 /* don't reserve swap pages */ > #define MAP_LOCKED 0x80 > > If someone were to add a new MAP_* value in mman-common.h at 0x40 it > would conflict with the existing powerpc value. The powerpc maintainers > might not notice, and that's a bug. > > I notice that someone is trying to avoid this kind of bug, because for > example the new MADV_HWPOISON was chosen as 100, which is higher than > any other MADV_* value for any architecture. > > Rather than avoid the problem by spot-checking, would it be acceptable > to merge in some private macros that block out exactly which constants > are already in use as existing values for arches using UAPI headers? > > Doing it this way would allow for the merged arches to more safely > include the asm-generic version of mman.h and start benefiting from new > constants without the usual maintenance cost (not to mention everyone > would start in lock-step going forward). Not to mention it simplifies > some of the glibc maintenance. This proposal looks reasonable to me and the proposed code seems OK for tile, at least. Thanks! -- Chris Metcalf, Tilera Corp. http://www.tilera.com -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
