This macro was ported from Linux and we've reached an aggreement there that the corner case "nbits = 0" is not applicable to this macro, because when "nbits = 0", which means no bits to mask, this macro is expected to return 0, instead of 0xffffffff. This patch simply adds a comment above the macro as a note to users about the corner case.
Signed-off-by: Wei Wang <wei.w.w...@intel.com> CC: Dr. David Alan Gilbert <dgilb...@redhat.com> CC: Juan Quintela <quint...@redhat.com> CC: Peter Xu <pet...@redhat.com> --- include/qemu/bitmap.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h index 509eedd..f53c640 100644 --- a/include/qemu/bitmap.h +++ b/include/qemu/bitmap.h @@ -60,6 +60,7 @@ */ #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) +/* "nbits = 0" is not applicable to this macro. Callers should avoid that. */ #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) #define DECLARE_BITMAP(name,bits) \ -- 2.7.4
