Re: [Qemu-devel] [PATCH v2] bitmap: fix BITMAP_LAST_WORD_MASK

[Wei Wang]

On 08/07/2018 03:39 PM, Peter Xu wrote:
> On Tue, Jul 31, 2018 at 06:01:18PM +0800, Wei Wang wrote:
> > When "nbits = 0", which means no bits to mask, this macro is expected to
> > return 0, instead of 0xffffffff. This patch changes the macro to return
> > 0 when there is no bit needs to be masked.
> >
> > Signed-off-by: Wei Wang <address@hidden>
> > CC: Juan Quintela <address@hidden>
> > CC: Dr. David Alan Gilbert <address@hidden>
> > CC: Peter Xu <address@hidden>
> Reviewed-by: Peter Xu <address@hidden>
>
> Is there any existing path that can trigger this nbits==0?

Not sure about other bitmap APIs which call this macro. But it happens 
in the patches we are working on, which use bitmap_count_one.
It would be good to have the macro itself handle this corner case, so 
that callers won't need to worry about that.

Best,
Wei