On Fri, Jan 19, 2018 at 2:20 AM, Jann Horn <jannh@xxxxxxxxxx> wrote:
>> + \
>> + __u._ptr = _arr + (_i & _mask); \
>> + __u._bit &= _mask; \
>
> AFAICS, if `idx` is out of bounds, you first zero out the index
> (`_i & _mask`) and then immediately afterwards zero out
> the whole pointer (`_u._bit &= _mask`).
> Is there a reason for the `_i & _mask`, and if so, can you
> add a comment explaining that?
I think that's just leftovers from my original (untested) thing that
also did the access itself. So that __u._bit masking wasn't masking
the pointer, it was masking the value that was *read* from the
pointer, so that you could know that an invalid access returned
0/NULL, not just the first value in the array.
Linus
