On Thu, 4 Nov 2021 at 22:34, Taylor Simpson <tsimp...@quicinc.com> wrote:
>
> Coverity is getting confused here. The index can never actually overflow.
> Does Coverity have a pragma or something to tell it it's OK?
>
> The loop nest in question is (the index must be < 128)
> for (int offset = 1; offset < 128; offset <<= 1) {
> for (int k = 0; k < 128; k++) {
> if (!(k & offset)) {
> swap(vector1.ub[k], vector0.ub[k + offset]);
> }
> }
> }
> Basically, it's looking for elements to swap, and the
> "if (!(k & offset))" prevents "k + offset" from overflowing.
Yes, I agree this is a false positive. I've marked it as an FP
in the Coverity web UI.
I suspect that changing "k + offset" to "k | offset" would
probably stop Coverity complaining, but we should only do that
if you think it's more readable that way. (As I read the code
we are doing bit operations here rather than addition, so
it seems slightly better to be using the OR; but there's not
a lot in it.)
thanks
-- PMM
