Jeff King <peff@xxxxxxxx> writes:
> Yep, but it's not much different than the hundreds of other function
> interfaces we have where sometimes you can pass NULL and sometimes not.
>
> So anyway. What do we want to do here? The fix I have? Something more
> elaborate and reusable? Or perhaps just switch it to:
My preference was to take the patch as-is, as it was clear enough,
before seeing this one ...
> diff --git a/xdiff-interface.c b/xdiff-interface.c
> index 3cd2ac2855..4d20069302 100644
> --- a/xdiff-interface.c
> +++ b/xdiff-interface.c
> @@ -84,8 +84,8 @@ static void trim_common_tail(mmfile_t *a, mmfile_t *b)
> {
> const int blk = 1024;
> long trimmed = 0, recovered = 0;
> - char *ap = a->ptr ? a->ptr + a->size : a->ptr;
> - char *bp = b->ptr ? b->ptr + b->size : b->ptr;
> + char *ap = a->size ? a->ptr + a->size : a->ptr;
> + char *bp = b->size ? b->ptr + b->size : b->ptr;
> long smaller = (a->size < b->size) ? a->size : b->size;
>
> while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
>
> By checking "size" instead of "ptr", then we know that the addition is a
> noop. And we'd continue to catch a NULL pointer mixed with a non-zero
> length (as a segfault). And a non-NULL pointer with a zero length does
> the right thing.
which makes quite a lot of sense.
