STINNER Victor writes:
> The following change is useless, it cannot overflow:
> -    if (n + k > MAXPATHLEN)
> +    if (k > MAXPATHLEN - n)
>          k = MAXPATHLEN - n;
> 
> n and k maximum values are MAXPATHLEN (and the maximum value of
> MAXPATHLEN is 4096), (...)

OK.  I could only tell that for n, not for k.  But even so it would
certainly be an unlikely overflow.