The issue is: the two functions that we're comparing for correctness treat lengths very differently: one scans len-1 bytes, the other scans len+1 bytes.

Even with a null terminator, there isn't a length that would work for both without overrunning the buffer.

        printf("%d %d\n", search_ok_1("mok", 2), search_ok_2("mok", 2));
        printf("%d %d\n", search_ok_1("mok", 3), search_ok_2("mok", 3));   /* Overruns without null term */
        printf("%d %d\n", search_ok_1("mok", 4), search_ok_2("mok", 4));   /* Overruns even WITH null term */

Prints out:

    1 2
    1 3
    1 1