Talk:c/string/byte/strcat

UB of strcat_s

                  ----------------------------------
           src:   |                    | \0 |      |
                  ---------------------------------- 
                  |                         |
                  |                         | 
                  V                         V                  destsz
        --------------------------..............................
dest:   |         | \0 |         |                             .
        --------------------------..............................