I know that passing a negative timeout to GET_LOCK() makes no sense. But if you do it by mistake (perhaps with dynamic sql) there are 2 cases:

• If the number is high, it is like passing 0:

  MariaDB [(none)]> SELECT GET_LOCK('x', -100);

  +---------------------+

  | GET_LOCK('x', -100) |

  +---------------------+

  | 0 |

  +---------------------+

  1 row in set (0.01 sec)

• if number is very low, it considers it as a positive number (you will need to kill the query):

  SELECT GET_LOCK('x', -1500000000);

  In both cases, I get no errors or warnings.