In NO_ZERO_DATE mode, multiple timestamp fields with no default can't be created

MariaDB [test]> set sql_mode='';

Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> create table t1(a timestamp, b timestamp);

Query OK, 0 rows affected (0.11 sec)

MariaDB [test]> set sql_mode = 'NO_ZERO_DATE';

Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> create table t2(a timestamp, b timestamp);

ERROR 1067 (42000): Invalid default value for 'b'

MariaDB [test]> create table t2(a timestamp, b int, c timestamp);

ERROR 1067 (42000): Invalid default value for 'c'

MariaDB [test]> create table t2(a timestamp);

Query OK, 0 rows affected (0.07 sec)

MariaDB [test]> set sql_mode='';

Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> create table t1(a timestamp, b timestamp);

Query OK, 0 rows affected (0.06 sec)

MariaDB [test]> set sql_mode='NO_ZERO_DATE';

Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> create index idx on t1(a);

ERROR 1067 (42000): Invalid default value for 'b'

MariaDB [test]> set sql_mode='NO_ZERO_DATE,STRICT_TRANS_TABLES';

Query OK, 0 rows affected (0.01 sec)

MariaDB [test]> create index idx on t1(a);

ERROR 1292 (22007): Incorrect datetime value: '0000-00-00 00:00:00' for column 'b' at row 1

MariaDB [test]> set sql_mode = 'NO_ZERO_DATE';

Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> create table t1 (a timestamp(5) on update current_timestamp(5));

ERROR 1067 (42000): Invalid default value for 'a'

MariaDB [test]> create table t1 (a timestamp(5) on update current_timestamp(4));

ERROR 1294 (HY000): Invalid ON UPDATE clause for 'a' column

MariaDB [test]> create table t1 (a timestamp(5) on update current_timestamp(6));

ERROR 1067 (42000): Invalid default value for 'a'

MariaDB [test]> create table t1 (a timestamp on update current_timestamp);

ERROR 1067 (42000): Invalid default value for 'a'