CURTIME, UTC_TIME and UTC_TIMESTAMP accept precision 65536 as zero

MariaDB accepts an explicitly requested fractional-seconds precision of 65536 for CURTIME(), UTC_TIME() and UTC_TIMESTAMP(). The functions return values with zero fractional digits instead of rejecting the precision with ER_TOO_BIG_PRECISION (1426).

Steps to reproduce

1. Connect to MariaDB 12.3.3.
2. Execute each statement separately, in the following order:

SELECT OCTET_LENGTH(CURTIME(65536)) AS curtime_length;

SELECT OCTET_LENGTH(UTC_TIME(65536)) AS utc_time_length;

SELECT OCTET_LENGTH(UTC_TIMESTAMP(65536)) AS utc_timestamp_length;

SELECT OCTET_LENGTH(CURTIME(6)) AS valid_length;

SELECT CURTIME(7) AS invalid_precision;

SELECT CAST('12:34:56' AS TIME(65536)) AS cast_precision;

These statements are read-only and require no setup.

Actual result

The first three statements succeed:

curtime_length

8

utc_time_length

8

utc_timestamp_length

19

The valid CURTIME(6) control succeeds and returns a length of 15. The two rejection controls produce the expected errors:

ERROR 1426 (42000): Too big precision specified for 'curtime'. Maximum is 6

ERROR 1426 (42000): Too big precision specified for '12:34:56'. Maximum is 6

Expected result

Each explicitly requested temporal fractional precision greater than 6 should be rejected with ER_TOO_BIG_PRECISION (1426). In particular, precision 65536 should not be accepted as a zero-fractional-precision value.

The differing treatment of 7 and 65536 indicates that the full-width precision is not preserved through validation for these temporal functions, while the TIME cast correctly rejects 65536.

This occurs when CURTIME, UTC_TIME or UTC_TIMESTAMP is given the exceptional precision value 65536.