Consider the following case:
CREATE TABLE t1 (a INT, b VARCHAR(30)) CHARSET=utf8mb4;
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INSERT INTO t1 VALUES (1, 'one'), (0, NULL), (3, 'three'), (4, 'four');
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PREPARE stmt1 FROM 'DELETE FROM t1 WHERE b=?' ;
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SET @arg00=NULL;
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EXECUTE stmt1 USING @arg00; # <<=== First time the prepared statement 'stmt1' is executed
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SET @arg00='one';
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EXECUTE stmt1 USING @arg00; <<=== Second time the same prepared statement is executed results in memory leaks
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The essential prerequisite in the above use case is that the table t1 is created with CHARSET=utf8mb4. Without explicit clause 'CHARSET=utf8mb4' in CREATE TABLE statement, the aforementioned test case would complete with success up to 11.6 where the default characterset was changed from latin1 to utf8mb4 (commit 36eba98817339f53cc57f1d4884ace3efb38db8d)
Bug
Critical
MDEV-14959 Control over memory allocated for SP/PS
