I have a strong feeling that I'm seeing this warning far too many times when testing stored aggregate functions. But without an error message it's hard for me to say if the bug is in MariaDB or in my tests. So I'll wait for a fix here.

It's ER_SP_STACK_TRACE. The error message is, precisely, "At line %u in %s". As far as I can see from the tests, it happens as

 Warnings:

 Error	1062	Duplicate entry '23' for key 'a'

 Note	4070	At line 4 in test.f2

 Level	Code	Message

 Warning	1012	Raising a warning

 Error	5555	RESIGNAL to not found

 Note	4070	At line 9 in test.test_resignal

 Error	9999	Variable 'sql_mode' can't be set to the value of 'NULL'

 Note	4070	At line 8 in test.peter_p1

The message is pretty clear if you know what it means, but I agree that on itself it's quite puzzling.

We need at least to document it, but also, perhaps, to reword to be less confusing.

What about "Error %u at line %u in %s"? It'd be, say

 Warnings:

 Error	1062	Duplicate entry '23' for key 'a'

 Note	4070	Error 1062 at line 4 in test.f2

I guess it's as good as anything. The current one is confusing because it does look like something is missing.
f_razzoli, but according to the above, you should also be getting some error along with the note. What is it?

Time passed and I cannot find out easily. But actually you already pointed out the problem: if you know what it means, it's clear... otherwise it means nothing. Documenting it would make it more useful, and would make clear that the "poor" message is not a bug.

I assume we agreed on changing the error message as above.

/*-- Testcase for
– -----------------------------------------
– | @sqlstate | @errno | @text |
– -----------------------------------------
– | HY000 | 4094 | At line 5 in test.Divide |
– -----------------------------------------*/

DELIMITER ;;
CREATE OR REPLACE PROCEDURE Divide(IN numerator INT, IN denominator INT, OUT result double)
BEGIN
DECLARE division_by_zero CONDITION FOR SQLSTATE '22012';
DECLARE CONTINUE HANDLER FOR division_by_zero
RESIGNAL SET MESSAGE_TEXT = 'Division by zero / Denominator cannot be zero';
IF denominator = 0 THEN
SIGNAL division_by_zero;
ELSE
SET result := numerator / denominator;
END IF;
END;
;;
delimiter ;
CALL Divide(10,0,@result);
GET DIAGNOSTICS @num_conditions = NUMBER;
SELECT @num_conditions;
GET DIAGNOSTICS CONDITION 2 @sqlstate = RETURNED_SQLSTATE,
@errno = MYSQL_ERRNO, @text = MESSAGE_TEXT;
SELECT @sqlstate, @errno, @text;

serg, rucha174,
maybe now is a good time to do the rewording? I've kept maintenance releases in the fix version field for now, but I suppose fixing it in 10.7 should suffice.