Bug #3296 SET character_set_results=NULL crashes server

• Submitted: 25 Mar 2004 16:36
• Modified: 30 Mar 2004 23:17
• Reporter: Paul DuBois
• Status: Closed
• Category: MySQL Server
• Severity: S2 (Serious)
• Version: 4.1.2
• OS: Linux (Linux)
• Assigned to: Oleksandr Byelkin
• CPU Architecture: Any

[25 Mar 2004 16:36] Paul DuBois

Description:
On Mac OS X, I can set character_set_results to NULL
and retrieve the value:

mysql> set character_set_results=null;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@character_set_results;
+-------------------------+
| @@character_set_results |
+-------------------------+
| NULL                    |
+-------------------------+
1 row in set (0.00 sec)

But on Red Hat or Gentoo Linux, the server crashes:

mysql> set character_set_results=null;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@character_set_results;
ERROR 2013 (HY000): Lost connection to MySQL server during query

How to repeat:
See above.

[25 Mar 2004 17:36] Paul DuBois

Additional information: The crash is specific to the use of SELECT @@var_name
form.  Retrieving the value using SHOW VARIABLES works fine:

mysql> set character_set_results=null;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'character\_set\_results';
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| character_set_results | NULL  |
+-----------------------+-------+
1 row in set (0.00 sec)

[25 Mar 2004 18:23] MySQL Verification Team

Paul I tested on Windows and Suse 9.0 with a server built with 1 day older BK
4.1 tree without to crash.

[30 Mar 2004 9:28] MySQL Verification Team

Sorry Paul,

But works for me fine too.

[30 Mar 2004 9:49] Paul DuBois

Sinisa,

What kind of system did you try it on? I already indicated below
that it happens only on some systems.

I'm disappointed you declare it not a bug, given that it's a trivial
way to crash the server.  If you tell me what information would be
helpful, I'll try to provide it.

[30 Mar 2004 10:02] MySQL Verification Team

This was tested on both Linux and Windows.

[30 Mar 2004 12:44] Oleksandr Byelkin

ChangeSet 
  1.1746 04/03/30 23:38:56 [e-mail] +3 -0 
  null processing for character_set_results (BUG#3296)

[30 Mar 2004 23:17] Oleksandr Byelkin

Thank you for bugreport. Patch for this bug is pushed to our internal source 
repository and will be present in next release of server 4.1