Bug #37301 Length and Max_length differ with no obvious reason

Description:
Length and Max_length differ with no obvious reason for "SHOW CREATE TABLE..." This occur somewhere after 5.0.44, all later versions affected.

How to repeat:
CREATE TABLE `new_bug` (
 `Codigo` int(10) unsigned NOT NULL auto_increment,
 `Nombre` varchar(255) default NULL,
 `Telefono` varchar(255) default NULL,
 `Observaciones` longtext,
 `Direccion` varchar(255) default NULL,
 `Dni` varchar(255) default NULL,
 `CP` int(11) default NULL,
 `Provincia` varchar(255) default NULL,
 `Poblacion` varchar(255) default NULL,
 PRIMARY KEY  (`Codigo`)
) ENGINE=MyISAM AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;

mysql> show create table a;
Field   1:  `Table`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       VAR_STRING
Collation:  cp1251_general_ci (51)
Length:     21
Max_length: 1
Decimals:   31
Flags:      NOT_NULL

Field   2:  `Create Table`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       VAR_STRING
Collation:  cp1251_general_ci (51)
Length:     341  <<<
Max_length: 445  <<<
Decimals:   31
Flags:      NOT_NULL 

Suggested fix:
This has been spotted working on Bug#24131. Thanks to Lawrin & JimW for following up.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/48153

2640 Sergey Glukhov	2008-06-19
      Bug#37301 Length and Max_length differ with no obvious reason
      Length value is the length of the field,
      Max_length is the length of the field value.
      So Max_length can not be more than Length.
      The fix: fixed calculation of the Item_empty_string item length

I'd recommend not to do the assignement in the constructor call. Seems a bit risky. Use collation.collation member instead.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/48161

2640 Sergey Glukhov	2008-06-19
      Bug#37301 Length and Max_length differ with no obvious reason(2nd version)
      Length value is the length of the field,
      Max_length is the length of the field value.
      So Max_length can not be more than Length.
      The fix: fixed calculation of the Item_empty_string item length

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/51781

2665 Chad MILLER	2008-08-15
      Bug#37301 Length and Max_length differ with no obvious reason(2nd version)
      Length value is the length of the field,
      Max_length is the length of the field value.
      So Max_length can not be more than Length.
      The fix: fixed calculation of the Item_empty_string item length
      
      (Patch applied and queued on demand of Trudy/Davi.)

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/51786

2665 Chad MILLER	2008-08-15
      Bug#37301 Length and Max_length differ with no obvious reason(2nd version)
      Length value is the length of the field,
      Max_length is the length of the field value.
      So Max_length can not be more than Length.
      The fix: fixed calculation of the Item_empty_string item length
      
      (Patch applied and queued on demand of Trudy/Davi.)

Queued to 5.0-bugteam, 5.1-bugteam, and 6.0-bugteam on demand of Trudy/Davi.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/52016

2713 Sergey Glukhov	2008-08-20
      after merge fix, related to bug#37301 changes

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/52017

2713 Sergey Glukhov	2008-08-20
      after merge fix, related to bug#37301 changes

Pushed into 5.1.28  (revid:gluh@mysql.com-20080820081542-i187hhlx4oxxnan2) (version source revid:gluh@mysql.com-20080820081542-i187hhlx4oxxnan2) (pib:3)

Noted in 5.1.28 changelog.

The max_length result set metadata value was calculated incorrectly 
under some circumstances.

Setting report to Patch Queued pending push of fix to 5.0.x/6.0.x.

Pushed into 6.0.7-alpha  (revid:gluh@mysql.com-20080820081542-i187hhlx4oxxnan2) (version source revid:sven@mysql.com-20080818175803-c1nutd5773r6b4gd) (pib:3)

Noted in 6.0.7 changelog.

Setting report to NDI pending push into 5.0.x.

Noted in 5.0.70 changelog.