From: Marko Mäkelä
Date: October 21 2010 6:54am
Subject: Re: bzr commit into mysql-5.5-innodb branch (marko.makela:3192)
 Bug#57588
List-Archive: http://lists.mysql.com/commits/121441
Message-Id: <20101021065429.GA2554@x60s>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed

On Thu, Oct 21, 2010 at 08:25:00AM +1100, Sunny Bains wrote:
>> /* Get mbmaxlen from mbminmaxlen. */
>> -#define DATA_MBMAXLEN(mbminmaxlen) ((mbminmaxlen) / DATA_MBMAX)
>> +#define DATA_MBMAXLEN(mbminmaxlen) ((ulint) ((mbminmaxlen) / DATA_MBMAX))
>
>This cast was dropped in the final version to catch type mismatch 
>between the two macros. If someone changes the type of the underlying 
>variables after your fix we will not catch the mismatch.  Unless the 
>original fix didn't solve the problem this change should be reverted.

The original fix was causing a warning in handler0alter.cc:

		ut_ad(DATA_MBMAXLEN(col->mbminmaxlen)
		      >= DATA_MBMINLEN(col->mbminmaxlen));
		ut_ad(DATA_MBMAXLEN(col->mbminmaxlen)
		      > DATA_MBMINLEN(col->mbminmaxlen) || flen == len);

This is because DATA_MBMAXLEN would have returned unsigned and 
DATA_MBMINLEN (after the cast that you added) would have returned ulint:

	unsigned	mbminmaxlen:5;	/*!< minimum and maximum length of a
					character, in bytes;
					DATA_MBMINMAXLEN(mbminlen,mbmaxlen);
					mbminlen=DATA_MBMINLEN(mbminmaxlen);
					mbmaxlen=DATA_MBMINLEN(mbminmaxlen) */

Best regards,

	Marko