From: Michael Widenius
Date: June 6 2009 11:33am
Subject: Re: MySQL Reengineering Project
List-Archive: http://lists.mysql.com/internals/36852
Message-Id: <18986.21524.882892.648735@narttu.askmonty.org>
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Hi!

Just noticed that I had missed this email. Better to get an answer
late than never...

>>>>> "Alaric" == Alaric Snell-Pym <alaric@stripped> writes:

Alaric> On 14 May 2009, at 12:39 am, Michael Widenius wrote:

Alaric> That, combined with the fact that in my recent foray into
>> UDFs I found
Alaric> that string UDFs are passed a buffer with room for 255
>> characters to
Alaric> put their result into, and then have the choice of using it
>> and
Alaric> returning a pointer to it or mallocing their own buffer and
>> returning
Alaric> a pointer to that (meaning that the caller, somewhere, must
>> have code
Alaric> to the effect of "if (returned_ptr != allocated_buffer)
Alaric> free(returned_ptr)" to clear up, I guess?),
>> 
>> Actually the idea was that you would in your object remember the
>> malloc you did and then free it.
>> 
>> So the code would be in the destructor:
>> 
>> x_free(malloc_pointer);

Alaric> What object? In a UDF, I just declare a function, as per http://dev.mysql.com/doc/refman/5.1/en/udf-return-values.html
Alaric>   - I surrender the pointer to mysql when I return, and have no chance
Alaric> to free it myself?

<cut>

You should store a copy of the pointer you alloc and free it in the
destructor.

See 'sequence_init()' in udf_example.c

Regards,
Monty