[fpc-devel]MySQL component installation

[Christopher Kirkpatrick]

I have been trying to install the MySQLLaz package into my Lazarus
system. It compiles OK, but on linking I get the following errors:

...undefined reference to `mysql_connect'
...undefined reference to `mysql_create_db'
...undefined reference to `mysql_drop_db'

error while linking

This is because I have MySQL v4 installed in my Linux distro (SuSE 9.0
or 9.1) and also WinXP, and the library no longer recognises these
calls. I pointed out in my tutorial on the WiKi

 http://lazarus-ccr.sourceforge.net/index.php?wiki=LazarusDatabase

that changes had to be made to the fpc mysql unit (I used a re-named
unit mysql_ver4) when creating simple applications to access late
versions of MySQL. Although there are files for access to ver 3.3.2 and
ver 4 in subdirectories of ($sourcepath)/fcl/packages/base/mysql, the
units in component packages that use mysql have no mechanism to
distinguish between the different versions. There is a file in each of
the directories called mysql_version, but it only defines the version as
a string, and doesn't do anything to modify the function calls.

In Version 4 of MySQL the function mysql_connect has been replaced by
mysql_real_connect (now with 8 parameters instead of 4); mysql_create_db
and mysql_drop_db have been deprecated in favour of issuing explicit SQL
statements to perform the same function.

I think the mysqldb unit needs to have some conditionals (to take
account of MySQL versions) inserted into the section of the
implementation  dealing with these functions (unless I am missing
something that is already there?).  I am prepared to have a go at making
the necessary modifications, but am reluctant to do so if there is
already some mechanism in place to cope with changes in version of
MySQL, or if one of the original developers can do it better and faster.

We need to be able to define the version of MySQL - usually this is only
done at link time by selecting the appropriate library. We are probably
going to have to ask the user what version he's using before we compile.

Can I have some guidance please from the FPC developers?

Regards - Chris
-- 
Christopher Kirkpatrick <chris.kirkpatrick at doctors.org.uk>