Re: [Vala] mysql bindings in genie

[Jan Hudec <bulb ucw cz>]

On Fri, Sep 10, 2010 at 21:03:44 +1200, Phil Daintree wrote:
> # valac --pkg=mysql mysqltest.gs
> /tmp/ccumEU4F.o: In function `_vala_main':
> mysqltest.vala.c:(.text+0xb6): undefined reference to `mysql_init'
> mysqltest.vala.c:(.text+0xca): undefined reference to `mysql_close'
> mysqltest.vala.c:(.text+0x116): undefined reference to `mysql_real_connect'
> mysqltest.vala.c:(.text+0x13e): undefined reference to `mysql_query'
> mysqltest.vala.c:(.text+0x14c): undefined reference to `mysql_use_result'
> mysqltest.vala.c:(.text+0x160): undefined reference to `mysql_free_result'
> mysqltest.vala.c:(.text+0x178): undefined reference to `mysql_eof'
> mysqltest.vala.c:(.text+0x1de): undefined reference to `mysql_fetch_row'
> mysqltest.vala.c:(.text+0x27b): undefined reference to `mysql_close'
> mysqltest.vala.c:(.text+0x293): undefined reference to `mysql_free_result'
> collect2: ld returned 1 exit status
> error: cc exited with status 256
> Compilation failed: 1 error(s), 0 warning(s)

libmysqlclient does not have a pkg-config file, right? So you have to pass
the relevant linker flags yourself. That would be '-X -lmysqlclient' IIRC.

Normally if you specify "--pkg=something" to valac, it will use
"something.vapi", but it will also ask pkg-config for compiler flags needed
to compile against "something" ("pkg-config --cflags --libs something").
Unfortunately mysql client library does not seem to come with appropriate
data file for pkg-config. Instead it seems to have mysql_config script, that
serves similar purpose, but valac is not able to call these custom scripts.
Therefore you have to specify the flags manually via -X. You have the headers
and libraries installed in default path, but you still need to specify at
least the library name.

> The mysql.h file is under /usr/include/mysql together with all the
> other mysql header files.

The header got included fine and the program compiled fine. The library is
what was missing, so the program failed to link.

-- 
                                                 Jan 'Bulb' Hudec <bulb ucw cz>