[Vala] Question about valac symbols (-D, --define)

[Tomasz Jankowski <tomcioj gmail com>]

Hello!

I'm new to Vala. I already integrated it with my project (I use Autotools).
I have problem with defining preprocessor symbol, I want to do something
like this:

gcc -DDATA_DIRECTORY_PATH="../data" main.c -o app


where I use DATA_DIRECTORY_PATH somewhere in main.c as regular string. When
I try to do something similar with valac it fails, her's make output:

/usr/bin/valac --define=DATA_DIRECTORY_PATH="../data" --pkg=gtk+-2.0  -C
main.vala
main.vala:29.17-29.35: error: The name `DATA_DIRECTORY_PATH' does not exist
in the context of `Main.main'
    string path = DATA_DIRECTORY_PATH;
                ^^^^^^^^^^^^^^^^^^^
Compilation failed: 1 error(s), 0 warning(s)