Add G_END_DECLS #include "category.h" G_BEGIN_DECLS
Thanks! I added that and it work just fine. Is there any documentation that explain what these macros do? The API reference of GLib gives a very short explanation: "Used (along with G_END_DECLS <http://developer.gnome.org/doc/API/2.0/glib/glib-Miscellaneous-Macros.html#G-END-DECLS:CAPS>) to bracket header files".