here is the testcode (also available @ http://paste.debian.net/108547):

int main(string[] args) {
	string path;

	string[] dirs = {
		Environment.get_user_config_dir(),
		"/etc"
	};

	try {
		var cfg = new KeyFile();
		cfg.load_from_dirs("example", dirs, out path, KeyFileFlags.NONE);
	} catch(FileError e) {
		error("FileError: %s", e.message);
	} catch(KeyFileError e) {
		error("KeyFileError: %s", e.message);
	}

	return 0;
}

and here is the valac output:
$ valac test.vala
/home/sre/test.vala.c: In function ‘_vala_main’:
/home/sre/test.vala.c:46: warning: passing argument 3 of ‘g_key_file_load_from_dirs’ from incompatible pointer type
/usr/include/glib-2.0/glib/gkeyfile.h:70: note: expected ‘const gchar **’ but argument is of type ‘gchar **’