// main.h
...
GdkWindowAttr attr =
{
	WINDOW_TITLE, 0, 0, 0, WINDOW_WIDTH, WINDOW_HEIGHT, GDK_INPUT_OUTPUT, 
	NULL, NULL, GDK_WINDOW_TOPLEVEL, NULL, NULL, NULL, FALSE,
};
...

// config.c
int WINDOW_WIDTH;
int WINDOW_HEIGHT;
...
cfg_opt_t opts[] = {
        CFG_SIMPLE_INT("windowwidth",&WINDOW_WIDTH),
	CFG_SIMPLE_INT("windowheight",&WINDOW_HEIGHT),
        CFG_END()
    }; 
cfg_t *cfg;
...

// 'make' output -- command is gcc main.c `pkg-config --cflags --libs gtk+-2.0 libconfuse`
$ make
gcc main.c `pkg-config --cflags --libs gtk+-2.0 libconfuse`
In file included from main.c:9:
main.h:15: error: initializer element is not constant
main.h:15: error: (near initialization for ‘attr.width’)
main.h:15: error: initializer element is not constant
main.h:15: error: (near initialization for ‘attr.height’)
make: *** [all] Error 1