atoms: Properly declare as global variables

See #3914

include/xcb.h

@@ -56,7 +56,7 @@
                          XCB_EVENT_MASK_FOCUS_CHANGE |                                                \
                          XCB_EVENT_MASK_ENTER_WINDOW)
 
-#define xmacro(atom) xcb_atom_t A_##atom;
+#define xmacro(atom) extern xcb_atom_t A_##atom;
 #include "atoms.xmacro"
 #undef xmacro
 

src/main.c

@@ -93,6 +93,11 @@ bool shape_supported = true;
 
 bool force_xinerama = false;
 
+/* Define all atoms as global variables */
+#define xmacro(atom) xcb_atom_t A_##atom;
+#include "atoms.xmacro"
+#undef xmacro
+
 /*
  * This callback is only a dummy, see xcb_prepare_cb.
  * See also man libev(3): "ev_prepare" and "ev_check" - customise your event loop