--- xwin.c.orig	Sun Jan 12 15:19:48 2020
+++ xwin.c	Mon Feb 10 11:32:25 2020
@@ -13,6 +13,7 @@
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <gtk/gtk.h>
 #include <gdk/gdkkeysyms.h>