diff -r -u ./fixed_gif_font.c ./gif_font.c
--- ./fixed_gif_font.c	2019-09-05 11:05:25.009598262 -0700
+++ ./gif_font.c	2019-09-05 10:52:45.308389085 -0700
@@ -11,6 +11,11 @@

 #include "gif_lib.h"

+// Windows doesn't have strtok_r.
+#if defined(WIN32) || defined(_WIN32) || defined(__WIN32) && !defined(__CYGWIN__)
+#define strtok_r strtok_s
+#endif
+
 /*****************************************************************************
  Ascii 8 by 8 regular font - only first 128 characters are supported.
 *****************************************************************************/