--- src/sounding.c.orig	2001-10-10 22:15:30.000000000 +0900
+++ src/sounding.c	2020-11-21 15:57:23.000000000 +0900
@@ -62,6 +62,7 @@
 /* MJK 12.15.98 */
 #  include      "topo.h"
 #  include      "v5d.h"
+extern void free_Xgfx( Xgfx *);
 #  define SOUND_BARB_SIZE               48
 #  define PI                            3.14159265