https://github.com/resurrecting-open-source-projects/sniffit/pull/3

From a05340968343d9f61f57506ed00bff0a62d3f38e Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Thu, 28 Jul 2022 12:14:44 +0100
Subject: [PATCH] Fix -Wimplicit-function-declaration

--- a/src/sn_cfgfile.c
+++ b/src/sn_cfgfile.c
@@ -2,6 +2,7 @@
 /*   - by          : Brecht Claerhout                                     */
 /*   - improvements: Shudoh Kazuyuki                                      */
 
+#include <ctype.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
--- a/src/sn_generation.c
+++ b/src/sn_generation.c
@@ -13,7 +13,9 @@
 #include "sn_curses.h"
 #include "sn_defines.h"
 #include "sn_structs.h"
+#include "sn_packets.h"
 #include "sn_generation.h"
+#include "sn_interface.h"
 
 extern volatile int screen_busy;
 
--- a/src/sn_interface.c
+++ b/src/sn_interface.c
@@ -4,6 +4,7 @@
 #include "sn_config.h"
 
 #ifdef INCLUDE_INTERFACE
+#include <ctype.h>
 #include <signal.h>
 #include <termios.h>
 #include <stdlib.h>
--- a/src/sniffit.c
+++ b/src/sniffit.c
@@ -3,6 +3,7 @@
 
 #include "sn_config.h"		/* Config header file */
 
+#include <ctype.h>
 #include <unistd.h>
 #include <signal.h>
 #include <stdlib.h>