diff --git a/lib/libatm/Makefile b/lib/libatm/Makefile
index 1de2e13177cb..6957c60249a5 100644
--- a/lib/libatm/Makefile
+++ b/lib/libatm/Makefile
@@ -33,5 +33,6 @@ INCS=	libatm.h
 
 LDADD+=	-lmd
 DPADD+=	${LIBMD}
+WARNS?=	5
 
 .include <bsd.lib.mk>
diff --git a/lib/libatm/atm_addr.c b/lib/libatm/atm_addr.c
index f92c4b13c973..ef860a60d494 100644
--- a/lib/libatm/atm_addr.c
+++ b/lib/libatm/atm_addr.c
@@ -183,6 +183,10 @@ get_hex_atm_addr(in, out, len)
 			val += c_value;
 			out[out_len] = (u_char) val;
 			out_len++;
+			if (out_len > len)
+				(void)fprintf(stderr, "%s() out_len > len (%d > %d)\n",
+						__func__, out_len, len);
+				
 			break;
 
 		case 4:
@@ -305,7 +309,8 @@ format_atm_addr(addr)
 		u2.c[3] = atm_spans->aas_addr[7];
 
 		if (!(u1.w == 0 && u2.w == 0))
-			sprintf(str, "0x%08lx.%08lx", ntohl(u1.w), ntohl(u2.w));
+			sprintf(str, "0x%08lx.%08lx",
+				(u_long)ntohl(u1.w), (u_long)ntohl(u2.w));
 		break;
 
 	case T_ATM_PVC_ADDR:
diff --git a/lib/libatm/cache_key.c b/lib/libatm/cache_key.c
index 680f44a11984..da08df216f1e 100644
--- a/lib/libatm/cache_key.c
+++ b/lib/libatm/cache_key.c
@@ -85,7 +85,7 @@ scsp_cache_key(ap, ip, ol, op)
 	 * Copy the addresses into a buffer for MD5 computation
 	 */
 	len = sizeof(struct in_addr) + ap->address_length;
-	if (len > sizeof(buff))
+	if (len > (int)sizeof(buff))
 		len = sizeof(buff);
 	bcopy(ip, buff, sizeof(struct in_addr));
 	bcopy(ap->address, &buff[sizeof(struct in_addr)],
diff --git a/lib/libatm/ip_addr.c b/lib/libatm/ip_addr.c
index 23288a81202c..df10acb7e677 100644
--- a/lib/libatm/ip_addr.c
+++ b/lib/libatm/ip_addr.c
@@ -73,18 +73,18 @@ get_ip_addr(p)
 	char	*p;
 {
 	struct hostent			*ip_host;
-	static struct sockaddr_in	sin;
+	static struct sockaddr_in	s;
 
 	/*
 	 * Get IP address of specified host name
 	 */
-	bzero(&sin, sizeof(sin));
-	sin.sin_family = AF_INET;
+	bzero(&s, sizeof(s));
+	s.sin_family = AF_INET;
 	if (p[0] >= '0' && p[0] <= '9') {
 		/*
 		 * IP address is in dotted decimal format
 		 */
-		if ((sin.sin_addr.s_addr = inet_addr(p)) == -1) {
+		if ((s.sin_addr.s_addr = inet_addr(p)) == INADDR_NONE) {
 			return((struct sockaddr_in *)0);
 		}
 	} else {
@@ -96,9 +96,9 @@ get_ip_addr(p)
 				ip_host->h_addrtype != AF_INET) {
 			return((struct sockaddr_in *)0);
 		}
-		sin.sin_addr.s_addr = *(u_long *)ip_host->h_addr_list[0];
+		s.sin_addr.s_addr = *(u_long *)ip_host->h_addr_list[0];
 	}
-	return(&sin);
+	return(&s);
 }
 
 
@@ -115,7 +115,7 @@ get_ip_addr(p)
  *	char *	pointer to a text-formatted string
  *
  */
-char *
+const char *
 format_ip_addr(addr)
 	struct in_addr	*addr;
 {
diff --git a/lib/libatm/libatm.h b/lib/libatm/libatm.h
index 61dd6ccb3014..70142330c049 100644
--- a/lib/libatm/libatm.h
+++ b/lib/libatm/libatm.h
@@ -71,7 +71,7 @@ struct harp_timer {
 	struct harp_timer	*ht_next;	/* Timer chain */
 	int			ht_ticks;	/* Seconds till exp */
 	int			ht_mark;	/* Processing flag */
-	void			(*ht_func)();	/* Function to call */
+	void	(*ht_func)(struct harp_timer *);	/* Function to call */
 };
 typedef struct harp_timer	Harp_timer;
 
@@ -100,7 +100,7 @@ extern int		get_netif_info(char *, struct air_netif_rsp **);
 
 /* ip_addr.c */
 extern struct sockaddr_in	*get_ip_addr(char *);
-extern char		*format_ip_addr(struct in_addr *);
+extern const char		*format_ip_addr(struct in_addr *);
 
 /* ip_checksum.c */
 extern short		ip_checksum(char *, int);
@@ -108,9 +108,9 @@ extern short		ip_checksum(char *, int);
 /* timer.c */
 extern Harp_timer	*harp_timer_head;
 extern int		harp_timer_exec;
-extern void		timer_proc();
-extern int		init_timer();
-extern int		block_timer();
+extern void		timer_proc(void);
+extern int		init_timer(void);
+extern int		block_timer(void);
 extern void		enable_timer(int);
 
 
diff --git a/lib/libatm/timer.c b/lib/libatm/timer.c
index 898e2929a79e..1870e55c017b 100644
--- a/lib/libatm/timer.c
+++ b/lib/libatm/timer.c
@@ -72,7 +72,7 @@ int		harp_timer_exec;
  *
  */
 static void
-timer_tick()
+timer_tick(void)
 {
 	/*
 	 * Bump the timer flag
@@ -96,10 +96,10 @@ timer_tick()
  *
  */
 void
-timer_proc()
+timer_proc(void)
 {
 	Harp_timer	*htp;
-	void		(*f)();
+	void		(*f)(Harp_timer *);
 
 	/*
 	 * Reset marks in all timers on the queue
@@ -188,7 +188,7 @@ init_timer()
 	/*
 	 * Set up signal handler
 	 */
-	if (signal(SIGALRM, timer_tick) == SIG_ERR) {
+	if (signal(SIGALRM, (sig_t)timer_tick) == SIG_ERR) {
 		return(errno);
 	}