Mark usage function as __dead2 in programs where it does not return

In most cases, usage does not return, so mark them as __dead2. For the
cases where they do return, they have not been marked __dead2.

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/735

usr.sbin/pnfsdscopymr/pnfsdscopymr.c

@@ -53,7 +53,7 @@ __FBSDID("$FreeBSD$");
 #include <fs/nfs/nfs.h>
 #include <fs/nfs/nfsrvstate.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct option longopts[] = {
 	{ "migrate",	required_argument,	NULL,	'm'	},

usr.sbin/pnfsdsfile/pnfsdsfile.c

@@ -46,7 +46,7 @@ __FBSDID("$FreeBSD$");
 #include <fs/nfs/nfs.h>
 #include <fs/nfs/nfsrvstate.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct option longopts[] = {
 	{ "changeds",	required_argument,	NULL,	'c'	},

usr.sbin/pnfsdskill/pnfsdskill.c

@@ -43,7 +43,7 @@ __FBSDID("$FreeBSD$");
 #include <fs/nfs/nfskpiport.h>
 #include <fs/nfs/nfs.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct option longopts[] = {
 	{ "force",	no_argument,	NULL,	'f'	},

usr.sbin/quotaon/quotaon.c

@@ -70,7 +70,7 @@ static int	vflag;		/* verbose */
 
 static int oneof(char *, char *[], int);
 static int quotaonoff(struct fstab *fs, int, int);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char **argv)

usr.sbin/repquota/repquota.c

@@ -104,7 +104,7 @@ int oneof(char *, char *[], int);
 int repquota(struct fstab *, int);
 char *timeprt(time_t);
 static void prthumanval(int64_t bytes);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/rip6query/rip6query.c

@@ -62,7 +62,7 @@ static struct rip6	*ripbuf;
 #define	RIPSIZE(n)	(sizeof(struct rip6) + (n-1) * sizeof(struct netinfo6))
 
 int main(int, char **);
-static void usage(void);
+static void usage(void) __dead2;
 static const char *sa_n2a(struct sockaddr *);
 static const char *inet6_n2a(struct in6_addr *);
 
@@ -90,7 +90,6 @@ main(int argc, char *argv[])
 			break;
 		default:
 			usage();
-			exit(1);
 			/*NOTREACHED*/
 		}
 	}
@@ -99,7 +98,6 @@ main(int argc, char *argv[])
 
 	if (argc != 1) {
 		usage();
-		exit(1);
 	}
 
 	if ((s = socket(AF_INET6, SOCK_DGRAM, 0)) < 0) {
@@ -168,13 +166,14 @@ main(int argc, char *argv[])
 		}
 	} while (len == RIPSIZE(24));
 
-	exit(0);
+	return 0;
 }
 
 static void
 usage(void)
 {
 	fprintf(stderr, "usage: rip6query [-I iface] address\n");
+	exit(1);
 }
 
 /* getnameinfo() is preferred as we may be able to show ifindex as ifname */

usr.sbin/rtprio/rtprio.c

@@ -49,7 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 
 static int parseint(const char *, const char *);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/rwhod/rwhod.c

@@ -137,7 +137,7 @@ void	run_as(uid_t *uid, gid_t *gid);
 void	quit(const char *msg);
 void	sender_process(void);
 int	verify(char *name, int maxlen);
-static void usage(void);
+static void usage(void) __dead2;
 
 #ifdef DEBUG
 char	*interval(int time, char *updown);

usr.sbin/setfib/setfib.c

@@ -45,7 +45,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/socket.h>
 #include <sys/sysctl.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/spray/spray.c

@@ -47,7 +47,7 @@ static const char rcsid[] =
 #define SPRAYOVERHEAD	86
 #endif
 
-static void usage(void);
+static void usage(void) __dead2;
 static void print_xferstats(unsigned int, int, double);
 
 /* spray buffer */

usr.sbin/tcpdrop/tcpdrop.c

@@ -58,7 +58,7 @@ static bool tcpdropall(const char *, const char *, int);
 static bool tcpdropbyname(const char *, const char *, const char *,
     const char *);
 static bool tcpdropconn(const struct in_conninfo *);
-static void usage(void);
+static void usage(void) __dead2;
 
 /*
  * Drop a tcp connection.