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/fdcontrol/fdcontrol.c

@@ -47,7 +47,7 @@ static	int format, verbose, show = 1, showfmt;
 static	char *fmtstring;
 
 static void showdev(enum fd_drivetype, const char *);
-static void usage(void);
+static void usage(void) __dead2;
 
 static void
 usage(void)

usr.sbin/gstat/gstat.c

@@ -66,7 +66,7 @@ static int flag_I = 1000000;
 			printw(__VA_ARGS__);				\
 	} while(0)
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static const char*
 el_prompt(void)

usr.sbin/iostat/iostat.c

@@ -149,7 +149,7 @@ static int dflag = 0, Iflag = 0, Cflag = 0, Tflag = 0, oflag = 0, Kflag = 0;
 static int xflag = 0, zflag = 0;
 
 /* local function declarations */
-static void usage(void);
+static void usage(void) __dead2;
 static void needhdr(int signo);
 static void needresize(int signo);
 static void needreturn(int signo);
@@ -173,6 +173,7 @@ usage(void)
 	fprintf(stderr, "usage: iostat [-CdhIKoTxz?] [-c count] [-M core]"
 		" [-n devs] [-N system]\n"
 		"\t      [-t type,if,pass] [-w wait] [drives]\n");
+	exit(1);
 }
 
 int
@@ -261,8 +262,6 @@ main(int argc, char **argv)
 				break;
 			default:
 				usage();
-				exit(1);
-				break;
 		}
 	}
 

usr.sbin/ip6addrctl/ip6addrctl.c

@@ -62,7 +62,7 @@ struct policyqueue {
 TAILQ_HEAD(policyhead, policyqueue);
 static struct policyhead policyhead;
 
-static void usage(void);
+static void usage(void) __dead2;
 static void get_policy(void);
 static void dump_policy(void);
 static int mask2plen(struct sockaddr_in6 *);

usr.sbin/jail/jail.c

@@ -73,7 +73,7 @@ static void print_jail(FILE *fp, struct cfjail *j, int oldcl, int running);
 static void print_param(FILE *fp, const struct cfparam *p, int sep, int doname);
 static void show_jails(void);
 static void quoted_print(FILE *fp, char *str);
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct permspec perm_sysctl[] = {
     { "security.jail.set_hostname_allowed", KP_ALLOW_SET_HOSTNAME, 0 },

usr.sbin/ndp/ndp.c

@@ -138,7 +138,7 @@ static int delete(char *);
 static int dump(struct sockaddr_in6 *, int);
 static struct in6_nbrinfo *getnbrinfo(struct in6_addr *, int, int);
 static int ndp_ether_aton(char *, u_char *);
-static void usage(void);
+static void usage(void) __dead2;
 static void ifinfo(char *, int, char **);
 static void rtrlist(void);
 static void plist(void);

usr.sbin/newsyslog/newsyslog.c

@@ -281,7 +281,7 @@ static struct conf_entry *init_entry(const char *fname,
 		struct conf_entry *src_entry);
 static void parse_args(int argc, char **argv);
 static int parse_doption(const char *doption);
-static void usage(void);
+static void usage(void) __dead2;
 static int log_trim(const char *logname, const struct conf_entry *log_ent);
 static int age_old_log(const char *file);
 static void savelog(char *from, char *to);

usr.sbin/nfsdumpstate/nfsdumpstate.c

@@ -56,7 +56,7 @@ __FBSDID("$FreeBSD$");
 
 static void dump_lockstate(char *);
 static void dump_openstate(void);
-static void usage(void);
+static void usage(void) __dead2;
 static char *open_flags(uint32_t);
 static char *deleg_flags(uint32_t);
 static char *lock_flags(uint32_t);

usr.sbin/nfsrevoke/nfsrevoke.c

@@ -57,7 +57,7 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <unistd.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char **argv)

usr.sbin/nscd/nscd.c

@@ -85,7 +85,7 @@ static void process_socket_event(struct kevent *, struct runtime_env *,
 static void process_timer_event(struct kevent *, struct runtime_env *,
 	struct configuration *);
 static void *processing_thread(void *);
-static void usage(void);
+static void usage(void) __dead2;
 
 void get_time_func(struct timeval *);
 

usr.sbin/nvram/nvram.c

@@ -41,7 +41,7 @@
 
 #define	DEVICE_NAME	(_PATH_DEV "powermac_nvram")
 
-static void usage(void);
+static void usage(void) __dead2;
 static int remove_var(uint8_t *, int, const char *);
 static int append_var(uint8_t *, int, const char *, const char *);