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.bin/elfctl/elfctl.c

@@ -56,7 +56,7 @@ static bool edit_file_features(Elf *, int, int, char *, bool);
 static bool get_file_features(Elf *, int, int, uint32_t *, uint64_t *, bool);
 static void print_features(void);
 static bool print_file_features(Elf *, int, int, char *, bool);
-static void usage(void);
+static void usage(void) __dead2;
 
 struct ControlFeatures {
 	const char *alias;

usr.bin/elfdump/elfdump.c

@@ -473,7 +473,7 @@ static void elf_print_got(Elf32_Ehdr *e, void *sh);
 static void elf_print_hash(Elf32_Ehdr *e, void *sh);
 static void elf_print_note(Elf32_Ehdr *e, void *sh);
 
-static void usage(void);
+static void usage(void) __dead2;
 
 /*
  * Helpers for ELF files with shnum or shstrndx values that don't fit in the

usr.bin/env/env.c

@@ -62,7 +62,7 @@ extern char **environ;
 
 int	 env_verbosity;
 
-static void usage(void);
+static void usage(void) __dead2;
 
 /*
  * Exit codes.

usr.bin/find/main.c

@@ -71,7 +71,7 @@ int mindepth = -1, maxdepth = -1; /* minimum and maximum depth */
 int regexp_flags = REG_BASIC;	/* use the "basic" regexp by default*/
 int exitstatus;
 
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.bin/finger/finger.c

@@ -98,7 +98,7 @@ int invoker_root = 0;
 
 static void loginlist(void);
 static int option(int, char **);
-static void usage(void);
+static void usage(void) __dead2;
 static void userlist(int, char **);
 
 static int

usr.bin/fold/fold.c

@@ -61,7 +61,7 @@ __FBSDID("$FreeBSD$");
 
 void fold(int);
 static int newpos(int, wint_t);
-static void usage(void);
+static void usage(void) __dead2;
 
 static int bflag;		/* Count bytes, not columns */
 static int sflag;		/* Split on word boundaries */

usr.bin/fortune/strfile/strfile.c

@@ -126,7 +126,7 @@ static int stable_collate_range_cmp(int, int);
 static void do_order(void);
 static void getargs(int, char **);
 static void randomize(void);
-static void usage(void);
+static void usage(void) __dead2;
 
 /*
  * main:

usr.bin/from/from.c

@@ -54,7 +54,7 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 
 static int match(const char *, const char *);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char **argv)

usr.bin/grdc/grdc.c

@@ -43,7 +43,7 @@ static void set(int, int);
 static void standt(int);
 static void movto(int, int);
 static void sighndl(int);
-static void usage(void);
+static void usage(void) __dead2;
 
 static void
 sighndl(int signo)

usr.bin/head/head.c

@@ -71,7 +71,7 @@ __FBSDID("$FreeBSD$");
 static void head(FILE *, intmax_t);
 static void head_bytes(FILE *, off_t);
 static void obsolete(char *[]);
-static void usage(void);
+static void usage(void) __dead2;
 
 static const struct option long_opts[] =
 {

usr.bin/join/join.c

@@ -114,7 +114,7 @@ static void outoneline(INPUT *, LINE *);
 static void outtwoline(INPUT *, LINE *, INPUT *, LINE *);
 static void slurp(INPUT *);
 static wchar_t *towcs(const char *);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.bin/ktrace/ktrace.c

@@ -67,7 +67,7 @@ static int pid;
 
 static void no_ktrace(int);
 static void set_pid_clear(const char *, enum clear);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.bin/ktrdump/ktrdump.c

@@ -53,7 +53,7 @@ __FBSDID("$FreeBSD$");
 #define	USAGE \
 	"usage: ktrdump [-cflqrtH] [-i ktrfile] [-M core] [-N system] [-o outfile]\n"
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct nlist nl[] = {
 	{ .n_name = "_ktr_version" },

usr.bin/leave/leave.c

@@ -52,7 +52,7 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 
 static void doalarm(u_int);
-static void usage(void);
+static void usage(void) __dead2;
 
 /*
  * leave [[+]hhmm]

usr.bin/limits/limits.c

@@ -257,7 +257,7 @@ static struct {
 #define RCS_STRING  "tfdscmlunbvpwko"
 
 static rlim_t resource_num(int which, int ch, const char *str);
-static void usage(void);
+static void usage(void) __dead2;
 static int getshelltype(void);
 static void print_limit(rlim_t limit, unsigned divisor, const char *inf,
 			const char *pfx, const char *sfx, const char *which);

usr.bin/lock/lock.c

@@ -81,7 +81,7 @@ __FBSDID("$FreeBSD$");
 static void quit(int);
 static void bye(int);
 static void hi(int);
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct timeval	timeout;
 static struct timeval	zerotime;

usr.bin/lockf/lockf.c

@@ -44,7 +44,7 @@ static int acquire_lock(const char *name, int flags);
 static void cleanup(void);
 static void killed(int sig);
 static void timeout(int sig);
-static void usage(void);
+static void usage(void) __dead2;
 static void wait_for_lock(const char *name);
 
 static const char *lockname;

usr.bin/look/look.c

@@ -89,7 +89,7 @@ static int	 look(wchar_t *, unsigned char *, unsigned char *);
 static wchar_t	*prepkey(const char *, wchar_t);
 static void	 print_from(wchar_t *, unsigned char *, unsigned char *);
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static struct option longopts[] = {
 	{ "alternative",no_argument,	NULL, 'a' },