convert all command handlers to variadic functions

Resolves dozens of: warning: passing arguments to a function without a
  prototype is deprecated in all versions of C and is not supported in C2x

In traditional C the empty argument list () indicates that a function
accepts an arbitrary amount of arguments of arbitary types. A function
which takes no arguments must be declared with a (void) prototype instead.

nsh has been making elaborate use of this feature by defining command handlers
with () and passing arbitrary arguments to handlers depending on the use case.
This coding style is not future-proof. In C++, () means "no arguments", the
same as (void), and clang is now warning about this C feature going away in
C2x, aligning C with C++.

Make nsh future-proof by using variadic function prototypes (...) instead
of () prototypes. Every handler now uses (int argc, char **argv, ...) as
prototype: the argument count, an argument vector, followed by arbitrary
arguments which can be extracted using the va_arg(3) function from stdarg.h.
The variadic part of the argument list can be used to pass arguments of types
other than char * without needing to convert them to strings and back.

Using () as function prototype defeats type-checking done by the compiler,
and the same is true for variadic arguments. We still need to manually make
sure that the correct amount and types of arguments are passed in the variadic
part of the handler's argument list.

Many handlers already use the argument count + argument vector approach and
do not need internal changes, just a new prototype.
Some handlers now require use of va_start/va_arg/va_end to access additional
arguments. For example, the interfaces handlers were passing an interface
name and file descriptor before the argument count/vector. The order of
arguments is now swapped, such that interface name and file descriptor get
passed as part of the variable argument list.

Testing + OK Tom

arp.c

@@ -160,7 +160,7 @@ rtget(struct sockaddr_inarp **sinp, struct sockaddr_dl **sdlp,
  * Set an individual arp entry
  */
 int
-arpset(int argc, char *argv[])
+arpset(int argc, char *argv[], ...)
 {
 	struct sockaddr_inarp *sin;
 	struct sockaddr_dl *sdl;

bgpnsh/bgpnsh.c

@@ -74,7 +74,7 @@ Menu showlist[] = {
 };
 
 static int
-showcmd(int argc, char **argv)
+showcmd(int argc, char **argv, ...)
 {
 	Menu *s;	/* pointer to current command */
 
@@ -106,7 +106,7 @@ showcmd(int argc, char **argv)
 }
 
 int
-quit(void)
+quit(int argc, char **argv, ...)
 {
 	printf("%% Session terminated.\n");
 	exit(0);

bridge.c

@@ -29,6 +29,7 @@
 #include <stdio.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <stdarg.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <sys/param.h>
@@ -115,10 +116,18 @@ static struct brc brps[] = {
 };
 
 int
-brport(char *ifname, int ifs, int argc, char **argv)
+brport(int argc, char **argv, ...)
 {
 	int set, i;
 	struct brc *x;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -222,12 +231,20 @@ static struct brc brvs[] = {
 };
 
 int
-brval(char *ifname, int ifs, int argc, char **argv)
+brval(int argc, char **argv, ...)
 {
 	int set;
 	u_int32_t val = 0;
 	const char *errmsg = NULL;
 	struct brc *x;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -323,8 +340,17 @@ brval(char *ifname, int ifs, int argc, char **argv)
 }
 
 int
-brrule(char *ifname, int ifs, int argc, char **argv)
+brrule(int argc, char **argv, ...)
 {
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
+
 	if (NO_ARG(argv[0])) {
 		printf("%% all rules for a member must be applied in order\n");
 		printf("%% use flush bridge-rules <bridge> <member>\n");
@@ -345,9 +371,17 @@ brrule(char *ifname, int ifs, int argc, char **argv)
 }
 
 int
-brstatic(char *ifname, int ifs, int argc, char **argv)
+brstatic(int argc, char **argv, ...)
 {
 	int set;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -387,11 +421,19 @@ static struct brd brds[] = {
 };
 
 int
-brpri(char *ifname, int ifs, int argc, char **argv)
+brpri(int argc, char **argv, ...)
 {
 	int set, val;
 	const char *errmsg = NULL;
 	struct brd *x;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -469,10 +511,16 @@ brpri(char *ifname, int ifs, int argc, char **argv)
  * flush wrappers here
  */
 int
-flush_bridgedyn(char *brdg)
+flush_bridgedyn(int argc, char **argv, ...)
 {
+	va_list ap;
+	char *brdg;
 	int ifs;
 
+	va_start(ap, argv);
+	brdg = va_arg(ap, char *);
+	va_end (ap);
+
 	ifs = socket(AF_INET, SOCK_DGRAM, 0);
 	if (ifs < 0) {
 		printf("%% socket: %s\n", strerror(errno));
@@ -492,10 +540,16 @@ flush_bridgedyn(char *brdg)
 }
 
 int
-flush_bridgeall(char *brdg)
+flush_bridgeall(int argc, char **argv, ...)
 {
+	va_list ap;
+	char *brdg;
 	int ifs;
 
+	va_start(ap, argv);
+	brdg = va_arg(ap, char *);
+	va_end(ap);
+
 	ifs = socket(AF_INET, SOCK_DGRAM, 0);
 	if (ifs < 0) {
 		printf("%% socket: %s\n", strerror(errno));
@@ -515,10 +569,17 @@ flush_bridgeall(char *brdg)
 }
 
 int
-flush_bridgerule(char *brdg, char *member)
+flush_bridgerule(int argc, char **argv, ...)
 {
+	va_list ap;
+	char *brdg, *member;
 	int ifs;
 
+	va_start(ap, argv);
+	brdg = va_arg(ap, char *);
+	member = va_arg(ap, char *);
+	va_end(ap);
+
 	ifs = socket(AF_INET, SOCK_DGRAM, 0);
 	if (ifs < 0) {
 		printf("%% socket: %s\n", strerror(errno));
@@ -1625,9 +1686,17 @@ brprotect_usage(void)
 }
 
 int
-brprotect(char *ifname, int ifs, int argc, char **argv)
+brprotect(int argc, char **argv, ...)
 {
 	int set;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -1755,7 +1824,7 @@ show_bridge(char *ifname)
 }
 
 int
-show_bridges(int argc, char **argv)
+show_bridges(int argc, char **argv, ...)
 {
 	switch (argc) {
 	case 2:

carp.c

@@ -16,6 +16,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include <string.h>
 #include <errno.h>
 #include <sys/limits.h>
@@ -46,13 +47,21 @@ static struct intc {
 static const char *carp_bal_modes[] = { CARP_BAL_MODES };
 
 int
-intcarp(char *ifname, int ifs, int argc, char **argv)
+intcarp(int argc, char **argv, ...)
 {
 	const char *errmsg = NULL;
 	struct ifreq ifr;
 	struct carpreq creq;
 	int set, bal_mode = 0, val = 0;
 	struct intc *x;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -196,11 +205,19 @@ intcarp(char *ifname, int ifs, int argc, char **argv)
 }
 
 int
-intcpass(char *ifname, int ifs, int argc, char **argv)
+intcpass(int argc, char **argv, ...)
 {
 	struct ifreq ifr;
 	struct carpreq creq;
 	int set;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -238,13 +255,21 @@ intcpass(char *ifname, int ifs, int argc, char **argv)
 }
 
 int
-intcnode(char *ifname, int ifs, int argc, char **argv)
+intcnode(int argc, char **argv, ...)
 {
 	struct ifreq ifr;
 	struct carpreq creq;
 	const char *errmsg = NULL;
 	int set, i, last;
 	u_int vhid, advskew;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;
@@ -428,11 +453,19 @@ carp_state(int s, char *ifname, FILE *outfile)
 }
 
 int
-intcdev(char *ifname, int ifs, int argc, char **argv)
+intcdev(int argc, char **argv, ...)
 {
 	struct ifreq ifr;
 	struct carpreq creq;
 	int set;
+	va_list ap;
+	char *ifname;
+	int ifs;
+
+	va_start(ap, argv);
+	ifname = va_arg(ap, char *);
+	ifs = va_arg(ap, int);
+	va_end(ap);
 
 	if (NO_ARG(argv[0])) {
 		set = 0;