fix signal handling in varnishtop and varnishhist

Using vut->last_sighup was not adequate, because the VUT_Main loop might
have terminated for some other signal or because of EOF.

On the other hand, we do not want to end the curses loop just because
the VUT_Main loop has ended in order to continue to display the last
state (and maybe the EOF in the top right corner).

So while I see that checking just one flag has some beauty to it, I do
think that directly checking the signal counters is both simple and
robust.

Fixes #3088 for varnishtop and varnishhist

bin/varnishhist/varnishhist.c

@@ -53,6 +53,7 @@
 #include "vas.h"
 #include "vut.h"
 #include "vtim.h"
+#include "vapi/vsig.h"
 
 #define HIST_N 2000		/* how far back we remember */
 #define HIST_RES 100		/* bucket resolution */
@@ -131,8 +132,6 @@ static const struct profile profiles[] = {
 
 static const struct profile *active_profile;
 
-static volatile sig_atomic_t quit = 0;
-
 static void
 update(void)
 {
@@ -384,7 +383,7 @@ do_curses(void *arg)
 	intrflush(stdscr, FALSE);
 	curs_set(0);
 	erase();
-	while (!quit && !vut->last_sighup) {
+	while (!VSIG_int && !VSIG_term && !VSIG_hup) {
 		AZ(pthread_mutex_lock(&mtx));
 		update();
 		AZ(pthread_mutex_unlock(&mtx));
@@ -413,7 +412,6 @@ do_curses(void *arg)
 		case 'Q':
 		case 'q':
 			AZ(raise(SIGINT));
-			quit = 1;
 			break;
 		case '0':
 		case '1':

bin/varnishtop/varnishtop.c

@@ -54,6 +54,7 @@
 #include "vas.h"
 #include "vtree.h"
 #include "vut.h"
+#include "vapi/vsig.h"
 
 #if 0
 #define AC(x) assert((x) != ERR)
@@ -82,8 +83,6 @@ static int f_flag = 0;
 static unsigned maxfieldlen = 0;
 static const char *ident;
 
-static volatile sig_atomic_t quit = 0;
-
 static VRBT_HEAD(t_order, top) h_order = VRBT_INITIALIZER(&h_order);
 static VRBT_HEAD(t_key, top) h_key = VRBT_INITIALIZER(&h_key);
 
@@ -257,7 +256,7 @@ do_curses(void *arg)
 	(void)curs_set(0);
 	AC(erase());
 	timeout(1000);
-	while (!quit && !vut->last_sighup) {
+	while (!VSIG_int && !VSIG_term && !VSIG_hup) {
 		AZ(pthread_mutex_lock(&mtx));
 		update(period);
 		AZ(pthread_mutex_unlock(&mtx));
@@ -284,7 +283,6 @@ do_curses(void *arg)
 		case 'Q':
 		case 'q':
 			AZ(raise(SIGINT));
-			quit = 1;
 			break;
 		default:
 			AC(beep());