libbb: introduce bb_signals and bb_signals_recursive,

which sets same handler for many signals. sig_catch is nuked
(bb_signals_recursive is more descriptive name).
*: use them as appropriate. 

function                                             old     new   delta
bb_signals_recursive                                   -      95     +95
bb_signals                                             -      52     +52
run_command                                          258     273     +15
svlogd_main                                         1368    1377      +9
runsv_main                                          1746    1752      +6
runsvdir_main                                       1643    1646      +3
UNSPEC_print                                          64      66      +2
time_main                                           1128    1127      -1
...
resize_main                                          246     210     -36
sig_catch                                             63       -     -63
set_fatal_sighandler                                  85      14     -71
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 5/24 up/down: 182/-548)        Total: -366 bytes

6 files changed, 31 insertions, 20 deletions

diff --git a/networking/dnsd.c b/networking/dnsd.c
index 5e7886167..0a5278377 100644
--- a/networking/dnsd.c
+++ b/networking/dnsd.c
@@ -361,14 +361,16 @@ int dnsd_main(int argc, char **argv)
         dnsentryinit();
 
         signal(SIGINT, interrupt);
-        /* why? signal(SIGPIPE, SIG_IGN); */
-        signal(SIGHUP, SIG_IGN);
+        bb_signals(0
+                /* why? + (1 << SIGPIPE) */
+                + (1 << SIGHUP)
 #ifdef SIGTSTP
-        signal(SIGTSTP, SIG_IGN);
+                + (1 << SIGTSTP)
 #endif
 #ifdef SIGURG
-        signal(SIGURG, SIG_IGN);
+                + (1 << SIGURG)
 #endif
+                , SIG_IGN);
 
         lsa = xdotted2sockaddr(listen_interface, port);
         udps = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0);
diff --git a/networking/nc_bloaty.c b/networking/nc_bloaty.c
index 206c5e5d9..853577aef 100644
--- a/networking/nc_bloaty.c
+++ b/networking/nc_bloaty.c
@@ -683,14 +683,18 @@ int nc_main(int argc, char **argv)
         PTR_TO_GLOBALS = xzalloc(sizeof(G));
 
         /* catch a signal or two for cleanup */
-        signal(SIGINT, catch);
-        signal(SIGQUIT, catch);
-        signal(SIGTERM, catch);
+        bb_signals(0
+                + (1 << SIGINT)
+                + (1 << SIGQUIT)
+                + (1 << SIGTERM)
+                , catch);
         /* and suppress others... */
+        bb_signals(0
 #ifdef SIGURG
-        signal(SIGURG, SIG_IGN);
+                + (1 << SIGURG)
 #endif
-        signal(SIGPIPE, SIG_IGN); /* important! */
+                + (1 << SIGPIPE) /* important! */
+                , SIG_IGN);
 
         proggie = argv;
         while (*++proggie) {
diff --git a/networking/sendmail.c b/networking/sendmail.c
index 63305d149..fa995abf4 100644
--- a/networking/sendmail.c
+++ b/networking/sendmail.c
@@ -111,8 +111,10 @@ static void launch_helper(const char **argv)
                 _exit(127);
         }
         // parent - check whether child is alive
-        sig_catch(SIGCHLD, signal_handler);
-        sig_catch(SIGALRM, signal_handler);
+        bb_signals_recursive(0
+                        + (1 << SIGCHLD)
+                        + (1 << SIGALRM)
+                        , signal_handler);
         signal_handler(SIGCHLD);
         // child seems OK -> parent goes on
 }
diff --git a/networking/slattach.c b/networking/slattach.c
index 17df4fa9e..e501d82e1 100644
--- a/networking/slattach.c
+++ b/networking/slattach.c
@@ -175,10 +175,12 @@ int slattach_main(int argc, char **argv)
 
         /* Trap signals in order to restore tty states upon exit */
         if (!(opt & OPT_e_quit)) {
-                signal(SIGHUP, sig_handler);
-                signal(SIGINT, sig_handler);
-                signal(SIGQUIT, sig_handler);
-                signal(SIGTERM, sig_handler);
+                bb_signals(0
+                        + (1 << SIGHUP)
+                        + (1 << SIGINT)
+                        + (1 << SIGQUIT)
+                        + (1 << SIGTERM)
+                        , sig_handler);
         }
 
         /* Open tty */
diff --git a/networking/telnetd.c b/networking/telnetd.c
index 962e5cc7b..0bffa9700 100644
--- a/networking/telnetd.c
+++ b/networking/telnetd.c
@@ -279,8 +279,7 @@ make_new_session(
         setsid();
 
         /* Restore default signal handling */
-        signal(SIGCHLD, SIG_DFL);
-        signal(SIGPIPE, SIG_DFL);
+        bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
 
         /* open the child's side of the tty. */
         /* NB: setsid() disconnects from any previous ctty's. Therefore
diff --git a/networking/udhcp/signalpipe.c b/networking/udhcp/signalpipe.c
index 918abd02d..1486b3b2d 100644
--- a/networking/udhcp/signalpipe.c
+++ b/networking/udhcp/signalpipe.c
@@ -42,9 +42,11 @@ void udhcp_sp_setup(void)
         close_on_exec_on(signal_pipe.rd);
         close_on_exec_on(signal_pipe.wr);
         ndelay_on(signal_pipe.wr);
-        signal(SIGUSR1, signal_handler);
-        signal(SIGUSR2, signal_handler);
-        signal(SIGTERM, signal_handler);
+        bb_signals(0
+                + (1 << SIGUSR1)
+                + (1 << SIGUSR2)
+                + (1 << SIGTERM)
+                , signal_handler);
 }