*: stop using atexit in non-debug build: saves ~260 in bss with musl

"builtin" below is atexit's 32-element global array of functions to call.

function                                             old     new   delta
top_main                                             879     889     +10
launch_helper                                        185     193      +8
powertop_main                                       1555    1559      +4
sed_main                                             651     650      -1
slot                                                   4       -      -4
call                                                   4       -      -4
atexit                                                23       -     -23
kill_helper                                           31       -     -31
__funcs_on_exit                                      120       -    -120
__cxa_atexit                                         168       -    -168
builtin                                              260       -    -260
------------------------------------------------------------------------------
(add/remove: 0/8 grow/shrink: 3/1 up/down: 22/-611)          Total: -589 bytes
   text	   data	    bss	    dec	    hex	filename
 912364	    563	   6132	 919059	  e0613	busybox_old
 912035	    563	   5844	 918442	  e03aa	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

4 files changed, 16 insertions, 22 deletions

diff --git a/editors/sed.c b/editors/sed.c
index f68f44724..3fc40ceef 100644
--- a/editors/sed.c
+++ b/editors/sed.c
@@ -1521,7 +1521,7 @@ int sed_main(int argc UNUSED_PARAM, char **argv)
         //argc -= optind;
         argv += optind;
         if (opt & OPT_in_place) { // -i
-                atexit(cleanup_outname);
+                die_func = cleanup_outname;
         }
         if (opt & (2|4))
                 G.regex_type |= REG_EXTENDED; // -r or -E
diff --git a/mailutils/mail.c b/mailutils/mail.c
index a7e43c0d1..eceb89071 100644
--- a/mailutils/mail.c
+++ b/mailutils/mail.c
@@ -6,23 +6,15 @@
  *
  * Licensed under GPLv2, see file LICENSE in this source tree.
  */
+#include <sys/prctl.h>
 #include "libbb.h"
 #include "mail.h"
 
-static void kill_helper(void)
-{
-        if (G.helper_pid > 0) {
-                kill(G.helper_pid, SIGTERM);
-                G.helper_pid = 0;
-        }
-}
-
 // generic signal handler
 static void signal_handler(int signo)
 {
 #define err signo
         if (SIGALRM == signo) {
-                kill_helper();
                 bb_error_msg_and_die("timed out");
         }
 
@@ -66,16 +58,15 @@ void FAST_FUNC launch_helper(const char **argv)
         // child stdout [1] -> parent stdin [0]
 
         if (!G.helper_pid) {
-                // child: try to execute connection helper
+                // child
+                // if parent dies, get SIGTERM
+                prctl(PR_SET_PDEATHSIG, SIGTERM, 0, 0, 0);
+                // try to execute connection helper
                 // NB: SIGCHLD & SIGALRM revert to SIG_DFL on exec
                 BB_EXECVP_or_die((char**)argv);
         }
 
-        // parent
-        // check whether child is alive
-        //redundant:signal_handler(SIGCHLD);
-        // child seems OK -> parent goes on
-        atexit(kill_helper);
+        // parent goes on
 }
 
 char* FAST_FUNC send_mail_command(const char *fmt, const char *param)
diff --git a/procps/powertop.c b/procps/powertop.c
index ebd659bdb..5d522bf91 100644
--- a/procps/powertop.c
+++ b/procps/powertop.c
@@ -8,11 +8,6 @@
  *
  * Licensed under GPLv2, see file LICENSE in this source tree.
  */
-
-//applet:IF_POWERTOP(APPLET(powertop, BB_DIR_USR_SBIN, BB_SUID_DROP))
-
-//kbuild:lib-$(CONFIG_POWERTOP) += powertop.o
-
 //config:config POWERTOP
 //config:       bool "powertop (9.1 kb)"
 //config:       default y
@@ -27,6 +22,10 @@
 //config:       Without this, powertop will only refresh display every 10 seconds.
 //config:       No keyboard commands will work, only ^C to terminate.
 
+//applet:IF_POWERTOP(APPLET(powertop, BB_DIR_USR_SBIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_POWERTOP) += powertop.o
+
 // XXX This should be configurable
 #define ENABLE_FEATURE_POWERTOP_PROCIRQ 1
 
@@ -718,7 +717,7 @@ int powertop_main(int UNUSED_PARAM argc, char UNUSED_PARAM **argv)
         set_termios_to_raw(STDIN_FILENO, &G.init_settings, TERMIOS_CLEAR_ISIG);
         bb_signals(BB_FATAL_SIGS, sig_handler);
         /* So we don't forget to reset term settings */
-        atexit(reset_term);
+        die_func = reset_term;
 #endif
 
         /* Collect initial data */
@@ -855,6 +854,9 @@ int powertop_main(int UNUSED_PARAM argc, char UNUSED_PARAM **argv)
         } /* for (;;) */
 
         bb_putchar('\n');
+#if ENABLE_FEATURE_POWERTOP_INTERACTIVE
+        reset_term();
+#endif
 
         return EXIT_SUCCESS;
 }
diff --git a/procps/top.c b/procps/top.c
index b9958afa0..f97ded5d6 100644
--- a/procps/top.c
+++ b/procps/top.c
@@ -1146,6 +1146,7 @@ int top_main(int argc UNUSED_PARAM, char **argv)
         else {
                 /* Turn on unbuffered input; turn off echoing, ^C ^Z etc */
                 set_termios_to_raw(STDIN_FILENO, &initial_settings, TERMIOS_CLEAR_ISIG);
+                die_func = reset_term;
         }
 
         bb_signals(BB_FATAL_SIGS, sig_catcher);