libbb: use _exit, not exit, in bb_daemonize_or_rexec()

By the time we reach exit in parent, child already exited or execed.
We should not re-run libc cleanup code.

While at it, introduce bb_daemon_helper() and add a few comments.

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

1 files changed, 8 insertions, 2 deletions

diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 98512bb00..f84e678b5 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -209,6 +209,9 @@ pid_t FAST_FUNC fork_or_rexec(char **argv)
         /* Maybe we are already re-execed and come here again? */
         if (re_execed)
                 return 0;
+
+        /* fflush_all(); ? - so far all callers had no buffered output to flush */
+
         pid = xvfork();
         if (pid) /* parent */
                 return pid;
@@ -245,8 +248,11 @@ void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
                 fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
 
         if (!(flags & DAEMON_ONLY_SANITIZE)) {
+
+                /* fflush_all(); - add it in fork_or_rexec() if necessary */
+
                 if (fork_or_rexec(argv))
-                        exit(EXIT_SUCCESS); /* parent */
+                        _exit(EXIT_SUCCESS); /* parent */
                 /* if daemonizing, detach from stdio & ctty */
                 setsid();
                 dup2(fd, 0);
@@ -258,7 +264,7 @@ void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
                          * Prevent this: stop being a session leader.
                          */
                         if (fork_or_rexec(argv))
-                                exit(EXIT_SUCCESS); /* parent */
+                                _exit(EXIT_SUCCESS); /* parent */
                 }
         }
         while (fd > 2) {