+#ifdef POSIX_SIGNALS
+ sigemptyset (&blocked);
+#ifdef SIGCHLD
+ sigaddset (&blocked, SIGCHLD);
+#endif
+#ifdef HAVE_VFORK
+ /* On many hosts (e.g. Solaris 2.4), if a vforked child calls `signal',
+ this sets the parent's signal handlers as well as the child's.
+ So delay all interrupts whose handlers the child might munge,
+ and record the current handlers so they can be restored later. */
+ sigaddset (&blocked, SIGINT ); sigaction (SIGINT , 0, &sigint_action );
+ sigaddset (&blocked, SIGQUIT); sigaction (SIGQUIT, 0, &sigquit_action);
+#ifdef AIX
+ sigaddset (&blocked, SIGHUP ); sigaction (SIGHUP , 0, &sighup_action );
+#endif
+#endif /* HAVE_VFORK */
+ sigprocmask (SIG_BLOCK, &blocked, &procmask);
+#else /* !POSIX_SIGNALS */