Signal Handling in System V

[katz / kowalski]

I have some questions about certain aspects of signal handling in
System V (which may be applicable to other versions).

  1).  Apparently if a process has a pending signal at the time it does
       a fork, the forked process also ends up with the same pending
       signal.  Is this result intentional and if so, why would anyone
       want signals to work this way, i.e., how is this useful?

   2). What is the safest way to ensure that a child process starts out
       "fresh" relative to signals (assuming sigset is used)?  One
       sequence which I believe should work is:

       (in parent)

	 sighold(sig);   /* to prevent the forked process from receiving
			     a signal it doesn't want */
	 fork();
	 sigrelse(sig);

       (in forked process - prior to exec)

	 signal(sig, SIG_DFL); /* to clear any pending signal and reset
				  the signal action routine. note: sigset
				  does not remove a pending signal */
	 sigrelse(sig);        /* to release any signal hold. note: signal
				  does not remove a signal hold */
	 exec(..);

       Is the preceding necessary and sufficient?

Thanks for any response.