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From: Terry Lambert <tlambert@primenet.com>
Message-Id: <199709071339.GAA06816@usr09.primenet.com>
Subject: Re: SIGCLD
To: joerg_wunsch@uriah.heep.sax.de
Date: Sun, 7 Sep 1997 13:39:17 +0000 (GMT)
Cc: freebsd-hackers@FreeBSD.ORG, jamil@counterintelligence.ml.org
In-Reply-To: <19970907091757.ST01979@uriah.heep.sax.de> from "J Wunsch" at Sep 7, 97 09:17:57 am
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> By explicitly setting the signal handler to SIG_IGN, you tell the system
> that you aren't interested in the death of your child, and you won't
> get zombies.
> 
> This of course is a terrible crock, but was the only way to express
> this in SVR3.  SVR4 and Posix use the option SA_NOCLDWAIT in
> sigaction(2) to express this wish.  FreeBSD doesn't implement this
> option (yet).

Are you sure about this?  The only POSIX defined SA_ flag I know about
is SA_NOCLDSTOP, which prevents SIGCHLD when child processes are stopped,
but still generates it for child process death.

While we are on the subject, SA_NODEFER is kind of wierd, and BSDI
compatability is impossible with SA_DISABLE being 0x0004 on BSDI
(which disables the taking of signals on an alternate stack).  I
understand the need for SA_RESETHAND; it lets you use the general
underlying "POSIX + flag extensions" signal implementation to get
backward compatability with SVR3/SVR2, etc..  But shouldn't any
FreeBSD-only flags really be higher in the flag space, like the
SA_USERTRAMP?


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.