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To: Mike Pritchard <mpp@freefall.freebsd.org>
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Subject: Re: docs/3047 & cvs commit: src/lib/libc/sys sigaction.2 
In-reply-to: Your message of "Mon, 24 Mar 97 19:41:41 PST."
             <199703250341.TAA08216@freefall.freebsd.org> 
Date: Tue, 25 Mar 1997 09:45:58 PST
From: Bill Fenner <fenner@parc.xerox.com>
Message-Id: <97Mar25.094606pst.177486@crevenia.parc.xerox.com>
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> Change the description of how attempts to block SIGKILL and SIGSTOP
> are handled.  The system call will actually fail in this case - the
> system doesn't silently ignore the request.  Closes PR# 3047

Um, if this is what you took from my wording then I did an even poorer
job than the man page did.

All I meant was that the antecedent of "This" in the second sentence
of

NOTE
     The mask specified in act is not allowed to block SIGKILL or SIGSTOP.
     This is done silently by the system.

is potentially unclear.  The first time I read this man page I thought
the antecedent was "block SIGKILL [and] SIGSTOP", e.g. "the system
silently blocks SIGKILL [and] SIGSTOP".  The real meaning (and an
alternative reading of the same sentence) is "the system silently
ignores attempts to block SIGKILL or SIGSTOP"; I just wanted to make
that sentence less ambiguous.

Attempting to block SIGKILL and SIGSTOP is not an error and is silently
ignored by the system.  Everything else that the system call is
attempting to do succeeds.  (At least, this is what POSIX says, and
this is what 2.2 does).

(While writing my test program to make absolutely sure, I noticed that the
first line should probably read "The mask specified in the sa_mask field"
or something similar, too...)

  Bill