From owner-freebsd-arch  Fri Jan 11 12: 5:13 2002
Delivered-To: freebsd-arch@freebsd.org
Received: from avocet.prod.itd.earthlink.net (avocet.mail.pas.earthlink.net [207.217.120.50])
	by hub.freebsd.org (Postfix) with ESMTP id 89DBC37B400
	for <arch@freebsd.org>; Fri, 11 Jan 2002 12:05:06 -0800 (PST)
Received: from pool0189.cvx21-bradley.dialup.earthlink.net ([209.179.192.189] helo=mindspring.com)
	by avocet.prod.itd.earthlink.net with esmtp (Exim 3.33 #1)
	id 16P7ux-0005xW-00; Fri, 11 Jan 2002 12:04:47 -0800
Message-ID: <3C3F455B.86856045@mindspring.com>
Date: Fri, 11 Jan 2002 12:04:43 -0800
From: Terry Lambert <tlambert2@mindspring.com>
X-Mailer: Mozilla 4.7 [en]C-CCK-MCD {Sony}  (Win98; U)
X-Accept-Language: en
MIME-Version: 1.0
To: Bruce Evans <bde@zeta.org.au>
Cc: Nate Williams <nate@yogotech.com>,
	Daniel Eischen <eischen@pcnet1.pcnet.com>,
	Dan Eischen <eischen@vigrid.com>, Peter Wemm <peter@wemm.org>,
	Archie Cobbs <archie@dellroad.org>, Alfred Perlstein <bright@mu.org>,
	arch@FreeBSD.ORG
Subject: Re: Request for review: getcontext, setcontext, etc
References: <20020112054041.J3330-100000@gamplex.bde.org>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-freebsd-arch@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-arch.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-arch>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-arch>
X-Loop: FreeBSD.ORG

Bruce Evans wrote:
> On Fri, 11 Jan 2002, Nate Williams wrote:
> > > > > > Why is reporting a SIGFPE considered broken?  This is a valid exception,
> > > > > > and it should be reported.
> > > > >
> > > > > Because the SIGFPE is for the broken context-switching code and not for
> > > > > the program.
> > > >
> > > > Ok, let's try again.  How can I make sure that a SIGFPE that occur due
> > > > to a FPU operation is properly reported using fsave/frestor?
> > >
> > > The set of such proper reports is null, so it is easily generated by not
> > > using fsave (sic) or frstor.
> >
> > Huh?  Are you saying that there are *NO* floating-point exceptions that
> > should be reported to a process?  Doesn't posix require that exceptions
> > be thrown.
> 
> I'm not saying any more, since I have made negative progress attempting
> to explain this.


In other words, SIGFPE is about as trappable as SIGBUS or SIGILL,
and means about the same thing: an unrecoverable fault.

If you think about it a little, since you can't guarantee delivery
of signals to particular threads anyway, it makes sense that SIGFPE
would not be useful under any circumstances in threaded programs,
no matter how you sliced it.

-- Terry

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message