From owner-freebsd-current@FreeBSD.ORG  Wed May 28 08:36:56 2003
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 2C30E37B401
	for <freebsd-current@freebsd.org>;
	Wed, 28 May 2003 08:36:56 -0700 (PDT)
Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16])
	by mx1.FreeBSD.org (Postfix) with ESMTP id C9F0A43FA3
	for <freebsd-current@freebsd.org>;
	Wed, 28 May 2003 08:36:54 -0700 (PDT)	(envelope-from bde@zeta.org.au)
Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246])
	by mailman.zeta.org.au (8.9.3p2/8.8.7) with ESMTP id BAA10949;
	Thu, 29 May 2003 01:36:31 +1000
Date: Thu, 29 May 2003 01:36:29 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
X-X-Sender: bde@gamplex.bde.org
To: Terry Lambert <tlambert2@mindspring.com>
In-Reply-To: <3ED3804B.DC65E10A@mindspring.com>
Message-ID: <20030529011400.A1228@gamplex.bde.org>
References: <200305201025.30296.jlido@goof.com>
	<20030522093623.30915ed0.fearow@attbi.com>
	<20030527200208.L1802@gamplex.bde.org>
	<3ED3804B.DC65E10A@mindspring.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: freebsd-current@freebsd.org
Subject: Re: gcc/libm floating-point bug?
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 28 May 2003 15:36:56 -0000

On Tue, 27 May 2003, Terry Lambert wrote:

> BTW: signal stacks are irrelevent; technically, you are not
> allowed to do floating point in signal handlers anyway.  8-).

Not true.  Signal handlers can do almost anything with local variables.
The main relevant restrictions on them is that they must not access
any static or global variables (other than write-only accesses to
objects whose type is volatile sig_atomic_t) or call any functions
that might make such accesses (which rules out calling most functions
including everything in libm).  These restrictions (and bugs) just
make doing floating in signal handlers not very useful.  Doing significant
floating point calculations in signal handlers might involve duplicating
functions from libm inline or as signal-safe private functions.
Outputting the results or otherwise influencing the world might involve
converting the results to arrays of bits and assigning the bits to
sig_atomic_t objects for later interpretation.

Bruce