Date: Fri, 11 Jan 2002 13:08:13 -0700 From: Nate Williams <nate@yogotech.com> To: Terry Lambert <tlambert2@mindspring.com> Cc: Bruce Evans <bde@zeta.org.au>, 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 Message-ID: <15423.17965.472722.218250@caddis.yogotech.com> In-Reply-To: <3C3F455B.86856045@mindspring.com> References: <20020112054041.J3330-100000@gamplex.bde.org> <3C3F455B.86856045@mindspring.com>
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> > > > > > > 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. It correctly works in single threaded programs in FreeBSD 2.2, but not in 4.4. > 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. What Bruce is saying is that it's not possible to deliver the signal *AT ALL*, let alone in threaded programs. However, he contradicts his own statements in later parts of the same email, hence the confusion. Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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