Date: Mon, 10 Apr 2000 20:50:02 -0700 (PDT) From: Kevin Day <toasty@dragondata.com> To: freebsd-bugs@FreeBSD.org Subject: Re: i386/17914: float-to-double core dump on 3.4R Message-ID: <200004110350.UAA44113@freefall.freebsd.org>
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The following reply was made to PR i386/17914; it has been noted by GNATS.
From: Kevin Day <toasty@dragondata.com>
To: aa8vb@ipass.net
Cc: FreeBSD-gnats-submit@FreeBSD.ORG
Subject: Re: i386/17914: float-to-double core dump on 3.4R
Date: Mon, 10 Apr 2000 22:47:51 -0500 (CDT)
> #include <float.h>
>
> main()
> {
> float f = FLT_MAX;
> double d;
> f = f * 2;
> d = f;
> }
>
> Delete the "d=f" line and it doesn't core. Put it in and it does
> (floating-point exception).
>
> From this it appears there may be a bug in the float-to-double
> promotion when f is Inf (or, at least I'd expect that f is Inf).
>
> Note that the core dump does not occur when the Inf is generated,
> but only when it is promoted to a double.
>
> I first noticed this by trying to printf the value of f after f=f*2
> and got the same core-dump behavior (due to float-to-double arg
> promotion).
See 'man setfpmask'. The default behavior in 3.4 was to cause a SIGFPE if
you do anything that causes an 'overflow' to be generated from the FPU. I
admit this is weird that it's doing it here, but I don't claim to understand
what happens in a case like this. :)
(4.0 and higher changed their defaults to ignore certain exceptions)
Kevin
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