Date: Sun, 10 Apr 2005 11:43:30 -0700 From: Bakul Shah <bakul@BitBlocks.com> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-current@freebsd.org Subject: Re: smbfs bug introduced at smbfs_vnops.c:1.58 Message-ID: <200504101843.j3AIhUh0046427@gate.bitblocks.com> In-Reply-To: Your message of "Mon, 11 Apr 2005 03:55:31 %2B1000." <20050411032601.S55302@delplex.bde.org>
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> A similar example with "double a;" is more interesting. This also
> gives undefined behaviour (C99 6.5.5[#5]). However, this is bogus if
> there is a floating point infinity. C99 has support for IEEE floating
> point and it is clearly intended that the behaviour of 1.0/0.0 is to
> give +Inf and raise the divide-by-zero exception, but I couldn't see
> anywhere in the C99 draft n869.txt where this is spelled out (raising of
> the divide-by-zero exception is spelled out for lots of math functions
> but doesn't seem to be mentioned for plain division).
This is indirectly spelled out in draft n2764.txt in annex F:
F.3 Operators and functions
[#1] C operators and functions provide IEC 60559 required
and recommended facilities as listed below.
-- The +, -, *, and / operators provide the IEC 60559 add,
subtract, multiply, and divide operations.
IEC 60599 (aka IEEE754) clearly states the behavior for
divide by zero. 6.5.5 does say x/0 is undefined but if
__STDC_IEC_559__ is defined then IEEE behavior is expected.
I haven't checked gassy-c (gcc) for conformance.
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