Date: Fri, 9 Jan 2009 08:57:26 -0700 From: John Hein <jhein@timing.com> To: =?UTF-8?B?VsOhY2xhdiBIYWlzbWFu?= <v.haisman@sh.cvut.cz> Cc: freebsd-standards@FreeBSD.ORG, das@FreeBSD.ORG, freebsd-gnats-submit@FreeBSD.ORG, imp@FreeBSD.ORG Subject: Re: standards/130067: Wrong numeric limits in system headers? Message-ID: <18791.29670.321788.799095@gromit.timing.com> In-Reply-To: <496676AB.9040905@sh.cvut.cz> References: <200812302231.mBUMVUtf092910@www.freebsd.org> <20081231215445.S3923@delplex.bde.org> <20090106190313.GA15233@zim.MIT.EDU> <496676AB.9040905@sh.cvut.cz>
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V=E1clav Haisman wrote at 22:56 +0100 on Jan 8, 2009: > David Schultz wrote, On 6.1.2009 20:03: > > On FreeBSD/i386, long doubles are represented with 64 bits of > > precision, but computations are performed with 53 bits of > > precision. In a sane world, this discrepancy wouldn't exist, but > > for reasons I won't get into, they do, and probably always will. > > = > > C99 defines the LDBL constants based on what can be represented, > > not what can be computed as the result of arithmetic operations, > > so my interpretation is that the values in float.h are correct, > > though confusing. > I am not language lawyer but even if it were true that the constants a= re > right, there is still the problem that they (especially the LDBL_MAX v= alue) > are useless with the provided GCC. Either GCC or the headers should be= > changed. Otherwise the constants are rather useless and unusable. FWIW, when you compile the OP's sample code on i386 with -pedantic (with 6.x's base gcc 3.4.6 or 7.x's base gcc 4.2.1), you get: x.cc:11: error: floating constant exceeds range of 'long double' (the LDBL_MAX line) That seems to tip the scale more to the 'float.h is wrong' side.
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