Re: [PATCH] Remove matherr, and SVID and X/Open math library configurations

Corinna Vinschen <[email protected]> Wed, 23 Jan 2019 10:35:30 +0100
Newsgroups	gmane.comp.lib.newlib
Message-ID	<[email protected]>
On Jan 22 17:27, Craig Howland wrote:
> On 1/22/19 3:51 PM, Jozef Lawrynowicz wrote:
> > ...
> > I've attached the original patch (0001-*), but also 3 further patches which
> > make some additional improvements to the float math functions.
> > 
> > 0002-Newlib-Remove-HUGE_VAL-definition-from-libm-math-fun.patch
> > This patch removes the definitions of HUGE_VAL from some of the float math
> > functions. HUGE_VAL is defined in newlib/libc/include/math.h, so it is not
> > necessary to have a further definition in the math functions.
> > 
> > 0003-Newlib-Use-HUGE_VALF-instead-of-HUGE_VAL-in-single-p.patch
> > This patch replaces instances of "(float).*HUGE_VAL" with a direct usage of
> > HUGE_VALF, which is also defined in math.h.
> > 
> > 0004-Newlib-Use-nanf-instead-of-nan-in-single-precision-f.patch
> > This patch further reduces code size for a few single-precision float math
> > functions, by using nanf() instead of nan() where required.
> > 
> > I've regtested the patches with the GCC testsuite for arm-unknown-eabi, and I
> > built Cygwin and regtested it with "make check".
> > 
> > Thanks,
> > Jozef
>      The tgamma() return values don't match the POSIX recommendation.  This
> is not really the fault of this patch, but the patch is propagating mistakes
> in the existing __kernel_standard() function (in k_standard.c).  POSIX
> defines a domain error for negative integers, with errno=EDOM return NAN. 
> This case is identified by value 41 to __kernel_standard(), except that it
> is also grouped with the case of tgamma(0).  tgamma(+-0) is a pole error,
> errno=ERANGE return +-HUGE_VAL, with the sign matching the argument.  In
> addition, an overflow error (value 40 to __kernel_standard()) is supposed to
> match the sign. That is, the existing implementation has several mistakes in
> it which are being propagated in the revised implementation.  Put another
> way, there are 3 different error classes, yet __kernel_standard() only has 2
> that are used by tgamma().
>      Speaking of the __kernel_standard() function, it really would best be
> deleted.  It is only called from tgamma() and tgammaf(), and could therefore
> stand a very large pruning, at the least.  But rather than that, just
> getting rid of it seems to be in order because the entire purpose behind
> __kernel_standard() appears to be related to the matherr stuff being
> deleted, and fixing the aforementioned tgamma() return-value problems would
> be more easily done within the functions than expanding __kernel_standard(),
> anyway.
>      These comments are really about existing flaws and not flaws in this
> patch, but it does seem a good opportunity to take care of them.

Are you going to patch this?


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat
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