Re: [boost] [trippels-ppc64le][math] Missing quadmath.h errors

Subject: Re: [boost] [trippels-ppc64le][math] Missing quadmath.h errors
From: Markus Trippelsdorf (markus_at_[hidden])
Date: 2015-11-16 07:53:01

On 2015.11.16 at 15:33 +0300, Andrey Semashev wrote:
> On 2015-11-16 14:47, John Maddock wrote:
> >
> >
> >On 16/11/2015 10:48, Andrey Semashev wrote:
> >>Hi,
> >>
> >>I'm seeing some test failures on the trippels-powerpc64le-gcc-6.0
> >>tester that amount to Boost.Math failing to build because the
> >>quadmath.h header is missing.
> >>
> >>http://www.boost.org/development/tests/develop/developer/output/trippels-powerpc64le-gcc-6-0-boost-bin-v2-libs-log-test-filt_matches_spirit_qi-test-gcc-6-0-0-release-build-no-threading-multi.html
> >>
> >>
> >>I understand that gcc 6.0 is an unreleased compiler, but the error is
> >>probably not a consequence of a compiler bug. Besides, another tester,
> >>Flast-FreeBSD10-gcc-6.0.0~gnu++11, passes. Is it possible that the
> >>header is not provided for powerpc64le? Or is an optional dependency
> >>whose presence is misdetected? Is this a known problem?
> >>
> >
> >Not a known problem, no.
> >
> >My understanding is that libquadmath is an integral part of GCC, and I
> >see that BOOST_HAS_FLOAT128 is defined for that platform - and that's
> >predicated on _GLIBCXX_USE_FLOAT128 so __float128 appears to be
> >supported?  The GCC manual is a little unclear to me when this is
> >supposed to be supported:
> >https://gcc.gnu.org/onlinedocs/gcc/Floating-Types.html.
> >
> >What happens on that platform with older (released) compilers?
> 
> I really don't know as I don't have access to a PPC machine. But after
> installing gcc 5.2.1 cross-compilers for ppc64le, aarch64, armhf on my local
> Kubuntu I couldn't find quadmath.h for these architectures - only the x86
> and x86_64 ones. Also, the release notes for gcc 4.6 [1] only mention x86,
> x86-64 and Itanium as the platforms that support libquadmath. Looking at the
> gcc package build scripts in Ubuntu there's definitely some special casing
> regarding quadmath for these architectures: ia64 i386 i486 i586 i686 amd64.
> 
> My understanding is that gcc may support __float128 type, which probably
> includes only the arithmetic/relational operators. libquadmath implements
> math functions for these types (sin, cos, etc.), and it may not support the
> architecture where gcc supports __float128. So it has to be detected
> separately.
> 
> I would suggest using __has_include when possible and hard-locking to x86,
> x86-64 and IA64 when not.

Please see: https://gcc.gnu.org/wiki/Ieee128PowerPC

(I run the trippels-powerpc64le-gcc-6.0 tests.)

-- 
Markus