[Bug libstdc++/85672] [9 Regression] error: redefinition of 'constexpr long double std::abs(long double)'

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85672

--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue Jul 31 09:38:28 2018
New Revision: 263084

URL: https://gcc.gnu.org/viewcvs?rev=263084&root=gcc&view=rev
Log:
PR libstdc++/84654 Disable __float128 specializations for -mno-float128

Backport from mainline
2018-05-08  Jonathan Wakely  <jwakely@redhat.com>

        PR libstdc++/85672
        * include/Makefile.am [!ENABLE_FLOAT128]: Change c++config.h entry
        to #undef _GLIBCXX_USE_FLOAT128 instead of defining it to zero.
        * include/Makefile.in: Regenerate.
        * include/bits/c++config (_GLIBCXX_USE_FLOAT128): Move definition
        within conditional block.

Backport from mainline
2018-05-01  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>

        PR libstdc++/84654
        * acinclude.m4: Set ENABLE_FLOAT128 instead of _GLIBCXX_USE_FLOAT128.
        * config.h.in: Remove references to _GLIBCXX_USE_FLOAT128.
        * configure: Regenerate.
        * include/Makefile.am: Replace the value of _GLIBCXX_USE_FLOAT128
        based on ENABLE_FLOAT128.
        * include/Makefile.in: Regenerate.
        * include/bits/c++config: Define _GLIBCXX_USE_FLOAT128.
        [!defined(__FLOAT128__) && !defined(__SIZEOF_FLOAT128__)]: Undefine
        _GLIBCXX_USE_FLOAT128.

Modified:
    branches/gcc-8-branch/libstdc++-v3/ChangeLog
    branches/gcc-8-branch/libstdc++-v3/acinclude.m4
    branches/gcc-8-branch/libstdc++-v3/config.h.in
    branches/gcc-8-branch/libstdc++-v3/configure
    branches/gcc-8-branch/libstdc++-v3/include/Makefile.am
    branches/gcc-8-branch/libstdc++-v3/include/Makefile.in
    branches/gcc-8-branch/libstdc++-v3/include/bits/c++config