[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

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-05-07
            Summary|error: redefinition of      |[9 Regression] error:
                   |'constexpr long double      |redefinition of 'constexpr
                   |std::abs(long double)'      |long double std::abs(long
                   |                            |double)'
     Ever confirmed|0                           |1

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes it woud have been broken by r259813 and this should fix it:

--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -342,7 +342,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __is_floating_point_helper<long double>
     : public true_type { };

-#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
+#if !defined(__STRICT_ANSI__) && _GLIBCXX_USE_FLOAT128
   template<>
     struct __is_floating_point_helper<__float128>
     : public true_type { };