[PATCH] PR libstdc++/84654 Do not use __float128 if it is disabled by the compiler

[Tulio Magno Quites Machado Filho]

In order to use the __float128 in C++ it's necessary to check if
it is supported in libstdc++ (i.e. via _GLIBCXX_USE_FLOAT128) and if the
compiler enabled its support too, e.g. -mfloat128 or -mno-float128.

2018-03-01 Tulio Magno Quites Machado Filho <tul...@linux.vnet.ibm.com>

        PR libstdc++/84654
        * include/bits/std_abs.h: Avoid to use __float128 when the
        compiler disabled it.
        * include/std/type_traits: Likewise.
---
 libstdc++-v3/include/bits/std_abs.h  | 3 ++-
 libstdc++-v3/include/std/type_traits | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/std_abs.h 
b/libstdc++-v3/include/bits/std_abs.h
index 6e4551d..3ad1c2b 100644
--- a/libstdc++-v3/include/bits/std_abs.h
+++ b/libstdc++-v3/include/bits/std_abs.h
@@ -96,7 +96,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   abs(__GLIBCXX_TYPE_INT_N_3 __x) { return __x >= 0 ? __x : -__x; }
 #endif
 
-#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
+#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128) \
+    && defined(__FLOAT128__)
   inline _GLIBCXX_CONSTEXPR
   __float128
   abs(__float128 __x)
diff --git a/libstdc++-v3/include/std/type_traits 
b/libstdc++-v3/include/std/type_traits
index 711d6c5..4e2e4f7 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -342,7 +342,8 @@ _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__) && defined(_GLIBCXX_USE_FLOAT128) \
+    && defined(__FLOAT128__)
   template<>
     struct __is_floating_point_helper<__float128>
     : public true_type { };
-- 
2.9.5