[gcc r16-2191] libstdc++: Always treat __float128 as a floating-point type

[Jonathan Wakely]

https://gcc.gnu.org/g:25ea539b3de7bb94481eb07cb7d621a3a88de727

commit r16-2191-g25ea539b3de7bb94481eb07cb7d621a3a88de727
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jul 2 21:16:30 2025 +0100

    libstdc++: Always treat __float128 as a floating-point type
    
    Similar to the previous commit that made is_integral_v<__int128>
    unconditionally true, this makes is_floating_point_v<__float128>
    unconditionally true. With the new extended floating-point types in
    C++23 (std::float64_t etc.) it seems unhelpful for is_floating_point_v
    to be true for them, but not for __float128. Especially as it is true on
    some targets, because __float128 is just a typedef for long double.
    
    This change makes is_floating_point_v<__float128> true whenever the type
    is defined, giving less surprising and more portable behaviour.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/cpp_type_traits.h (__is_floating<__float128>):
            Do not depend on __STRICT_ANSI__.
            * include/bits/stl_algobase.h (__size_to_integer(__float128)):
            Likewise.
            * include/std/type_traits (__is_floating_point_helper<__float128>):
            Likewise.
    
    Reviewed-by: Patrick Palka <ppalka@redhat.com>

Diff:
---
 libstdc++-v3/include/bits/cpp_type_traits.h | 9 +++++++++
 libstdc++-v3/include/bits/stl_algobase.h    | 2 +-
 libstdc++-v3/include/std/type_traits        | 2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
index 770ad94b3b4d..38cea4c67b76 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -313,6 +313,15 @@ __INT_N(__int128)
       typedef __true_type __type;
     };
 
+#ifdef _GLIBCXX_USE_FLOAT128
+  template<>
+    struct __is_floating<__float128>
+    {
+      enum { __value = 1 };
+      typedef __true_type __type;
+    };
+#endif
+
 #ifdef __STDCPP_FLOAT16_T__
   template<>
     struct __is_floating<_Float16>
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index 71ef2335a311..b104ec2536a0 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -1065,7 +1065,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
   __size_to_integer(double __n) { return (long long)__n; }
   inline _GLIBCXX_CONSTEXPR long long
   __size_to_integer(long double __n) { return (long long)__n; }
-#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
+#ifdef _GLIBCXX_USE_FLOAT128
   __extension__ inline _GLIBCXX_CONSTEXPR long long
   __size_to_integer(__float128 __n) { return (long long)__n; }
 #endif
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index e88d04e44d76..78a5ee8c0eb4 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -532,7 +532,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public true_type { };
 #endif
 
-#if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
+#ifdef _GLIBCXX_USE_FLOAT128
   template<>
     struct __is_floating_point_helper<__float128>
     : public true_type { };