[PATCH] libstdc++: Use _GLIBCXX_USE_BUILTIN_TRAIT for _Nth_type

[Patrick Palka]

Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

-- >8 --

Since _Nth_type has a fallback native implementation, use
_GLIBCXX_USE_BUILTIN_TRAIT when deciding whether __type_pack_element
is available so that we can easily toggle which implementation
to use.

libstdc++-v3/ChangeLog:

        * include/bits/utility.h (_Nth_type): Use
        _GLIBCXX_USE_BUILTIN_TRAIT instead of __has_builtin.
---
 libstdc++-v3/include/bits/utility.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/utility.h 
b/libstdc++-v3/include/bits/utility.h
index 45d7241da9f..d8a5fb960fe 100644
--- a/libstdc++-v3/include/bits/utility.h
+++ b/libstdc++-v3/include/bits/utility.h
@@ -225,7 +225,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #endif // C++17
 
-#if __has_builtin(__type_pack_element)
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__type_pack_element)
   template<size_t _Np, typename... _Types>
     struct _Nth_type
     { using type = __type_pack_element<_Np, _Types...>; };
-- 
2.43.0.283.ga54a84b333