[libc++] Prefer __has_builtin for detecting compiler-provided type_traits

[philnik]

Summary

Both clang and GCC support using __has_builtin for detecting compiler-provided type_traits. Use it instead of __has_keyword or __has_feature to remove special-casing for GCC-provided builtins

[Mordante]

In general looks good, but I really like to see it pass all CIs. (I know the current failures aren't due to this patch.)

libcxx/include/__type_traits/is_convertible.h

32

please update the comment to match the #if, same for the #endif.

[ldionne]

LGTM, but I don't understand what's the special-casing for GCC that you mention in the commit message. Can you elaborate?

[philnik]

In D129056#3631232, @ldionne wrote:

LGTM, but I don't understand what's the special-casing for GCC that you mention in the commit message. Can you elaborate?

We've had a few __has_keyword(whatever) || _LIBCPP_COMPILER_GCC before (for example in is_trivially_destructible.h). The || _LIBCPP_COMPILER_GCC is now unnecessary, since GCC correctly reports support for builtin type traits with __has_builtin.

[Mordante]

libcxx/include/__type_traits/is_convertible.h

32

I've addressed this comment myself.

libcxx/include/__type_traits/extent.h

 #include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__array_extent)
+#if __has_builtin(__array_extent)
 
 template<class _Tp, size_t _Dim = 0>
 struct _LIBCPP_TEMPLATE_VIS extent
     : integral_constant<size_t, __array_extent(_Tp, _Dim)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp, unsigned _Ip = 0>
 inline constexpr size_t extent_v = __array_extent(_Tp, _Ip);
 #endif
 
-#else // __has_keyword(__array_extent)
+#else // __has_builtin(__array_extent)
 
 template <class _Tp, unsigned _Ip = 0> struct _LIBCPP_TEMPLATE_VIS extent
     : public integral_constant<size_t, 0> {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[], 0>
     : public integral_constant<size_t, 0> {};
 template <class _Tp, unsigned _Ip> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[], _Ip>
     : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
 template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[_Np], 0>
     : public integral_constant<size_t, _Np> {};
 template <class _Tp, size_t _Np, unsigned _Ip> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[_Np], _Ip>
     : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp, unsigned _Ip = 0>
 inline constexpr size_t extent_v = extent<_Tp, _Ip>::value;
 #endif
 
-#endif // __has_keyword(__array_extent)
+#endif // __has_builtin(__array_extent)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_EXTENT_H

libcxx/include/__type_traits/has_virtual_destructor.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_feature(has_virtual_destructor) || defined(_LIBCPP_COMPILER_GCC)
+#if __has_builtin(__has_virtual_destructor)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS has_virtual_destructor
     : public integral_constant<bool, __has_virtual_destructor(_Tp)> {};
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS has_virtual_destructor
     : public false_type {};

libcxx/include/__type_traits/is_array.h

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // TODO: Clang incorrectly reports that __is_array is true for T[0].
 //       Re-enable the branch once https://llvm.org/PR54705 is fixed.
-#if __has_keyword(__is_array) && 0
+#if __has_builtin(__is_array) && 0
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_array : _BoolConstant<__is_array(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_array_v = __is_array(_Tp);
 #endif
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_array
     : public false_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_array<_Tp[]>
     : public true_type {};
 template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS is_array<_Tp[_Np]>
     : public true_type {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_array_v = is_array<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_array)
+#endif // __has_builtin(__is_array)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_ARRAY_H

libcxx/include/__type_traits/is_assignable.h

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template<typename, typename _Tp> struct __select_2nd { typedef _LIBCPP_NODEBUG _Tp type; };
 
-#if __has_keyword(__is_assignable)
+#if __has_builtin(__is_assignable)
 
 template<class _Tp, class _Up>
 struct _LIBCPP_TEMPLATE_VIS is_assignable : _BoolConstant<__is_assignable(_Tp, _Up)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp, class _Arg>
 inline constexpr bool is_assignable_v = __is_assignable(_Tp, _Arg);
 #endif
 
-#else // __has_keyword(__is_assignable)
+#else // __has_builtin(__is_assignable)
 
 template <class _Tp, class _Arg>
 typename __select_2nd<decltype((declval<_Tp>() = declval<_Arg>())), true_type>::type
 __is_assignable_test(int);
 
 template <class, class>
 false_type __is_assignable_test(...);
 

 struct is_assignable
     : public __is_assignable_imp<_Tp, _Arg> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp, class _Arg>
 inline constexpr bool is_assignable_v = is_assignable<_Tp, _Arg>::value;
 #endif
 
-#endif // __has_keyword(__is_assignable)
+#endif // __has_builtin(__is_assignable)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H

libcxx/include/__type_traits/is_compound.h

 #include <__type_traits/is_fundamental.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_compound)
+#if __has_builtin(__is_compound)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_compound : _BoolConstant<__is_compound(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_compound_v = __is_compound(_Tp);
 #endif
 
-#else // __has_keyword(__is_compound)
+#else // __has_builtin(__is_compound)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_compound
     : public integral_constant<bool, !is_fundamental<_Tp>::value> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_compound_v = is_compound<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_compound)
+#endif // __has_builtin(__is_compound)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_COMPOUND_H

libcxx/include/__type_traits/is_const.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_const)
+#if __has_builtin(__is_const)
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_const : _BoolConstant<__is_const(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_const_v = __is_const(_Tp);
 #endif
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_const            : public false_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_const<_Tp const> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_const_v = is_const<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_const)
+#endif // __has_builtin(__is_const)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_CONST_H

libcxx/include/__type_traits/is_convertible.h

 #include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_feature(is_convertible_to) && !defined(_LIBCPP_USE_IS_CONVERTIBLE_FALLBACK)
+#if __has_builtin(__is_convertible_to) && !defined(_LIBCPP_USE_IS_CONVERTIBLE_FALLBACK)
 
 template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS is_convertible
     : public integral_constant<bool, __is_convertible_to(_T1, _T2)> {};
 
-#else  // __has_feature(is_convertible_to)
+#else  // __has_builtin(__is_convertible_to)
 
 namespace __is_convertible_imp
 {
 template <class _Tp> void  __test_convert(_Tp);
 
 template <class _From, class _To, class = void>
 struct __is_convertible_test : public false_type {};
 

 
 template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS is_convertible
     : public __is_convertible<_T1, _T2>
 {
     static const size_t __complete_check1 = __is_convertible_check<_T1>::__v;
     static const size_t __complete_check2 = __is_convertible_check<_T2>::__v;
 };
 
-#endif // __has_feature(is_convertible_to)
+#endif // __has_builtin(__is_convertible_to)
 
 #if _LIBCPP_STD_VER > 14
 template <class _From, class _To>
 inline constexpr bool is_convertible_v = is_convertible<_From, _To>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_CONVERTIBLE_H

libcxx/include/__type_traits/is_destructible.h

 #include <__utility/declval.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_destructible)
+#if __has_builtin(__is_destructible)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_destructible : _BoolConstant<__is_destructible(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_destructible_v = __is_destructible(_Tp);
 #endif
 
-#else // __has_keyword(__is_destructible)
+#else // __has_builtin(__is_destructible)
 
 //  if it's a reference, return true
 //  if it's a function, return false
 //  if it's   void,     return false
 //  if it's an array of unknown bound, return false
 //  Otherwise, return "declval<_Up&>().~_Up()" is well-formed
 //    where _Up is remove_all_extents<_Tp>::type
 

 struct is_destructible<void>
     : public false_type {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_destructible)
+#endif // __has_builtin(__is_destructible)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_DESTRUCTIBLE_H

libcxx/include/__type_traits/is_function.h

 #include <__type_traits/is_reference.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_function)
+#if __has_builtin(__is_function)
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_function : integral_constant<bool, __is_function(_Tp)> {};
 
 #else
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_function
     : public integral_constant<bool, !(is_reference<_Tp>::value || is_const<const _Tp>::value)> {};
 
-#endif // __has_keyword(__is_function)
+#endif // __has_builtin(__is_function)
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_function_v = is_function<_Tp>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_FUNCTIONAL_H

libcxx/include/__type_traits/is_fundamental.h

 #include <__type_traits/is_void.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_fundamental)
+#if __has_builtin(__is_fundamental)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_fundamental : _BoolConstant<__is_fundamental(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_fundamental_v = __is_fundamental(_Tp);
 #endif
 
-#else // __has_keyword(__is_fundamental)
+#else // __has_builtin(__is_fundamental)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_fundamental
     : public integral_constant<bool, is_void<_Tp>::value        ||
                                      __is_nullptr_t<_Tp>::value ||
                                      is_arithmetic<_Tp>::value> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_fundamental)
+#endif // __has_builtin(__is_fundamental)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_FUNDAMENTAL_H

libcxx/include/__type_traits/is_integral.h

 template <>          struct __libcpp_is_integral<unsigned long>      { enum { value = 1 }; };
 template <>          struct __libcpp_is_integral<long long>          { enum { value = 1 }; };
 template <>          struct __libcpp_is_integral<unsigned long long> { enum { value = 1 }; };
 #ifndef _LIBCPP_HAS_NO_INT128
 template <>          struct __libcpp_is_integral<__int128_t>         { enum { value = 1 }; };
 template <>          struct __libcpp_is_integral<__uint128_t>        { enum { value = 1 }; };
 #endif
 
-#if __has_keyword(__is_integral)
+#if __has_builtin(__is_integral)
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_integral : _BoolConstant<__is_integral(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_integral_v = __is_integral(_Tp);
 #endif
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_integral
     : public _BoolConstant<__libcpp_is_integral<typename remove_cv<_Tp>::type>::value> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_integral_v = is_integral<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_integral)
+#endif // __has_builtin(__is_integral)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_INTEGRAL_H

libcxx/include/__type_traits/is_member_function_pointer.h

 template <class _Tp, class _Up> struct __libcpp_is_member_pointer<_Tp _Up::*> {
   enum {
     __is_member = true,
     __is_func = is_function<_Tp>::value,
     __is_obj = !__is_func,
   };
 };
 
-#if __has_keyword(__is_member_function_pointer)
+#if __has_builtin(__is_member_function_pointer)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_member_function_pointer
     : _BoolConstant<__is_member_function_pointer(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_member_function_pointer_v = __is_member_function_pointer(_Tp);
 #endif
 
-#else // __has_keyword(__is_member_function_pointer)
+#else // __has_builtin(__is_member_function_pointer)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_function_pointer
     : public _BoolConstant< __libcpp_is_member_pointer<typename remove_cv<_Tp>::type>::__is_func > {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_member_function_pointer_v = is_member_function_pointer<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_member_function_pointer)
+#endif // __has_builtin(__is_member_function_pointer)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_MEMBER_FUNCTION_POINTER_H

libcxx/include/__type_traits/is_member_object_pointer.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_member_object_pointer)
+#if __has_builtin(__is_member_object_pointer)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_member_object_pointer
     : _BoolConstant<__is_member_object_pointer(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_member_object_pointer_v = __is_member_object_pointer(_Tp);
 #endif
 
-#else // __has_keyword(__is_member_object_pointer)
+#else // __has_builtin(__is_member_object_pointer)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_object_pointer
     : public _BoolConstant< __libcpp_is_member_pointer<typename remove_cv<_Tp>::type>::__is_obj >  {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_member_object_pointer_v = is_member_object_pointer<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_member_object_pointer)
+#endif // __has_builtin(__is_member_object_pointer)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_MEMBER_FUNCTION_POINTER_H

libcxx/include/__type_traits/is_member_pointer.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_member_pointer)
+#if __has_builtin(__is_member_pointer)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_member_pointer : _BoolConstant<__is_member_pointer(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_member_pointer_v = __is_member_pointer(_Tp);
 #endif
 
-#else // __has_keyword(__is_member_pointer)
+#else // __has_builtin(__is_member_pointer)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_pointer
  : public _BoolConstant< __libcpp_is_member_pointer<typename remove_cv<_Tp>::type>::__is_member > {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_member_pointer)
+#endif // __has_builtin(__is_member_pointer)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_MEMBER_POINTER_H

libcxx/include/__type_traits/is_nothrow_assignable.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_nothrow_assignable)
+#if __has_builtin(__is_nothrow_assignable)
 
 template <class _Tp, class _Arg>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
     : public integral_constant<bool, __is_nothrow_assignable(_Tp, _Arg)> {};
 
 #else
 
 template <bool, class _Tp, class _Arg> struct __libcpp_is_nothrow_assignable;

 };
 
 template <class _Tp, class _Arg>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
     : public __libcpp_is_nothrow_assignable<is_assignable<_Tp, _Arg>::value, _Tp, _Arg>
 {
 };
 
-#endif // _LIBCPP_HAS_NO_NOEXCEPT
+#endif // __has_builtin(__is_nothrow_assignable)
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp, class _Arg>
 inline constexpr bool is_nothrow_assignable_v = is_nothrow_assignable<_Tp, _Arg>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_NOTHROW_ASSIGNABLE_H

libcxx/include/__type_traits/is_nothrow_constructible.h

 #include <__utility/declval.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_nothrow_constructible)
+#if __has_builtin(__is_nothrow_constructible)
 
 template <class _Tp, class... _Args>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : public integral_constant<bool, __is_nothrow_constructible(_Tp, _Args...)> {};
 
 #else
 
 template <bool, bool, class _Tp, class... _Args> struct __libcpp_is_nothrow_constructible;

 };
 
 template <class _Tp, size_t _Ns>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp[_Ns]>
     : __libcpp_is_nothrow_constructible<is_constructible<_Tp>::value, is_reference<_Tp>::value, _Tp>
 {
 };
 
-#endif // _LIBCPP_HAS_NO_NOEXCEPT
+#endif // __has_builtin(__is_nothrow_constructible)
 
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp, class ..._Args>
 inline constexpr bool is_nothrow_constructible_v = is_nothrow_constructible<_Tp, _Args...>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_NOTHROW_CONSTRUCTIBLE_H

libcxx/include/__type_traits/is_object.h

 #include <__type_traits/is_union.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_object)
+#if __has_builtin(__is_object)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_object : _BoolConstant<__is_object(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_object_v = __is_object(_Tp);
 #endif
 
-#else // __has_keyword(__is_object)
+#else // __has_builtin(__is_object)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_object
     : public integral_constant<bool, is_scalar<_Tp>::value ||
                                      is_array<_Tp>::value  ||
                                      is_union<_Tp>::value  ||
                                      is_class<_Tp>::value  > {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_object_v = is_object<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_object)
+#endif // __has_builtin(__is_object)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_OBJECT_H

libcxx/include/__type_traits/is_pod.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_feature(is_pod) || defined(_LIBCPP_COMPILER_GCC)
+#if __has_builtin(__is_pod)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pod
     : public integral_constant<bool, __is_pod(_Tp)> {};
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pod
     : public integral_constant<bool, is_trivially_default_constructible<_Tp>::value   &&
                                      is_trivially_copy_constructible<_Tp>::value      &&
                                      is_trivially_copy_assignable<_Tp>::value    &&
                                      is_trivially_destructible<_Tp>::value> {};
 
-#endif
+#endif // __has_builtin(__is_pod)
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_pod_v = is_pod<_Tp>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_POD_H

libcxx/include/__type_traits/is_pointer.h

 #include <__type_traits/remove_cv.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_pointer)
+#if __has_builtin(__is_pointer)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_pointer : _BoolConstant<__is_pointer(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_pointer_v = __is_pointer(_Tp);
 #endif
 
-#else // __has_keyword(__is_pointer)
+#else // __has_builtin(__is_pointer)
 
 template <class _Tp> struct __libcpp_is_pointer       : public false_type {};
 template <class _Tp> struct __libcpp_is_pointer<_Tp*> : public true_type {};
 
 template <class _Tp> struct __libcpp_remove_objc_qualifiers { typedef _Tp type; };
 #if defined(_LIBCPP_HAS_OBJC_ARC)
 template <class _Tp> struct __libcpp_remove_objc_qualifiers<_Tp __strong> { typedef _Tp type; };
 template <class _Tp> struct __libcpp_remove_objc_qualifiers<_Tp __weak> { typedef _Tp type; };
 template <class _Tp> struct __libcpp_remove_objc_qualifiers<_Tp __autoreleasing> { typedef _Tp type; };
 template <class _Tp> struct __libcpp_remove_objc_qualifiers<_Tp __unsafe_unretained> { typedef _Tp type; };
 #endif
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pointer
     : public __libcpp_is_pointer<typename __libcpp_remove_objc_qualifiers<typename remove_cv<_Tp>::type>::type> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_pointer)
+#endif // __has_builtin(__is_pointer)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_POINTER_H

libcxx/include/__type_traits/is_reference.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_lvalue_reference) && \
-    __has_keyword(__is_rvalue_reference) && \
-    __has_keyword(__is_reference)
+#if __has_builtin(__is_lvalue_reference) && \
+    __has_builtin(__is_rvalue_reference) && \
+    __has_builtin(__is_reference)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_lvalue_reference : _BoolConstant<__is_lvalue_reference(_Tp)> { };
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_rvalue_reference : _BoolConstant<__is_rvalue_reference(_Tp)> { };
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_reference : _BoolConstant<__is_reference(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_reference_v = __is_reference(_Tp);
 template <class _Tp>
 inline constexpr bool is_lvalue_reference_v = __is_lvalue_reference(_Tp);
 template <class _Tp>
 inline constexpr bool is_rvalue_reference_v = __is_rvalue_reference(_Tp);
 #endif
 
-#else // __has_keyword(__is_lvalue_reference) && etc...
+#else // __has_builtin(__is_lvalue_reference) && etc...
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_lvalue_reference       : public false_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_lvalue_reference<_Tp&> : public true_type {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_rvalue_reference        : public false_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_rvalue_reference<_Tp&&> : public true_type {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_reference        : public false_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_reference<_Tp&>  : public true_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_reference<_Tp&&> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_reference_v = is_reference<_Tp>::value;
 
 template <class _Tp>
 inline constexpr bool is_lvalue_reference_v = is_lvalue_reference<_Tp>::value;
 
 template <class _Tp>
 inline constexpr bool is_rvalue_reference_v = is_rvalue_reference<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_lvalue_reference) && etc...
+#endif // __has_builtin(__is_lvalue_reference) && etc...
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_REFERENCE_H

libcxx/include/__type_traits/is_scalar.h

 #include <__type_traits/is_pointer.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_scalar)
+#if __has_builtin(__is_scalar)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_scalar : _BoolConstant<__is_scalar(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_scalar_v = __is_scalar(_Tp);
 #endif
 
-#else // __has_keyword(__is_scalar)
+#else // __has_builtin(__is_scalar)
 
 template <class _Tp> struct __is_block : false_type {};
 #if defined(_LIBCPP_HAS_EXTENSION_BLOCKS)
 template <class _Rp, class ..._Args> struct __is_block<_Rp (^)(_Args...)> : true_type {};
 #endif
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_scalar
     : public integral_constant<bool, is_arithmetic<_Tp>::value     ||
                                      is_member_pointer<_Tp>::value ||
                                      is_pointer<_Tp>::value        ||
                                      __is_nullptr_t<_Tp>::value    ||
                                      __is_block<_Tp>::value        ||
                                      is_enum<_Tp>::value           > {};
 
 template <> struct _LIBCPP_TEMPLATE_VIS is_scalar<nullptr_t> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_scalar)
+#endif // __has_builtin(__is_scalar)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_SCALAR_H

libcxx/include/__type_traits/is_signed.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_signed)
+#if __has_builtin(__is_signed)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_signed : _BoolConstant<__is_signed(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_signed_v = __is_signed(_Tp);
 #endif
 
-#else // __has_keyword(__is_signed)
+#else // __has_builtin(__is_signed)
 
 template <class _Tp, bool = is_integral<_Tp>::value>
 struct __libcpp_is_signed_impl : public _BoolConstant<(_Tp(-1) < _Tp(0))> {};
 
 template <class _Tp>
 struct __libcpp_is_signed_impl<_Tp, false> : public true_type {};  // floating point
 
 template <class _Tp, bool = is_arithmetic<_Tp>::value>
 struct __libcpp_is_signed : public __libcpp_is_signed_impl<_Tp> {};
 
 template <class _Tp> struct __libcpp_is_signed<_Tp, false> : public false_type {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_signed : public __libcpp_is_signed<_Tp> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_signed_v = is_signed<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_signed)
+#endif // __has_builtin(__is_signed)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_SIGNED_H

libcxx/include/__type_traits/is_standard_layout.h

 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_standard_layout
-#if __has_feature(is_standard_layout) || defined(_LIBCPP_COMPILER_GCC)
+#if __has_builtin(__is_standard_layout)
     : public integral_constant<bool, __is_standard_layout(_Tp)>
 #else
     : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value>
 #endif
     {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_standard_layout_v = is_standard_layout<_Tp>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_STANDARD_LAYOUT_H

libcxx/include/__type_traits/is_trivial.h

 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivial
-#if __has_feature(is_trivial) || defined(_LIBCPP_COMPILER_GCC)
+#if __has_builtin(__is_trivial)
     : public integral_constant<bool, __is_trivial(_Tp)>
 #else
     : integral_constant<bool, is_trivially_copyable<_Tp>::value &&
                                  is_trivially_default_constructible<_Tp>::value>
 #endif
     {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_trivial_v = is_trivial<_Tp>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_TRIVIAL_H

libcxx/include/__type_traits/is_trivially_destructible.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_trivially_destructible)
+#if __has_builtin(__is_trivially_destructible)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public integral_constant<bool, __is_trivially_destructible(_Tp)> {};
 
-#elif __has_feature(has_trivial_destructor) || defined(_LIBCPP_COMPILER_GCC)
+#elif __has_builtin(__has_trivial_destructor)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public integral_constant<bool, is_destructible<_Tp>::value && __has_trivial_destructor(_Tp)> {};
 
 #else
 
 template <class _Tp> struct __libcpp_trivial_destructor
     : public integral_constant<bool, is_scalar<_Tp>::value ||
                                      is_reference<_Tp>::value> {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible<_Tp[]>
     : public false_type {};
 
-#endif
+#endif // __has_builtin(__is_trivially_destructible)
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_trivially_destructible_v = is_trivially_destructible<_Tp>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_TRIVIALLY_DESTRUCTIBLE_H

libcxx/include/__type_traits/is_unsigned.h

 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // Before AppleClang 14, __is_unsigned returned true for enums with signed underlying type.
-#if __has_keyword(__is_unsigned) && !(defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER < 1400)
+#if __has_builtin(__is_unsigned) && !(defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER < 1400)
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_unsigned : _BoolConstant<__is_unsigned(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_unsigned_v = __is_unsigned(_Tp);
 #endif
 
-#else // __has_keyword(__is_unsigned)
+#else // __has_builtin(__is_unsigned)
 
 template <class _Tp, bool = is_integral<_Tp>::value>
 struct __libcpp_is_unsigned_impl : public _BoolConstant<(_Tp(0) < _Tp(-1))> {};
 
 template <class _Tp>
 struct __libcpp_is_unsigned_impl<_Tp, false> : public false_type {};  // floating point
 
 template <class _Tp, bool = is_arithmetic<_Tp>::value>
 struct __libcpp_is_unsigned : public __libcpp_is_unsigned_impl<_Tp> {};
 
 template <class _Tp> struct __libcpp_is_unsigned<_Tp, false> : public false_type {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_unsigned : public __libcpp_is_unsigned<_Tp> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_unsigned_v = is_unsigned<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_unsigned)
+#endif // __has_builtin(__is_unsigned)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_UNSIGNED_H

libcxx/include/__type_traits/is_void.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_void)
+#if __has_builtin(__is_void)
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_void : _BoolConstant<__is_void(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_void_v = __is_void(_Tp);
 #endif
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_void
     : public is_same<typename remove_cv<_Tp>::type, void> {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_void_v = is_void<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_void)
+#endif // __has_builtin(__is_void)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_VOID_H

libcxx/include/__type_traits/is_volatile.h

 #include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if __has_keyword(__is_volatile)
+#if __has_builtin(__is_volatile)
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_volatile : _BoolConstant<__is_volatile(_Tp)> { };
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_volatile_v = __is_volatile(_Tp);
 #endif
 
 #else
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_volatile               : public false_type {};
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_volatile<_Tp volatile> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
 inline constexpr bool is_volatile_v = is_volatile<_Tp>::value;
 #endif
 
-#endif // __has_keyword(__is_volatile)
+#endif // __has_builtin(__is_volatile)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_IS_VOLATILE_H