| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef _LIBCPP___TYPE_TRAITS_IS_EQUAILITY_COMPARABLE_H |
| #define _LIBCPP___TYPE_TRAITS_IS_EQUAILITY_COMPARABLE_H |
| |
| #include <__config> |
| #include <__type_traits/integral_constant.h> |
| #include <__type_traits/is_integral.h> |
| #include <__type_traits/is_same.h> |
| #include <__type_traits/is_void.h> |
| #include <__type_traits/remove_cv.h> |
| #include <__type_traits/remove_cvref.h> |
| #include <__type_traits/void_t.h> |
| #include <__utility/declval.h> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| template <class _Tp, class _Up, class = void> |
| struct __is_equality_comparable : false_type {}; |
| |
| template <class _Tp, class _Up> |
| struct __is_equality_comparable<_Tp, _Up, __void_t<decltype(std::declval<_Tp>() == std::declval<_Up>())> > : true_type { |
| }; |
| |
| // A type is_trivially_equality_comparable if the expression `a == b` is equivalent to `std::memcmp(&a, &b, sizeof(T))` |
| // (with `a` and `b` being of type `T`). For the case where we compare two object of the same type, we can use |
| // __is_trivially_equality_comparable. We have special-casing for pointers which point to the same type ignoring |
| // cv-qualifications and comparing to void-pointers. |
| // |
| // The following types are not trivially equality comparable: |
| // floating-point types: different bit-patterns can compare equal. (e.g 0.0 and -0.0) |
| // enums: The user is allowed to specialize operator== for enums |
| // pointers that don't have the same type (ignoring cv-qualifiers): pointers to virtual bases are equality comparable, |
| // but don't have the same bit-pattern. An exception to this is comparing to a void-pointer. There the bit-pattern is |
| // always compared. |
| |
| template <class _Tp, class _Up> |
| struct __libcpp_is_trivially_equality_comparable_impl : false_type {}; |
| |
| template <class _Tp> |
| struct __libcpp_is_trivially_equality_comparable_impl<_Tp, _Tp> |
| #if __has_builtin(__is_trivially_equality_comparable) |
| : integral_constant<bool, __is_trivially_equality_comparable(_Tp) && __is_equality_comparable<_Tp, _Tp>::value> { |
| }; |
| #else |
| : is_integral<_Tp> { |
| }; |
| #endif // __has_builtin(__is_trivially_equality_comparable) |
| |
| template <class _Tp> |
| struct __libcpp_is_trivially_equality_comparable_impl<_Tp*, _Tp*> : true_type {}; |
| |
| // TODO: Use is_pointer_inverconvertible_base_of |
| template <class _Tp, class _Up> |
| struct __libcpp_is_trivially_equality_comparable_impl<_Tp*, _Up*> |
| : integral_constant< |
| bool, |
| __is_equality_comparable<_Tp*, _Up*>::value && |
| (is_same<__remove_cv_t<_Tp>, __remove_cv_t<_Up> >::value || is_void<_Tp>::value || is_void<_Up>::value)> { |
| }; |
| |
| template <class _Tp, class _Up> |
| using __libcpp_is_trivially_equality_comparable = |
| __libcpp_is_trivially_equality_comparable_impl<__remove_cv_t<_Tp>, __remove_cv_t<_Up> >; |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___TYPE_TRAITS_IS_EQUAILITY_COMPARABLE_H |