1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H
11#define _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H
12
13#include <__config>
14#include <__iterator/concepts.h>
15
16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17#  pragma GCC system_header
18#endif
19
20_LIBCPP_BEGIN_NAMESPACE_STD
21
22#if _LIBCPP_STD_VER >= 20
23
24struct unreachable_sentinel_t {
25  template <weakly_incrementable _Iter>
26  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(unreachable_sentinel_t, const _Iter&) noexcept {
27    return false;
28  }
29};
30
31inline constexpr unreachable_sentinel_t unreachable_sentinel{};
32
33#endif // _LIBCPP_STD_VER >= 20
34
35_LIBCPP_END_NAMESPACE_STD
36
37#endif // _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H
38