v3/utility/addressof.hpp

0001 // Range v3 library
0002 //
0003 //  Copyright Eric Niebler 2013-present
0004 //
0005 //  Use, modification and distribution is subject to the
0006 //  Boost Software License, Version 1.0. (See accompanying
0007 //  file LICENSE_1_0.txt or copy at
0008 //  http://www.boost.org/LICENSE_1_0.txt)
0009 //
0010 // Project home: https://github.com/ericniebler/range-v3
0011 //
0012 #ifndef RANGES_V3_UTILITY_ADDRESSOF_HPP
0013 #define RANGES_V3_UTILITY_ADDRESSOF_HPP
0014
0015 #include <memory>
0016 #include <type_traits>
0017
0018 #include <concepts/concepts.hpp>
0019
0020 #include <range/v3/range_fwd.hpp>
0021
0022 #include <range/v3/detail/config.hpp>
0023
0024 #include <range/v3/detail/prologue.hpp>
0025
0026 namespace ranges
0027 {
0028     /// \cond
0029     namespace detail
0030     {
0031 #ifdef __cpp_lib_addressof_constexpr
0032         using std::addressof;
0033 #else
0034         namespace check_addressof
0035         {
0036             inline ignore_t operator&(ignore_t)
0037             {
0038                 return {};
0039             }
0040             template<typename T>
0041             auto addressof(T & t)
0042             {
0043                 return &t;
0044             }
0045         } // namespace check_addressof
0046
0047         template<typename T>
0048         constexpr bool has_bad_addressof()
0049         {
0050             return !std::is_scalar<T>::value &&
0051                    !RANGES_IS_SAME(decltype(check_addressof::addressof(*(T *)nullptr)),
0052                                    ignore_t);
0053         }
0054
0055         template(typename T)(
0056             requires(has_bad_addressof<T>()))
0057         T * addressof(T & arg) noexcept
0058         {
0059             return std::addressof(arg);
0060         }
0061
0062         template(typename T)(
0063             requires (!has_bad_addressof<T>()))
0064         constexpr T * addressof(T & arg) noexcept
0065         {
0066             return &arg;
0067         }
0068
0069         template<typename T>
0070         T const * addressof(T const &&) = delete;
0071 #endif
0072     } // namespace detail
0073     /// \endcond
0074 } // namespace ranges
0075
0076 #include <range/v3/detail/epilogue.hpp>
0077
0078 #endif