1 // Implementation of INVOKE -*- C++ -*-
2
3 // Copyright (C) 2016-2023 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file include/bits/invoke.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{functional}
28 */
29
30 #ifndef _GLIBCXX_INVOKE_H
31 #define _GLIBCXX_INVOKE_H 1
32
33 #pragma GCC system_header
34
35 #if __cplusplus < 201103L
36 # include <bits/c++0x_warning.h>
37 #else
38
39 #include <type_traits>
40 #include <bits/move.h> // forward
41
42 namespace std _GLIBCXX_VISIBILITY(default)
43 {
44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
45
46 /**
47 * @addtogroup utilities
48 * @{
49 */
50
51 // Used by __invoke_impl instead of std::forward<_Tp> so that a
52 // reference_wrapper is converted to an lvalue-reference.
53 template<typename _Tp, typename _Up = typename __inv_unwrap<_Tp>::type>
54 constexpr _Up&&
55 __invfwd(typename remove_reference<_Tp>::type& __t) noexcept
56 { return static_cast<_Up&&>(__t); }
57
58 template<typename _Res, typename _Fn, typename... _Args>
59 constexpr _Res
60 __invoke_impl(__invoke_other, _Fn&& __f, _Args&&... __args)
61 { return std::forward<_Fn>(__f)(std::forward<_Args>(__args)...); }
62
63 template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
64 constexpr _Res
65 __invoke_impl(__invoke_memfun_ref, _MemFun&& __f, _Tp&& __t,
66 _Args&&... __args)
67 { return (__invfwd<_Tp>(__t).*__f)(std::forward<_Args>(__args)...); }
68
69 template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
70 constexpr _Res
71 __invoke_impl(__invoke_memfun_deref, _MemFun&& __f, _Tp&& __t,
72 _Args&&... __args)
73 {
74 return ((*std::forward<_Tp>(__t)).*__f)(std::forward<_Args>(__args)...);
75 }
76
77 template<typename _Res, typename _MemPtr, typename _Tp>
78 constexpr _Res
79 __invoke_impl(__invoke_memobj_ref, _MemPtr&& __f, _Tp&& __t)
80 { return __invfwd<_Tp>(__t).*__f; }
81
82 template<typename _Res, typename _MemPtr, typename _Tp>
83 constexpr _Res
84 __invoke_impl(__invoke_memobj_deref, _MemPtr&& __f, _Tp&& __t)
85 { return (*std::forward<_Tp>(__t)).*__f; }
86
87 /// Invoke a callable object.
88 template<typename _Callable, typename... _Args>
89 constexpr typename __invoke_result<_Callable, _Args...>::type
90 __invoke(_Callable&& __fn, _Args&&... __args)
91 noexcept(__is_nothrow_invocable<_Callable, _Args...>::value)
92 {
93 using __result = __invoke_result<_Callable, _Args...>;
94 using __type = typename __result::type;
95 using __tag = typename __result::__invoke_type;
96 return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
97 std::forward<_Args>(__args)...);
98 }
99
100 #if __cplusplus >= 201703L
101 // INVOKE<R>: Invoke a callable object and convert the result to R.
102 template<typename _Res, typename _Callable, typename... _Args>
103 constexpr enable_if_t<is_invocable_r_v<_Res, _Callable, _Args...>, _Res>
104 __invoke_r(_Callable&& __fn, _Args&&... __args)
105 noexcept(is_nothrow_invocable_r_v<_Res, _Callable, _Args...>)
106 {
107 using __result = __invoke_result<_Callable, _Args...>;
108 using __type = typename __result::type;
109 using __tag = typename __result::__invoke_type;
110 if constexpr (is_void_v<_Res>)
111 std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
112 std::forward<_Args>(__args)...);
113 else
114 return std::__invoke_impl<__type>(__tag{},
115 std::forward<_Callable>(__fn),
116 std::forward<_Args>(__args)...);
117 }
118 #else // C++11 or C++14
119 // This is a non-SFINAE-friendly std::invoke_r<R>(fn, args...) for C++11/14.
120 // It's used in std::function, std::bind, and std::packaged_task. Only
121 // std::function is constrained on is_invocable_r, but that is checked on
122 // construction so doesn't need to be checked again when calling __invoke_r.
123 // Consequently, these __invoke_r overloads do not check for invocable
124 // arguments, nor check that the invoke result is convertible to R.
125
126 // INVOKE<R>: Invoke a callable object and convert the result to R.
127 template<typename _Res, typename _Callable, typename... _Args>
128 constexpr __enable_if_t<!is_void<_Res>::value, _Res>
129 __invoke_r(_Callable&& __fn, _Args&&... __args)
130 {
131 using __result = __invoke_result<_Callable, _Args...>;
132 using __type = typename __result::type;
133 #if __has_builtin(__reference_converts_from_temporary)
134 static_assert(!__reference_converts_from_temporary(_Res, __type),
135 "INVOKE<R> must not create a dangling reference");
136 #endif
137 using __tag = typename __result::__invoke_type;
138 return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
139 std::forward<_Args>(__args)...);
140 }
141
142 // INVOKE<R> when R is cv void
143 template<typename _Res, typename _Callable, typename... _Args>
144 _GLIBCXX14_CONSTEXPR __enable_if_t<is_void<_Res>::value, _Res>
145 __invoke_r(_Callable&& __fn, _Args&&... __args)
146 {
147 using __result = __invoke_result<_Callable, _Args...>;
148 using __type = typename __result::type;
149 using __tag = typename __result::__invoke_type;
150 std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
151 std::forward<_Args>(__args)...);
152 }
153 #endif // C++11 or C++14
154
155 _GLIBCXX_END_NAMESPACE_VERSION
156 } // namespace std
157
158 #endif // C++11
159
160 #endif // _GLIBCXX_INVOKE_H