Automatic date update in version.in
[binutils-gdb.git] / gdbsupport / traits.h
blob6487cb9d5c19e3e4a08975b97e9124c29e52be12
1 /* Copyright (C) 2017-2022 Free Software Foundation, Inc.
3 This file is part of GDB.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 #ifndef COMMON_TRAITS_H
19 #define COMMON_TRAITS_H
21 #include <type_traits>
23 /* GCC does not understand __has_feature. */
24 #if !defined(__has_feature)
25 # define __has_feature(x) 0
26 #endif
28 /* HAVE_IS_TRIVIALLY_COPYABLE is defined as 1 iff
29 std::is_trivially_copyable is available. GCC only implemented it
30 in GCC 5. */
31 #if (__has_feature(is_trivially_copyable) \
32 || (defined __GNUC__ && __GNUC__ >= 5))
33 # define HAVE_IS_TRIVIALLY_COPYABLE 1
34 #endif
36 /* HAVE_IS_TRIVIALLY_CONSTRUCTIBLE is defined as 1 iff
37 std::is_trivially_constructible is available. GCC only implemented it
38 in GCC 5. */
39 #if (__has_feature(is_trivially_constructible) \
40 || (defined __GNUC__ && __GNUC__ >= 5))
41 # define HAVE_IS_TRIVIALLY_CONSTRUCTIBLE 1
42 #endif
44 namespace gdb {
46 /* Pre C++14-safe (CWG 1558) version of C++17's std::void_t. See
47 <http://en.cppreference.com/w/cpp/types/void_t>. */
49 template<typename... Ts>
50 struct make_void { typedef void type; };
52 template<typename... Ts>
53 using void_t = typename make_void<Ts...>::type;
55 /* Implementation of the detection idiom:
57 - http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf
58 - http://en.cppreference.com/w/cpp/experimental/is_detected
62 struct nonesuch
64 nonesuch () = delete;
65 ~nonesuch () = delete;
66 nonesuch (const nonesuch &) = delete;
67 void operator= (const nonesuch &) = delete;
70 namespace detection_detail {
71 /* Implementation of the detection idiom (negative case). */
72 template<typename Default, typename AlwaysVoid,
73 template<typename...> class Op, typename... Args>
74 struct detector
76 using value_t = std::false_type;
77 using type = Default;
80 /* Implementation of the detection idiom (positive case). */
81 template<typename Default, template<typename...> class Op, typename... Args>
82 struct detector<Default, void_t<Op<Args...>>, Op, Args...>
84 using value_t = std::true_type;
85 using type = Op<Args...>;
88 /* Detect whether Op<Args...> is a valid type, use Default if not. */
89 template<typename Default, template<typename...> class Op,
90 typename... Args>
91 using detected_or = detector<Default, void, Op, Args...>;
93 /* Op<Args...> if that is a valid type, otherwise Default. */
94 template<typename Default, template<typename...> class Op,
95 typename... Args>
96 using detected_or_t
97 = typename detected_or<Default, Op, Args...>::type;
99 } /* detection_detail */
101 template<template<typename...> class Op, typename... Args>
102 using is_detected
103 = typename detection_detail::detector<nonesuch, void, Op, Args...>::value_t;
105 template<template<typename...> class Op, typename... Args>
106 using detected_t
107 = typename detection_detail::detector<nonesuch, void, Op, Args...>::type;
109 template<typename Default, template<typename...> class Op, typename... Args>
110 using detected_or = detection_detail::detected_or<Default, Op, Args...>;
112 template<typename Default, template<typename...> class Op, typename... Args>
113 using detected_or_t = typename detected_or<Default, Op, Args...>::type;
115 template<typename Expected, template<typename...> class Op, typename... Args>
116 using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
118 template<typename To, template<typename...> class Op, typename... Args>
119 using is_detected_convertible
120 = std::is_convertible<detected_t<Op, Args...>, To>;
122 /* A few trait helpers, mainly stolen from libstdc++. Uppercase
123 because "and/or", etc. are reserved keywords. */
125 template<typename Predicate>
126 struct Not : public std::integral_constant<bool, !Predicate::value>
129 template<typename...>
130 struct Or;
132 template<>
133 struct Or<> : public std::false_type
136 template<typename B1>
137 struct Or<B1> : public B1
140 template<typename B1, typename B2>
141 struct Or<B1, B2>
142 : public std::conditional<B1::value, B1, B2>::type
145 template<typename B1,typename B2,typename B3, typename... Bn>
146 struct Or<B1, B2, B3, Bn...>
147 : public std::conditional<B1::value, B1, Or<B2, B3, Bn...>>::type
150 template<typename...>
151 struct And;
153 template<>
154 struct And<> : public std::true_type
157 template<typename B1>
158 struct And<B1> : public B1
161 template<typename B1, typename B2>
162 struct And<B1, B2>
163 : public std::conditional<B1::value, B2, B1>::type
166 template<typename B1, typename B2, typename B3, typename... Bn>
167 struct And<B1, B2, B3, Bn...>
168 : public std::conditional<B1::value, And<B2, B3, Bn...>, B1>::type
171 /* Concepts-light-like helper to make SFINAE logic easier to read. */
172 template<typename Condition>
173 using Requires = typename std::enable_if<Condition::value, void>::type;
176 #endif /* COMMON_TRAITS_H */