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3666a048 | 1 | /* Copyright (C) 2017-2021 Free Software Foundation, Inc. |
9c541725 PA |
2 | |
3 | This file is part of GDB. | |
4 | ||
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. | |
9 | ||
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. | |
14 | ||
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/>. */ | |
17 | ||
18 | #ifndef COMMON_TRAITS_H | |
19 | #define COMMON_TRAITS_H | |
20 | ||
22796e97 PA |
21 | #include <type_traits> |
22 | ||
debed3db PA |
23 | /* GCC does not understand __has_feature. */ |
24 | #if !defined(__has_feature) | |
25 | # define __has_feature(x) 0 | |
26 | #endif | |
27 | ||
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 | |
35 | ||
284a0e3c SM |
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)) | |
184cde75 | 41 | # define HAVE_IS_TRIVIALLY_CONSTRUCTIBLE 1 |
284a0e3c SM |
42 | #endif |
43 | ||
9c541725 PA |
44 | namespace gdb { |
45 | ||
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>. */ | |
48 | ||
49 | template<typename... Ts> | |
50 | struct make_void { typedef void type; }; | |
51 | ||
52 | template<typename... Ts> | |
53 | using void_t = typename make_void<Ts...>::type; | |
54 | ||
1945192c PA |
55 | /* Implementation of the detection idiom: |
56 | ||
57 | - http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf | |
58 | - http://en.cppreference.com/w/cpp/experimental/is_detected | |
59 | ||
60 | */ | |
61 | ||
62 | struct nonesuch | |
63 | { | |
64 | nonesuch () = delete; | |
65 | ~nonesuch () = delete; | |
66 | nonesuch (const nonesuch &) = delete; | |
67 | void operator= (const nonesuch &) = delete; | |
68 | }; | |
69 | ||
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 | |
75 | { | |
76 | using value_t = std::false_type; | |
77 | using type = Default; | |
78 | }; | |
79 | ||
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...> | |
83 | { | |
84 | using value_t = std::true_type; | |
85 | using type = Op<Args...>; | |
86 | }; | |
87 | ||
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...>; | |
92 | ||
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; | |
98 | ||
99 | } /* detection_detail */ | |
100 | ||
101 | template<template<typename...> class Op, typename... Args> | |
102 | using is_detected | |
103 | = typename detection_detail::detector<nonesuch, void, Op, Args...>::value_t; | |
104 | ||
105 | template<template<typename...> class Op, typename... Args> | |
106 | using detected_t | |
107 | = typename detection_detail::detector<nonesuch, void, Op, Args...>::type; | |
108 | ||
109 | template<typename Default, template<typename...> class Op, typename... Args> | |
110 | using detected_or = detection_detail::detected_or<Default, Op, Args...>; | |
111 | ||
112 | template<typename Default, template<typename...> class Op, typename... Args> | |
113 | using detected_or_t = typename detected_or<Default, Op, Args...>::type; | |
114 | ||
115 | template<typename Expected, template<typename...> class Op, typename... Args> | |
116 | using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>; | |
117 | ||
118 | template<typename To, template<typename...> class Op, typename... Args> | |
119 | using is_detected_convertible | |
120 | = std::is_convertible<detected_t<Op, Args...>, To>; | |
121 | ||
22796e97 | 122 | /* A few trait helpers, mainly stolen from libstdc++. Uppercase |
b0b92aeb PA |
123 | because "and/or", etc. are reserved keywords. */ |
124 | ||
125 | template<typename Predicate> | |
126 | struct Not : public std::integral_constant<bool, !Predicate::value> | |
127 | {}; | |
128 | ||
129 | template<typename...> | |
130 | struct Or; | |
131 | ||
132 | template<> | |
133 | struct Or<> : public std::false_type | |
134 | {}; | |
135 | ||
136 | template<typename B1> | |
137 | struct Or<B1> : public B1 | |
138 | {}; | |
139 | ||
140 | template<typename B1, typename B2> | |
141 | struct Or<B1, B2> | |
142 | : public std::conditional<B1::value, B1, B2>::type | |
143 | {}; | |
144 | ||
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 | |
148 | {}; | |
22796e97 PA |
149 | |
150 | template<typename...> | |
151 | struct And; | |
152 | ||
153 | template<> | |
154 | struct And<> : public std::true_type | |
155 | {}; | |
156 | ||
157 | template<typename B1> | |
158 | struct And<B1> : public B1 | |
159 | {}; | |
160 | ||
161 | template<typename B1, typename B2> | |
162 | struct And<B1, B2> | |
163 | : public std::conditional<B1::value, B2, B1>::type | |
164 | {}; | |
165 | ||
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 | |
169 | {}; | |
170 | ||
b0b92aeb PA |
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; | |
9c541725 PA |
174 | } |
175 | ||
176 | #endif /* COMMON_TRAITS_H */ |