1 /* Copyright (C) 2017-2019 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
28 /* HAVE_IS_TRIVIALLY_COPYABLE is defined as 1 iff
29 std::is_trivially_copyable is available. GCC only implemented it
31 #if (__has_feature(is_trivially_copyable) \
32 || (defined __GNUC__ && __GNUC__ >= 5))
33 # define HAVE_IS_TRIVIALLY_COPYABLE 1
36 /* HAVE_IS_TRIVIALLY_CONSTRUCTIBLE is defined as 1 iff
37 std::is_trivially_constructible is available. GCC only implemented it
39 #if (__has_feature(is_trivially_constructible) \
40 || (defined __GNUC__ && __GNUC__ >= 5))
41 # define HAVE_IS_TRIVIALLY_CONSTRUCTIBLE 1
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 /* A few trait helpers, mainly stolen from libstdc++. Uppercase
56 because "and/or", etc. are reserved keywords. */
58 template<typename Predicate>
59 struct Not : public std::integral_constant<bool, !Predicate::value>
66 struct Or<> : public std::false_type
70 struct Or<B1> : public B1
73 template<typename B1, typename B2>
75 : public std::conditional<B1::value, B1, B2>::type
78 template<typename B1,typename B2,typename B3, typename... Bn>
79 struct Or<B1, B2, B3, Bn...>
80 : public std::conditional<B1::value, B1, Or<B2, B3, Bn...>>::type
87 struct And<> : public std::true_type
91 struct And<B1> : public B1
94 template<typename B1, typename B2>
96 : public std::conditional<B1::value, B2, B1>::type
99 template<typename B1, typename B2, typename B3, typename... Bn>
100 struct And<B1, B2, B3, Bn...>
101 : public std::conditional<B1::value, And<B2, B3, Bn...>, B1>::type
104 /* Concepts-light-like helper to make SFINAE logic easier to read. */
105 template<typename Condition>
106 using Requires = typename std::enable_if<Condition::value, void>::type;
109 #endif /* COMMON_TRAITS_H */