1 /* Copyright (C) 2017-2020 Free Software Foundation, Inc. 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 21 #include <type_traits> 22 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 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 43 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 55 /* A few trait helpers, mainly stolen from libstdc++. Uppercase 56 because "and/or", etc. are reserved keywords. */ 57 58 template<typename Predicate> 59 struct Not : public std::integral_constant<bool, !Predicate::value> 60 {}; 61 62 template<typename...> 63 struct Or; 64 65 template<> 66 struct Or<> : public std::false_type 67 {}; 68 69 template<typename B1> 70 struct Or<B1> : public B1 71 {}; 72 73 template<typename B1, typename B2> 74 struct Or<B1, B2> 75 : public std::conditional<B1::value, B1, B2>::type 76 {}; 77 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 81 {}; 82 83 template<typename...> 84 struct And; 85 86 template<> 87 struct And<> : public std::true_type 88 {}; 89 90 template<typename B1> 91 struct And<B1> : public B1 92 {}; 93 94 template<typename B1, typename B2> 95 struct And<B1, B2> 96 : public std::conditional<B1::value, B2, B1>::type 97 {}; 98 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 102 {}; 103 104 /* 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; 107 } 108 109 #endif /* COMMON_TRAITS_H */ 110