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traits.h
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1 /* Copyright (C) 2017-2018 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 namespace gdb {
37
38 /* Pre C++14-safe (CWG 1558) version of C++17's std::void_t. See
39 <http://en.cppreference.com/w/cpp/types/void_t>. */
40
41 template<typename... Ts>
42 struct make_void { typedef void type; };
43
44 template<typename... Ts>
45 using void_t = typename make_void<Ts...>::type;
46
47 /* A few trait helpers, mainly stolen from libstdc++. Uppercase
48 because "and/or", etc. are reserved keywords. */
49
50 template<typename Predicate>
51 struct Not : public std::integral_constant<bool, !Predicate::value>
52 {};
53
54 template<typename...>
55 struct Or;
56
57 template<>
58 struct Or<> : public std::false_type
59 {};
60
61 template<typename B1>
62 struct Or<B1> : public B1
63 {};
64
65 template<typename B1, typename B2>
66 struct Or<B1, B2>
67 : public std::conditional<B1::value, B1, B2>::type
68 {};
69
70 template<typename B1,typename B2,typename B3, typename... Bn>
71 struct Or<B1, B2, B3, Bn...>
72 : public std::conditional<B1::value, B1, Or<B2, B3, Bn...>>::type
73 {};
74
75 template<typename...>
76 struct And;
77
78 template<>
79 struct And<> : public std::true_type
80 {};
81
82 template<typename B1>
83 struct And<B1> : public B1
84 {};
85
86 template<typename B1, typename B2>
87 struct And<B1, B2>
88 : public std::conditional<B1::value, B2, B1>::type
89 {};
90
91 template<typename B1, typename B2, typename B3, typename... Bn>
92 struct And<B1, B2, B3, Bn...>
93 : public std::conditional<B1::value, And<B2, B3, Bn...>, B1>::type
94 {};
95
96 /* Concepts-light-like helper to make SFINAE logic easier to read. */
97 template<typename Condition>
98 using Requires = typename std::enable_if<Condition::value, void>::type;
99 }
100
101 #endif /* COMMON_TRAITS_H */
gdb::And< B1 >
Definition: traits.h:83
gdb::make_void::type
void type
Definition: traits.h:42
gdb::And<>
Definition: traits.h:79
gdb::Or<>
Definition: traits.h:58
gdb::Not
Definition: traits.h:51
gdb::Or< B1 >
Definition: traits.h:62
gdb::And
Definition: traits.h:76
gdb::Or
Definition: traits.h:55
gdb
Definition: array-view.h:66
gdb::Requires
typename std::enable_if< Condition::value, void >::type Requires
Definition: traits.h:98
gdb::make_void
Definition: traits.h:42
gdb::void_t
typename make_void< Ts... >::type void_t
Definition: traits.h:45
gdb::And< B1, B2 >
Definition: traits.h:87
gdb::Or< B1, B2 >
Definition: traits.h:66