libstdc++
type_traits.h
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1 // -*- C++ -*-
2 
3 // Copyright (C) 2005-2025 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the terms
7 // of the GNU General Public License as published by the Free Software
8 // Foundation; either version 3, or (at your option) any later
9 // version.
10 
11 // This library is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file ext/type_traits.h
26  * This file is a GNU extension to the Standard C++ Library.
27  */
28 
29 #ifndef _EXT_TYPE_TRAITS
30 #define _EXT_TYPE_TRAITS 1
31 
32 #ifdef _GLIBCXX_SYSHDR
33 #pragma GCC system_header
34 #endif
35 
36 #include <bits/c++config.h>
37 #include <bits/cpp_type_traits.h>
38 
39 #pragma GCC diagnostic push
40 #pragma GCC diagnostic ignored "-Wlong-long"
41 
42 extern "C++" {
43 
44 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
45 {
46 _GLIBCXX_BEGIN_NAMESPACE_VERSION
47 
48  // Define a nested type if some predicate holds.
49  template<bool, typename>
50  struct __enable_if
51  { };
52 
53  template<typename _Tp>
54  struct __enable_if<true, _Tp>
55  { typedef _Tp __type; };
56 
57 
58  // Conditional expression for types. If true, first, if false, second.
59  template<bool _Cond, typename _Iftrue, typename _Iffalse>
60  struct __conditional_type
61  { typedef _Iftrue __type; };
62 
63  template<typename _Iftrue, typename _Iffalse>
64  struct __conditional_type<false, _Iftrue, _Iffalse>
65  { typedef _Iffalse __type; };
66 
67 
68  // Given an integral builtin type, return the corresponding unsigned type.
69  template<typename _Tp>
70  struct __add_unsigned
71  {
72  private:
73  typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
74 
75  public:
76  typedef typename __if_type::__type __type;
77  };
78 
79  template<>
80  struct __add_unsigned<char>
81  { typedef unsigned char __type; };
82 
83  template<>
84  struct __add_unsigned<signed char>
85  { typedef unsigned char __type; };
86 
87  template<>
88  struct __add_unsigned<short>
89  { typedef unsigned short __type; };
90 
91  template<>
92  struct __add_unsigned<int>
93  { typedef unsigned int __type; };
94 
95  template<>
96  struct __add_unsigned<long>
97  { typedef unsigned long __type; };
98 
99  template<>
100  struct __add_unsigned<long long>
101  { typedef unsigned long long __type; };
102 
103  // Declare but don't define.
104  template<>
105  struct __add_unsigned<bool>;
106 
107  template<>
108  struct __add_unsigned<wchar_t>;
109 
110 
111  // Given an integral builtin type, return the corresponding signed type.
112  template<typename _Tp>
113  struct __remove_unsigned
114  {
115  private:
116  typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
117 
118  public:
119  typedef typename __if_type::__type __type;
120  };
121 
122  template<>
123  struct __remove_unsigned<char>
124  { typedef signed char __type; };
125 
126  template<>
127  struct __remove_unsigned<unsigned char>
128  { typedef signed char __type; };
129 
130  template<>
131  struct __remove_unsigned<unsigned short>
132  { typedef short __type; };
133 
134  template<>
135  struct __remove_unsigned<unsigned int>
136  { typedef int __type; };
137 
138  template<>
139  struct __remove_unsigned<unsigned long>
140  { typedef long __type; };
141 
142  template<>
143  struct __remove_unsigned<unsigned long long>
144  { typedef long long __type; };
145 
146  // Declare but don't define.
147  template<>
148  struct __remove_unsigned<bool>;
149 
150  template<>
151  struct __remove_unsigned<wchar_t>;
152 
153 
154  // For use in string and vstring.
155  template<typename _Type>
156  _GLIBCXX_CONSTEXPR
157  inline bool
158  __is_null_pointer(_Type* __ptr)
159  { return __ptr == 0; }
160 
161  template<typename _Type>
162  _GLIBCXX_CONSTEXPR
163  inline bool
164  __is_null_pointer(_Type)
165  { return false; }
166 
167 #if __cplusplus >= 201103L
168  constexpr bool
169  __is_null_pointer(std::nullptr_t)
170  { return true; }
171 #endif
172 
173  // For arithmetic promotions in <complex> and <cmath>
174 
175  template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
176  struct __promote
177  { typedef double __type; };
178 
179  // No nested __type member for non-integer non-floating point types,
180  // allows this type to be used for SFINAE to constrain overloads in
181  // <cmath> and <complex> to only the intended types.
182  template<typename _Tp>
183  struct __promote<_Tp, false>
184  { };
185 
186  template<>
187  struct __promote<long double>
188  { typedef long double __type; };
189 
190  template<>
191  struct __promote<double>
192  { typedef double __type; };
193 
194  template<>
195  struct __promote<float>
196  { typedef float __type; };
197 
198 #ifdef __STDCPP_FLOAT16_T__
199  template<>
200  struct __promote<_Float16>
201  { typedef _Float16 __type; };
202 #endif
203 
204 #ifdef __STDCPP_FLOAT32_T__
205  template<>
206  struct __promote<_Float32>
207  { typedef _Float32 __type; };
208 #endif
209 
210 #ifdef __STDCPP_FLOAT64_T__
211  template<>
212  struct __promote<_Float64>
213  { typedef _Float64 __type; };
214 #endif
215 
216 #ifdef __STDCPP_FLOAT128_T__
217  template<>
218  struct __promote<_Float128>
219  { typedef _Float128 __type; };
220 #endif
221 
222 #ifdef __STDCPP_BFLOAT16_T__
223  template<>
224  struct __promote<__gnu_cxx::__bfloat16_t>
225  { typedef __gnu_cxx::__bfloat16_t __type; };
226 #endif
227 
228 #if __cpp_fold_expressions
229 
230  template<typename... _Tp>
231  using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
232 
233  // Deducing the promoted type is done by __promoted_t<_Tp...>,
234  // then __promote is used to provide the nested __type member.
235  template<typename _Tp, typename _Up>
236  using __promote_2 = __promote<__promoted_t<_Tp, _Up>>;
237 
238  template<typename _Tp, typename _Up, typename _Vp>
239  using __promote_3 = __promote<__promoted_t<_Tp, _Up, _Vp>>;
240 
241  template<typename _Tp, typename _Up, typename _Vp, typename _Wp>
242  using __promote_4 = __promote<__promoted_t<_Tp, _Up, _Vp, _Wp>>;
243 
244 #else
245 
246  template<typename _Tp, typename _Up,
247  typename _Tp2 = typename __promote<_Tp>::__type,
248  typename _Up2 = typename __promote<_Up>::__type>
249  struct __promote_2
250  {
251  typedef __typeof__(_Tp2() + _Up2()) __type;
252  };
253 
254  template<typename _Tp, typename _Up, typename _Vp,
255  typename _Tp2 = typename __promote<_Tp>::__type,
256  typename _Up2 = typename __promote<_Up>::__type,
257  typename _Vp2 = typename __promote<_Vp>::__type>
258  struct __promote_3
259  {
260  typedef __typeof__(_Tp2() + _Up2() + _Vp2()) __type;
261  };
262 
263  template<typename _Tp, typename _Up, typename _Vp, typename _Wp,
264  typename _Tp2 = typename __promote<_Tp>::__type,
265  typename _Up2 = typename __promote<_Up>::__type,
266  typename _Vp2 = typename __promote<_Vp>::__type,
267  typename _Wp2 = typename __promote<_Wp>::__type>
268  struct __promote_4
269  {
270  typedef __typeof__(_Tp2() + _Up2() + _Vp2() + _Wp2()) __type;
271  };
272 #endif
273 
274 _GLIBCXX_END_NAMESPACE_VERSION
275 } // namespace
276 } // extern "C++"
277 
278 #pragma GCC diagnostic pop
279 
280 #endif
GNU extensions for public use.