1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001-2020 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 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU 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 /* 26 * Copyright (c) 1996-1997 27 * Silicon Graphics Computer Systems, Inc. 28 * 29 * Permission to use, copy, modify, distribute and sell this software 30 * and its documentation for any purpose is hereby granted without fee, 31 * provided that the above copyright notice appear in all copies and 32 * that both that copyright notice and this permission notice appear 33 * in supporting documentation. Silicon Graphics makes no 34 * representations about the suitability of this software for any 35 * purpose. It is provided "as is" without express or implied warranty. 36 */ 37 38 /** @file bits/allocator.h 39 * This is an internal header file, included by other library headers. 40 * Do not attempt to use it directly. @headername{memory} 41 */ 42 43 #ifndef _ALLOCATOR_H 44 #define _ALLOCATOR_H 1 45 46 #include <bits/c++allocator.h> // Define the base class to std::allocator. 47 #include <bits/memoryfwd.h> 48 #if __cplusplus >= 201103L 49 #include <type_traits> 50 #endif 51 52 #define __cpp_lib_incomplete_container_elements 201505 53 54 namespace std _GLIBCXX_VISIBILITY(default) 55 { 56 _GLIBCXX_BEGIN_NAMESPACE_VERSION 57 58 /** 59 * @addtogroup allocators 60 * @{ 61 */ 62 63 /// allocator<void> specialization. 64 template<> 65 class allocator<void> 66 { 67 public: 68 typedef void value_type; 69 typedef size_t size_type; 70 typedef ptrdiff_t difference_type; 71 #if __cplusplus <= 201703L 72 typedef void* pointer; 73 typedef const void* const_pointer; 74 75 template<typename _Tp1> 76 struct rebind 77 { typedef allocator<_Tp1> other; }; 78 #else 79 allocator() = default; 80 81 template<typename _Up> 82 constexpr 83 allocator(const allocator<_Up>&) { } 84 #endif // ! C++20 85 86 #if __cplusplus >= 201103L && __cplusplus <= 201703L 87 // _GLIBCXX_RESOLVE_LIB_DEFECTS 88 // 2103. std::allocator propagate_on_container_move_assignment 89 typedef true_type propagate_on_container_move_assignment; 90 91 typedef true_type is_always_equal; 92 93 template<typename _Up, typename... _Args> 94 void 95 construct(_Up* __p, _Args&&... __args) 96 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value) 97 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 98 99 template<typename _Up> 100 void 101 destroy(_Up* __p) 102 noexcept(std::is_nothrow_destructible<_Up>::value) 103 { __p->~_Up(); } 104 #endif // C++11 to C++17 105 }; 106 107 /** 108 * @brief The @a standard allocator, as per [20.4]. 109 * 110 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator 111 * for further details. 112 * 113 * @tparam _Tp Type of allocated object. 114 */ 115 template<typename _Tp> 116 class allocator : public __allocator_base<_Tp> 117 { 118 public: 119 typedef _Tp value_type; 120 typedef size_t size_type; 121 typedef ptrdiff_t difference_type; 122 #if __cplusplus <= 201703L 123 typedef _Tp* pointer; 124 typedef const _Tp* const_pointer; 125 typedef _Tp& reference; 126 typedef const _Tp& const_reference; 127 128 template<typename _Tp1> 129 struct rebind 130 { typedef allocator<_Tp1> other; }; 131 #endif 132 133 #if __cplusplus >= 201103L 134 // _GLIBCXX_RESOLVE_LIB_DEFECTS 135 // 2103. std::allocator propagate_on_container_move_assignment 136 typedef true_type propagate_on_container_move_assignment; 137 138 typedef true_type is_always_equal; 139 #endif 140 141 // _GLIBCXX_RESOLVE_LIB_DEFECTS 142 // 3035. std::allocator's constructors should be constexpr 143 _GLIBCXX20_CONSTEXPR 144 allocator() _GLIBCXX_NOTHROW { } 145 146 _GLIBCXX20_CONSTEXPR 147 allocator(const allocator& __a) _GLIBCXX_NOTHROW 148 : __allocator_base<_Tp>(__a) { } 149 150 #if __cplusplus >= 201103L 151 // Avoid implicit deprecation. 152 allocator& operator=(const allocator&) = default; 153 #endif 154 155 template<typename _Tp1> 156 _GLIBCXX20_CONSTEXPR 157 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { } 158 159 #if __cpp_constexpr_dynamic_alloc 160 constexpr 161 #endif 162 ~allocator() _GLIBCXX_NOTHROW { } 163 164 #if __cplusplus > 201703L 165 [[nodiscard,__gnu__::__always_inline__]] 166 constexpr _Tp* 167 allocate(size_t __n) 168 { 169 #ifdef __cpp_lib_is_constant_evaluated 170 if (std::is_constant_evaluated()) 171 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp))); 172 #endif 173 return __allocator_base<_Tp>::allocate(__n, 0); 174 } 175 176 [[__gnu__::__always_inline__]] 177 constexpr void 178 deallocate(_Tp* __p, size_t __n) 179 { 180 #ifdef __cpp_lib_is_constant_evaluated 181 if (std::is_constant_evaluated()) 182 { 183 ::operator delete(__p); 184 return; 185 } 186 #endif 187 __allocator_base<_Tp>::deallocate(__p, __n); 188 } 189 #endif // C++20 190 191 friend _GLIBCXX20_CONSTEXPR bool 192 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW 193 { return true; } 194 195 #if __cpp_impl_three_way_comparison < 201907L 196 friend _GLIBCXX20_CONSTEXPR bool 197 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW 198 { return false; } 199 #endif 200 201 // Inherit everything else. 202 }; 203 204 template<typename _T1, typename _T2> 205 inline _GLIBCXX20_CONSTEXPR bool 206 operator==(const allocator<_T1>&, const allocator<_T2>&) 207 _GLIBCXX_NOTHROW 208 { return true; } 209 210 #if __cpp_impl_three_way_comparison < 201907L 211 template<typename _T1, typename _T2> 212 inline _GLIBCXX20_CONSTEXPR bool 213 operator!=(const allocator<_T1>&, const allocator<_T2>&) 214 _GLIBCXX_NOTHROW 215 { return false; } 216 #endif 217 218 // Invalid allocator<cv T> partial specializations. 219 // allocator_traits::rebind_alloc can be used to form a valid allocator type. 220 template<typename _Tp> 221 class allocator<const _Tp> 222 { 223 public: 224 typedef _Tp value_type; 225 template<typename _Up> allocator(const allocator<_Up>&) { } 226 }; 227 228 template<typename _Tp> 229 class allocator<volatile _Tp> 230 { 231 public: 232 typedef _Tp value_type; 233 template<typename _Up> allocator(const allocator<_Up>&) { } 234 }; 235 236 template<typename _Tp> 237 class allocator<const volatile _Tp> 238 { 239 public: 240 typedef _Tp value_type; 241 template<typename _Up> allocator(const allocator<_Up>&) { } 242 }; 243 244 /// @} group allocator 245 246 // Inhibit implicit instantiations for required instantiations, 247 // which are defined via explicit instantiations elsewhere. 248 #if _GLIBCXX_EXTERN_TEMPLATE 249 extern template class allocator<char>; 250 extern template class allocator<wchar_t>; 251 #endif 252 253 // Undefine. 254 #undef __allocator_base 255 256 // To implement Option 3 of DR 431. 257 template<typename _Alloc, bool = __is_empty(_Alloc)> 258 struct __alloc_swap 259 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } }; 260 261 template<typename _Alloc> 262 struct __alloc_swap<_Alloc, false> 263 { 264 static void 265 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT 266 { 267 // Precondition: swappable allocators. 268 if (__one != __two) 269 swap(__one, __two); 270 } 271 }; 272 273 // Optimize for stateless allocators. 274 template<typename _Alloc, bool = __is_empty(_Alloc)> 275 struct __alloc_neq 276 { 277 static bool 278 _S_do_it(const _Alloc&, const _Alloc&) 279 { return false; } 280 }; 281 282 template<typename _Alloc> 283 struct __alloc_neq<_Alloc, false> 284 { 285 static bool 286 _S_do_it(const _Alloc& __one, const _Alloc& __two) 287 { return __one != __two; } 288 }; 289 290 #if __cplusplus >= 201103L 291 template<typename _Tp, bool 292 = __or_<is_copy_constructible<typename _Tp::value_type>, 293 is_nothrow_move_constructible<typename _Tp::value_type>>::value> 294 struct __shrink_to_fit_aux 295 { static bool _S_do_it(_Tp&) noexcept { return false; } }; 296 297 template<typename _Tp> 298 struct __shrink_to_fit_aux<_Tp, true> 299 { 300 static bool 301 _S_do_it(_Tp& __c) noexcept 302 { 303 #if __cpp_exceptions 304 try 305 { 306 _Tp(__make_move_if_noexcept_iterator(__c.begin()), 307 __make_move_if_noexcept_iterator(__c.end()), 308 __c.get_allocator()).swap(__c); 309 return true; 310 } 311 catch(...) 312 { return false; } 313 #else 314 return false; 315 #endif 316 } 317 }; 318 #endif 319 320 _GLIBCXX_END_NAMESPACE_VERSION 321 } // namespace std 322 323 #endif 324