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 // Since C++20 the primary template should be used for allocator<void>, 64 // but then it would have a non-trivial default ctor and dtor for C++20, 65 // but trivial for C++98-17, which would be an ABI incompatibiliy between 66 // different standard dialects. So C++20 still uses the allocator<void> 67 // explicit specialization, with the historical ABI properties, but with 68 // the same members that are present in the primary template. 69 70 /// allocator<void> specialization. 71 template<> 72 class allocator<void> 73 { 74 public: 75 typedef void value_type; 76 typedef size_t size_type; 77 typedef ptrdiff_t difference_type; 78 79 #if __cplusplus <= 201703L 80 // These were removed for C++20, allocator_traits does the right thing. 81 typedef void* pointer; 82 typedef const void* const_pointer; 83 84 template<typename _Tp1> 85 struct rebind 86 { typedef allocator<_Tp1> other; }; 87 #endif 88 89 #if __cplusplus >= 201103L 90 // _GLIBCXX_RESOLVE_LIB_DEFECTS 91 // 2103. std::allocator propagate_on_container_move_assignment 92 typedef true_type propagate_on_container_move_assignment; 93 94 typedef true_type is_always_equal; 95 96 #if __cplusplus > 201703L 97 // As noted above, these members are present for C++20 to provide the 98 // same API as the primary template, but still trivial as in pre-C++20. 99 allocator() = default; 100 ~allocator() = default; 101 102 template<typename _Up> 103 constexpr 104 allocator(const allocator<_Up>&) noexcept { } 105 106 // No allocate member because it's ill-formed by LWG 3307. 107 // No deallocate member because it would be undefined to call it 108 // with any pointer which wasn't obtained from allocate. 109 #endif // C++20 110 #endif // C++11 111 }; 112 113 /** 114 * @brief The @a standard allocator, as per C++03 [20.4.1]. 115 * 116 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator 117 * for further details. 118 * 119 * @tparam _Tp Type of allocated object. 120 */ 121 template<typename _Tp> 122 class allocator : public __allocator_base<_Tp> 123 { 124 public: 125 typedef _Tp value_type; 126 typedef size_t size_type; 127 typedef ptrdiff_t difference_type; 128 129 #if __cplusplus <= 201703L 130 // These were removed for C++20. 131 typedef _Tp* pointer; 132 typedef const _Tp* const_pointer; 133 typedef _Tp& reference; 134 typedef const _Tp& const_reference; 135 136 template<typename _Tp1> 137 struct rebind 138 { typedef allocator<_Tp1> other; }; 139 #endif 140 141 #if __cplusplus >= 201103L 142 // _GLIBCXX_RESOLVE_LIB_DEFECTS 143 // 2103. std::allocator propagate_on_container_move_assignment 144 typedef true_type propagate_on_container_move_assignment; 145 146 typedef true_type is_always_equal; 147 #endif 148 149 // _GLIBCXX_RESOLVE_LIB_DEFECTS 150 // 3035. std::allocator's constructors should be constexpr 151 _GLIBCXX20_CONSTEXPR 152 allocator() _GLIBCXX_NOTHROW { } 153 154 _GLIBCXX20_CONSTEXPR 155 allocator(const allocator& __a) _GLIBCXX_NOTHROW 156 : __allocator_base<_Tp>(__a) { } 157 158 #if __cplusplus >= 201103L 159 // Avoid implicit deprecation. 160 allocator& operator=(const allocator&) = default; 161 #endif 162 163 template<typename _Tp1> 164 _GLIBCXX20_CONSTEXPR 165 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { } 166 167 #if __cpp_constexpr_dynamic_alloc 168 constexpr 169 #endif 170 ~allocator() _GLIBCXX_NOTHROW { } 171 172 #if __cplusplus > 201703L 173 [[nodiscard,__gnu__::__always_inline__]] 174 constexpr _Tp* 175 allocate(size_t __n) 176 { 177 #ifdef __cpp_lib_is_constant_evaluated 178 if (std::is_constant_evaluated()) 179 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp))); 180 #endif 181 return __allocator_base<_Tp>::allocate(__n, 0); 182 } 183 184 [[__gnu__::__always_inline__]] 185 constexpr void 186 deallocate(_Tp* __p, size_t __n) 187 { 188 #ifdef __cpp_lib_is_constant_evaluated 189 if (std::is_constant_evaluated()) 190 { 191 ::operator delete(__p); 192 return; 193 } 194 #endif 195 __allocator_base<_Tp>::deallocate(__p, __n); 196 } 197 #endif // C++20 198 199 friend _GLIBCXX20_CONSTEXPR bool 200 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW 201 { return true; } 202 203 #if __cpp_impl_three_way_comparison < 201907L 204 friend _GLIBCXX20_CONSTEXPR bool 205 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW 206 { return false; } 207 #endif 208 209 // Inherit everything else. 210 }; 211 212 template<typename _T1, typename _T2> 213 inline _GLIBCXX20_CONSTEXPR bool 214 operator==(const allocator<_T1>&, const allocator<_T2>&) 215 _GLIBCXX_NOTHROW 216 { return true; } 217 218 #if __cpp_impl_three_way_comparison < 201907L 219 template<typename _T1, typename _T2> 220 inline _GLIBCXX20_CONSTEXPR bool 221 operator!=(const allocator<_T1>&, const allocator<_T2>&) 222 _GLIBCXX_NOTHROW 223 { return false; } 224 #endif 225 226 // Invalid allocator<cv T> partial specializations. 227 // allocator_traits::rebind_alloc can be used to form a valid allocator type. 228 template<typename _Tp> 229 class allocator<const _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<volatile _Tp> 238 { 239 public: 240 typedef _Tp value_type; 241 template<typename _Up> allocator(const allocator<_Up>&) { } 242 }; 243 244 template<typename _Tp> 245 class allocator<const volatile _Tp> 246 { 247 public: 248 typedef _Tp value_type; 249 template<typename _Up> allocator(const allocator<_Up>&) { } 250 }; 251 252 /// @} group allocator 253 254 // Inhibit implicit instantiations for required instantiations, 255 // which are defined via explicit instantiations elsewhere. 256 #if _GLIBCXX_EXTERN_TEMPLATE 257 extern template class allocator<char>; 258 extern template class allocator<wchar_t>; 259 #endif 260 261 // Undefine. 262 #undef __allocator_base 263 264 // To implement Option 3 of DR 431. 265 template<typename _Alloc, bool = __is_empty(_Alloc)> 266 struct __alloc_swap 267 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } }; 268 269 template<typename _Alloc> 270 struct __alloc_swap<_Alloc, false> 271 { 272 static void 273 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT 274 { 275 // Precondition: swappable allocators. 276 if (__one != __two) 277 swap(__one, __two); 278 } 279 }; 280 281 // Optimize for stateless allocators. 282 template<typename _Alloc, bool = __is_empty(_Alloc)> 283 struct __alloc_neq 284 { 285 static bool 286 _S_do_it(const _Alloc&, const _Alloc&) 287 { return false; } 288 }; 289 290 template<typename _Alloc> 291 struct __alloc_neq<_Alloc, false> 292 { 293 static bool 294 _S_do_it(const _Alloc& __one, const _Alloc& __two) 295 { return __one != __two; } 296 }; 297 298 #if __cplusplus >= 201103L 299 template<typename _Tp, bool 300 = __or_<is_copy_constructible<typename _Tp::value_type>, 301 is_nothrow_move_constructible<typename _Tp::value_type>>::value> 302 struct __shrink_to_fit_aux 303 { static bool _S_do_it(_Tp&) noexcept { return false; } }; 304 305 template<typename _Tp> 306 struct __shrink_to_fit_aux<_Tp, true> 307 { 308 static bool 309 _S_do_it(_Tp& __c) noexcept 310 { 311 #if __cpp_exceptions 312 try 313 { 314 _Tp(__make_move_if_noexcept_iterator(__c.begin()), 315 __make_move_if_noexcept_iterator(__c.end()), 316 __c.get_allocator()).swap(__c); 317 return true; 318 } 319 catch(...) 320 { return false; } 321 #else 322 return false; 323 #endif 324 } 325 }; 326 #endif 327 328 _GLIBCXX_END_NAMESPACE_VERSION 329 } // namespace std 330 331 #endif 332