libstdc++
memory
Go to the documentation of this file.
1 // <memory> -*- 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) 1997-1999
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 
39 /** @file include/memory
40  * This is a Standard C++ Library header.
41  * @ingroup memory
42  */
43 
44 #ifndef _GLIBCXX_MEMORY
45 #define _GLIBCXX_MEMORY 1
46 
47 #pragma GCC system_header
48 
49 /**
50  * @defgroup memory Memory
51  * @ingroup utilities
52  *
53  * Components for memory allocation, deallocation, and management.
54  */
55 
56 /**
57  * @defgroup pointer_abstractions Pointer Abstractions
58  * @ingroup memory
59  *
60  * Smart pointers, etc.
61  */
62 
63 #include <bits/stl_algobase.h>
64 #include <bits/allocator.h>
65 #include <bits/stl_construct.h>
66 #include <bits/stl_uninitialized.h>
67 #include <bits/stl_tempbuf.h>
68 #include <bits/stl_raw_storage_iter.h>
69 #include <bits/ranges_uninitialized.h>
70 
71 #if __cplusplus >= 201103L
72 # include <exception> // std::exception
73 # include <typeinfo> // std::type_info in get_deleter
74 # include <iosfwd> // std::basic_ostream
75 # include <ext/atomicity.h>
76 # include <ext/concurrence.h>
77 # include <bits/functexcept.h>
78 # include <bits/stl_function.h> // std::less
79 # include <bits/uses_allocator.h>
80 # include <bits/alloc_traits.h>
81 # include <type_traits>
82 # include <debug/debug.h>
83 # include <bits/unique_ptr.h>
84 # include <bits/shared_ptr.h>
85 # include <bits/shared_ptr_atomic.h>
86 # if _GLIBCXX_USE_DEPRECATED
87 # include <backward/auto_ptr.h>
88 # endif
89 #else
90 # include <backward/auto_ptr.h>
91 #endif
92 
93 #if __cplusplus >= 201103L
94 #include <cstdint>
95 #if __cplusplus > 201703L
96 # include <bit> // for has_single_bit
97 # include <new> // for placement operator new
98 # include <tuple> // for tuple, make_tuple, make_from_tuple
99 #endif
100 namespace std _GLIBCXX_VISIBILITY(default)
101 {
102 _GLIBCXX_BEGIN_NAMESPACE_VERSION
103 
104 /**
105  * @brief Fit aligned storage in buffer.
106  * @ingroup memory
107  *
108  * This function tries to fit @a __size bytes of storage with alignment
109  * @a __align into the buffer @a __ptr of size @a __space bytes. If such
110  * a buffer fits then @a __ptr is changed to point to the first byte of the
111  * aligned storage and @a __space is reduced by the bytes used for alignment.
112  *
113  * C++11 20.6.5 [ptr.align]
114  *
115  * @param __align A fundamental or extended alignment value.
116  * @param __size Size of the aligned storage required.
117  * @param __ptr Pointer to a buffer of @a __space bytes.
118  * @param __space Size of the buffer pointed to by @a __ptr.
119  * @return the updated pointer if the aligned storage fits, otherwise nullptr.
120  *
121  */
122 inline void*
123 align(size_t __align, size_t __size, void*& __ptr, size_t& __space) noexcept
124 {
125 #ifdef _GLIBCXX_USE_C99_STDINT_TR1
126  const auto __intptr = reinterpret_cast<uintptr_t>(__ptr);
127 #else
128  // Cannot use std::uintptr_t so assume that std::size_t can be used instead.
129  static_assert(sizeof(size_t) >= sizeof(void*),
130  "std::size_t must be a suitable substitute for std::uintptr_t");
131  const auto __intptr = reinterpret_cast<unsigned long long>(__ptr);
132 #endif
133  const auto __aligned = (__intptr - 1u + __align) & -__align;
134  const auto __diff = __aligned - __intptr;
135  if ((__size + __diff) > __space)
136  return nullptr;
137  else
138  {
139  __space -= __diff;
140  return __ptr = reinterpret_cast<void*>(__aligned);
141  }
142 }
143 
144 /** @defgroup ptr_safety Pointer Safety and Garbage Collection
145  * @ingroup memory
146  *
147  * Utilities to assist with garbage collection in an implementation
148  * that supports <em>strict pointer safety</em>.
149  * This implementation only supports <em>relaxed pointer safety</em>
150  * and so these functions have no effect.
151  *
152  * C++11 20.6.4 [util.dynamic.safety], Pointer safety
153  *
154  * @{
155  */
156 
157 /// Constants representing the different types of pointer safety.
158 enum class pointer_safety { relaxed, preferred, strict };
159 
160 /// Inform a garbage collector that an object is still in use.
161 inline void
162 declare_reachable(void*) { }
163 
164 /// Unregister an object previously registered with declare_reachable.
165 template <typename _Tp>
166  inline _Tp*
167  undeclare_reachable(_Tp* __p) { return __p; }
168 
169 /// Inform a garbage collector that a region of memory need not be traced.
170 inline void
171 declare_no_pointers(char*, size_t) { }
172 
173 /// Unregister a range previously registered with declare_no_pointers.
174 inline void
175 undeclare_no_pointers(char*, size_t) { }
176 
177 /// The type of pointer safety supported by the implementation.
178 inline pointer_safety
179 get_pointer_safety() noexcept { return pointer_safety::relaxed; }
180 /// @}
181 
182 #if __cplusplus > 201703L
183 #define __cpp_lib_assume_aligned 201811L
184  /** @brief Inform the compiler that a pointer is aligned.
185  *
186  * @tparam _Align An alignment value (i.e. a power of two)
187  * @tparam _Tp An object type
188  * @param __ptr A pointer that is aligned to _Align
189  *
190  * C++20 20.10.6 [ptr.align]
191  *
192  * @ingroup memory
193  */
194  template<size_t _Align, class _Tp>
195  [[nodiscard,__gnu__::__always_inline__]]
196  constexpr _Tp*
197  assume_aligned(_Tp* __ptr) noexcept
198  {
199  static_assert(std::has_single_bit(_Align));
200  if (std::is_constant_evaluated())
201  return __ptr;
202  else
203  {
204  // This function is expected to be used in hot code, where
205  // __glibcxx_assert would add unwanted overhead.
206  _GLIBCXX_DEBUG_ASSERT((std::uintptr_t)__ptr % _Align == 0);
207  return static_cast<_Tp*>(__builtin_assume_aligned(__ptr, _Align));
208  }
209  }
210 #endif // C++2a
211 
212 #if __cplusplus > 201703L
213  template<typename _Tp>
214  struct __is_pair : false_type { };
215  template<typename _Tp, typename _Up>
216  struct __is_pair<pair<_Tp, _Up>> : true_type { };
217  template<typename _Tp, typename _Up>
218  struct __is_pair<const pair<_Tp, _Up>> : true_type { };
219 
220 /** @addtogroup allocators
221  * @{
222  */
223  template<typename _Tp, typename __ = _Require<__not_<__is_pair<_Tp>>>,
224  typename _Alloc, typename... _Args>
225  constexpr auto
226  __uses_alloc_args(const _Alloc& __a, _Args&&... __args) noexcept
227  {
228  if constexpr (uses_allocator_v<remove_cv_t<_Tp>, _Alloc>)
229  {
230  if constexpr (is_constructible_v<_Tp, allocator_arg_t,
231  const _Alloc&, _Args...>)
232  {
233  return tuple<allocator_arg_t, const _Alloc&, _Args&&...>(
234  allocator_arg, __a, std::forward<_Args>(__args)...);
235  }
236  else
237  {
238  static_assert(is_constructible_v<_Tp, _Args..., const _Alloc&>,
239  "construction with an allocator must be possible"
240  " if uses_allocator is true");
241 
242  return tuple<_Args&&..., const _Alloc&>(
243  std::forward<_Args>(__args)..., __a);
244  }
245  }
246  else
247  {
248  static_assert(is_constructible_v<_Tp, _Args...>);
249 
250  return tuple<_Args&&...>(std::forward<_Args>(__args)...);
251  }
252  }
253 
254 #if __cpp_concepts
255  template<typename _Tp>
256  concept _Std_pair = __is_pair<_Tp>::value;
257 #endif
258 
259 // This is a temporary workaround until -fconcepts is implied by -std=gnu++2a
260 #if __cpp_concepts
261 # define _GLIBCXX_STD_PAIR_CONSTRAINT(T) _Std_pair T
262 # define _GLIBCXX_STD_PAIR_CONSTRAINT_(T) _Std_pair T
263 #else
264 # define _GLIBCXX_STD_PAIR_CONSTRAINT(T) \
265  typename T, typename __ = _Require<__is_pair<T>>
266 # define _GLIBCXX_STD_PAIR_CONSTRAINT_(T) typename T, typename
267 #endif
268 
269  template<typename _Tp,
270 #if ! __cpp_concepts
271  typename __ = _Require<__not_<__is_pair<_Tp>>>,
272 #endif
273  typename _Alloc, typename... _Args>
274  constexpr auto
275  uses_allocator_construction_args(const _Alloc& __a,
276  _Args&&... __args) noexcept
277 #if __cpp_concepts
278  requires (! _Std_pair<_Tp>)
279 #endif
280  {
281  return std::__uses_alloc_args<_Tp>(__a, std::forward<_Args>(__args)...);
282  }
283 
284  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
285  typename _Tuple1, typename _Tuple2>
286  constexpr auto
287  uses_allocator_construction_args(const _Alloc& __a, piecewise_construct_t,
288  _Tuple1&& __x, _Tuple2&& __y) noexcept;
289 
290  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc>
291  constexpr auto
292  uses_allocator_construction_args(const _Alloc&) noexcept;
293 
294  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
295  typename _Up, typename _Vp>
296  constexpr auto
297  uses_allocator_construction_args(const _Alloc&, _Up&&, _Vp&&) noexcept;
298 
299  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
300  typename _Up, typename _Vp>
301  constexpr auto
302  uses_allocator_construction_args(const _Alloc&,
303  const pair<_Up, _Vp>&) noexcept;
304 
305  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
306  typename _Up, typename _Vp>
307  constexpr auto
308  uses_allocator_construction_args(const _Alloc&, pair<_Up, _Vp>&&) noexcept;
309 
310  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
311  typename _Tuple1, typename _Tuple2>
312  constexpr auto
313  uses_allocator_construction_args(const _Alloc& __a, piecewise_construct_t,
314  _Tuple1&& __x, _Tuple2&& __y) noexcept
315  {
316  using _Tp1 = typename _Tp::first_type;
317  using _Tp2 = typename _Tp::second_type;
318 
319  return std::make_tuple(piecewise_construct,
320  std::apply([&__a](auto&&... __args1) {
321  return std::uses_allocator_construction_args<_Tp1>(
322  __a, std::forward<decltype(__args1)>(__args1)...);
323  }, std::forward<_Tuple1>(__x)),
324  std::apply([&__a](auto&&... __args2) {
325  return std::uses_allocator_construction_args<_Tp2>(
326  __a, std::forward<decltype(__args2)>(__args2)...);
327  }, std::forward<_Tuple2>(__y)));
328  }
329 
330  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc>
331  constexpr auto
332  uses_allocator_construction_args(const _Alloc& __a) noexcept
333  {
334  using _Tp1 = typename _Tp::first_type;
335  using _Tp2 = typename _Tp::second_type;
336 
337  return std::make_tuple(piecewise_construct,
338  std::uses_allocator_construction_args<_Tp1>(__a),
339  std::uses_allocator_construction_args<_Tp2>(__a));
340  }
341 
342  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
343  typename _Up, typename _Vp>
344  constexpr auto
345  uses_allocator_construction_args(const _Alloc& __a, _Up&& __u, _Vp&& __v)
346  noexcept
347  {
348  using _Tp1 = typename _Tp::first_type;
349  using _Tp2 = typename _Tp::second_type;
350 
351  return std::make_tuple(piecewise_construct,
352  std::uses_allocator_construction_args<_Tp1>(__a,
353  std::forward<_Up>(__u)),
354  std::uses_allocator_construction_args<_Tp2>(__a,
355  std::forward<_Vp>(__v)));
356  }
357 
358  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
359  typename _Up, typename _Vp>
360  constexpr auto
361  uses_allocator_construction_args(const _Alloc& __a,
362  const pair<_Up, _Vp>& __pr) noexcept
363  {
364  using _Tp1 = typename _Tp::first_type;
365  using _Tp2 = typename _Tp::second_type;
366 
367  return std::make_tuple(piecewise_construct,
368  std::uses_allocator_construction_args<_Tp1>(__a, __pr.first),
369  std::uses_allocator_construction_args<_Tp2>(__a, __pr.second));
370  }
371 
372  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
373  typename _Up, typename _Vp>
374  constexpr auto
375  uses_allocator_construction_args(const _Alloc& __a,
376  pair<_Up, _Vp>&& __pr) noexcept
377  {
378  using _Tp1 = typename _Tp::first_type;
379  using _Tp2 = typename _Tp::second_type;
380 
381  return std::make_tuple(piecewise_construct,
382  std::uses_allocator_construction_args<_Tp1>(__a,
383  std::move(__pr).first),
384  std::uses_allocator_construction_args<_Tp2>(__a,
385  std::move(__pr).second));
386  }
387 
388  template<typename _Tp, typename _Alloc, typename... _Args>
389  inline _Tp
390  make_obj_using_allocator(const _Alloc& __a, _Args&&... __args)
391  {
392  return std::make_from_tuple<_Tp>(
393  std::uses_allocator_construction_args<_Tp>(__a,
394  std::forward<_Args>(__args)...));
395  }
396 
397  template<typename _Tp, typename _Alloc, typename... _Args>
398  inline _Tp*
399  uninitialized_construct_using_allocator(_Tp* __p, const _Alloc& __a,
400  _Args&&... __args)
401  {
402  return std::apply([&](auto&&... __xs) {
403  return std::construct_at(__p, std::forward<decltype(__xs)>(__xs)...);
404  }, std::uses_allocator_construction_args<_Tp>(__a,
405  std::forward<_Args>(__args)...));
406  }
407 // @}
408 
409 #endif // C++2a
410 
411 _GLIBCXX_END_NAMESPACE_VERSION
412 } // namespace
413 #endif // C++11
414 
415 #if __cplusplus > 201402L
416 // Parallel STL algorithms
417 # if _PSTL_EXECUTION_POLICIES_DEFINED
418 // If <execution> has already been included, pull in implementations
419 # include <pstl/glue_memory_impl.h>
420 # else
421 // Otherwise just pull in forward declarations
422 # include <pstl/glue_memory_defs.h>
423 # endif
424 
425 // Feature test macro for parallel algorithms
426 # define __cpp_lib_parallel_algorithm 201603L
427 #endif // C++17
428 
429 #endif /* _GLIBCXX_MEMORY */