source: Daodan/MSYS2/mingw32/include/c++/11.2.0/memory_resource@ 1166

Last change on this file since 1166 was 1166, checked in by rossy, 3 years ago

Daodan: Replace MinGW build env with an up-to-date MSYS2 env
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1// <memory_resource> -*- C++ -*-
2
3// Copyright (C) 2018-2021 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/** @file include/memory_resource
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_MEMORY_RESOURCE
30#define _GLIBCXX_MEMORY_RESOURCE 1
31
32#pragma GCC system_header
33
34#if __cplusplus >= 201703L
35
36#include <vector> // vector
37#include <cstddef> // size_t, max_align_t, byte
38#include <shared_mutex> // shared_mutex
39#include <bits/align.h> // align
40#include <bits/functexcept.h> // __throw_bad_array_new_length
41#include <bits/uses_allocator.h> // __use_alloc
42#include <bits/uses_allocator_args.h> // uninitialized_construct_using_alloc
43#include <ext/numeric_traits.h>
44#include <debug/assertions.h>
45
46#if ! __cpp_lib_make_obj_using_allocator
47# include <utility> // pair, index_sequence
48# include <tuple> // tuple, forward_as_tuple
49#endif
50
51namespace std _GLIBCXX_VISIBILITY(default)
52{
53_GLIBCXX_BEGIN_NAMESPACE_VERSION
54namespace pmr
55{
56#ifdef _GLIBCXX_HAS_GTHREADS
57 // Header and all contents are present.
58# define __cpp_lib_memory_resource 201603L
59#else
60 // The pmr::synchronized_pool_resource type is missing.
61# define __cpp_lib_memory_resource 1
62#endif
63
64 class memory_resource;
65
66#if __cplusplus == 201703L
67 template<typename _Tp>
68 class polymorphic_allocator;
69#else // C++20
70# define __cpp_lib_polymorphic_allocator 201902L
71 template<typename _Tp = std::byte>
72 class polymorphic_allocator;
73#endif
74
75 // Global memory resources
76 memory_resource* new_delete_resource() noexcept;
77 memory_resource* null_memory_resource() noexcept;
78 memory_resource* set_default_resource(memory_resource* __r) noexcept;
79 memory_resource* get_default_resource() noexcept
80 __attribute__((__returns_nonnull__));
81
82 // Pool resource classes
83 struct pool_options;
84#ifdef _GLIBCXX_HAS_GTHREADS
85 class synchronized_pool_resource;
86#endif
87 class unsynchronized_pool_resource;
88 class monotonic_buffer_resource;
89
90 /// Class memory_resource
91 class memory_resource
92 {
93 static constexpr size_t _S_max_align = alignof(max_align_t);
94
95 public:
96 memory_resource() = default;
97 memory_resource(const memory_resource&) = default;
98 virtual ~memory_resource(); // key function
99
100 memory_resource& operator=(const memory_resource&) = default;
101
102 [[nodiscard]]
103 void*
104 allocate(size_t __bytes, size_t __alignment = _S_max_align)
105 __attribute__((__returns_nonnull__,__alloc_size__(2),__alloc_align__(3)))
106 { return do_allocate(__bytes, __alignment); }
107
108 void
109 deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
110 __attribute__((__nonnull__))
111 { return do_deallocate(__p, __bytes, __alignment); }
112
113 bool
114 is_equal(const memory_resource& __other) const noexcept
115 { return do_is_equal(__other); }
116
117 private:
118 virtual void*
119 do_allocate(size_t __bytes, size_t __alignment) = 0;
120
121 virtual void
122 do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
123
124 virtual bool
125 do_is_equal(const memory_resource& __other) const noexcept = 0;
126 };
127
128 inline bool
129 operator==(const memory_resource& __a, const memory_resource& __b) noexcept
130 { return &__a == &__b || __a.is_equal(__b); }
131
132#if __cpp_impl_three_way_comparison < 201907L
133 inline bool
134 operator!=(const memory_resource& __a, const memory_resource& __b) noexcept
135 { return !(__a == __b); }
136#endif
137
138 // C++17 23.12.3 Class template polymorphic_allocator
139 template<typename _Tp>
140 class polymorphic_allocator
141 {
142 // _GLIBCXX_RESOLVE_LIB_DEFECTS
143 // 2975. Missing case for pair construction in polymorphic allocators
144 template<typename _Up>
145 struct __not_pair { using type = void; };
146
147 template<typename _Up1, typename _Up2>
148 struct __not_pair<pair<_Up1, _Up2>> { };
149
150 public:
151 using value_type = _Tp;
152
153 polymorphic_allocator() noexcept
154 : _M_resource(get_default_resource())
155 { }
156
157 polymorphic_allocator(memory_resource* __r) noexcept
158 __attribute__((__nonnull__))
159 : _M_resource(__r)
160 { _GLIBCXX_DEBUG_ASSERT(__r); }
161
162 polymorphic_allocator(const polymorphic_allocator& __other) = default;
163
164 template<typename _Up>
165 polymorphic_allocator(const polymorphic_allocator<_Up>& __x) noexcept
166 : _M_resource(__x.resource())
167 { }
168
169 polymorphic_allocator&
170 operator=(const polymorphic_allocator&) = delete;
171
172 [[nodiscard]]
173 _Tp*
174 allocate(size_t __n)
175 __attribute__((__returns_nonnull__))
176 {
177 if ((__gnu_cxx::__int_traits<size_t>::__max / sizeof(_Tp)) < __n)
178 std::__throw_bad_array_new_length();
179 return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
180 alignof(_Tp)));
181 }
182
183 void
184 deallocate(_Tp* __p, size_t __n) noexcept
185 __attribute__((__nonnull__))
186 { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
187
188#if __cplusplus > 201703L
189 [[nodiscard]] void*
190 allocate_bytes(size_t __nbytes,
191 size_t __alignment = alignof(max_align_t))
192 { return _M_resource->allocate(__nbytes, __alignment); }
193
194 void
195 deallocate_bytes(void* __p, size_t __nbytes,
196 size_t __alignment = alignof(max_align_t))
197 { _M_resource->deallocate(__p, __nbytes, __alignment); }
198
199 template<typename _Up>
200 [[nodiscard]] _Up*
201 allocate_object(size_t __n = 1)
202 {
203 if ((__gnu_cxx::__int_traits<size_t>::__max / sizeof(_Up)) < __n)
204 std::__throw_bad_array_new_length();
205 return static_cast<_Up*>(allocate_bytes(__n * sizeof(_Up),
206 alignof(_Up)));
207 }
208
209 template<typename _Up>
210 void
211 deallocate_object(_Up* __p, size_t __n = 1)
212 { deallocate_bytes(__p, __n * sizeof(_Up), alignof(_Up)); }
213
214 template<typename _Up, typename... _CtorArgs>
215 [[nodiscard]] _Up*
216 new_object(_CtorArgs&&... __ctor_args)
217 {
218 _Up* __p = allocate_object<_Up>();
219 __try
220 {
221 construct(__p, std::forward<_CtorArgs>(__ctor_args)...);
222 }
223 __catch (...)
224 {
225 deallocate_object(__p);
226 __throw_exception_again;
227 }
228 return __p;
229 }
230
231 template<typename _Up>
232 void
233 delete_object(_Up* __p)
234 {
235 destroy(__p);
236 deallocate_object(__p);
237 }
238#endif // C++2a
239
240#if ! __cpp_lib_make_obj_using_allocator
241 template<typename _Tp1, typename... _Args>
242 __attribute__((__nonnull__))
243 typename __not_pair<_Tp1>::type
244 construct(_Tp1* __p, _Args&&... __args)
245 {
246 // _GLIBCXX_RESOLVE_LIB_DEFECTS
247 // 2969. polymorphic_allocator::construct() shouldn't pass resource()
248 using __use_tag
249 = std::__uses_alloc_t<_Tp1, polymorphic_allocator, _Args...>;
250 if constexpr (is_base_of_v<__uses_alloc0, __use_tag>)
251 ::new(__p) _Tp1(std::forward<_Args>(__args)...);
252 else if constexpr (is_base_of_v<__uses_alloc1_, __use_tag>)
253 ::new(__p) _Tp1(allocator_arg, *this,
254 std::forward<_Args>(__args)...);
255 else
256 ::new(__p) _Tp1(std::forward<_Args>(__args)..., *this);
257 }
258
259 template<typename _Tp1, typename _Tp2,
260 typename... _Args1, typename... _Args2>
261 __attribute__((__nonnull__))
262 void
263 construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
264 tuple<_Args1...> __x, tuple<_Args2...> __y)
265 {
266 auto __x_tag =
267 __use_alloc<_Tp1, polymorphic_allocator, _Args1...>(*this);
268 auto __y_tag =
269 __use_alloc<_Tp2, polymorphic_allocator, _Args2...>(*this);
270 index_sequence_for<_Args1...> __x_i;
271 index_sequence_for<_Args2...> __y_i;
272
273 ::new(__p) pair<_Tp1, _Tp2>(piecewise_construct,
274 _S_construct_p(__x_tag, __x_i, __x),
275 _S_construct_p(__y_tag, __y_i, __y));
276 }
277
278 template<typename _Tp1, typename _Tp2>
279 __attribute__((__nonnull__))
280 void
281 construct(pair<_Tp1, _Tp2>* __p)
282 { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
283
284 template<typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
285 __attribute__((__nonnull__))
286 void
287 construct(pair<_Tp1, _Tp2>* __p, _Up&& __x, _Vp&& __y)
288 {
289 this->construct(__p, piecewise_construct,
290 std::forward_as_tuple(std::forward<_Up>(__x)),
291 std::forward_as_tuple(std::forward<_Vp>(__y)));
292 }
293
294 template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
295 __attribute__((__nonnull__))
296 void
297 construct(pair<_Tp1, _Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
298 {
299 this->construct(__p, piecewise_construct,
300 std::forward_as_tuple(__pr.first),
301 std::forward_as_tuple(__pr.second));
302 }
303
304 template<typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
305 __attribute__((__nonnull__))
306 void
307 construct(pair<_Tp1, _Tp2>* __p, pair<_Up, _Vp>&& __pr)
308 {
309 this->construct(__p, piecewise_construct,
310 std::forward_as_tuple(std::forward<_Up>(__pr.first)),
311 std::forward_as_tuple(std::forward<_Vp>(__pr.second)));
312 }
313#else // make_obj_using_allocator
314 template<typename _Tp1, typename... _Args>
315 __attribute__((__nonnull__))
316 void
317 construct(_Tp1* __p, _Args&&... __args)
318 {
319 std::uninitialized_construct_using_allocator(__p, *this,
320 std::forward<_Args>(__args)...);
321 }
322#endif
323
324 template<typename _Up>
325 __attribute__((__nonnull__))
326 void
327 destroy(_Up* __p)
328 { __p->~_Up(); }
329
330 polymorphic_allocator
331 select_on_container_copy_construction() const noexcept
332 { return polymorphic_allocator(); }
333
334 memory_resource*
335 resource() const noexcept
336 __attribute__((__returns_nonnull__))
337 { return _M_resource; }
338
339 private:
340 using __uses_alloc1_ = __uses_alloc1<polymorphic_allocator>;
341 using __uses_alloc2_ = __uses_alloc2<polymorphic_allocator>;
342
343#if ! __cpp_lib_make_obj_using_allocator
344 template<typename _Ind, typename... _Args>
345 static tuple<_Args&&...>
346 _S_construct_p(__uses_alloc0, _Ind, tuple<_Args...>& __t)
347 { return std::move(__t); }
348
349 template<size_t... _Ind, typename... _Args>
350 static tuple<allocator_arg_t, polymorphic_allocator, _Args&&...>
351 _S_construct_p(__uses_alloc1_ __ua, index_sequence<_Ind...>,
352 tuple<_Args...>& __t)
353 {
354 return {
355 allocator_arg, *__ua._M_a, std::get<_Ind>(std::move(__t))...
356 };
357 }
358
359 template<size_t... _Ind, typename... _Args>
360 static tuple<_Args&&..., polymorphic_allocator>
361 _S_construct_p(__uses_alloc2_ __ua, index_sequence<_Ind...>,
362 tuple<_Args...>& __t)
363 { return { std::get<_Ind>(std::move(__t))..., *__ua._M_a }; }
364#endif
365
366 memory_resource* _M_resource;
367 };
368
369 template<typename _Tp1, typename _Tp2>
370 inline bool
371 operator==(const polymorphic_allocator<_Tp1>& __a,
372 const polymorphic_allocator<_Tp2>& __b) noexcept
373 { return *__a.resource() == *__b.resource(); }
374
375#if __cpp_impl_three_way_comparison < 201907L
376 template<typename _Tp1, typename _Tp2>
377 inline bool
378 operator!=(const polymorphic_allocator<_Tp1>& __a,
379 const polymorphic_allocator<_Tp2>& __b) noexcept
380 { return !(__a == __b); }
381#endif
382
383 /// Parameters for tuning a pool resource's behaviour.
384 struct pool_options
385 {
386 /** @brief Upper limit on number of blocks in a chunk.
387 *
388 * A lower value prevents allocating huge chunks that could remain mostly
389 * unused, but means pools will need to replenished more frequently.
390 */
391 size_t max_blocks_per_chunk = 0;
392
393 /* @brief Largest block size (in bytes) that should be served from pools.
394 *
395 * Larger allocations will be served directly by the upstream resource,
396 * not from one of the pools managed by the pool resource.
397 */
398 size_t largest_required_pool_block = 0;
399 };
400
401 // Common implementation details for un-/synchronized pool resources.
402 class __pool_resource
403 {
404 friend class synchronized_pool_resource;
405 friend class unsynchronized_pool_resource;
406
407 __pool_resource(const pool_options& __opts, memory_resource* __upstream);
408
409 ~__pool_resource();
410
411 __pool_resource(const __pool_resource&) = delete;
412 __pool_resource& operator=(const __pool_resource&) = delete;
413
414 // Allocate a large unpooled block.
415 void*
416 allocate(size_t __bytes, size_t __alignment);
417
418 // Deallocate a large unpooled block.
419 void
420 deallocate(void* __p, size_t __bytes, size_t __alignment);
421
422
423 // Deallocate unpooled memory.
424 void release() noexcept;
425
426 memory_resource* resource() const noexcept
427 { return _M_unpooled.get_allocator().resource(); }
428
429 struct _Pool;
430
431 _Pool* _M_alloc_pools();
432
433 const pool_options _M_opts;
434
435 struct _BigBlock;
436 // Collection of blocks too big for any pool, sorted by address.
437 // This also stores the only copy of the upstream memory resource pointer.
438 _GLIBCXX_STD_C::pmr::vector<_BigBlock> _M_unpooled;
439
440 const int _M_npools;
441 };
442
443#ifdef _GLIBCXX_HAS_GTHREADS
444 /// A thread-safe memory resource that manages pools of fixed-size blocks.
445 class synchronized_pool_resource : public memory_resource
446 {
447 public:
448 synchronized_pool_resource(const pool_options& __opts,
449 memory_resource* __upstream)
450 __attribute__((__nonnull__));
451
452 synchronized_pool_resource()
453 : synchronized_pool_resource(pool_options(), get_default_resource())
454 { }
455
456 explicit
457 synchronized_pool_resource(memory_resource* __upstream)
458 __attribute__((__nonnull__))
459 : synchronized_pool_resource(pool_options(), __upstream)
460 { }
461
462 explicit
463 synchronized_pool_resource(const pool_options& __opts)
464 : synchronized_pool_resource(__opts, get_default_resource()) { }
465
466 synchronized_pool_resource(const synchronized_pool_resource&) = delete;
467
468 virtual ~synchronized_pool_resource();
469
470 synchronized_pool_resource&
471 operator=(const synchronized_pool_resource&) = delete;
472
473 void release();
474
475 memory_resource*
476 upstream_resource() const noexcept
477 __attribute__((__returns_nonnull__))
478 { return _M_impl.resource(); }
479
480 pool_options options() const noexcept { return _M_impl._M_opts; }
481
482 protected:
483 void*
484 do_allocate(size_t __bytes, size_t __alignment) override;
485
486 void
487 do_deallocate(void* __p, size_t __bytes, size_t __alignment) override;
488
489 bool
490 do_is_equal(const memory_resource& __other) const noexcept override
491 { return this == &__other; }
492
493 public:
494 // Thread-specific pools (only public for access by implementation details)
495 struct _TPools;
496
497 private:
498 _TPools* _M_alloc_tpools(lock_guard<shared_mutex>&);
499 _TPools* _M_alloc_shared_tpools(lock_guard<shared_mutex>&);
500 auto _M_thread_specific_pools() noexcept;
501
502 __pool_resource _M_impl;
503 __gthread_key_t _M_key;
504 // Linked list of thread-specific pools. All threads share _M_tpools[0].
505 _TPools* _M_tpools = nullptr;
506 mutable shared_mutex _M_mx;
507 };
508#endif
509
510 /// A non-thread-safe memory resource that manages pools of fixed-size blocks.
511 class unsynchronized_pool_resource : public memory_resource
512 {
513 public:
514 [[__gnu__::__nonnull__]]
515 unsynchronized_pool_resource(const pool_options& __opts,
516 memory_resource* __upstream);
517
518 unsynchronized_pool_resource()
519 : unsynchronized_pool_resource(pool_options(), get_default_resource())
520 { }
521
522 [[__gnu__::__nonnull__]]
523 explicit
524 unsynchronized_pool_resource(memory_resource* __upstream)
525 : unsynchronized_pool_resource(pool_options(), __upstream)
526 { }
527
528 explicit
529 unsynchronized_pool_resource(const pool_options& __opts)
530 : unsynchronized_pool_resource(__opts, get_default_resource()) { }
531
532 unsynchronized_pool_resource(const unsynchronized_pool_resource&) = delete;
533
534 virtual ~unsynchronized_pool_resource();
535
536 unsynchronized_pool_resource&
537 operator=(const unsynchronized_pool_resource&) = delete;
538
539 void release();
540
541 [[__gnu__::__returns_nonnull__]]
542 memory_resource*
543 upstream_resource() const noexcept
544 { return _M_impl.resource(); }
545
546 pool_options options() const noexcept { return _M_impl._M_opts; }
547
548 protected:
549 void*
550 do_allocate(size_t __bytes, size_t __alignment) override;
551
552 void
553 do_deallocate(void* __p, size_t __bytes, size_t __alignment) override;
554
555 bool
556 do_is_equal(const memory_resource& __other) const noexcept override
557 { return this == &__other; }
558
559 private:
560 using _Pool = __pool_resource::_Pool;
561
562 auto _M_find_pool(size_t) noexcept;
563
564 __pool_resource _M_impl;
565 _Pool* _M_pools = nullptr;
566 };
567
568 class monotonic_buffer_resource : public memory_resource
569 {
570 public:
571 explicit
572 monotonic_buffer_resource(memory_resource* __upstream) noexcept
573 __attribute__((__nonnull__))
574 : _M_upstream(__upstream)
575 { _GLIBCXX_DEBUG_ASSERT(__upstream != nullptr); }
576
577 monotonic_buffer_resource(size_t __initial_size,
578 memory_resource* __upstream) noexcept
579 __attribute__((__nonnull__))
580 : _M_next_bufsiz(__initial_size),
581 _M_upstream(__upstream)
582 {
583 _GLIBCXX_DEBUG_ASSERT(__upstream != nullptr);
584 _GLIBCXX_DEBUG_ASSERT(__initial_size > 0);
585 }
586
587 monotonic_buffer_resource(void* __buffer, size_t __buffer_size,
588 memory_resource* __upstream) noexcept
589 __attribute__((__nonnull__(4)))
590 : _M_current_buf(__buffer), _M_avail(__buffer_size),
591 _M_next_bufsiz(_S_next_bufsize(__buffer_size)),
592 _M_upstream(__upstream),
593 _M_orig_buf(__buffer), _M_orig_size(__buffer_size)
594 {
595 _GLIBCXX_DEBUG_ASSERT(__upstream != nullptr);
596 _GLIBCXX_DEBUG_ASSERT(__buffer != nullptr || __buffer_size == 0);
597 }
598
599 monotonic_buffer_resource() noexcept
600 : monotonic_buffer_resource(get_default_resource())
601 { }
602
603 explicit
604 monotonic_buffer_resource(size_t __initial_size) noexcept
605 : monotonic_buffer_resource(__initial_size, get_default_resource())
606 { }
607
608 monotonic_buffer_resource(void* __buffer, size_t __buffer_size) noexcept
609 : monotonic_buffer_resource(__buffer, __buffer_size, get_default_resource())
610 { }
611
612 monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
613
614 virtual ~monotonic_buffer_resource(); // key function
615
616 monotonic_buffer_resource&
617 operator=(const monotonic_buffer_resource&) = delete;
618
619 void
620 release() noexcept
621 {
622 if (_M_head)
623 _M_release_buffers();
624
625 // reset to initial state at contruction:
626 if ((_M_current_buf = _M_orig_buf))
627 {
628 _M_avail = _M_orig_size;
629 _M_next_bufsiz = _S_next_bufsize(_M_orig_size);
630 }
631 else
632 {
633 _M_avail = 0;
634 _M_next_bufsiz = _M_orig_size;
635 }
636 }
637
638 memory_resource*
639 upstream_resource() const noexcept
640 __attribute__((__returns_nonnull__))
641 { return _M_upstream; }
642
643 protected:
644 void*
645 do_allocate(size_t __bytes, size_t __alignment) override
646 {
647 if (__builtin_expect(__bytes == 0, false))
648 __bytes = 1; // Ensures we don't return the same pointer twice.
649
650 void* __p = std::align(__alignment, __bytes, _M_current_buf, _M_avail);
651 if (__builtin_expect(__p == nullptr, false))
652 {
653 _M_new_buffer(__bytes, __alignment);
654 __p = _M_current_buf;
655 }
656 _M_current_buf = (char*)_M_current_buf + __bytes;
657 _M_avail -= __bytes;
658 return __p;
659 }
660
661 void
662 do_deallocate(void*, size_t, size_t) override
663 { }
664
665 bool
666 do_is_equal(const memory_resource& __other) const noexcept override
667 { return this == &__other; }
668
669 private:
670 // Update _M_current_buf and _M_avail to refer to a new buffer with
671 // at least the specified size and alignment, allocated from upstream.
672 void
673 _M_new_buffer(size_t __bytes, size_t __alignment);
674
675 // Deallocate all buffers obtained from upstream.
676 void
677 _M_release_buffers() noexcept;
678
679 static size_t
680 _S_next_bufsize(size_t __buffer_size) noexcept
681 {
682 if (__builtin_expect(__buffer_size == 0, false))
683 __buffer_size = 1;
684 return __buffer_size * _S_growth_factor;
685 }
686
687 static constexpr size_t _S_init_bufsize = 128 * sizeof(void*);
688 static constexpr float _S_growth_factor = 1.5;
689
690 void* _M_current_buf = nullptr;
691 size_t _M_avail = 0;
692 size_t _M_next_bufsiz = _S_init_bufsize;
693
694 // Initial values set at construction and reused by release():
695 memory_resource* const _M_upstream;
696 void* const _M_orig_buf = nullptr;
697 size_t const _M_orig_size = _M_next_bufsiz;
698
699 class _Chunk;
700 _Chunk* _M_head = nullptr;
701 };
702
703} // namespace pmr
704_GLIBCXX_END_NAMESPACE_VERSION
705} // namespace std
706
707#endif // C++17
708#endif // _GLIBCXX_MEMORY_RESOURCE
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