libstdc++
experimental/memory_resource
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1// <experimental/memory_resource> -*- C++ -*-
2
3// Copyright (C) 2015-2020 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/** @file experimental/memory_resource
26 * This is a TS C++ Library header.
27 * @ingroup libfund-ts
28 */
29
30#ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
31#define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
32
33#pragma GCC system_header
34
35#if __cplusplus >= 201402L
36
37#include <memory> // align, uses_allocator, __uses_alloc
38#include <experimental/utility> // pair, experimental::erased_type
39#include <atomic> // atomic
40#include <new> // placement new
41#include <cstddef> // max_align_t
42#include <ext/new_allocator.h>
43#include <debug/assertions.h>
44
45/// @cond
46namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
47{
48_GLIBCXX_BEGIN_NAMESPACE_VERSION
49 template<typename _Tp> class malloc_allocator;
50_GLIBCXX_END_NAMESPACE_VERSION
51} // namespace __gnu_cxx
52/// @endcond
53
54namespace std {
55_GLIBCXX_BEGIN_NAMESPACE_VERSION
56
57namespace experimental {
58inline namespace fundamentals_v2 {
59namespace pmr {
60#define __cpp_lib_experimental_memory_resources 201402L
61
62 // Standard memory resources
63
64 // 8.5 Class memory_resource
65 class memory_resource;
66
67 // 8.6 Class template polymorphic_allocator
68 template<typename _Tp>
69 class polymorphic_allocator;
70
71 template<typename _Alloc, typename _Resource = memory_resource>
72 class __resource_adaptor_imp;
73
74 // 8.7 Alias template resource_adaptor
75 template<typename _Alloc>
76 using resource_adaptor = __resource_adaptor_imp<
77 typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
78
79 // 8.8 Global memory resources
80 memory_resource* new_delete_resource() noexcept;
81 memory_resource* null_memory_resource() noexcept;
82 memory_resource* get_default_resource() noexcept;
83 memory_resource* set_default_resource(memory_resource* __r) noexcept;
84
85 // TODO 8.9 Pool resource classes
86
87 class memory_resource
88 {
89 static constexpr size_t _S_max_align = alignof(max_align_t);
90
91 public:
92 memory_resource() = default;
93 memory_resource(const memory_resource&) = default;
94 virtual ~memory_resource() = default;
95
96 memory_resource& operator=(const memory_resource&) = default;
97
98 _GLIBCXX_NODISCARD void*
99 allocate(size_t __bytes, size_t __alignment = _S_max_align)
100 { return do_allocate(__bytes, __alignment); }
101
102 void
103 deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
104 { return do_deallocate(__p, __bytes, __alignment); }
105
106 bool
107 is_equal(const memory_resource& __other) const noexcept
108 { return do_is_equal(__other); }
109
110 protected:
111 virtual void*
112 do_allocate(size_t __bytes, size_t __alignment) = 0;
113
114 virtual void
115 do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
116
117 virtual bool
118 do_is_equal(const memory_resource& __other) const noexcept = 0;
119 };
120
121 inline bool
122 operator==(const memory_resource& __a, const memory_resource& __b) noexcept
123 { return &__a == &__b || __a.is_equal(__b); }
124
125 inline bool
126 operator!=(const memory_resource& __a, const memory_resource& __b) noexcept
127 { return !(__a == __b); }
128
129
130 template<typename _Tp>
131 class polymorphic_allocator
132 {
133 public:
134 using value_type = _Tp;
135
136 polymorphic_allocator() noexcept
137 : _M_resource(get_default_resource())
138 { }
139
140 polymorphic_allocator(memory_resource* __r)
141 : _M_resource(__r)
142 { _GLIBCXX_DEBUG_ASSERT(__r); }
143
144 polymorphic_allocator(const polymorphic_allocator& __other) = default;
145
146 template <typename _Up>
147 polymorphic_allocator(const polymorphic_allocator<_Up>&
148 __other) noexcept
149 : _M_resource(__other.resource())
150 { }
151
152 polymorphic_allocator&
153 operator=(const polymorphic_allocator& __rhs) = default;
154
155 _GLIBCXX_NODISCARD _Tp* allocate(size_t __n)
156 { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
157 alignof(_Tp))); }
158
159 void
160 deallocate(_Tp* __p, size_t __n)
161 { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
162
163 template <typename _Tp1, typename... _Args> //used here
164 void
165 construct(_Tp1* __p, _Args&&... __args)
166 {
167 std::__uses_allocator_construct(this->resource(), __p,
168 std::forward<_Args>(__args)...);
169 }
170
171 // Specializations for pair using piecewise construction
172 template <typename _Tp1, typename _Tp2,
173 typename... _Args1, typename... _Args2>
174 void
175 construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
176 tuple<_Args1...> __x, tuple<_Args2...> __y)
177 {
178 memory_resource* const __resource = this->resource();
179 auto __x_use_tag =
180 std::__use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
181 auto __y_use_tag =
182 std::__use_alloc<_Tp2, memory_resource*, _Args2...>(__resource);
183
185 _M_construct_p(__x_use_tag, __x),
186 _M_construct_p(__y_use_tag, __y));
187 }
188
189 template <typename _Tp1, typename _Tp2>
190 void
191 construct(pair<_Tp1,_Tp2>* __p)
192 { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
193
194 template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
195 void
196 construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
197 {
198 this->construct(__p, piecewise_construct,
199 forward_as_tuple(std::forward<_Up>(__x)),
200 forward_as_tuple(std::forward<_Vp>(__y)));
201 }
202
203 template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
204 void
205 construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
206 {
207 this->construct(__p, piecewise_construct,
210 }
211
212 template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
213 void
214 construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
215 {
216 this->construct(__p, piecewise_construct,
217 forward_as_tuple(std::forward<_Up>(__pr.first)),
218 forward_as_tuple(std::forward<_Vp>(__pr.second)));
219 }
220
221 template <typename _Up>
222 void
223 destroy(_Up* __p)
224 { __p->~_Up(); }
225
226 // Return a default-constructed allocator (no allocator propagation)
227 polymorphic_allocator
228 select_on_container_copy_construction() const
229 { return polymorphic_allocator(); }
230
231 memory_resource* resource() const { return _M_resource; }
232
233 private:
234 using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
235 using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
236
237 template<typename _Tuple>
238 _Tuple&&
239 _M_construct_p(__uses_alloc0, _Tuple& __t)
240 { return std::move(__t); }
241
242 template<typename... _Args>
243 decltype(auto)
244 _M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
245 { return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
246 std::move(__t)); }
247
248 template<typename... _Args>
249 decltype(auto)
250 _M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
251 { return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
252
253 memory_resource* _M_resource;
254 };
255
256 template <class _Tp1, class _Tp2>
257 bool
258 operator==(const polymorphic_allocator<_Tp1>& __a,
259 const polymorphic_allocator<_Tp2>& __b) noexcept
260 { return *__a.resource() == *__b.resource(); }
261
262 template <class _Tp1, class _Tp2>
263 bool
264 operator!=(const polymorphic_allocator<_Tp1>& __a,
265 const polymorphic_allocator<_Tp2>& __b) noexcept
266 { return !(__a == __b); }
267
268
269 /// @cond undocumented
270 class __resource_adaptor_common
271 {
272 template<typename, typename> friend class __resource_adaptor_imp;
273
274 struct _AlignMgr
275 {
276 _AlignMgr(size_t __nbytes, size_t __align)
277 : _M_nbytes(__nbytes), _M_align(__align)
278 { }
279
280 // Total size that needs to be allocated.
281 size_t
282 _M_alloc_size() const { return _M_buf_size() + _M_token_size(); }
283
284 void*
285 _M_adjust(void* __ptr) const
286 {
287 const auto __orig_ptr = static_cast<char*>(__ptr);
288 size_t __space = _M_buf_size();
289 // Align the pointer within the buffer:
290 std::align(_M_align, _M_nbytes, __ptr, __space);
291 const auto __aligned_ptr = static_cast<char*>(__ptr);
292 const auto __token_size = _M_token_size();
293 // Store token immediately after the aligned block:
294 char* const __end = __aligned_ptr + _M_nbytes;
295 if (__token_size == 1)
296 _S_write<unsigned char>(__end, __aligned_ptr - __orig_ptr);
297 else if (__token_size == sizeof(short))
298 _S_write<unsigned short>(__end, __aligned_ptr - __orig_ptr);
299 else if (__token_size == sizeof(int) && sizeof(int) < sizeof(char*))
300 _S_write<unsigned int>(__end, __aligned_ptr - __orig_ptr);
301 else // (__token_size == sizeof(char*))
302 // Just store the original pointer:
303 _S_write<char*>(__end, __orig_ptr);
304 return __aligned_ptr;
305 }
306
307 char*
308 _M_unadjust(char* __ptr) const
309 {
310 const char* const __end = __ptr + _M_nbytes;
311 char* __orig_ptr;
312 const auto __token_size = _M_token_size();
313 // Read the token and restore the original pointer:
314 if (__token_size == 1)
315 __orig_ptr = __ptr - _S_read<unsigned char>(__end);
316 else if (__token_size == sizeof(short))
317 __orig_ptr = __ptr - _S_read<unsigned short>(__end);
318 else if (__token_size == sizeof(int)
319 && sizeof(int) < sizeof(char*))
320 __orig_ptr = __ptr - _S_read<unsigned int>(__end);
321 else // (__token_size == sizeof(char*))
322 __orig_ptr = _S_read<char*>(__end);
323 // The adjustment is always less than the requested alignment,
324 // so if that isn't true now then either the wrong size was passed
325 // to deallocate or the token was overwritten by a buffer overflow:
326 __glibcxx_assert(static_cast<size_t>(__ptr - __orig_ptr) < _M_align);
327 return __orig_ptr;
328 }
329
330 private:
331 size_t _M_nbytes;
332 size_t _M_align;
333
334 // Number of bytes needed to fit block of given size and alignment.
335 size_t
336 _M_buf_size() const { return _M_nbytes + _M_align - 1; }
337
338 // Number of additional bytes needed to write the token.
339 int
340 _M_token_size() const
341 {
342 if (_M_align <= (1ul << __CHAR_BIT__))
343 return 1;
344 if (_M_align <= (1ul << (sizeof(short) * __CHAR_BIT__)))
345 return sizeof(short);
346 if (_M_align <= (1ull << (sizeof(int) * __CHAR_BIT__)))
347 return sizeof(int);
348 return sizeof(char*);
349 }
350
351 template<typename _Tp>
352 static void
353 _S_write(void* __to, _Tp __val)
354 { __builtin_memcpy(__to, &__val, sizeof(_Tp)); }
355
356 template<typename _Tp>
357 static _Tp
358 _S_read(const void* __from)
359 {
360 _Tp __val;
361 __builtin_memcpy(&__val, __from, sizeof(_Tp));
362 return __val;
363 }
364 };
365 };
366 /// @endcond
367
368 // 8.7.1 __resource_adaptor_imp
369 template<typename _Alloc, typename _Resource>
370 class __resource_adaptor_imp
371 : public _Resource, private __resource_adaptor_common
372 {
373 using memory_resource = _Resource;
374
375 static_assert(is_same<char,
377 "Allocator's value_type is char");
378 static_assert(is_same<char*,
379 typename allocator_traits<_Alloc>::pointer>::value,
380 "Allocator's pointer type is value_type*");
381 static_assert(is_same<const char*,
383 "Allocator's const_pointer type is value_type const*");
384 static_assert(is_same<void*,
386 "Allocator's void_pointer type is void*");
387 static_assert(is_same<const void*,
389 "Allocator's const_void_pointer type is void const*");
390
391 public:
392 using allocator_type = _Alloc;
393
394 __resource_adaptor_imp() = default;
395 __resource_adaptor_imp(const __resource_adaptor_imp&) = default;
396 __resource_adaptor_imp(__resource_adaptor_imp&&) = default;
397
398 explicit __resource_adaptor_imp(const _Alloc& __a2)
399 : _M_alloc(__a2)
400 { }
401
402 explicit __resource_adaptor_imp(_Alloc&& __a2)
403 : _M_alloc(std::move(__a2))
404 { }
405
406 __resource_adaptor_imp&
407 operator=(const __resource_adaptor_imp&) = default;
408
409 allocator_type get_allocator() const noexcept { return _M_alloc; }
410
411 protected:
412 virtual void*
413 do_allocate(size_t __bytes, size_t __alignment) override
414 {
415 // Cannot use max_align_t on 32-bit Solaris x86, see PR libstdc++/77691
416#if ! (defined __sun__ && defined __i386__)
417 if (__alignment == alignof(max_align_t))
418 return _M_allocate<alignof(max_align_t)>(__bytes);
419#endif
420 switch (__alignment)
421 {
422 case 1:
423 return _M_alloc.allocate(__bytes);
424 case 2:
425 return _M_allocate<2>(__bytes);
426 case 4:
427 return _M_allocate<4>(__bytes);
428 case 8:
429 return _M_allocate<8>(__bytes);
430 }
431 const _AlignMgr __mgr(__bytes, __alignment);
432 // Assume _M_alloc returns 1-byte aligned memory, so allocate enough
433 // space to fit a block of the right size and alignment, plus some
434 // extra bytes to store a token for retrieving the original pointer.
435 return __mgr._M_adjust(_M_alloc.allocate(__mgr._M_alloc_size()));
436 }
437
438 virtual void
439 do_deallocate(void* __ptr, size_t __bytes, size_t __alignment) noexcept
440 override
441 {
442#if ! (defined __sun__ && defined __i386__)
443 if (__alignment == alignof(max_align_t))
444 return (void) _M_deallocate<alignof(max_align_t)>(__ptr, __bytes);
445#endif
446 switch (__alignment)
447 {
448 case 1:
449 return (void) _M_alloc.deallocate((char*)__ptr, __bytes);
450 case 2:
451 return (void) _M_deallocate<2>(__ptr, __bytes);
452 case 4:
453 return (void) _M_deallocate<4>(__ptr, __bytes);
454 case 8:
455 return (void) _M_deallocate<8>(__ptr, __bytes);
456 }
457 const _AlignMgr __mgr(__bytes, __alignment);
458 // Use the stored token to retrieve the original pointer.
459 _M_alloc.deallocate(__mgr._M_unadjust((char*)__ptr),
460 __mgr._M_alloc_size());
461 }
462
463 virtual bool
464 do_is_equal(const memory_resource& __other) const noexcept override
465 {
466 if (auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other))
467 return _M_alloc == __p->_M_alloc;
468 return false;
469 }
470
471 private:
472 template<size_t _Num>
473 struct _Aligned_type { alignas(_Num) char __c[_Num]; };
474
475 // Rebind the allocator to the specified type and use it to allocate.
476 template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
477 void*
478 _M_allocate(size_t __bytes)
479 {
480 typename allocator_traits<_Alloc>::template
481 rebind_alloc<_Tp> __a2(_M_alloc);
482 const size_t __n = (__bytes + _Num - 1) / _Num;
483 return __a2.allocate(__n);
484 }
485
486 // Rebind the allocator to the specified type and use it to deallocate.
487 template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
488 void
489 _M_deallocate(void* __ptr, size_t __bytes) noexcept
490 {
491 typename allocator_traits<_Alloc>::template
492 rebind_alloc<_Tp> __a2(_M_alloc);
493 const size_t __n = (__bytes + _Num - 1) / _Num;
494 __a2.deallocate((_Tp*)__ptr, __n);
495 }
496
497 _Alloc _M_alloc{};
498 };
499
500 // Global memory resources
501
502 inline memory_resource*
503 new_delete_resource() noexcept
504 {
505 using type = resource_adaptor<__gnu_cxx::new_allocator<char>>;
506 alignas(type) static unsigned char __buf[sizeof(type)];
507 static type* __r = new(__buf) type;
508 return __r;
509 }
510
511 inline memory_resource*
512 null_memory_resource() noexcept
513 {
514 class type final : public memory_resource
515 {
516 void*
517 do_allocate(size_t, size_t) override
518 { std::__throw_bad_alloc(); }
519
520 void
521 do_deallocate(void*, size_t, size_t) noexcept override
522 { }
523
524 bool
525 do_is_equal(const memory_resource& __other) const noexcept override
526 { return this == &__other; }
527 };
528
529 alignas(type) static unsigned char __buf[sizeof(type)];
530 static type* __r = new(__buf) type;
531 return __r;
532 }
533
534 // The default memory resource
535
536 /// @cond undocumented
538 __get_default_resource()
539 {
540 using type = atomic<memory_resource*>;
541 alignas(type) static unsigned char __buf[sizeof(type)];
542 static type* __r = new(__buf) type(new_delete_resource());
543 return *__r;
544 }
545 /// @endcond
546
547 /// Get the current default resource.
548 inline memory_resource*
550 { return __get_default_resource().load(); }
551
552 /// Change the default resource and return the previous one.
553 inline memory_resource*
554 set_default_resource(memory_resource* __r) noexcept
555 {
556 if (__r == nullptr)
557 __r = new_delete_resource();
558 return __get_default_resource().exchange(__r);
559 }
560
561} // namespace pmr
562} // namespace fundamentals_v2
563} // namespace experimental
564
565_GLIBCXX_END_NAMESPACE_VERSION
566} // namespace std
567#endif // C++14
568#endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
void * align(size_t __align, size_t __size, void *&__ptr, size_t &__space) noexcept
Fit aligned storage in buffer.
Definition: memory:123
_T1 first
The first member.
Definition: stl_pair.h:216
constexpr auto tuple_cat(_Tpls &&... __tpls) -> typename __tuple_cat_result< _Tpls... >::__type
tuple_cat
Definition: tuple:1600
constexpr tuple< _Elements &&... > forward_as_tuple(_Elements &&... __args) noexcept
std::forward_as_tuple
Definition: tuple:1485
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:101
_T2 second
The second member.
Definition: stl_pair.h:217
constexpr piecewise_construct_t piecewise_construct
Tag for piecewise construction of std::pair objects.
Definition: stl_pair.h:82
ISO C++ entities toplevel namespace is std.
GNU extensions for public use.
Generic atomic type, primary class template.
Definition: atomic:181
typename _Ptr< __v_pointer, void >::type void_pointer
The allocator's void pointer type.
__detected_or_t< value_type *, __pointer, _Alloc > pointer
The allocator's pointer type.
typename _Ptr< __cv_pointer, const void >::type const_void_pointer
The allocator's const void pointer type.
typename _Ptr< __c_pointer, const value_type >::type const_pointer
The allocator's const pointer type.
_Alloc::value_type value_type
The allocated type.
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:212
memory_resource * set_default_resource(memory_resource *__r) noexcept
Change the default resource and return the previous one.
memory_resource * get_default_resource() noexcept
Get the current default resource.