1 // Experimental shared_ptr with array support -*- C++ -*-
2
3 // Copyright (C) 2015-2018 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/bits/shared_ptr.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{experimental/memory}
28 */
29
30 #ifndef _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H
31 #define _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H 1
32
33 #pragma GCC system_header
34
35 #if __cplusplus >= 201402L
36
37 #include <memory>
38 #include <experimental/type_traits>
39
_GLIBCXX_VISIBILITY(default)40 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43
44 namespace experimental
45 {
46 inline namespace fundamentals_v2
47 {
48 // 8.2.1
49
50 template<typename _Tp> class shared_ptr;
51 template<typename _Tp> class weak_ptr;
52 template<typename _Tp> class enable_shared_from_this;
53
54 template<typename _Yp, typename _Tp>
55 constexpr bool __sp_compatible_v
56 = std::__sp_compatible_with<_Yp*, _Tp*>::value;
57
58 template<typename _Tp, typename _Yp>
59 constexpr bool __sp_is_constructible_v
60 = std::__sp_is_constructible<_Tp, _Yp>::value;
61
62 template<typename _Tp>
63 class shared_ptr : public __shared_ptr<_Tp>
64 {
65 using _Base_type = __shared_ptr<_Tp>;
66
67 public:
68 using element_type = typename _Base_type::element_type;
69
70 private:
71 // Constraint for construction from a pointer of type _Yp*:
72 template<typename _Yp>
73 using _SafeConv = enable_if_t<__sp_is_constructible_v<_Tp, _Yp>>;
74
75 template<typename _Tp1, typename _Res = void>
76 using _Compatible
77 = enable_if_t<__sp_compatible_v<_Tp1, _Tp>, _Res>;
78
79 template<typename _Tp1, typename _Del,
80 typename _Ptr = typename unique_ptr<_Tp1, _Del>::pointer,
81 typename _Res = void>
82 using _UniqCompatible = enable_if_t<
83 __sp_compatible_v<_Tp1, _Tp>
84 && experimental::is_convertible_v<_Ptr, element_type*>,
85 _Res>;
86
87 public:
88
89 // 8.2.1.1, shared_ptr constructors
90 constexpr shared_ptr() noexcept = default;
91
92 template<typename _Tp1, typename = _SafeConv<_Tp1>>
93 explicit
94 shared_ptr(_Tp1* __p) : _Base_type(__p)
95 { _M_enable_shared_from_this_with(__p); }
96
97 template<typename _Tp1, typename _Deleter, typename = _SafeConv<_Tp1>>
98 shared_ptr(_Tp1* __p, _Deleter __d)
99 : _Base_type(__p, __d)
100 { _M_enable_shared_from_this_with(__p); }
101
102 template<typename _Tp1, typename _Deleter, typename _Alloc,
103 typename = _SafeConv<_Tp1>>
104 shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a)
105 : _Base_type(__p, __d, __a)
106 { _M_enable_shared_from_this_with(__p); }
107
108 template<typename _Deleter>
109 shared_ptr(nullptr_t __p, _Deleter __d)
110 : _Base_type(__p, __d) { }
111
112 template<typename _Deleter, typename _Alloc>
113 shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
114 : _Base_type(__p, __d, __a) { }
115
116 template<typename _Tp1>
117 shared_ptr(const shared_ptr<_Tp1>& __r, element_type* __p) noexcept
118 : _Base_type(__r, __p) { }
119
120 shared_ptr(const shared_ptr& __r) noexcept
121 : _Base_type(__r) { }
122
123 template<typename _Tp1, typename = _Compatible<_Tp1>>
124 shared_ptr(const shared_ptr<_Tp1>& __r) noexcept
125 : _Base_type(__r) { }
126
127 shared_ptr(shared_ptr&& __r) noexcept
128 : _Base_type(std::move(__r)) { }
129
130 template<typename _Tp1, typename = _Compatible<_Tp1>>
131 shared_ptr(shared_ptr<_Tp1>&& __r) noexcept
132 : _Base_type(std::move(__r)) { }
133
134 template<typename _Tp1, typename = _Compatible<_Tp1>>
135 explicit
136 shared_ptr(const weak_ptr<_Tp1>& __r)
137 : _Base_type(__r) { }
138
139 #if _GLIBCXX_USE_DEPRECATED
140 template<typename _Tp1, typename = _Compatible<_Tp1>>
141 shared_ptr(std::auto_ptr<_Tp1>&& __r)
142 : _Base_type(std::move(__r))
143 { _M_enable_shared_from_this_with(static_cast<_Tp1*>(this->get())); }
144 #endif
145
146 template<typename _Tp1, typename _Del,
147 typename = _UniqCompatible<_Tp1, _Del>>
148 shared_ptr(unique_ptr<_Tp1, _Del>&& __r)
149 : _Base_type(std::move(__r))
150 {
151 // XXX assume conversion from __r.get() to this->get() to __elem_t*
152 // is a round trip, which might not be true in all cases.
153 using __elem_t = typename unique_ptr<_Tp1, _Del>::element_type;
154 _M_enable_shared_from_this_with(static_cast<__elem_t*>(this->get()));
155 }
156
157 constexpr shared_ptr(nullptr_t __p)
158 : _Base_type(__p) { }
159
160 // C++14 §20.8.2.2
161 ~shared_ptr() = default;
162
163 // C++14 §20.8.2.3
164 shared_ptr& operator=(const shared_ptr&) noexcept = default;
165
166 template <typename _Tp1>
167 _Compatible<_Tp1, shared_ptr&>
168 operator=(const shared_ptr<_Tp1>& __r) noexcept
169 {
170 _Base_type::operator=(__r);
171 return *this;
172 }
173
174 shared_ptr&
175 operator=(shared_ptr&& __r) noexcept
176 {
177 _Base_type::operator=(std::move(__r));
178 return *this;
179 }
180
181 template <typename _Tp1>
182 _Compatible<_Tp1, shared_ptr&>
183 operator=(shared_ptr<_Tp1>&& __r) noexcept
184 {
185 _Base_type::operator=(std::move(__r));
186 return *this;
187 }
188
189 #if _GLIBCXX_USE_DEPRECATED
190 template<typename _Tp1>
191 _Compatible<_Tp1, shared_ptr&>
192 operator=(std::auto_ptr<_Tp1>&& __r)
193 {
194 __shared_ptr<_Tp>::operator=(std::move(__r));
195 return *this;
196 }
197 #endif
198
199 template <typename _Tp1, typename _Del>
200 _UniqCompatible<_Tp1, _Del, shared_ptr&>
201 operator=(unique_ptr<_Tp1, _Del>&& __r)
202 {
203 _Base_type::operator=(std::move(__r));
204 return *this;
205 }
206
207 // C++14 §20.8.2.2.4
208 // swap & reset
209 // 8.2.1.2 shared_ptr observers
210 // in __shared_ptr
211
212 private:
213 template<typename _Alloc, typename... _Args>
214 shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
215 _Args&&... __args)
216 : _Base_type(__tag, __a, std::forward<_Args>(__args)...)
217 { _M_enable_shared_from_this_with(this->get()); }
218
219 template<typename _Tp1, typename _Alloc, typename... _Args>
220 friend shared_ptr<_Tp1>
221 allocate_shared(const _Alloc& __a, _Args&&... __args);
222
223 shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
224 : _Base_type(__r, std::nothrow) { }
225
226 friend class weak_ptr<_Tp>;
227
228 template<typename _Yp>
229 using __esft_base_t =
230 decltype(__expt_enable_shared_from_this_base(std::declval<_Yp*>()));
231
232 // Detect an accessible and unambiguous enable_shared_from_this base.
233 template<typename _Yp, typename = void>
234 struct __has_esft_base
235 : false_type { };
236
237 template<typename _Yp>
238 struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
239 : __bool_constant<!is_array_v<_Tp>> { }; // ignore base for arrays
240
241 template<typename _Yp>
242 typename enable_if<__has_esft_base<_Yp>::value>::type
243 _M_enable_shared_from_this_with(const _Yp* __p) noexcept
244 {
245 if (auto __base = __expt_enable_shared_from_this_base(__p))
246 {
247 __base->_M_weak_this
248 = shared_ptr<_Yp>(*this, const_cast<_Yp*>(__p));
249 }
250 }
251
252 template<typename _Yp>
253 typename enable_if<!__has_esft_base<_Yp>::value>::type
254 _M_enable_shared_from_this_with(const _Yp*) noexcept
255 { }
256 };
257
258 // C++14 §20.8.2.2.7 //DOING
259 template<typename _Tp1, typename _Tp2>
260 bool operator==(const shared_ptr<_Tp1>& __a,
261 const shared_ptr<_Tp2>& __b) noexcept
262 { return __a.get() == __b.get(); }
263
264 template<typename _Tp>
265 inline bool
266 operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
267 { return !__a; }
268
269 template<typename _Tp>
270 inline bool
271 operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
272 { return !__a; }
273
274 template<typename _Tp1, typename _Tp2>
275 inline bool
276 operator!=(const shared_ptr<_Tp1>& __a,
277 const shared_ptr<_Tp2>& __b) noexcept
278 { return __a.get() != __b.get(); }
279
280 template<typename _Tp>
281 inline bool
282 operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
283 { return (bool)__a; }
284
285 template<typename _Tp>
286 inline bool
287 operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
288 { return (bool)__a; }
289
290 template<typename _Tp1, typename _Tp2>
291 inline bool
292 operator<(const shared_ptr<_Tp1>& __a,
293 const shared_ptr<_Tp2>& __b) noexcept
294 {
295 using __elem_t1 = typename shared_ptr<_Tp1>::element_type;
296 using __elem_t2 = typename shared_ptr<_Tp2>::element_type;
297 using _CT = common_type_t<__elem_t1*, __elem_t2*>;
298 return std::less<_CT>()(__a.get(), __b.get());
299 }
300
301 template<typename _Tp>
302 inline bool
303 operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
304 {
305 using __elem_t = typename shared_ptr<_Tp>::element_type;
306 return std::less<__elem_t*>()(__a.get(), nullptr);
307 }
308
309 template<typename _Tp>
310 inline bool
311 operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
312 {
313 using __elem_t = typename shared_ptr<_Tp>::element_type;
314 return std::less<__elem_t*>()(nullptr, __a.get());
315 }
316
317 template<typename _Tp1, typename _Tp2>
318 inline bool
319 operator<=(const shared_ptr<_Tp1>& __a,
320 const shared_ptr<_Tp2>& __b) noexcept
321 { return !(__b < __a); }
322
323 template<typename _Tp>
324 inline bool
325 operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
326 { return !(nullptr < __a); }
327
328 template<typename _Tp>
329 inline bool
330 operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
331 { return !(__a < nullptr); }
332
333 template<typename _Tp1, typename _Tp2>
334 inline bool
335 operator>(const shared_ptr<_Tp1>& __a,
336 const shared_ptr<_Tp2>& __b) noexcept
337 { return (__b < __a); }
338
339 template<typename _Tp>
340 inline bool
341 operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
342 {
343 using __elem_t = typename shared_ptr<_Tp>::element_type;
344 return std::less<__elem_t*>()(nullptr, __a.get());
345 }
346
347 template<typename _Tp>
348 inline bool
349 operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
350 {
351 using __elem_t = typename shared_ptr<_Tp>::element_type;
352 return std::less<__elem_t*>()(__a.get(), nullptr);
353 }
354
355 template<typename _Tp1, typename _Tp2>
356 inline bool
357 operator>=(const shared_ptr<_Tp1>& __a,
358 const shared_ptr<_Tp2>& __b) noexcept
359 { return !(__a < __b); }
360
361 template<typename _Tp>
362 inline bool
363 operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
364 { return !(__a < nullptr); }
365
366 template<typename _Tp>
367 inline bool
368 operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
369 { return !(nullptr < __a); }
370
371 // C++14 §20.8.2.2.8
372 template<typename _Tp>
373 inline void
374 swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
375 { __a.swap(__b); }
376
377 // 8.2.1.3, shared_ptr casts
378 template<typename _Tp, typename _Tp1>
379 inline shared_ptr<_Tp>
380 static_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
381 {
382 using __elem_t = typename shared_ptr<_Tp>::element_type;
383 return shared_ptr<_Tp>(__r, static_cast<__elem_t*>(__r.get()));
384 }
385
386 template<typename _Tp, typename _Tp1>
387 inline shared_ptr<_Tp>
388 dynamic_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
389 {
390 using __elem_t = typename shared_ptr<_Tp>::element_type;
391 if (_Tp* __p = dynamic_cast<__elem_t*>(__r.get()))
392 return shared_ptr<_Tp>(__r, __p);
393 return shared_ptr<_Tp>();
394 }
395
396 template<typename _Tp, typename _Tp1>
397 inline shared_ptr<_Tp>
398 const_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
399 {
400 using __elem_t = typename shared_ptr<_Tp>::element_type;
401 return shared_ptr<_Tp>(__r, const_cast<__elem_t*>(__r.get()));
402 }
403
404 template<typename _Tp, typename _Tp1>
405 inline shared_ptr<_Tp>
406 reinterpret_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
407 {
408 using __elem_t = typename shared_ptr<_Tp>::element_type;
409 return shared_ptr<_Tp>(__r, reinterpret_cast<__elem_t*>(__r.get()));
410 }
411
412 // C++14 §20.8.2.3
413 template<typename _Tp>
414 class weak_ptr : public __weak_ptr<_Tp>
415 {
416 template<typename _Tp1, typename _Res = void>
417 using _Compatible = enable_if_t<__sp_compatible_v<_Tp1, _Tp>, _Res>;
418
419 using _Base_type = __weak_ptr<_Tp>;
420
421 public:
422 constexpr weak_ptr() noexcept = default;
423
424 template<typename _Tp1, typename = _Compatible<_Tp1>>
425 weak_ptr(const shared_ptr<_Tp1>& __r) noexcept
426 : _Base_type(__r) { }
427
428 weak_ptr(const weak_ptr&) noexcept = default;
429
430 template<typename _Tp1, typename = _Compatible<_Tp1>>
431 weak_ptr(const weak_ptr<_Tp1>& __r) noexcept
432 : _Base_type(__r) { }
433
434 weak_ptr(weak_ptr&&) noexcept = default;
435
436 template<typename _Tp1, typename = _Compatible<_Tp1>>
437 weak_ptr(weak_ptr<_Tp1>&& __r) noexcept
438 : _Base_type(std::move(__r)) { }
439
440 weak_ptr&
441 operator=(const weak_ptr& __r) noexcept = default;
442
443 template<typename _Tp1>
444 _Compatible<_Tp1, weak_ptr&>
445 operator=(const weak_ptr<_Tp1>& __r) noexcept
446 {
447 this->_Base_type::operator=(__r);
448 return *this;
449 }
450
451 template<typename _Tp1>
452 _Compatible<_Tp1, weak_ptr&>
453 operator=(const shared_ptr<_Tp1>& __r) noexcept
454 {
455 this->_Base_type::operator=(__r);
456 return *this;
457 }
458
459 weak_ptr&
460 operator=(weak_ptr&& __r) noexcept = default;
461
462 template<typename _Tp1>
463 _Compatible<_Tp1, weak_ptr&>
464 operator=(weak_ptr<_Tp1>&& __r) noexcept
465 {
466 this->_Base_type::operator=(std::move(__r));
467 return *this;
468 }
469
470 shared_ptr<_Tp>
471 lock() const noexcept
472 { return shared_ptr<_Tp>(*this, std::nothrow); }
473
474 friend class enable_shared_from_this<_Tp>;
475 };
476
477 // C++14 §20.8.2.3.6
478 template<typename _Tp>
479 inline void
480 swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
481 { __a.swap(__b); }
482
483 /// C++14 §20.8.2.2.10
484 template<typename _Del, typename _Tp>
485 inline _Del*
486 get_deleter(const shared_ptr<_Tp>& __p) noexcept
487 { return std::get_deleter<_Del>(__p); }
488
489 // C++14 §20.8.2.2.11
490 template<typename _Ch, typename _Tr, typename _Tp>
491 inline std::basic_ostream<_Ch, _Tr>&
492 operator<<(std::basic_ostream<_Ch, _Tr>& __os, const shared_ptr<_Tp>& __p)
493 {
494 __os << __p.get();
495 return __os;
496 }
497
498 // C++14 §20.8.2.4
499 template<typename _Tp = void> class owner_less;
500
501 /// Partial specialization of owner_less for shared_ptr.
502 template<typename _Tp>
503 struct owner_less<shared_ptr<_Tp>>
504 : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
505 { };
506
507 /// Partial specialization of owner_less for weak_ptr.
508 template<typename _Tp>
509 struct owner_less<weak_ptr<_Tp>>
510 : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
511 { };
512
513 template<>
514 class owner_less<void>
515 {
516 template<typename _Tp, typename _Up>
517 bool
518 operator()(shared_ptr<_Tp> const& __lhs,
519 shared_ptr<_Up> const& __rhs) const
520 { return __lhs.owner_before(__rhs); }
521
522 template<typename _Tp, typename _Up>
523 bool
524 operator()(shared_ptr<_Tp> const& __lhs,
525 weak_ptr<_Up> const& __rhs) const
526 { return __lhs.owner_before(__rhs); }
527
528 template<typename _Tp, typename _Up>
529 bool
530 operator()(weak_ptr<_Tp> const& __lhs,
531 shared_ptr<_Up> const& __rhs) const
532 { return __lhs.owner_before(__rhs); }
533
534 template<typename _Tp, typename _Up>
535 bool
536 operator()(weak_ptr<_Tp> const& __lhs,
537 weak_ptr<_Up> const& __rhs) const
538 { return __lhs.owner_before(__rhs); }
539
540 typedef void is_transparent;
541 };
542
543 // C++14 §20.8.2.6
544 template<typename _Tp>
545 inline bool
546 atomic_is_lock_free(const shared_ptr<_Tp>* __p)
547 { return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); }
548
549 template<typename _Tp>
550 shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p)
551 { return std::atomic_load<_Tp>(__p); }
552
553 template<typename _Tp>
554 shared_ptr<_Tp>
555 atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order __mo)
556 { return std::atomic_load_explicit<_Tp>(__p, __mo); }
557
558 template<typename _Tp>
559 void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
560 { return std::atomic_store<_Tp>(__p, __r); }
561
562 template<typename _Tp>
563 shared_ptr<_Tp>
564 atomic_store_explicit(const shared_ptr<_Tp>* __p,
565 shared_ptr<_Tp> __r,
566 memory_order __mo)
567 { return std::atomic_store_explicit<_Tp>(__p, __r, __mo); }
568
569 template<typename _Tp>
570 void atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
571 { return std::atomic_exchange<_Tp>(__p, __r); }
572
573 template<typename _Tp>
574 shared_ptr<_Tp>
575 atomic_exchange_explicit(const shared_ptr<_Tp>* __p,
576 shared_ptr<_Tp> __r,
577 memory_order __mo)
578 { return std::atomic_exchange_explicit<_Tp>(__p, __r, __mo); }
579
580 template<typename _Tp>
581 bool atomic_compare_exchange_weak(shared_ptr<_Tp>* __p,
582 shared_ptr<_Tp>* __v,
583 shared_ptr<_Tp> __w)
584 { return std::atomic_compare_exchange_weak<_Tp>(__p, __v, __w); }
585
586 template<typename _Tp>
587 bool atomic_compare_exchange_strong(shared_ptr<_Tp>* __p,
588 shared_ptr<_Tp>* __v,
589 shared_ptr<_Tp> __w)
590 { return std::atomic_compare_exchange_strong<_Tp>(__p, __v, __w); }
591
592 template<typename _Tp>
593 bool atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p,
594 shared_ptr<_Tp>* __v,
595 shared_ptr<_Tp> __w,
596 memory_order __success,
597 memory_order __failure)
598 { return std::atomic_compare_exchange_weak_explicit<_Tp>(__p, __v, __w,
599 __success,
600 __failure); }
601
602 template<typename _Tp>
603 bool atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p,
604 shared_ptr<_Tp>* __v,
605 shared_ptr<_Tp> __w,
606 memory_order __success,
607 memory_order __failure)
608 { return std::atomic_compare_exchange_strong_explicit<_Tp>(__p, __v, __w,
609 __success,
610 __failure); }
611
612 //enable_shared_from_this
613 template<typename _Tp>
614 class enable_shared_from_this
615 {
616 protected:
617 constexpr enable_shared_from_this() noexcept { }
618
619 enable_shared_from_this(const enable_shared_from_this&) noexcept { }
620
621 enable_shared_from_this&
622 operator=(const enable_shared_from_this&) noexcept
623 { return *this; }
624
625 ~enable_shared_from_this() { }
626
627 public:
628 shared_ptr<_Tp>
629 shared_from_this()
630 { return shared_ptr<_Tp>(this->_M_weak_this); }
631
632 shared_ptr<const _Tp>
633 shared_from_this() const
634 { return shared_ptr<const _Tp>(this->_M_weak_this); }
635
636 weak_ptr<_Tp>
637 weak_from_this() noexcept
638 { return _M_weak_this; }
639
640 weak_ptr<const _Tp>
641 weak_from_this() const noexcept
642 { return _M_weak_this; }
643
644 private:
645 template<typename _Tp1>
646 void
647 _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
648 { _M_weak_this._M_assign(__p, __n); }
649
650 // Found by ADL when this is an associated class.
651 friend const enable_shared_from_this*
652 __expt_enable_shared_from_this_base(const enable_shared_from_this* __p)
653 { return __p; }
654
655 template<typename>
656 friend class shared_ptr;
657
658 mutable weak_ptr<_Tp> _M_weak_this;
659 };
660 } // namespace fundamentals_v2
661 } // namespace experimental
662
663 /// std::hash specialization for shared_ptr.
664 template<typename _Tp>
665 struct hash<experimental::shared_ptr<_Tp>>
666 : public __hash_base<size_t, experimental::shared_ptr<_Tp>>
667 {
668 size_t
669 operator()(const experimental::shared_ptr<_Tp>& __s) const noexcept
670 { return std::hash<_Tp*>()(__s.get()); }
671 };
672
673 _GLIBCXX_END_NAMESPACE_VERSION
674 } // namespace std
675
676 #endif // __cplusplus <= 201103L
677
678 #endif // _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H
679