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1 // Experimental shared_ptr with array support -*- C++ -*- 2 3 // Copyright (C) 2015-2025 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 #ifdef _GLIBCXX_SYSHDR 34 #pragma GCC system_header 35 #endif 36 37 #if __cplusplus >= 201402L 38 39 #include <memory> 40 #include <experimental/type_traits> 41 42 namespace std _GLIBCXX_VISIBILITY(default) 43 { 44 _GLIBCXX_BEGIN_NAMESPACE_VERSION 45 46 namespace experimental 47 { 48 inline namespace fundamentals_v2 49 { 50 // 8.2.1 51 52 template<typename _Tp> class shared_ptr; 53 template<typename _Tp> class weak_ptr; 54 template<typename _Tp> class enable_shared_from_this; 55 56 template<typename _Yp, typename _Tp> 57 constexpr bool __sp_compatible_v 58 = std::__sp_compatible_with<_Yp*, _Tp*>::value; 59 60 template<typename _Tp, typename _Yp> 61 constexpr bool __sp_is_constructible_v 62 = std::__sp_is_constructible<_Tp, _Yp>::value; 63 64 template<typename _Tp> 65 class shared_ptr : public __shared_ptr<_Tp> 66 { 67 using _Base_type = __shared_ptr<_Tp>; 68 69 public: 70 using element_type = typename _Base_type::element_type; 71 72 private: 73 // Constraint for construction from a pointer of type _Yp*: 74 template<typename _Yp> 75 using _SafeConv = enable_if_t<__sp_is_constructible_v<_Tp, _Yp>>; 76 77 template<typename _Tp1, typename _Res = void> 78 using _Compatible 79 = enable_if_t<__sp_compatible_v<_Tp1, _Tp>, _Res>; 80 81 template<typename _Tp1, typename _Del, 82 typename _Ptr = typename unique_ptr<_Tp1, _Del>::pointer, 83 typename _Res = void> 84 using _UniqCompatible = enable_if_t< 85 __sp_compatible_v<_Tp1, _Tp> 86 && experimental::is_convertible_v<_Ptr, element_type*>, 87 _Res>; 88 89 public: 90 91 // 8.2.1.1, shared_ptr constructors 92 constexpr shared_ptr() noexcept = default; 93 94 template<typename _Tp1, typename = _SafeConv<_Tp1>> 95 explicit 96 shared_ptr(_Tp1* __p) : _Base_type(__p) 97 { _M_enable_shared_from_this_with(__p); } 98 99 template<typename _Tp1, typename _Deleter, typename = _SafeConv<_Tp1>> 100 shared_ptr(_Tp1* __p, _Deleter __d) 101 : _Base_type(__p, __d) 102 { _M_enable_shared_from_this_with(__p); } 103 104 template<typename _Tp1, typename _Deleter, typename _Alloc, 105 typename = _SafeConv<_Tp1>> 106 shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a) 107 : _Base_type(__p, __d, __a) 108 { _M_enable_shared_from_this_with(__p); } 109 110 template<typename _Deleter> 111 shared_ptr(nullptr_t __p, _Deleter __d) 112 : _Base_type(__p, __d) { } 113 114 template<typename _Deleter, typename _Alloc> 115 shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a) 116 : _Base_type(__p, __d, __a) { } 117 118 template<typename _Tp1> 119 shared_ptr(const shared_ptr<_Tp1>& __r, element_type* __p) noexcept 120 : _Base_type(__r, __p) { } 121 122 shared_ptr(const shared_ptr& __r) noexcept 123 : _Base_type(__r) { } 124 125 template<typename _Tp1, typename = _Compatible<_Tp1>> 126 shared_ptr(const shared_ptr<_Tp1>& __r) noexcept 127 : _Base_type(__r) { } 128 129 shared_ptr(shared_ptr&& __r) noexcept 130 : _Base_type(std::move(__r)) { } 131 132 template<typename _Tp1, typename = _Compatible<_Tp1>> 133 shared_ptr(shared_ptr<_Tp1>&& __r) noexcept 134 : _Base_type(std::move(__r)) { } 135 136 template<typename _Tp1, typename = _Compatible<_Tp1>> 137 explicit 138 shared_ptr(const weak_ptr<_Tp1>& __r) 139 : _Base_type(__r) { } 140 141 #if _GLIBCXX_USE_DEPRECATED 142 #pragma GCC diagnostic push 143 #pragma GCC diagnostic ignored "-Wdeprecated-declarations" 144 template<typename _Tp1, typename = _Compatible<_Tp1>> 145 shared_ptr(std::auto_ptr<_Tp1>&& __r) 146 : _Base_type(std::move(__r)) 147 { _M_enable_shared_from_this_with(static_cast<_Tp1*>(this->get())); } 148 #pragma GCC diagnostic pop 149 #endif 150 151 template<typename _Tp1, typename _Del, 152 typename = _UniqCompatible<_Tp1, _Del>> 153 shared_ptr(unique_ptr<_Tp1, _Del>&& __r) 154 : _Base_type(std::move(__r)) 155 { 156 // XXX assume conversion from __r.get() to this->get() to __elem_t* 157 // is a round trip, which might not be true in all cases. 158 using __elem_t = typename unique_ptr<_Tp1, _Del>::element_type; 159 _M_enable_shared_from_this_with(static_cast<__elem_t*>(this->get())); 160 } 161 162 constexpr shared_ptr(nullptr_t __p) 163 : _Base_type(__p) { } 164 165 // C++14 20.8.2.2 166 ~shared_ptr() = default; 167 168 // C++14 20.8.2.3 169 shared_ptr& operator=(const shared_ptr&) noexcept = default; 170 171 template <typename _Tp1> 172 _Compatible<_Tp1, shared_ptr&> 173 operator=(const shared_ptr<_Tp1>& __r) noexcept 174 { 175 _Base_type::operator=(__r); 176 return *this; 177 } 178 179 shared_ptr& 180 operator=(shared_ptr&& __r) noexcept 181 { 182 _Base_type::operator=(std::move(__r)); 183 return *this; 184 } 185 186 template <typename _Tp1> 187 _Compatible<_Tp1, shared_ptr&> 188 operator=(shared_ptr<_Tp1>&& __r) noexcept 189 { 190 _Base_type::operator=(std::move(__r)); 191 return *this; 192 } 193 194 #if _GLIBCXX_USE_DEPRECATED 195 #pragma GCC diagnostic push 196 #pragma GCC diagnostic ignored "-Wdeprecated-declarations" 197 template<typename _Tp1> 198 _Compatible<_Tp1, shared_ptr&> 199 operator=(std::auto_ptr<_Tp1>&& __r) 200 { 201 __shared_ptr<_Tp>::operator=(std::move(__r)); 202 return *this; 203 } 204 #pragma GCC diagnostic pop 205 #endif 206 207 template <typename _Tp1, typename _Del> 208 _UniqCompatible<_Tp1, _Del, shared_ptr&> 209 operator=(unique_ptr<_Tp1, _Del>&& __r) 210 { 211 _Base_type::operator=(std::move(__r)); 212 return *this; 213 } 214 215 // C++14 20.8.2.2.4 216 // swap & reset 217 // 8.2.1.2 shared_ptr observers 218 // in __shared_ptr 219 220 private: 221 template<typename _Alloc, typename... _Args> 222 shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a, 223 _Args&&... __args) 224 : _Base_type(__tag, __a, std::forward<_Args>(__args)...) 225 { _M_enable_shared_from_this_with(this->get()); } 226 227 template<typename _Tp1, typename _Alloc, typename... _Args> 228 friend shared_ptr<_Tp1> 229 allocate_shared(const _Alloc& __a, _Args&&... __args); 230 231 shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t) 232 : _Base_type(__r, std::nothrow) { } 233 234 friend class weak_ptr<_Tp>; 235 236 template<typename _Yp> 237 using __esft_base_t = 238 decltype(__expt_enable_shared_from_this_base(std::declval<_Yp*>())); 239 240 // Detect an accessible and unambiguous enable_shared_from_this base. 241 template<typename _Yp, typename = void> 242 struct __has_esft_base 243 : false_type { }; 244 245 template<typename _Yp> 246 struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>> 247 : __bool_constant<!is_array_v<_Tp>> { }; // ignore base for arrays 248 249 template<typename _Yp> 250 typename enable_if<__has_esft_base<_Yp>::value>::type 251 _M_enable_shared_from_this_with(const _Yp* __p) noexcept 252 { 253 if (auto __base = __expt_enable_shared_from_this_base(__p)) 254 { 255 __base->_M_weak_this 256 = shared_ptr<_Yp>(*this, const_cast<_Yp*>(__p)); 257 } 258 } 259 260 template<typename _Yp> 261 typename enable_if<!__has_esft_base<_Yp>::value>::type 262 _M_enable_shared_from_this_with(const _Yp*) noexcept 263 { } 264 }; 265 266 // C++14 20.8.2.2.7 267 template<typename _Tp1, typename _Tp2> 268 bool operator==(const shared_ptr<_Tp1>& __a, 269 const shared_ptr<_Tp2>& __b) noexcept 270 { return __a.get() == __b.get(); } 271 272 template<typename _Tp> 273 inline bool 274 operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 275 { return !__a; } 276 277 template<typename _Tp> 278 inline bool 279 operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 280 { return !__a; } 281 282 template<typename _Tp1, typename _Tp2> 283 inline bool 284 operator!=(const shared_ptr<_Tp1>& __a, 285 const shared_ptr<_Tp2>& __b) noexcept 286 { return __a.get() != __b.get(); } 287 288 template<typename _Tp> 289 inline bool 290 operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 291 { return (bool)__a; } 292 293 template<typename _Tp> 294 inline bool 295 operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 296 { return (bool)__a; } 297 298 template<typename _Tp1, typename _Tp2> 299 inline bool 300 operator<(const shared_ptr<_Tp1>& __a, 301 const shared_ptr<_Tp2>& __b) noexcept 302 { 303 using __elem_t1 = typename shared_ptr<_Tp1>::element_type; 304 using __elem_t2 = typename shared_ptr<_Tp2>::element_type; 305 using _CT = common_type_t<__elem_t1*, __elem_t2*>; 306 return std::less<_CT>()(__a.get(), __b.get()); 307 } 308 309 template<typename _Tp> 310 inline bool 311 operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 312 { 313 using __elem_t = typename shared_ptr<_Tp>::element_type; 314 return std::less<__elem_t*>()(__a.get(), nullptr); 315 } 316 317 template<typename _Tp> 318 inline bool 319 operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 320 { 321 using __elem_t = typename shared_ptr<_Tp>::element_type; 322 return std::less<__elem_t*>()(nullptr, __a.get()); 323 } 324 325 template<typename _Tp1, typename _Tp2> 326 inline bool 327 operator<=(const shared_ptr<_Tp1>& __a, 328 const shared_ptr<_Tp2>& __b) noexcept 329 { return !(__b < __a); } 330 331 template<typename _Tp> 332 inline bool 333 operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 334 { return !(nullptr < __a); } 335 336 template<typename _Tp> 337 inline bool 338 operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 339 { return !(__a < nullptr); } 340 341 template<typename _Tp1, typename _Tp2> 342 inline bool 343 operator>(const shared_ptr<_Tp1>& __a, 344 const shared_ptr<_Tp2>& __b) noexcept 345 { return (__b < __a); } 346 347 template<typename _Tp> 348 inline bool 349 operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 350 { 351 using __elem_t = typename shared_ptr<_Tp>::element_type; 352 return std::less<__elem_t*>()(nullptr, __a.get()); 353 } 354 355 template<typename _Tp> 356 inline bool 357 operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 358 { 359 using __elem_t = typename shared_ptr<_Tp>::element_type; 360 return std::less<__elem_t*>()(__a.get(), nullptr); 361 } 362 363 template<typename _Tp1, typename _Tp2> 364 inline bool 365 operator>=(const shared_ptr<_Tp1>& __a, 366 const shared_ptr<_Tp2>& __b) noexcept 367 { return !(__a < __b); } 368 369 template<typename _Tp> 370 inline bool 371 operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 372 { return !(__a < nullptr); } 373 374 template<typename _Tp> 375 inline bool 376 operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 377 { return !(nullptr < __a); } 378 379 // C++14 20.8.2.2.8 380 template<typename _Tp> 381 inline void 382 swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept 383 { __a.swap(__b); } 384 385 // 8.2.1.3, shared_ptr casts 386 template<typename _Tp, typename _Tp1> 387 inline shared_ptr<_Tp> 388 static_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept 389 { 390 using __elem_t = typename shared_ptr<_Tp>::element_type; 391 return shared_ptr<_Tp>(__r, static_cast<__elem_t*>(__r.get())); 392 } 393 394 template<typename _Tp, typename _Tp1> 395 inline shared_ptr<_Tp> 396 dynamic_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept 397 { 398 using __elem_t = typename shared_ptr<_Tp>::element_type; 399 if (_Tp* __p = dynamic_cast<__elem_t*>(__r.get())) 400 return shared_ptr<_Tp>(__r, __p); 401 return shared_ptr<_Tp>(); 402 } 403 404 template<typename _Tp, typename _Tp1> 405 inline shared_ptr<_Tp> 406 const_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, const_cast<__elem_t*>(__r.get())); 410 } 411 412 template<typename _Tp, typename _Tp1> 413 inline shared_ptr<_Tp> 414 reinterpret_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept 415 { 416 using __elem_t = typename shared_ptr<_Tp>::element_type; 417 return shared_ptr<_Tp>(__r, reinterpret_cast<__elem_t*>(__r.get())); 418 } 419 420 // C++14 20.8.2.3 421 template<typename _Tp> 422 class weak_ptr : public __weak_ptr<_Tp> 423 { 424 template<typename _Tp1, typename _Res = void> 425 using _Compatible = enable_if_t<__sp_compatible_v<_Tp1, _Tp>, _Res>; 426 427 using _Base_type = __weak_ptr<_Tp>; 428 429 public: 430 constexpr weak_ptr() noexcept = default; 431 432 template<typename _Tp1, typename = _Compatible<_Tp1>> 433 weak_ptr(const shared_ptr<_Tp1>& __r) noexcept 434 : _Base_type(__r) { } 435 436 weak_ptr(const weak_ptr&) noexcept = default; 437 438 template<typename _Tp1, typename = _Compatible<_Tp1>> 439 weak_ptr(const weak_ptr<_Tp1>& __r) noexcept 440 : _Base_type(__r) { } 441 442 weak_ptr(weak_ptr&&) noexcept = default; 443 444 template<typename _Tp1, typename = _Compatible<_Tp1>> 445 weak_ptr(weak_ptr<_Tp1>&& __r) noexcept 446 : _Base_type(std::move(__r)) { } 447 448 weak_ptr& 449 operator=(const weak_ptr& __r) noexcept = default; 450 451 template<typename _Tp1> 452 _Compatible<_Tp1, weak_ptr&> 453 operator=(const weak_ptr<_Tp1>& __r) noexcept 454 { 455 this->_Base_type::operator=(__r); 456 return *this; 457 } 458 459 template<typename _Tp1> 460 _Compatible<_Tp1, weak_ptr&> 461 operator=(const shared_ptr<_Tp1>& __r) noexcept 462 { 463 this->_Base_type::operator=(__r); 464 return *this; 465 } 466 467 weak_ptr& 468 operator=(weak_ptr&& __r) noexcept = default; 469 470 template<typename _Tp1> 471 _Compatible<_Tp1, weak_ptr&> 472 operator=(weak_ptr<_Tp1>&& __r) noexcept 473 { 474 this->_Base_type::operator=(std::move(__r)); 475 return *this; 476 } 477 478 shared_ptr<_Tp> 479 lock() const noexcept 480 { return shared_ptr<_Tp>(*this, std::nothrow); } 481 482 friend class enable_shared_from_this<_Tp>; 483 }; 484 485 // C++14 20.8.2.3.6 486 template<typename _Tp> 487 inline void 488 swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept 489 { __a.swap(__b); } 490 491 /// C++14 20.8.2.2.10 492 template<typename _Del, typename _Tp> 493 inline _Del* 494 get_deleter(const shared_ptr<_Tp>& __p) noexcept 495 { return std::get_deleter<_Del>(__p); } 496 497 // C++14 20.8.2.2.11 498 template<typename _Ch, typename _Tr, typename _Tp> 499 inline std::basic_ostream<_Ch, _Tr>& 500 operator<<(std::basic_ostream<_Ch, _Tr>& __os, const shared_ptr<_Tp>& __p) 501 { 502 __os << __p.get(); 503 return __os; 504 } 505 506 // C++14 20.8.2.4 507 template<typename _Tp = void> class owner_less; 508 509 /// Partial specialization of owner_less for shared_ptr. 510 template<typename _Tp> 511 struct owner_less<shared_ptr<_Tp>> 512 : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>> 513 { }; 514 515 /// Partial specialization of owner_less for weak_ptr. 516 template<typename _Tp> 517 struct owner_less<weak_ptr<_Tp>> 518 : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>> 519 { }; 520 521 template<> 522 class owner_less<void> 523 { 524 template<typename _Tp, typename _Up> 525 bool 526 operator()(shared_ptr<_Tp> const& __lhs, 527 shared_ptr<_Up> const& __rhs) const 528 { return __lhs.owner_before(__rhs); } 529 530 template<typename _Tp, typename _Up> 531 bool 532 operator()(shared_ptr<_Tp> const& __lhs, 533 weak_ptr<_Up> const& __rhs) const 534 { return __lhs.owner_before(__rhs); } 535 536 template<typename _Tp, typename _Up> 537 bool 538 operator()(weak_ptr<_Tp> const& __lhs, 539 shared_ptr<_Up> const& __rhs) const 540 { return __lhs.owner_before(__rhs); } 541 542 template<typename _Tp, typename _Up> 543 bool 544 operator()(weak_ptr<_Tp> const& __lhs, 545 weak_ptr<_Up> const& __rhs) const 546 { return __lhs.owner_before(__rhs); } 547 548 typedef void is_transparent; 549 }; 550 551 // C++14 20.8.2.6 552 template<typename _Tp> 553 inline bool 554 atomic_is_lock_free(const shared_ptr<_Tp>* __p) 555 { return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); } 556 557 template<typename _Tp> 558 shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p) 559 { return std::atomic_load<_Tp>(__p); } 560 561 template<typename _Tp> 562 shared_ptr<_Tp> 563 atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order __mo) 564 { return std::atomic_load_explicit<_Tp>(__p, __mo); } 565 566 template<typename _Tp> 567 void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) 568 { return std::atomic_store<_Tp>(__p, __r); } 569 570 template<typename _Tp> 571 shared_ptr<_Tp> 572 atomic_store_explicit(const shared_ptr<_Tp>* __p, 573 shared_ptr<_Tp> __r, 574 memory_order __mo) 575 { return std::atomic_store_explicit<_Tp>(__p, __r, __mo); } 576 577 template<typename _Tp> 578 void atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) 579 { return std::atomic_exchange<_Tp>(__p, __r); } 580 581 template<typename _Tp> 582 shared_ptr<_Tp> 583 atomic_exchange_explicit(const shared_ptr<_Tp>* __p, 584 shared_ptr<_Tp> __r, 585 memory_order __mo) 586 { return std::atomic_exchange_explicit<_Tp>(__p, __r, __mo); } 587 588 template<typename _Tp> 589 bool atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, 590 shared_ptr<_Tp>* __v, 591 shared_ptr<_Tp> __w) 592 { return std::atomic_compare_exchange_weak<_Tp>(__p, __v, __w); } 593 594 template<typename _Tp> 595 bool atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, 596 shared_ptr<_Tp>* __v, 597 shared_ptr<_Tp> __w) 598 { return std::atomic_compare_exchange_strong<_Tp>(__p, __v, __w); } 599 600 template<typename _Tp> 601 bool atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p, 602 shared_ptr<_Tp>* __v, 603 shared_ptr<_Tp> __w, 604 memory_order __success, 605 memory_order __failure) 606 { return std::atomic_compare_exchange_weak_explicit<_Tp>(__p, __v, __w, 607 __success, 608 __failure); } 609 610 template<typename _Tp> 611 bool atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p, 612 shared_ptr<_Tp>* __v, 613 shared_ptr<_Tp> __w, 614 memory_order __success, 615 memory_order __failure) 616 { return std::atomic_compare_exchange_strong_explicit<_Tp>(__p, __v, __w, 617 __success, 618 __failure); } 619 620 //enable_shared_from_this 621 template<typename _Tp> 622 class enable_shared_from_this 623 { 624 protected: 625 constexpr enable_shared_from_this() noexcept { } 626 627 enable_shared_from_this(const enable_shared_from_this&) noexcept { } 628 629 enable_shared_from_this& 630 operator=(const enable_shared_from_this&) noexcept 631 { return *this; } 632 633 ~enable_shared_from_this() { } 634 635 public: 636 shared_ptr<_Tp> 637 shared_from_this() 638 { return shared_ptr<_Tp>(this->_M_weak_this); } 639 640 shared_ptr<const _Tp> 641 shared_from_this() const 642 { return shared_ptr<const _Tp>(this->_M_weak_this); } 643 644 weak_ptr<_Tp> 645 weak_from_this() noexcept 646 { return _M_weak_this; } 647 648 weak_ptr<const _Tp> 649 weak_from_this() const noexcept 650 { return _M_weak_this; } 651 652 private: 653 template<typename _Tp1> 654 void 655 _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept 656 { _M_weak_this._M_assign(__p, __n); } 657 658 // Found by ADL when this is an associated class. 659 friend const enable_shared_from_this* 660 __expt_enable_shared_from_this_base(const enable_shared_from_this* __p) 661 { return __p; } 662 663 template<typename> 664 friend class shared_ptr; 665 666 mutable weak_ptr<_Tp> _M_weak_this; 667 }; 668 } // namespace fundamentals_v2 669 } // namespace experimental 670 671 /// std::hash specialization for shared_ptr. 672 template<typename _Tp> 673 struct hash<experimental::shared_ptr<_Tp>> 674 : public __hash_base<size_t, experimental::shared_ptr<_Tp>> 675 { 676 size_t 677 operator()(const experimental::shared_ptr<_Tp>& __s) const noexcept 678 { return std::hash<_Tp*>()(__s.get()); } 679 }; 680 681 _GLIBCXX_END_NAMESPACE_VERSION 682 } // namespace std 683 684 #endif // __cplusplus <= 201103L 685 686 #endif // _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H
