1 // shared_ptr and weak_ptr implementation details -*- C++ -*- 2 3 // Copyright (C) 2007-2015 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 // GCC Note: Based on files from version 1.32.0 of the Boost library. 26 27 // shared_count.hpp 28 // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd. 29 30 // shared_ptr.hpp 31 // Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes. 32 // Copyright (C) 2001, 2002, 2003 Peter Dimov 33 34 // weak_ptr.hpp 35 // Copyright (C) 2001, 2002, 2003 Peter Dimov 36 37 // enable_shared_from_this.hpp 38 // Copyright (C) 2002 Peter Dimov 39 40 // Distributed under the Boost Software License, Version 1.0. (See 41 // accompanying file LICENSE_1_0.txt or copy at 42 // http://www.boost.org/LICENSE_1_0.txt) 43 44 /** @file bits/shared_ptr_base.h 45 * This is an internal header file, included by other library headers. 46 * Do not attempt to use it directly. @headername{memory} 47 */ 48 49 #ifndef _SHARED_PTR_BASE_H 50 #define _SHARED_PTR_BASE_H 1 51 52 #include <bits/allocated_ptr.h> 53 #include <ext/aligned_buffer.h> 54 55 namespace std _GLIBCXX_VISIBILITY(default) 56 { 57 _GLIBCXX_BEGIN_NAMESPACE_VERSION 58 59 #if _GLIBCXX_USE_DEPRECATED 60 template<typename> class auto_ptr; 61 #endif 62 63 /** 64 * @brief Exception possibly thrown by @c shared_ptr. 65 * @ingroup exceptions 66 */ 67 class bad_weak_ptr : public std::exception 68 { 69 public: 70 virtual char const* 71 what() const noexcept; 72 73 virtual ~bad_weak_ptr() noexcept; 74 }; 75 76 // Substitute for bad_weak_ptr object in the case of -fno-exceptions. 77 inline void 78 __throw_bad_weak_ptr() 79 { _GLIBCXX_THROW_OR_ABORT(bad_weak_ptr()); } 80 81 using __gnu_cxx::_Lock_policy; 82 using __gnu_cxx::__default_lock_policy; 83 using __gnu_cxx::_S_single; 84 using __gnu_cxx::_S_mutex; 85 using __gnu_cxx::_S_atomic; 86 87 // Empty helper class except when the template argument is _S_mutex. 88 template<_Lock_policy _Lp> 89 class _Mutex_base 90 { 91 protected: 92 // The atomic policy uses fully-fenced builtins, single doesn't care. 93 enum { _S_need_barriers = 0 }; 94 }; 95 96 template<> 97 class _Mutex_base<_S_mutex> 98 : public __gnu_cxx::__mutex 99 { 100 protected: 101 // This policy is used when atomic builtins are not available. 102 // The replacement atomic operations might not have the necessary 103 // memory barriers. 104 enum { _S_need_barriers = 1 }; 105 }; 106 107 template<_Lock_policy _Lp = __default_lock_policy> 108 class _Sp_counted_base 109 : public _Mutex_base<_Lp> 110 { 111 public: 112 _Sp_counted_base() noexcept 113 : _M_use_count(1), _M_weak_count(1) { } 114 115 virtual 116 ~_Sp_counted_base() noexcept 117 { } 118 119 // Called when _M_use_count drops to zero, to release the resources 120 // managed by *this. 121 virtual void 122 _M_dispose() noexcept = 0; 123 124 // Called when _M_weak_count drops to zero. 125 virtual void 126 _M_destroy() noexcept 127 { delete this; } 128 129 virtual void* 130 _M_get_deleter(const std::type_info&) noexcept = 0; 131 132 void 133 _M_add_ref_copy() 134 { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); } 135 136 void 137 _M_add_ref_lock(); 138 139 bool 140 _M_add_ref_lock_nothrow(); 141 142 void 143 _M_release() noexcept 144 { 145 // Be race-detector-friendly. For more info see bits/c++config. 146 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count); 147 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1) 148 { 149 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count); 150 _M_dispose(); 151 // There must be a memory barrier between dispose() and destroy() 152 // to ensure that the effects of dispose() are observed in the 153 // thread that runs destroy(). 154 // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html 155 if (_Mutex_base<_Lp>::_S_need_barriers) 156 { 157 _GLIBCXX_READ_MEM_BARRIER; 158 _GLIBCXX_WRITE_MEM_BARRIER; 159 } 160 161 // Be race-detector-friendly. For more info see bits/c++config. 162 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count); 163 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, 164 -1) == 1) 165 { 166 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count); 167 _M_destroy(); 168 } 169 } 170 } 171 172 void 173 _M_weak_add_ref() noexcept 174 { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); } 175 176 void 177 _M_weak_release() noexcept 178 { 179 // Be race-detector-friendly. For more info see bits/c++config. 180 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count); 181 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1) 182 { 183 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count); 184 if (_Mutex_base<_Lp>::_S_need_barriers) 185 { 186 // See _M_release(), 187 // destroy() must observe results of dispose() 188 _GLIBCXX_READ_MEM_BARRIER; 189 _GLIBCXX_WRITE_MEM_BARRIER; 190 } 191 _M_destroy(); 192 } 193 } 194 195 long 196 _M_get_use_count() const noexcept 197 { 198 // No memory barrier is used here so there is no synchronization 199 // with other threads. 200 return __atomic_load_n(&_M_use_count, __ATOMIC_RELAXED); 201 } 202 203 private: 204 _Sp_counted_base(_Sp_counted_base const&) = delete; 205 _Sp_counted_base& operator=(_Sp_counted_base const&) = delete; 206 207 _Atomic_word _M_use_count; // #shared 208 _Atomic_word _M_weak_count; // #weak + (#shared != 0) 209 }; 210 211 template<> 212 inline void 213 _Sp_counted_base<_S_single>:: 214 _M_add_ref_lock() 215 { 216 if (_M_use_count == 0) 217 __throw_bad_weak_ptr(); 218 ++_M_use_count; 219 } 220 221 template<> 222 inline void 223 _Sp_counted_base<_S_mutex>:: 224 _M_add_ref_lock() 225 { 226 __gnu_cxx::__scoped_lock sentry(*this); 227 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0) 228 { 229 _M_use_count = 0; 230 __throw_bad_weak_ptr(); 231 } 232 } 233 234 template<> 235 inline void 236 _Sp_counted_base<_S_atomic>:: 237 _M_add_ref_lock() 238 { 239 // Perform lock-free add-if-not-zero operation. 240 _Atomic_word __count = _M_get_use_count(); 241 do 242 { 243 if (__count == 0) 244 __throw_bad_weak_ptr(); 245 // Replace the current counter value with the old value + 1, as 246 // long as it's not changed meanwhile. 247 } 248 while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1, 249 true, __ATOMIC_ACQ_REL, 250 __ATOMIC_RELAXED)); 251 } 252 253 template<> 254 inline bool 255 _Sp_counted_base<_S_single>:: 256 _M_add_ref_lock_nothrow() 257 { 258 if (_M_use_count == 0) 259 return false; 260 ++_M_use_count; 261 return true; 262 } 263 264 template<> 265 inline bool 266 _Sp_counted_base<_S_mutex>:: 267 _M_add_ref_lock_nothrow() 268 { 269 __gnu_cxx::__scoped_lock sentry(*this); 270 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0) 271 { 272 _M_use_count = 0; 273 return false; 274 } 275 return true; 276 } 277 278 template<> 279 inline bool 280 _Sp_counted_base<_S_atomic>:: 281 _M_add_ref_lock_nothrow() 282 { 283 // Perform lock-free add-if-not-zero operation. 284 _Atomic_word __count = _M_get_use_count(); 285 do 286 { 287 if (__count == 0) 288 return false; 289 // Replace the current counter value with the old value + 1, as 290 // long as it's not changed meanwhile. 291 } 292 while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1, 293 true, __ATOMIC_ACQ_REL, 294 __ATOMIC_RELAXED)); 295 return true; 296 } 297 298 template<> 299 inline void 300 _Sp_counted_base<_S_single>::_M_add_ref_copy() 301 { ++_M_use_count; } 302 303 template<> 304 inline void 305 _Sp_counted_base<_S_single>::_M_release() noexcept 306 { 307 if (--_M_use_count == 0) 308 { 309 _M_dispose(); 310 if (--_M_weak_count == 0) 311 _M_destroy(); 312 } 313 } 314 315 template<> 316 inline void 317 _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept 318 { ++_M_weak_count; } 319 320 template<> 321 inline void 322 _Sp_counted_base<_S_single>::_M_weak_release() noexcept 323 { 324 if (--_M_weak_count == 0) 325 _M_destroy(); 326 } 327 328 template<> 329 inline long 330 _Sp_counted_base<_S_single>::_M_get_use_count() const noexcept 331 { return _M_use_count; } 332 333 334 // Forward declarations. 335 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy> 336 class __shared_ptr; 337 338 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy> 339 class __weak_ptr; 340 341 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy> 342 class __enable_shared_from_this; 343 344 template<typename _Tp> 345 class shared_ptr; 346 347 template<typename _Tp> 348 class weak_ptr; 349 350 template<typename _Tp> 351 struct owner_less; 352 353 template<typename _Tp> 354 class enable_shared_from_this; 355 356 template<_Lock_policy _Lp = __default_lock_policy> 357 class __weak_count; 358 359 template<_Lock_policy _Lp = __default_lock_policy> 360 class __shared_count; 361 362 363 // Counted ptr with no deleter or allocator support 364 template<typename _Ptr, _Lock_policy _Lp> 365 class _Sp_counted_ptr final : public _Sp_counted_base<_Lp> 366 { 367 public: 368 explicit 369 _Sp_counted_ptr(_Ptr __p) noexcept 370 : _M_ptr(__p) { } 371 372 virtual void 373 _M_dispose() noexcept 374 { delete _M_ptr; } 375 376 virtual void 377 _M_destroy() noexcept 378 { delete this; } 379 380 virtual void* 381 _M_get_deleter(const std::type_info&) noexcept 382 { return nullptr; } 383 384 _Sp_counted_ptr(const _Sp_counted_ptr&) = delete; 385 _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete; 386 387 private: 388 _Ptr _M_ptr; 389 }; 390 391 template<> 392 inline void 393 _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() noexcept { } 394 395 template<> 396 inline void 397 _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() noexcept { } 398 399 template<> 400 inline void 401 _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { } 402 403 template<int _Nm, typename _Tp, 404 bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)> 405 struct _Sp_ebo_helper; 406 407 /// Specialization using EBO. 408 template<int _Nm, typename _Tp> 409 struct _Sp_ebo_helper<_Nm, _Tp, true> : private _Tp 410 { 411 explicit _Sp_ebo_helper(const _Tp& __tp) : _Tp(__tp) { } 412 413 static _Tp& 414 _S_get(_Sp_ebo_helper& __eboh) { return static_cast<_Tp&>(__eboh); } 415 }; 416 417 /// Specialization not using EBO. 418 template<int _Nm, typename _Tp> 419 struct _Sp_ebo_helper<_Nm, _Tp, false> 420 { 421 explicit _Sp_ebo_helper(const _Tp& __tp) : _M_tp(__tp) { } 422 423 static _Tp& 424 _S_get(_Sp_ebo_helper& __eboh) 425 { return __eboh._M_tp; } 426 427 private: 428 _Tp _M_tp; 429 }; 430 431 // Support for custom deleter and/or allocator 432 template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp> 433 class _Sp_counted_deleter final : public _Sp_counted_base<_Lp> 434 { 435 class _Impl : _Sp_ebo_helper<0, _Deleter>, _Sp_ebo_helper<1, _Alloc> 436 { 437 typedef _Sp_ebo_helper<0, _Deleter> _Del_base; 438 typedef _Sp_ebo_helper<1, _Alloc> _Alloc_base; 439 440 public: 441 _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept 442 : _M_ptr(__p), _Del_base(__d), _Alloc_base(__a) 443 { } 444 445 _Deleter& _M_del() noexcept { return _Del_base::_S_get(*this); } 446 _Alloc& _M_alloc() noexcept { return _Alloc_base::_S_get(*this); } 447 448 _Ptr _M_ptr; 449 }; 450 451 public: 452 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_deleter>; 453 454 // __d(__p) must not throw. 455 _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept 456 : _M_impl(__p, __d, _Alloc()) { } 457 458 // __d(__p) must not throw. 459 _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept 460 : _M_impl(__p, __d, __a) { } 461 462 ~_Sp_counted_deleter() noexcept { } 463 464 virtual void 465 _M_dispose() noexcept 466 { _M_impl._M_del()(_M_impl._M_ptr); } 467 468 virtual void 469 _M_destroy() noexcept 470 { 471 __allocator_type __a(_M_impl._M_alloc()); 472 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this }; 473 this->~_Sp_counted_deleter(); 474 } 475 476 virtual void* 477 _M_get_deleter(const std::type_info& __ti) noexcept 478 { 479 #if __cpp_rtti 480 // _GLIBCXX_RESOLVE_LIB_DEFECTS 481 // 2400. shared_ptr's get_deleter() should use addressof() 482 return __ti == typeid(_Deleter) 483 ? std::__addressof(_M_impl._M_del()) 484 : nullptr; 485 #else 486 return nullptr; 487 #endif 488 } 489 490 private: 491 _Impl _M_impl; 492 }; 493 494 // helpers for make_shared / allocate_shared 495 496 struct _Sp_make_shared_tag { }; 497 498 template<typename _Tp, typename _Alloc, _Lock_policy _Lp> 499 class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp> 500 { 501 class _Impl : _Sp_ebo_helper<0, _Alloc> 502 { 503 typedef _Sp_ebo_helper<0, _Alloc> _A_base; 504 505 public: 506 explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { } 507 508 _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); } 509 510 __gnu_cxx::__aligned_buffer<_Tp> _M_storage; 511 }; 512 513 public: 514 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>; 515 516 template<typename... _Args> 517 _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args) 518 : _M_impl(__a) 519 { 520 // _GLIBCXX_RESOLVE_LIB_DEFECTS 521 // 2070. allocate_shared should use allocator_traits<A>::construct 522 allocator_traits<_Alloc>::construct(__a, _M_ptr(), 523 std::forward<_Args>(__args)...); // might throw 524 } 525 526 ~_Sp_counted_ptr_inplace() noexcept { } 527 528 virtual void 529 _M_dispose() noexcept 530 { 531 allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr()); 532 } 533 534 // Override because the allocator needs to know the dynamic type 535 virtual void 536 _M_destroy() noexcept 537 { 538 __allocator_type __a(_M_impl._M_alloc()); 539 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this }; 540 this->~_Sp_counted_ptr_inplace(); 541 } 542 543 // Sneaky trick so __shared_ptr can get the managed pointer 544 virtual void* 545 _M_get_deleter(const std::type_info& __ti) noexcept 546 { 547 #if __cpp_rtti 548 if (__ti == typeid(_Sp_make_shared_tag)) 549 return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr()); 550 #endif 551 return nullptr; 552 } 553 554 private: 555 _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); } 556 557 _Impl _M_impl; 558 }; 559 560 561 template<_Lock_policy _Lp> 562 class __shared_count 563 { 564 public: 565 constexpr __shared_count() noexcept : _M_pi(0) 566 { } 567 568 template<typename _Ptr> 569 explicit 570 __shared_count(_Ptr __p) : _M_pi(0) 571 { 572 __try 573 { 574 _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p); 575 } 576 __catch(...) 577 { 578 delete __p; 579 __throw_exception_again; 580 } 581 } 582 583 template<typename _Ptr, typename _Deleter> 584 __shared_count(_Ptr __p, _Deleter __d) 585 : __shared_count(__p, std::move(__d), allocator<void>()) 586 { } 587 588 template<typename _Ptr, typename _Deleter, typename _Alloc> 589 __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0) 590 { 591 typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type; 592 __try 593 { 594 typename _Sp_cd_type::__allocator_type __a2(__a); 595 auto __guard = std::__allocate_guarded(__a2); 596 _Sp_cd_type* __mem = __guard.get(); 597 ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a)); 598 _M_pi = __mem; 599 __guard = nullptr; 600 } 601 __catch(...) 602 { 603 __d(__p); // Call _Deleter on __p. 604 __throw_exception_again; 605 } 606 } 607 608 template<typename _Tp, typename _Alloc, typename... _Args> 609 __shared_count(_Sp_make_shared_tag, _Tp*, const _Alloc& __a, 610 _Args&&... __args) 611 : _M_pi(0) 612 { 613 typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type; 614 typename _Sp_cp_type::__allocator_type __a2(__a); 615 auto __guard = std::__allocate_guarded(__a2); 616 _Sp_cp_type* __mem = __guard.get(); 617 ::new (__mem) _Sp_cp_type(std::move(__a), 618 std::forward<_Args>(__args)...); 619 _M_pi = __mem; 620 __guard = nullptr; 621 } 622 623 #if _GLIBCXX_USE_DEPRECATED 624 // Special case for auto_ptr<_Tp> to provide the strong guarantee. 625 template<typename _Tp> 626 explicit 627 __shared_count(std::auto_ptr<_Tp>&& __r); 628 #endif 629 630 // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee. 631 template<typename _Tp, typename _Del> 632 explicit 633 __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0) 634 { 635 using _Ptr = typename unique_ptr<_Tp, _Del>::pointer; 636 using _Del2 = typename conditional<is_reference<_Del>::value, 637 reference_wrapper<typename remove_reference<_Del>::type>, 638 _Del>::type; 639 using _Sp_cd_type 640 = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>; 641 using _Alloc = allocator<_Sp_cd_type>; 642 using _Alloc_traits = allocator_traits<_Alloc>; 643 _Alloc __a; 644 _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1); 645 _Alloc_traits::construct(__a, __mem, __r.release(), 646 __r.get_deleter()); // non-throwing 647 _M_pi = __mem; 648 } 649 650 // Throw bad_weak_ptr when __r._M_get_use_count() == 0. 651 explicit __shared_count(const __weak_count<_Lp>& __r); 652 653 // Does not throw if __r._M_get_use_count() == 0, caller must check. 654 explicit __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t); 655 656 ~__shared_count() noexcept 657 { 658 if (_M_pi != nullptr) 659 _M_pi->_M_release(); 660 } 661 662 __shared_count(const __shared_count& __r) noexcept 663 : _M_pi(__r._M_pi) 664 { 665 if (_M_pi != 0) 666 _M_pi->_M_add_ref_copy(); 667 } 668 669 __shared_count& 670 operator=(const __shared_count& __r) noexcept 671 { 672 _Sp_counted_base<_Lp>* __tmp = __r._M_pi; 673 if (__tmp != _M_pi) 674 { 675 if (__tmp != 0) 676 __tmp->_M_add_ref_copy(); 677 if (_M_pi != 0) 678 _M_pi->_M_release(); 679 _M_pi = __tmp; 680 } 681 return *this; 682 } 683 684 void 685 _M_swap(__shared_count& __r) noexcept 686 { 687 _Sp_counted_base<_Lp>* __tmp = __r._M_pi; 688 __r._M_pi = _M_pi; 689 _M_pi = __tmp; 690 } 691 692 long 693 _M_get_use_count() const noexcept 694 { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; } 695 696 bool 697 _M_unique() const noexcept 698 { return this->_M_get_use_count() == 1; } 699 700 void* 701 _M_get_deleter(const std::type_info& __ti) const noexcept 702 { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; } 703 704 bool 705 _M_less(const __shared_count& __rhs) const noexcept 706 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); } 707 708 bool 709 _M_less(const __weak_count<_Lp>& __rhs) const noexcept 710 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); } 711 712 // Friend function injected into enclosing namespace and found by ADL 713 friend inline bool 714 operator==(const __shared_count& __a, const __shared_count& __b) noexcept 715 { return __a._M_pi == __b._M_pi; } 716 717 private: 718 friend class __weak_count<_Lp>; 719 720 _Sp_counted_base<_Lp>* _M_pi; 721 }; 722 723 724 template<_Lock_policy _Lp> 725 class __weak_count 726 { 727 public: 728 constexpr __weak_count() noexcept : _M_pi(nullptr) 729 { } 730 731 __weak_count(const __shared_count<_Lp>& __r) noexcept 732 : _M_pi(__r._M_pi) 733 { 734 if (_M_pi != nullptr) 735 _M_pi->_M_weak_add_ref(); 736 } 737 738 __weak_count(const __weak_count& __r) noexcept 739 : _M_pi(__r._M_pi) 740 { 741 if (_M_pi != nullptr) 742 _M_pi->_M_weak_add_ref(); 743 } 744 745 __weak_count(__weak_count&& __r) noexcept 746 : _M_pi(__r._M_pi) 747 { __r._M_pi = nullptr; } 748 749 ~__weak_count() noexcept 750 { 751 if (_M_pi != nullptr) 752 _M_pi->_M_weak_release(); 753 } 754 755 __weak_count& 756 operator=(const __shared_count<_Lp>& __r) noexcept 757 { 758 _Sp_counted_base<_Lp>* __tmp = __r._M_pi; 759 if (__tmp != nullptr) 760 __tmp->_M_weak_add_ref(); 761 if (_M_pi != nullptr) 762 _M_pi->_M_weak_release(); 763 _M_pi = __tmp; 764 return *this; 765 } 766 767 __weak_count& 768 operator=(const __weak_count& __r) noexcept 769 { 770 _Sp_counted_base<_Lp>* __tmp = __r._M_pi; 771 if (__tmp != nullptr) 772 __tmp->_M_weak_add_ref(); 773 if (_M_pi != nullptr) 774 _M_pi->_M_weak_release(); 775 _M_pi = __tmp; 776 return *this; 777 } 778 779 __weak_count& 780 operator=(__weak_count&& __r) noexcept 781 { 782 if (_M_pi != nullptr) 783 _M_pi->_M_weak_release(); 784 _M_pi = __r._M_pi; 785 __r._M_pi = nullptr; 786 return *this; 787 } 788 789 void 790 _M_swap(__weak_count& __r) noexcept 791 { 792 _Sp_counted_base<_Lp>* __tmp = __r._M_pi; 793 __r._M_pi = _M_pi; 794 _M_pi = __tmp; 795 } 796 797 long 798 _M_get_use_count() const noexcept 799 { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; } 800 801 bool 802 _M_less(const __weak_count& __rhs) const noexcept 803 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); } 804 805 bool 806 _M_less(const __shared_count<_Lp>& __rhs) const noexcept 807 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); } 808 809 // Friend function injected into enclosing namespace and found by ADL 810 friend inline bool 811 operator==(const __weak_count& __a, const __weak_count& __b) noexcept 812 { return __a._M_pi == __b._M_pi; } 813 814 private: 815 friend class __shared_count<_Lp>; 816 817 _Sp_counted_base<_Lp>* _M_pi; 818 }; 819 820 // Now that __weak_count is defined we can define this constructor: 821 template<_Lock_policy _Lp> 822 inline 823 __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r) 824 : _M_pi(__r._M_pi) 825 { 826 if (_M_pi != nullptr) 827 _M_pi->_M_add_ref_lock(); 828 else 829 __throw_bad_weak_ptr(); 830 } 831 832 // Now that __weak_count is defined we can define this constructor: 833 template<_Lock_policy _Lp> 834 inline 835 __shared_count<_Lp>:: 836 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) 837 : _M_pi(__r._M_pi) 838 { 839 if (_M_pi != nullptr) 840 if (!_M_pi->_M_add_ref_lock_nothrow()) 841 _M_pi = nullptr; 842 } 843 844 // Support for enable_shared_from_this. 845 846 // Friend of __enable_shared_from_this. 847 template<_Lock_policy _Lp, typename _Tp1, typename _Tp2> 848 void 849 __enable_shared_from_this_helper(const __shared_count<_Lp>&, 850 const __enable_shared_from_this<_Tp1, 851 _Lp>*, const _Tp2*) noexcept; 852 853 // Friend of enable_shared_from_this. 854 template<typename _Tp1, typename _Tp2> 855 void 856 __enable_shared_from_this_helper(const __shared_count<>&, 857 const enable_shared_from_this<_Tp1>*, 858 const _Tp2*) noexcept; 859 860 template<_Lock_policy _Lp> 861 inline void 862 __enable_shared_from_this_helper(const __shared_count<_Lp>&, ...) noexcept 863 { } 864 865 866 template<typename _Tp, _Lock_policy _Lp> 867 class __shared_ptr 868 { 869 template<typename _Ptr> 870 using _Convertible 871 = typename enable_if<is_convertible<_Ptr, _Tp*>::value>::type; 872 873 public: 874 typedef _Tp element_type; 875 876 constexpr __shared_ptr() noexcept 877 : _M_ptr(0), _M_refcount() 878 { } 879 880 template<typename _Tp1> 881 explicit __shared_ptr(_Tp1* __p) 882 : _M_ptr(__p), _M_refcount(__p) 883 { 884 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 885 static_assert( !is_void<_Tp1>::value, "incomplete type" ); 886 static_assert( sizeof(_Tp1) > 0, "incomplete type" ); 887 __enable_shared_from_this_helper(_M_refcount, __p, __p); 888 } 889 890 template<typename _Tp1, typename _Deleter> 891 __shared_ptr(_Tp1* __p, _Deleter __d) 892 : _M_ptr(__p), _M_refcount(__p, __d) 893 { 894 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 895 // TODO requires _Deleter CopyConstructible and __d(__p) well-formed 896 __enable_shared_from_this_helper(_M_refcount, __p, __p); 897 } 898 899 template<typename _Tp1, typename _Deleter, typename _Alloc> 900 __shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a) 901 : _M_ptr(__p), _M_refcount(__p, __d, std::move(__a)) 902 { 903 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 904 // TODO requires _Deleter CopyConstructible and __d(__p) well-formed 905 __enable_shared_from_this_helper(_M_refcount, __p, __p); 906 } 907 908 template<typename _Deleter> 909 __shared_ptr(nullptr_t __p, _Deleter __d) 910 : _M_ptr(0), _M_refcount(__p, __d) 911 { } 912 913 template<typename _Deleter, typename _Alloc> 914 __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a) 915 : _M_ptr(0), _M_refcount(__p, __d, std::move(__a)) 916 { } 917 918 template<typename _Tp1> 919 __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, _Tp* __p) noexcept 920 : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws 921 { } 922 923 __shared_ptr(const __shared_ptr&) noexcept = default; 924 __shared_ptr& operator=(const __shared_ptr&) noexcept = default; 925 ~__shared_ptr() = default; 926 927 template<typename _Tp1, typename = _Convertible<_Tp1*>> 928 __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 929 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) 930 { } 931 932 __shared_ptr(__shared_ptr&& __r) noexcept 933 : _M_ptr(__r._M_ptr), _M_refcount() 934 { 935 _M_refcount._M_swap(__r._M_refcount); 936 __r._M_ptr = 0; 937 } 938 939 template<typename _Tp1, typename = _Convertible<_Tp1*>> 940 __shared_ptr(__shared_ptr<_Tp1, _Lp>&& __r) noexcept 941 : _M_ptr(__r._M_ptr), _M_refcount() 942 { 943 _M_refcount._M_swap(__r._M_refcount); 944 __r._M_ptr = 0; 945 } 946 947 template<typename _Tp1> 948 explicit __shared_ptr(const __weak_ptr<_Tp1, _Lp>& __r) 949 : _M_refcount(__r._M_refcount) // may throw 950 { 951 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 952 953 // It is now safe to copy __r._M_ptr, as 954 // _M_refcount(__r._M_refcount) did not throw. 955 _M_ptr = __r._M_ptr; 956 } 957 958 // If an exception is thrown this constructor has no effect. 959 template<typename _Tp1, typename _Del, typename 960 = _Convertible<typename unique_ptr<_Tp1, _Del>::pointer>> 961 __shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r) 962 : _M_ptr(__r.get()), _M_refcount() 963 { 964 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 965 auto __raw = _S_raw_ptr(__r.get()); 966 _M_refcount = __shared_count<_Lp>(std::move(__r)); 967 __enable_shared_from_this_helper(_M_refcount, __raw, __raw); 968 } 969 970 #if _GLIBCXX_USE_DEPRECATED 971 // Postcondition: use_count() == 1 and __r.get() == 0 972 template<typename _Tp1> 973 __shared_ptr(std::auto_ptr<_Tp1>&& __r); 974 #endif 975 976 constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { } 977 978 template<typename _Tp1> 979 __shared_ptr& 980 operator=(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 981 { 982 _M_ptr = __r._M_ptr; 983 _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw 984 return *this; 985 } 986 987 #if _GLIBCXX_USE_DEPRECATED 988 template<typename _Tp1> 989 __shared_ptr& 990 operator=(std::auto_ptr<_Tp1>&& __r) 991 { 992 __shared_ptr(std::move(__r)).swap(*this); 993 return *this; 994 } 995 #endif 996 997 __shared_ptr& 998 operator=(__shared_ptr&& __r) noexcept 999 { 1000 __shared_ptr(std::move(__r)).swap(*this); 1001 return *this; 1002 } 1003 1004 template<class _Tp1> 1005 __shared_ptr& 1006 operator=(__shared_ptr<_Tp1, _Lp>&& __r) noexcept 1007 { 1008 __shared_ptr(std::move(__r)).swap(*this); 1009 return *this; 1010 } 1011 1012 template<typename _Tp1, typename _Del> 1013 __shared_ptr& 1014 operator=(std::unique_ptr<_Tp1, _Del>&& __r) 1015 { 1016 __shared_ptr(std::move(__r)).swap(*this); 1017 return *this; 1018 } 1019 1020 void 1021 reset() noexcept 1022 { __shared_ptr().swap(*this); } 1023 1024 template<typename _Tp1> 1025 void 1026 reset(_Tp1* __p) // _Tp1 must be complete. 1027 { 1028 // Catch self-reset errors. 1029 _GLIBCXX_DEBUG_ASSERT(__p == 0 || __p != _M_ptr); 1030 __shared_ptr(__p).swap(*this); 1031 } 1032 1033 template<typename _Tp1, typename _Deleter> 1034 void 1035 reset(_Tp1* __p, _Deleter __d) 1036 { __shared_ptr(__p, __d).swap(*this); } 1037 1038 template<typename _Tp1, typename _Deleter, typename _Alloc> 1039 void 1040 reset(_Tp1* __p, _Deleter __d, _Alloc __a) 1041 { __shared_ptr(__p, __d, std::move(__a)).swap(*this); } 1042 1043 // Allow class instantiation when _Tp is [cv-qual] void. 1044 typename std::add_lvalue_reference<_Tp>::type 1045 operator*() const noexcept 1046 { 1047 _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); 1048 return *_M_ptr; 1049 } 1050 1051 _Tp* 1052 operator->() const noexcept 1053 { 1054 _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); 1055 return _M_ptr; 1056 } 1057 1058 _Tp* 1059 get() const noexcept 1060 { return _M_ptr; } 1061 1062 explicit operator bool() const // never throws 1063 { return _M_ptr == 0 ? false : true; } 1064 1065 bool 1066 unique() const noexcept 1067 { return _M_refcount._M_unique(); } 1068 1069 long 1070 use_count() const noexcept 1071 { return _M_refcount._M_get_use_count(); } 1072 1073 void 1074 swap(__shared_ptr<_Tp, _Lp>& __other) noexcept 1075 { 1076 std::swap(_M_ptr, __other._M_ptr); 1077 _M_refcount._M_swap(__other._M_refcount); 1078 } 1079 1080 template<typename _Tp1> 1081 bool 1082 owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const 1083 { return _M_refcount._M_less(__rhs._M_refcount); } 1084 1085 template<typename _Tp1> 1086 bool 1087 owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const 1088 { return _M_refcount._M_less(__rhs._M_refcount); } 1089 1090 #if __cpp_rtti 1091 protected: 1092 // This constructor is non-standard, it is used by allocate_shared. 1093 template<typename _Alloc, typename... _Args> 1094 __shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a, 1095 _Args&&... __args) 1096 : _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a, 1097 std::forward<_Args>(__args)...) 1098 { 1099 // _M_ptr needs to point to the newly constructed object. 1100 // This relies on _Sp_counted_ptr_inplace::_M_get_deleter. 1101 void* __p = _M_refcount._M_get_deleter(typeid(__tag)); 1102 _M_ptr = static_cast<_Tp*>(__p); 1103 __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr); 1104 } 1105 #else 1106 template<typename _Alloc> 1107 struct _Deleter 1108 { 1109 void operator()(typename _Alloc::value_type* __ptr) 1110 { 1111 __allocated_ptr<_Alloc> __guard{ _M_alloc, __ptr }; 1112 allocator_traits<_Alloc>::destroy(_M_alloc, __guard.get()); 1113 } 1114 _Alloc _M_alloc; 1115 }; 1116 1117 template<typename _Alloc, typename... _Args> 1118 __shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a, 1119 _Args&&... __args) 1120 : _M_ptr(), _M_refcount() 1121 { 1122 typedef typename allocator_traits<_Alloc>::template 1123 rebind_traits<typename std::remove_cv<_Tp>::type> __traits; 1124 _Deleter<typename __traits::allocator_type> __del = { __a }; 1125 auto __guard = std::__allocate_guarded(__del._M_alloc); 1126 auto __ptr = __guard.get(); 1127 // _GLIBCXX_RESOLVE_LIB_DEFECTS 1128 // 2070. allocate_shared should use allocator_traits<A>::construct 1129 __traits::construct(__del._M_alloc, __ptr, 1130 std::forward<_Args>(__args)...); 1131 __guard = nullptr; 1132 __shared_count<_Lp> __count(__ptr, __del, __del._M_alloc); 1133 _M_refcount._M_swap(__count); 1134 _M_ptr = __ptr; 1135 __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr); 1136 } 1137 #endif 1138 1139 template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc, 1140 typename... _Args> 1141 friend __shared_ptr<_Tp1, _Lp1> 1142 __allocate_shared(const _Alloc& __a, _Args&&... __args); 1143 1144 // This constructor is used by __weak_ptr::lock() and 1145 // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t). 1146 __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t) 1147 : _M_refcount(__r._M_refcount, std::nothrow) 1148 { 1149 _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr; 1150 } 1151 1152 friend class __weak_ptr<_Tp, _Lp>; 1153 1154 private: 1155 void* 1156 _M_get_deleter(const std::type_info& __ti) const noexcept 1157 { return _M_refcount._M_get_deleter(__ti); } 1158 1159 template<typename _Tp1> 1160 static _Tp1* 1161 _S_raw_ptr(_Tp1* __ptr) 1162 { return __ptr; } 1163 1164 template<typename _Tp1> 1165 static auto 1166 _S_raw_ptr(_Tp1 __ptr) -> decltype(std::__addressof(*__ptr)) 1167 { return std::__addressof(*__ptr); } 1168 1169 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr; 1170 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr; 1171 1172 template<typename _Del, typename _Tp1, _Lock_policy _Lp1> 1173 friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept; 1174 1175 _Tp* _M_ptr; // Contained pointer. 1176 __shared_count<_Lp> _M_refcount; // Reference counter. 1177 }; 1178 1179 1180 // 20.7.2.2.7 shared_ptr comparisons 1181 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp> 1182 inline bool 1183 operator==(const __shared_ptr<_Tp1, _Lp>& __a, 1184 const __shared_ptr<_Tp2, _Lp>& __b) noexcept 1185 { return __a.get() == __b.get(); } 1186 1187 template<typename _Tp, _Lock_policy _Lp> 1188 inline bool 1189 operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept 1190 { return !__a; } 1191 1192 template<typename _Tp, _Lock_policy _Lp> 1193 inline bool 1194 operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept 1195 { return !__a; } 1196 1197 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp> 1198 inline bool 1199 operator!=(const __shared_ptr<_Tp1, _Lp>& __a, 1200 const __shared_ptr<_Tp2, _Lp>& __b) noexcept 1201 { return __a.get() != __b.get(); } 1202 1203 template<typename _Tp, _Lock_policy _Lp> 1204 inline bool 1205 operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept 1206 { return (bool)__a; } 1207 1208 template<typename _Tp, _Lock_policy _Lp> 1209 inline bool 1210 operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept 1211 { return (bool)__a; } 1212 1213 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp> 1214 inline bool 1215 operator<(const __shared_ptr<_Tp1, _Lp>& __a, 1216 const __shared_ptr<_Tp2, _Lp>& __b) noexcept 1217 { 1218 typedef typename std::common_type<_Tp1*, _Tp2*>::type _CT; 1219 return std::less<_CT>()(__a.get(), __b.get()); 1220 } 1221 1222 template<typename _Tp, _Lock_policy _Lp> 1223 inline bool 1224 operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept 1225 { return std::less<_Tp*>()(__a.get(), nullptr); } 1226 1227 template<typename _Tp, _Lock_policy _Lp> 1228 inline bool 1229 operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept 1230 { return std::less<_Tp*>()(nullptr, __a.get()); } 1231 1232 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp> 1233 inline bool 1234 operator<=(const __shared_ptr<_Tp1, _Lp>& __a, 1235 const __shared_ptr<_Tp2, _Lp>& __b) noexcept 1236 { return !(__b < __a); } 1237 1238 template<typename _Tp, _Lock_policy _Lp> 1239 inline bool 1240 operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept 1241 { return !(nullptr < __a); } 1242 1243 template<typename _Tp, _Lock_policy _Lp> 1244 inline bool 1245 operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept 1246 { return !(__a < nullptr); } 1247 1248 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp> 1249 inline bool 1250 operator>(const __shared_ptr<_Tp1, _Lp>& __a, 1251 const __shared_ptr<_Tp2, _Lp>& __b) noexcept 1252 { return (__b < __a); } 1253 1254 template<typename _Tp, _Lock_policy _Lp> 1255 inline bool 1256 operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept 1257 { return std::less<_Tp*>()(nullptr, __a.get()); } 1258 1259 template<typename _Tp, _Lock_policy _Lp> 1260 inline bool 1261 operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept 1262 { return std::less<_Tp*>()(__a.get(), nullptr); } 1263 1264 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp> 1265 inline bool 1266 operator>=(const __shared_ptr<_Tp1, _Lp>& __a, 1267 const __shared_ptr<_Tp2, _Lp>& __b) noexcept 1268 { return !(__a < __b); } 1269 1270 template<typename _Tp, _Lock_policy _Lp> 1271 inline bool 1272 operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept 1273 { return !(__a < nullptr); } 1274 1275 template<typename _Tp, _Lock_policy _Lp> 1276 inline bool 1277 operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept 1278 { return !(nullptr < __a); } 1279 1280 template<typename _Sp> 1281 struct _Sp_less : public binary_function<_Sp, _Sp, bool> 1282 { 1283 bool 1284 operator()(const _Sp& __lhs, const _Sp& __rhs) const noexcept 1285 { 1286 typedef typename _Sp::element_type element_type; 1287 return std::less<element_type*>()(__lhs.get(), __rhs.get()); 1288 } 1289 }; 1290 1291 template<typename _Tp, _Lock_policy _Lp> 1292 struct less<__shared_ptr<_Tp, _Lp>> 1293 : public _Sp_less<__shared_ptr<_Tp, _Lp>> 1294 { }; 1295 1296 // 20.7.2.2.8 shared_ptr specialized algorithms. 1297 template<typename _Tp, _Lock_policy _Lp> 1298 inline void 1299 swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept 1300 { __a.swap(__b); } 1301 1302 // 20.7.2.2.9 shared_ptr casts 1303 1304 // The seemingly equivalent code: 1305 // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get())) 1306 // will eventually result in undefined behaviour, attempting to 1307 // delete the same object twice. 1308 /// static_pointer_cast 1309 template<typename _Tp, typename _Tp1, _Lock_policy _Lp> 1310 inline __shared_ptr<_Tp, _Lp> 1311 static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 1312 { return __shared_ptr<_Tp, _Lp>(__r, static_cast<_Tp*>(__r.get())); } 1313 1314 // The seemingly equivalent code: 1315 // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get())) 1316 // will eventually result in undefined behaviour, attempting to 1317 // delete the same object twice. 1318 /// const_pointer_cast 1319 template<typename _Tp, typename _Tp1, _Lock_policy _Lp> 1320 inline __shared_ptr<_Tp, _Lp> 1321 const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 1322 { return __shared_ptr<_Tp, _Lp>(__r, const_cast<_Tp*>(__r.get())); } 1323 1324 // The seemingly equivalent code: 1325 // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get())) 1326 // will eventually result in undefined behaviour, attempting to 1327 // delete the same object twice. 1328 /// dynamic_pointer_cast 1329 template<typename _Tp, typename _Tp1, _Lock_policy _Lp> 1330 inline __shared_ptr<_Tp, _Lp> 1331 dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 1332 { 1333 if (_Tp* __p = dynamic_cast<_Tp*>(__r.get())) 1334 return __shared_ptr<_Tp, _Lp>(__r, __p); 1335 return __shared_ptr<_Tp, _Lp>(); 1336 } 1337 1338 1339 template<typename _Tp, _Lock_policy _Lp> 1340 class __weak_ptr 1341 { 1342 template<typename _Ptr> 1343 using _Convertible 1344 = typename enable_if<is_convertible<_Ptr, _Tp*>::value>::type; 1345 1346 public: 1347 typedef _Tp element_type; 1348 1349 constexpr __weak_ptr() noexcept 1350 : _M_ptr(nullptr), _M_refcount() 1351 { } 1352 1353 __weak_ptr(const __weak_ptr&) noexcept = default; 1354 1355 ~__weak_ptr() = default; 1356 1357 // The "obvious" converting constructor implementation: 1358 // 1359 // template<typename _Tp1> 1360 // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r) 1361 // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws 1362 // { } 1363 // 1364 // has a serious problem. 1365 // 1366 // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr) 1367 // conversion may require access to *__r._M_ptr (virtual inheritance). 1368 // 1369 // It is not possible to avoid spurious access violations since 1370 // in multithreaded programs __r._M_ptr may be invalidated at any point. 1371 template<typename _Tp1, typename = _Convertible<_Tp1*>> 1372 __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r) noexcept 1373 : _M_refcount(__r._M_refcount) 1374 { _M_ptr = __r.lock().get(); } 1375 1376 template<typename _Tp1, typename = _Convertible<_Tp1*>> 1377 __weak_ptr(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 1378 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) 1379 { } 1380 1381 __weak_ptr(__weak_ptr&& __r) noexcept 1382 : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount)) 1383 { __r._M_ptr = nullptr; } 1384 1385 template<typename _Tp1, typename = _Convertible<_Tp1*>> 1386 __weak_ptr(__weak_ptr<_Tp1, _Lp>&& __r) noexcept 1387 : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount)) 1388 { __r._M_ptr = nullptr; } 1389 1390 __weak_ptr& 1391 operator=(const __weak_ptr& __r) noexcept = default; 1392 1393 template<typename _Tp1> 1394 __weak_ptr& 1395 operator=(const __weak_ptr<_Tp1, _Lp>& __r) noexcept 1396 { 1397 _M_ptr = __r.lock().get(); 1398 _M_refcount = __r._M_refcount; 1399 return *this; 1400 } 1401 1402 template<typename _Tp1> 1403 __weak_ptr& 1404 operator=(const __shared_ptr<_Tp1, _Lp>& __r) noexcept 1405 { 1406 _M_ptr = __r._M_ptr; 1407 _M_refcount = __r._M_refcount; 1408 return *this; 1409 } 1410 1411 __weak_ptr& 1412 operator=(__weak_ptr&& __r) noexcept 1413 { 1414 _M_ptr = __r._M_ptr; 1415 _M_refcount = std::move(__r._M_refcount); 1416 __r._M_ptr = nullptr; 1417 return *this; 1418 } 1419 1420 template<typename _Tp1> 1421 __weak_ptr& 1422 operator=(__weak_ptr<_Tp1, _Lp>&& __r) noexcept 1423 { 1424 _M_ptr = __r.lock().get(); 1425 _M_refcount = std::move(__r._M_refcount); 1426 __r._M_ptr = nullptr; 1427 return *this; 1428 } 1429 1430 __shared_ptr<_Tp, _Lp> 1431 lock() const noexcept 1432 { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); } 1433 1434 long 1435 use_count() const noexcept 1436 { return _M_refcount._M_get_use_count(); } 1437 1438 bool 1439 expired() const noexcept 1440 { return _M_refcount._M_get_use_count() == 0; } 1441 1442 template<typename _Tp1> 1443 bool 1444 owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const 1445 { return _M_refcount._M_less(__rhs._M_refcount); } 1446 1447 template<typename _Tp1> 1448 bool 1449 owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const 1450 { return _M_refcount._M_less(__rhs._M_refcount); } 1451 1452 void 1453 reset() noexcept 1454 { __weak_ptr().swap(*this); } 1455 1456 void 1457 swap(__weak_ptr& __s) noexcept 1458 { 1459 std::swap(_M_ptr, __s._M_ptr); 1460 _M_refcount._M_swap(__s._M_refcount); 1461 } 1462 1463 private: 1464 // Used by __enable_shared_from_this. 1465 void 1466 _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept 1467 { 1468 _M_ptr = __ptr; 1469 _M_refcount = __refcount; 1470 } 1471 1472 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr; 1473 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr; 1474 friend class __enable_shared_from_this<_Tp, _Lp>; 1475 friend class enable_shared_from_this<_Tp>; 1476 1477 _Tp* _M_ptr; // Contained pointer. 1478 __weak_count<_Lp> _M_refcount; // Reference counter. 1479 }; 1480 1481 // 20.7.2.3.6 weak_ptr specialized algorithms. 1482 template<typename _Tp, _Lock_policy _Lp> 1483 inline void 1484 swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept 1485 { __a.swap(__b); } 1486 1487 template<typename _Tp, typename _Tp1> 1488 struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool> 1489 { 1490 bool 1491 operator()(const _Tp& __lhs, const _Tp& __rhs) const 1492 { return __lhs.owner_before(__rhs); } 1493 1494 bool 1495 operator()(const _Tp& __lhs, const _Tp1& __rhs) const 1496 { return __lhs.owner_before(__rhs); } 1497 1498 bool 1499 operator()(const _Tp1& __lhs, const _Tp& __rhs) const 1500 { return __lhs.owner_before(__rhs); } 1501 }; 1502 1503 template<typename _Tp, _Lock_policy _Lp> 1504 struct owner_less<__shared_ptr<_Tp, _Lp>> 1505 : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>> 1506 { }; 1507 1508 template<typename _Tp, _Lock_policy _Lp> 1509 struct owner_less<__weak_ptr<_Tp, _Lp>> 1510 : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>> 1511 { }; 1512 1513 1514 template<typename _Tp, _Lock_policy _Lp> 1515 class __enable_shared_from_this 1516 { 1517 protected: 1518 constexpr __enable_shared_from_this() noexcept { } 1519 1520 __enable_shared_from_this(const __enable_shared_from_this&) noexcept { } 1521 1522 __enable_shared_from_this& 1523 operator=(const __enable_shared_from_this&) noexcept 1524 { return *this; } 1525 1526 ~__enable_shared_from_this() { } 1527 1528 public: 1529 __shared_ptr<_Tp, _Lp> 1530 shared_from_this() 1531 { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); } 1532 1533 __shared_ptr<const _Tp, _Lp> 1534 shared_from_this() const 1535 { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); } 1536 1537 private: 1538 template<typename _Tp1> 1539 void 1540 _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept 1541 { _M_weak_this._M_assign(__p, __n); } 1542 1543 template<_Lock_policy _Lp1, typename _Tp1, typename _Tp2> 1544 friend void 1545 __enable_shared_from_this_helper(const __shared_count<_Lp1>&, 1546 const __enable_shared_from_this<_Tp1, 1547 _Lp1>*, const _Tp2*) noexcept; 1548 1549 mutable __weak_ptr<_Tp, _Lp> _M_weak_this; 1550 }; 1551 1552 template<_Lock_policy _Lp1, typename _Tp1, typename _Tp2> 1553 inline void 1554 __enable_shared_from_this_helper(const __shared_count<_Lp1>& __pn, 1555 const __enable_shared_from_this<_Tp1, 1556 _Lp1>* __pe, 1557 const _Tp2* __px) noexcept 1558 { 1559 if (__pe != nullptr) 1560 __pe->_M_weak_assign(const_cast<_Tp2*>(__px), __pn); 1561 } 1562 1563 template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args> 1564 inline __shared_ptr<_Tp, _Lp> 1565 __allocate_shared(const _Alloc& __a, _Args&&... __args) 1566 { 1567 return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(), __a, 1568 std::forward<_Args>(__args)...); 1569 } 1570 1571 template<typename _Tp, _Lock_policy _Lp, typename... _Args> 1572 inline __shared_ptr<_Tp, _Lp> 1573 __make_shared(_Args&&... __args) 1574 { 1575 typedef typename std::remove_const<_Tp>::type _Tp_nc; 1576 return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(), 1577 std::forward<_Args>(__args)...); 1578 } 1579 1580 /// std::hash specialization for __shared_ptr. 1581 template<typename _Tp, _Lock_policy _Lp> 1582 struct hash<__shared_ptr<_Tp, _Lp>> 1583 : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>> 1584 { 1585 size_t 1586 operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept 1587 { return std::hash<_Tp*>()(__s.get()); } 1588 }; 1589 1590 _GLIBCXX_END_NAMESPACE_VERSION 1591 } // namespace 1592 1593 #endif // _SHARED_PTR_BASE_H 1594