1 // shared_ptr and weak_ptr implementation -*- C++ -*- 2 3 // Copyright (C) 2007-2017 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 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_H 50 #define _SHARED_PTR_H 1 51 52 #include <bits/shared_ptr_base.h> 53 54 namespace std _GLIBCXX_VISIBILITY(default) 55 { 56 _GLIBCXX_BEGIN_NAMESPACE_VERSION 57 58 /** 59 * @addtogroup pointer_abstractions 60 * @{ 61 */ 62 63 /// 20.7.2.2.11 shared_ptr I/O 64 template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp> 65 inline std::basic_ostream<_Ch, _Tr>& 66 operator<<(std::basic_ostream<_Ch, _Tr>& __os, 67 const __shared_ptr<_Tp, _Lp>& __p) 68 { 69 __os << __p.get(); 70 return __os; 71 } 72 73 /// 20.7.2.2.10 shared_ptr get_deleter 74 template<typename _Del, typename _Tp, _Lock_policy _Lp> 75 inline _Del* 76 get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept 77 { 78 #if __cpp_rtti 79 return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del))); 80 #else 81 return 0; 82 #endif 83 } 84 85 86 /** 87 * @brief A smart pointer with reference-counted copy semantics. 88 * 89 * The object pointed to is deleted when the last shared_ptr pointing to 90 * it is destroyed or reset. 91 */ 92 template<typename _Tp> 93 class shared_ptr : public __shared_ptr<_Tp> 94 { 95 template<typename... _Args> 96 using _Constructible = typename enable_if< 97 is_constructible<__shared_ptr<_Tp>, _Args...>::value 98 >::type; 99 100 template<typename _Arg> 101 using _Assignable = typename enable_if< 102 is_assignable<__shared_ptr<_Tp>&, _Arg>::value, shared_ptr& 103 >::type; 104 105 public: 106 107 using element_type = typename __shared_ptr<_Tp>::element_type; 108 109 #if __cplusplus > 201402L 110 # define __cpp_lib_shared_ptr_weak_type 201606 111 using weak_type = weak_ptr<_Tp>; 112 #endif 113 /** 114 * @brief Construct an empty %shared_ptr. 115 * @post use_count()==0 && get()==0 116 */ 117 constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { } 118 119 shared_ptr(const shared_ptr&) noexcept = default; 120 121 /** 122 * @brief Construct a %shared_ptr that owns the pointer @a __p. 123 * @param __p A pointer that is convertible to element_type*. 124 * @post use_count() == 1 && get() == __p 125 * @throw std::bad_alloc, in which case @c delete @a __p is called. 126 */ 127 template<typename _Yp, typename = _Constructible<_Yp*>> 128 explicit 129 shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { } 130 131 /** 132 * @brief Construct a %shared_ptr that owns the pointer @a __p 133 * and the deleter @a __d. 134 * @param __p A pointer. 135 * @param __d A deleter. 136 * @post use_count() == 1 && get() == __p 137 * @throw std::bad_alloc, in which case @a __d(__p) is called. 138 * 139 * Requirements: _Deleter's copy constructor and destructor must 140 * not throw 141 * 142 * __shared_ptr will release __p by calling __d(__p) 143 */ 144 template<typename _Yp, typename _Deleter, 145 typename = _Constructible<_Yp*, _Deleter>> 146 shared_ptr(_Yp* __p, _Deleter __d) 147 : __shared_ptr<_Tp>(__p, std::move(__d)) { } 148 149 /** 150 * @brief Construct a %shared_ptr that owns a null pointer 151 * and the deleter @a __d. 152 * @param __p A null pointer constant. 153 * @param __d A deleter. 154 * @post use_count() == 1 && get() == __p 155 * @throw std::bad_alloc, in which case @a __d(__p) is called. 156 * 157 * Requirements: _Deleter's copy constructor and destructor must 158 * not throw 159 * 160 * The last owner will call __d(__p) 161 */ 162 template<typename _Deleter> 163 shared_ptr(nullptr_t __p, _Deleter __d) 164 : __shared_ptr<_Tp>(__p, std::move(__d)) { } 165 166 /** 167 * @brief Construct a %shared_ptr that owns the pointer @a __p 168 * and the deleter @a __d. 169 * @param __p A pointer. 170 * @param __d A deleter. 171 * @param __a An allocator. 172 * @post use_count() == 1 && get() == __p 173 * @throw std::bad_alloc, in which case @a __d(__p) is called. 174 * 175 * Requirements: _Deleter's copy constructor and destructor must 176 * not throw _Alloc's copy constructor and destructor must not 177 * throw. 178 * 179 * __shared_ptr will release __p by calling __d(__p) 180 */ 181 template<typename _Yp, typename _Deleter, typename _Alloc, 182 typename = _Constructible<_Yp*, _Deleter, _Alloc>> 183 shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a) 184 : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { } 185 186 /** 187 * @brief Construct a %shared_ptr that owns a null pointer 188 * and the deleter @a __d. 189 * @param __p A null pointer constant. 190 * @param __d A deleter. 191 * @param __a An allocator. 192 * @post use_count() == 1 && get() == __p 193 * @throw std::bad_alloc, in which case @a __d(__p) is called. 194 * 195 * Requirements: _Deleter's copy constructor and destructor must 196 * not throw _Alloc's copy constructor and destructor must not 197 * throw. 198 * 199 * The last owner will call __d(__p) 200 */ 201 template<typename _Deleter, typename _Alloc> 202 shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a) 203 : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { } 204 205 // Aliasing constructor 206 207 /** 208 * @brief Constructs a %shared_ptr instance that stores @a __p 209 * and shares ownership with @a __r. 210 * @param __r A %shared_ptr. 211 * @param __p A pointer that will remain valid while @a *__r is valid. 212 * @post get() == __p && use_count() == __r.use_count() 213 * 214 * This can be used to construct a @c shared_ptr to a sub-object 215 * of an object managed by an existing @c shared_ptr. 216 * 217 * @code 218 * shared_ptr< pair<int,int> > pii(new pair<int,int>()); 219 * shared_ptr<int> pi(pii, &pii->first); 220 * assert(pii.use_count() == 2); 221 * @endcode 222 */ 223 template<typename _Yp> 224 shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) noexcept 225 : __shared_ptr<_Tp>(__r, __p) { } 226 227 /** 228 * @brief If @a __r is empty, constructs an empty %shared_ptr; 229 * otherwise construct a %shared_ptr that shares ownership 230 * with @a __r. 231 * @param __r A %shared_ptr. 232 * @post get() == __r.get() && use_count() == __r.use_count() 233 */ 234 template<typename _Yp, 235 typename = _Constructible<const shared_ptr<_Yp>&>> 236 shared_ptr(const shared_ptr<_Yp>& __r) noexcept 237 : __shared_ptr<_Tp>(__r) { } 238 239 /** 240 * @brief Move-constructs a %shared_ptr instance from @a __r. 241 * @param __r A %shared_ptr rvalue. 242 * @post *this contains the old value of @a __r, @a __r is empty. 243 */ 244 shared_ptr(shared_ptr&& __r) noexcept 245 : __shared_ptr<_Tp>(std::move(__r)) { } 246 247 /** 248 * @brief Move-constructs a %shared_ptr instance from @a __r. 249 * @param __r A %shared_ptr rvalue. 250 * @post *this contains the old value of @a __r, @a __r is empty. 251 */ 252 template<typename _Yp, typename = _Constructible<shared_ptr<_Yp>>> 253 shared_ptr(shared_ptr<_Yp>&& __r) noexcept 254 : __shared_ptr<_Tp>(std::move(__r)) { } 255 256 /** 257 * @brief Constructs a %shared_ptr that shares ownership with @a __r 258 * and stores a copy of the pointer stored in @a __r. 259 * @param __r A weak_ptr. 260 * @post use_count() == __r.use_count() 261 * @throw bad_weak_ptr when __r.expired(), 262 * in which case the constructor has no effect. 263 */ 264 template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>> 265 explicit shared_ptr(const weak_ptr<_Yp>& __r) 266 : __shared_ptr<_Tp>(__r) { } 267 268 #if _GLIBCXX_USE_DEPRECATED 269 template<typename _Yp, typename = _Constructible<auto_ptr<_Yp>>> 270 shared_ptr(auto_ptr<_Yp>&& __r); 271 #endif 272 273 // _GLIBCXX_RESOLVE_LIB_DEFECTS 274 // 2399. shared_ptr's constructor from unique_ptr should be constrained 275 template<typename _Yp, typename _Del, 276 typename = _Constructible<unique_ptr<_Yp, _Del>>> 277 shared_ptr(unique_ptr<_Yp, _Del>&& __r) 278 : __shared_ptr<_Tp>(std::move(__r)) { } 279 280 #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED 281 // This non-standard constructor exists to support conversions that 282 // were possible in C++11 and C++14 but are ill-formed in C++17. 283 // If an exception is thrown this constructor has no effect. 284 template<typename _Yp, typename _Del, 285 _Constructible<unique_ptr<_Yp, _Del>, __sp_array_delete>* = 0> 286 shared_ptr(unique_ptr<_Yp, _Del>&& __r) 287 : __shared_ptr<_Tp>(std::move(__r), __sp_array_delete()) { } 288 #endif 289 290 /** 291 * @brief Construct an empty %shared_ptr. 292 * @post use_count() == 0 && get() == nullptr 293 */ 294 constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { } 295 296 shared_ptr& operator=(const shared_ptr&) noexcept = default; 297 298 template<typename _Yp> 299 _Assignable<const shared_ptr<_Yp>&> 300 operator=(const shared_ptr<_Yp>& __r) noexcept 301 { 302 this->__shared_ptr<_Tp>::operator=(__r); 303 return *this; 304 } 305 306 #if _GLIBCXX_USE_DEPRECATED 307 template<typename _Yp> 308 _Assignable<auto_ptr<_Yp>> 309 operator=(auto_ptr<_Yp>&& __r) 310 { 311 this->__shared_ptr<_Tp>::operator=(std::move(__r)); 312 return *this; 313 } 314 #endif 315 316 shared_ptr& 317 operator=(shared_ptr&& __r) noexcept 318 { 319 this->__shared_ptr<_Tp>::operator=(std::move(__r)); 320 return *this; 321 } 322 323 template<class _Yp> 324 _Assignable<shared_ptr<_Yp>> 325 operator=(shared_ptr<_Yp>&& __r) noexcept 326 { 327 this->__shared_ptr<_Tp>::operator=(std::move(__r)); 328 return *this; 329 } 330 331 template<typename _Yp, typename _Del> 332 _Assignable<unique_ptr<_Yp, _Del>> 333 operator=(unique_ptr<_Yp, _Del>&& __r) 334 { 335 this->__shared_ptr<_Tp>::operator=(std::move(__r)); 336 return *this; 337 } 338 339 private: 340 // This constructor is non-standard, it is used by allocate_shared. 341 template<typename _Alloc, typename... _Args> 342 shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a, 343 _Args&&... __args) 344 : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...) 345 { } 346 347 template<typename _Yp, typename _Alloc, typename... _Args> 348 friend shared_ptr<_Yp> 349 allocate_shared(const _Alloc& __a, _Args&&... __args); 350 351 // This constructor is non-standard, it is used by weak_ptr::lock(). 352 shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t) 353 : __shared_ptr<_Tp>(__r, std::nothrow) { } 354 355 friend class weak_ptr<_Tp>; 356 }; 357 358 #if __cpp_deduction_guides >= 201606 359 template<typename _Tp> 360 shared_ptr(weak_ptr<_Tp>) -> shared_ptr<_Tp>; 361 template<typename _Tp, typename _Del> 362 shared_ptr(unique_ptr<_Tp, _Del>) -> shared_ptr<_Tp>; 363 #endif 364 365 // 20.7.2.2.7 shared_ptr comparisons 366 template<typename _Tp, typename _Up> 367 inline bool 368 operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept 369 { return __a.get() == __b.get(); } 370 371 template<typename _Tp> 372 inline bool 373 operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 374 { return !__a; } 375 376 template<typename _Tp> 377 inline bool 378 operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 379 { return !__a; } 380 381 template<typename _Tp, typename _Up> 382 inline bool 383 operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept 384 { return __a.get() != __b.get(); } 385 386 template<typename _Tp> 387 inline bool 388 operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 389 { return (bool)__a; } 390 391 template<typename _Tp> 392 inline bool 393 operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 394 { return (bool)__a; } 395 396 template<typename _Tp, typename _Up> 397 inline bool 398 operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept 399 { 400 using _Tp_elt = typename shared_ptr<_Tp>::element_type; 401 using _Up_elt = typename shared_ptr<_Up>::element_type; 402 using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type; 403 return less<_Vp>()(__a.get(), __b.get()); 404 } 405 406 template<typename _Tp> 407 inline bool 408 operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 409 { 410 using _Tp_elt = typename shared_ptr<_Tp>::element_type; 411 return less<_Tp_elt*>()(__a.get(), nullptr); 412 } 413 414 template<typename _Tp> 415 inline bool 416 operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 417 { 418 using _Tp_elt = typename shared_ptr<_Tp>::element_type; 419 return less<_Tp_elt*>()(nullptr, __a.get()); 420 } 421 422 template<typename _Tp, typename _Up> 423 inline bool 424 operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept 425 { return !(__b < __a); } 426 427 template<typename _Tp> 428 inline bool 429 operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 430 { return !(nullptr < __a); } 431 432 template<typename _Tp> 433 inline bool 434 operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 435 { return !(__a < nullptr); } 436 437 template<typename _Tp, typename _Up> 438 inline bool 439 operator>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept 440 { return (__b < __a); } 441 442 template<typename _Tp> 443 inline bool 444 operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 445 { return nullptr < __a; } 446 447 template<typename _Tp> 448 inline bool 449 operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 450 { return __a < nullptr; } 451 452 template<typename _Tp, typename _Up> 453 inline bool 454 operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept 455 { return !(__a < __b); } 456 457 template<typename _Tp> 458 inline bool 459 operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept 460 { return !(__a < nullptr); } 461 462 template<typename _Tp> 463 inline bool 464 operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept 465 { return !(nullptr < __a); } 466 467 template<typename _Tp> 468 struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>> 469 { }; 470 471 // 20.7.2.2.8 shared_ptr specialized algorithms. 472 template<typename _Tp> 473 inline void 474 swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept 475 { __a.swap(__b); } 476 477 // 20.7.2.2.9 shared_ptr casts. 478 template<typename _Tp, typename _Up> 479 inline shared_ptr<_Tp> 480 static_pointer_cast(const shared_ptr<_Up>& __r) noexcept 481 { 482 using _Sp = shared_ptr<_Tp>; 483 return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get())); 484 } 485 486 template<typename _Tp, typename _Up> 487 inline shared_ptr<_Tp> 488 const_pointer_cast(const shared_ptr<_Up>& __r) noexcept 489 { 490 using _Sp = shared_ptr<_Tp>; 491 return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get())); 492 } 493 494 template<typename _Tp, typename _Up> 495 inline shared_ptr<_Tp> 496 dynamic_pointer_cast(const shared_ptr<_Up>& __r) noexcept 497 { 498 using _Sp = shared_ptr<_Tp>; 499 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get())) 500 return _Sp(__r, __p); 501 return _Sp(); 502 } 503 504 #if __cplusplus > 201402L 505 template<typename _Tp, typename _Up> 506 inline shared_ptr<_Tp> 507 reinterpret_pointer_cast(const shared_ptr<_Up>& __r) noexcept 508 { 509 using _Sp = shared_ptr<_Tp>; 510 return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get())); 511 } 512 #endif 513 514 /** 515 * @brief A smart pointer with weak semantics. 516 * 517 * With forwarding constructors and assignment operators. 518 */ 519 template<typename _Tp> 520 class weak_ptr : public __weak_ptr<_Tp> 521 { 522 template<typename _Arg> 523 using _Constructible = typename enable_if< 524 is_constructible<__weak_ptr<_Tp>, _Arg>::value 525 >::type; 526 527 template<typename _Arg> 528 using _Assignable = typename enable_if< 529 is_assignable<__weak_ptr<_Tp>&, _Arg>::value, weak_ptr& 530 >::type; 531 532 public: 533 constexpr weak_ptr() noexcept = default; 534 535 template<typename _Yp, 536 typename = _Constructible<const shared_ptr<_Yp>&>> 537 weak_ptr(const shared_ptr<_Yp>& __r) noexcept 538 : __weak_ptr<_Tp>(__r) { } 539 540 weak_ptr(const weak_ptr&) noexcept = default; 541 542 template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>> 543 weak_ptr(const weak_ptr<_Yp>& __r) noexcept 544 : __weak_ptr<_Tp>(__r) { } 545 546 weak_ptr(weak_ptr&&) noexcept = default; 547 548 template<typename _Yp, typename = _Constructible<weak_ptr<_Yp>>> 549 weak_ptr(weak_ptr<_Yp>&& __r) noexcept 550 : __weak_ptr<_Tp>(std::move(__r)) { } 551 552 weak_ptr& 553 operator=(const weak_ptr& __r) noexcept = default; 554 555 template<typename _Yp> 556 _Assignable<const weak_ptr<_Yp>&> 557 operator=(const weak_ptr<_Yp>& __r) noexcept 558 { 559 this->__weak_ptr<_Tp>::operator=(__r); 560 return *this; 561 } 562 563 template<typename _Yp> 564 _Assignable<const shared_ptr<_Yp>&> 565 operator=(const shared_ptr<_Yp>& __r) noexcept 566 { 567 this->__weak_ptr<_Tp>::operator=(__r); 568 return *this; 569 } 570 571 weak_ptr& 572 operator=(weak_ptr&& __r) noexcept = default; 573 574 template<typename _Yp> 575 _Assignable<weak_ptr<_Yp>> 576 operator=(weak_ptr<_Yp>&& __r) noexcept 577 { 578 this->__weak_ptr<_Tp>::operator=(std::move(__r)); 579 return *this; 580 } 581 582 shared_ptr<_Tp> 583 lock() const noexcept 584 { return shared_ptr<_Tp>(*this, std::nothrow); } 585 }; 586 587 #if __cpp_deduction_guides >= 201606 588 template<typename _Tp> 589 weak_ptr(shared_ptr<_Tp>) -> weak_ptr<_Tp>; 590 #endif 591 592 // 20.7.2.3.6 weak_ptr specialized algorithms. 593 template<typename _Tp> 594 inline void 595 swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept 596 { __a.swap(__b); } 597 598 599 /// Primary template owner_less 600 template<typename _Tp = void> 601 struct owner_less; 602 603 /// Void specialization of owner_less 604 template<> 605 struct owner_less<void> : _Sp_owner_less<void, void> 606 { }; 607 608 /// Partial specialization of owner_less for shared_ptr. 609 template<typename _Tp> 610 struct owner_less<shared_ptr<_Tp>> 611 : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>> 612 { }; 613 614 /// Partial specialization of owner_less for weak_ptr. 615 template<typename _Tp> 616 struct owner_less<weak_ptr<_Tp>> 617 : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>> 618 { }; 619 620 /** 621 * @brief Base class allowing use of member function shared_from_this. 622 */ 623 template<typename _Tp> 624 class enable_shared_from_this 625 { 626 protected: 627 constexpr enable_shared_from_this() noexcept { } 628 629 enable_shared_from_this(const enable_shared_from_this&) noexcept { } 630 631 enable_shared_from_this& 632 operator=(const enable_shared_from_this&) noexcept 633 { return *this; } 634 635 ~enable_shared_from_this() { } 636 637 public: 638 shared_ptr<_Tp> 639 shared_from_this() 640 { return shared_ptr<_Tp>(this->_M_weak_this); } 641 642 shared_ptr<const _Tp> 643 shared_from_this() const 644 { return shared_ptr<const _Tp>(this->_M_weak_this); } 645 646 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11 647 #define __cpp_lib_enable_shared_from_this 201603 648 weak_ptr<_Tp> 649 weak_from_this() noexcept 650 { return this->_M_weak_this; } 651 652 weak_ptr<const _Tp> 653 weak_from_this() const noexcept 654 { return this->_M_weak_this; } 655 #endif 656 657 private: 658 template<typename _Tp1> 659 void 660 _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept 661 { _M_weak_this._M_assign(__p, __n); } 662 663 // Found by ADL when this is an associated class. 664 friend const enable_shared_from_this* 665 __enable_shared_from_this_base(const __shared_count<>&, 666 const enable_shared_from_this* __p) 667 { return __p; } 668 669 template<typename, _Lock_policy> 670 friend class __shared_ptr; 671 672 mutable weak_ptr<_Tp> _M_weak_this; 673 }; 674 675 /** 676 * @brief Create an object that is owned by a shared_ptr. 677 * @param __a An allocator. 678 * @param __args Arguments for the @a _Tp object's constructor. 679 * @return A shared_ptr that owns the newly created object. 680 * @throw An exception thrown from @a _Alloc::allocate or from the 681 * constructor of @a _Tp. 682 * 683 * A copy of @a __a will be used to allocate memory for the shared_ptr 684 * and the new object. 685 */ 686 template<typename _Tp, typename _Alloc, typename... _Args> 687 inline shared_ptr<_Tp> 688 allocate_shared(const _Alloc& __a, _Args&&... __args) 689 { 690 return shared_ptr<_Tp>(_Sp_make_shared_tag(), __a, 691 std::forward<_Args>(__args)...); 692 } 693 694 /** 695 * @brief Create an object that is owned by a shared_ptr. 696 * @param __args Arguments for the @a _Tp object's constructor. 697 * @return A shared_ptr that owns the newly created object. 698 * @throw std::bad_alloc, or an exception thrown from the 699 * constructor of @a _Tp. 700 */ 701 template<typename _Tp, typename... _Args> 702 inline shared_ptr<_Tp> 703 make_shared(_Args&&... __args) 704 { 705 typedef typename std::remove_const<_Tp>::type _Tp_nc; 706 return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(), 707 std::forward<_Args>(__args)...); 708 } 709 710 /// std::hash specialization for shared_ptr. 711 template<typename _Tp> 712 struct hash<shared_ptr<_Tp>> 713 : public __hash_base<size_t, shared_ptr<_Tp>> 714 { 715 size_t 716 operator()(const shared_ptr<_Tp>& __s) const noexcept 717 { 718 return std::hash<typename shared_ptr<_Tp>::element_type*>()(__s.get()); 719 } 720 }; 721 722 // @} group pointer_abstractions 723 724 _GLIBCXX_END_NAMESPACE_VERSION 725 } // namespace 726 727 #endif // _SHARED_PTR_H 728