libstdc++-v3/include/bits/shared_ptr_base.h

   1 // shared_ptr and weak_ptr implementation details -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009 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  *  You should not attempt to use it directly.
  47  */
  48
  49 #ifndef _SHARED_PTR_BASE_H
  50 #define _SHARED_PTR_BASE_H 1
  51
  52 _GLIBCXX_BEGIN_NAMESPACE(std)
  53
  54   // Forward declarations.
  55   template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
  56     class __shared_ptr;
  57
  58   template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
  59     class __weak_ptr;
  60
  61   template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
  62     class __enable_shared_from_this;
  63
  64   template<typename _Tp>
  65     class shared_ptr;
  66
  67   template<typename _Tp>
  68     class weak_ptr;
  69
  70   template<typename _Tp>
  71     struct owner_less;
  72
  73   template<typename _Tp>
  74     class enable_shared_from_this;
  75
  76   template<_Lock_policy _Lp = __default_lock_policy>
  77     class __weak_count;
  78
  79   template<_Lock_policy _Lp = __default_lock_policy>
  80     class __shared_count;
  81
  82
  83   // Counted ptr with no deleter or allocator support
  84   template<typename _Ptr, _Lock_policy _Lp>
  85     class _Sp_counted_ptr : public _Sp_counted_base<_Lp>
  86     {
  87     public:
  88       _Sp_counted_ptr(_Ptr __p)
  89       : _M_ptr(__p) { }
  90
  91       virtual void
  92       _M_dispose() // nothrow
  93       { delete _M_ptr; }
  94
  95       virtual void
  96       _M_destroy() // nothrow
  97       { delete this; }
  98
  99       virtual void*
 100       _M_get_deleter(const std::type_info& __ti)
 101       { return 0; }
 102
 103       _Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
 104       _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
 105
 106     protected:
 107       _Ptr             _M_ptr;  // copy constructor must not throw
 108     };
 109
 110   // Support for custom deleter and/or allocator
 111   template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
 112     class _Sp_counted_deleter : public _Sp_counted_ptr<_Ptr, _Lp>
 113     {
 114       typedef typename _Alloc::template
 115           rebind<_Sp_counted_deleter>::other _My_alloc_type;
 116
 117       // Helper class that stores the Deleter and also acts as an allocator.
 118       // Used to dispose of the owned pointer and the internal refcount
 119       // Requires that copies of _Alloc can free each other's memory.
 120       struct _My_Deleter
 121       : public _My_alloc_type    // copy constructor must not throw
 122       {
 123         _Deleter _M_del;         // copy constructor must not throw
 124         _My_Deleter(_Deleter __d, const _Alloc& __a)
 125           : _My_alloc_type(__a), _M_del(__d) { }
 126       };
 127
 128     protected:
 129       typedef _Sp_counted_ptr<_Ptr, _Lp> _Base_type;
 130
 131     public:
 132       // __d(__p) must not throw.
 133       _Sp_counted_deleter(_Ptr __p, _Deleter __d)
 134       : _Base_type(__p), _M_del(__d, _Alloc()) { }
 135
 136       // __d(__p) must not throw.
 137       _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a)
 138       : _Base_type(__p), _M_del(__d, __a) { }
 139
 140       virtual void
 141       _M_dispose() // nothrow
 142       { _M_del._M_del(_Base_type::_M_ptr); }
 143
 144       virtual void
 145       _M_destroy() // nothrow
 146       {
 147         _My_alloc_type __a(_M_del);
 148         this->~_Sp_counted_deleter();
 149         __a.deallocate(this, 1);
 150       }
 151
 152       virtual void*
 153       _M_get_deleter(const std::type_info& __ti)
 154       {
 155 #ifdef __GXX_RTTI
 156         return __ti == typeid(_Deleter) ? &_M_del._M_del : 0;
 157 #else
 158         return 0;
 159 #endif
 160       }
 161
 162     protected:
 163       _My_Deleter      _M_del;  // copy constructor must not throw
 164     };
 165
 166   // helpers for make_shared / allocate_shared
 167
 168   template<typename _Tp>
 169     struct _Sp_destroy_inplace
 170     {
 171       void operator()(_Tp* __p) const { if (__p) __p->~_Tp(); }
 172     };
 173
 174   struct _Sp_make_shared_tag { };
 175
 176   template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
 177     class _Sp_counted_ptr_inplace
 178     : public _Sp_counted_deleter<_Tp*, _Sp_destroy_inplace<_Tp>, _Alloc, _Lp>
 179     {
 180       typedef _Sp_counted_deleter<_Tp*, _Sp_destroy_inplace<_Tp>, _Alloc, _Lp>
 181         _Base_type;
 182
 183     public:
 184       _Sp_counted_ptr_inplace(_Alloc __a)
 185       : _Base_type(static_cast<_Tp*>(0), _Sp_destroy_inplace<_Tp>(), __a)
 186       , _M_storage()
 187       {
 188         void* __p = &_M_storage;
 189         ::new (__p) _Tp();  // might throw
 190         _Base_type::_Base_type::_M_ptr = static_cast<_Tp*>(__p);
 191       }
 192
 193       template<typename... _Args>
 194         _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
 195         : _Base_type(static_cast<_Tp*>(0), _Sp_destroy_inplace<_Tp>(), __a)
 196         , _M_storage()
 197         {
 198           void* __p = &_M_storage;
 199           ::new (__p) _Tp(std::forward<_Args>(__args)...);  // might throw
 200           _Base_type::_Base_type::_M_ptr = static_cast<_Tp*>(__p);
 201         }
 202
 203       // Override because the allocator needs to know the dynamic type
 204       virtual void
 205       _M_destroy() // nothrow
 206       {
 207         typedef typename _Alloc::template
 208             rebind<_Sp_counted_ptr_inplace>::other _My_alloc_type;
 209         _My_alloc_type __a(_Base_type::_M_del);
 210         this->~_Sp_counted_ptr_inplace();
 211         __a.deallocate(this, 1);
 212       }
 213
 214       // Sneaky trick so __shared_ptr can get the managed pointer
 215       virtual void*
 216       _M_get_deleter(const std::type_info& __ti)
 217       {
 218 #ifdef __GXX_RTTI
 219         return __ti == typeid(_Sp_make_shared_tag)
 220                ? static_cast<void*>(&_M_storage)
 221                : _Base_type::_M_get_deleter(__ti);
 222 #else
 223         return 0;
 224 #endif
 225       }
 226
 227     private:
 228       typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type
 229         _M_storage;
 230     };
 231
 232   template<_Lock_policy _Lp>
 233     class __shared_count
 234     {
 235     public:
 236       __shared_count() : _M_pi(0) // nothrow
 237       { }
 238
 239       template<typename _Ptr>
 240         __shared_count(_Ptr __p) : _M_pi(0)
 241         {
 242           __try
 243             {
 244               _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
 245             }
 246           __catch(...)
 247             {
 248               delete __p;
 249               __throw_exception_again;
 250             }
 251         }
 252
 253       template<typename _Ptr, typename _Deleter>
 254         __shared_count(_Ptr __p, _Deleter __d) : _M_pi(0)
 255         {
 256           // The allocator's value_type doesn't matter, will rebind it anyway.
 257           typedef std::allocator<int> _Alloc;
 258           typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
 259           typedef std::allocator<_Sp_cd_type> _Alloc2;
 260           _Alloc2 __a2;
 261           __try
 262             {
 263               _M_pi = __a2.allocate(1);
 264               ::new(static_cast<void*>(_M_pi)) _Sp_cd_type(__p, __d);
 265             }
 266           __catch(...)
 267             {
 268               __d(__p); // Call _Deleter on __p.
 269               if (_M_pi)
 270                 __a2.deallocate(static_cast<_Sp_cd_type*>(_M_pi), 1);
 271               __throw_exception_again;
 272             }
 273         }
 274
 275       template<typename _Ptr, typename _Deleter, typename _Alloc>
 276         __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
 277         {
 278           typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
 279           typedef typename _Alloc::template rebind<_Sp_cd_type>::other _Alloc2;
 280           _Alloc2 __a2(__a);
 281           __try
 282             {
 283               _M_pi = __a2.allocate(1);
 284               ::new(static_cast<void*>(_M_pi)) _Sp_cd_type(__p, __d, __a);
 285             }
 286           __catch(...)
 287             {
 288               __d(__p); // Call _Deleter on __p.
 289               if (_M_pi)
 290                 __a2.deallocate(static_cast<_Sp_cd_type*>(_M_pi), 1);
 291               __throw_exception_again;
 292             }
 293         }
 294
 295       template<typename _Tp, typename _Alloc, typename... _Args>
 296         __shared_count(_Sp_make_shared_tag, _Tp*, _Alloc __a, _Args&&... __args)
 297         : _M_pi(0)
 298         {
 299           typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
 300           typedef typename _Alloc::template rebind<_Sp_cp_type>::other _Alloc2;
 301           _Alloc2 __a2(__a);
 302           __try
 303             {
 304               _M_pi = __a2.allocate(1);
 305               ::new(static_cast<void*>(_M_pi)) _Sp_cp_type(__a,
 306                     std::forward<_Args>(__args)...);
 307             }
 308           __catch(...)
 309             {
 310               if (_M_pi)
 311                 __a2.deallocate(static_cast<_Sp_cp_type*>(_M_pi), 1);
 312               __throw_exception_again;
 313             }
 314         }
 315
 316 #if _GLIBCXX_DEPRECATED
 317       // Special case for auto_ptr<_Tp> to provide the strong guarantee.
 318       template<typename _Tp>
 319         explicit __shared_count(std::auto_ptr<_Tp>&& __r)
 320         : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get()))
 321         { __r.release(); }
 322 #endif
 323
 324       // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
 325       template<typename _Tp, typename _Del>
 326         explicit __shared_count(std::unique_ptr<_Tp, _Del>&& __r)
 327         : _M_pi(_S_create_from_up(std::move(__r)))
 328         { __r.release(); }
 329
 330       // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
 331       explicit __shared_count(const __weak_count<_Lp>& __r);
 332
 333       ~__shared_count() // nothrow
 334       {
 335         if (_M_pi != 0)
 336           _M_pi->_M_release();
 337       }
 338
 339       __shared_count(const __shared_count& __r)
 340       : _M_pi(__r._M_pi) // nothrow
 341       {
 342         if (_M_pi != 0)
 343           _M_pi->_M_add_ref_copy();
 344       }
 345
 346       __shared_count&
 347       operator=(const __shared_count& __r) // nothrow
 348       {
 349         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 350         if (__tmp != _M_pi)
 351           {
 352             if (__tmp != 0)
 353               __tmp->_M_add_ref_copy();
 354             if (_M_pi != 0)
 355               _M_pi->_M_release();
 356             _M_pi = __tmp;
 357           }
 358         return *this;
 359       }
 360
 361       void
 362       _M_swap(__shared_count& __r) // nothrow
 363       {
 364         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 365         __r._M_pi = _M_pi;
 366         _M_pi = __tmp;
 367       }
 368
 369       long
 370       _M_get_use_count() const // nothrow
 371       { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
 372
 373       bool
 374       _M_unique() const // nothrow
 375       { return this->_M_get_use_count() == 1; }
 376
 377       void*
 378       _M_get_deleter(const std::type_info& __ti) const
 379       { return _M_pi ? _M_pi->_M_get_deleter(__ti) : 0; }
 380
 381       bool
 382       _M_less(const __shared_count& __rhs) const
 383       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 384
 385       bool
 386       _M_less(const __weak_count<_Lp>& __rhs) const
 387       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 388
 389       // Friend function injected into enclosing namespace and found by ADL
 390       friend inline bool
 391       operator==(const __shared_count& __a, const __shared_count& __b)
 392       { return __a._M_pi == __b._M_pi; }
 393
 394     private:
 395       friend class __weak_count<_Lp>;
 396
 397       template<typename _Tp, typename _Del>
 398         static _Sp_counted_base<_Lp>*
 399         _S_create_from_up(std::unique_ptr<_Tp, _Del>&& __r,
 400           typename std::enable_if<!std::is_reference<_Del>::value>::type* = 0)
 401         {
 402           return new _Sp_counted_deleter<_Tp*, _Del, std::allocator<_Tp>,
 403             _Lp>(__r.get(), __r.get_deleter());
 404         }
 405
 406       template<typename _Tp, typename _Del>
 407         static _Sp_counted_base<_Lp>*
 408         _S_create_from_up(std::unique_ptr<_Tp, _Del>&& __r,
 409           typename std::enable_if<std::is_reference<_Del>::value>::type* = 0)
 410         {
 411           typedef typename std::remove_reference<_Del>::type _Del1;
 412           typedef std::reference_wrapper<_Del1> _Del2;
 413           return new _Sp_counted_deleter<_Tp*, _Del2, std::allocator<_Tp>,
 414             _Lp>(__r.get(), std::ref(__r.get_deleter()));
 415         }
 416
 417       _Sp_counted_base<_Lp>*  _M_pi;
 418     };
 419
 420
 421   template<_Lock_policy _Lp>
 422     class __weak_count
 423     {
 424     public:
 425       __weak_count() : _M_pi(0) // nothrow
 426       { }
 427
 428       __weak_count(const __shared_count<_Lp>& __r) : _M_pi(__r._M_pi) // nothrow
 429       {
 430         if (_M_pi != 0)
 431           _M_pi->_M_weak_add_ref();
 432       }
 433
 434       __weak_count(const __weak_count<_Lp>& __r) : _M_pi(__r._M_pi) // nothrow
 435       {
 436         if (_M_pi != 0)
 437           _M_pi->_M_weak_add_ref();
 438       }
 439
 440       ~__weak_count() // nothrow
 441       {
 442         if (_M_pi != 0)
 443           _M_pi->_M_weak_release();
 444       }
 445
 446       __weak_count<_Lp>&
 447       operator=(const __shared_count<_Lp>& __r) // nothrow
 448       {
 449         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 450         if (__tmp != 0)
 451           __tmp->_M_weak_add_ref();
 452         if (_M_pi != 0)
 453           _M_pi->_M_weak_release();
 454         _M_pi = __tmp;
 455         return *this;
 456       }
 457
 458       __weak_count<_Lp>&
 459       operator=(const __weak_count<_Lp>& __r) // nothrow
 460       {
 461         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 462         if (__tmp != 0)
 463           __tmp->_M_weak_add_ref();
 464         if (_M_pi != 0)
 465           _M_pi->_M_weak_release();
 466         _M_pi = __tmp;
 467         return *this;
 468       }
 469
 470       void
 471       _M_swap(__weak_count<_Lp>& __r) // nothrow
 472       {
 473         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 474         __r._M_pi = _M_pi;
 475         _M_pi = __tmp;
 476       }
 477
 478       long
 479       _M_get_use_count() const // nothrow
 480       { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
 481
 482       bool
 483       _M_less(const __weak_count& __rhs) const
 484       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 485
 486       bool
 487       _M_less(const __shared_count<_Lp>& __rhs) const
 488       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 489
 490       // Friend function injected into enclosing namespace and found by ADL
 491       friend inline bool
 492       operator==(const __weak_count& __a, const __weak_count& __b)
 493       { return __a._M_pi == __b._M_pi; }
 494
 495     private:
 496       friend class __shared_count<_Lp>;
 497
 498       _Sp_counted_base<_Lp>*  _M_pi;
 499     };
 500
 501   // Now that __weak_count is defined we can define this constructor:
 502   template<_Lock_policy _Lp>
 503     inline __shared_count<_Lp>:: __shared_count(const __weak_count<_Lp>& __r)
 504     : _M_pi(__r._M_pi)
 505     {
 506       if (_M_pi != 0)
 507         _M_pi->_M_add_ref_lock();
 508       else
 509         __throw_bad_weak_ptr();
 510     }
 511
 512
 513   // Support for enable_shared_from_this.
 514
 515   // Friend of __enable_shared_from_this.
 516   template<_Lock_policy _Lp, typename _Tp1, typename _Tp2>
 517     void
 518     __enable_shared_from_this_helper(const __shared_count<_Lp>&,
 519                                      const __enable_shared_from_this<_Tp1,
 520                                      _Lp>*, const _Tp2*);
 521
 522   // Friend of enable_shared_from_this.
 523   template<typename _Tp1, typename _Tp2>
 524     void
 525     __enable_shared_from_this_helper(const __shared_count<>&,
 526                                      const enable_shared_from_this<_Tp1>*,
 527                                      const _Tp2*);
 528
 529   template<_Lock_policy _Lp>
 530     inline void
 531     __enable_shared_from_this_helper(const __shared_count<_Lp>&, ...)
 532     { }
 533
 534
 535   template<typename _Tp, _Lock_policy _Lp>
 536     class __shared_ptr
 537     {
 538     public:
 539       typedef _Tp   element_type;
 540
 541       __shared_ptr() : _M_ptr(0), _M_refcount() // never throws
 542       { }
 543
 544       template<typename _Tp1>
 545         explicit __shared_ptr(_Tp1* __p) : _M_ptr(__p), _M_refcount(__p)
 546         {
 547           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 548           // __glibcxx_function_requires(_CompleteConcept<_Tp1*>)
 549           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 550         }
 551
 552       template<typename _Tp1, typename _Deleter>
 553         __shared_ptr(_Tp1* __p, _Deleter __d)
 554         : _M_ptr(__p), _M_refcount(__p, __d)
 555         {
 556           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 557           // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
 558           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 559         }
 560
 561       template<typename _Tp1, typename _Deleter, typename _Alloc>
 562         __shared_ptr(_Tp1* __p, _Deleter __d, const _Alloc& __a)
 563         : _M_ptr(__p), _M_refcount(__p, __d, __a)
 564         {
 565           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 566           // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
 567           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 568         }
 569
 570       template<typename _Tp1>
 571         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, _Tp* __p)
 572         : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
 573         { }
 574
 575       //  generated copy constructor, assignment, destructor are fine.
 576
 577       template<typename _Tp1>
 578         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r)
 579         : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 580         { __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) }
 581
 582       __shared_ptr(__shared_ptr&& __r)
 583       : _M_ptr(__r._M_ptr), _M_refcount() // never throws
 584       {
 585         _M_refcount._M_swap(__r._M_refcount);
 586         __r._M_ptr = 0;
 587       }
 588
 589       template<typename _Tp1>
 590         __shared_ptr(__shared_ptr<_Tp1, _Lp>&& __r)
 591         : _M_ptr(__r._M_ptr), _M_refcount() // never throws
 592         {
 593           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 594           _M_refcount._M_swap(__r._M_refcount);
 595           __r._M_ptr = 0;
 596         }
 597
 598       template<typename _Tp1>
 599         explicit __shared_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 600         : _M_refcount(__r._M_refcount) // may throw
 601         {
 602           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 603
 604           // It is now safe to copy __r._M_ptr, as
 605           // _M_refcount(__r._M_refcount) did not throw.
 606           _M_ptr = __r._M_ptr;
 607         }
 608
 609       template<typename _Tp1, typename _Del>
 610         explicit __shared_ptr(const std::unique_ptr<_Tp1, _Del>&) = delete;
 611
 612       // If an exception is thrown this constructor has no effect.
 613       template<typename _Tp1, typename _Del>
 614         explicit __shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
 615         : _M_ptr(__r.get()), _M_refcount()
 616         {
 617           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 618           _Tp1* __tmp = __r.get();
 619           _M_refcount = __shared_count<_Lp>(std::move(__r));
 620           __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
 621         }
 622
 623 #if _GLIBCXX_DEPRECATED
 624       // Postcondition: use_count() == 1 and __r.get() == 0
 625       template<typename _Tp1>
 626         explicit __shared_ptr(std::auto_ptr<_Tp1>&& __r)
 627         : _M_ptr(__r.get()), _M_refcount()
 628         {
 629           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 630           // TODO requires _Tp1 is complete, delete __r.release() well-formed
 631           _Tp1* __tmp = __r.get();
 632           _M_refcount = __shared_count<_Lp>(std::move(__r));
 633           __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
 634         }
 635 #endif
 636
 637       template<typename _Tp1>
 638         __shared_ptr&
 639         operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws
 640         {
 641           _M_ptr = __r._M_ptr;
 642           _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
 643           return *this;
 644         }
 645
 646 #if _GLIBCXX_DEPRECATED
 647       template<typename _Tp1>
 648         __shared_ptr&
 649         operator=(std::auto_ptr<_Tp1>&& __r)
 650         {
 651           __shared_ptr(std::move(__r)).swap(*this);
 652           return *this;
 653         }
 654 #endif
 655
 656       __shared_ptr&
 657       operator=(__shared_ptr&& __r)
 658       {
 659         __shared_ptr(std::move(__r)).swap(*this);
 660         return *this;
 661       }
 662
 663       template<class _Tp1>
 664         __shared_ptr&
 665         operator=(__shared_ptr<_Tp1, _Lp>&& __r)
 666         {
 667           __shared_ptr(std::move(__r)).swap(*this);
 668           return *this;
 669         }
 670
 671       template<typename _Tp1, typename _Del>
 672         __shared_ptr&
 673         operator=(const std::unique_ptr<_Tp1, _Del>& __r) = delete;
 674
 675       template<typename _Tp1, typename _Del>
 676         __shared_ptr&
 677         operator=(std::unique_ptr<_Tp1, _Del>&& __r)
 678         {
 679           __shared_ptr(std::move(__r)).swap(*this);
 680           return *this;
 681         }
 682
 683       void
 684       reset() // never throws
 685       { __shared_ptr().swap(*this); }
 686
 687       template<typename _Tp1>
 688         void
 689         reset(_Tp1* __p) // _Tp1 must be complete.
 690         {
 691           // Catch self-reset errors.
 692           _GLIBCXX_DEBUG_ASSERT(__p == 0 || __p != _M_ptr);
 693           __shared_ptr(__p).swap(*this);
 694         }
 695
 696       template<typename _Tp1, typename _Deleter>
 697         void
 698         reset(_Tp1* __p, _Deleter __d)
 699         { __shared_ptr(__p, __d).swap(*this); }
 700
 701       template<typename _Tp1, typename _Deleter, typename _Alloc>
 702         void
 703         reset(_Tp1* __p, _Deleter __d, const _Alloc& __a)
 704         { __shared_ptr(__p, __d, __a).swap(*this); }
 705
 706       // Allow class instantiation when _Tp is [cv-qual] void.
 707       typename std::add_lvalue_reference<_Tp>::type
 708       operator*() const // never throws
 709       {
 710         _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
 711         return *_M_ptr;
 712       }
 713
 714       _Tp*
 715       operator->() const // never throws
 716       {
 717         _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
 718         return _M_ptr;
 719       }
 720
 721       _Tp*
 722       get() const // never throws
 723       { return _M_ptr; }
 724
 725       explicit operator bool() const // never throws
 726       { return _M_ptr == 0 ? false : true; }
 727
 728       bool
 729       unique() const // never throws
 730       { return _M_refcount._M_unique(); }
 731
 732       long
 733       use_count() const // never throws
 734       { return _M_refcount._M_get_use_count(); }
 735
 736       void
 737       swap(__shared_ptr<_Tp, _Lp>& __other) // never throws
 738       {
 739         std::swap(_M_ptr, __other._M_ptr);
 740         _M_refcount._M_swap(__other._M_refcount);
 741       }
 742
 743       template<typename _Tp1>
 744         bool
 745         owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const
 746         { return _M_refcount._M_less(__rhs._M_refcount); }
 747
 748       template<typename _Tp1>
 749         bool
 750         owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const
 751         { return _M_refcount._M_less(__rhs._M_refcount); }
 752
 753 #ifdef __GXX_RTTI
 754     protected:
 755       // This constructor is non-standard, it is used by allocate_shared.
 756       template<typename _Alloc, typename... _Args>
 757         __shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
 758         : _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a,
 759                                 std::forward<_Args>(__args)...)
 760         {
 761           // _M_ptr needs to point to the newly constructed object.
 762           // This relies on _Sp_counted_ptr_inplace::_M_get_deleter.
 763           void* __p = _M_refcount._M_get_deleter(typeid(__tag));
 764           _M_ptr = static_cast<_Tp*>(__p);
 765           __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
 766         }
 767 #else
 768       template<typename _Alloc>
 769         struct _Deleter
 770         {
 771           void operator()(_Tp* __ptr)
 772           {
 773             _M_alloc.destroy(__ptr);
 774             _M_alloc.deallocate(__ptr, 1);
 775           }
 776           _Alloc _M_alloc;
 777         };
 778
 779       template<typename _Alloc, typename... _Args>
 780         __shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
 781         : _M_ptr(), _M_refcount()
 782         {
 783           typedef typename _Alloc::template rebind<_Tp>::other _Alloc2;
 784           _Deleter<_Alloc2> __del = { _Alloc2(__a) };
 785           _M_ptr = __del._M_alloc.allocate(1);
 786           __try
 787             {
 788               __del._M_alloc.construct(_M_ptr, std::forward<_Args>(__args)...);
 789             }
 790           __catch(...)
 791             {
 792               __del._M_alloc.deallocate(_M_ptr, 1);
 793               __throw_exception_again;
 794             }
 795           __shared_count<_Lp> __count(_M_ptr, __del, __del._M_alloc);
 796           _M_refcount._M_swap(__count);
 797           __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
 798         }
 799 #endif
 800
 801       template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
 802                typename... _Args>
 803         friend __shared_ptr<_Tp1, _Lp1>
 804         __allocate_shared(_Alloc __a, _Args&&... __args);
 805
 806     private:
 807       void*
 808       _M_get_deleter(const std::type_info& __ti) const
 809       { return _M_refcount._M_get_deleter(__ti); }
 810
 811       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
 812       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
 813
 814       template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
 815         friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&);
 816
 817       _Tp*                 _M_ptr;         // Contained pointer.
 818       __shared_count<_Lp>  _M_refcount;    // Reference counter.
 819     };
 820
 821
 822   // 20.8.13.2.7 shared_ptr comparisons
 823   template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
 824     inline bool
 825     operator==(const __shared_ptr<_Tp1, _Lp>& __a,
 826                const __shared_ptr<_Tp2, _Lp>& __b)
 827     { return __a.get() == __b.get(); }
 828
 829   template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
 830     inline bool
 831     operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
 832                const __shared_ptr<_Tp2, _Lp>& __b)
 833     { return __a.get() != __b.get(); }
 834
 835   template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
 836     inline bool
 837     operator<(const __shared_ptr<_Tp1, _Lp>& __a,
 838               const __shared_ptr<_Tp2, _Lp>& __b)
 839     { return __a.get() < __b.get(); }
 840
 841   template<typename _Sp>
 842     struct _Sp_less : public binary_function<_Sp, _Sp, bool>
 843     {
 844       bool
 845       operator()(const _Sp& __lhs, const _Sp& __rhs) const
 846       {
 847         typedef typename _Sp::element_type element_type;
 848         return std::less<element_type*>()(__lhs.get(), __rhs.get());
 849       }
 850     };
 851
 852   template<typename _Tp, _Lock_policy _Lp>
 853     struct less<__shared_ptr<_Tp, _Lp>>
 854     : public _Sp_less<__shared_ptr<_Tp, _Lp>>
 855     { };
 856
 857   // XXX LessThanComparable<_Tp> concept should provide >, >= and <=
 858   template<typename _Tp, _Lock_policy _Lp>
 859     inline bool
 860     operator>(const __shared_ptr<_Tp, _Lp>& __a,
 861               const __shared_ptr<_Tp, _Lp>& __b)
 862     { return __a.get() > __b.get(); }
 863
 864   template<typename _Tp, _Lock_policy _Lp>
 865     inline bool
 866     operator>=(const __shared_ptr<_Tp, _Lp>& __a,
 867                const __shared_ptr<_Tp, _Lp>& __b)
 868     { return __a.get() >= __b.get(); }
 869
 870   template<typename _Tp, _Lock_policy _Lp>
 871     inline bool
 872     operator<=(const __shared_ptr<_Tp, _Lp>& __a,
 873                const __shared_ptr<_Tp, _Lp>& __b)
 874     { return __a.get() <= __b.get(); }
 875
 876   // 2.2.3.8 shared_ptr specialized algorithms.
 877   template<typename _Tp, _Lock_policy _Lp>
 878     inline void
 879     swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b)
 880     { __a.swap(__b); }
 881
 882   // 2.2.3.9 shared_ptr casts
 883
 884   // The seemingly equivalent code:
 885   // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
 886   // will eventually result in undefined behaviour, attempting to
 887   // delete the same object twice.
 888   /// static_pointer_cast
 889   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 890     inline __shared_ptr<_Tp, _Lp>
 891     static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 892     { return __shared_ptr<_Tp, _Lp>(__r, static_cast<_Tp*>(__r.get())); }
 893
 894   // The seemingly equivalent code:
 895   // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
 896   // will eventually result in undefined behaviour, attempting to
 897   // delete the same object twice.
 898   /// const_pointer_cast
 899   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 900     inline __shared_ptr<_Tp, _Lp>
 901     const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 902     { return __shared_ptr<_Tp, _Lp>(__r, const_cast<_Tp*>(__r.get())); }
 903
 904   // The seemingly equivalent code:
 905   // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
 906   // will eventually result in undefined behaviour, attempting to
 907   // delete the same object twice.
 908   /// dynamic_pointer_cast
 909   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 910     inline __shared_ptr<_Tp, _Lp>
 911     dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 912     {
 913       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
 914         return __shared_ptr<_Tp, _Lp>(__r, __p);
 915       return __shared_ptr<_Tp, _Lp>();
 916     }
 917
 918
 919   template<typename _Tp, _Lock_policy _Lp>
 920     class __weak_ptr
 921     {
 922     public:
 923       typedef _Tp element_type;
 924
 925       __weak_ptr() : _M_ptr(0), _M_refcount() // never throws
 926       { }
 927
 928       // Generated copy constructor, assignment, destructor are fine.
 929
 930       // The "obvious" converting constructor implementation:
 931       //
 932       //  template<typename _Tp1>
 933       //    __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 934       //    : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 935       //    { }
 936       //
 937       // has a serious problem.
 938       //
 939       //  __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
 940       //  conversion may require access to *__r._M_ptr (virtual inheritance).
 941       //
 942       // It is not possible to avoid spurious access violations since
 943       // in multithreaded programs __r._M_ptr may be invalidated at any point.
 944       template<typename _Tp1>
 945         __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 946         : _M_refcount(__r._M_refcount) // never throws
 947         {
 948           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 949           _M_ptr = __r.lock().get();
 950         }
 951
 952       template<typename _Tp1>
 953         __weak_ptr(const __shared_ptr<_Tp1, _Lp>& __r)
 954         : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 955         { __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) }
 956
 957       template<typename _Tp1>
 958         __weak_ptr&
 959         operator=(const __weak_ptr<_Tp1, _Lp>& __r) // never throws
 960         {
 961           _M_ptr = __r.lock().get();
 962           _M_refcount = __r._M_refcount;
 963           return *this;
 964         }
 965
 966       template<typename _Tp1>
 967         __weak_ptr&
 968         operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws
 969         {
 970           _M_ptr = __r._M_ptr;
 971           _M_refcount = __r._M_refcount;
 972           return *this;
 973         }
 974
 975       __shared_ptr<_Tp, _Lp>
 976       lock() const // never throws
 977       {
 978 #ifdef __GTHREADS
 979         // Optimization: avoid throw overhead.
 980         if (expired())
 981           return __shared_ptr<element_type, _Lp>();
 982
 983         __try
 984           {
 985             return __shared_ptr<element_type, _Lp>(*this);
 986           }
 987         __catch(const bad_weak_ptr&)
 988           {
 989             // Q: How can we get here?
 990             // A: Another thread may have invalidated r after the
 991             //    use_count test above.
 992             return __shared_ptr<element_type, _Lp>();
 993           }
 994
 995 #else
 996         // Optimization: avoid try/catch overhead when single threaded.
 997         return expired() ? __shared_ptr<element_type, _Lp>()
 998                          : __shared_ptr<element_type, _Lp>(*this);
 999
1000 #endif
1001       } // XXX MT
1002
1003       long
1004       use_count() const // never throws
1005       { return _M_refcount._M_get_use_count(); }
1006
1007       bool
1008       expired() const // never throws
1009       { return _M_refcount._M_get_use_count() == 0; }
1010
1011       template<typename _Tp1>
1012         bool
1013         owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const
1014         { return _M_refcount._M_less(__rhs._M_refcount); }
1015
1016       template<typename _Tp1>
1017         bool
1018         owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const
1019         { return _M_refcount._M_less(__rhs._M_refcount); }
1020
1021       void
1022       reset() // never throws
1023       { __weak_ptr().swap(*this); }
1024
1025       void
1026       swap(__weak_ptr& __s) // never throws
1027       {
1028         std::swap(_M_ptr, __s._M_ptr);
1029         _M_refcount._M_swap(__s._M_refcount);
1030       }
1031
1032       // Comparisons
1033       template<typename _Tp1>
1034         bool operator<(const __weak_ptr<_Tp1, _Lp>&) const = delete;
1035
1036       template<typename _Tp1>
1037         bool operator<=(const __weak_ptr<_Tp1, _Lp>&) const = delete;
1038
1039       template<typename _Tp1>
1040         bool operator>(const __weak_ptr<_Tp1, _Lp>&) const = delete;
1041
1042       template<typename _Tp1>
1043         bool operator>=(const __weak_ptr<_Tp1, _Lp>&) const = delete;
1044
1045     private:
1046       // Used by __enable_shared_from_this.
1047       void
1048       _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount)
1049       {
1050         _M_ptr = __ptr;
1051         _M_refcount = __refcount;
1052       }
1053
1054       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1055       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1056       friend class __enable_shared_from_this<_Tp, _Lp>;
1057       friend class enable_shared_from_this<_Tp>;
1058
1059       _Tp*               _M_ptr;         // Contained pointer.
1060       __weak_count<_Lp>  _M_refcount;    // Reference counter.
1061     };
1062
1063   // 20.8.13.3.7 weak_ptr specialized algorithms.
1064   template<typename _Tp, _Lock_policy _Lp>
1065     inline void
1066     swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b)
1067     { __a.swap(__b); }
1068
1069   template<typename _Tp, typename _Tp1>
1070     struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
1071     {
1072       bool
1073       operator()(const _Tp& __lhs, const _Tp& __rhs) const
1074       { return __lhs.owner_before(__rhs); }
1075
1076       bool
1077       operator()(const _Tp& __lhs, const _Tp1& __rhs) const
1078       { return __lhs.owner_before(__rhs); }
1079
1080       bool
1081       operator()(const _Tp1& __lhs, const _Tp& __rhs) const
1082       { return __lhs.owner_before(__rhs); }
1083     };
1084
1085   template<typename _Tp, _Lock_policy _Lp>
1086     struct owner_less<__shared_ptr<_Tp, _Lp>>
1087     : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
1088     { };
1089
1090   template<typename _Tp, _Lock_policy _Lp>
1091     struct owner_less<__weak_ptr<_Tp, _Lp>>
1092     : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
1093     { };
1094
1095
1096   template<typename _Tp, _Lock_policy _Lp>
1097     class __enable_shared_from_this
1098     {
1099     protected:
1100       __enable_shared_from_this() { }
1101
1102       __enable_shared_from_this(const __enable_shared_from_this&) { }
1103
1104       __enable_shared_from_this&
1105       operator=(const __enable_shared_from_this&)
1106       { return *this; }
1107
1108       ~__enable_shared_from_this() { }
1109
1110     public:
1111       __shared_ptr<_Tp, _Lp>
1112       shared_from_this()
1113       { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
1114
1115       __shared_ptr<const _Tp, _Lp>
1116       shared_from_this() const
1117       { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
1118
1119     private:
1120       template<typename _Tp1>
1121         void
1122         _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const
1123         { _M_weak_this._M_assign(__p, __n); }
1124
1125       template<typename _Tp1>
1126         friend void
1127         __enable_shared_from_this_helper(const __shared_count<_Lp>& __pn,
1128                                          const __enable_shared_from_this* __pe,
1129                                          const _Tp1* __px)
1130         {
1131           if (__pe != 0)
1132             __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
1133         }
1134
1135       mutable __weak_ptr<_Tp, _Lp>  _M_weak_this;
1136     };
1137
1138
1139   template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
1140     inline __shared_ptr<_Tp, _Lp>
1141     __allocate_shared(_Alloc __a, _Args&&... __args)
1142     {
1143       return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(),
1144           std::forward<_Alloc>(__a), std::forward<_Args>(__args)...);
1145     }
1146
1147   template<typename _Tp, _Lock_policy _Lp, typename... _Args>
1148     inline __shared_ptr<_Tp, _Lp>
1149     __make_shared(_Args&&... __args)
1150     {
1151       typedef typename std::remove_const<_Tp>::type _Tp_nc;
1152       return __allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
1153                                          std::forward<_Args>(__args)...);
1154     }
1155
1156 _GLIBCXX_END_NAMESPACE
1157
1158 #endif // _SHARED_PTR_BASE_H