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

   1 // shared_ptr and weak_ptr implementation details -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010 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       explicit
  89       _Sp_counted_ptr(_Ptr __p)
  90       : _M_ptr(__p) { }
  91
  92       virtual void
  93       _M_dispose() // nothrow
  94       { delete _M_ptr; }
  95
  96       virtual void
  97       _M_destroy() // nothrow
  98       { delete this; }
  99
 100       virtual void*
 101       _M_get_deleter(const std::type_info&)
 102       { return 0; }
 103
 104       _Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
 105       _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
 106
 107     protected:
 108       _Ptr             _M_ptr;  // copy constructor must not throw
 109     };
 110
 111   template<>
 112     inline void
 113     _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() { }
 114
 115   template<>
 116     inline void
 117     _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() { }
 118
 119   template<>
 120     inline void
 121     _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() { }
 122
 123   // Support for custom deleter and/or allocator
 124   template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
 125     class _Sp_counted_deleter : public _Sp_counted_ptr<_Ptr, _Lp>
 126     {
 127       typedef typename _Alloc::template
 128           rebind<_Sp_counted_deleter>::other _My_alloc_type;
 129
 130       // Helper class that stores the Deleter and also acts as an allocator.
 131       // Used to dispose of the owned pointer and the internal refcount
 132       // Requires that copies of _Alloc can free each other's memory.
 133       struct _My_Deleter
 134       : public _My_alloc_type    // copy constructor must not throw
 135       {
 136         _Deleter _M_del;         // copy constructor must not throw
 137         _My_Deleter(_Deleter __d, const _Alloc& __a)
 138           : _My_alloc_type(__a), _M_del(__d) { }
 139       };
 140
 141     protected:
 142       typedef _Sp_counted_ptr<_Ptr, _Lp> _Base_type;
 143
 144     public:
 145       // __d(__p) must not throw.
 146       _Sp_counted_deleter(_Ptr __p, _Deleter __d)
 147       : _Base_type(__p), _M_del(__d, _Alloc()) { }
 148
 149       // __d(__p) must not throw.
 150       _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a)
 151       : _Base_type(__p), _M_del(__d, __a) { }
 152
 153       virtual void
 154       _M_dispose() // nothrow
 155       { _M_del._M_del(_Base_type::_M_ptr); }
 156
 157       virtual void
 158       _M_destroy() // nothrow
 159       {
 160         _My_alloc_type __a(_M_del);
 161         this->~_Sp_counted_deleter();
 162         __a.deallocate(this, 1);
 163       }
 164
 165       virtual void*
 166       _M_get_deleter(const std::type_info& __ti)
 167       {
 168 #ifdef __GXX_RTTI
 169         return __ti == typeid(_Deleter) ? &_M_del._M_del : 0;
 170 #else
 171         return 0;
 172 #endif
 173       }
 174
 175     protected:
 176       _My_Deleter      _M_del;  // copy constructor must not throw
 177     };
 178
 179   // helpers for make_shared / allocate_shared
 180
 181   template<typename _Tp>
 182     struct _Sp_destroy_inplace
 183     {
 184       void operator()(_Tp* __p) const { if (__p) __p->~_Tp(); }
 185     };
 186
 187   struct _Sp_make_shared_tag { };
 188
 189   template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
 190     class _Sp_counted_ptr_inplace
 191     : public _Sp_counted_deleter<_Tp*, _Sp_destroy_inplace<_Tp>, _Alloc, _Lp>
 192     {
 193       typedef _Sp_counted_deleter<_Tp*, _Sp_destroy_inplace<_Tp>, _Alloc, _Lp>
 194         _Base_type;
 195
 196     public:
 197       explicit
 198       _Sp_counted_ptr_inplace(_Alloc __a)
 199       : _Base_type(static_cast<_Tp*>(0), _Sp_destroy_inplace<_Tp>(), __a)
 200       , _M_storage()
 201       {
 202         void* __p = &_M_storage;
 203         ::new (__p) _Tp();  // might throw
 204         _Base_type::_Base_type::_M_ptr = static_cast<_Tp*>(__p);
 205       }
 206
 207       template<typename... _Args>
 208         _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
 209         : _Base_type(static_cast<_Tp*>(0), _Sp_destroy_inplace<_Tp>(), __a)
 210         , _M_storage()
 211         {
 212           void* __p = &_M_storage;
 213           ::new (__p) _Tp(std::forward<_Args>(__args)...);  // might throw
 214           _Base_type::_Base_type::_M_ptr = static_cast<_Tp*>(__p);
 215         }
 216
 217       // Override because the allocator needs to know the dynamic type
 218       virtual void
 219       _M_destroy() // nothrow
 220       {
 221         typedef typename _Alloc::template
 222             rebind<_Sp_counted_ptr_inplace>::other _My_alloc_type;
 223         _My_alloc_type __a(_Base_type::_M_del);
 224         this->~_Sp_counted_ptr_inplace();
 225         __a.deallocate(this, 1);
 226       }
 227
 228       // Sneaky trick so __shared_ptr can get the managed pointer
 229       virtual void*
 230       _M_get_deleter(const std::type_info& __ti)
 231       {
 232 #ifdef __GXX_RTTI
 233         return __ti == typeid(_Sp_make_shared_tag)
 234                ? static_cast<void*>(&_M_storage)
 235                : _Base_type::_M_get_deleter(__ti);
 236 #else
 237         return 0;
 238 #endif
 239       }
 240
 241     private:
 242       typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type
 243         _M_storage;
 244     };
 245
 246   template<_Lock_policy _Lp>
 247     class __shared_count
 248     {
 249     public:
 250       __shared_count() : _M_pi(0) // nothrow
 251       { }
 252
 253       template<typename _Ptr>
 254         explicit
 255         __shared_count(_Ptr __p) : _M_pi(0)
 256         {
 257           __try
 258             {
 259               _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
 260             }
 261           __catch(...)
 262             {
 263               delete __p;
 264               __throw_exception_again;
 265             }
 266         }
 267
 268       template<typename _Ptr, typename _Deleter>
 269         __shared_count(_Ptr __p, _Deleter __d) : _M_pi(0)
 270         {
 271           // The allocator's value_type doesn't matter, will rebind it anyway.
 272           typedef std::allocator<int> _Alloc;
 273           typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
 274           typedef std::allocator<_Sp_cd_type> _Alloc2;
 275           _Alloc2 __a2;
 276           __try
 277             {
 278               _M_pi = __a2.allocate(1);
 279               ::new(static_cast<void*>(_M_pi)) _Sp_cd_type(__p, __d);
 280             }
 281           __catch(...)
 282             {
 283               __d(__p); // Call _Deleter on __p.
 284               if (_M_pi)
 285                 __a2.deallocate(static_cast<_Sp_cd_type*>(_M_pi), 1);
 286               __throw_exception_again;
 287             }
 288         }
 289
 290       template<typename _Ptr, typename _Deleter, typename _Alloc>
 291         __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
 292         {
 293           typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
 294           typedef typename _Alloc::template rebind<_Sp_cd_type>::other _Alloc2;
 295           _Alloc2 __a2(__a);
 296           __try
 297             {
 298               _M_pi = __a2.allocate(1);
 299               ::new(static_cast<void*>(_M_pi)) _Sp_cd_type(__p, __d, __a);
 300             }
 301           __catch(...)
 302             {
 303               __d(__p); // Call _Deleter on __p.
 304               if (_M_pi)
 305                 __a2.deallocate(static_cast<_Sp_cd_type*>(_M_pi), 1);
 306               __throw_exception_again;
 307             }
 308         }
 309
 310       template<typename _Tp, typename _Alloc, typename... _Args>
 311         __shared_count(_Sp_make_shared_tag, _Tp*, _Alloc __a, _Args&&... __args)
 312         : _M_pi(0)
 313         {
 314           typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
 315           typedef typename _Alloc::template rebind<_Sp_cp_type>::other _Alloc2;
 316           _Alloc2 __a2(__a);
 317           __try
 318             {
 319               _M_pi = __a2.allocate(1);
 320               ::new(static_cast<void*>(_M_pi)) _Sp_cp_type(__a,
 321                     std::forward<_Args>(__args)...);
 322             }
 323           __catch(...)
 324             {
 325               if (_M_pi)
 326                 __a2.deallocate(static_cast<_Sp_cp_type*>(_M_pi), 1);
 327               __throw_exception_again;
 328             }
 329         }
 330
 331 #if _GLIBCXX_DEPRECATED
 332       // Special case for auto_ptr<_Tp> to provide the strong guarantee.
 333       template<typename _Tp>
 334         explicit
 335         __shared_count(std::auto_ptr<_Tp>&& __r)
 336         : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get()))
 337         { __r.release(); }
 338 #endif
 339
 340       // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
 341       template<typename _Tp, typename _Del>
 342         explicit
 343         __shared_count(std::unique_ptr<_Tp, _Del>&& __r)
 344         : _M_pi(_S_create_from_up(std::move(__r)))
 345         { __r.release(); }
 346
 347       // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
 348       explicit __shared_count(const __weak_count<_Lp>& __r);
 349
 350       ~__shared_count() // nothrow
 351       {
 352         if (_M_pi != 0)
 353           _M_pi->_M_release();
 354       }
 355
 356       __shared_count(const __shared_count& __r)
 357       : _M_pi(__r._M_pi) // nothrow
 358       {
 359         if (_M_pi != 0)
 360           _M_pi->_M_add_ref_copy();
 361       }
 362
 363       __shared_count&
 364       operator=(const __shared_count& __r) // nothrow
 365       {
 366         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 367         if (__tmp != _M_pi)
 368           {
 369             if (__tmp != 0)
 370               __tmp->_M_add_ref_copy();
 371             if (_M_pi != 0)
 372               _M_pi->_M_release();
 373             _M_pi = __tmp;
 374           }
 375         return *this;
 376       }
 377
 378       void
 379       _M_swap(__shared_count& __r) // nothrow
 380       {
 381         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 382         __r._M_pi = _M_pi;
 383         _M_pi = __tmp;
 384       }
 385
 386       long
 387       _M_get_use_count() const // nothrow
 388       { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
 389
 390       bool
 391       _M_unique() const // nothrow
 392       { return this->_M_get_use_count() == 1; }
 393
 394       void*
 395       _M_get_deleter(const std::type_info& __ti) const
 396       { return _M_pi ? _M_pi->_M_get_deleter(__ti) : 0; }
 397
 398       bool
 399       _M_less(const __shared_count& __rhs) const
 400       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 401
 402       bool
 403       _M_less(const __weak_count<_Lp>& __rhs) const
 404       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 405
 406       // Friend function injected into enclosing namespace and found by ADL
 407       friend inline bool
 408       operator==(const __shared_count& __a, const __shared_count& __b)
 409       { return __a._M_pi == __b._M_pi; }
 410
 411     private:
 412       friend class __weak_count<_Lp>;
 413
 414       template<typename _Tp, typename _Del>
 415         static _Sp_counted_base<_Lp>*
 416         _S_create_from_up(std::unique_ptr<_Tp, _Del>&& __r,
 417           typename std::enable_if<!std::is_reference<_Del>::value>::type* = 0)
 418         {
 419           return new _Sp_counted_deleter<_Tp*, _Del, std::allocator<_Tp>,
 420             _Lp>(__r.get(), __r.get_deleter());
 421         }
 422
 423       template<typename _Tp, typename _Del>
 424         static _Sp_counted_base<_Lp>*
 425         _S_create_from_up(std::unique_ptr<_Tp, _Del>&& __r,
 426           typename std::enable_if<std::is_reference<_Del>::value>::type* = 0)
 427         {
 428           typedef typename std::remove_reference<_Del>::type _Del1;
 429           typedef std::reference_wrapper<_Del1> _Del2;
 430           return new _Sp_counted_deleter<_Tp*, _Del2, std::allocator<_Tp>,
 431             _Lp>(__r.get(), std::ref(__r.get_deleter()));
 432         }
 433
 434       _Sp_counted_base<_Lp>*  _M_pi;
 435     };
 436
 437
 438   template<_Lock_policy _Lp>
 439     class __weak_count
 440     {
 441     public:
 442       __weak_count() : _M_pi(0) // nothrow
 443       { }
 444
 445       __weak_count(const __shared_count<_Lp>& __r) : _M_pi(__r._M_pi) // nothrow
 446       {
 447         if (_M_pi != 0)
 448           _M_pi->_M_weak_add_ref();
 449       }
 450
 451       __weak_count(const __weak_count<_Lp>& __r) : _M_pi(__r._M_pi) // nothrow
 452       {
 453         if (_M_pi != 0)
 454           _M_pi->_M_weak_add_ref();
 455       }
 456
 457       ~__weak_count() // nothrow
 458       {
 459         if (_M_pi != 0)
 460           _M_pi->_M_weak_release();
 461       }
 462
 463       __weak_count<_Lp>&
 464       operator=(const __shared_count<_Lp>& __r) // nothrow
 465       {
 466         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 467         if (__tmp != 0)
 468           __tmp->_M_weak_add_ref();
 469         if (_M_pi != 0)
 470           _M_pi->_M_weak_release();
 471         _M_pi = __tmp;
 472         return *this;
 473       }
 474
 475       __weak_count<_Lp>&
 476       operator=(const __weak_count<_Lp>& __r) // nothrow
 477       {
 478         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 479         if (__tmp != 0)
 480           __tmp->_M_weak_add_ref();
 481         if (_M_pi != 0)
 482           _M_pi->_M_weak_release();
 483         _M_pi = __tmp;
 484         return *this;
 485       }
 486
 487       void
 488       _M_swap(__weak_count<_Lp>& __r) // nothrow
 489       {
 490         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 491         __r._M_pi = _M_pi;
 492         _M_pi = __tmp;
 493       }
 494
 495       long
 496       _M_get_use_count() const // nothrow
 497       { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
 498
 499       bool
 500       _M_less(const __weak_count& __rhs) const
 501       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 502
 503       bool
 504       _M_less(const __shared_count<_Lp>& __rhs) const
 505       { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
 506
 507       // Friend function injected into enclosing namespace and found by ADL
 508       friend inline bool
 509       operator==(const __weak_count& __a, const __weak_count& __b)
 510       { return __a._M_pi == __b._M_pi; }
 511
 512     private:
 513       friend class __shared_count<_Lp>;
 514
 515       _Sp_counted_base<_Lp>*  _M_pi;
 516     };
 517
 518   // Now that __weak_count is defined we can define this constructor:
 519   template<_Lock_policy _Lp>
 520     inline __shared_count<_Lp>:: __shared_count(const __weak_count<_Lp>& __r)
 521     : _M_pi(__r._M_pi)
 522     {
 523       if (_M_pi != 0)
 524         _M_pi->_M_add_ref_lock();
 525       else
 526         __throw_bad_weak_ptr();
 527     }
 528
 529
 530   // Support for enable_shared_from_this.
 531
 532   // Friend of __enable_shared_from_this.
 533   template<_Lock_policy _Lp, typename _Tp1, typename _Tp2>
 534     void
 535     __enable_shared_from_this_helper(const __shared_count<_Lp>&,
 536                                      const __enable_shared_from_this<_Tp1,
 537                                      _Lp>*, const _Tp2*);
 538
 539   // Friend of enable_shared_from_this.
 540   template<typename _Tp1, typename _Tp2>
 541     void
 542     __enable_shared_from_this_helper(const __shared_count<>&,
 543                                      const enable_shared_from_this<_Tp1>*,
 544                                      const _Tp2*);
 545
 546   template<_Lock_policy _Lp>
 547     inline void
 548     __enable_shared_from_this_helper(const __shared_count<_Lp>&, ...)
 549     { }
 550
 551
 552   template<typename _Tp, _Lock_policy _Lp>
 553     class __shared_ptr
 554     {
 555     public:
 556       typedef _Tp   element_type;
 557
 558       __shared_ptr() : _M_ptr(0), _M_refcount() // never throws
 559       { }
 560
 561       template<typename _Tp1>
 562         explicit __shared_ptr(_Tp1* __p) : _M_ptr(__p), _M_refcount(__p)
 563         {
 564           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 565           static_assert( sizeof(_Tp1) > 0, "incomplete type" );
 566           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 567         }
 568
 569       template<typename _Tp1, typename _Deleter>
 570         __shared_ptr(_Tp1* __p, _Deleter __d)
 571         : _M_ptr(__p), _M_refcount(__p, __d)
 572         {
 573           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 574           // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
 575           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 576         }
 577
 578       template<typename _Tp1, typename _Deleter, typename _Alloc>
 579         __shared_ptr(_Tp1* __p, _Deleter __d, const _Alloc& __a)
 580         : _M_ptr(__p), _M_refcount(__p, __d, __a)
 581         {
 582           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 583           // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
 584           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 585         }
 586
 587       template<typename _Deleter>
 588         __shared_ptr(nullptr_t __p, _Deleter __d)
 589         : _M_ptr(0), _M_refcount(__p, __d)
 590         { }
 591
 592       template<typename _Deleter, typename _Alloc>
 593         __shared_ptr(nullptr_t __p, _Deleter __d, const _Alloc& __a)
 594         : _M_ptr(0), _M_refcount(__p, __d, __a)
 595         { }
 596
 597       template<typename _Tp1>
 598         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, _Tp* __p)
 599         : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
 600         { }
 601
 602       //  generated copy constructor, assignment, destructor are fine.
 603
 604       template<typename _Tp1, typename = typename
 605                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 606         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r)
 607         : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 608         { }
 609
 610       __shared_ptr(__shared_ptr&& __r)
 611       : _M_ptr(__r._M_ptr), _M_refcount() // never throws
 612       {
 613         _M_refcount._M_swap(__r._M_refcount);
 614         __r._M_ptr = 0;
 615       }
 616
 617       template<typename _Tp1, typename = typename
 618                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 619         __shared_ptr(__shared_ptr<_Tp1, _Lp>&& __r)
 620         : _M_ptr(__r._M_ptr), _M_refcount() // never throws
 621         {
 622           _M_refcount._M_swap(__r._M_refcount);
 623           __r._M_ptr = 0;
 624         }
 625
 626       template<typename _Tp1>
 627         explicit __shared_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 628         : _M_refcount(__r._M_refcount) // may throw
 629         {
 630           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 631
 632           // It is now safe to copy __r._M_ptr, as
 633           // _M_refcount(__r._M_refcount) did not throw.
 634           _M_ptr = __r._M_ptr;
 635         }
 636
 637       // If an exception is thrown this constructor has no effect.
 638       template<typename _Tp1, typename _Del>
 639         __shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
 640         : _M_ptr(__r.get()), _M_refcount()
 641         {
 642           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 643           _Tp1* __tmp = __r.get();
 644           _M_refcount = __shared_count<_Lp>(std::move(__r));
 645           __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
 646         }
 647
 648 #if _GLIBCXX_DEPRECATED
 649       // Postcondition: use_count() == 1 and __r.get() == 0
 650       template<typename _Tp1>
 651         __shared_ptr(std::auto_ptr<_Tp1>&& __r)
 652         : _M_ptr(__r.get()), _M_refcount()
 653         {
 654           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 655           static_assert( sizeof(_Tp1) > 0, "incomplete type" );
 656           _Tp1* __tmp = __r.get();
 657           _M_refcount = __shared_count<_Lp>(std::move(__r));
 658           __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
 659         }
 660 #endif
 661
 662       /* TODO: use delegating constructor */
 663       __shared_ptr(nullptr_t) : _M_ptr(0), _M_refcount() // never throws
 664       { }
 665
 666       template<typename _Tp1>
 667         __shared_ptr&
 668         operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws
 669         {
 670           _M_ptr = __r._M_ptr;
 671           _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
 672           return *this;
 673         }
 674
 675 #if _GLIBCXX_DEPRECATED
 676       template<typename _Tp1>
 677         __shared_ptr&
 678         operator=(std::auto_ptr<_Tp1>&& __r)
 679         {
 680           __shared_ptr(std::move(__r)).swap(*this);
 681           return *this;
 682         }
 683 #endif
 684
 685       __shared_ptr&
 686       operator=(__shared_ptr&& __r)
 687       {
 688         __shared_ptr(std::move(__r)).swap(*this);
 689         return *this;
 690       }
 691
 692       template<class _Tp1>
 693         __shared_ptr&
 694         operator=(__shared_ptr<_Tp1, _Lp>&& __r)
 695         {
 696           __shared_ptr(std::move(__r)).swap(*this);
 697           return *this;
 698         }
 699
 700       template<typename _Tp1, typename _Del>
 701         __shared_ptr&
 702         operator=(std::unique_ptr<_Tp1, _Del>&& __r)
 703         {
 704           __shared_ptr(std::move(__r)).swap(*this);
 705           return *this;
 706         }
 707
 708       void
 709       reset() // never throws
 710       { __shared_ptr().swap(*this); }
 711
 712       template<typename _Tp1>
 713         void
 714         reset(_Tp1* __p) // _Tp1 must be complete.
 715         {
 716           // Catch self-reset errors.
 717           _GLIBCXX_DEBUG_ASSERT(__p == 0 || __p != _M_ptr);
 718           __shared_ptr(__p).swap(*this);
 719         }
 720
 721       template<typename _Tp1, typename _Deleter>
 722         void
 723         reset(_Tp1* __p, _Deleter __d)
 724         { __shared_ptr(__p, __d).swap(*this); }
 725
 726       template<typename _Tp1, typename _Deleter, typename _Alloc>
 727         void
 728         reset(_Tp1* __p, _Deleter __d, const _Alloc& __a)
 729         { __shared_ptr(__p, __d, __a).swap(*this); }
 730
 731       // Allow class instantiation when _Tp is [cv-qual] void.
 732       typename std::add_lvalue_reference<_Tp>::type
 733       operator*() const // never throws
 734       {
 735         _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
 736         return *_M_ptr;
 737       }
 738
 739       _Tp*
 740       operator->() const // never throws
 741       {
 742         _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
 743         return _M_ptr;
 744       }
 745
 746       _Tp*
 747       get() const // never throws
 748       { return _M_ptr; }
 749
 750       explicit operator bool() const // never throws
 751       { return _M_ptr == 0 ? false : true; }
 752
 753       bool
 754       unique() const // never throws
 755       { return _M_refcount._M_unique(); }
 756
 757       long
 758       use_count() const // never throws
 759       { return _M_refcount._M_get_use_count(); }
 760
 761       void
 762       swap(__shared_ptr<_Tp, _Lp>& __other) // never throws
 763       {
 764         std::swap(_M_ptr, __other._M_ptr);
 765         _M_refcount._M_swap(__other._M_refcount);
 766       }
 767
 768       template<typename _Tp1>
 769         bool
 770         owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const
 771         { return _M_refcount._M_less(__rhs._M_refcount); }
 772
 773       template<typename _Tp1>
 774         bool
 775         owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const
 776         { return _M_refcount._M_less(__rhs._M_refcount); }
 777
 778 #ifdef __GXX_RTTI
 779     protected:
 780       // This constructor is non-standard, it is used by allocate_shared.
 781       template<typename _Alloc, typename... _Args>
 782         __shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
 783         : _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a,
 784                                 std::forward<_Args>(__args)...)
 785         {
 786           // _M_ptr needs to point to the newly constructed object.
 787           // This relies on _Sp_counted_ptr_inplace::_M_get_deleter.
 788           void* __p = _M_refcount._M_get_deleter(typeid(__tag));
 789           _M_ptr = static_cast<_Tp*>(__p);
 790           __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
 791         }
 792 #else
 793       template<typename _Alloc>
 794         struct _Deleter
 795         {
 796           void operator()(_Tp* __ptr)
 797           {
 798             _M_alloc.destroy(__ptr);
 799             _M_alloc.deallocate(__ptr, 1);
 800           }
 801           _Alloc _M_alloc;
 802         };
 803
 804       template<typename _Alloc, typename... _Args>
 805         __shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
 806         : _M_ptr(), _M_refcount()
 807         {
 808           typedef typename _Alloc::template rebind<_Tp>::other _Alloc2;
 809           _Deleter<_Alloc2> __del = { _Alloc2(__a) };
 810           _M_ptr = __del._M_alloc.allocate(1);
 811           __try
 812             {
 813               __del._M_alloc.construct(_M_ptr, std::forward<_Args>(__args)...);
 814             }
 815           __catch(...)
 816             {
 817               __del._M_alloc.deallocate(_M_ptr, 1);
 818               __throw_exception_again;
 819             }
 820           __shared_count<_Lp> __count(_M_ptr, __del, __del._M_alloc);
 821           _M_refcount._M_swap(__count);
 822           __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
 823         }
 824 #endif
 825
 826       template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
 827                typename... _Args>
 828         friend __shared_ptr<_Tp1, _Lp1>
 829         __allocate_shared(_Alloc __a, _Args&&... __args);
 830
 831     private:
 832       void*
 833       _M_get_deleter(const std::type_info& __ti) const
 834       { return _M_refcount._M_get_deleter(__ti); }
 835
 836       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
 837       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
 838
 839       template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
 840         friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&);
 841
 842       _Tp*                 _M_ptr;         // Contained pointer.
 843       __shared_count<_Lp>  _M_refcount;    // Reference counter.
 844     };
 845
 846
 847   // 20.8.13.2.7 shared_ptr comparisons
 848   template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
 849     inline bool
 850     operator==(const __shared_ptr<_Tp1, _Lp>& __a,
 851                const __shared_ptr<_Tp2, _Lp>& __b)
 852     { return __a.get() == __b.get(); }
 853
 854   template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
 855     inline bool
 856     operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
 857                const __shared_ptr<_Tp2, _Lp>& __b)
 858     { return __a.get() != __b.get(); }
 859
 860   template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
 861     inline bool
 862     operator<(const __shared_ptr<_Tp1, _Lp>& __a,
 863               const __shared_ptr<_Tp2, _Lp>& __b)
 864     { return __a.get() < __b.get(); }
 865
 866   template<typename _Sp>
 867     struct _Sp_less : public binary_function<_Sp, _Sp, bool>
 868     {
 869       bool
 870       operator()(const _Sp& __lhs, const _Sp& __rhs) const
 871       {
 872         typedef typename _Sp::element_type element_type;
 873         return std::less<element_type*>()(__lhs.get(), __rhs.get());
 874       }
 875     };
 876
 877   template<typename _Tp, _Lock_policy _Lp>
 878     struct less<__shared_ptr<_Tp, _Lp>>
 879     : public _Sp_less<__shared_ptr<_Tp, _Lp>>
 880     { };
 881
 882   // XXX LessThanComparable<_Tp> concept should provide >, >= and <=
 883   template<typename _Tp, _Lock_policy _Lp>
 884     inline bool
 885     operator>(const __shared_ptr<_Tp, _Lp>& __a,
 886               const __shared_ptr<_Tp, _Lp>& __b)
 887     { return __a.get() > __b.get(); }
 888
 889   template<typename _Tp, _Lock_policy _Lp>
 890     inline bool
 891     operator>=(const __shared_ptr<_Tp, _Lp>& __a,
 892                const __shared_ptr<_Tp, _Lp>& __b)
 893     { return __a.get() >= __b.get(); }
 894
 895   template<typename _Tp, _Lock_policy _Lp>
 896     inline bool
 897     operator<=(const __shared_ptr<_Tp, _Lp>& __a,
 898                const __shared_ptr<_Tp, _Lp>& __b)
 899     { return __a.get() <= __b.get(); }
 900
 901   // 2.2.3.8 shared_ptr specialized algorithms.
 902   template<typename _Tp, _Lock_policy _Lp>
 903     inline void
 904     swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b)
 905     { __a.swap(__b); }
 906
 907   // 2.2.3.9 shared_ptr casts
 908
 909   // The seemingly equivalent code:
 910   // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
 911   // will eventually result in undefined behaviour, attempting to
 912   // delete the same object twice.
 913   /// static_pointer_cast
 914   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 915     inline __shared_ptr<_Tp, _Lp>
 916     static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 917     { return __shared_ptr<_Tp, _Lp>(__r, static_cast<_Tp*>(__r.get())); }
 918
 919   // The seemingly equivalent code:
 920   // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
 921   // will eventually result in undefined behaviour, attempting to
 922   // delete the same object twice.
 923   /// const_pointer_cast
 924   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 925     inline __shared_ptr<_Tp, _Lp>
 926     const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 927     { return __shared_ptr<_Tp, _Lp>(__r, const_cast<_Tp*>(__r.get())); }
 928
 929   // The seemingly equivalent code:
 930   // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
 931   // will eventually result in undefined behaviour, attempting to
 932   // delete the same object twice.
 933   /// dynamic_pointer_cast
 934   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 935     inline __shared_ptr<_Tp, _Lp>
 936     dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 937     {
 938       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
 939         return __shared_ptr<_Tp, _Lp>(__r, __p);
 940       return __shared_ptr<_Tp, _Lp>();
 941     }
 942
 943
 944   template<typename _Tp, _Lock_policy _Lp>
 945     class __weak_ptr
 946     {
 947     public:
 948       typedef _Tp element_type;
 949
 950       __weak_ptr() : _M_ptr(0), _M_refcount() // never throws
 951       { }
 952
 953       // Generated copy constructor, assignment, destructor are fine.
 954
 955       // The "obvious" converting constructor implementation:
 956       //
 957       //  template<typename _Tp1>
 958       //    __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 959       //    : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 960       //    { }
 961       //
 962       // has a serious problem.
 963       //
 964       //  __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
 965       //  conversion may require access to *__r._M_ptr (virtual inheritance).
 966       //
 967       // It is not possible to avoid spurious access violations since
 968       // in multithreaded programs __r._M_ptr may be invalidated at any point.
 969       template<typename _Tp1, typename = typename
 970                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 971         __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 972         : _M_refcount(__r._M_refcount) // never throws
 973         { _M_ptr = __r.lock().get(); }
 974
 975       template<typename _Tp1, typename = typename
 976                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 977         __weak_ptr(const __shared_ptr<_Tp1, _Lp>& __r)
 978         : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 979         { }
 980
 981       template<typename _Tp1>
 982         __weak_ptr&
 983         operator=(const __weak_ptr<_Tp1, _Lp>& __r) // never throws
 984         {
 985           _M_ptr = __r.lock().get();
 986           _M_refcount = __r._M_refcount;
 987           return *this;
 988         }
 989
 990       template<typename _Tp1>
 991         __weak_ptr&
 992         operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws
 993         {
 994           _M_ptr = __r._M_ptr;
 995           _M_refcount = __r._M_refcount;
 996           return *this;
 997         }
 998
 999       __shared_ptr<_Tp, _Lp>
1000       lock() const // never throws
1001       {
1002 #ifdef __GTHREADS
1003         // Optimization: avoid throw overhead.
1004         if (expired())
1005           return __shared_ptr<element_type, _Lp>();
1006
1007         __try
1008           {
1009             return __shared_ptr<element_type, _Lp>(*this);
1010           }
1011         __catch(const bad_weak_ptr&)
1012           {
1013             // Q: How can we get here?
1014             // A: Another thread may have invalidated r after the
1015             //    use_count test above.
1016             return __shared_ptr<element_type, _Lp>();
1017           }
1018
1019 #else
1020         // Optimization: avoid try/catch overhead when single threaded.
1021         return expired() ? __shared_ptr<element_type, _Lp>()
1022                          : __shared_ptr<element_type, _Lp>(*this);
1023
1024 #endif
1025       } // XXX MT
1026
1027       long
1028       use_count() const // never throws
1029       { return _M_refcount._M_get_use_count(); }
1030
1031       bool
1032       expired() const // never throws
1033       { return _M_refcount._M_get_use_count() == 0; }
1034
1035       template<typename _Tp1>
1036         bool
1037         owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const
1038         { return _M_refcount._M_less(__rhs._M_refcount); }
1039
1040       template<typename _Tp1>
1041         bool
1042         owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const
1043         { return _M_refcount._M_less(__rhs._M_refcount); }
1044
1045       void
1046       reset() // never throws
1047       { __weak_ptr().swap(*this); }
1048
1049       void
1050       swap(__weak_ptr& __s) // never throws
1051       {
1052         std::swap(_M_ptr, __s._M_ptr);
1053         _M_refcount._M_swap(__s._M_refcount);
1054       }
1055
1056     private:
1057       // Used by __enable_shared_from_this.
1058       void
1059       _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount)
1060       {
1061         _M_ptr = __ptr;
1062         _M_refcount = __refcount;
1063       }
1064
1065       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1066       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1067       friend class __enable_shared_from_this<_Tp, _Lp>;
1068       friend class enable_shared_from_this<_Tp>;
1069
1070       _Tp*               _M_ptr;         // Contained pointer.
1071       __weak_count<_Lp>  _M_refcount;    // Reference counter.
1072     };
1073
1074   // 20.8.13.3.7 weak_ptr specialized algorithms.
1075   template<typename _Tp, _Lock_policy _Lp>
1076     inline void
1077     swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b)
1078     { __a.swap(__b); }
1079
1080   template<typename _Tp, typename _Tp1>
1081     struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
1082     {
1083       bool
1084       operator()(const _Tp& __lhs, const _Tp& __rhs) const
1085       { return __lhs.owner_before(__rhs); }
1086
1087       bool
1088       operator()(const _Tp& __lhs, const _Tp1& __rhs) const
1089       { return __lhs.owner_before(__rhs); }
1090
1091       bool
1092       operator()(const _Tp1& __lhs, const _Tp& __rhs) const
1093       { return __lhs.owner_before(__rhs); }
1094     };
1095
1096   template<typename _Tp, _Lock_policy _Lp>
1097     struct owner_less<__shared_ptr<_Tp, _Lp>>
1098     : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
1099     { };
1100
1101   template<typename _Tp, _Lock_policy _Lp>
1102     struct owner_less<__weak_ptr<_Tp, _Lp>>
1103     : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
1104     { };
1105
1106
1107   template<typename _Tp, _Lock_policy _Lp>
1108     class __enable_shared_from_this
1109     {
1110     protected:
1111       __enable_shared_from_this() { }
1112
1113       __enable_shared_from_this(const __enable_shared_from_this&) { }
1114
1115       __enable_shared_from_this&
1116       operator=(const __enable_shared_from_this&)
1117       { return *this; }
1118
1119       ~__enable_shared_from_this() { }
1120
1121     public:
1122       __shared_ptr<_Tp, _Lp>
1123       shared_from_this()
1124       { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
1125
1126       __shared_ptr<const _Tp, _Lp>
1127       shared_from_this() const
1128       { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
1129
1130     private:
1131       template<typename _Tp1>
1132         void
1133         _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const
1134         { _M_weak_this._M_assign(__p, __n); }
1135
1136       template<typename _Tp1>
1137         friend void
1138         __enable_shared_from_this_helper(const __shared_count<_Lp>& __pn,
1139                                          const __enable_shared_from_this* __pe,
1140                                          const _Tp1* __px)
1141         {
1142           if (__pe != 0)
1143             __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
1144         }
1145
1146       mutable __weak_ptr<_Tp, _Lp>  _M_weak_this;
1147     };
1148
1149
1150   template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
1151     inline __shared_ptr<_Tp, _Lp>
1152     __allocate_shared(_Alloc __a, _Args&&... __args)
1153     {
1154       return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(),
1155           std::forward<_Alloc>(__a), std::forward<_Args>(__args)...);
1156     }
1157
1158   template<typename _Tp, _Lock_policy _Lp, typename... _Args>
1159     inline __shared_ptr<_Tp, _Lp>
1160     __make_shared(_Args&&... __args)
1161     {
1162       typedef typename std::remove_const<_Tp>::type _Tp_nc;
1163       return __allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
1164                                          std::forward<_Args>(__args)...);
1165     }
1166
1167   /// std::hash specialization for __shared_ptr.
1168   template<typename _Tp, _Lock_policy _Lp>
1169     struct hash<__shared_ptr<_Tp, _Lp>>
1170     : public std::unary_function<__shared_ptr<_Tp, _Lp>, size_t>
1171     {
1172       size_t
1173       operator()(const __shared_ptr<_Tp, _Lp>& __s) const
1174       { return std::hash<_Tp*>()(__s.get()); }
1175     };
1176
1177 _GLIBCXX_END_NAMESPACE
1178
1179 #endif // _SHARED_PTR_BASE_H