libstdc++-v3/include/tr1/shared_ptr.h

   1 // <tr1/shared_ptr.h> -*- 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 //  shared_count.hpp
  26 //  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
  27
  28 //  shared_ptr.hpp
  29 //  Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
  30 //  Copyright (C) 2001, 2002, 2003 Peter Dimov
  31
  32 //  weak_ptr.hpp
  33 //  Copyright (C) 2001, 2002, 2003 Peter Dimov
  34
  35 //  enable_shared_from_this.hpp
  36 //  Copyright (C) 2002 Peter Dimov
  37
  38 // Distributed under the Boost Software License, Version 1.0. (See
  39 // accompanying file LICENSE_1_0.txt or copy at
  40 // http://www.boost.org/LICENSE_1_0.txt)
  41
  42 // GCC Note:  based on version 1.32.0 of the Boost library.
  43
  44 /** @file tr1/shared_ptr.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 _TR1_SHARED_PTR_H
  50 #define _TR1_SHARED_PTR_H 1
  51
  52 #if defined(_GLIBCXX_INCLUDE_AS_CXX0X)
  53 #  error TR1 header cannot be included from C++0x header
  54 #endif
  55
  56 namespace std
  57 {
  58 namespace tr1
  59 {
  60
  61   template<typename _Ptr, typename _Deleter, _Lock_policy _Lp>
  62     class _Sp_counted_base_impl
  63     : public _Sp_counted_base<_Lp>
  64     {
  65     public:
  66       /**
  67        *  @brief
  68        *  @pre     __d(__p) must not throw.
  69        */
  70       _Sp_counted_base_impl(_Ptr __p, _Deleter __d)
  71       : _M_ptr(__p), _M_del(__d) { }
  72
  73       virtual void
  74       _M_dispose() // nothrow
  75       { _M_del(_M_ptr); }
  76
  77       virtual void*
  78       _M_get_deleter(const std::type_info& __ti)
  79       { return __ti == typeid(_Deleter) ? &_M_del : 0; }
  80
  81     private:
  82       _Sp_counted_base_impl(const _Sp_counted_base_impl&);
  83       _Sp_counted_base_impl& operator=(const _Sp_counted_base_impl&);
  84
  85       _Ptr      _M_ptr;  // copy constructor must not throw
  86       _Deleter  _M_del;  // copy constructor must not throw
  87     };
  88
  89   template<_Lock_policy _Lp = __default_lock_policy>
  90     class __weak_count;
  91
  92   template<typename _Tp>
  93     struct _Sp_deleter
  94     {
  95       typedef void result_type;
  96       typedef _Tp* argument_type;
  97       void operator()(_Tp* __p) const { delete __p; }
  98     };
  99
 100   template<_Lock_policy _Lp = __default_lock_policy>
 101     class __shared_count
 102     {
 103     public:
 104       __shared_count()
 105       : _M_pi(0) // nothrow
 106       { }
 107
 108       template<typename _Ptr>
 109         __shared_count(_Ptr __p) : _M_pi(0)
 110         {
 111           __try
 112             {
 113               typedef typename std::tr1::remove_pointer<_Ptr>::type _Tp;
 114               _M_pi = new _Sp_counted_base_impl<_Ptr, _Sp_deleter<_Tp>, _Lp>(
 115                   __p, _Sp_deleter<_Tp>());
 116             }
 117           __catch(...)
 118             {
 119               delete __p;
 120               __throw_exception_again;
 121             }
 122         }
 123
 124       template<typename _Ptr, typename _Deleter>
 125         __shared_count(_Ptr __p, _Deleter __d) : _M_pi(0)
 126         {
 127           __try
 128             {
 129               _M_pi = new _Sp_counted_base_impl<_Ptr, _Deleter, _Lp>(__p, __d);
 130             }
 131           __catch(...)
 132             {
 133               __d(__p); // Call _Deleter on __p.
 134               __throw_exception_again;
 135             }
 136         }
 137
 138       // Special case for auto_ptr<_Tp> to provide the strong guarantee.
 139       template<typename _Tp>
 140         explicit
 141         __shared_count(std::auto_ptr<_Tp>& __r)
 142         : _M_pi(new _Sp_counted_base_impl<_Tp*,
 143                 _Sp_deleter<_Tp>, _Lp >(__r.get(), _Sp_deleter<_Tp>()))
 144         { __r.release(); }
 145
 146       // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
 147       explicit
 148       __shared_count(const __weak_count<_Lp>& __r);
 149
 150       ~__shared_count() // nothrow
 151       {
 152         if (_M_pi != 0)
 153           _M_pi->_M_release();
 154       }
 155
 156       __shared_count(const __shared_count& __r)
 157       : _M_pi(__r._M_pi) // nothrow
 158       {
 159         if (_M_pi != 0)
 160           _M_pi->_M_add_ref_copy();
 161       }
 162
 163       __shared_count&
 164       operator=(const __shared_count& __r) // nothrow
 165       {
 166         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 167         if (__tmp != _M_pi)
 168           {
 169             if (__tmp != 0)
 170               __tmp->_M_add_ref_copy();
 171             if (_M_pi != 0)
 172               _M_pi->_M_release();
 173             _M_pi = __tmp;
 174           }
 175         return *this;
 176       }
 177
 178       void
 179       _M_swap(__shared_count& __r) // nothrow
 180       {
 181         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 182         __r._M_pi = _M_pi;
 183         _M_pi = __tmp;
 184       }
 185
 186       long
 187       _M_get_use_count() const // nothrow
 188       { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
 189
 190       bool
 191       _M_unique() const // nothrow
 192       { return this->_M_get_use_count() == 1; }
 193
 194       friend inline bool
 195       operator==(const __shared_count& __a, const __shared_count& __b)
 196       { return __a._M_pi == __b._M_pi; }
 197
 198       friend inline bool
 199       operator<(const __shared_count& __a, const __shared_count& __b)
 200       { return std::less<_Sp_counted_base<_Lp>*>()(__a._M_pi, __b._M_pi); }
 201
 202       void*
 203       _M_get_deleter(const std::type_info& __ti) const
 204       { return _M_pi ? _M_pi->_M_get_deleter(__ti) : 0; }
 205
 206     private:
 207       friend class __weak_count<_Lp>;
 208
 209       _Sp_counted_base<_Lp>*  _M_pi;
 210     };
 211
 212
 213   template<_Lock_policy _Lp>
 214     class __weak_count
 215     {
 216     public:
 217       __weak_count()
 218       : _M_pi(0) // nothrow
 219       { }
 220
 221       __weak_count(const __shared_count<_Lp>& __r)
 222       : _M_pi(__r._M_pi) // nothrow
 223       {
 224         if (_M_pi != 0)
 225           _M_pi->_M_weak_add_ref();
 226       }
 227
 228       __weak_count(const __weak_count<_Lp>& __r)
 229       : _M_pi(__r._M_pi) // nothrow
 230       {
 231         if (_M_pi != 0)
 232           _M_pi->_M_weak_add_ref();
 233       }
 234
 235       ~__weak_count() // nothrow
 236       {
 237         if (_M_pi != 0)
 238           _M_pi->_M_weak_release();
 239       }
 240
 241       __weak_count<_Lp>&
 242       operator=(const __shared_count<_Lp>& __r) // nothrow
 243       {
 244         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 245         if (__tmp != 0)
 246           __tmp->_M_weak_add_ref();
 247         if (_M_pi != 0)
 248           _M_pi->_M_weak_release();
 249         _M_pi = __tmp;
 250         return *this;
 251       }
 252
 253       __weak_count<_Lp>&
 254       operator=(const __weak_count<_Lp>& __r) // nothrow
 255       {
 256         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 257         if (__tmp != 0)
 258           __tmp->_M_weak_add_ref();
 259         if (_M_pi != 0)
 260           _M_pi->_M_weak_release();
 261         _M_pi = __tmp;
 262         return *this;
 263       }
 264
 265       void
 266       _M_swap(__weak_count<_Lp>& __r) // nothrow
 267       {
 268         _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
 269         __r._M_pi = _M_pi;
 270         _M_pi = __tmp;
 271       }
 272
 273       long
 274       _M_get_use_count() const // nothrow
 275       { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
 276
 277       friend inline bool
 278       operator==(const __weak_count<_Lp>& __a, const __weak_count<_Lp>& __b)
 279       { return __a._M_pi == __b._M_pi; }
 280
 281       friend inline bool
 282       operator<(const __weak_count<_Lp>& __a, const __weak_count<_Lp>& __b)
 283       { return std::less<_Sp_counted_base<_Lp>*>()(__a._M_pi, __b._M_pi); }
 284
 285     private:
 286       friend class __shared_count<_Lp>;
 287
 288       _Sp_counted_base<_Lp>*  _M_pi;
 289     };
 290
 291   // now that __weak_count is defined we can define this constructor:
 292   template<_Lock_policy _Lp>
 293     inline
 294     __shared_count<_Lp>::
 295     __shared_count(const __weak_count<_Lp>& __r)
 296     : _M_pi(__r._M_pi)
 297     {
 298       if (_M_pi != 0)
 299         _M_pi->_M_add_ref_lock();
 300       else
 301         __throw_bad_weak_ptr();
 302     }
 303
 304   // Forward declarations.
 305   template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
 306     class __shared_ptr;
 307
 308   template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
 309     class __weak_ptr;
 310
 311   template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
 312     class __enable_shared_from_this;
 313
 314   template<typename _Tp>
 315     class shared_ptr;
 316
 317   template<typename _Tp>
 318     class weak_ptr;
 319
 320   template<typename _Tp>
 321     class enable_shared_from_this;
 322
 323   // Support for enable_shared_from_this.
 324
 325   // Friend of __enable_shared_from_this.
 326   template<_Lock_policy _Lp, typename _Tp1, typename _Tp2>
 327     void
 328     __enable_shared_from_this_helper(const __shared_count<_Lp>&,
 329                                      const __enable_shared_from_this<_Tp1,
 330                                      _Lp>*, const _Tp2*);
 331
 332   // Friend of enable_shared_from_this.
 333   template<typename _Tp1, typename _Tp2>
 334     void
 335     __enable_shared_from_this_helper(const __shared_count<>&,
 336                                      const enable_shared_from_this<_Tp1>*,
 337                                      const _Tp2*);
 338
 339   template<_Lock_policy _Lp>
 340     inline void
 341     __enable_shared_from_this_helper(const __shared_count<_Lp>&, ...)
 342     { }
 343
 344
 345   struct __static_cast_tag { };
 346   struct __const_cast_tag { };
 347   struct __dynamic_cast_tag { };
 348
 349   /**
 350    *  @class __shared_ptr
 351    *
 352    *  A smart pointer with reference-counted copy semantics.
 353    *  The object pointed to is deleted when the last shared_ptr pointing to
 354    *  it is destroyed or reset.
 355    */
 356   template<typename _Tp, _Lock_policy _Lp>
 357     class __shared_ptr
 358     {
 359     public:
 360       typedef _Tp   element_type;
 361
 362       /** @brief  Construct an empty %__shared_ptr.
 363        *  @post   use_count()==0 && get()==0
 364        */
 365       __shared_ptr()
 366       : _M_ptr(0), _M_refcount() // never throws
 367       { }
 368
 369       /** @brief  Construct a %__shared_ptr that owns the pointer @a __p.
 370        *  @param  __p  A pointer that is convertible to element_type*.
 371        *  @post   use_count() == 1 && get() == __p
 372        *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
 373        */
 374       template<typename _Tp1>
 375         explicit
 376         __shared_ptr(_Tp1* __p)
 377         : _M_ptr(__p), _M_refcount(__p)
 378         {
 379           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 380           // __glibcxx_function_requires(_CompleteConcept<_Tp1*>)
 381           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 382         }
 383
 384       //
 385       // Requirements: _Deleter's copy constructor and destructor must
 386       // not throw
 387       //
 388       // __shared_ptr will release __p by calling __d(__p)
 389       //
 390       /** @brief  Construct a %__shared_ptr that owns the pointer @a __p
 391        *          and the deleter @a __d.
 392        *  @param  __p  A pointer.
 393        *  @param  __d  A deleter.
 394        *  @post   use_count() == 1 && get() == __p
 395        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 396        */
 397       template<typename _Tp1, typename _Deleter>
 398         __shared_ptr(_Tp1* __p, _Deleter __d)
 399         : _M_ptr(__p), _M_refcount(__p, __d)
 400         {
 401           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 402           // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
 403           __enable_shared_from_this_helper(_M_refcount, __p, __p);
 404         }
 405
 406       //  generated copy constructor, assignment, destructor are fine.
 407
 408       /** @brief  If @a __r is empty, constructs an empty %__shared_ptr;
 409        *          otherwise construct a %__shared_ptr that shares ownership
 410        *          with @a __r.
 411        *  @param  __r  A %__shared_ptr.
 412        *  @post   get() == __r.get() && use_count() == __r.use_count()
 413        */
 414       template<typename _Tp1>
 415         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r)
 416         : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 417         { __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) }
 418
 419       /** @brief  Constructs a %__shared_ptr that shares ownership with @a __r
 420        *          and stores a copy of the pointer stored in @a __r.
 421        *  @param  __r  A weak_ptr.
 422        *  @post   use_count() == __r.use_count()
 423        *  @throw  bad_weak_ptr when __r.expired(),
 424        *          in which case the constructor has no effect.
 425        */
 426       template<typename _Tp1>
 427         explicit
 428         __shared_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 429         : _M_refcount(__r._M_refcount) // may throw
 430         {
 431           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 432           // It is now safe to copy __r._M_ptr, as _M_refcount(__r._M_refcount)
 433           // did not throw.
 434           _M_ptr = __r._M_ptr;
 435         }
 436
 437 #if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_DEPRECATED
 438       /**
 439        * @post use_count() == 1 and __r.get() == 0
 440        */
 441       template<typename _Tp1>
 442         explicit
 443         __shared_ptr(std::auto_ptr<_Tp1>& __r)
 444         : _M_ptr(__r.get()), _M_refcount()
 445         {
 446           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 447           // TODO requires _Tp1 is complete, delete __r.release() well-formed
 448           _Tp1* __tmp = __r.get();
 449           _M_refcount = __shared_count<_Lp>(__r);
 450           __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
 451         }
 452
 453 #endif
 454
 455       template<typename _Tp1>
 456         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, __static_cast_tag)
 457         : _M_ptr(static_cast<element_type*>(__r._M_ptr)),
 458           _M_refcount(__r._M_refcount)
 459         { }
 460
 461       template<typename _Tp1>
 462         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, __const_cast_tag)
 463         : _M_ptr(const_cast<element_type*>(__r._M_ptr)),
 464           _M_refcount(__r._M_refcount)
 465         { }
 466
 467       template<typename _Tp1>
 468         __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, __dynamic_cast_tag)
 469         : _M_ptr(dynamic_cast<element_type*>(__r._M_ptr)),
 470           _M_refcount(__r._M_refcount)
 471         {
 472           if (_M_ptr == 0) // need to allocate new counter -- the cast failed
 473             _M_refcount = __shared_count<_Lp>();
 474         }
 475
 476       template<typename _Tp1>
 477         __shared_ptr&
 478         operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws
 479         {
 480           _M_ptr = __r._M_ptr;
 481           _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
 482           return *this;
 483         }
 484
 485 #if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_DEPRECATED
 486       template<typename _Tp1>
 487         __shared_ptr&
 488         operator=(std::auto_ptr<_Tp1>& __r)
 489         {
 490           __shared_ptr(__r).swap(*this);
 491           return *this;
 492         }
 493 #endif
 494
 495       void
 496       reset() // never throws
 497       { __shared_ptr().swap(*this); }
 498
 499       template<typename _Tp1>
 500         void
 501         reset(_Tp1* __p) // _Tp1 must be complete.
 502         {
 503           // Catch self-reset errors.
 504           _GLIBCXX_DEBUG_ASSERT(__p == 0 || __p != _M_ptr);
 505           __shared_ptr(__p).swap(*this);
 506         }
 507
 508       template<typename _Tp1, typename _Deleter>
 509         void
 510         reset(_Tp1* __p, _Deleter __d)
 511         { __shared_ptr(__p, __d).swap(*this); }
 512
 513       // Allow class instantiation when _Tp is [cv-qual] void.
 514       typename std::tr1::add_reference<_Tp>::type
 515       operator*() const // never throws
 516       {
 517         _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
 518         return *_M_ptr;
 519       }
 520
 521       _Tp*
 522       operator->() const // never throws
 523       {
 524         _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
 525         return _M_ptr;
 526       }
 527
 528       _Tp*
 529       get() const // never throws
 530       { return _M_ptr; }
 531
 532       // Implicit conversion to "bool"
 533     private:
 534       typedef _Tp* __shared_ptr::*__unspecified_bool_type;
 535
 536     public:
 537       operator __unspecified_bool_type() const // never throws
 538       { return _M_ptr == 0 ? 0 : &__shared_ptr::_M_ptr; }
 539
 540       bool
 541       unique() const // never throws
 542       { return _M_refcount._M_unique(); }
 543
 544       long
 545       use_count() const // never throws
 546       { return _M_refcount._M_get_use_count(); }
 547
 548       void
 549       swap(__shared_ptr<_Tp, _Lp>& __other) // never throws
 550       {
 551         std::swap(_M_ptr, __other._M_ptr);
 552         _M_refcount._M_swap(__other._M_refcount);
 553       }
 554
 555     private:
 556       void*
 557       _M_get_deleter(const std::type_info& __ti) const
 558       { return _M_refcount._M_get_deleter(__ti); }
 559
 560       template<typename _Tp1, _Lock_policy _Lp1>
 561         bool
 562         _M_less(const __shared_ptr<_Tp1, _Lp1>& __rhs) const
 563         { return _M_refcount < __rhs._M_refcount; }
 564
 565       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
 566       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
 567
 568       template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
 569         friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&);
 570
 571       // Friends injected into enclosing namespace and found by ADL:
 572       template<typename _Tp1>
 573         friend inline bool
 574         operator==(const __shared_ptr& __a, const __shared_ptr<_Tp1, _Lp>& __b)
 575         { return __a.get() == __b.get(); }
 576
 577       template<typename _Tp1>
 578         friend inline bool
 579         operator!=(const __shared_ptr& __a, const __shared_ptr<_Tp1, _Lp>& __b)
 580         { return __a.get() != __b.get(); }
 581
 582       template<typename _Tp1>
 583         friend inline bool
 584         operator<(const __shared_ptr& __a, const __shared_ptr<_Tp1, _Lp>& __b)
 585         { return __a._M_less(__b); }
 586
 587       _Tp*                 _M_ptr;         // Contained pointer.
 588       __shared_count<_Lp>  _M_refcount;    // Reference counter.
 589     };
 590
 591   // 2.2.3.8 shared_ptr specialized algorithms.
 592   template<typename _Tp, _Lock_policy _Lp>
 593     inline void
 594     swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b)
 595     { __a.swap(__b); }
 596
 597   // 2.2.3.9 shared_ptr casts
 598   /** @warning The seemingly equivalent
 599    *           <code>shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))</code>
 600    *           will eventually result in undefined behaviour,
 601    *           attempting to delete the same object twice.
 602    */
 603   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 604     inline __shared_ptr<_Tp, _Lp>
 605     static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 606     { return __shared_ptr<_Tp, _Lp>(__r, __static_cast_tag()); }
 607
 608   /** @warning The seemingly equivalent
 609    *           <code>shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))</code>
 610    *           will eventually result in undefined behaviour,
 611    *           attempting to delete the same object twice.
 612    */
 613   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 614     inline __shared_ptr<_Tp, _Lp>
 615     const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 616     { return __shared_ptr<_Tp, _Lp>(__r, __const_cast_tag()); }
 617
 618   /** @warning The seemingly equivalent
 619    *           <code>shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))</code>
 620    *           will eventually result in undefined behaviour,
 621    *           attempting to delete the same object twice.
 622    */
 623   template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
 624     inline __shared_ptr<_Tp, _Lp>
 625     dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r)
 626     { return __shared_ptr<_Tp, _Lp>(__r, __dynamic_cast_tag()); }
 627
 628   // 2.2.3.7 shared_ptr I/O
 629   template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
 630     std::basic_ostream<_Ch, _Tr>&
 631     operator<<(std::basic_ostream<_Ch, _Tr>& __os,
 632                const __shared_ptr<_Tp, _Lp>& __p)
 633     {
 634       __os << __p.get();
 635       return __os;
 636     }
 637
 638   // 2.2.3.10 shared_ptr get_deleter (experimental)
 639   template<typename _Del, typename _Tp, _Lock_policy _Lp>
 640     inline _Del*
 641     get_deleter(const __shared_ptr<_Tp, _Lp>& __p)
 642     { return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del))); }
 643
 644
 645   template<typename _Tp, _Lock_policy _Lp>
 646     class __weak_ptr
 647     {
 648     public:
 649       typedef _Tp element_type;
 650
 651       __weak_ptr()
 652       : _M_ptr(0), _M_refcount() // never throws
 653       { }
 654
 655       // Generated copy constructor, assignment, destructor are fine.
 656
 657       // The "obvious" converting constructor implementation:
 658       //
 659       //  template<typename _Tp1>
 660       //    __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 661       //    : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 662       //    { }
 663       //
 664       // has a serious problem.
 665       //
 666       //  __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
 667       //  conversion may require access to *__r._M_ptr (virtual inheritance).
 668       //
 669       // It is not possible to avoid spurious access violations since
 670       // in multithreaded programs __r._M_ptr may be invalidated at any point.
 671       template<typename _Tp1>
 672         __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
 673         : _M_refcount(__r._M_refcount) // never throws
 674         {
 675           __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
 676           _M_ptr = __r.lock().get();
 677         }
 678
 679       template<typename _Tp1>
 680         __weak_ptr(const __shared_ptr<_Tp1, _Lp>& __r)
 681         : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
 682         { __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) }
 683
 684       template<typename _Tp1>
 685         __weak_ptr&
 686         operator=(const __weak_ptr<_Tp1, _Lp>& __r) // never throws
 687         {
 688           _M_ptr = __r.lock().get();
 689           _M_refcount = __r._M_refcount;
 690           return *this;
 691         }
 692
 693       template<typename _Tp1>
 694         __weak_ptr&
 695         operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws
 696         {
 697           _M_ptr = __r._M_ptr;
 698           _M_refcount = __r._M_refcount;
 699           return *this;
 700         }
 701
 702       __shared_ptr<_Tp, _Lp>
 703       lock() const // never throws
 704       {
 705 #ifdef __GTHREADS
 706         // Optimization: avoid throw overhead.
 707         if (expired())
 708           return __shared_ptr<element_type, _Lp>();
 709
 710         __try
 711           {
 712             return __shared_ptr<element_type, _Lp>(*this);
 713           }
 714         __catch(const bad_weak_ptr&)
 715           {
 716             // Q: How can we get here?
 717             // A: Another thread may have invalidated r after the
 718             //    use_count test above.
 719             return __shared_ptr<element_type, _Lp>();
 720           }
 721
 722 #else
 723         // Optimization: avoid try/catch overhead when single threaded.
 724         return expired() ? __shared_ptr<element_type, _Lp>()
 725                          : __shared_ptr<element_type, _Lp>(*this);
 726
 727 #endif
 728       } // XXX MT
 729
 730       long
 731       use_count() const // never throws
 732       { return _M_refcount._M_get_use_count(); }
 733
 734       bool
 735       expired() const // never throws
 736       { return _M_refcount._M_get_use_count() == 0; }
 737
 738       void
 739       reset() // never throws
 740       { __weak_ptr().swap(*this); }
 741
 742       void
 743       swap(__weak_ptr& __s) // never throws
 744       {
 745         std::swap(_M_ptr, __s._M_ptr);
 746         _M_refcount._M_swap(__s._M_refcount);
 747       }
 748
 749     private:
 750       // Used by __enable_shared_from_this.
 751       void
 752       _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount)
 753       {
 754         _M_ptr = __ptr;
 755         _M_refcount = __refcount;
 756       }
 757
 758       template<typename _Tp1>
 759         bool
 760         _M_less(const __weak_ptr<_Tp1, _Lp>& __rhs) const
 761         { return _M_refcount < __rhs._M_refcount; }
 762
 763       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
 764       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
 765       friend class __enable_shared_from_this<_Tp, _Lp>;
 766       friend class enable_shared_from_this<_Tp>;
 767
 768       // Friend injected into namespace and found by ADL.
 769       template<typename _Tp1>
 770         friend inline bool
 771         operator<(const __weak_ptr& __lhs, const __weak_ptr<_Tp1, _Lp>& __rhs)
 772         { return __lhs._M_less(__rhs); }
 773
 774       _Tp*               _M_ptr;         // Contained pointer.
 775       __weak_count<_Lp>  _M_refcount;    // Reference counter.
 776     };
 777
 778   // 2.2.4.7 weak_ptr specialized algorithms.
 779   template<typename _Tp, _Lock_policy _Lp>
 780     inline void
 781     swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b)
 782     { __a.swap(__b); }
 783
 784
 785   template<typename _Tp, _Lock_policy _Lp>
 786     class __enable_shared_from_this
 787     {
 788     protected:
 789       __enable_shared_from_this() { }
 790
 791       __enable_shared_from_this(const __enable_shared_from_this&) { }
 792
 793       __enable_shared_from_this&
 794       operator=(const __enable_shared_from_this&)
 795       { return *this; }
 796
 797       ~__enable_shared_from_this() { }
 798
 799     public:
 800       __shared_ptr<_Tp, _Lp>
 801       shared_from_this()
 802       { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
 803
 804       __shared_ptr<const _Tp, _Lp>
 805       shared_from_this() const
 806       { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
 807
 808     private:
 809       template<typename _Tp1>
 810         void
 811         _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const
 812         { _M_weak_this._M_assign(__p, __n); }
 813
 814       template<typename _Tp1>
 815         friend void
 816         __enable_shared_from_this_helper(const __shared_count<_Lp>& __pn,
 817                                          const __enable_shared_from_this* __pe,
 818                                          const _Tp1* __px)
 819         {
 820           if (__pe != 0)
 821             __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
 822         }
 823
 824       mutable __weak_ptr<_Tp, _Lp>  _M_weak_this;
 825     };
 826
 827
 828   /// shared_ptr
 829   // The actual shared_ptr, with forwarding constructors and
 830   // assignment operators.
 831   template<typename _Tp>
 832     class shared_ptr
 833     : public __shared_ptr<_Tp>
 834     {
 835     public:
 836       shared_ptr()
 837       : __shared_ptr<_Tp>() { }
 838
 839       template<typename _Tp1>
 840         explicit
 841         shared_ptr(_Tp1* __p)
 842         : __shared_ptr<_Tp>(__p) { }
 843
 844       template<typename _Tp1, typename _Deleter>
 845         shared_ptr(_Tp1* __p, _Deleter __d)
 846         : __shared_ptr<_Tp>(__p, __d) { }
 847
 848       template<typename _Tp1>
 849         shared_ptr(const shared_ptr<_Tp1>& __r)
 850         : __shared_ptr<_Tp>(__r) { }
 851
 852       template<typename _Tp1>
 853         explicit
 854         shared_ptr(const weak_ptr<_Tp1>& __r)
 855         : __shared_ptr<_Tp>(__r) { }
 856
 857 #if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_DEPRECATED
 858       template<typename _Tp1>
 859         explicit
 860         shared_ptr(std::auto_ptr<_Tp1>& __r)
 861         : __shared_ptr<_Tp>(__r) { }
 862 #endif
 863
 864       template<typename _Tp1>
 865         shared_ptr(const shared_ptr<_Tp1>& __r, __static_cast_tag)
 866         : __shared_ptr<_Tp>(__r, __static_cast_tag()) { }
 867
 868       template<typename _Tp1>
 869         shared_ptr(const shared_ptr<_Tp1>& __r, __const_cast_tag)
 870         : __shared_ptr<_Tp>(__r, __const_cast_tag()) { }
 871
 872       template<typename _Tp1>
 873         shared_ptr(const shared_ptr<_Tp1>& __r, __dynamic_cast_tag)
 874         : __shared_ptr<_Tp>(__r, __dynamic_cast_tag()) { }
 875
 876       template<typename _Tp1>
 877         shared_ptr&
 878         operator=(const shared_ptr<_Tp1>& __r) // never throws
 879         {
 880           this->__shared_ptr<_Tp>::operator=(__r);
 881           return *this;
 882         }
 883
 884 #if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_DEPRECATED
 885       template<typename _Tp1>
 886         shared_ptr&
 887         operator=(std::auto_ptr<_Tp1>& __r)
 888         {
 889           this->__shared_ptr<_Tp>::operator=(__r);
 890           return *this;
 891         }
 892 #endif
 893     };
 894
 895   // 2.2.3.8 shared_ptr specialized algorithms.
 896   template<typename _Tp>
 897     inline void
 898     swap(__shared_ptr<_Tp>& __a, __shared_ptr<_Tp>& __b)
 899     { __a.swap(__b); }
 900
 901   template<typename _Tp, typename _Tp1>
 902     inline shared_ptr<_Tp>
 903     static_pointer_cast(const shared_ptr<_Tp1>& __r)
 904     { return shared_ptr<_Tp>(__r, __static_cast_tag()); }
 905
 906   template<typename _Tp, typename _Tp1>
 907     inline shared_ptr<_Tp>
 908     const_pointer_cast(const shared_ptr<_Tp1>& __r)
 909     { return shared_ptr<_Tp>(__r, __const_cast_tag()); }
 910
 911   template<typename _Tp, typename _Tp1>
 912     inline shared_ptr<_Tp>
 913     dynamic_pointer_cast(const shared_ptr<_Tp1>& __r)
 914     { return shared_ptr<_Tp>(__r, __dynamic_cast_tag()); }
 915
 916
 917   /// weak_ptr
 918   // The actual weak_ptr, with forwarding constructors and
 919   // assignment operators.
 920   template<typename _Tp>
 921     class weak_ptr
 922     : public __weak_ptr<_Tp>
 923     {
 924     public:
 925       weak_ptr()
 926       : __weak_ptr<_Tp>() { }
 927
 928       template<typename _Tp1>
 929         weak_ptr(const weak_ptr<_Tp1>& __r)
 930         : __weak_ptr<_Tp>(__r) { }
 931
 932       template<typename _Tp1>
 933         weak_ptr(const shared_ptr<_Tp1>& __r)
 934         : __weak_ptr<_Tp>(__r) { }
 935
 936       template<typename _Tp1>
 937         weak_ptr&
 938         operator=(const weak_ptr<_Tp1>& __r) // never throws
 939         {
 940           this->__weak_ptr<_Tp>::operator=(__r);
 941           return *this;
 942         }
 943
 944       template<typename _Tp1>
 945         weak_ptr&
 946         operator=(const shared_ptr<_Tp1>& __r) // never throws
 947         {
 948           this->__weak_ptr<_Tp>::operator=(__r);
 949           return *this;
 950         }
 951
 952       shared_ptr<_Tp>
 953       lock() const // never throws
 954       {
 955 #ifdef __GTHREADS
 956         if (this->expired())
 957           return shared_ptr<_Tp>();
 958
 959         __try
 960           {
 961             return shared_ptr<_Tp>(*this);
 962           }
 963         __catch(const bad_weak_ptr&)
 964           {
 965             return shared_ptr<_Tp>();
 966           }
 967 #else
 968         return this->expired() ? shared_ptr<_Tp>()
 969                                : shared_ptr<_Tp>(*this);
 970 #endif
 971       }
 972     };
 973
 974   /// enable_shared_from_this
 975   template<typename _Tp>
 976     class enable_shared_from_this
 977     {
 978     protected:
 979       enable_shared_from_this() { }
 980
 981       enable_shared_from_this(const enable_shared_from_this&) { }
 982
 983       enable_shared_from_this&
 984       operator=(const enable_shared_from_this&)
 985       { return *this; }
 986
 987       ~enable_shared_from_this() { }
 988
 989     public:
 990       shared_ptr<_Tp>
 991       shared_from_this()
 992       { return shared_ptr<_Tp>(this->_M_weak_this); }
 993
 994       shared_ptr<const _Tp>
 995       shared_from_this() const
 996       { return shared_ptr<const _Tp>(this->_M_weak_this); }
 997
 998     private:
 999       template<typename _Tp1>
1000         void
1001         _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const
1002         { _M_weak_this._M_assign(__p, __n); }
1003
1004       template<typename _Tp1>
1005         friend void
1006         __enable_shared_from_this_helper(const __shared_count<>& __pn,
1007                                          const enable_shared_from_this* __pe,
1008                                          const _Tp1* __px)
1009         {
1010           if (__pe != 0)
1011             __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
1012         }
1013
1014       mutable weak_ptr<_Tp>  _M_weak_this;
1015     };
1016
1017 }
1018 }
1019
1020 #endif // _TR1_SHARED_PTR_H