Line data    Source code

       1             : // auto_ptr implementation -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2007-2019 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             : /** @file backward/auto_ptr.h
      26             :  *  This is an internal header file, included by other library headers.
      27             :  *  Do not attempt to use it directly. @headername{memory}
      28             :  */
      29             : 
      30             : #ifndef _BACKWARD_AUTO_PTR_H
      31             : #define _BACKWARD_AUTO_PTR_H 1
      32             : 
      33             : #include <bits/c++config.h>
      34             : #include <debug/debug.h>
      35             : 
      36             : namespace std _GLIBCXX_VISIBILITY(default)
      37             : {
      38             : _GLIBCXX_BEGIN_NAMESPACE_VERSION
      39             : 
      40             :   /**
      41             :    *  A wrapper class to provide auto_ptr with reference semantics.
      42             :    *  For example, an auto_ptr can be assigned (or constructed from)
      43             :    *  the result of a function which returns an auto_ptr by value.
      44             :    *
      45             :    *  All the auto_ptr_ref stuff should happen behind the scenes.
      46             :    */
      47             :   template<typename _Tp1>
      48             :     struct auto_ptr_ref
      49             :     {
      50             :       _Tp1* _M_ptr;
      51             :       
      52             :       explicit
      53             :       auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
      54             :     } _GLIBCXX_DEPRECATED;
      55             : 
      56             : #pragma GCC diagnostic push
      57             : #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
      58             : 
      59             :   /**
      60             :    *  @brief  A simple smart pointer providing strict ownership semantics.
      61             :    *
      62             :    *  The Standard says:
      63             :    *  <pre>
      64             :    *  An @c auto_ptr owns the object it holds a pointer to.  Copying
      65             :    *  an @c auto_ptr copies the pointer and transfers ownership to the
      66             :    *  destination.  If more than one @c auto_ptr owns the same object
      67             :    *  at the same time the behavior of the program is undefined.
      68             :    *
      69             :    *  The uses of @c auto_ptr include providing temporary
      70             :    *  exception-safety for dynamically allocated memory, passing
      71             :    *  ownership of dynamically allocated memory to a function, and
      72             :    *  returning dynamically allocated memory from a function.  @c
      73             :    *  auto_ptr does not meet the CopyConstructible and Assignable
      74             :    *  requirements for Standard Library <a
      75             :    *  href="tables.html#65">container</a> elements and thus
      76             :    *  instantiating a Standard Library container with an @c auto_ptr
      77             :    *  results in undefined behavior.
      78             :    *  </pre>
      79             :    *  Quoted from [20.4.5]/3.
      80             :    *
      81             :    *  Good examples of what can and cannot be done with auto_ptr can
      82             :    *  be found in the libstdc++ testsuite.
      83             :    *
      84             :    *  _GLIBCXX_RESOLVE_LIB_DEFECTS
      85             :    *  127.  auto_ptr<> conversion issues
      86             :    *  These resolutions have all been incorporated.
      87             :    */
      88             :   template<typename _Tp>
      89             :     class auto_ptr
      90             :     {
      91             :     private:
      92             :       _Tp* _M_ptr;
      93             :       
      94             :     public:
      95             :       /// The pointed-to type.
      96             :       typedef _Tp element_type;
      97             :       
      98             :       /**
      99             :        *  @brief  An %auto_ptr is usually constructed from a raw pointer.
     100             :        *  @param  __p  A pointer (defaults to NULL).
     101             :        *
     102             :        *  This object now @e owns the object pointed to by @a __p.
     103             :        */
     104             :       explicit
     105           0 :       auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
     106             : 
     107             :       /**
     108             :        *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
     109             :        *  @param  __a  Another %auto_ptr of the same type.
     110             :        *
     111             :        *  This object now @e owns the object previously owned by @a __a,
     112             :        *  which has given up ownership.
     113             :        */
     114             :       auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
     115             : 
     116             :       /**
     117             :        *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
     118             :        *  @param  __a  Another %auto_ptr of a different but related type.
     119             :        *
     120             :        *  A pointer-to-Tp1 must be convertible to a
     121             :        *  pointer-to-Tp/element_type.
     122             :        *
     123             :        *  This object now @e owns the object previously owned by @a __a,
     124             :        *  which has given up ownership.
     125             :        */
     126             :       template<typename _Tp1>
     127             :         auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
     128             : 
     129             :       /**
     130             :        *  @brief  %auto_ptr assignment operator.
     131             :        *  @param  __a  Another %auto_ptr of the same type.
     132             :        *
     133             :        *  This object now @e owns the object previously owned by @a __a,
     134             :        *  which has given up ownership.  The object that this one @e
     135             :        *  used to own and track has been deleted.
     136             :        */
     137             :       auto_ptr&
     138             :       operator=(auto_ptr& __a) throw()
     139             :       {
     140             :         reset(__a.release());
     141             :         return *this;
     142             :       }
     143             : 
     144             :       /**
     145             :        *  @brief  %auto_ptr assignment operator.
     146             :        *  @param  __a  Another %auto_ptr of a different but related type.
     147             :        *
     148             :        *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
     149             :        *
     150             :        *  This object now @e owns the object previously owned by @a __a,
     151             :        *  which has given up ownership.  The object that this one @e
     152             :        *  used to own and track has been deleted.
     153             :        */
     154             :       template<typename _Tp1>
     155             :         auto_ptr&
     156             :         operator=(auto_ptr<_Tp1>& __a) throw()
     157             :         {
     158             :           reset(__a.release());
     159             :           return *this;
     160             :         }
     161             : 
     162             :       /**
     163             :        *  When the %auto_ptr goes out of scope, the object it owns is
     164             :        *  deleted.  If it no longer owns anything (i.e., @c get() is
     165             :        *  @c NULL), then this has no effect.
     166             :        *
     167             :        *  The C++ standard says there is supposed to be an empty throw
     168             :        *  specification here, but omitting it is standard conforming.  Its
     169             :        *  presence can be detected only if _Tp::~_Tp() throws, but this is
     170             :        *  prohibited.  [17.4.3.6]/2
     171             :        */
     172           0 :       ~auto_ptr() { delete _M_ptr; }
     173             :       
     174             :       /**
     175             :        *  @brief  Smart pointer dereferencing.
     176             :        *
     177             :        *  If this %auto_ptr no longer owns anything, then this
     178             :        *  operation will crash.  (For a smart pointer, <em>no longer owns
     179             :        *  anything</em> is the same as being a null pointer, and you know
     180             :        *  what happens when you dereference one of those...)
     181             :        */
     182             :       element_type&
     183           0 :       operator*() const throw() 
     184             :       {
     185             :         __glibcxx_assert(_M_ptr != 0);
     186             :         return *_M_ptr; 
     187             :       }
     188             :       
     189             :       /**
     190             :        *  @brief  Smart pointer dereferencing.
     191             :        *
     192             :        *  This returns the pointer itself, which the language then will
     193             :        *  automatically cause to be dereferenced.
     194             :        */
     195             :       element_type*
     196             :       operator->() const throw() 
     197             :       {
     198             :         __glibcxx_assert(_M_ptr != 0);
     199             :         return _M_ptr; 
     200             :       }
     201             :       
     202             :       /**
     203             :        *  @brief  Bypassing the smart pointer.
     204             :        *  @return  The raw pointer being managed.
     205             :        *
     206             :        *  You can get a copy of the pointer that this object owns, for
     207             :        *  situations such as passing to a function which only accepts
     208             :        *  a raw pointer.
     209             :        *
     210             :        *  @note  This %auto_ptr still owns the memory.
     211             :        */
     212             :       element_type*
     213             :       get() const throw() { return _M_ptr; }
     214             :       
     215             :       /**
     216             :        *  @brief  Bypassing the smart pointer.
     217             :        *  @return  The raw pointer being managed.
     218             :        *
     219             :        *  You can get a copy of the pointer that this object owns, for
     220             :        *  situations such as passing to a function which only accepts
     221             :        *  a raw pointer.
     222             :        *
     223             :        *  @note  This %auto_ptr no longer owns the memory.  When this object
     224             :        *  goes out of scope, nothing will happen.
     225             :        */
     226             :       element_type*
     227             :       release() throw()
     228             :       {
     229             :         element_type* __tmp = _M_ptr;
     230             :         _M_ptr = 0;
     231             :         return __tmp;
     232             :       }
     233             :       
     234             :       /**
     235             :        *  @brief  Forcibly deletes the managed object.
     236             :        *  @param  __p  A pointer (defaults to NULL).
     237             :        *
     238             :        *  This object now @e owns the object pointed to by @a __p.  The
     239             :        *  previous object has been deleted.
     240             :        */
     241             :       void
     242             :       reset(element_type* __p = 0) throw()
     243             :       {
     244             :         if (__p != _M_ptr)
     245             :           {
     246             :             delete _M_ptr;
     247             :             _M_ptr = __p;
     248             :           }
     249             :       }
     250             :       
     251             :       /** 
     252             :        *  @brief  Automatic conversions
     253             :        *
     254             :        *  These operations are supposed to convert an %auto_ptr into and from
     255             :        *  an auto_ptr_ref automatically as needed.  This would allow
     256             :        *  constructs such as
     257             :        *  @code
     258             :        *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
     259             :        *    ...
     260             :        *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
     261             :        *  @endcode
     262             :        *
     263             :        *  But it doesn't work, and won't be fixed. For further details see
     264             :        *  http://cplusplus.github.io/LWG/lwg-closed.html#463
     265             :        */
     266             :       auto_ptr(auto_ptr_ref<element_type> __ref) throw()
     267             :       : _M_ptr(__ref._M_ptr) { }
     268             :       
     269             :       auto_ptr&
     270             :       operator=(auto_ptr_ref<element_type> __ref) throw()
     271             :       {
     272             :         if (__ref._M_ptr != this->get())
     273             :           {
     274             :             delete _M_ptr;
     275             :             _M_ptr = __ref._M_ptr;
     276             :           }
     277             :         return *this;
     278             :       }
     279             :       
     280             :       template<typename _Tp1>
     281             :         operator auto_ptr_ref<_Tp1>() throw()
     282             :         { return auto_ptr_ref<_Tp1>(this->release()); }
     283             : 
     284             :       template<typename _Tp1>
     285             :         operator auto_ptr<_Tp1>() throw()
     286             :         { return auto_ptr<_Tp1>(this->release()); }
     287             :     } _GLIBCXX_DEPRECATED;
     288             : 
     289             :   // _GLIBCXX_RESOLVE_LIB_DEFECTS
     290             :   // 541. shared_ptr template assignment and void
     291             :   template<>
     292             :     class auto_ptr<void>
     293             :     {
     294             :     public:
     295             :       typedef void element_type;
     296             :     } _GLIBCXX_DEPRECATED;
     297             : 
     298             : #if __cplusplus >= 201103L
     299             :   template<_Lock_policy _Lp>
     300             :   template<typename _Tp>
     301             :     inline
     302             :     __shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r)
     303             :     : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get()))
     304             :     { __r.release(); }
     305             : 
     306             :   template<typename _Tp, _Lock_policy _Lp>
     307             :   template<typename _Tp1, typename>
     308             :     inline
     309             :     __shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r)
     310             :     : _M_ptr(__r.get()), _M_refcount()
     311             :     {
     312             :       __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
     313             :       static_assert( sizeof(_Tp1) > 0, "incomplete type" );
     314             :       _Tp1* __tmp = __r.get();
     315             :       _M_refcount = __shared_count<_Lp>(std::move(__r));
     316             :       _M_enable_shared_from_this_with(__tmp);
     317             :     }
     318             : 
     319             :   template<typename _Tp>
     320             :   template<typename _Tp1, typename>
     321             :     inline
     322             :     shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r)
     323             :     : __shared_ptr<_Tp>(std::move(__r)) { }
     324             : 
     325             :   template<typename _Tp, typename _Dp>
     326             :   template<typename _Up, typename>
     327             :     inline
     328             :     unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept
     329             :     : _M_t(__u.release(), deleter_type()) { }
     330             : #endif
     331             : 
     332             : #pragma GCC diagnostic pop
     333             : 
     334             : _GLIBCXX_END_NAMESPACE_VERSION
     335             : } // namespace
     336             : 
     337             : #endif /* _BACKWARD_AUTO_PTR_H */